Introducing a Back Filter: The Impact of Metal Type on Reducing Particulate Matter and Sulfide Emissions from Diesel Engine Exhaust

Introducing a Back Filter: The Impact of Metal Type on Reducing Particulate Matter and Sulfide Emissions from Diesel Engine Exhaust | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Introducing a Back Filter: The Impact of Metal Type on Reducing Particulate Matter and Sulfide Emissions from Diesel Engine Exhaust Zohreh Haghighi Kafash, Mohammad Reza Mahmoudian This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6526930/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 10 Sep, 2025 Read the published version in Environmental Science and Pollution Research → Version 1 posted 5 You are reading this latest preprint version Abstract This study introduces a back filter installed at the end of the exhaust pipes of city buses, examining how the type of metal used in its construction affects the absorption of suspended particles and the reduction of sulfides in diesel engine exhaust gases. The back filter is constructed from three metals: copper, zinc, and nickel. The nickel sample was prepared by electroplated of nickel on the 316 steel surfaces (316SNi), while hot-dip galvanized steel was used as a substitute for zinc (SZinc). Poly tetrafluoroethylene (PTFE) powder was utilized to enhance soot adsorption, sandwiched between two metal plates in each back filter. The results indicated that the amount of soot deposited on the 316SNi filter was approximately five and three times greater than that on the filters made of copper and SZinc in the absence and presence of PTFE powder. Additionally, the sulfide absorption on the 316SNi filter was ten times higher than on the other two types. To interpret these results, impedance spectroscopy was employed to assess the electrical resistance of the absorbed soot, and X-ray diffraction was utilized to identify the mineral compounds formed on the filter's surface. The significant differences observed can be attributed to the lower thermal conductivity of 316SNi compared to the other metals, the reduced electrical resistance of soot adsorbed on 316SNi, and the formation of nickel sulfide as a kinetic product on its surface. Soot Deposition Air pollution Back filter Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 1 Introduction Nowadays, one of the global concerns that have received more attention is the issue of air pollution and climate change (Miller et al., 2024 ). Industrialization is accelerating and causing many negative consequences for both humanity and the environment (Ramakrishna & Jose, 2021 ). In the majority of instances, making amends for inflicted damage is irreversible. In recent years, in the metropolitan areas, the escalating consumption of fossil fuels by internal combustion engine has imposed significant costs on the entire economy, and air pollution has become a hazardous event (Carranza et al., 2022 ; Kumar & Choudhary, 2023 ; Verma et al., 2021 ). Studies have shown that, compared to other pollutants, particles with diameters between PM2.5 and PM10 have more severe effects on the health of certain groups such as children, the elderly, and those with underlying diseases. In addition, its effects on plants have been fully confirmed (Stanek & Brown, 2019 ; Zhou et al., 2022 ; Guo et al., 2024 ; Wang et al., 2020 ). Diesel engines are popular due to their advantages such as, robustness, reliability, and easy maintenance. In addition, due to their high energy density, it enables them to produce more power per unit of fuel, making them efficient and cost-effective engines (Saravanamuthu et al., 2023 ). Unfortunately, diesel engines are one of the important sources of air pollution in the production of carbon-based suspended particles in the form of soot (black carbon) (Wei & Wang, 2021 ). The incomplete combustion of hydrocarbons such as fossil fuels, biofuels, and biomass causes a substantial increase in soot emissions and accumulation in the environment. Soot is a kind of amorphous carbonaceous nanomaterial that has a high percentage of macropores, low ash content, and volatiles. Every year, nearly 8 million metric tons (MMTs) of soot are released into the environment (Philomina et al., 2022 ; Chylek et al., 2023 ; Uttaravalli et al., 2022 ). Exposure to soot has numerous harmful effects on human health. Short-term exposure to soot may cause exacerbated cardiovascular and respiratory symptoms, reduce visibility, and cause nose and eye irritation, and therefore, increase medical needs and hospitalizations. Long-term exposure to soot may lead to premature death, asthma, bronchitis, lung cancer, stroke, and heart attack. The fundamental key to a pollution-free world is understanding the harmful effects of these contaminants and identifying effective ways to control them (Seaton et al., 1995 ; Sydbom et al., 2001 ; Sahu et al., 2016 ; Nelin et al., 2012 ; Ristovski et al., 2012 ; Watanabe and Oonuki, 1999 ; Su et al., 1989 ; Gopal et al., 2021 ). Through proper treatment, collected and recycled carbon black can be used for a wide range of products. Recent research has shown that diesel soot nanoparticles can be used as feedstock to produce high performance activated carbon with high carbon dioxide adsorption. The activated carbons produced have shown a high CO 2 uptake capacity, favorable adsorption kinetics, and high CO 2 /N 2 selectivity after combined oxidative treatment (Guerrero Peña et al., 2023 ). Uttaravalli et al. ( 2022 ) emphasized the environmental advantages of recycling soot to mitigate emissions from hydrocarbon fuel combustion. They noted that incorporating recycled soot can enhance the mechanical, thermal, and electrical properties of products and serve as an effective adsorbent for pollutants, thus offering a sustainable alternative to the current carbon. This study focused on the sustainable use of recycled soot (carbon black) from diesel engine exhaust, emphasizing its potential applications in composite materials, energy storage devices, and the removal of various contaminants in the treatment of air and water. On the other hand, Lough et al. ( 2005 ) found that 19% of particulate matters (PM10) were consisted of metals such as Si, Fe, Ca, Na, Mg, Al, and K. Recent reports have shown that metals such as zinc, nickel, and copper have catalytic properties on gases produced by burning various fossil fuels. Prikhod’ko et al. ( 2014 ) reported the effect of copper and nickel substrates in the flame zone of premixed propane-oxygen and found nickel substrates to be more efficient for graphene growth. So far, various methods have been introduced to absorb soot or minimize it in the process of fossil fuel combustion (Shukla et al., 2024 ). Many of these methods are focused on engine efficiency, fuel type (Zhang et al., 2018 ), the use of different catalysts (Caliskan & Mori, 2017 ) in the exhaust pipe tank, and the use of different filters (Al-Wakeel et al., 2012 ), but the main priority of soot collection to reduce the resulting pollution should be considered (Uttaravalli et al., 2022 ). In line with this goal, simple installation of the filter, easy removal of soot accumulated in the filter, prevention of negative impact on engine performance, and most importantly, low price and the possibility of using it multiple times should be considered (Luo et al., 2023 ). On the other hand, creating incentives for financial managers to install and remove accumulated waste is one of the things that affect its social efficiency (Ling et al., 2021 ; Manni & Runhaar, 2014 ). Therefore, implementing any type of project, such as fabricating a simple device, making changes in fuel, improving engine performance, improving engine alloys, and improving engine oil, not only impacts the health and quality of life of organisms but also serves as an interesting topic for research. This study introduces a back filter installed at the end of the exhaust pipe of city buses and investigates the impact of the metal type used in its construction on the absorption of suspended particles and the reduction of sulfides in diesel engine exhaust gases. The back filter is constructed from three different metals: copper, zinc, and nickel, each used separately. Due to the high cost of pure nickel, nickel was electroplated onto stainless steel 316 (316SNi), while hot-dip galvanized steel sheet was utilized as a substitute for zinc (SZinc). 2 Experimental methods 2.1 Methodology and strategy The research methodology and strategy were structured around specific steps and questions that needed to be addressed: 1-Designing and Installing a Back Filter: The back filter was designed and installed at the end of the exhaust system of city buses, where engineers had not previously implemented any solutions. This placement allows for the absorption of pollutants before exhaust gases are released into the atmosphere, making any captured pollution beneficial. 2-Characteristics of the Manufactured Back Filter: The back filter was required to meet several key characteristics: a) cost-effectiveness, b) sulfur absorption capability, c) reusability, d) quick and easy installation, and e) no negative impact on bus engine performance Based on these features, a back filter was designed and three types of metals, copper, zinc, and nickel, were considered for its manufacture. In order for the back filter to be economical Nickel metal was electroplated on 316 Stain less steel (316SNi) and hot-dip galvanized steel sheet was used to replace zinc (SZinc). Other researchers have reported the effectiveness of nickel and its alloys as a suitable catalyst, but because the fabrication of the back filter using this type of metal is very expensive and on the other hand, alloys with a high percentage of nickel such as Raney nickel are very rare in Iran, we decided to electroplate Ni on the surface of 316 Stainless steel. Poly (tetrafluoroethylene) (PTFE) powder (1 Micron, Nano Bonyan Asia, Tehran, Iran) was utilized to enhance soot adsorption, sandwiched between two metal plates in each back filter. The charge created by the vibration of PTFE powder, which is usually a triboelectric charge, can help attract soot onto the filter backing. A city bus from Tehran Municipality was selected, using EURO 3 fuel, with the specifications listed in Table 1 . The engine specifications of the bus are listed in Table 2 . After each test, a technical inspection of the engine was performed to ensure that all conditions were the same for all tests. Table 1 General specifications of the EURO 3 fuel Parameter Specification Sulfur Content Max 350 ppm (parts per million) for diesel; Max 150 ppm for gasoline Aromatic Hydrocarbons Max 35% by volume Olefins (Gasoline) Max 18% by volume Benzene Content Max 1% by volume Cetane Number (Diesel) Min 51 Distillation (Gasoline) − 90% of the fuel must evaporate at 210°C Volatility (Gasoline) Must comply with Reid Vapor Pressure (RVP) standards for summer and winter Density (Diesel) 820–845 kg/m³ at 15°C Lead Content (Gasoline) Lead-free (Max 0.005 g/L) Oxygen Content (Gasoline) Max 2.7% by weight Polycyclic Aromatics (Diesel) Max 11% by weight Additives Use of specific additives is permitted to improve combustion and engine performance Particulate Matter (PM) Reduction compared to previous standards Table 2 The specifications of the subject bus (Volvo B9R) Category Specifications Chassis Volvo B9R, EURO 3 -compliant chassis with R9700 body and double-glazed adhesive windows. Engine - Model: D9B 380, inline, 6-cylinder, 4-stroke. - Power: 380 hp at 1900 rpm. - Torque: 1740 Nm at 1200–1400 rpm. - Displacement: 9.4 liters. - Features: Turbocharger, intercooler, electronic fuel control (EMS2), EURO 3 & EURO 4 emission standards. Gearbox - Model: I-Shift V2412AT. - Type: Fully automatic, 12-speed forward, 4 reverse gears. - Manual mode option with gear locking. - Fuel-saving software. - Hydraulic retarder: VR3250 with braking power of 400–600 kW, integrated with EBS. Suspension & Axles - Front axle: Standard camber, electronic suspension. - Rear axle: Volvo RS 1228B with 4 air springs, ratio 2.85:1. - Hydraulic telescopic dampers. Steering - Adjustable hydraulic steering with a 450 mm diameter steering wheel. - Max turning angle: 50°. Braking System - Disc brakes on both axles, dual-circuit air brakes. - Features: ABS, EBD, EBS, ASR, TCS. - Automatic lining adjustment, asbestos-free linings. - Integrated retarder and brake cooling system. Electrical System - Voltage: 24V. - Batteries: 2 x 225 Ah. - Alternators: 2 x 110 Ah. - Emergency battery cut-off system. Tires - Configuration: Tubeless tires. - Sizes: 295/80R22.5 & 315/80R22.5. - Steel rims. Dimensions - Length: 12,500 mm. - Width: 2,550 mm. - Height: 3,700 mm. - Wheelbase: 6,300 mm. - Cabin height: 1,950 mm. Weights - Maximum weight with passengers and cargo: 19,000 kg. - Front axle load limit: 7,500 kg. - Rear axle load limit: 12,000 kg. Passenger Capacity - Standard: 47 + 1 + 1. - Classic: 44 + 1 + 1. - VIP: 25 + 1 + 1. Fuel Tank - Capacity: 600 liters. - Dual-side fueling capability near the front axle. Safety Features - FUPS (Front Underrun Protection System). - FIP (Frontal Impact Protection). - KIP (Driver Knee Impact Protection). Comfort Features - Passenger: Adjustable reclining seats, air conditioning, individual sound systems, 2 LCD screens, 1 VCD player. - Double-glazed, adhesive-secured windows. - Cabin: Fridge, water cooler, coffee maker, electric blinds, sleeping cabin with mattress and pillows, contact intercom. - Lighting: LED-based ambient lighting and reading lights. Emission Standard EURO 3 Additional Features - Satellite navigation (GPS). - Emergency equipment: Fire extinguishers (2), emergency hammers (4). - Air-tight baggage doors with warning systems. - Advanced lighting: Digital front display, rearview cameras, and warning systems for gearbox brakes and motor compartments. 2.2 Apparatus and Characterizations The constituents, morphology, and chemical properties of soot-deposited on half-sheets were investigated by; energy dispersive X-ray (EDX) spectroscopy, field emission scanning electron microscopy (FESEM, Quanta 200F), and FTIR spectroscopy (Spectrum 400 (FT-IR/FT-FIR spectrometer) were used. The phase of each sample was studied by X-ray diffraction (Siemens D5000) with Cu Kα radiation. The electrochemical properties of the materials deposited on the half-plates were studied using impedance spectroscopy (EIS). All the electrochemical experiments were performed using a PalmSens potentiostat/galvanostat. General-purpose software (PSTrace 5.10.5604) and a frequency response analyzer (Eissa1), installed on a computer and interfaced with the potentiostat, were used to conduct the experiments and analyze the data. Electrochemical impedance spectroscopy (EIS) measurements were performed in a 3.5% w/w NaCl solution. The impedance spectra for the determination of the charge transfer resistance of the soot-deposited Cu/GCE, soot-deposited SZinc/GCE, and soot-deposited soot-deposited 316SNi /GCE were obtained over a frequency range of 100 kHz–0.1 Hz, with an acquisition of 10 points per decade. A saturated Ag/AgCl electrode and a platinum foil served as the reference and counter electrodes, respectively. 2.3 Electrode preparation One milligram (1 mg) of soot-deposited on half-plates in a device made of copper, hot-dip galvanized steel sheet (SZinc), and 316 stainless steel (316SNi) (referred to as soot-deposited Cu, soot-deposited SZinc, and soot-deposited 316SNi) was dispersed in 1 mL of deionized (DI) water using ultrasonication for 30 minutes to produce a dark brown homogeneous suspension. Then, 10 µL of the homogeneous suspension was drop-cast onto the surface of a polished glassy carbon electrode (GCE) and dried at room temperature. Next, 3 µL of Nafion 117 (1% m/v) was drop-cast onto the surface of the soot-deposited Cu/GCE, soot-deposited SZinc/GCE, and soot-deposited 316SNi/GCE to enhance the stability of the electrode. 2.4 Electroplating of Ni on the surface of 316Stainless steel To electroplate nickel onto the surface of a stainless steel 316 back filter, we followed the method reported by Gay et al. (1987). The process involved the following steps: First, the plates were cleaned by immersing them in an electrolytic bath containing 10% V/V sulfuric acid while connected to the anode of a DC power source. The second step involved rinsing the plates to remove any residual sulfuric acid. The third step was nickel plating, achieved by immersing the plates in a nickel electrolytic solution composed of nickel chloride and hydrochloric acid, with the voltage adjusted according to the surface area of each plate. Figure 1 presents the FESEM (a) and EDX (b) results of the stainless steel 316 plates after nickel electroplating. It is important to note that nanotechnology methods were not employed to enhance the surface area of the deposited nickel for two reasons: 1) Cleaning the plates and removing soot from the surface would have been challenging and would require washing methods that could lead to environmental pollution, which end users would likely be reluctant to undertake; and 2) Production costs would have increased. 3 Results and discussion 3.1 Device installation and amount of soot deposited Figure 2 shows the structure of the back filter, which is made of pure copper (99%), SZinc, and 316SNi, with the properties specified in Table 3 . Each plate consisted of two parallel metal layers separated by a distance of 2 mm, creating a chamber for PTFE powder. A total of 3 g, 5 g, and 7 g of PTFE powder were added to plates with radii of 1.5 cm, 2.5 cm, and 4.5 cm, respectively. The angles of the half-plates with respect to the central rod were considered to be 30°, 45°, and 90°. The direction of the half-plates was aligned with that of the exhaust gases. All the half-plates were sandblasted to achieve a near-white surface profile as per Swedish specification SA 2.5 (Venison, 1973 ), then washed with methanol to remove oil stains, and finally installed at the end of the exhaust pipe. First, three SZinc back filters were made with angles 30°, 45°, and 90° relative to the vertical axis of the device respectively, and each was installed on the bus exhaust. The results of the amount of soot deposited on the devices at different angles, along with the opinions of engineers and drivers on engine performance after installing the back filter, led to the selection of 45°. The 30° angle was not considered due to the small amount of soot deposited on the plates, and the 90° angle was not considered due to the obstruction of exhaust gas passage (Fig. 3 (a and b)). It is important to note that the back filter is installed at the end of the exhaust pipe in such a way that a plate with a smaller diameter initially encounters the exhaust gases. This prevents the small half-plate from being masked by the exhaust gases if the back filter is installed in the opposite direction. Selecting three half-plates with different diameters also reduces the possibility of a negative effect on exhaust performance for the exhaust gases resulting from engine combustion. Table 4 (a) and (b) shows the ppm value of soot deposited on the back filter made of copper, SZinc, and 316SNi in absence and presence of PTFE powder. It is well know that the type of charge created by the vibration of PTFE powder is typically a triboelectric charge. This occurs due to the triboelectric effect, where materials become electrically charged after coming into contact with each other and then separating. In the case of PTFE, its properties allow it to gain or lose electrons when subjected to mechanical vibrations, leading to the generation of static electricity. PTFE is known to gain a negative charge when it comes into contact with metals like steel, which tends to lose electrons and thus acquire a positive charge. As mentioned in the experimental section, the ppm of soot deposited on the filters after installation on a bus with specific fuel consumption and specifications was determined after traveling a distance of 1813 km. It should be noted that not only was this distance the same for all three filters, but the route traveled was also considered identical. Before installing each of these filters, a technical inspection of the bus was carried out to ensure that no changes were made to the test conditions. As shown in Table 4 , the ppm value of soot deposited on 316SNi is approximately 5 and 3 times higher than that of the soot deposited on a back filter made of copper and SZinc in the absence and presence of PTFE respectively. Since the use of PTFE has been shown to absorb more soot, it has been shown that soot particles become negatively charged as they pass through the exhaust pipe and are neutralized and absorbed when they come into contact with the back filter plates, which are positively charged due to the presence of PTFE. Table 3 The type of Alloy and metal Type of device/wt% →All data is based on EDX Results Hot-dip galvanized steel sheet O 6.12 Al 0.30 S 0.22 Ca 0.21 Fe 7.78 Zn 85.37 copper O 4.94 Cu 95.06 316 stainless steel (before electroplating) C 7.61 O 4.66 Na 0.25 Si 0.56 P 0.04 S 0.04 Ca 0.24 Cr 17.07 Mn 1.26 Fe 60.99 Ni 6.50 Table 4 PPM value of soot-depositedon the filter back made of Copper, Szinc and 316SNi, in the absence (a) and presence of PTFE (b). Type of material used in the back filter Copper SZinc 316SNi ppm value (In the absent of PTFE) 52400 67900 318500 ppm value (In the presence of PTFE) 75100 77200 223600 3.2 FESEM results Figure 4 shows the FESEM results of the soot deposited on a device made of copper (soot- deposited Cu), SZinc (soot-deposited SZinc) and 316SNi (soot-deposited316SNi). The histogram shows that the average size of the soot deposited on copper and SZinc is approximately 26 nm and 27 nm, respectively, while the size of the soot deposited on 316SNi is much larger, more compact, and in the microscale range. According to the FESEM results, the porosity of the soot deposited on Cu and SZinc is much higher compared to that of the soot deposited on 316SNi, and these results are further confirmed by the impedance spectroscopy results presented in the next section. 3.3 XRD and EDX results Figure 5 shows the XRD results for soot deposited on Cu (a), soot deposited on SZinc (b), and soot deposited on 316SNi (c). The XRD pattern for the soot deposited on Cu (a) shows peaks corresponding to (00-002-1195, copper sulfate hydrate (antlerite)) and (00-003-0892, Cu 2 O (cuprite)). The XRD results for the soot deposited on SZinc (b) show peaks at (00-001-0402, ZnSO 4 ·7H 2 O) and (01-089-0511). Meanwhile, the XRD results for the soot deposited on 316SNi (c) are consistent with the patterns of (00-026-1288, NiSO 4 ·6H 2 O) and (00-001-1286, NiS). Comparison of the results shows that the device made with 316SNi not only adsorbs more ppm value of the soot, but also adsorbs more sulfur. The XRD results also show a broad amorphous diffraction peak appearing at the 2θ = 0–12° range in the XRD diagrams, which is related to carbon atoms and is observed in all three patterns. These results are also confirmed by the EDX results (Fig. 6 ). As shown in Fig. 6 , the weight fraction of sulfur adsorbed by the device made using 316SNi is approximately 10 times that of the device made using SZinc and copper (Table 5 ). Previous reports have shown that the presence of heavy metals in soot from fuel combustion can originate from the engine body or its accessories, such as the exhaust. However, the XRD and EDX results in this report, considering the amount of these metals especially in relation to the soot-deposited 316SNi suggest that their source, in addition to the engine, could be the reaction of sulfur and oxygen with the metal of the device at a temperature of approximately 300°C to 450°C (exhaust gas temperature at the end of the exhaust pipe). This reaction leads to the formation of deposits such as NiSO 4 , CuSO 4 , ZnSO 4 , ZnO, CuO, and NiS. In other words, particularly in relation to device made of 316SNi, it resulted in sulfur absorption. While the enthalpy of formation of nickel oxide (-240.5 kJ/mol) is lower than that of nickel sulfide (-50.68 kJ/mol), XRD and EDX results show that in a device made of 316SNi, the dominant product of the reaction between nickel, oxygen, and sulfur is nickel sulfide. This can be attributed to the activation energy at the relatively low temperature of the exhaust end, which is required for the reaction of the nickel surface with oxygen and sulfur. This activation energy is lower for nickel sulfide (50–100 kJ/mol for NiS) than for nickel oxide (100–200 kJ/mol for NiO). Therefore, the formation of nickel sulfide is driven by the production of a kinetic product. Table 5 The weight percentages from the EDX results for the soot-deposited Cu, soot-deposited SZinc, and soot-deposited 316SNi. Type of Back Filter/Elements(Wt%) C O Si S Ca Fe Zn Ni Cu P Soot-deposited Cu 86.73 9.92 1.43 0.45 1.28 0.19 Soot-deposited SZinc 87.11 9.26 0.67 1.50 0.13 0.47 0.86 Soot-deposited 316SNi 32.83 27.63 15.51 24.03 3.4 EIS results Electrochemical Impedance Spectroscopy (EIS) in a 3.5% (w/w) NaCl solution was used to analyze the soot-deposited Cu/GCE (a), soot-deposited SZinc/GCE (b), and soot-deposited 316SNi/GCE (c). The Nyquist plots recorded after 20 min in a 3.5% (w/w) NaCl solution are shown in Fig. 7 . The semicircular region was related to Rpo, which represents the pore resistance due to the formation of ionically conducting paths across the soot coating. The Warburg impedance observed in the mid-frequency region is evidence of the effective barrier behavior of the soot film. The electrochemical parameters of the soot/electrolyte system were evaluated using Eissa1 software. We observed excellent agreement between the experimental results and the parameters obtained from the R(Q(RW)) equivalent circuit model for the soot-deposited Cu/GCE (a) and R(C(RW)) for the soot-deposited SZinc/GCE (b) and the soot-deposited 316SNi/GCE (c), where the chi-squared (χ²) value minimized at 10 − 4 (Fig. 7 ). The model of the soot/electrolyte system was built using series components. The first component is the bulk solution resistance of the soot and the electrolyte, Rs (R1). The second component is the parallel combination of the constant phase element (CPE) of the soot coating in the equivalent circuit of the soot-deposited Cu/GCE (a), Q, and R2, which represents Rpo. Rpo is the pore resistance, which arises from the formation of ionically conducting paths across the soot coating. The double-layer capacitance (Cdl) was parallel to Rpo in the equivalent circuits of the soot-deposited SZinc/GCE (b) and the soot-deposited 316SNi/GCE (c). Additionally, a series connection to Rpo, represented by W, accounts for the Warburg impedance of the soot film. The Warburg impedance (W) is due to pore formation on the surface of each electrode. The constant phase element (CPE) is introduced in parallel with Rpo in the equivalent circuit of the soot-deposited Cu/GCE (a), corresponding to the pores on the surface of the soot film. Simulation results for the soot film show that this electrical equivalent circuit was successfully applied to the experimental data, explaining the interface between the electrode/soot film and the electrolyte (Table 6 ). Instead of a pure capacitor, a constant phase element (CPE) was introduced in the fitting procedure to achieve a good agreement between the simulated and experimental data (the equivalent circuit of the soot-deposited Cu/GCE (a)). The impedance of CPE is defined as ZCPE = Q − 1 × (jω) −n , where Q represents a combination of properties related to the surface and electroactive species, independent of frequency. The parameter “n” is related to the slope of log Z versus log f. The value of “n” ranges from 0 to 1, with values closer to 1 indicating a smoother film surface (Mahmoudian et al., 2017 ). The EIS results show that the electrical resistance of soot deposited on 316SNi is much lower than that of soot deposited on SZinc and copper. Previous reports have shown that soot from engine combustion becomes electrically charged as it passes through an exhaust pipe. If this charge is discharged, soot clusters can form (Ju et al., 2023 ). Therefore, based on the EIS results, which confirm the lowest resistance for soot-deposited 316SNi, it can be concluded that the electrical discharge of soot particles in a device made of 316SNi is greater, thereby increasing the probability of soot particle accumulation on its surface. The results of log Z vs. log f, which show the total resistance of the soot-deposited Cu/GCE (a), soot-deposited SZinc/GCE (b), and soot-deposited 316SNi/GCE (c), confirm the inference from the simulation (Fig. 8 ). On the other hand, significant sulfide adsorption and NiS production lead to notable changes in the electron conductivity of the soot deposited on the 316SNi surface. According to previous reports, the electron conductivity of NiS is much higher than that of ZnO and Cu 2 O (electron conductivities of NiS, ZnO, and Cu 2 O are 10 4 S/m, 10 − 1 to 10 − 4 S/m, and 10 − 2 to 10 − 4 S/m, respectively) (Gahtar et al., 2021 ). Table 6 Electrochemical parameters obtained from the simulation of the EIS results for the soot-deposited Cu/GCE (a), soot-deposited SZinc/GCE (b), and soot-deposited 316SNi/GCE in a 3.5% (w/w) NaCl solution. The type of Back filter R1(Rs) Cdl Rpo W Q (CPE) n soot- deposited Cu /GCE 44.26 1737.01 2570.9 3.0817×10 − 5 0.89 soot- deposited SZinc/ GCE 45.966 0.00011479 483.4 605.88 soot-deposited 316SNi/GCE 43.345 7.383×10 − 9 191.6 404.12 The thermal conductivity of the substrate can also affect the particle size of the soot agglomerates formed on its surface. Other researchers have reported that particle size is inversely related to thermal conductivity (Karunarathne et al., 2025 ). The thermal conductivities of copper, SZinc, and 316SNi are 390–400 W/m O K, 50–60 W/m O K, and 16–25 W/m O K, respectively. The SEM results show that the size of the agglomerates is inversely related to the thermal conductivity of the device metals. 3.5 FTIR characterization FTIR characterization was used to identify the organic compounds in the soot deposited on the device. Based on previous reports, the presence of unburned hydrocarbons in soot has been documented (Wang & Chung, 2019 ). On the other hand, due to the lower temperature at the end of the exhaust pipe compared to the beginning of the pipe and the exhaust storage, where temperatures are much higher, the possibility of a new reaction between the particles forming soot on the devices is unlikely. In other words, if any type of bond or functional group is observed in the soot deposited on the devices, it should be interpreted based on previously reported results (Shabnam et al., 2019 ). This is not related to the reaction of soot particles on the surface of the devices. Figure 9 shows the FTIR spectra of the soot deposited on the surfaces of Cu (a), SZinc (b), and 316SNi (c). The peak at 3126.43 cm − 1 is related to O–H stretching vibrations, possibly from alcohols or phenols (hydrogen-bonded, broad signal). The existence of C–H stretching vibrations, likely from alkanes (sp³ hybridized C–H bonds), was confirmed by the peak at 2921.57 cm − 1 . A broad peak, possibly indicative of CO 2 contamination common in IR spectra due to atmospheric CO 2 was observed at 2360.58 cm − 1 . The peak at 1576.32 cm − 1 corresponds to C = C stretching in aromatic or conjugated systems (aromatic rings or alkenes). The presence of C–O bonding, which can be characteristic of ethers, esters, or alcohols, was detected at 1116.01 cm − 1 in the FTIR spectrum of the deposited soot on the surface of Cu. As seen in the FTIR spectrum of the deposited soot on the surface of SZinc, the O–H, C–H, CO 2 , C = C, and C–O groups appear with a slight shift, similar to the spectrum of the deposited soot on the surface of Cu. In addition, peaks related to C–H (symmetric stretching in CH 2 groups, characteristic of aliphatic chains), C = O (stretching vibrations, typical of carbonyl groups such as ketones, aldehydes, or esters), C–H (bending vibrations, common in aliphatic hydrocarbons or methyl groups), and out-of-plane bending vibrations, possibly from aromatic rings or halogenated compounds, are also observed at 2849.41 cm − 1 , 1719.76 cm − 1 , 1457.23 cm − 1 , and 602.90 cm − 1 , respectively. All the peaks or functional groups associated with the soot deposited on copper and SZinc are also present in the soot deposited on 316SNi. Therefore, it can be concluded that the type of metal used to make the device at low exhaust end temperatures did not have a significant effect on the type of organic compounds. However, it had a significant effect on the reaction of sulfur and oxygen with the metal used to make the device. Based on the results obtained, it can be concluded that using a 316SNi device leads to increased sulfur absorption, and one of the reasons for the greater mass deposited on the surface of 316SNi could be this factor. 4 Conclusion In this study, hot-dip galvanized steel (SZinc), copper, and Nickel electroplated 316 Stainless steel (316SNi) were used separately to make the back filter. The inside of the back filter was designed so that the exhaust gases would follow a sinusoidal path to increase interaction with the half-plates. This design did not negatively affect engine performance. the ppm value of soot deposited on 316SNi is approximately 5 and 3 times higher than that of the soot deposited on a back filter made of copper and SZinc in the absence and presence of PTFE respectively. Additionally, the amount of sulfide adsorbed on the 316SNi back filter was 10 times higher than on the other two materials. The reasons for this significant difference were explained by the following factors: Inverse relationship between the thermal conductivity of the alloy or metal and the particle size of the soot adsorbed on the back filter. Inverse relationship between the electrical resistance of the deposited soot and the amount of soot deposited. To interpret the results, impedance spectroscopy was used to investigate the electrical resistance of the adsorbed soot, and X-ray diffraction (XRD) was used to identify the mineral compounds formed on the surface of the back filter. The lower thermal conductivity of 316SNi compared to the other two materials, the lower electrical resistance of the adsorbed soot on 316SNi, and the formation of nickel sulfide as a kinetic product on the steel surface can be considered some of the significant factors. Declarations Acknowledgments: We would like to thank the research and technology council of Farhangian University for financial support through this investigation under post doctorate project No. 50000/17375/600. Funding: This is not applicable' for that specific section. Authors’ Contributions: Mohammad reza Mahmoudian designed the device, interpreted and write the article, while Zohreh Haghighi Kafash edited, performed characterizations and experiments. Ethical Approval: This is not applicable' for that specific section. Consent to Publish: This is not applicable' for that specific section. Consent to Participate: This is not applicable' for that specific section. Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Data Availability Statement: This is not applicable' for that specific section. We have included all relevant data and the methodology for constructing the device in the text. References Al-Wakeel HB, Karim ZA, Al-Kayiem HH, Jamlus MH (2012) Soot reduction strategy: A review. J Appl Sci 12:2338–2345. https://doi.org/10.3923/jas.2012.2338.2345 Caliskan H, Mori K (2017) Environmental, enviroeconomic and enhanced thermodynamic analyses of a diesel engine with diesel oxidation catalyst (DOC) and diesel particulate filter (DPF) after-treatment systems. 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Environ Sci Pollut Res 29:58664–58674. https://doi.org/10.1007/s11356-022-19928-y Schemes Scheme 1 is available in the Supplementary Files section Supplementary Files Scheme1.png Scheme 1: the interaction of exhaust gases with a 316SNi back filter Cite Share Download PDF Status: Published Journal Publication published 10 Sep, 2025 Read the published version in Environmental Science and Pollution Research → Version 1 posted Editorial decision: Major Revision 16 Jul, 2025 Reviewers agreed at journal 16 May, 2025 Reviewers invited by journal 15 May, 2025 Editor assigned by journal 06 May, 2025 First submitted to journal 01 May, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6526930","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":457097533,"identity":"be7c03d8-b73f-421c-8476-11826d9bd8c6","order_by":0,"name":"Zohreh Haghighi Kafash","email":"","orcid":"","institution":"Farhangian Teacher Education University: Farhangian University","correspondingAuthor":false,"prefix":"","firstName":"Zohreh","middleName":"Haghighi","lastName":"Kafash","suffix":""},{"id":457097534,"identity":"84e23cf5-0c07-4818-a5da-3d0c8e31f0c6","order_by":1,"name":"Mohammad Reza Mahmoudian","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA3UlEQVRIiWNgGAWjYPCCAyDCAEjaMDBIkKgljUQtQHyYsBbdBt4HTDdq7kTzSyRvPPBzx/nE/tnNBx8w1NhE49JidoDdgDnn2LPcmTPSCg72nrmdOOPOsWQDhmNpuQ04tbAxMOewHc7dcCPH4ABv2+3Ehhs5ZhKMDYcJaPkH0XLwb9u5xPlEacltg2g5zNt2IHEDcVr6DufO7HlWcFi2Ldl44420ZIMEgn75dji3nz1588e3bXay824kH3zwocYGpxYG+QfsP5D5jmCVCbiUYwP2pCgeBaNgFIyCkQEAQEdkuAac30YAAAAASUVORK5CYII=","orcid":"","institution":"Farhangian Teacher Education University: Farhangian University","correspondingAuthor":true,"prefix":"","firstName":"Mohammad","middleName":"Reza","lastName":"Mahmoudian","suffix":""}],"badges":[],"createdAt":"2025-04-25 08:23:56","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6526930/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6526930/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s11356-025-36938-8","type":"published","date":"2025-09-10T15:57:05+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":83067504,"identity":"5d2b5e61-9151-4e60-b22f-b383d4e21b7c","added_by":"auto","created_at":"2025-05-19 15:53:53","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":592119,"visible":true,"origin":"","legend":"\u003cp\u003eFESEM (a) and EDX (b) results of Ni electroplated 316 stain less steel.\u003c/p\u003e","description":"","filename":"image1.png","url":"https://assets-eu.researchsquare.com/files/rs-6526930/v1/6f38f17c36fdad4fc64b4e36.png"},{"id":83067657,"identity":"55cdbe0d-703e-4f40-9c6a-38b48e073168","added_by":"auto","created_at":"2025-05-19 16:01:53","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":317372,"visible":true,"origin":"","legend":"\u003cp\u003eThe structure of the device made of pure copper (99%), hot-dip galvanized steel sheet, and Ni electroplated on 316 stainless steel, with the properties specified in Table 3.\u003c/p\u003e","description":"","filename":"image2.png","url":"https://assets-eu.researchsquare.com/files/rs-6526930/v1/a3800a5ace090218e7f6fd7b.png"},{"id":83067662,"identity":"bfd65e14-9b29-44a5-a852-698dda2f85f4","added_by":"auto","created_at":"2025-05-19 16:01:54","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":734678,"visible":true,"origin":"","legend":"\u003cp\u003eThe copper prototype, ready for installation at the end of the exhaust downpipe (a). Upon completion of the component's manufacturing and preparation, a Back Filter was affixed to the end of the exhaust pipe (b).\u003c/p\u003e","description":"","filename":"image3.png","url":"https://assets-eu.researchsquare.com/files/rs-6526930/v1/f643aee4b4bc976090a36181.png"},{"id":83067654,"identity":"ec6f32a6-5eae-428a-85f1-38a12e702299","added_by":"auto","created_at":"2025-05-19 16:01:53","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":1518024,"visible":true,"origin":"","legend":"\u003cp\u003eFESEM results of the soot deposited on a device made of Cu (a and b), SZinc (c and d), and 316SNi (e).\u003c/p\u003e","description":"","filename":"image4.png","url":"https://assets-eu.researchsquare.com/files/rs-6526930/v1/3826c46bc79e273ac58c5267.png"},{"id":83067537,"identity":"80e9b991-1b18-42cb-82a2-590404e2e517","added_by":"auto","created_at":"2025-05-19 15:53:54","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":359951,"visible":true,"origin":"","legend":"\u003cp\u003eXRD results for the soot-deposited Cu (a), the soot-deposited SZinc (b), and the soot-deposited 316SNi (c).\u003c/p\u003e","description":"","filename":"image5.png","url":"https://assets-eu.researchsquare.com/files/rs-6526930/v1/07c72e55e03d32884386e388.png"},{"id":83067519,"identity":"c74643b6-580b-4d2a-9d11-4d70347fa591","added_by":"auto","created_at":"2025-05-19 15:53:53","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":356225,"visible":true,"origin":"","legend":"\u003cp\u003eEDX results of the soot-deposited Cu (a), soot-deposited SZinc (b), and soot-deposited 316SNi (c).\u003c/p\u003e","description":"","filename":"image6.png","url":"https://assets-eu.researchsquare.com/files/rs-6526930/v1/bb92eae8c0ff974c82edf33a.png"},{"id":83067514,"identity":"c3852168-e49f-484a-917c-a969fae75cec","added_by":"auto","created_at":"2025-05-19 15:53:53","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":269717,"visible":true,"origin":"","legend":"\u003cp\u003eThe Nyquist plots of the soot- deposited Cu /GCE (a), soot- deposited SZinc/ GCE (b) and soot- deposited 316SNi/GCEin 3.5 % (w/w) NaCl solution.\u003c/p\u003e","description":"","filename":"image7.png","url":"https://assets-eu.researchsquare.com/files/rs-6526930/v1/728b7d90965c7f89b1acfe16.png"},{"id":83067658,"identity":"a54a1866-0c9e-4fa5-a102-8abb008132d8","added_by":"auto","created_at":"2025-05-19 16:01:53","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":83946,"visible":true,"origin":"","legend":"\u003cp\u003eThe results of log Z vs. log f for the soot-deposited Cu/GCE (a), soot-deposited SZinc/GCE (b), and soot-deposited 316SNi/GCE (c) in a 3.5% (w/w) NaCl solution.\u003c/p\u003e","description":"","filename":"image8.png","url":"https://assets-eu.researchsquare.com/files/rs-6526930/v1/7596a744a4876b30dd0fd6e3.png"},{"id":83068067,"identity":"fad1b135-de1c-4830-99ec-21085a3d3e28","added_by":"auto","created_at":"2025-05-19 16:09:53","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":111519,"visible":true,"origin":"","legend":"\u003cp\u003eThe FTIR spectra of the deposited soot on the surface of Cu (a), SZinc (b), and 316SNi (c).\u003c/p\u003e","description":"","filename":"image9.png","url":"https://assets-eu.researchsquare.com/files/rs-6526930/v1/66959b468d278d3b76b10abb.png"},{"id":91359029,"identity":"2cc24d7b-e294-4ac6-ac01-0a1633fe65cd","added_by":"auto","created_at":"2025-09-15 16:04:24","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":5829554,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6526930/v1/d77549a0-5134-4c0c-b4a1-f9aa431167ae.pdf"},{"id":83067656,"identity":"d87711ab-1bb5-4482-bb78-1942eea19a64","added_by":"auto","created_at":"2025-05-19 16:01:53","extension":"png","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":116098,"visible":true,"origin":"","legend":"\u003cp\u003eScheme 1: the interaction of exhaust gases with a 316SNi back filter\u003c/p\u003e","description":"","filename":"Scheme1.png","url":"https://assets-eu.researchsquare.com/files/rs-6526930/v1/5f024edc0cb157b1d6f03dd2.png"}],"financialInterests":"","formattedTitle":"Introducing a Back Filter: The Impact of Metal Type on Reducing Particulate Matter and Sulfide Emissions from Diesel Engine Exhaust","fulltext":[{"header":"1 Introduction","content":"\u003cp\u003eNowadays, one of the global concerns that have received more attention is the issue of air pollution and climate change (Miller et al., \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Industrialization is accelerating and causing many negative consequences for both humanity and the environment (Ramakrishna \u0026amp; Jose, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). In the majority of instances, making amends for inflicted damage is irreversible. In recent years, in the metropolitan areas, the escalating consumption of fossil fuels by internal combustion engine has imposed significant costs on the entire economy, and air pollution has become a hazardous event (Carranza et al., \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Kumar \u0026amp; Choudhary, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; Verma et al., \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Studies have shown that, compared to other pollutants, particles with diameters between PM2.5 and PM10 have more severe effects on the health of certain groups such as children, the elderly, and those with underlying diseases. In addition, its effects on plants have been fully confirmed (Stanek \u0026amp; Brown, \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Zhou et al., \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Guo et al., \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2024\u003c/span\u003e; Wang et al., \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2020\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eDiesel engines are popular due to their advantages such as, robustness, reliability, and easy maintenance. In addition, due to their high energy density, it enables them to produce more power per unit of fuel, making them efficient and cost-effective engines (Saravanamuthu et al., \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Unfortunately, diesel engines are one of the important sources of air pollution in the production of carbon-based suspended particles in the form of soot (black carbon) (Wei \u0026amp; Wang, \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). The incomplete combustion of hydrocarbons such as fossil fuels, biofuels, and biomass causes a substantial increase in soot emissions and accumulation in the environment. Soot is a kind of amorphous carbonaceous nanomaterial that has a high percentage of macropores, low ash content, and volatiles. Every year, nearly 8\u0026nbsp;million metric tons (MMTs) of soot are released into the environment (Philomina et al., \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Chylek et al., \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; Uttaravalli et al., \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). Exposure to soot has numerous harmful effects on human health. Short-term exposure to soot may cause exacerbated cardiovascular and respiratory symptoms, reduce visibility, and cause nose and eye irritation, and therefore, increase medical needs and hospitalizations. Long-term exposure to soot may lead to premature death, asthma, bronchitis, lung cancer, stroke, and heart attack. The fundamental key to a pollution-free world is understanding the harmful effects of these contaminants and identifying effective ways to control them (Seaton et al., \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e1995\u003c/span\u003e; Sydbom et al., \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2001\u003c/span\u003e; Sahu et al., \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Nelin et al., \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Ristovski et al., \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Watanabe and Oonuki, \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e1999\u003c/span\u003e; Su et al., \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e1989\u003c/span\u003e; Gopal et al., \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2021\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThrough proper treatment, collected and recycled carbon black can be used for a wide range of products. Recent research has shown that diesel soot nanoparticles can be used as feedstock to produce high performance activated carbon with high carbon dioxide adsorption. The activated carbons produced have shown a high CO\u003csub\u003e2\u003c/sub\u003e uptake capacity, favorable adsorption kinetics, and high CO\u003csub\u003e2\u003c/sub\u003e/N\u003csub\u003e2\u003c/sub\u003e selectivity after combined oxidative treatment (Guerrero Pe\u0026ntilde;a et al., \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Uttaravalli et al. (\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2022\u003c/span\u003e) emphasized the environmental advantages of recycling soot to mitigate emissions from hydrocarbon fuel combustion. They noted that incorporating recycled soot can enhance the mechanical, thermal, and electrical properties of products and serve as an effective adsorbent for pollutants, thus offering a sustainable alternative to the current carbon. This study focused on the sustainable use of recycled soot (carbon black) from diesel engine exhaust, emphasizing its potential applications in composite materials, energy storage devices, and the removal of various contaminants in the treatment of air and water. On the other hand, Lough et al. (\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2005\u003c/span\u003e) found that 19% of particulate matters (PM10) were consisted of metals such as Si, Fe, Ca, Na, Mg, Al, and K. Recent reports have shown that metals such as zinc, nickel, and copper have catalytic properties on gases produced by burning various fossil fuels. Prikhod\u0026rsquo;ko et al. (\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2014\u003c/span\u003e) reported the effect of copper and nickel substrates in the flame zone of premixed propane-oxygen and found nickel substrates to be more efficient for graphene growth.\u003c/p\u003e \u003cp\u003eSo far, various methods have been introduced to absorb soot or minimize it in the process of fossil fuel combustion (Shukla et al., \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Many of these methods are focused on engine efficiency, fuel type (Zhang et al., \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2018\u003c/span\u003e), the use of different catalysts (Caliskan \u0026amp; Mori, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2017\u003c/span\u003e) in the exhaust pipe tank, and the use of different filters (Al-Wakeel et al., \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2012\u003c/span\u003e), but the main priority of soot collection to reduce the resulting pollution should be considered (Uttaravalli et al., \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). In line with this goal, simple installation of the filter, easy removal of soot accumulated in the filter, prevention of negative impact on engine performance, and most importantly, low price and the possibility of using it multiple times should be considered (Luo et al., \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). On the other hand, creating incentives for financial managers to install and remove accumulated waste is one of the things that affect its social efficiency (Ling et al., \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Manni \u0026amp; Runhaar, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). Therefore, implementing any type of project, such as fabricating a simple device, making changes in fuel, improving engine performance, improving engine alloys, and improving engine oil, not only impacts the health and quality of life of organisms but also serves as an interesting topic for research.\u003c/p\u003e \u003cp\u003eThis study introduces a back filter installed at the end of the exhaust pipe of city buses and investigates the impact of the metal type used in its construction on the absorption of suspended particles and the reduction of sulfides in diesel engine exhaust gases. The back filter is constructed from three different metals: copper, zinc, and nickel, each used separately. Due to the high cost of pure nickel, nickel was electroplated onto stainless steel 316 (316SNi), while hot-dip galvanized steel sheet was utilized as a substitute for zinc (SZinc).\u003c/p\u003e"},{"header":"2 Experimental methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Methodology and strategy\u003c/h2\u003e \u003cp\u003eThe research methodology and strategy were structured around specific steps and questions that needed to be addressed:\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003e1-Designing and Installing a Back Filter:\u003c/h3\u003e\n\u003cp\u003eThe back filter was designed and installed at the end of the exhaust system of city buses, where engineers had not previously implemented any solutions. This placement allows for the absorption of pollutants before exhaust gases are released into the atmosphere, making any captured pollution beneficial.\u003c/p\u003e\n\u003ch3\u003e2-Characteristics of the Manufactured Back Filter:\u003c/h3\u003e\n\u003cp\u003eThe back filter was required to meet several key characteristics: a) cost-effectiveness, b) sulfur absorption capability, c) reusability, d) quick and easy installation, and e) no negative impact on bus engine performance\u003c/p\u003e \u003cp\u003eBased on these features, a back filter was designed and three types of metals, copper, zinc, and nickel, were considered for its manufacture. In order for the back filter to be economical Nickel metal was electroplated on 316 Stain less steel (316SNi) and hot-dip galvanized steel sheet was used to replace zinc (SZinc). Other researchers have reported the effectiveness of nickel and its alloys as a suitable catalyst, but because the fabrication of the back filter using this type of metal is very expensive and on the other hand, alloys with a high percentage of nickel such as Raney nickel are very rare in Iran, we decided to electroplate Ni on the surface of 316 Stainless steel. Poly (tetrafluoroethylene) (PTFE) powder (1 Micron, Nano Bonyan Asia, Tehran, Iran) was utilized to enhance soot adsorption, sandwiched between two metal plates in each back filter. The charge created by the vibration of PTFE powder, which is usually a triboelectric charge, can help attract soot onto the filter backing. A city bus from Tehran Municipality was selected, using EURO 3 fuel, with the specifications listed in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The engine specifications of the bus are listed in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. After each test, a technical inspection of the engine was performed to ensure that all conditions were the same for all tests.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eGeneral specifications of the EURO 3 fuel\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"2\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eParameter\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSpecification\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSulfur Content\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMax 350 ppm (parts per million) for diesel; Max 150 ppm for gasoline\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAromatic Hydrocarbons\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMax 35% by volume\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOlefins (Gasoline)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMax 18% by volume\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBenzene Content\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMax 1% by volume\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCetane Number (Diesel)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMin 51\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDistillation (Gasoline)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u0026minus;\u0026thinsp;90% of the fuel must evaporate at 210\u0026deg;C\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVolatility (Gasoline)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMust comply with Reid Vapor Pressure (RVP) standards for summer and winter\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDensity (Diesel)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e820\u0026ndash;845 kg/m\u0026sup3; at 15\u0026deg;C\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLead Content (Gasoline)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eLead-free (Max 0.005 g/L)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOxygen Content (Gasoline)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMax 2.7% by weight\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePolycyclic Aromatics (Diesel)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMax 11% by weight\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAdditives\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eUse of specific additives is permitted to improve combustion and engine performance\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eParticulate Matter (PM)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eReduction compared to previous standards\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eThe specifications of the subject bus (Volvo B9R)\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"2\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCategory\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSpecifications\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eChassis\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eVolvo B9R, EURO 3\u003c/p\u003e \u003cp\u003e-compliant chassis with R9700 body and double-glazed adhesive windows.\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eEngine\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e- Model: D9B 380, inline, 6-cylinder, 4-stroke.\u003c/p\u003e \u003cp\u003e- Power: 380 hp at 1900 rpm.\u003c/p\u003e \u003cp\u003e- Torque: 1740 Nm at 1200\u0026ndash;1400 rpm.\u003c/p\u003e \u003cp\u003e- Displacement: 9.4 liters.\u003c/p\u003e\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e- Features: Turbocharger, intercooler, electronic fuel control (EMS2), EURO 3 \u0026amp; EURO 4 emission standards.\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGearbox\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e- Model: I-Shift V2412AT.\u003c/p\u003e \u003cp\u003e- Type: Fully automatic, 12-speed forward, 4 reverse gears.\u003c/p\u003e \u003cp\u003e- Manual mode option with gear locking.\u003c/p\u003e\u003cp\u003e- Fuel-saving software.\u003c/p\u003e\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e- Hydraulic retarder: VR3250 with braking power of 400\u0026ndash;600 kW, integrated with EBS.\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSuspension \u0026amp; Axles\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e- Front axle: Standard camber, electronic suspension.\u003c/p\u003e \u003cp\u003e- Rear axle: Volvo RS 1228B with 4 air springs, ratio 2.85:1.\u003c/p\u003e \u003cp\u003e- Hydraulic telescopic dampers.\u003c/p\u003e\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSteering\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e- Adjustable hydraulic steering with a 450 mm diameter steering wheel.\u003c/p\u003e \u003cp\u003e- Max turning angle: 50\u0026deg;.\u003c/p\u003e\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBraking System\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e- Disc brakes on both axles, dual-circuit air brakes.\u003c/p\u003e \u003cp\u003e- Features: ABS, EBD, EBS, ASR, TCS.\u003c/p\u003e \u003cp\u003e- Automatic lining adjustment, asbestos-free linings.\u003c/p\u003e\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e- Integrated retarder and brake cooling system.\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eElectrical System\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e- Voltage: 24V.\u003c/p\u003e \u003cp\u003e- Batteries: 2 x 225 Ah.\u003c/p\u003e \u003cp\u003e- Alternators: 2 x 110 Ah.\u003c/p\u003e \u003cp\u003e- Emergency battery cut-off system.\u003c/p\u003e\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTires\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e- Configuration: Tubeless tires.\u003c/p\u003e \u003cp\u003e- Sizes: 295/80R22.5 \u0026amp; 315/80R22.5.\u003c/p\u003e \u003cp\u003e- Steel rims.\u003c/p\u003e\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDimensions\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e- Length: 12,500 mm.\u003c/p\u003e \u003cp\u003e- Width: 2,550 mm.\u003c/p\u003e \u003cp\u003e- Height: 3,700 mm.\u003c/p\u003e \u003cp\u003e- Wheelbase: 6,300 mm.\u003c/p\u003e \u003cp\u003e- Cabin height: 1,950 mm.\u003c/p\u003e\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eWeights\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e- Maximum weight with passengers and cargo: 19,000 kg.\u003c/p\u003e \u003cp\u003e- Front axle load limit: 7,500 kg.\u003c/p\u003e \u003cp\u003e- Rear axle load limit: 12,000 kg.\u003c/p\u003e\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePassenger Capacity\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e- Standard: 47\u0026thinsp;+\u0026thinsp;1\u0026thinsp;+\u0026thinsp;1.\u003c/p\u003e \u003cp\u003e- Classic: 44\u0026thinsp;+\u0026thinsp;1\u0026thinsp;+\u0026thinsp;1.\u003c/p\u003e \u003cp\u003e- VIP: 25\u0026thinsp;+\u0026thinsp;1\u0026thinsp;+\u0026thinsp;1.\u003c/p\u003e\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFuel Tank\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e- Capacity: 600 liters.\u003c/p\u003e \u003cp\u003e- Dual-side fueling capability near the front axle.\u003c/p\u003e\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSafety Features\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e- FUPS (Front Underrun Protection System).\u003c/p\u003e \u003cp\u003e- FIP (Frontal Impact Protection).\u003c/p\u003e \u003cp\u003e- KIP (Driver Knee Impact Protection).\u003c/p\u003e\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eComfort Features\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e- Passenger: Adjustable reclining seats, air conditioning, individual sound systems, 2 LCD screens, 1 VCD player.\u003c/p\u003e \u003cp\u003e- Double-glazed, adhesive-secured windows.\u003c/p\u003e\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e- Cabin: Fridge, water cooler, coffee maker, electric blinds, sleeping cabin with mattress and pillows, contact intercom.\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e- Lighting: LED-based ambient lighting and reading lights.\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eEmission Standard\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eEURO 3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAdditional Features\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e- Satellite navigation (GPS).\u003c/p\u003e \u003cp\u003e- Emergency equipment: Fire extinguishers (2), emergency hammers (4).\u003c/p\u003e \u003cp\u003e- Air-tight baggage doors with warning systems.\u003c/p\u003e\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e- Advanced lighting: Digital front display, rearview cameras, and warning systems for gearbox brakes and motor compartments.\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Apparatus and Characterizations\u003c/h2\u003e \u003cp\u003eThe constituents, morphology, and chemical properties of soot-deposited on half-sheets were investigated by; energy dispersive X-ray (EDX) spectroscopy, field emission scanning electron microscopy (FESEM, Quanta 200F), and FTIR spectroscopy (Spectrum 400 (FT-IR/FT-FIR spectrometer) were used. The phase of each sample was studied by X-ray diffraction (Siemens D5000) with Cu Kα radiation. The electrochemical properties of the materials deposited on the half-plates were studied using impedance spectroscopy (EIS). All the electrochemical experiments were performed using a PalmSens potentiostat/galvanostat. General-purpose software (PSTrace 5.10.5604) and a frequency response analyzer (Eissa1), installed on a computer and interfaced with the potentiostat, were used to conduct the experiments and analyze the data. Electrochemical impedance spectroscopy (EIS) measurements were performed in a 3.5% w/w NaCl solution. The impedance spectra for the determination of the charge transfer resistance of the soot-deposited Cu/GCE, soot-deposited SZinc/GCE, and soot-deposited soot-deposited 316SNi /GCE were obtained over a frequency range of 100 kHz\u0026ndash;0.1 Hz, with an acquisition of 10 points per decade. A saturated Ag/AgCl electrode and a platinum foil served as the reference and counter electrodes, respectively.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e2.3 Electrode preparation\u003c/h2\u003e \u003cp\u003eOne milligram (1 mg) of soot-deposited on half-plates in a device made of copper, hot-dip galvanized steel sheet (SZinc), and 316 stainless steel (316SNi) (referred to as soot-deposited Cu, soot-deposited SZinc, and soot-deposited 316SNi) was dispersed in 1 mL of deionized (DI) water using ultrasonication for 30 minutes to produce a dark brown homogeneous suspension. Then, 10 \u0026micro;L of the homogeneous suspension was drop-cast onto the surface of a polished glassy carbon electrode (GCE) and dried at room temperature. Next, 3 \u0026micro;L of Nafion 117 (1% m/v) was drop-cast onto the surface of the soot-deposited Cu/GCE, soot-deposited SZinc/GCE, and soot-deposited 316SNi/GCE to enhance the stability of the electrode.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e2.4 Electroplating of Ni on the surface of 316Stainless steel\u003c/h2\u003e \u003cp\u003eTo electroplate nickel onto the surface of a stainless steel 316 back filter, we followed the method reported by Gay et al. (1987). The process involved the following steps:\u003c/p\u003e \u003cp\u003eFirst, the plates were cleaned by immersing them in an electrolytic bath containing 10% V/V sulfuric acid while connected to the anode of a DC power source. The second step involved rinsing the plates to remove any residual sulfuric acid. The third step was nickel plating, achieved by immersing the plates in a nickel electrolytic solution composed of nickel chloride and hydrochloric acid, with the voltage adjusted according to the surface area of each plate. Figure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e presents the FESEM (a) and EDX (b) results of the stainless steel 316 plates after nickel electroplating.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIt is important to note that nanotechnology methods were not employed to enhance the surface area of the deposited nickel for two reasons: 1) Cleaning the plates and removing soot from the surface would have been challenging and would require washing methods that could lead to environmental pollution, which end users would likely be reluctant to undertake; and 2) Production costs would have increased.\u003c/p\u003e \u003c/div\u003e"},{"header":"3 Results and discussion","content":"\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Device installation and amount of soot deposited\u003c/h2\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e shows the structure of the back filter, which is made of pure copper (99%), SZinc, and 316SNi, with the properties specified in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. Each plate consisted of two parallel metal layers separated by a distance of 2 mm, creating a chamber for PTFE powder. A total of 3 g, 5 g, and 7 g of PTFE powder were added to plates with radii of 1.5 cm, 2.5 cm, and 4.5 cm, respectively. The angles of the half-plates with respect to the central rod were considered to be 30\u0026deg;, 45\u0026deg;, and 90\u0026deg;. The direction of the half-plates was aligned with that of the exhaust gases. All the half-plates were sandblasted to achieve a near-white surface profile as per Swedish specification SA 2.5 (Venison, \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e1973\u003c/span\u003e), then washed with methanol to remove oil stains, and finally installed at the end of the exhaust pipe. First, three SZinc back filters were made with angles 30\u0026deg;, 45\u0026deg;, and 90\u0026deg; relative to the vertical axis of the device respectively, and each was installed on the bus exhaust. The results of the amount of soot deposited on the devices at different angles, along with the opinions of engineers and drivers on engine performance after installing the back filter, led to the selection of 45\u0026deg;. The 30\u0026deg; angle was not considered due to the small amount of soot deposited on the plates, and the 90\u0026deg; angle was not considered due to the obstruction of exhaust gas passage (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e (a and b)). It is important to note that the back filter is installed at the end of the exhaust pipe in such a way that a plate with a smaller diameter initially encounters the exhaust gases. This prevents the small half-plate from being masked by the exhaust gases if the back filter is installed in the opposite direction. Selecting three half-plates with different diameters also reduces the possibility of a negative effect on exhaust performance for the exhaust gases resulting from engine combustion. Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e (a) and (b) shows the ppm value of soot deposited on the back filter made of copper, SZinc, and 316SNi in absence and presence of PTFE powder. It is well know that the type of charge created by the vibration of PTFE powder is typically a triboelectric charge. This occurs due to the triboelectric effect, where materials become electrically charged after coming into contact with each other and then separating. In the case of PTFE, its properties allow it to gain or lose electrons when subjected to mechanical vibrations, leading to the generation of static electricity. PTFE is known to gain a negative charge when it comes into contact with metals like steel, which tends to lose electrons and thus acquire a positive charge. As mentioned in the experimental section, the ppm of soot deposited on the filters after installation on a bus with specific fuel consumption and specifications was determined after traveling a distance of 1813 km. It should be noted that not only was this distance the same for all three filters, but the route traveled was also considered identical. Before installing each of these filters, a technical inspection of the bus was carried out to ensure that no changes were made to the test conditions. As shown in Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e, the ppm value of soot deposited on 316SNi is approximately 5 and 3 times higher than that of the soot deposited on a back filter made of copper and SZinc in the absence and presence of PTFE respectively. Since the use of PTFE has been shown to absorb more soot, it has been shown that soot particles become negatively charged as they pass through the exhaust pipe and are neutralized and absorbed when they come into contact with the back filter plates, which are positively charged due to the presence of PTFE.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eThe type of Alloy and metal\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"13\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c11\" colnum=\"11\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c12\" colnum=\"12\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c13\" colnum=\"13\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eType of device/wt%\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"11\" nameend=\"c12\" namest=\"c2\"\u003e \u003cp\u003e\u0026rarr;All data is based on EDX Results\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"1\" nameend=\"c13\" namest=\"c13\"\u003e\u0026nbsp;\u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHot-dip galvanized steel sheet\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eO\u003c/p\u003e \u003cp\u003e6.12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eAl\u003c/p\u003e \u003cp\u003e0.30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eS\u003c/p\u003e \u003cp\u003e0.22\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eCa\u003c/p\u003e \u003cp\u003e0.21\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eFe\u003c/p\u003e \u003cp\u003e7.78\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eZn\u003c/p\u003e \u003cp\u003e85.37\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c13\" namest=\"c12\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ecopper\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eO\u003c/p\u003e \u003cp\u003e4.94\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eCu\u003c/p\u003e \u003cp\u003e95.06\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c13\" namest=\"c12\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e316 stainless steel\u003c/p\u003e \u003cp\u003e(before electroplating)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eC\u003c/p\u003e \u003cp\u003e7.61\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eO\u003c/p\u003e \u003cp\u003e4.66\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eNa\u003c/p\u003e \u003cp\u003e0.25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eSi\u003c/p\u003e \u003cp\u003e0.56\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eP\u003c/p\u003e \u003cp\u003e0.04\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eS\u003c/p\u003e \u003cp\u003e0.04\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003eCa\u003c/p\u003e \u003cp\u003e0.24\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003eCr\u003c/p\u003e \u003cp\u003e17.07\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003eMn\u003c/p\u003e \u003cp\u003e1.26\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003eFe\u003c/p\u003e \u003cp\u003e60.99\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c13\" namest=\"c12\"\u003e \u003cp\u003eNi\u003c/p\u003e \u003cp\u003e6.50\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003ePPM value of soot-depositedon the filter back made of Copper, Szinc and 316SNi, in the absence (a) and presence of PTFE (b).\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eType of material used in the back filter\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCopper\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSZinc\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e316SNi\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eppm value (In the absent of PTFE)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e52400\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e67900\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e318500\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eppm value (In the presence of PTFE)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e75100\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e77200\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e223600\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e3.2 FESEM results\u003c/h2\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e shows the FESEM results of the soot deposited on a device made of copper (soot- deposited Cu), SZinc (soot-deposited SZinc) and 316SNi (soot-deposited316SNi). The histogram shows that the average size of the soot deposited on copper and SZinc is approximately 26 nm and 27 nm, respectively, while the size of the soot deposited on 316SNi is much larger, more compact, and in the microscale range. According to the FESEM results, the porosity of the soot deposited on Cu and SZinc is much higher compared to that of the soot deposited on 316SNi, and these results are further confirmed by the impedance spectroscopy results presented in the next section.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003e3.3 XRD and EDX results\u003c/h2\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e shows the XRD results for soot deposited on Cu (a), soot deposited on SZinc (b), and soot deposited on 316SNi (c). The XRD pattern for the soot deposited on Cu (a) shows peaks corresponding to (00-002-1195, copper sulfate hydrate (antlerite)) and (00-003-0892, Cu\u003csub\u003e2\u003c/sub\u003eO (cuprite)). The XRD results for the soot deposited on SZinc (b) show peaks at (00-001-0402, ZnSO\u003csub\u003e4\u003c/sub\u003e\u0026middot;7H\u003csub\u003e2\u003c/sub\u003eO) and (01-089-0511). Meanwhile, the XRD results for the soot deposited on 316SNi (c) are consistent with the patterns of (00-026-1288, NiSO\u003csub\u003e4\u003c/sub\u003e\u0026middot;6H\u003csub\u003e2\u003c/sub\u003eO) and (00-001-1286, NiS). Comparison of the results shows that the device made with 316SNi not only adsorbs more ppm value of the soot, but also adsorbs more sulfur. The XRD results also show a broad amorphous diffraction peak appearing at the 2θ\u0026thinsp;=\u0026thinsp;0\u0026ndash;12\u0026deg; range in the XRD diagrams, which is related to carbon atoms and is observed in all three patterns. These results are also confirmed by the EDX results (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e). As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e, the weight fraction of sulfur adsorbed by the device made using 316SNi is approximately 10 times that of the device made using SZinc and copper (Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). Previous reports have shown that the presence of heavy metals in soot from fuel combustion can originate from the engine body or its accessories, such as the exhaust. However, the XRD and EDX results in this report, considering the amount of these metals especially in relation to the soot-deposited 316SNi suggest that their source, in addition to the engine, could be the reaction of sulfur and oxygen with the metal of the device at a temperature of approximately 300\u0026deg;C to 450\u0026deg;C (exhaust gas temperature at the end of the exhaust pipe). This reaction leads to the formation of deposits such as NiSO\u003csub\u003e4\u003c/sub\u003e, CuSO\u003csub\u003e4\u003c/sub\u003e, ZnSO\u003csub\u003e4\u003c/sub\u003e, ZnO, CuO, and NiS. In other words, particularly in relation to device made of 316SNi, it resulted in sulfur absorption. While the enthalpy of formation of nickel oxide (-240.5 kJ/mol) is lower than that of nickel sulfide (-50.68 kJ/mol), XRD and EDX results show that in a device made of 316SNi, the dominant product of the reaction between nickel, oxygen, and sulfur is nickel sulfide. This can be attributed to the activation energy at the relatively low temperature of the exhaust end, which is required for the reaction of the nickel surface with oxygen and sulfur. This activation energy is lower for nickel sulfide (50\u0026ndash;100 kJ/mol for NiS) than for nickel oxide (100\u0026ndash;200 kJ/mol for NiO). Therefore, the formation of nickel sulfide is driven by the production of a kinetic product.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab5\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eThe weight percentages from the EDX results for the soot-deposited Cu, soot-deposited SZinc, and soot-deposited 316SNi.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"11\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c11\" colnum=\"11\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eType of Back Filter/Elements(Wt%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eC\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eO\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eSi\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eS\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eCa\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eFe\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eZn\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003eNi\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c10\"\u003e \u003cp\u003eCu\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c11\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSoot-deposited Cu\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e86.73\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e9.92\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.43\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e1.28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e0.19\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSoot-deposited SZinc\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e87.11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e9.26\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.67\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.47\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.86\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSoot-deposited 316SNi\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e32.83\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e27.63\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e15.51\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e24.03\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e\u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003e3.4 EIS results\u003c/h2\u003e \u003cp\u003eElectrochemical Impedance Spectroscopy (EIS) in a 3.5% (w/w) NaCl solution was used to analyze the soot-deposited Cu/GCE (a), soot-deposited SZinc/GCE (b), and soot-deposited 316SNi/GCE (c). The Nyquist plots recorded after 20 min in a 3.5% (w/w) NaCl solution are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e. The semicircular region was related to Rpo, which represents the pore resistance due to the formation of ionically conducting paths across the soot coating. The Warburg impedance observed in the mid-frequency region is evidence of the effective barrier behavior of the soot film. The electrochemical parameters of the soot/electrolyte system were evaluated using Eissa1 software. We observed excellent agreement between the experimental results and the parameters obtained from the R(Q(RW)) equivalent circuit model for the soot-deposited Cu/GCE (a) and R(C(RW)) for the soot-deposited SZinc/GCE (b) and the soot-deposited 316SNi/GCE (c), where the chi-squared (χ\u0026sup2;) value minimized at 10\u003csup\u003e\u0026minus;\u0026thinsp;4\u003c/sup\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e). The model of the soot/electrolyte system was built using series components. The first component is the bulk solution resistance of the soot and the electrolyte, Rs (R1). The second component is the parallel combination of the constant phase element (CPE) of the soot coating in the equivalent circuit of the soot-deposited Cu/GCE (a), Q, and R2, which represents Rpo. Rpo is the pore resistance, which arises from the formation of ionically conducting paths across the soot coating. The double-layer capacitance (Cdl) was parallel to Rpo in the equivalent circuits of the soot-deposited SZinc/GCE (b) and the soot-deposited 316SNi/GCE (c). Additionally, a series connection to Rpo, represented by W, accounts for the Warburg impedance of the soot film. The Warburg impedance (W) is due to pore formation on the surface of each electrode. The constant phase element (CPE) is introduced in parallel with Rpo in the equivalent circuit of the soot-deposited Cu/GCE (a), corresponding to the pores on the surface of the soot film. Simulation results for the soot film show that this electrical equivalent circuit was successfully applied to the experimental data, explaining the interface between the electrode/soot film and the electrolyte (Table\u0026nbsp;\u003cspan refid=\"Tab6\" class=\"InternalRef\"\u003e6\u003c/span\u003e). Instead of a pure capacitor, a constant phase element (CPE) was introduced in the fitting procedure to achieve a good agreement between the simulated and experimental data (the equivalent circuit of the soot-deposited Cu/GCE (a)). The impedance of CPE is defined as ZCPE\u0026thinsp;=\u0026thinsp;Q\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e \u0026times; (jω)\u003csup\u003e\u0026minus;n\u003c/sup\u003e, where Q represents a combination of properties related to the surface and electroactive species, independent of frequency. The parameter \u0026ldquo;n\u0026rdquo; is related to the slope of log Z versus log f. The value of \u0026ldquo;n\u0026rdquo; ranges from 0 to 1, with values closer to 1 indicating a smoother film surface (Mahmoudian et al., \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). The EIS results show that the electrical resistance of soot deposited on 316SNi is much lower than that of soot deposited on SZinc and copper. Previous reports have shown that soot from engine combustion becomes electrically charged as it passes through an exhaust pipe. If this charge is discharged, soot clusters can form (Ju et al., \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Therefore, based on the EIS results, which confirm the lowest resistance for soot-deposited 316SNi, it can be concluded that the electrical discharge of soot particles in a device made of 316SNi is greater, thereby increasing the probability of soot particle accumulation on its surface. The results of log Z vs. log f, which show the total resistance of the soot-deposited Cu/GCE (a), soot-deposited SZinc/GCE (b), and soot-deposited 316SNi/GCE (c), confirm the inference from the simulation (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e). On the other hand, significant sulfide adsorption and NiS production lead to notable changes in the electron conductivity of the soot deposited on the 316SNi surface. According to previous reports, the electron conductivity of NiS is much higher than that of ZnO and Cu\u003csub\u003e2\u003c/sub\u003eO (electron conductivities of NiS, ZnO, and Cu\u003csub\u003e2\u003c/sub\u003eO are 10\u003csup\u003e4\u003c/sup\u003e S/m, 10\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e to 10\u003csup\u003e\u0026minus;\u0026thinsp;4\u003c/sup\u003e S/m, and 10\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e to 10\u003csup\u003e\u0026minus;\u0026thinsp;4\u003c/sup\u003e S/m, respectively) (Gahtar et al., \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2021\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab6\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 6\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eElectrochemical parameters obtained from the simulation of the EIS results for the soot-deposited Cu/GCE (a), soot-deposited SZinc/GCE (b), and soot-deposited 316SNi/GCE in a 3.5% (w/w) NaCl solution.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eThe type of Back filter\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eR1(Rs)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eCdl\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eRpo\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eW\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eQ (CPE)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003en\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003esoot- deposited Cu /GCE\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e44.26\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1737.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2570.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e3.0817\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;5\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.89\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003esoot- deposited SZinc/ GCE\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e45.966\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.00011479\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e483.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e605.88\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003esoot-deposited 316SNi/GCE\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e43.345\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7.383\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;9\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e191.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e404.12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe thermal conductivity of the substrate can also affect the particle size of the soot agglomerates formed on its surface. Other researchers have reported that particle size is inversely related to thermal conductivity (Karunarathne et al., \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). The thermal conductivities of copper, SZinc, and 316SNi are 390\u0026ndash;400 W/m \u003csup\u003eO\u003c/sup\u003eK, 50\u0026ndash;60 W/m \u003csup\u003eO\u003c/sup\u003eK, and 16\u0026ndash;25 W/m \u003csup\u003eO\u003c/sup\u003eK, respectively. The SEM results show that the size of the agglomerates is inversely related to the thermal conductivity of the device metals.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003e3.5 FTIR characterization\u003c/h2\u003e \u003cp\u003eFTIR characterization was used to identify the organic compounds in the soot deposited on the device. Based on previous reports, the presence of unburned hydrocarbons in soot has been documented (Wang \u0026amp; Chung, \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). On the other hand, due to the lower temperature at the end of the exhaust pipe compared to the beginning of the pipe and the exhaust storage, where temperatures are much higher, the possibility of a new reaction between the particles forming soot on the devices is unlikely. In other words, if any type of bond or functional group is observed in the soot deposited on the devices, it should be interpreted based on previously reported results (Shabnam et al., \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). This is not related to the reaction of soot particles on the surface of the devices. Figure\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e shows the FTIR spectra of the soot deposited on the surfaces of Cu (a), SZinc (b), and 316SNi (c). The peak at 3126.43 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is related to O\u0026ndash;H stretching vibrations, possibly from alcohols or phenols (hydrogen-bonded, broad signal). The existence of C\u0026ndash;H stretching vibrations, likely from alkanes (sp\u0026sup3; hybridized C\u0026ndash;H bonds), was confirmed by the peak at 2921.57 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. A broad peak, possibly indicative of CO\u003csub\u003e2\u003c/sub\u003e contamination common in IR spectra due to atmospheric CO\u003csub\u003e2\u003c/sub\u003e was observed at 2360.58 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. The peak at 1576.32 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e corresponds to C\u0026thinsp;=\u0026thinsp;C stretching in aromatic or conjugated systems (aromatic rings or alkenes). The presence of C\u0026ndash;O bonding, which can be characteristic of ethers, esters, or alcohols, was detected at 1116.01 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e in the FTIR spectrum of the deposited soot on the surface of Cu. As seen in the FTIR spectrum of the deposited soot on the surface of SZinc, the O\u0026ndash;H, C\u0026ndash;H, CO\u003csub\u003e2\u003c/sub\u003e, C\u0026thinsp;=\u0026thinsp;C, and C\u0026ndash;O groups appear with a slight shift, similar to the spectrum of the deposited soot on the surface of Cu. In addition, peaks related to C\u0026ndash;H (symmetric stretching in CH\u003csub\u003e2\u003c/sub\u003e groups, characteristic of aliphatic chains), C\u0026thinsp;=\u0026thinsp;O (stretching vibrations, typical of carbonyl groups such as ketones, aldehydes, or esters), C\u0026ndash;H (bending vibrations, common in aliphatic hydrocarbons or methyl groups), and out-of-plane bending vibrations, possibly from aromatic rings or halogenated compounds, are also observed at 2849.41 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, 1719.76 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, 1457.23 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, and 602.90 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, respectively. All the peaks or functional groups associated with the soot deposited on copper and SZinc are also present in the soot deposited on 316SNi. Therefore, it can be concluded that the type of metal used to make the device at low exhaust end temperatures did not have a significant effect on the type of organic compounds. However, it had a significant effect on the reaction of sulfur and oxygen with the metal used to make the device. Based on the results obtained, it can be concluded that using a 316SNi device leads to increased sulfur absorption, and one of the reasons for the greater mass deposited on the surface of 316SNi could be this factor.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"4 Conclusion","content":"\u003cp\u003eIn this study, hot-dip galvanized steel (SZinc), copper, and Nickel electroplated 316 Stainless steel (316SNi) were used separately to make the back filter. The inside of the back filter was designed so that the exhaust gases would follow a sinusoidal path to increase interaction with the half-plates. This design did not negatively affect engine performance. the ppm value of soot deposited on 316SNi is approximately 5 and 3 times higher than that of the soot deposited on a back filter made of copper and SZinc in the absence and presence of PTFE respectively. Additionally, the amount of sulfide adsorbed on the 316SNi back filter was 10 times higher than on the other two materials. The reasons for this significant difference were explained by the following factors:\u003c/p\u003e \u003cp\u003e \u003col\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eInverse relationship between the thermal conductivity of the alloy or metal and the particle size of the soot adsorbed on the back filter.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eInverse relationship between the electrical resistance of the deposited soot and the amount of soot deposited.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003c/ol\u003e \u003c/p\u003e \u003cp\u003eTo interpret the results, impedance spectroscopy was used to investigate the electrical resistance of the adsorbed soot, and X-ray diffraction (XRD) was used to identify the mineral compounds formed on the surface of the back filter. The lower thermal conductivity of 316SNi compared to the other two materials, the lower electrical resistance of the adsorbed soot on 316SNi, and the formation of nickel sulfide as a kinetic product on the steel surface can be considered some of the significant factors.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgments:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe would like to thank the research and technology council of Farhangian University for financial support through this investigation under post doctorate project No.\u0026nbsp;50000/17375/600.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding:\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThis is not applicable\u0026apos; for that specific section.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026rsquo; Contributions:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eMohammad reza Mahmoudian designed the device, interpreted and write the article, while Zohreh Haghighi Kafash edited, performed characterizations and experiments.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthical Approval:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis is not applicable\u0026apos; for that specific section.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to Publish:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis is not applicable\u0026apos; for that specific section.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to Participate:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis is not applicable\u0026apos; for that specific section.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting Interests:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData Availability Statement:\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThis is not applicable\u0026apos; for that specific section. 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Environ Sci Pollut Res 29:58664\u0026ndash;58674. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/s11356-022-19928-y\u003c/span\u003e\u003cspan address=\"10.1007/s11356-022-19928-y\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"},{"header":"Schemes","content":"\u003cp\u003eScheme 1 is available in the Supplementary Files section\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":true,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"environmental-science-and-pollution-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"espr","sideBox":"Learn more about [Environmental Science and Pollution Research](https://www.springer.com/journal/11356)","snPcode":"11356","submissionUrl":"https://submission.nature.com/new-submission/11356/3","title":"Environmental Science and Pollution Research","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Soot, Deposition, Air pollution, Back filter","lastPublishedDoi":"10.21203/rs.3.rs-6526930/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6526930/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThis study introduces a back filter installed at the end of the exhaust pipes of city buses, examining how the type of metal used in its construction affects the absorption of suspended particles and the reduction of sulfides in diesel engine exhaust gases. The back filter is constructed from three metals: copper, zinc, and nickel. The nickel sample was prepared by electroplated of nickel on the 316 steel surfaces (316SNi), while hot-dip galvanized steel was used as a substitute for zinc (SZinc). Poly tetrafluoroethylene (PTFE) powder was utilized to enhance soot adsorption, sandwiched between two metal plates in each back filter. The results indicated that the amount of soot deposited on the 316SNi filter was approximately five and three times greater than that on the filters made of copper and SZinc in the absence and presence of PTFE powder. Additionally, the sulfide absorption on the 316SNi filter was ten times higher than on the other two types. To interpret these results, impedance spectroscopy was employed to assess the electrical resistance of the absorbed soot, and X-ray diffraction was utilized to identify the mineral compounds formed on the filter's surface. The significant differences observed can be attributed to the lower thermal conductivity of 316SNi compared to the other metals, the reduced electrical resistance of soot adsorbed on 316SNi, and the formation of nickel sulfide as a kinetic product on its surface.\u003c/p\u003e","manuscriptTitle":"Introducing a Back Filter: The Impact of Metal Type on Reducing Particulate Matter and Sulfide Emissions from Diesel Engine Exhaust","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-05-19 15:53:48","doi":"10.21203/rs.3.rs-6526930/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Major Revision","date":"2025-07-16T17:44:41+00:00","index":"","fulltext":""},{"type":"reviewerAgreed","content":"","date":"2025-05-16T07:23:56+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-05-15T12:46:27+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-05-06T04:44:55+00:00","index":"","fulltext":""},{"type":"submitted","content":"Environmental Science and Pollution Research","date":"2025-05-02T02:39:32+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"environmental-science-and-pollution-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"espr","sideBox":"Learn more about [Environmental Science and Pollution Research](https://www.springer.com/journal/11356)","snPcode":"11356","submissionUrl":"https://submission.nature.com/new-submission/11356/3","title":"Environmental Science and Pollution Research","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"9808fb33-ad11-487c-9d1e-f40ef3d957fa","owner":[],"postedDate":"May 19th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-09-15T16:00:57+00:00","versionOfRecord":{"articleIdentity":"rs-6526930","link":"https://doi.org/10.1007/s11356-025-36938-8","journal":{"identity":"environmental-science-and-pollution-research","isVorOnly":false,"title":"Environmental Science and Pollution Research"},"publishedOn":"2025-09-10 15:57:05","publishedOnDateReadable":"September 10th, 2025"},"versionCreatedAt":"2025-05-19 15:53:48","video":"","vorDoi":"10.1007/s11356-025-36938-8","vorDoiUrl":"https://doi.org/10.1007/s11356-025-36938-8","workflowStages":[]},"version":"v1","identity":"rs-6526930","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6526930","identity":"rs-6526930","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}