Chemical Activation of Castor Stalk-Derived Porous Carbon for Highly Efficient CO 2 Adsorption in Sustainable Carbon Capture Applications

Chemical Activation of Castor Stalk-Derived Porous Carbon for Highly Efficient CO 2 Adsorption in Sustainable Carbon Capture Applications | 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 Chemical Activation of Castor Stalk-Derived Porous Carbon for Highly Efficient CO 2 Adsorption in Sustainable Carbon Capture Applications Panchanan Pramanik, Renu Gupta, Ajay Bansal This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5879347/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Greenhouse gas emissions have become a pressing concern in recent times, with CO 2 emerging as the primary culprit behind global warming, rising sea levels, and disruptions to ecosystems. Of all the greenhouse gases, CO 2 's impact on global warming stands out as the most significant. To address this issue, activated carbon (AC) has gained prominence as an effective CO 2 adsorption agent, owing to its porous structure, expansive surface area, cost-effectiveness, and environmentally friendly properties. In this current research, activated carbon was produced from castor stalk biomass through a single-stage chemical activation process known as pyrolysis. This method is lauded for its cost-efficiency, simplicity, and minimal environmental impact. Potassium hydroxide (KOH) and aluminum sulfate (ALUM) were employed as the activating agents. Subsequently, the synthesized activated carbon was subjected to Methylene Blue adsorption testing to evaluate its CO 2 adsorption capacity, among other potential applications. The characterization of the activated carbon derived from castor stalk involved a series of techniques, including CHNS analysis, proximate analysis, SEM, FTIR, XRD, and BET surface area analysis. These analyses unveiled the impressive attributes of the castor stalk-derived activated carbon, featuring an exceptionally high surface area of 1687 m 2 /g, a substantial pore volume of 1.015 cm 3 /g, and a pore diameter of 2.71 nm. Furthermore, the Methylene Blue adsorption test yielded a remarkable value of 447.72 mg/g with 89.5% adsorption efficiency. High CO 2 adsorption capacity (2.46 mmol/g) was observed over castor stalk-derived activated carbon. The comparative study shows higher CO 2 adsorption capacity in comparison to activated carbon derived from various biomasses using KOH as the activating agent. So, the present study shows activated carbon derived from Castor stalk using KOH and Alum as activating agent can be a promising method for CO 2 adsorption. Biomass Castor stalk Activated carbon Pyrolysis Methylene blue CO2 adsorption Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 1. Introduction Over the past few decades, there has been a 7% increase in the concentration of CO 2 in the Earth's atmosphere. This rise can be primarily attributed to the rapid industrialization and improvements in living standards, which have led to a substantial increase in the release of greenhouse gases like CO 2 and CH 4 into the atmosphere [1]. The emissions of these gases contribute to global warming, higher sea levels, and environmental pollution, ultimately disrupting the delicate balance of ecosystems. Among the various greenhouse gases, such as CO 2 , CH 4 , HFCs, and PFCs, CO 2 stands out as having the most significant impact on global warming [2]. Despite its association with environmental issues, CO 2 is noteworthy for being non-toxic, cost-effective, and capable of being utilized in the production of various organic chemicals, including glucose, starch, and CaCO 3 , which offer substantial commercial benefits. Considerable efforts are underway to develop technologies for capturing CO 2 to mitigate the greenhouse effect. Agricultural residues and waste biomass are gaining increasing attention due to their affordability, widespread availability, and environmentally friendly characteristics, and they are being explored for conversion and utilization in the production of activated carbon [3]. Typically, activated carbon is derived from biomass through thermochemical conversion processes like pyrolysis. Activated carbon is characterized by its high surface area and porosity, making it a valuable material. Biomass or biochar can serve as the starting materials for the synthesis of activated carbon. Various types of biomass, including rice husk, walnut shells, almond shells, bamboo-based materials, coconut shells, empty fruit bunches of oil palm, peanut shell char, fox nut (Euryale ferox) shells, African palm shells, and more, have been employed in the production of activated carbon [4], [5], [6], [7], [8], [9], [10], [11], [12]. Various studies have been reported by the researchers to capture CO 2 using different technologies such as carbonization and pyrolysis [13]. Activated carbon is a well-known and famous technology to capture CO 2 due to its higher adsorption capacity and can be synthesised from biomass. India has a lot of waste biomass in various forms, such as forest residue, agriculture, kitchen waste, etc. Castor is a plant that is mainly used to produce castor oil. India is the largest castor producing country in the world with more than 85%, followed by China with about 7% and Brazil with 5%. Among the different states of India, Gujarat produces 78%, followed by Rajasthan (18%), Andhra Pradesh (2%), Karnataka (1%), and the remaining state (1%). Thus, for sustainable agricultural production, castor is a very important crop in the Saurashtra region of Gujarat (India). At present, the castor stalks are either burned on the field or ploughed into the soil. The ploughed in stalks reduce the erosion resistance of the soil. Castor stalks do not contain much nutritional value and are quite woody in nature [14]. Therefore, it can be a pathbreaker for the production of activated carbon. In the present study, a novel technique has been used to synthesize activated carbon from the stalks of castor as biomass. The activation process has been carried out by taking powdered castor stalks impregnated with reagents KOH with Alum in the crucible completely covered with a lid in a muffle furnace and liquid nitrogen was also used for creating an inert atmosphere inside the crucible. The activated carbon thus formed has resulted in increased porosity and high surface area. The prepared biomass was characterized for proximate and ultimate analysis, to study the ash, fixed carbon, and volatile matter content, and to find the composition of C, H, S, and O elements. Also, the synthesized activated carbon was analyzed for proximate and ultimate analysis, BET, FTIR, XRD, and SEM analysis to analyze the surface area, functional groups, crystalline nature, and structure of the synthesized activated carbon. 2. Experiment 2.1 Materials Castor stalk was taken from the campus of the NITJ, Punjab, India. As an activating reagent, potassium hydroxide (KOH) and alum (KAl(SO 4 ) 2 .12H 2 O) analytical grade were used. Distilled water and hydrochloric acid (HCl) were used to neutralize the product formed. 2.1 Preparation of Activated Carbon Activated carbon was synthesized using KOH and alum as activating agents in the ratio 1:1.5:0.1 (CAS: KOH: Alum). Approximately 50 g of dried castor stalk (CAS) fine powder was taken and mixed with 75g of KOH and 5g of alum. After mixing the sample, distilled water was added, and the slurry was impregnated for 24 hours at ambient temperature using a magnetic stirrer at 350–400 RPM. After 24 hours of continuous stirring, the slurries were placed in an oven. The sample was dried at 120°C for 4 hours until it became paste-like. After drying, the sample was activated in a muffle furnace at (700 ± 10) °C for 60 minutes in a crucible dipped with liquid nitrogen and completely sealed with aluminum foil to create an inert atmosphere throughout the activation process. After activation, the sample was naturally cooled for 4 hours. The sample was extracted, and then it was stirred for half an hour at 350 rpm. Then the sample was water washed till its pH reached to neutral value. After filtering, the sample was dried in an oven at 120°C for 3 hours and then dissolved in 10% diluted hydrochloric acid. The activated sample was allowed to settle for about 3–4 hours until all ash content reached the upper layer. The upper layer containing ash was removed, and the sample was washed with deionized water to remove organic impurities and subsequently with NaOH to attain neutral condition for the filtered-out solution. Finally, the activated sample was taken in a petri dish and dried at 120°C for 4 hours. All moisture and water contents were properly dried, and the collected sample is the desired activated carbon. Thereafter, the activated carbon was ground, and the weight obtained was noted for yield percentage. The method for preparation of activated carbon from castor stalk is presented in Fig. 1 . Owing to the unavailability of conventional pyrolizers, like tubular furnaces, we carry out the process in a muffle furnace, making sure the environment is inert. At lieu of nitrogen gas, liquid nitrogen is also used because it is simple to obtain at the institute lab and works well for the experiment. Nitrogen gas can also be used as an alternative to liquid nitrogen. A general overview of activated carbon production, characterization and its applications are shown in Fig. 1 a. 2.2 Characterization 2.2.1 Proximate & Ultimate Analysis Castor stalk was dried in sunlight for 20–25 days. The unprocessed material underwent crushing and screening to achieve a consistent size smaller than 2.0 mm and thereafter proximate and ultimate analysis were carried out. A proximate analysis was conducted to ascertain the levels of moisture content, ash content, volatile matter, and fixed carbon. This was achieved by employing crucibles, both with and without lids, in a heating oven set to temperatures between 27ºC and 950ºC. The moisture and total ash contents were assessed using the established proximate analysis protocol. The contents of C, H, N, and S of the castor stalk (CAS) and Activated carbon (AC) were measured by the CHNS Analyzer (Thermo Fisher company) using K factors. 2.2.2 Pore Volume, Surface area BET Analysis (BELSORP-maxII (S/N: 175, Version 2.0.1.1) was carried out to examine surface area ( \(\:{S}_{BET})\) , total Pore volume ( \(\:{V}_{t}),\) macro pore volumes ( \(\:{V}_{mic})\:\) and micro pore surface ( \(\:{S}_{mic})\:\) of the synthesized activated carbon using the t-plot method. \(\:\text{P}\text{o}\text{r}\text{e}\:\text{v}\text{o}\text{l}\text{u}\text{m}\text{e}\:\left({V}_{t}\right)\) was estimated from nitrogen adsorption at a relative pressure of 0.98. Pore Size Distribution (PSD) was determined using the BJH model. The sample was completely dried and then degassed at 150ºC for 4 hours. After that, using liquid nitrogen, the adsorption and desorption curves were obtained. 2.2.3 Surface Morphology Surface morphology of activated carbon was identified by using Scanning Electron Microscopy using SIGMA 500VP. To study the morphology of Activated Carbon (AC) was dried for 24 hrs. at 110 \(\:^\circ\:\) C. Thereafter the sample was sonicated and then it was dissolved in ethanol. 2.2.4 Functional Group Analysis Fourier transform infrared spectroscopy was used to analyze the functional groups present in activated carbon and castor stalk in the range 4000 − 400 cm − 1 by using a Spectrophotometer (Agilent Carry 630). 2.2.5 X-Ray Diffraction X-ray diffraction was used to identify the presence of any crystalline structure in different ranges of 2θ for activated carbon and castor stalk. The intensity counts were noted for activated carbon at θ = 18.3°and for castor stalk biomass its intensity counts peak obtained at θ = 22.45°. PAN analytical Empyrean was used for this analysis. 2.2.6 Adsorptive properties Adsorptive properties of AC were performed with MB as adsorbate. The calibration curve was plotted using a UV spectrophotometer. Various concentrations of methylene blue ranging from 150–750 ppm using a stock solution of 1000 ppm. The absorbance was carried out at 668 nm wavelength using a double beam UV- Vis Spectrophotometer (Shimadzu). The relation between adsorption and methylene blue concentration is represented in Eq. 1 Ads = 0.0022C + 0.5952 (R 2 = 0.999) [1] The adsorptive capacity of MB was analyzed using the batch equilibrium technique. A volume of 100 ml from a stock solution containing 1000 mg/L of MB was diluted to a concentration of 500 mg/L. This diluted solution was then transferred into a 250 ml flask, to which 100 mg of AC sample was added. The resulting mixture was placed inside an incubator set at 25 o C, where it was stirred for 6 hours to achieve equilibrium. Subsequently, the sample underwent centrifugation at 4000 rpm for 10 minutes. Finally, the activated carbon settled at the bottom, and the remaining concentration of MB was extracted using a pipette. This extracted sample was then subjected to analysis utilizing a UV spectrophotometer. The quantity of MB adsorbed at equilibrium conditions, denoted as q e (mg/g), was determined as follows: \(\:{\text{q}}_{\text{e}}=\frac{{\text{C}}_{\text{O}}-{\text{C}}_{\text{e}}}{\text{M}}\text{*}\text{V}\) [2] \(\:{\text{C}}_{0}\:\) represents the initial concentration of the MB solution, while C e represents the final concentration. M stands for the weight of the AC used, and V represents the volume of the MB solution. 3. Results and Discussion 3.1 Proximate Analysis 1 g of raw biomass Castor Stalk after grinding and messing was taken in a crucible and analyzed at different temperatures for the measurement of moisture content, volatile material, ash content, and fixed carbon. For moisture determination, a 1 g castor stalk sample was heated at 104–110 ºC without covering the lid of the crucible in a drying oven for 1 hour. Then, for volatile matter, 1 g of sample is placed in a crucible properly covered with a lid and heated at 50ºC/min to 950 ± 20ºC and holding at this temperature for 7 min. For ash determination, the sample was heated at a rate of 700 to 750 ºC for 2 hours, and further, the sample was heated so that the final temperature of the furnace rose to 900 to 950 ºC by the end of the second hour, and then finally fixed carbon was determined by subtracting the moisture content, ash content, and volatile matter from the total percentage [ASTM D5142-04, 2010]. The given table suggests the value of carbon content and other constituents present in biomass. The proximate analysis for the castor stalk and activated carbon obtained from the castor stalk is presented in Table 1 . Table 1 shows 3.3 times increase in fixed carbon content in activated carbon in comparison to raw biomass. Table 1 Proximate Analysis of CAS and AC S. No. Sample Code Moisture (%) Ash (%) Volatile matter (%) Fixed carbon (%) 1. CAS 10.02 14.62 57.15 18.21 2. AC 6.60 11.50 21.42 60.48 3.2 Ultimate Analysis CHNS analysis of raw castor stalk and prepared activated carbon was done to measure the ultimate analysis, i.e., contents of carbon, hydrogen, nitrogen, sulfur, and oxygen. The ultimate analysis of raw castor stalk and prepared activated carbon is presented in Table 2 . Table 2 shows that the material contains 38.96% carbon, 3.55% hydrogen, 1.01% nitrogen, and 56.48% oxygen. After activation, the amount of carbon, hydrogen, and nitrogen in the activated carbon (AC) is found to be 76.49%, 7.83%, and 0.43%. respectively. The carbon content in the activated carbon was almost doubled. There was a 4.28% rise in hydrogen content and a 0.58% decrease in nitrogen content in the obtained. Table 2 % Values of CHNS Observed in raw CAS (Castor stalk) and Activated Carbon (AC) S. No. Sample Code %C %H %N %S % O 1. CAS 38.96 3.55 1.01 0.00 56.48 2. AC 76.49 7.83 0.43 0.00 15.25 3.3% Yield The activated carbon was synthesized using powdered castor stalk, KOH, and Alum in the ratio (1:1.5:0.1). Alum was added to enhance the porosity of the activated carbon. The initial weight of the castor stalk powder was noted. The mixture of powdered stalk, KOH and Alum was impregnated for 24 hours under continuous stirring. Then the sample was activated at 550 ºC − 900 ºC at a step of 50 o C for 60 minutes, taking the same impregnation ratio. Then the sample was filtered out to remove KOH and Alum by adding 10% dilute hydrochloric acid, which helps to neutralize its pH to 7. Finally, the sample was dried in the oven for 4 hours at 110 ºC. The sample was weighed again, and the % yield was calculated using Eq. (3) \(\:\text{%}\:\text{Y}\text{i}\text{e}\text{l}\text{d}=\:\frac{\text{W}\text{e}\text{i}\text{g}\text{h}\text{t}\:\text{o}\text{f}\:\text{P}\text{r}\text{o}\text{d}\text{u}\text{c}\text{t}}{\text{W}\text{i}\text{e}\text{g}\text{h}\text{t}\:\text{o}\text{f}\:\text{s}\text{a}\text{m}\text{p}\text{l}\text{e}\:\text{t}\text{a}\text{k}\text{e}\text{n}}\text{*}100\) [3] where weight of product was the weight of activated carbon obtained after the complete removal of moisture and weight of the sample taken was the initial weight of raw castor stalk taken for the experiment. The observed trend in Fig. 2 a shows that with an increase in the temperature of activation during pyrolysis, the yield percentage of the activated carbon produced decreased. Further, the activated carbon thus produced at various temperatures was analyzed for methylene blue adsorption studies and are presented in Fig. 2 b. It is observed that with an increase in temperature from 550 o C to 700 o C the adsorption of methylene blue increased and thereafter with an increase in temperature from 750 o C to 900 o C it decreased. This may be due to the fact that at low temperatures the ash content or volatile matter is present in the activated carbon which has increased the yield % of activated carbon and showed lower adsorption. So, for the current study activated carbon obtained at 700ºC with 8.5% yield was used for further characterization and adsorption studies of methylene blue and CO 2 . 3.4 BET analysis Nitrogen adsorption isotherm at -196°C was used to find the specific surface area and pore structure of activated carbon produced from castor stalk (Fig. 3 ) and the results are presented in Table 3 . Table 3 BET analysis of AC S. No. Sample Code Surface Area (m 2 /g) Pore Volume (cm 3 /g) Pore Diameter (nm) 1. AC 1687 1.0150 2.7095 Table 4 Comparison of BET surface area of Porous Carbon derived from various agro-residues. Precursor Activating agent Impregnation ratio Activation temperature (K) S BET , m 2 /g References Coconut shell KOH 1:3 873 1172 [15] Garlic peel KOH 1:2 1073 1262 [16] Rice Husk KOH 1:3 873 755 [17] Arundo donaxa KOH 1:2 873 1122 [18] Rotten strawberries KOH 1:2 923 1117 [19] Chestnut shell NaNH 2 1:1 773 1416 [20] Sugarcane bagasse KOH 1:2 873 1113 [21] Cotton boll KOH 1:2 973 1381 [22] Tea seed shell KOH 1:4 973 1503 [23] Castor Stalk KOH + Alum 1:1.5:0.1 973 1687 Present study The observed adsorption hysteresis loop was classified as type 4. The pore type was observed to be the inkbottle type, which was associated with the desorption process [24]. The surface area of the synthesized activated carbon is found to be 1687 m 2 /g, with a pore volume of 1.0150 cm 3 /g and a pore diameter of 2.7095 nm. A comparative study of surface area of AC produced from various biomasses is presented in Table 4 which highlights higher surface area for AC synthesized in the present study. It may be due to the novel synthesis technique adopted where the alum has been used in addition to KOH as the activating agent and also the inert atmosphere was created using liquid nitrogen. High surface area has resulted in enhanced the adsorption capacity. 3.5 Analysis of Functional groups: FTIR spectra for both castor stalk and activated carbon is presented in Fig. 4 . In the castor stalk spectrum, we observe peaks at 1027.45 cm − 1 and 1239.11 cm − 1 , which can be attributed to the stretching of C-O-C bonds in ethers. Additionally, peaks at 1736.40 cm − 1 are associated with the stretching vibrations of C = O bonds within aromatic rings, and a C-N stretching vibration is evident at 2367.26 cm − 1 .C-N stretching at wave number 2367.26 cm − 1 was also observed in activated carbon. After activation, the castor stalk AC was ascribed to C-H stretching at wave number 22913.87 cm − 1 . The band at 3341.29 cm − 1 is attributed to NH stretching. And finally, bands at 3638.27 cm − 1 represent O-H stretching in hydroxyl functional groups, which was presented in the raw material castor stalk as well as in the activated carbon obtained after activation. The details of functional groups at their respective wavenumbers are provided in Table 5 . Table 5 FTIR Result of raw Castor Stalk (CAS) and Activated Carbon (AC). Wave number (cm − 1) 1027.45, 1239.11 1736.40 2367.26 2913.87 3341.29 ≥ 3638.71 CAS C-O C = O C-N C-H N-H O-H AC ---- ---- C-N ---- ---- O-H 3.6 X-Ray Diffraction Analysis XRD analysis results for castor stalk and activated carbon is shown in Fig. 5 . XRD method is usually used to identify materials crystallographic features. The difference in structures of raw biomass castor stalk and porous activated carbon can be clearly revealed in Fig. 5 . The intensity counts are observed to check the presence of Potassium (K), Aluminum (Al) and Hydride (H) in the amorphous activated carbon as Alum and KOH are used as activating reagent during preparation of porous activated carbon. Because of the amorphous character the peaks were not as clearly identified as it was being observed for crystalline samples. The activated carbon does not show much intensity count peaks throughout 10 o to 80 o angle for 2θ which may be due to the amorphous nature of the activated carbon synthesized. A strong and broad diffraction peak count intensity were detected for activated carbon (AC) at 2θ = 14.2° reveals amorphous structure of activated carbon [25]. Similarly, at 2θ = 22.4° for castor stalk powder 4500 + counts intense peak is observed which may be due to presence of some metal oxide having some crystalline structure [26]. 3.7 Surface Morphology of Activated Carbon SEM images of the microstructures of the AC reveals the fluffy and porous structure of the synthesized activated carbon (Fig. 6 ). Further the external surface of the AC seems to be full of cavities. At 10 µm, 3 KX and 3 µm, 7 KX, magnification, the spherical pores were observed. AC is a porous material having large number of mesopores and micro pores of different dimensions. KOH and Alum were used as reagent during activation leads to the formation of cavities and pores. Further washing with hydrochloric acid might have resulted in the formation of micro pores within the carbon matrix. 3.8 Methylene Blue (MB) Analysis 100 mg of AC was added in 100 ml of 500 ppm of Methylene blue. The adsorption studies were carried out for 6 hours under continuous stirring After 6 hours of batch adsorption, the absorbance value of activated carbon for methylene blue was analyzed using UV spectrophotometer at 668 nm wavelength. The observed absorbance of the final solution was observed to be 0.7102 which shows 52.27% adsorption. Further the methylene blue adsorption capacity was calculated using Eq. [2] and was observed to be 447.72 mg/g. Table 6 Comparison of MB adsorption (mg/g) of AC synthesized from different biomass. Precursor Activating agent Surface area (m 2 /g) Methylene blue value (mg/g) References Tea waste H 3 PO 4 2054.5 402.25 [27] Palm shells ZnCl 2 731 163.00 [28] Sorghum residues ZnCl 2 1817 386.10 [29] Oil palm fiber Microwave radiation 707.7 312.50 [30] Date pits FeCl 3 780 259.20 [31] Cotton stalk ZnCl 2 + microwave radiation 794 193.50 [32] Castor Stalk KOH + Alum 1687 447.72 Present study Table 6 shows the compression of methylene blue value obtained by activated carbon produced from different biomass and also the activated carbon produced in this research work. It was observed that the value of methylene blue obtained from castor stalk was much higher than the values obtained from all other biomass as compared. Thus, we can say because of chemical activation of castor stalk with KOH and Alum the activated carbon synthesized has much higher adsorption capacity than it was produced by other activating reagents. 3.10 Adsorption of CO 2 on obtained Activated Carbon CO 2 adsorption isotherms were assessed employing a static volumetric system known as ASAP 2020. The samples underwent in-situ activation by heating them to 200°C, gradually increasing the temperature at a rate of 5°C per minute under vacuum conditions (0.005 mm Hg) overnight, utilizing the degassing system integrated into the ASAP 2020 equipment. To maintain the desired adsorption temperature, water from a constant temperature water bath was circulated [33]. The adsorbate gas was introduced into the setup in specific volumes required to attain a predetermined range of pressures, spanning from 1 to 760 mmHg. Three pressure transducers, each with a different range of 1, 10, and 1000 mmHg, were employed to measure the pressures accurately. To ascertain equilibrium for each measurement point, a minimum equilibrium interval of 20 seconds was enforced, with a maximum relative tolerance of 5% relative to the target pressure and an absolute tolerance of 5 mmHg. The adsorption capacity, denoted as millimoles of gas adsorbed per gram of adsorbent, was derived from the adsorption isotherms [34] (Fig. 7 ). Notably, the adsorption capacity for CO 2 is observed to be 2.46 mmol/g at a temperature of 298.15K and a pressure of 1 atm. Comparison of CO 2 adsorption capacity of activated carbon synthesized from various biomass is presented in Table 7 which shows a remarkable high adsorption in comparison to reported adsorbents. This achievement is exceptional, especially considering that the activated carbon was produced using a novel pyrolysis process conducted in muffle furnaces, with the additional use of liquid nitrogen to create an inert atmosphere during the chemical activation process. Table 7 Comparison of CO 2 adsorption capacity of activated carbon synthesized from various biomass. Precursor Activating agent Impregnation ratio Activation temp (K) CO 2 Adsorption (mmol/g) at 25 O C References Palm Kernel Shell Physical Activation -- 1123 2.13 [35] Olive Stones Physical Activation -- 1073 1.98 [36] Coconut shell KOH 1:2 1073 1.80 [37] Sargassum KOH 1:1 1073 1.05 [38] Enteromorpha KOH 1:1 1073 0.52 [38] Coffee Grounds KOH 1:2 873 3.00 [39] Wheat flour KOH 1:5 1073 2.28 [40] Castor Stalk KOH + Alum 1:1.5:0.1 973 2.46 Present study 4. Conclusion Porous activated carbon obtained from castor stalk is cost effective due to its abundance availability and low cost. Pyrolysis process using muffle furnace is also termed to be as clean and new methodology with very low cost of production. To manage various agro-residues development of porous activated carbon can be considered to be one of the most predominating pathways for CO 2 capture. Single step activation of castor stalk biomass using amalgamation of Alum and KOH as activating agent at a temperature of 700 ± 10 o C and 60 min holding time was considered. Yield %, calorific value of biomass, (FTIR) for different functional group in raw biomass and activated carbon, (XRD) for crystalline and amorphous nature, (SEM) for Surface morphology, (CHNS) for ultimate analysis, methylene blue value and Proximate analysis were the various characterization technique used. Beside 447.72 mg/g methylene blue value, a very high surface area 1687 m 2 /g with pore volume of 1.0150 cm 3 /g and a pore diameter of 2.7095 nm was observed. CO 2 adsorption isotherm data have been obtained from a static volumetric system (ASAP 2020). The remarkable aspect of this accomplishment lies in the fact that, under a temperature of 298.15K and a pressure of 1 atm, the CO 2 adsorption capacity reached an impressive 2.46 mmol/g. What makes this even more noteworthy is that the activated carbon was manufactured using an innovative pyrolysis method within muffle furnaces, and an additional step involved the utilization of liquid nitrogen to establish an inert atmosphere during the chemical activation procedure. Declarations Ethical approval Not applicable. Consent to participate All authors gave explicit consent to participate. Consent to publish All authors gave explicit consent to submit. Funding The authors declare that no funds, grants, or other support were received during the preparation of this manuscript. Authors contribution Panchanan Pramanik: Resources, Methodology, Investigation, Data Curation, Writing-Original draft, Renu Gupta: Analyzing characterization, Editing draft, Ajay Bansal: Conceptualization, Supervision, Editing draft. Competing Interests All authors involved in this manuscript have approved it and declare that they have no conflict of interests. Availability of data and materials Not required Acknowledgment: The authors gratefully acknowledge Dr. B.R Ambedkar National Institute of Technology Jalandhar for providing all research facilities. The authors also acknowledge IIT Delhi, SAIF-IIT Bombay, CSMCRI Bhavnagar for providing characterization facilities. References J. D. Figueroa, T. Fout, S. Plasynski, H. McIlvried, and R. D. Srivastava, “Advances in CO2 capture technology-The U.S. Department of Energy’s Carbon Sequestration Program,” Int. J. Greenh. Gas Control , vol. 2, no. 1, pp. 9–20, 2008, doi: 10.1016/S1750-5836(07)00094-1. H. 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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-5879347","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":405636097,"identity":"65bd4eb7-fabc-4591-9a6d-86b805ac29f3","order_by":0,"name":"Panchanan Pramanik","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA40lEQVRIie3RvQrCMBDA8TsOdKpdDxx8hYqrH69SKejqJB3jki6Ca6Uv4SOkdHAJnSs4KIKuXV3EqKPS6uaQ/xjy4/IBYLP9Ywx4LMPbsNNcCAWNxxKKOkI91iroLlOh1JekwY5UKAof4EVqcpPowKz3hOvTIivn0HEFyUPlkL3yvVl4bjXbY3OwHLqxwsirIh77ymdNhIkhqQTcAEquJmanIwnFLn2S0RckQOHIzFwfn2RcS7iYELGemEc243TOQZzVEDeeXq5l2DdfuT2V4bw/WEXRuZK8TQWgX/bbbDab7WN3in5RtlxL+10AAAAASUVORK5CYII=","orcid":"","institution":"Dr. B R Ambedkar National Institute of Technology","correspondingAuthor":true,"prefix":"","firstName":"Panchanan","middleName":"","lastName":"Pramanik","suffix":""},{"id":405636098,"identity":"e3e80fab-c2ae-44f8-b7d5-5b135e44d8a7","order_by":1,"name":"Renu Gupta","email":"","orcid":"","institution":"Dr. B R Ambedkar National Institute of 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Activated Carbon from Castor stalk and its applications.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-5879347/v1/23bd16f5e2b7310653379248.png"},{"id":74666006,"identity":"9df09ab5-6f3a-42ed-9cac-5ef725cba235","added_by":"auto","created_at":"2025-01-24 13:23:03","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":106002,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFig.1a: A general overview of activated carbon production, characterization and its applications.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"1a.png","url":"https://assets-eu.researchsquare.com/files/rs-5879347/v1/3d59b17d780465000241efd1.png"},{"id":74665446,"identity":"604d1749-a5e7-45c2-9260-4584a1594f82","added_by":"auto","created_at":"2025-01-24 13:15:03","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":90547,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFig. 2a: Plot of Yield of Activated carbon vs Temperature (ºC) Fig 2b: Plot of adsorption of Activated carbon on methylene blue vs Temperature (ºC\u003c/strong\u003e)\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-5879347/v1/d2603cead56a67968de74254.png"},{"id":74665447,"identity":"d7f9c497-e775-4d61-8c40-1214efa5b01a","added_by":"auto","created_at":"2025-01-24 13:15:03","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":32094,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFig 3: BET surface isotherm of AC\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-5879347/v1/b7ba1e9fd6a381ad2cd61da7.png"},{"id":74665453,"identity":"eaf38f45-6ee6-4bd3-b114-1a218e679a6e","added_by":"auto","created_at":"2025-01-24 13:15:03","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":52487,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFig. 4: FTIR spectra of CAS and AC.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-5879347/v1/8953f6e01d81a3d3be3cee7d.png"},{"id":74665465,"identity":"7b00b889-1b5d-4f33-8517-9e1d4bf1cf31","added_by":"auto","created_at":"2025-01-24 13:15:04","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":59077,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFig. 5: X-Ray Diffraction of raw castor stalk (CAS) and Activated carbon (AC).\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-5879347/v1/8fba26085337e80087365510.png"},{"id":74665470,"identity":"c3294e1a-df98-4d44-b95d-7d1fd8b5cda0","added_by":"auto","created_at":"2025-01-24 13:15:04","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":244589,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFig. 6: SEM micrographs (a) AC at10μm, (b) AC at 3μm.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-5879347/v1/267ca225cf0d52fa6fa3ba54.png"},{"id":74665455,"identity":"6f880498-1ae5-47a8-b20e-1e01c75a44d7","added_by":"auto","created_at":"2025-01-24 13:15:03","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":27068,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFig. 7: CO\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e Adsorption curve of Castor stalk activated carbon (AC).\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-5879347/v1/752d6d2d8ce571c81552d9f9.png"},{"id":74932862,"identity":"8bfa80b2-cd1c-4a7b-8d4d-b26eb60aaa5f","added_by":"auto","created_at":"2025-01-28 12:47:20","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2185846,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5879347/v1/e9640666-1d37-4d40-964d-cfcd3caff956.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Chemical Activation of Castor Stalk-Derived Porous Carbon for Highly Efficient CO 2 Adsorption in Sustainable Carbon Capture Applications","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eOver the past few decades, there has been a 7% increase in the concentration of CO\u003csub\u003e2\u003c/sub\u003e in the Earth's atmosphere. This rise can be primarily attributed to the rapid industrialization and improvements in living standards, which have led to a substantial increase in the release of greenhouse gases like CO\u003csub\u003e2\u003c/sub\u003e and CH\u003csub\u003e4\u003c/sub\u003e into the atmosphere [1]. The emissions of these gases contribute to global warming, higher sea levels, and environmental pollution, ultimately disrupting the delicate balance of ecosystems. Among the various greenhouse gases, such as CO\u003csub\u003e2\u003c/sub\u003e, CH\u003csub\u003e4\u003c/sub\u003e, HFCs, and PFCs, CO\u003csub\u003e2\u003c/sub\u003e stands out as having the most significant impact on global warming [2]. Despite its association with environmental issues, CO\u003csub\u003e2\u003c/sub\u003e is noteworthy for being non-toxic, cost-effective, and capable of being utilized in the production of various organic chemicals, including glucose, starch, and CaCO\u003csub\u003e3\u003c/sub\u003e, which offer substantial commercial benefits. Considerable efforts are underway to develop technologies for capturing CO\u003csub\u003e2\u003c/sub\u003e to mitigate the greenhouse effect. Agricultural residues and waste biomass are gaining increasing attention due to their affordability, widespread availability, and environmentally friendly characteristics, and they are being explored for conversion and utilization in the production of activated carbon [3]. Typically, activated carbon is derived from biomass through thermochemical conversion processes like pyrolysis. Activated carbon is characterized by its high surface area and porosity, making it a valuable material. Biomass or biochar can serve as the starting materials for the synthesis of activated carbon. Various types of biomass, including rice husk, walnut shells, almond shells, bamboo-based materials, coconut shells, empty fruit bunches of oil palm, peanut shell char, fox nut (Euryale ferox) shells, African palm shells, and more, have been employed in the production of activated carbon [4], [5], [6], [7], [8], [9], [10], [11], [12].\u003c/p\u003e \u003cp\u003eVarious studies have been reported by the researchers to capture CO\u003csub\u003e2\u003c/sub\u003e using different technologies such as carbonization and pyrolysis [13]. Activated carbon is a well-known and famous technology to capture CO\u003csub\u003e2\u003c/sub\u003e due to its higher adsorption capacity and can be synthesised from biomass. India has a lot of waste biomass in various forms, such as forest residue, agriculture, kitchen waste, etc. Castor is a plant that is mainly used to produce castor oil. India is the largest castor producing country in the world with more than 85%, followed by China with about 7% and Brazil with 5%. Among the different states of India, Gujarat produces 78%, followed by Rajasthan (18%), Andhra Pradesh (2%), Karnataka (1%), and the remaining state (1%). Thus, for sustainable agricultural production, castor is a very important crop in the Saurashtra region of Gujarat (India). At present, the castor stalks are either burned on the field or ploughed into the soil. The ploughed in stalks reduce the erosion resistance of the soil. Castor stalks do not contain much nutritional value and are quite woody in nature [14]. Therefore, it can be a pathbreaker for the production of activated carbon.\u003c/p\u003e \u003cp\u003eIn the present study, a novel technique has been used to synthesize activated carbon from the stalks of castor as biomass. The activation process has been carried out by taking powdered castor stalks impregnated with reagents KOH with Alum in the crucible completely covered with a lid in a muffle furnace and liquid nitrogen was also used for creating an inert atmosphere inside the crucible. The activated carbon thus formed has resulted in increased porosity and high surface area. The prepared biomass was characterized for proximate and ultimate analysis, to study the ash, fixed carbon, and volatile matter content, and to find the composition of C, H, S, and O elements. Also, the synthesized activated carbon was analyzed for proximate and ultimate analysis, BET, FTIR, XRD, and SEM analysis to analyze the surface area, functional groups, crystalline nature, and structure of the synthesized activated carbon.\u003c/p\u003e"},{"header":"2. Experiment","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Materials\u003c/h2\u003e \u003cp\u003eCastor stalk was taken from the campus of the NITJ, Punjab, India. As an activating reagent, potassium hydroxide (KOH) and alum (KAl(SO\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e.12H\u003csub\u003e2\u003c/sub\u003eO) analytical grade were used. Distilled water and hydrochloric acid (HCl) were used to neutralize the product formed.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Preparation of Activated Carbon\u003c/h2\u003e \u003cp\u003eActivated carbon was synthesized using KOH and alum as activating agents in the ratio 1:1.5:0.1 (CAS: KOH: Alum). Approximately 50 g of dried castor stalk (CAS) fine powder was taken and mixed with 75g of KOH and 5g of alum. After mixing the sample, distilled water was added, and the slurry was impregnated for 24 hours at ambient temperature using a magnetic stirrer at 350\u0026ndash;400 RPM. After 24 hours of continuous stirring, the slurries were placed in an oven. The sample was dried at 120\u0026deg;C for 4 hours until it became paste-like. After drying, the sample was activated in a muffle furnace at (700\u0026thinsp;\u0026plusmn;\u0026thinsp;10) \u0026deg;C for 60 minutes in a crucible dipped with liquid nitrogen and completely sealed with aluminum foil to create an inert atmosphere throughout the activation process. After activation, the sample was naturally cooled for 4 hours. The sample was extracted, and then it was stirred for half an hour at 350 rpm. Then the sample was water washed till its pH reached to neutral value. After filtering, the sample was dried in an oven at 120\u0026deg;C for 3 hours and then dissolved in 10% diluted hydrochloric acid. The activated sample was allowed to settle for about 3\u0026ndash;4 hours until all ash content reached the upper layer. The upper layer containing ash was removed, and the sample was washed with deionized water to remove organic impurities and subsequently with NaOH to attain neutral condition for the filtered-out solution. Finally, the activated sample was taken in a petri dish and dried at 120\u0026deg;C for 4 hours. All moisture and water contents were properly dried, and the collected sample is the desired activated carbon. Thereafter, the activated carbon was ground, and the weight obtained was noted for yield percentage. The method for preparation of activated carbon from castor stalk is presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e1\u003c/span\u003e. Owing to the unavailability of conventional pyrolizers, like tubular furnaces, we carry out the process in a muffle furnace, making sure the environment is inert. At lieu of nitrogen gas, liquid nitrogen is also used because it is simple to obtain at the institute lab and works well for the experiment. Nitrogen gas can also be used as an alternative to liquid nitrogen. A general overview of activated carbon production, characterization and its applications are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e1\u003c/span\u003ea.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Characterization\u003c/h2\u003e \u003cdiv id=\"Sec6\" class=\"Section3\"\u003e \u003ch2\u003e2.2.1 Proximate \u0026amp; Ultimate Analysis\u003c/h2\u003e \u003cp\u003eCastor stalk was dried in sunlight for 20\u0026ndash;25 days. The unprocessed material underwent crushing and screening to achieve a consistent size smaller than 2.0 mm and thereafter proximate and ultimate analysis were carried out. A proximate analysis was conducted to ascertain the levels of moisture content, ash content, volatile matter, and fixed carbon. This was achieved by employing crucibles, both with and without lids, in a heating oven set to temperatures between 27\u0026ordm;C and 950\u0026ordm;C. The moisture and total ash contents were assessed using the established proximate analysis protocol. The contents of C, H, N, and S of the castor stalk (CAS) and Activated carbon (AC) were measured by the CHNS Analyzer (Thermo Fisher company) using K factors.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section3\"\u003e \u003ch2\u003e2.2.2 Pore Volume, Surface area\u003c/h2\u003e \u003cp\u003eBET Analysis (BELSORP-maxII (S/N: 175, Version 2.0.1.1) was carried out to examine surface area (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{S}_{BET})\\)\u003c/span\u003e\u003c/span\u003e, total Pore volume (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{V}_{t}),\\)\u003c/span\u003e\u003c/span\u003e macro pore volumes (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{V}_{mic})\\:\\)\u003c/span\u003e\u003c/span\u003eand micro pore surface (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{S}_{mic})\\:\\)\u003c/span\u003e\u003c/span\u003e of the synthesized activated carbon using the t-plot method. \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\text{P}\\text{o}\\text{r}\\text{e}\\:\\text{v}\\text{o}\\text{l}\\text{u}\\text{m}\\text{e}\\:\\left({V}_{t}\\right)\\)\u003c/span\u003e\u003c/span\u003e was estimated from nitrogen adsorption at a relative pressure of 0.98. Pore Size Distribution (PSD) was determined using the BJH model. The sample was completely dried and then degassed at 150\u0026ordm;C for 4 hours. After that, using liquid nitrogen, the adsorption and desorption curves were obtained.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section3\"\u003e \u003ch2\u003e\u003cb\u003e2.2.3 Surface Morphology\u003c/b\u003e\u003c/h2\u003e \u003cp\u003eSurface morphology of activated carbon was identified by using Scanning Electron Microscopy using SIGMA 500VP. To study the morphology of Activated Carbon (AC) was dried for 24 hrs. at 110\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:^\\circ\\:\\)\u003c/span\u003e\u003c/span\u003eC. Thereafter the sample was sonicated and then it was dissolved in ethanol.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section3\"\u003e \u003ch2\u003e2.2.4 Functional Group Analysis\u003c/h2\u003e \u003cp\u003eFourier transform infrared spectroscopy was used to analyze the functional groups present in activated carbon and castor stalk in the range 4000\u0026thinsp;\u0026minus;\u0026thinsp;400 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e by using a Spectrophotometer (Agilent Carry 630).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section3\"\u003e \u003ch2\u003e2.2.5 X-Ray Diffraction\u003c/h2\u003e \u003cp\u003eX-ray diffraction was used to identify the presence of any crystalline structure in different ranges of 2θ for activated carbon and castor stalk. The intensity counts were noted for activated carbon at θ\u0026thinsp;=\u0026thinsp;18.3\u0026deg;and for castor stalk biomass its intensity counts peak obtained at θ\u0026thinsp;=\u0026thinsp;22.45\u0026deg;. PAN analytical Empyrean was used for this analysis.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section3\"\u003e \u003ch2\u003e2.2.6 Adsorptive properties\u003c/h2\u003e \u003cp\u003eAdsorptive properties of AC were performed with MB as adsorbate. The calibration curve was plotted using a UV spectrophotometer. Various concentrations of methylene blue ranging from 150\u0026ndash;750 ppm using a stock solution of 1000 ppm. The absorbance was carried out at 668 nm wavelength using a double beam UV- Vis Spectrophotometer (Shimadzu). The relation between adsorption and methylene blue concentration is represented in Eq.\u0026nbsp;1\u003c/p\u003e \u003cp\u003eAds\u0026thinsp;=\u0026thinsp;0.0022C\u0026thinsp;+\u0026thinsp;0.5952 (R\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0.999) [1]\u003c/p\u003e \u003cp\u003eThe adsorptive capacity of MB was analyzed using the batch equilibrium technique. A volume of 100 ml from a stock solution containing 1000 mg/L of MB was diluted to a concentration of 500 mg/L. This diluted solution was then transferred into a 250 ml flask, to which 100 mg of AC sample was added. The resulting mixture was placed inside an incubator set at 25\u003csup\u003eo\u003c/sup\u003eC, where it was stirred for 6 hours to achieve equilibrium. Subsequently, the sample underwent centrifugation at 4000 rpm for 10 minutes. Finally, the activated carbon settled at the bottom, and the remaining concentration of MB was extracted using a pipette. This extracted sample was then subjected to analysis utilizing a UV spectrophotometer. The quantity of MB adsorbed at equilibrium conditions, denoted as q\u003csub\u003ee\u003c/sub\u003e (mg/g), was determined as follows:\u003c/p\u003e \u003cp\u003e \u003cspan class=\"InlineEquation\"\u003e \u003cspan class=\"mathinline\"\u003e\\(\\:{\\text{q}}_{\\text{e}}=\\frac{{\\text{C}}_{\\text{O}}-{\\text{C}}_{\\text{e}}}{\\text{M}}\\text{*}\\text{V}\\)\u003c/span\u003e \u003c/span\u003e [2]\u003c/p\u003e \u003cp\u003e \u003cspan class=\"InlineEquation\"\u003e \u003cspan class=\"mathinline\"\u003e\\(\\:{\\text{C}}_{0}\\:\\)\u003c/span\u003e \u003c/span\u003erepresents the initial concentration of the MB solution, while C\u003csub\u003ee\u003c/sub\u003e represents the final concentration. M stands for the weight of the AC used, and V represents the volume of the MB solution.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e"},{"header":"3. Results and Discussion","content":"\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Proximate Analysis\u003c/h2\u003e \u003cp\u003e1 g of raw biomass Castor Stalk after grinding and messing was taken in a crucible and analyzed at different temperatures for the measurement of moisture content, volatile material, ash content, and fixed carbon. For moisture determination, a 1 g castor stalk sample was heated at 104\u0026ndash;110 \u0026ordm;C without covering the lid of the crucible in a drying oven for 1 hour. Then, for volatile matter, 1 g of sample is placed in a crucible properly covered with a lid and heated at 50\u0026ordm;C/min to 950\u0026thinsp;\u0026plusmn;\u0026thinsp;20\u0026ordm;C and holding at this temperature for 7 min. For ash determination, the sample was heated at a rate of 700 to 750 \u0026ordm;C for 2 hours, and further, the sample was heated so that the final temperature of the furnace rose to 900 to 950 \u0026ordm;C by the end of the second hour, and then finally fixed carbon was determined by subtracting the moisture content, ash content, and volatile matter from the total percentage [ASTM D5142-04, 2010]. The given table suggests the value of carbon content and other constituents present in biomass. The proximate analysis for the castor stalk and activated carbon obtained from the castor stalk is presented in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e shows 3.3 times increase in fixed carbon content in activated carbon in comparison to raw biomass.\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\u003eProximate Analysis of CAS and AC\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\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=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eS. No.\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSample Code\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMoisture (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eAsh (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eVolatile matter (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eFixed carbon (%)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCAS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e10.02\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e14.62\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e57.15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e18.21\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAC\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e6.60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e11.50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e21.42\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e60.48\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=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Ultimate Analysis\u003c/h2\u003e \u003cp\u003eCHNS analysis of raw castor stalk and prepared activated carbon was done to measure the ultimate analysis, i.e., contents of carbon, hydrogen, nitrogen, sulfur, and oxygen. The ultimate analysis of raw castor stalk and prepared activated carbon is presented in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e shows that the material contains 38.96% carbon, 3.55% hydrogen, 1.01% nitrogen, and 56.48% oxygen. After activation, the amount of carbon, hydrogen, and nitrogen in the activated carbon (AC) is found to be 76.49%, 7.83%, and 0.43%. respectively. The carbon content in the activated carbon was almost doubled. There was a 4.28% rise in hydrogen content and a 0.58% decrease in nitrogen content in the obtained.\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\u003e% Values of CHNS Observed in raw CAS (Castor stalk) and Activated Carbon (AC)\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=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eS. No.\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSample Code\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e%C\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e%H\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e%N\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003e%S\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003e% O\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCAS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e38.96\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e3.55\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e56.48\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAC\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e76.49\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e7.83\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.43\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e15.25\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=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003e3.3% Yield\u003c/h2\u003e \u003cp\u003eThe activated carbon was synthesized using powdered castor stalk, KOH, and Alum in the ratio (1:1.5:0.1). Alum was added to enhance the porosity of the activated carbon. The initial weight of the castor stalk powder was noted. The mixture of powdered stalk, KOH and Alum was impregnated for 24 hours under continuous stirring. Then the sample was activated at 550 \u0026ordm;C \u0026minus;\u0026thinsp;900 \u0026ordm;C at a step of 50\u003csup\u003eo\u003c/sup\u003eC for 60 minutes, taking the same impregnation ratio. Then the sample was filtered out to remove KOH and Alum by adding 10% dilute hydrochloric acid, which helps to neutralize its pH to 7. Finally, the sample was dried in the oven for 4 hours at 110 \u0026ordm;C. The sample was weighed again, and the % yield was calculated using Eq.\u0026nbsp;(3)\u003c/p\u003e \u003cp\u003e \u003cspan class=\"InlineEquation\"\u003e \u003cspan class=\"mathinline\"\u003e\\(\\:\\text{%}\\:\\text{Y}\\text{i}\\text{e}\\text{l}\\text{d}=\\:\\frac{\\text{W}\\text{e}\\text{i}\\text{g}\\text{h}\\text{t}\\:\\text{o}\\text{f}\\:\\text{P}\\text{r}\\text{o}\\text{d}\\text{u}\\text{c}\\text{t}}{\\text{W}\\text{i}\\text{e}\\text{g}\\text{h}\\text{t}\\:\\text{o}\\text{f}\\:\\text{s}\\text{a}\\text{m}\\text{p}\\text{l}\\text{e}\\:\\text{t}\\text{a}\\text{k}\\text{e}\\text{n}}\\text{*}100\\)\u003c/span\u003e \u003c/span\u003e [3]\u003c/p\u003e \u003cp\u003ewhere weight of product was the weight of activated carbon obtained after the complete removal of moisture and weight of the sample taken was the initial weight of raw castor stalk taken for the experiment.\u003c/p\u003e \u003cp\u003eThe observed trend in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e2\u003c/span\u003ea shows that with an increase in the temperature of activation during pyrolysis, the yield percentage of the activated carbon produced decreased. Further, the activated carbon thus produced at various temperatures was analyzed for methylene blue adsorption studies and are presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e2\u003c/span\u003eb. It is observed that with an increase in temperature from 550\u003csup\u003eo\u003c/sup\u003eC to 700\u003csup\u003eo\u003c/sup\u003eC the adsorption of methylene blue increased and thereafter with an increase in temperature from 750\u003csup\u003eo\u003c/sup\u003eC to 900\u003csup\u003eo\u003c/sup\u003eC it decreased. This may be due to the fact that at low temperatures the ash content or volatile matter is present in the activated carbon which has increased the yield % of activated carbon and showed lower adsorption. So, for the current study activated carbon obtained at 700\u0026ordm;C with 8.5% yield was used for further characterization and adsorption studies of methylene blue and CO\u003csub\u003e2\u003c/sub\u003e.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec16\" class=\"Section2\"\u003e \u003ch2\u003e3.4 BET analysis\u003c/h2\u003e \u003cp\u003eNitrogen adsorption isotherm at -196\u0026deg;C was used to find the specific surface area and pore structure of activated carbon produced from castor stalk (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e3\u003c/span\u003e) and the results are presented in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\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\u003eBET analysis of AC\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\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 \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eS. No.\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSample Code\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSurface Area\u003c/p\u003e \u003cp\u003e(m\u003csup\u003e2\u003c/sup\u003e/g)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePore Volume\u003c/p\u003e \u003cp\u003e(cm\u003csup\u003e3\u003c/sup\u003e/g)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003ePore Diameter\u003c/p\u003e \u003cp\u003e(nm)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAC\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1687\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.0150\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.7095\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=\"Tab4\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eComparison of BET surface area of Porous Carbon derived from various agro-residues.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\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=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePrecursor\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eActivating agent\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eImpregnation ratio\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eActivation temperature (K)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eS\u003csub\u003eBET\u003c/sub\u003e,\u003c/p\u003e \u003cp\u003em\u003csup\u003e2\u003c/sup\u003e /g\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eReferences\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCoconut shell\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eKOH\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1:3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e873\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1172\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e[15]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGarlic peel\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eKOH\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1:2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1073\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1262\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e[16]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRice Husk\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eKOH\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1:3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e873\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e755\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e[17]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eArundo donaxa\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eKOH\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1:2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e873\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1122\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e[18]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRotten strawberries\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eKOH\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1:2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e923\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1117\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e[19]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eChestnut shell\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNaNH\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1:1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e773\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1416\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e[20]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSugarcane bagasse\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eKOH\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1:2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e873\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1113\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e[21]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCotton boll\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eKOH\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1:2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e973\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1381\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e[22]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTea seed shell\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eKOH\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1:4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e973\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1503\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e[23]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eCastor Stalk\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eKOH\u0026thinsp;+\u0026thinsp;Alum\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e1:1.5:0.1\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e973\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e1687\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cb\u003ePresent study\u003c/b\u003e\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\u003eThe observed adsorption hysteresis loop was classified as type 4. The pore type was observed to be the inkbottle type, which was associated with the desorption process [24]. The surface area of the synthesized activated carbon is found to be 1687 m\u003csup\u003e2\u003c/sup\u003e/g, with a pore volume of 1.0150 cm\u003csup\u003e3\u003c/sup\u003e/g and a pore diameter of 2.7095 nm. A comparative study of surface area of AC produced from various biomasses is presented in Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e which highlights higher surface area for AC synthesized in the present study. It may be due to the novel synthesis technique adopted where the alum has been used in addition to KOH as the activating agent and also the inert atmosphere was created using liquid nitrogen. High surface area has resulted in enhanced the adsorption capacity.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec17\" class=\"Section2\"\u003e \u003ch2\u003e3.5 Analysis of Functional groups:\u003c/h2\u003e \u003cp\u003eFTIR spectra for both castor stalk and activated carbon is presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e4\u003c/span\u003e. In the castor stalk spectrum, we observe peaks at 1027.45 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 1239.11 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, which can be attributed to the stretching of C-O-C bonds in ethers. Additionally, peaks at 1736.40 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e are associated with the stretching vibrations of C\u0026thinsp;=\u0026thinsp;O bonds within aromatic rings, and a C-N stretching vibration is evident at 2367.26 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e.C-N stretching at wave number 2367.26 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e was also observed in activated carbon. After activation, the castor stalk AC was ascribed to C-H stretching at wave number 22913.87 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. The band at 3341.29 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is attributed to NH stretching. And finally, bands at 3638.27 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e represent O-H stretching in hydroxyl functional groups, which was presented in the raw material castor stalk as well as in the activated carbon obtained after activation. The details of functional groups at their respective wavenumbers are provided in Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\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\u003eFTIR Result of raw Castor Stalk (CAS) and Activated Carbon (AC).\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\u003eWave number (cm\u003csup\u003e\u0026minus;\u0026thinsp;1)\u003c/sup\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1027.45,\u003c/p\u003e \u003cp\u003e1239.11\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1736.40\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2367.26\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2913.87\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003e3341.29\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u0026ge;\u0026thinsp;3638.71\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCAS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eC-O\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eC\u0026thinsp;=\u0026thinsp;O\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eC-N\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eC-H\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eN-H\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eO-H\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAC\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e----\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e----\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eC-N\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e----\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e----\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eO-H\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=\"Sec18\" class=\"Section2\"\u003e \u003ch2\u003e3.6 X-Ray Diffraction Analysis\u003c/h2\u003e \u003cp\u003eXRD analysis results for castor stalk and activated carbon is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e5\u003c/span\u003e. XRD method is usually used to identify materials crystallographic features. The difference in structures of raw biomass castor stalk and porous activated carbon can be clearly revealed in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e5\u003c/span\u003e. The intensity counts are observed to check the presence of Potassium (K), Aluminum (Al) and Hydride (H) in the amorphous activated carbon as Alum and KOH are used as activating reagent during preparation of porous activated carbon. Because of the amorphous character the peaks were not as clearly identified as it was being observed for crystalline samples. The activated carbon does not show much intensity count peaks throughout 10\u003csup\u003eo\u003c/sup\u003e to 80\u003csup\u003eo\u003c/sup\u003e angle for 2θ which may be due to the amorphous nature of the activated carbon synthesized. A strong and broad diffraction peak count intensity were detected for activated carbon (AC) at 2θ\u0026thinsp;=\u0026thinsp;14.2\u0026deg; reveals amorphous structure of activated carbon [25]. Similarly, at 2θ\u0026thinsp;=\u0026thinsp;22.4\u0026deg; for castor stalk powder 4500\u0026thinsp;+\u0026thinsp;counts intense peak is observed which may be due to presence of some metal oxide having some crystalline structure [26].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec19\" class=\"Section2\"\u003e \u003ch2\u003e3.7 Surface Morphology of Activated Carbon\u003c/h2\u003e \u003cp\u003eSEM images of the microstructures of the AC reveals the fluffy and porous structure of the synthesized activated carbon (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e6\u003c/span\u003e). Further the external surface of the AC seems to be full of cavities. At 10 \u0026micro;m, 3 KX and 3 \u0026micro;m, 7 KX, magnification, the spherical pores were observed. AC is a porous material having large number of mesopores and micro pores of different dimensions. KOH and Alum were used as reagent during activation leads to the formation of cavities and pores. Further washing with hydrochloric acid might have resulted in the formation of micro pores within the carbon matrix.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec20\" class=\"Section2\"\u003e \u003ch2\u003e3.8 Methylene Blue (MB) Analysis\u003c/h2\u003e \u003cp\u003e100 mg of AC was added in 100 ml of 500 ppm of Methylene blue. The adsorption studies were carried out for 6 hours under continuous stirring After 6 hours of batch adsorption, the absorbance value of activated carbon for methylene blue was analyzed using UV spectrophotometer at 668 nm wavelength. The observed absorbance of the final solution was observed to be 0.7102 which shows 52.27% adsorption. Further the methylene blue adsorption capacity was calculated using Eq.\u0026nbsp;[2] and was observed to be 447.72 mg/g.\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\u003eComparison of MB adsorption (mg/g) of AC synthesized from different biomass.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\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=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePrecursor\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eActivating agent\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSurface area (m\u003csup\u003e2\u003c/sup\u003e/g)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMethylene blue value (mg/g)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eReferences\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTea waste\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eH\u003csub\u003e3\u003c/sub\u003ePO\u003csub\u003e4\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2054.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e402.25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e[27]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePalm shells\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eZnCl\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e731\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e163.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e[28]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSorghum residues\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eZnCl\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1817\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e386.10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e[29]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOil palm fiber\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMicrowave radiation\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e707.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e312.50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e[30]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDate pits\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eFeCl\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e780\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e259.20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e[31]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCotton stalk\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eZnCl\u003csub\u003e2\u003c/sub\u003e\u0026thinsp;+\u0026thinsp;microwave radiation\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e794\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e193.50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e[32]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eCastor Stalk\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eKOH\u0026thinsp;+\u0026thinsp;Alum\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e1687\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e447.72\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003ePresent study\u003c/b\u003e\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\u003eTable\u0026nbsp;\u003cspan refid=\"Tab6\" class=\"InternalRef\"\u003e6\u003c/span\u003e shows the compression of methylene blue value obtained by activated carbon produced from different biomass and also the activated carbon produced in this research work. It was observed that the value of methylene blue obtained from castor stalk was much higher than the values obtained from all other biomass as compared. Thus, we can say because of chemical activation of castor stalk with KOH and Alum the activated carbon synthesized has much higher adsorption capacity than it was produced by other activating reagents.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec21\" class=\"Section2\"\u003e \u003ch2\u003e3.10 Adsorption of CO\u003csub\u003e2\u003c/sub\u003e on obtained Activated Carbon\u003c/h2\u003e \u003cp\u003eCO\u003csub\u003e2\u003c/sub\u003e adsorption isotherms were assessed employing a static volumetric system known as ASAP 2020. The samples underwent in-situ activation by heating them to 200\u0026deg;C, gradually increasing the temperature at a rate of 5\u0026deg;C per minute under vacuum conditions (0.005 mm Hg) overnight, utilizing the degassing system integrated into the ASAP 2020 equipment. To maintain the desired adsorption temperature, water from a constant temperature water bath was circulated [33]. The adsorbate gas was introduced into the setup in specific volumes required to attain a predetermined range of pressures, spanning from 1 to 760 mmHg. Three pressure transducers, each with a different range of 1, 10, and 1000 mmHg, were employed to measure the pressures accurately. To ascertain equilibrium for each measurement point, a minimum equilibrium interval of 20 seconds was enforced, with a maximum relative tolerance of 5% relative to the target pressure and an absolute tolerance of 5 mmHg. The adsorption capacity, denoted as millimoles of gas adsorbed per gram of adsorbent, was derived from the adsorption isotherms [34] (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e7\u003c/span\u003e). Notably, the adsorption capacity for CO\u003csub\u003e2\u003c/sub\u003e is observed to be 2.46 mmol/g at a temperature of 298.15K and a pressure of 1 atm. Comparison of CO\u003csub\u003e2\u003c/sub\u003e adsorption capacity of activated carbon synthesized from various biomass is presented in Table\u0026nbsp;\u003cspan refid=\"Tab7\" class=\"InternalRef\"\u003e7\u003c/span\u003e which shows a remarkable high adsorption in comparison to reported adsorbents. This achievement is exceptional, especially considering that the activated carbon was produced using a novel pyrolysis process conducted in muffle furnaces, with the additional use of liquid nitrogen to create an inert atmosphere during the chemical activation process.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab7\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 7\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eComparison of CO\u003csub\u003e2\u003c/sub\u003e adsorption capacity of activated carbon synthesized from various biomass.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\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=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePrecursor\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eActivating agent\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eImpregnation ratio\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eActivation temp (K)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eCO\u003csub\u003e2\u003c/sub\u003e Adsorption (mmol/g) at 25\u003csup\u003eO\u003c/sup\u003eC\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eReferences\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePalm Kernel Shell\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePhysical Activation\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e--\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1123\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e2.13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e[35]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOlive Stones\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePhysical Activation\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e--\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1073\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.98\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e[36]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCoconut shell\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eKOH\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1:2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1073\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.80\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e[37]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSargassum\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eKOH\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1:1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1073\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.05\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e[38]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eEnteromorpha\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eKOH\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1:1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1073\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.52\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e[38]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCoffee Grounds\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eKOH\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1:2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e873\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e3.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e[39]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eWheat flour\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eKOH\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1:5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1073\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e2.28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e[40]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eCastor Stalk\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eKOH\u0026thinsp;+\u0026thinsp;Alum\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e1:1.5:0.1\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e973\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e2.46\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cb\u003ePresent study\u003c/b\u003e\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"},{"header":"4. Conclusion","content":"\u003cp\u003ePorous activated carbon obtained from castor stalk is cost effective due to its abundance availability and low cost. Pyrolysis process using muffle furnace is also termed to be as clean and new methodology with very low cost of production. To manage various agro-residues development of porous activated carbon can be considered to be one of the most predominating pathways for CO\u003csub\u003e2\u003c/sub\u003e capture. Single step activation of castor stalk biomass using amalgamation of Alum and KOH as activating agent at a temperature of 700\u0026thinsp;\u0026plusmn;\u0026thinsp;10\u003csup\u003eo\u003c/sup\u003eC and 60 min holding time was considered. Yield %, calorific value of biomass, (FTIR) for different functional group in raw biomass and activated carbon, (XRD) for crystalline and amorphous nature, (SEM) for Surface morphology, (CHNS) for ultimate analysis, methylene blue value and Proximate analysis were the various characterization technique used. Beside 447.72 mg/g methylene blue value, a very high surface area 1687 m\u003csup\u003e2\u003c/sup\u003e/g with pore volume of 1.0150 cm\u003csup\u003e3\u003c/sup\u003e/g and a pore diameter of 2.7095 nm was observed. CO\u003csub\u003e2\u003c/sub\u003e adsorption isotherm data have been obtained from a static volumetric system (ASAP 2020). The remarkable aspect of this accomplishment lies in the fact that, under a temperature of 298.15K and a pressure of 1 atm, the CO\u003csub\u003e2\u003c/sub\u003e adsorption capacity reached an impressive 2.46 mmol/g. What makes this even more noteworthy is that the activated carbon was manufactured using an innovative pyrolysis method within muffle furnaces, and an additional step involved the utilization of liquid nitrogen to establish an inert atmosphere during the chemical activation procedure.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch3\u003e\u003cstrong\u003eEthical approval\u003c/strong\u003e\u003c/h3\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003ch3\u003e\u003cstrong\u003eConsent to participate\u003c/strong\u003e\u003c/h3\u003e\n\u003cp\u003eAll authors gave explicit consent to participate.\u003c/p\u003e\n\u003ch3\u003e\u003cstrong\u003eConsent to publish\u003c/strong\u003e\u003c/h3\u003e\n\u003cp\u003eAll authors gave explicit consent to submit.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that no funds, grants, or other support were received during the preparation of this manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors contribution\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePanchanan Pramanik:\u003c/strong\u003e Resources, Methodology, Investigation, Data Curation, Writing-Original draft, \u003cstrong\u003eRenu Gupta:\u003c/strong\u003e Analyzing characterization, Editing draft,\u003cstrong\u003e\u0026nbsp;Ajay Bansal:\u003c/strong\u003e Conceptualization, Supervision, Editing draft.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting Interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll authors involved in this manuscript have approved it and declare that they have no conflict of interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot required\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgment:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors gratefully acknowledge Dr. B.R Ambedkar National Institute of Technology Jalandhar for providing all research facilities. The authors also acknowledge IIT Delhi, SAIF-IIT Bombay, CSMCRI Bhavnagar for providing characterization facilities.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eJ. D. Figueroa, T. Fout, S. Plasynski, H. McIlvried, and R. D. Srivastava, \u0026ldquo;Advances in CO2 capture technology-The U.S. Department of Energy\u0026rsquo;s Carbon Sequestration Program,\u0026rdquo; \u003cem\u003eInt. J. Greenh. Gas Control\u003c/em\u003e, vol. 2, no. 1, pp. 9\u0026ndash;20, 2008, doi: 10.1016/S1750-5836(07)00094-1.\u003c/li\u003e\n\u003cli\u003eH. Yang \u003cem\u003eet al.\u003c/em\u003e, \u0026ldquo;Progress in carbon dioxide separation and capture: A review,\u0026rdquo; \u003cem\u003eJ. Environ. Sci.\u003c/em\u003e, vol. 20, no. 1, pp. 14\u0026ndash;27, 2008, doi: 10.1016/S1001-0742(08)60002-9.\u003c/li\u003e\n\u003cli\u003eR. Wang, P. Wang, X. Yan, J. Lang, C. Peng, and Q. 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October, pp. 1\u0026ndash;10, 2016, doi: 10.1038/srep34590.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Biomass, Castor stalk, Activated carbon, Pyrolysis, Methylene blue, CO2 adsorption","lastPublishedDoi":"10.21203/rs.3.rs-5879347/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5879347/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eGreenhouse gas emissions have become a pressing concern in recent times, with CO\u003csub\u003e2\u003c/sub\u003e emerging as the primary culprit behind global warming, rising sea levels, and disruptions to ecosystems. Of all the greenhouse gases, CO\u003csub\u003e2\u003c/sub\u003e's impact on global warming stands out as the most significant. To address this issue, activated carbon (AC) has gained prominence as an effective CO\u003csub\u003e2\u003c/sub\u003e adsorption agent, owing to its porous structure, expansive surface area, cost-effectiveness, and environmentally friendly properties. In this current research, activated carbon was produced from castor stalk biomass through a single-stage chemical activation process known as pyrolysis. This method is lauded for its cost-efficiency, simplicity, and minimal environmental impact. Potassium hydroxide (KOH) and aluminum sulfate (ALUM) were employed as the activating agents. Subsequently, the synthesized activated carbon was subjected to Methylene Blue adsorption testing to evaluate its CO\u003csub\u003e2\u003c/sub\u003e adsorption capacity, among other potential applications. The characterization of the activated carbon derived from castor stalk involved a series of techniques, including CHNS analysis, proximate analysis, SEM, FTIR, XRD, and BET surface area analysis. These analyses unveiled the impressive attributes of the castor stalk-derived activated carbon, featuring an exceptionally high surface area of 1687 m\u003csup\u003e2\u003c/sup\u003e/g, a substantial pore volume of 1.015 cm\u003csup\u003e3\u003c/sup\u003e/g, and a pore diameter of 2.71 nm. Furthermore, the Methylene Blue adsorption test yielded a remarkable value of 447.72 mg/g with 89.5% adsorption efficiency. High CO\u003csub\u003e2\u003c/sub\u003e adsorption capacity (2.46 mmol/g) was observed over castor stalk-derived activated carbon. The comparative study shows higher CO\u003csub\u003e2\u003c/sub\u003e adsorption capacity in comparison to activated carbon derived from various biomasses using KOH as the activating agent. So, the present study shows activated carbon derived from Castor stalk using KOH and Alum as activating agent can be a promising method for CO\u003csub\u003e2\u003c/sub\u003e adsorption.\u003c/p\u003e","manuscriptTitle":"Chemical Activation of Castor Stalk-Derived Porous Carbon for Highly Efficient CO 2 Adsorption in Sustainable Carbon Capture Applications","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-01-24 13:14:58","doi":"10.21203/rs.3.rs-5879347/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"cda49013-449a-4479-964a-dd5f983b63f5","owner":[],"postedDate":"January 24th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-01-28T12:39:05+00:00","versionOfRecord":[],"versionCreatedAt":"2025-01-24 13:14:58","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-5879347","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5879347","identity":"rs-5879347","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}