Investigation doping effects of Copper to enhance photocatalytic performance of Tungsten Trioxide for advanced Tetracycline elimination even under visible light

Investigation doping effects of Copper to enhance photocatalytic performance of Tungsten Trioxide for advanced Tetracycline elimination even under visible light | 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 Investigation doping effects of Copper to enhance photocatalytic performance of Tungsten Trioxide for advanced Tetracycline elimination even under visible light Nguyen Viet Khoa, Nguyen Thi Hanh, Nguyen Thuy Huong, Phuong Thao, and 4 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4373404/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 The goal of the research was to improve photocatalytic activity of WO 3 by Cu doping to use for tetracycline decomposition. Firstly, the Cu dopant worked as nuclei for the crystallization of WO 3 leading to an increase in growth and sizes of formed crystals. However, the incorporation of Cu dopants in the WO 3 induced significant deviation into the WO 3 lattice inhibiting agglomeration of the WO 3 crystals to form large particles. Therefore, the crystal sizes of Cu-WO 3 were bigger than the WO 3 crystals, however, the Cu-WO 3 particles compared to WO 3 particles were smaller. By existing in the WO 3 lattice, the Cu dopant created an intermediate band to decrease band-gap energy and to boost electron-hole separation of the WO 3 . Therefore, the synthesized Cu-WO 3 effectively generated large electrons and holes for the decomposition of tetracycline under visible light excitation. The study investigated that 3Cu-WO 3 , in which the Cu doping ratio was 3% mole, showed the highest tetracycline decomposition efficiency (∼79.5%). This was due to the doping of Cu into the WO 3 lattice reached a limit, excess that limitation, Cu precursor formed CuO distributing on the WO 3 surface to eclipse light reaching the material leading to decrease in electron-hole separation rate due to limited light absorption or decrease in photocatalytic degradation. Finally, the Cu-WO 3 exhibited novel stability during the degradation of tetracycline. Cu dopant WO3 Photocatalysis Tetracycline removal Recycling Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 1. Introduction Antibiotics have always been an inseparable part of healthcare for humans and animals. However, enormous scientific evidences indicated that their convenient as well as indiscriminate antibiotic uses lead to their sharply increasing environmental occurrences resulting in multiple unintended consequences (Kraemer et al. 2019 , Larsson &Flach 2022 , Liu et al. 2021 , Martinez 2009 , Yang et al. 2023 ). Against both Gram(-) and Gram(+) bacteria, mycoplasma, parasites and fungus, Tetracycline (TC) as one of the primary antibiotic groups with broad spectrum activity, has been used regularly in veterinary treatment, human therapy purposes as well as agricultural sector (Gopal et al. 2020 ). However, the antibiotic has been used extensively without any dosage regulation in most nations. More than 50% of used Tetracycline was excreted in the forms of feces and urine of the treated organisms (Hu et al. 2022 ). The primary and secondary treatments in conventional wastewater treatment plans would be not sufficient for complete TC removal. Uncontrolled use and released TC, which is a persistent compound and could be transformed into even more harmful substances in natural biodegrading cycles, caused the spread of mutated bacteria, which can resist multiple antibiotics, leading to environmental and ecological damages as well as bioaccumulating in the food chain resulting in threatening human health. Thus, there is an urgent need to investigate a sustainable and advanced technology to completely eliminate Tetracycline as well as other antibiotics from the environment to overcome the threatening problem. Several removal techniques, such as membrane filtration, adsorption onto the material, reverse osmosis, and advanced oxidation processes (ozonation, photolysis, and photocatalysis), have been researched thoroughly and applied to treat wastewater containing TC (Gopal et al. 2020 , Liu et al. 2017 , Song et al. 2022 , Wang et al. 2018 , Xiong et al. 2024 ). Among them, photocatalysis, in which photocatalyst would be excited by suitable incident light to release free radicals, such as HO˙, − O 2 ˙, and HO 2 ˙, for antibiotic degradation into simpler byproducts resulting in complete TC removal from wastewater, has been studied comprehensively as a promising removal technology (Cao et al. 2019 , López-Peñalver et al. 2010 , Norvill et al. 2017 , Wu et al. 2020 ). As a conventional photocatalyst, TiO 2 has been broadly utilized for elimination of numerous kinds of organic pollutants. Nevertheless, the used TiO 2 only showed good degradation efficiency under excitation of ultraviolet light (Jing et al. 2023 , Li et al. 2023 ). Only less than 5% of the solar light spectrum is ultraviolet light irradiation greatly restricting applications of the TiO 2 in practical systems. Therefore, it is particularly crucial to investigate a suitable photocatalyst effectively working under visible light, which accounts for approximately 44% of solar light (Luo et al. 2023 ). Currently, tungsten oxide (WO 3 ), has received broad popularity because of its non-toxic, industrial-friendly cost, reasonable stability, and moderate band gap energy (∼2.8 eV) (Ajel &Al-nayili 2023 , Yao et al. 2021 ). Previous literature reports demonstrated that the WO 3 has higher valence band potential than the requiring oxidation potential for hydroxyl radical formation (Tang et al. 2023 , Zhao et al. 2023 ). Hence, photo-generated holes, which were produced when the WO 3 was excited by the suitable incident light, effectively reacted with H 2 O to form hydroxyl radicals resulting in high organic pollutant degradation efficiencies. However, degradation efficiencies of the pure WO 3 would be halved due to its excessive electron-hole recombination, insufficient visible light absorption, and low surface area. Thus, numerous strategies, including micromorphology control, metal and/or non-metal doping, noble metal deposition, and heterojunction construction, have been researched to overcome one or all of these limitations. Among them, doping transitional metals, such as Ni, Fe, and Zn, into the lattice of the WO 3 greatly enhanced its photocatalytic performance (Naeimi et al. 2022 , Song et al. 2015 ). For instance, Hui Song et al. have doped Fe successfully into the pure WO 3 lattice (Song et al. 2015 ). The authors investigated that the phenomenal degrading performance by the Fe-doped WO 3 was approximately 93%, which was much higher than that by the pure WO 3 (~ 10%). Copper – Cu, a transition metal with low cost, has been widely used as a dopant to incorporate into various photocatalyst lattices, such as CoFe 2 O 4 , TiO 2 , Bi 2 MoO 6 , and BiVO 4 , to enhance their photocatalytic performance (Bakhtiarnia et al. 2023 , Mo &Zhang 2024 , Wang et al. 2023 ). In our earlier researches, Cu was successfully doped into TiO 2 , ZnO, and NiWO 4 to improve their photocatalysis for elimination of various organic pollutants, and even converted CO 2 into valuable products (Hanh et al. 2019 , Pham &Lee 2015 , Thanh Truc et al. 2019 , Tri et al. 2019 ). The obtained results indicated that due to similarity in ionic radii, Cu dopants replaced certain Ti, Zn, and W ions in the TiO 2 , ZnO, and NiWO 4 lattices, respectively. By doping into the TiO 2 (ZnO or CuWO 4 ) lattices, Cu dopants effectively decreased their band gap energies. With the outer electron shell configuration of 3d 9 , Cu dopant could perform as an electron receptor to minimize electron-hole recombination rate of these materials resulting in their photocatalytic enhancement. Based on obtained results from previous studies, this study is designed for investigating Cu as a promising dopant to dope into WO 3 lattice to enhance photocatalysis of the WO 3 before being used for the tetracycline removal process in aqueous environment. 2. Experiments 1.1. Material preparation To obtain a homogeneous solution for synthesis of WO 3 , double distilled water was used to dissolve sodium tungstate dihydrate (Na 2 WO 4 .2H 2 O) before stirring for 30 minutes. Then, a 3M HCl solution was slowly dropped into the solution for pH control to 1 before monitoring its temperature to 80 ℃ for the next 2 hours. An achieved yellow suspension was then centrifuged and washed by distilled water. The obtained precipitate was continuously air dried for 24 hours and calcinated for next 2 hours at 500 ℃ to achieve WO 3 . Cu-doped WO 3 was also prepared via co-precipitation method. Copper chloride (CuCl 2 ) solution was added into the prepared solution of sodium tungstate before stirring for 30 minutes. The above used HCl solution (3M) was also dropped to the solution for pH control to 1. Then, temperature of the obtained suspension was controlled to 80 ℃ for 2h. Centrifugation was also used to separate the obtained yellow precipitate of the suspension. Double distilled water was also used to wash the separated precipitate before air drying for 24 hours and calcinating at 500 ℃ for 2 hours to achieve Cu-doped WO 3 (Cu-WO 3 ) samples. The amounts of used CuCl 2 solution were measured to obtain 1Cu-WO 3 , 2Cu-WO 3 , 3Cu-WO 3 , 4Cu-WO 3 and 5Cu-WO 3 samples, which the Cu/WO 3 ratios were 1, 2, 3, 4, and 5% mole, respectively. An AXS D8 X-ray diffractometer (XRD) was used to investigate crystalline structure of synthesized materials. At the same periods, morphology as well as elemental mapping of the prepared materials were examined by a S-4800 scaning eletron microscope (SEM) equipping with an HD-2700 energy dispesive X-ray detetor (EDX). To analyze optical properties of synthesized materials, an UV-3101PC ultra violet – visible absorption spectrometer (UV-Vis) was applied. 1.2. Photocatalysis test To investigate photocatalytic efficiency, 50 mg of the prepared material was put into tetracycline solution (200 mL, 10 ppm), then stirred in the dark for 2 hours before being irradiated with a 35 W LED lamp to activate the photocatalysis. Then, for every 30 mins passing, 10 mL sample was taken quickly to centrifugate at the speed of 12000 rpm for 15 mins. A PTFE filter was continuously used to eliminate the remaining material after centrifugation. Then, the filtered solution was examined by an ultraviolet-visible spectrometer at 368.5 nm to detect remaining tetracycline contents. Recycling experiments were also carried out to investigate the material’s stability as well as recovery ability after being used for the tetracycline elimination process. In a distinctive experiment, the used photocatalyst for tetracycline decomposition for 4 hours, was filtrated to collect before washing with distilled water. Then, the obtained sample was dried in a vacuum dark chamber at 150 o C for 24 hours before being continuously used for the next tetracycline elimination cycle. 3. Result and Discussion 3.1. Material characteristics 3.1.1. Doped photocatalyst Figure 1 presented XRD results of synthesized WO 3 and Cu-WO 3 samples. This showed that the prepared WO 3 material has XRD pattern similarity to the standard WO 3 (PDF Card No. 1528915) with a monoclinic phase. Peaks locating at 2 θ = 20.38°, 23.08°, 23.56°, 24.32°, 26.6°, 28.58°, 33.27°, 34.16°, 35.62°, 41.82°, 44.95°, 47.28°, 48.30°, 50°, 53.48°, 54.2°, 54.92°, 55.9°, 58.21°, 60.43°, 62.26° are well identified, which corresponded to (11 − 1), (002), (020), (200), (120), (11 − 2), (022), (220), (122), (222), (132), (004), (140), (024), (042), (240), (420), (332), (242), and (340) planes. In comparison to the WO 3 XRD pattern, these Cu-WO 3 XRD patterns displayed both peak intensity increases and sharpness. The XRD patterns of CuWO 3 samples also revealed a slightly left shifted. The influents of Cu dopants distorting WO 3 lattice parameters were investigated using the Scherrer formula and Miller indices (hkl) (Deepa &Rajendran 2018 , Prabhu et al. 2014 ). The obtained results were presented in Table 1 , which shown that the Cu-WO 3 materials revealed an increase in crystal sizes as compared to the pure WO 3 . The phenomenon was because of the Cu dopants, which acted as nuclei for WO 3 crystallization during the synthesizing process (Carson et al. 2012 ). Thus, the crystallization process would be greatly enhanced with the aid of Cu nuclei resulting in an increase in growth and size of formed crystals. Furthermore, significant lattice parameter differences were observed between the doped materials and the pure WO 3 (Table 1 ). The interference of Cu dopants, which replaced numerous W elements in the WO 3 lattice, could be the cause of the divergence. The replacement caused the lattice disorder because Cu 2+ and W 6+ have different ionic radii (Assadi &Hanaor 2016 , Bakhtiarnia et al. 2023 , Khalid et al. 2022 , Naeimi et al. 2022 ). Hence, the acquired XRD pattern outcomes designated that Cu was effectively doped into the crystal structure of WO 3 . Table 1 also indicated that the lattice parameter deviation in Cu-WO 3 materials tends to increase within copper dopant ratios increase up to 3% in mole. Nevertheless, further deviation could not be seen with further copper doping ratio increases from 4 to 5% samples. This was due to the doping of copper into the WO 3 matrix reached limitation. Excessive copper precursor distributed on surface of the WO 3 instead of doping into its lattice. The distributed copper could be oxidized to CuO during material calcination in the air. Therefore, low peaks at 35.58 and 38.92 o corresponding to CuO components were observed in the XRD patterns of the synthesized 4Cu-WO 3 and 5Cu-WO 3 . Table 1 Lattice parameters and crystal sizes of prepared photocatalysts Samples Crystal sizes (nm) Lattice parameters Surface area (m 2 /g) a (Å) b (Å) c (Å) Cell-volume (Å 3 ) WO 3 22.95 7.2999 7.5305 7.6790 422.0770 7.6 1Cu-WO 3 27.04 7.3118 7.5368 7.6855 423.4754 10.52 2Cu-WO 3 29.36 7.3118 7.5431 7.6987 424.8979 13.37 3Cu-WO 3 30.65 7.3266 7.5526 7.7085 426.4962 15.16 4Cu-WO 3 30.78 7.3281 7.5538 7.7099 426.7272 15.82 5Cu-WO 3 30.86 7.3289 7.5548 7.7112 426.9058 16.26 3.1.2. Morphology Figure 2 presented the SEM images to describe surface morphology of synthesized WO 3 (2A) and 3Cu-WO 3 (2B) materials. At first, SEM images proved that synthesized materials were nanoparticles. Later, SEM images indicated that WO 3 particles, which are approximately 200 nm, were larger than Cu-WO 3 particles, which were approximately 80 nm. This was because Cu dopants defected the WO 3 lattice causing its disorder. Thus, the agglomeration of these disordered WO 3 crystals to form large particles was inhibited resulting in a decrease in particle sizes of Cu-WO 3 materials in comparison to the pure WO 3 . To further determine surface morphology, the prepared WO 3 and Cu-WO 3 photocatalysts were analyzed via nitrogen adsorption/desorption isotherms. The calculated BET surface areas of the prepared materials were also presented in the Table 1 . Additionally, Fig. 2 C displayed the obtained isotherms for WO 3 and 3Cu-WO 3 materials. Firstly, isotherms of both WO 3 and 3Cu-WO 3 were hysteresis loops indicating that they were mesoporous materials. In addition, the WO 3 and 3Cu-WO 3 isotherms also showed H2 inferring hysteresis types. It signified that the surface of WO 3 and Cu-WO 3 samples contained pores shaped like ink-bottle and randomly folded sheets (Zhang et al. 2021 ). The estimated surface area of pure WO 3 sample was greatly smaller than those of Cu-WO 3 samples (Table 1 ). The increasing in surface area of the Cu-WO 3 materials in comparison to the WO 3 was firstly because the particles of the Cu-WO 3 was substantially smaller than the WO 3 particles. Secondly, the distribution of pore sizes in WO 3 and 3Cu-WO 3 materials, showing in the inset Figure in Fig. 2 C, indicated the fact that the surface area increases of the doped materials were caused by the pore number increases or by the Cu dopants, which interfered mesopore formation on the surface of the WO 3 material. Table 1 also indicated that among these Cu-WO 3 samples, the 5Cu-WO 3 sample exhibited the highest BET surface area. This could be due to CuO oxides distributing on the WO 3 surface induced mesopore formation. 3.1.3. Optical characteristics The remarkable visible light absorption enhancement and red shifted in absorption edges could be seen in the optical absorption spectra of Cu-WO 3 in comparison to that of pure WO 3 (Fig. 3 A). In the PL spectra, the peaks of the Cu doped WO 3 materials were also significantly lower than that of the pure WO 3 also demonstrating that the electron-hole recombination of the doped materials was greatly prevented (Fig. 3 B). The optical band-gap energies (E BG ) of the synthesized materials, which were calculated based on the Kubeka-Munk equation associating with Tauc plot, were also shown in Fig. 4 to further demonstrate their optical properties. It can be seen that the E BG of these WO 3 , Cu-WO 3 , Cu-WO 3 , 3Cu-WO 3 , 4Cu-WO 3 , and 5Cu-WO 3 materials were 2.72, 2.63, 2.58, 2.55, 2.52, and 2.51 eV, respectively. Thus, the E BG of the Cu-doped WO 3 materials were lower than that of the pure WO 3 . This was due to the effects of copper dopant, a d-transition metal, replaced certain tungsten components in the WO 3 lattice. When copper entered into the WO 3 lattice, 3d orbitals of the copper was lower than 5d orbitals of the tungsten, which form the WO 3 conduction band (Gao et al. 2021 , Naeimi et al. 2022 ). As a result, an intermediate band that is lower than the WO 3 conduction band was formed causing the E BG decreases in the Cu-WO 3 samples (Deb 1973 , Kramida &Shirai 2009 , Orgel 2004 , Rao et al. 2012 ). The newly created band also worked as an electron accepter/donor to minimize electron-hole recombination rate leading to the improvement in visible light absorption of the Cu-WO 3 samples (Fig. 3 A). When the copper content reached high levels (4 and 5% mole), however, the visible light absorption of the Cu-WO 3 was vaguely decreased (Fig. 3 A). As mentioned in the XRD and SEM results, above doping limitation, further use of the copper precursor generated CuO oxides. The formed CuO would gather into large particles distributing on the surface to prevent incident light interacting with WO 3 leading to decrease in light absorption (Chen et al. 2013 ). On the other hand, with the increase in Cu contents, the E BG of the doped materials tended to continuously decrease even with the high Cu content samples (4Cu-WO 3 and 5Cu-WO 3 ). After reaching doping limitation, Cu dopant would not further exist in the WO 3 lattice to narrow its energy band-gap. However, the energy band-gap of CuO oxide, which was approximately 2.1 eV, could interfere the energy band-gap of the Cu-WO 3 to continuously narrow their band-gap energies even with high Cu contents (Chen et al. 2018 , Kumar et al. 2020 ). 3.2. Tetracycline elimination The tetracycline elimination was carried out by replacing photocatalyst, while maintaining similar experimental conditions for each experiment, to determine the photocatalytic performance presented in Fig. 5 . In the first 120 minutes, through adsorption onto the material surface, a certain amount of tetracycline was eliminated. The equilibrium state was reached after approximately 60 minutes in the dark condition. Due to the high surface area, doped materials presented better tetracycline adsorption capacity than the pure WO 3 . The 5Cu-WO 3 , which exhibited the highest surface area, showed the highest tetracycline adsorption ability. On the other hand, without the presence of photocatalyst, the self-photodegradation of tetracycline would not be observed when the light source was provided. However, with the use of photocatalysts, great numbers of tetracycline were eliminated under irradiation of visible light. Under irradiation of a suitable light source, synthesized materials could attract free photons to stimulate electrons jump from their valence band (V band ) up to conduction band (C band ) while leaving holes at the V band . Tetracycline could be mineralized to CO 2 , H 2 O, and/or non-toxic secondary substances when it directly interacts with these holes. H 2 O could also react with these formed holes to generate • OH free radicals. The radicals also played a crucial role in tetracycline degrading/mineralizing. At the same time, photo-excited electrons in the C band would react with dissolved O 2 , which was absorbed onto the surface of synthesized materials, to produce • \({\text{O}}_{\text{2}}^{\text{-}}\) radicals. These radicals can be an intermediate substance to produce • OH radicals in the aqueous environment for the continuous tetracycline degradation process (Eq. 5–8). A possible mechanism for tetracycline elimination on the surface of doped and non-doped materials could be described by following equations: Synthesized WO 3 (or Cu-WO 3 ) + hν → h + + e – (Eq. 1) h + + Tetracycline → CO 2 + H 2 O (Eq. 2) h + + H 2 O → HO • + H + (Eq. 3) e – + O 2 → • \({\text{O}}_{\text{2}}^{\text{-}}\) (Eq. 4) • \({\text{O}}_{\text{2}}^{\text{-}}\) + H 2 O→ • O 2 H + – OH (Eq. 5) • O 2 H + H 2 O → H 2 O 2 + HO • (Eq. 6) 2 • O 2 H→ O 2 + H 2 O 2 (Eq. 7) H 2 O 2 + e – → HO • + OH – (Eq. 8) HO • + Tetracycline → CO 2 + H 2 O (Eq. 9) Figure 5 also demonstrated that Cu-doped WO 3 photocatalysts exhibited higher degradation performance than the pure WO 3 . It was due to Cu dopants successfully narrowed the energy band-gap and induced electron-hole separation efficiency of the WO 3 . Therefore, the Cu-WO 3 generated large amounts of electrons and holes for an effective tetracycline elimination process. Along multiple ratios of Cu dopants, the 3Cu-WO 3 , in which the Cu doping ratio was 3% mole, exhibited the highest elimination efficiency (79.52%). It can be seen that when the Cu dopant ratio surpassed 3%, the decomposition performance of doped material decreased. This was because the limitation of Cu doping into the WO 3 resulted in the CuO formation onto the surface of the WO 3 . The distribution of CuO on the WO 3 surface obscured incident light reaching to the WO 3 to reduce optical absorption for separation of electrons and holes of the material. Therefore, the photocatalytic degradation was decreased. Hence, the 3Cu-WO 3 exhibited the highest photocatalytic performance for tetracycline elimination. Finally, tetracycline elimination of the recycled 3Cu-WO 3 , which was presented in Fig. 6 A, indicated that the photocatalyst exhibited a constant photocatalytic performance over four cycles. The obtained XRD results of initial and recycled 3Cu-WO 3 were also presented in Fig. 6 B. The peaks in the Cu-WO 3 XRD pattern before it was utilized as a photocatalyst for the elimination of tetracycline were similarly identical to those of the pristine Cu-WO 3 . The results indicated the novel stability of the photocatalyst during tetracycline elimination. 4. Conclusions The study efficaciously doped Cu into WO 3 matrix to boost its photocatalysis for elimination of tetracycline. The doped Cu worked as nuclei for WO 3 crystallization leading to crystal size increase of the Cu-WO 3 . Thus, these WO 3 crystal was smaller than the Cu-WO 3 crystal. On the other hand, the doped Cu induced lattice deviation in the WO 3 . Therefore, the agglomeration of these deviated WO 3 crystals to large particles was greatly inhibited or WO 3 particles were greatly larger than the Cu-WO 3 particles. In addition, an intermediate level, which was lower than the WO 3 C band , was created by the Cu dopant resulting in band-gap energy decrease of the Cu-WO 3 material. The newly created level also worked as electron accepter/donor to reduce electron-hole recombination. Therefore, the Cu-WO 3 absorbed incident visible irradiation effectively to produce large amounts of electron-hole pairs for decomposition of tetracycline. The optimized Cu doping for maximum enhancement photocatalysis of the WO 3 was 3% mole. Above the ratio, the used Cu precursor formed CuO distributing on the WO 3 surface to eclipse incident light to the material. Thus, light absorption of the material was decreased resulting in low electron-hole production or photocatalytic degradation. Finally, the Cu-WO 3 exhibited novel stability during the tetracycline degradation. Declarations Acknowledgements This research is funded by Vietnam National Foundation for Science and Technology Development (NAFOSTED) under grant number 104.05-2021.89 - Ethical approval and consent to participate This study does not include any human or animal subjects. - Consent to Publish All authors agreed for publication. Authors Contributions: Nguyen Viet Khoa wrote the introduction, material synthesis, photocatalytic experiment, and recycling sections, conducted material synthesis and degradation experiment and revised the paper. Nguyen Thi Hanh designed the study, conducted materials synthesis and degradation experiments, reviewed and revised the paper. Nguyen Thuy Huong conducted material synthesis, SEM analysis and degradation experiment, wrote the related section. Phuong Thao contributed to material synthesis, conducted XRD analysis, wrote the related section. Thanh-Dong Pham conceived and designed the study, conducted degradation experiments, wrote the abstract, reviewed and revised the paper. Ha Minh Ngoc conducted UV–Vis analysis, wrote the related section. Nguyen Thi Dieu Cam conducted PL analysis, degradation experiments, wrote the related section. Nguyen Van Noi conducted BET and UV-Vis analysis, wrote the related section. - Funding This research is funded by Vietnam National Foundation for Science and Technology Development (NAFOSTED) under grant number 104.05-2021.89 - Competing interests All authors declare no competing interests References Ajel MK, Al-nayili A (2023): Synthesis, characterization of Ag-WO3/bentonite nanocomposites and their application in photocatalytic degradation of humic acid in water. Environmental Science and Pollution Research 30, 20775-20789 Assadi MHN, Hanaor DAH (2016): The effects of copper doping on photocatalytic activity at (101) planes of anatase TiO2: A theoretical study. 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Physica B: Condensed Matter 407, 593-597 Song H, Li Y, Lou Z, Xiao M, Hu L, Ye Z, Zhu L (2015): Synthesis of Fe-doped WO3 nanostructures with high visible-light-driven photocatalytic activities. Applied Catalysis B: Environmental 166-167, 112-120 Song X, Jo C, Zhou M (2022): Enhanced tetracycline removal using membrane-like air-cathode with high flux and anti-fouling performance in flow-through electro-filtration system. Water Research 224, 119057 Tang Z, Li H, Liu Y, Liang J, Liu J, Tang H, Wu Q, Jiang F, Jiang W (2023): Advanced electrochromic properties of Nb-doped WO3 inverse opal films in NIR region by slow photon effect-assisted enhancement of localized surface plasmon resonance. Applied Surface Science 622, 156802 Thanh Truc NT, Pham T-D, Van Thuan D, Son LT, Tran DT, Nguyen MV, Nguyen VN, Dang NM, Trang HT (2019): Superior activity of Cu-NiWO4/g-C3N4 Z direct system for photocatalytic decomposition of VOCs in aerosol under visible light. Journal of Alloys and Compounds 798, 12-18 Tri NLM, Duc DS, Van Thuan D, Tahtamouni TA, Pham T-D, Tran DT, Thi Phuong Le Chi N, Nguyen VN (2019): Superior photocatalytic activity of Cu doped NiWO4 for efficient degradation of benzene in air even under visible radiation. Chemical Physics 525, 110411 Wang H, Fang C, Wang Q, Chu Y, Song Y, Chen Y, Xue X (2018): Sorption of tetracycline on biochar derived from rice straw and swine manure. RSC Advances 8, 16260-16268 Wang J, Zhao C, Yuan S, Li X, Zhang J, Hu X, Lin H, Wu Y, He Y (2023): One-step fabrication of Cu-doped Bi2MoO6 microflower for enhancing performance in photocatalytic nitrogen fixation. Journal of Colloid and Interface Science 638, 427-438 Wu S, Hu H, Lin Y, Zhang J, Hu YH (2020): Visible light photocatalytic degradation of tetracycline over TiO2. Chemical Engineering Journal 382, 122842 Xiong T, Feng Q, Fang C, Chen R, Wang Y, Xu L, Liu C (2024): A novel ZnCo2O4/BiOBr p-n/Z-scheme heterojunction photocatalyst for enhancing photocatalytic activity. Environmental Science and Pollution Research 31, 26839-26854 Yang H, Ping Q, Zhang Y (2023): Highly efficient degradation of ofloxacin and diclofenac by composite photocatalyst aloe-emodin/PMMA. Environmental Science and Pollution Research 30, 72721-72740 Yao Y, Sang D, Zou L, Wang Q, Liu C (2021): A Review on the Properties and Applications of WO(3) Nanostructure-Based Optical and Electronic Devices. Nanomaterials (Basel) 11 Zhang H, Chen Y, Pan Y, Bao L, Yuan Y-J (2021): Hydrogen pressure-assisted rapid recombination of oxygen vacancies in WO3 nanosheets for enhanced N2 photofixation. Journal of Solid State Chemistry 303, 122520 Zhao B, Shao N, Chen X, Ma J, Gao Y, Chen X (2023): Construction of novel type II heterojunction WO3/Bi2WO6 and Z-scheme heterojunction CdS/Bi2WO6 photocatalysts with significantly enhanced photocatalytic activity for the degradation of rhodamine B and reduction of Cr(VI). Colloids and Surfaces A: Physicochemical and Engineering Aspects 663, 131072 Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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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-4373404","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":326973898,"identity":"cc88e918-0cd4-4e99-89ca-c56617b35509","order_by":0,"name":"Nguyen Viet Khoa","email":"","orcid":"","institution":"Vietnam National University Hanoi","correspondingAuthor":false,"prefix":"","firstName":"Nguyen","middleName":"Viet","lastName":"Khoa","suffix":""},{"id":326973899,"identity":"a784fc1a-d3c6-4dec-ba00-fdb3e705610c","order_by":1,"name":"Nguyen Thi Hanh","email":"","orcid":"","institution":"Vietnam National University Hanoi","correspondingAuthor":false,"prefix":"","firstName":"Nguyen","middleName":"Thi","lastName":"Hanh","suffix":""},{"id":326973900,"identity":"fbcde703-81a4-4434-b744-2d5e7b92f535","order_by":2,"name":"Nguyen Thuy Huong","email":"","orcid":"","institution":"Vietnam National University Hanoi","correspondingAuthor":false,"prefix":"","firstName":"Nguyen","middleName":"Thuy","lastName":"Huong","suffix":""},{"id":326973901,"identity":"c65d96ce-f1fe-428c-8933-62bdb0072efc","order_by":3,"name":"Phuong Thao","email":"","orcid":"","institution":"Vietnam National University Hanoi","correspondingAuthor":false,"prefix":"","firstName":"Phuong","middleName":"","lastName":"Thao","suffix":""},{"id":326973902,"identity":"4e78addc-8816-4a4e-ae61-287d981754f2","order_by":4,"name":"Thanh-Dong Pham","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA2klEQVRIie3OsQrCMBCA4ZZAXWJdr4M+QyRQCu3DtEtd1LmDYEDIVOnqYwi+QCVQl8O5o6NjwVXEiODY1k0wPxzk4D6IZZlMv1ipp8lgMnqvpB+xdxhxT3xDyFCmyb7sS9zTVl0pKvtQLyqwsjARsChbiYfnNIBMEb9epmDhTJNl3EpYPfcZQ+X4iD7YUiWCIusmiVSU5y/y6Ef45ShTYINcE6HJIG8nnv6PLTBicMp5EFczLruIqy9v9wzWxYZO62YVjgtC24nOgc8zfq1d9zrS9DgymUymf+4JOKtJrFhyQ9IAAAAASUVORK5CYII=","orcid":"","institution":"Vietnam National University Hanoi","correspondingAuthor":true,"prefix":"","firstName":"Thanh-Dong","middleName":"","lastName":"Pham","suffix":""},{"id":326973903,"identity":"dcb65954-2143-4b1f-a1bb-481056a796a6","order_by":5,"name":"Ha Minh Ngoc","email":"","orcid":"","institution":"Vietnam National University Hanoi","correspondingAuthor":false,"prefix":"","firstName":"Ha","middleName":"Minh","lastName":"Ngoc","suffix":""},{"id":326973904,"identity":"477178d9-44d5-4a16-a03c-a7d3ae3e0a9d","order_by":6,"name":"Nguyen Thi Dieu Cam","email":"","orcid":"","institution":"Quy Nhon University","correspondingAuthor":false,"prefix":"","firstName":"Nguyen","middleName":"Thi Dieu","lastName":"Cam","suffix":""},{"id":326973905,"identity":"1cfca23c-dce1-4fa0-a414-c9f2beac8b0a","order_by":7,"name":"Nguyen Van Noi","email":"","orcid":"","institution":"Vietnam National University Hanoi","correspondingAuthor":false,"prefix":"","firstName":"Nguyen","middleName":"Van","lastName":"Noi","suffix":""}],"badges":[],"createdAt":"2024-05-06 01:37:44","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4373404/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4373404/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":62001397,"identity":"9a00f458-bd4a-46bb-b160-db30b98082e4","added_by":"auto","created_at":"2024-08-08 05:58:59","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":91594,"visible":true,"origin":"","legend":"\u003cp\u003eXRD results of prepared WO\u003csub\u003e3\u003c/sub\u003e and Cu-WO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-4373404/v1/075b16e654c1da3375b0b678.png"},{"id":62002135,"identity":"1d2547e5-654a-4088-a14c-8c07101c6f73","added_by":"auto","created_at":"2024-08-08 06:06:59","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":198938,"visible":true,"origin":"","legend":"\u003cp\u003eWO\u003csub\u003e3\u003c/sub\u003e SEM image (A), 3Cu-WO\u003csub\u003e3\u003c/sub\u003e SEM image (B) and N\u003csub\u003e2\u003c/sub\u003e adsorption-desorption isotherms (C) of the WO\u003csub\u003e3 \u003c/sub\u003eand 3Cu-WO\u003csub\u003e3 \u003c/sub\u003ematerials\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-4373404/v1/81f1d7f70080886d0d865432.png"},{"id":62002134,"identity":"57e49558-3322-49b0-9e10-5c6122ca1339","added_by":"auto","created_at":"2024-08-08 06:06:59","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":84611,"visible":true,"origin":"","legend":"\u003cp\u003eUV-Vis (A) and PL spectra (B) of synthesized materials\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-4373404/v1/c07c53c1b8ecfa912486dee7.png"},{"id":62001402,"identity":"49a07264-8f59-4c1d-a752-cfa2c0d91157","added_by":"auto","created_at":"2024-08-08 05:58:59","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":73959,"visible":true,"origin":"","legend":"\u003cp\u003eTauc plots and calculated band-gap energies of synthesized materials\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-4373404/v1/a3874a5ce206af682f1bd790.png"},{"id":62001400,"identity":"a10ddd37-ac33-4bc6-8762-b07648f4af1d","added_by":"auto","created_at":"2024-08-08 05:58:59","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":84057,"visible":true,"origin":"","legend":"\u003cp\u003eTetracycline elimination by different photocatalysts under dark and light conditions\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-4373404/v1/373c3e7c1785ca2c9bfc1ddf.png"},{"id":62001399,"identity":"ff03977a-2058-47fe-b558-261ba35e18eb","added_by":"auto","created_at":"2024-08-08 05:58:59","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":46404,"visible":true,"origin":"","legend":"\u003cp\u003eTetracycline removal by recycled 3Cu-WO\u003csub\u003e3\u003c/sub\u003e (A) and XRD patterns of initial and recycled 3Cu-WO\u003csub\u003e3\u003c/sub\u003e (B)\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-4373404/v1/29adf76336021618d20a6d47.png"},{"id":69938858,"identity":"8e7954c5-77ee-44a8-9fea-dc67710b49a6","added_by":"auto","created_at":"2024-11-26 20:13:17","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1133594,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4373404/v1/fc64c631-9325-4d6a-9504-2099c90d77cd.pdf"}],"financialInterests":"","formattedTitle":"Investigation doping effects of Copper to enhance photocatalytic performance of Tungsten Trioxide for advanced Tetracycline elimination even under visible light","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eAntibiotics have always been an inseparable part of healthcare for humans and animals. However, enormous scientific evidences indicated that their convenient as well as indiscriminate antibiotic uses lead to their sharply increasing environmental occurrences resulting in multiple unintended consequences (Kraemer et al. \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2019\u003c/span\u003e, Larsson \u0026amp;Flach \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2022\u003c/span\u003e, Liu et al. \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2021\u003c/span\u003e, Martinez \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2009\u003c/span\u003e, Yang et al. \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Against both Gram(-) and Gram(+) bacteria, mycoplasma, parasites and fungus, Tetracycline (TC) as one of the primary antibiotic groups with broad spectrum activity, has been used regularly in veterinary treatment, human therapy purposes as well as agricultural sector (Gopal et al. \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). However, the antibiotic has been used extensively without any dosage regulation in most nations. More than 50% of used Tetracycline was excreted in the forms of feces and urine of the treated organisms (Hu et al. \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). The primary and secondary treatments in conventional wastewater treatment plans would be not sufficient for complete TC removal. Uncontrolled use and released TC, which is a persistent compound and could be transformed into even more harmful substances in natural biodegrading cycles, caused the spread of mutated bacteria, which can resist multiple antibiotics, leading to environmental and ecological damages as well as bioaccumulating in the food chain resulting in threatening human health. Thus, there is an urgent need to investigate a sustainable and advanced technology to completely eliminate Tetracycline as well as other antibiotics from the environment to overcome the threatening problem.\u003c/p\u003e \u003cp\u003eSeveral removal techniques, such as membrane filtration, adsorption onto the material, reverse osmosis, and advanced oxidation processes (ozonation, photolysis, and photocatalysis), have been researched thoroughly and applied to treat wastewater containing TC (Gopal et al. \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2020\u003c/span\u003e, Liu et al. \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2017\u003c/span\u003e, Song et al. \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2022\u003c/span\u003e, Wang et al. \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2018\u003c/span\u003e, Xiong et al. \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Among them, photocatalysis, in which photocatalyst would be excited by suitable incident light to release free radicals, such as HO˙, \u003csup\u003e\u0026minus;\u003c/sup\u003eO\u003csub\u003e2\u003c/sub\u003e˙, and HO\u003csub\u003e2\u003c/sub\u003e˙, for antibiotic degradation into simpler byproducts resulting in complete TC removal from wastewater, has been studied comprehensively as a promising removal technology (Cao et al. \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2019\u003c/span\u003e, L\u0026oacute;pez-Pe\u0026ntilde;alver et al. \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2010\u003c/span\u003e, Norvill et al. \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2017\u003c/span\u003e, Wu et al. \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). As a conventional photocatalyst, TiO\u003csub\u003e2\u003c/sub\u003e has been broadly utilized for elimination of numerous kinds of organic pollutants. Nevertheless, the used TiO\u003csub\u003e2\u003c/sub\u003e only showed good degradation efficiency under excitation of ultraviolet light (Jing et al. \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2023\u003c/span\u003e, Li et al. \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Only less than 5% of the solar light spectrum is ultraviolet light irradiation greatly restricting applications of the TiO\u003csub\u003e2\u003c/sub\u003e in practical systems. Therefore, it is particularly crucial to investigate a suitable photocatalyst effectively working under visible light, which accounts for approximately 44% of solar light (Luo et al. \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2023\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eCurrently, tungsten oxide (WO\u003csub\u003e3\u003c/sub\u003e), has received broad popularity because of its non-toxic, industrial-friendly cost, reasonable stability, and moderate band gap energy (\u0026sim;2.8 eV) (Ajel \u0026amp;Al-nayili \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2023\u003c/span\u003e, Yao et al. \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Previous literature reports demonstrated that the WO\u003csub\u003e3\u003c/sub\u003e has higher valence band potential than the requiring oxidation potential for hydroxyl radical formation (Tang et al. \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2023\u003c/span\u003e, Zhao et al. \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Hence, photo-generated holes, which were produced when the WO\u003csub\u003e3\u003c/sub\u003e was excited by the suitable incident light, effectively reacted with H\u003csub\u003e2\u003c/sub\u003eO to form hydroxyl radicals resulting in high organic pollutant degradation efficiencies. However, degradation efficiencies of the pure WO\u003csub\u003e3\u003c/sub\u003e would be halved due to its excessive electron-hole recombination, insufficient visible light absorption, and low surface area. Thus, numerous strategies, including micromorphology control, metal and/or non-metal doping, noble metal deposition, and heterojunction construction, have been researched to overcome one or all of these limitations. Among them, doping transitional metals, such as Ni, Fe, and Zn, into the lattice of the WO\u003csub\u003e3\u003c/sub\u003e greatly enhanced its photocatalytic performance (Naeimi et al. \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2022\u003c/span\u003e, Song et al. \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). For instance, Hui Song et al. have doped Fe successfully into the pure WO\u003csub\u003e3\u003c/sub\u003e lattice (Song et al. \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). The authors investigated that the phenomenal degrading performance by the Fe-doped WO\u003csub\u003e3\u003c/sub\u003e was approximately 93%, which was much higher than that by the pure WO\u003csub\u003e3\u003c/sub\u003e (~\u0026thinsp;10%).\u003c/p\u003e \u003cp\u003eCopper \u0026ndash; Cu, a transition metal with low cost, has been widely used as a dopant to incorporate into various photocatalyst lattices, such as CoFe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e, TiO\u003csub\u003e2\u003c/sub\u003e, Bi\u003csub\u003e2\u003c/sub\u003eMoO\u003csub\u003e6\u003c/sub\u003e, and BiVO\u003csub\u003e4\u003c/sub\u003e, to enhance their photocatalytic performance (Bakhtiarnia et al. \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2023\u003c/span\u003e, Mo \u0026amp;Zhang \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2024\u003c/span\u003e, Wang et al. \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). In our earlier researches, Cu was successfully doped into TiO\u003csub\u003e2\u003c/sub\u003e, ZnO, and NiWO\u003csub\u003e4\u003c/sub\u003e to improve their photocatalysis for elimination of various organic pollutants, and even converted CO\u003csub\u003e2\u003c/sub\u003e into valuable products (Hanh et al. \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2019\u003c/span\u003e, Pham \u0026amp;Lee \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2015\u003c/span\u003e, Thanh Truc et al. \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2019\u003c/span\u003e, Tri et al. \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). The obtained results indicated that due to similarity in ionic radii, Cu dopants replaced certain Ti, Zn, and W ions in the TiO\u003csub\u003e2\u003c/sub\u003e, ZnO, and NiWO\u003csub\u003e4\u003c/sub\u003e lattices, respectively. By doping into the TiO\u003csub\u003e2\u003c/sub\u003e (ZnO or CuWO\u003csub\u003e4\u003c/sub\u003e) lattices, Cu dopants effectively decreased their band gap energies. With the outer electron shell configuration of 3d\u003csup\u003e9\u003c/sup\u003e, Cu dopant could perform as an electron receptor to minimize electron-hole recombination rate of these materials resulting in their photocatalytic enhancement. Based on obtained results from previous studies, this study is designed for investigating Cu as a promising dopant to dope into WO\u003csub\u003e3\u003c/sub\u003e lattice to enhance photocatalysis of the WO\u003csub\u003e3\u003c/sub\u003e before being used for the tetracycline removal process in aqueous environment.\u003c/p\u003e"},{"header":"2. Experiments","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e1.1. Material preparation\u003c/h2\u003e \u003cp\u003eTo obtain a homogeneous solution for synthesis of WO\u003csub\u003e3\u003c/sub\u003e, double distilled water was used to dissolve sodium tungstate dihydrate (Na\u003csub\u003e2\u003c/sub\u003eWO\u003csub\u003e4\u003c/sub\u003e.2H\u003csub\u003e2\u003c/sub\u003eO) before stirring for 30 minutes. Then, a 3M HCl solution was slowly dropped into the solution for pH control to 1 before monitoring its temperature to 80 ℃ for the next 2 hours. An achieved yellow suspension was then centrifuged and washed by distilled water. The obtained precipitate was continuously air dried for 24 hours and calcinated for next 2 hours at 500 ℃ to achieve WO\u003csub\u003e3\u003c/sub\u003e.\u003c/p\u003e \u003cp\u003eCu-doped WO\u003csub\u003e3\u003c/sub\u003e was also prepared via co-precipitation method. Copper chloride (CuCl\u003csub\u003e2\u003c/sub\u003e) solution was added into the prepared solution of sodium tungstate before stirring for 30 minutes. The above used HCl solution (3M) was also dropped to the solution for pH control to 1. Then, temperature of the obtained suspension was controlled to 80 ℃ for 2h. Centrifugation was also used to separate the obtained yellow precipitate of the suspension. Double distilled water was also used to wash the separated precipitate before air drying for 24 hours and calcinating at 500 ℃ for 2 hours to achieve Cu-doped WO\u003csub\u003e3\u003c/sub\u003e (Cu-WO\u003csub\u003e3\u003c/sub\u003e) samples. The amounts of used CuCl\u003csub\u003e2\u003c/sub\u003e solution were measured to obtain 1Cu-WO\u003csub\u003e3\u003c/sub\u003e, 2Cu-WO\u003csub\u003e3\u003c/sub\u003e, 3Cu-WO\u003csub\u003e3\u003c/sub\u003e, 4Cu-WO\u003csub\u003e3\u003c/sub\u003e and 5Cu-WO\u003csub\u003e3\u003c/sub\u003e samples, which the Cu/WO\u003csub\u003e3\u003c/sub\u003e ratios were 1, 2, 3, 4, and 5% mole, respectively.\u003c/p\u003e \u003cp\u003eAn AXS D8 X-ray diffractometer (XRD) was used to investigate crystalline structure of synthesized materials. At the same periods, morphology as well as elemental mapping of the prepared materials were examined by a S-4800 scaning eletron microscope (SEM) equipping with an HD-2700 energy dispesive X-ray detetor (EDX). To analyze optical properties of synthesized materials, an UV-3101PC ultra violet \u0026ndash; visible absorption spectrometer (UV-Vis) was applied.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e1.2. Photocatalysis test\u003c/h2\u003e \u003cp\u003eTo investigate photocatalytic efficiency, 50 mg of the prepared material was put into tetracycline solution (200 mL, 10 ppm), then stirred in the dark for 2 hours before being irradiated with a 35 W LED lamp to activate the photocatalysis. Then, for every 30 mins passing, 10 mL sample was taken quickly to centrifugate at the speed of 12000 rpm for 15 mins. A PTFE filter was continuously used to eliminate the remaining material after centrifugation. Then, the filtered solution was examined by an ultraviolet-visible spectrometer at 368.5 nm to detect remaining tetracycline contents. Recycling experiments were also carried out to investigate the material\u0026rsquo;s stability as well as recovery ability after being used for the tetracycline elimination process. In a distinctive experiment, the used photocatalyst for tetracycline decomposition for 4 hours, was filtrated to collect before washing with distilled water. Then, the obtained sample was dried in a vacuum dark chamber at 150 \u003csup\u003eo\u003c/sup\u003eC for 24 hours before being continuously used for the next tetracycline elimination cycle.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Result and Discussion","content":"\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e3.1. Material characteristics\u003c/h2\u003e \u003cdiv id=\"Sec7\" class=\"Section3\"\u003e \u003ch2\u003e3.1.1. Doped photocatalyst\u003c/h2\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e presented XRD results of synthesized WO\u003csub\u003e3\u003c/sub\u003e and Cu-WO\u003csub\u003e3\u003c/sub\u003e samples. This showed that the prepared WO\u003csub\u003e3\u003c/sub\u003e material has XRD pattern similarity to the standard WO\u003csub\u003e3\u003c/sub\u003e (PDF Card No. 1528915) with a monoclinic phase. Peaks locating at 2\u003cem\u003eθ\u003c/em\u003e\u0026thinsp;=\u0026thinsp;20.38\u0026deg;, 23.08\u0026deg;, 23.56\u0026deg;, 24.32\u0026deg;, 26.6\u0026deg;, 28.58\u0026deg;, 33.27\u0026deg;, 34.16\u0026deg;, 35.62\u0026deg;, 41.82\u0026deg;, 44.95\u0026deg;, 47.28\u0026deg;, 48.30\u0026deg;, 50\u0026deg;, 53.48\u0026deg;, 54.2\u0026deg;, 54.92\u0026deg;, 55.9\u0026deg;, 58.21\u0026deg;, 60.43\u0026deg;, 62.26\u0026deg; are well identified, which corresponded to (11\u0026thinsp;\u0026minus;\u0026thinsp;1), (002), (020), (200), (120), (11\u0026thinsp;\u0026minus;\u0026thinsp;2), (022), (220), (122), (222), (132), (004), (140), (024), (042), (240), (420), (332), (242), and (340) planes. In comparison to the WO\u003csub\u003e3\u003c/sub\u003e XRD pattern, these Cu-WO\u003csub\u003e3\u003c/sub\u003e XRD patterns displayed both peak intensity increases and sharpness. The XRD patterns of CuWO\u003csub\u003e3\u003c/sub\u003e samples also revealed a slightly left shifted. The influents of Cu dopants distorting WO\u003csub\u003e3\u003c/sub\u003e lattice parameters were investigated using the Scherrer formula and Miller indices (hkl) (Deepa \u0026amp;Rajendran \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2018\u003c/span\u003e, Prabhu et al. \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). The obtained results were presented in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, which shown that the Cu-WO\u003csub\u003e3\u003c/sub\u003e materials revealed an increase in crystal sizes as compared to the pure WO\u003csub\u003e3\u003c/sub\u003e. The phenomenon was because of the Cu dopants, which acted as nuclei for WO\u003csub\u003e3\u003c/sub\u003e crystallization during the synthesizing process (Carson et al. \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). Thus, the crystallization process would be greatly enhanced with the aid of Cu nuclei resulting in an increase in growth and size of formed crystals. Furthermore, significant lattice parameter differences were observed between the doped materials and the pure WO\u003csub\u003e3\u003c/sub\u003e (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The interference of Cu dopants, which replaced numerous W elements in the WO\u003csub\u003e3\u003c/sub\u003e lattice, could be the cause of the divergence. The replacement caused the lattice disorder because Cu\u003csup\u003e2+\u003c/sup\u003e and W\u003csup\u003e6+\u003c/sup\u003e have different ionic radii (Assadi \u0026amp;Hanaor \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2016\u003c/span\u003e, Bakhtiarnia et al. \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2023\u003c/span\u003e, Khalid et al. \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2022\u003c/span\u003e, Naeimi et al. \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). Hence, the acquired XRD pattern outcomes designated that Cu was effectively doped into the crystal structure of WO\u003csub\u003e3\u003c/sub\u003e. Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e also indicated that the lattice parameter deviation in Cu-WO\u003csub\u003e3\u003c/sub\u003e materials tends to increase within copper dopant ratios increase up to 3% in mole. Nevertheless, further deviation could not be seen with further copper doping ratio increases from 4 to 5% samples. This was due to the doping of copper into the WO\u003csub\u003e3\u003c/sub\u003e matrix reached limitation. Excessive copper precursor distributed on surface of the WO\u003csub\u003e3\u003c/sub\u003e instead of doping into its lattice. The distributed copper could be oxidized to CuO during material calcination in the air. Therefore, low peaks at 35.58 and 38.92\u003csup\u003eo\u003c/sup\u003e corresponding to CuO components were observed in the XRD patterns of the synthesized 4Cu-WO\u003csub\u003e3\u003c/sub\u003e and 5Cu-WO\u003csub\u003e3\u003c/sub\u003e.\u003c/p\u003e \u003cp\u003e \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\u003eLattice parameters and crystal sizes of prepared photocatalysts\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=\"char\" char=\".\" 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\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eSamples\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eCrystal sizes (nm)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"4\" nameend=\"c6\" namest=\"c3\"\u003e \u003cp\u003eLattice parameters\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eSurface area\u003c/p\u003e \u003cp\u003e(m\u003csup\u003e2\u003c/sup\u003e/g)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003ea (\u0026Aring;)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eb (\u0026Aring;)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003ec (\u0026Aring;)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eCell-volume (\u0026Aring;\u003csup\u003e3\u003c/sup\u003e)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eWO\u003c/b\u003e\u003csub\u003e\u003cb\u003e3\u003c/b\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e22.95\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e7.2999\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e7.5305\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e7.6790\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e422.0770\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e7.6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003e1Cu-WO\u003c/b\u003e\u003csub\u003e\u003cb\u003e3\u003c/b\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e27.04\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e7.3118\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e7.5368\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e7.6855\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e423.4754\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e10.52\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003e2Cu-WO\u003c/b\u003e\u003csub\u003e\u003cb\u003e3\u003c/b\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e29.36\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e7.3118\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e7.5431\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e7.6987\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e424.8979\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e13.37\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003e3Cu-WO\u003c/b\u003e\u003csub\u003e\u003cb\u003e3\u003c/b\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e30.65\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e7.3266\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e7.5526\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e7.7085\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e426.4962\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e15.16\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003e4Cu-WO\u003c/b\u003e\u003csub\u003e\u003cb\u003e3\u003c/b\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e30.78\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e7.3281\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e7.5538\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e7.7099\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e426.7272\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e15.82\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003e5Cu-WO\u003c/b\u003e\u003csub\u003e\u003cb\u003e3\u003c/b\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e30.86\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e7.3289\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e7.5548\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e7.7112\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e426.9058\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e16.26\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=\"Sec8\" class=\"Section3\"\u003e \u003ch2\u003e3.1.2. Morphology\u003c/h2\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e presented the SEM images to describe surface morphology of synthesized WO\u003csub\u003e3\u003c/sub\u003e (2A) and 3Cu-WO\u003csub\u003e3\u003c/sub\u003e (2B) materials. At first, SEM images proved that synthesized materials were nanoparticles. Later, SEM images indicated that WO\u003csub\u003e3\u003c/sub\u003e particles, which are approximately 200 nm, were larger than Cu-WO\u003csub\u003e3\u003c/sub\u003e particles, which were approximately 80 nm. This was because Cu dopants defected the WO\u003csub\u003e3\u003c/sub\u003e lattice causing its disorder. Thus, the agglomeration of these disordered WO\u003csub\u003e3\u003c/sub\u003e crystals to form large particles was inhibited resulting in a decrease in particle sizes of Cu-WO\u003csub\u003e3\u003c/sub\u003e materials in comparison to the pure WO\u003csub\u003e3\u003c/sub\u003e. To further determine surface morphology, the prepared WO\u003csub\u003e3\u003c/sub\u003e and Cu-WO\u003csub\u003e3\u003c/sub\u003e photocatalysts were analyzed via nitrogen adsorption/desorption isotherms. The calculated BET surface areas of the prepared materials were also presented in the Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. Additionally, Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eC displayed the obtained isotherms for WO\u003csub\u003e3\u003c/sub\u003e and 3Cu-WO\u003csub\u003e3\u003c/sub\u003e materials. Firstly, isotherms of both WO\u003csub\u003e3\u003c/sub\u003e and 3Cu-WO\u003csub\u003e3\u003c/sub\u003e were hysteresis loops indicating that they were mesoporous materials. In addition, the WO\u003csub\u003e3\u003c/sub\u003e and 3Cu-WO\u003csub\u003e3\u003c/sub\u003e isotherms also showed H2 inferring hysteresis types. It signified that the surface of WO\u003csub\u003e3\u003c/sub\u003e and Cu-WO\u003csub\u003e3\u003c/sub\u003e samples contained pores shaped like ink-bottle and randomly folded sheets (Zhang et al. \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). The estimated surface area of pure WO\u003csub\u003e3\u003c/sub\u003e sample was greatly smaller than those of Cu-WO\u003csub\u003e3\u003c/sub\u003e samples (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The increasing in surface area of the Cu-WO\u003csub\u003e3\u003c/sub\u003e materials in comparison to the WO\u003csub\u003e3\u003c/sub\u003e was firstly because the particles of the Cu-WO\u003csub\u003e3\u003c/sub\u003e was substantially smaller than the WO\u003csub\u003e3\u003c/sub\u003e particles. Secondly, the distribution of pore sizes in WO\u003csub\u003e3\u003c/sub\u003e and 3Cu-WO\u003csub\u003e3\u003c/sub\u003e materials, showing in the inset Figure in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eC, indicated the fact that the surface area increases of the doped materials were caused by the pore number increases or by the Cu dopants, which interfered mesopore formation on the surface of the WO\u003csub\u003e3\u003c/sub\u003e material. Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e also indicated that among these Cu-WO\u003csub\u003e3\u003c/sub\u003e samples, the 5Cu-WO\u003csub\u003e3\u003c/sub\u003e sample exhibited the highest BET surface area. This could be due to CuO oxides distributing on the WO\u003csub\u003e3\u003c/sub\u003e surface induced mesopore formation.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section3\"\u003e \u003ch2\u003e3.1.3. Optical characteristics\u003c/h2\u003e \u003cp\u003eThe remarkable visible light absorption enhancement and red shifted in absorption edges could be seen in the optical absorption spectra of Cu-WO\u003csub\u003e3\u003c/sub\u003e in comparison to that of pure WO\u003csub\u003e3\u003c/sub\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eA). In the PL spectra, the peaks of the Cu doped WO\u003csub\u003e3\u003c/sub\u003e materials were also significantly lower than that of the pure WO\u003csub\u003e3\u003c/sub\u003e also demonstrating that the electron-hole recombination of the doped materials was greatly prevented (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eB). The optical band-gap energies (E\u003csub\u003eBG\u003c/sub\u003e) of the synthesized materials, which were calculated based on the Kubeka-Munk equation associating with Tauc plot, were also shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e to further demonstrate their optical properties. It can be seen that the E\u003csub\u003eBG\u003c/sub\u003e of these WO\u003csub\u003e3\u003c/sub\u003e, Cu-WO\u003csub\u003e3\u003c/sub\u003e, Cu-WO\u003csub\u003e3\u003c/sub\u003e, 3Cu-WO\u003csub\u003e3\u003c/sub\u003e, 4Cu-WO\u003csub\u003e3\u003c/sub\u003e, and 5Cu-WO\u003csub\u003e3\u003c/sub\u003e materials were 2.72, 2.63, 2.58, 2.55, 2.52, and 2.51 eV, respectively. Thus, the E\u003csub\u003eBG\u003c/sub\u003e of the Cu-doped WO\u003csub\u003e3\u003c/sub\u003e materials were lower than that of the pure WO\u003csub\u003e3\u003c/sub\u003e. This was due to the effects of copper dopant, a d-transition metal, replaced certain tungsten components in the WO\u003csub\u003e3\u003c/sub\u003e lattice. When copper entered into the WO\u003csub\u003e3\u003c/sub\u003e lattice, 3d orbitals of the copper was lower than 5d orbitals of the tungsten, which form the WO\u003csub\u003e3\u003c/sub\u003e conduction band (Gao et al. \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2021\u003c/span\u003e, Naeimi et al. \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). As a result, an intermediate band that is lower than the WO\u003csub\u003e3\u003c/sub\u003e conduction band was formed causing the E\u003csub\u003eBG\u003c/sub\u003e decreases in the Cu-WO\u003csub\u003e3\u003c/sub\u003e samples (Deb \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e1973\u003c/span\u003e, Kramida \u0026amp;Shirai \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2009\u003c/span\u003e, Orgel \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2004\u003c/span\u003e, Rao et al. \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). The newly created band also worked as an electron accepter/donor to minimize electron-hole recombination rate leading to the improvement in visible light absorption of the Cu-WO\u003csub\u003e3\u003c/sub\u003e samples (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eA). When the copper content reached high levels (4 and 5% mole), however, the visible light absorption of the Cu-WO\u003csub\u003e3\u003c/sub\u003e was vaguely decreased (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eA). As mentioned in the XRD and SEM results, above doping limitation, further use of the copper precursor generated CuO oxides. The formed CuO would gather into large particles distributing on the surface to prevent incident light interacting with WO\u003csub\u003e3\u003c/sub\u003e leading to decrease in light absorption (Chen et al. \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2013\u003c/span\u003e). On the other hand, with the increase in Cu contents, the E\u003csub\u003eBG\u003c/sub\u003e of the doped materials tended to continuously decrease even with the high Cu content samples (4Cu-WO\u003csub\u003e3\u003c/sub\u003e and 5Cu-WO\u003csub\u003e3\u003c/sub\u003e). After reaching doping limitation, Cu dopant would not further exist in the WO\u003csub\u003e3\u003c/sub\u003e lattice to narrow its energy band-gap. However, the energy band-gap of CuO oxide, which was approximately 2.1 eV, could interfere the energy band-gap of the Cu-WO\u003csub\u003e3\u003c/sub\u003e to continuously narrow their band-gap energies even with high Cu contents (Chen et al. \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2018\u003c/span\u003e, Kumar et al. \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2020\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e3.2. Tetracycline elimination\u003c/h2\u003e \u003cp\u003eThe tetracycline elimination was carried out by replacing photocatalyst, while maintaining similar experimental conditions for each experiment, to determine the photocatalytic performance presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e. In the first 120 minutes, through adsorption onto the material surface, a certain amount of tetracycline was eliminated. The equilibrium state was reached after approximately 60 minutes in the dark condition. Due to the high surface area, doped materials presented better tetracycline adsorption capacity than the pure WO\u003csub\u003e3\u003c/sub\u003e. The 5Cu-WO\u003csub\u003e3\u003c/sub\u003e, which exhibited the highest surface area, showed the highest tetracycline adsorption ability. On the other hand, without the presence of photocatalyst, the self-photodegradation of tetracycline would not be observed when the light source was provided. However, with the use of photocatalysts, great numbers of tetracycline were eliminated under irradiation of visible light. Under irradiation of a suitable light source, synthesized materials could attract free photons to stimulate electrons jump from their valence band (V\u003csub\u003eband\u003c/sub\u003e) up to conduction band (C\u003csub\u003eband\u003c/sub\u003e) while leaving holes at the V\u003csub\u003eband\u003c/sub\u003e. Tetracycline could be mineralized to CO\u003csub\u003e2\u003c/sub\u003e, H\u003csub\u003e2\u003c/sub\u003eO, and/or non-toxic secondary substances when it directly interacts with these holes. H\u003csub\u003e2\u003c/sub\u003eO could also react with these formed holes to generate \u003csup\u003e\u0026bull;\u003c/sup\u003eOH free radicals. The radicals also played a crucial role in tetracycline degrading/mineralizing. At the same time, photo-excited electrons in the C\u003csub\u003eband\u003c/sub\u003e would react with dissolved O\u003csub\u003e2\u003c/sub\u003e, which was absorbed onto the surface of synthesized materials, to produce \u003csup\u003e\u0026bull;\u003c/sup\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({\\text{O}}_{\\text{2}}^{\\text{-}}\\)\u003c/span\u003e\u003c/span\u003e radicals. These radicals can be an intermediate substance to produce \u003csup\u003e\u0026bull;\u003c/sup\u003eOH radicals in the aqueous environment for the continuous tetracycline degradation process (Eq.\u0026nbsp;5\u0026ndash;8). A possible mechanism for tetracycline elimination on the surface of doped and non-doped materials could be described by following equations:\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Taba\" border=\"1\"\u003e \u003ccolgroup cols=\"2\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSynthesized WO\u003csub\u003e3\u003c/sub\u003e (or Cu-WO\u003csub\u003e3\u003c/sub\u003e)\u0026thinsp;+\u0026thinsp;hν \u0026rarr; h\u003csup\u003e+\u003c/sup\u003e + e\u003csup\u003e\u0026ndash;\u003c/sup\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e(Eq.\u0026nbsp;1)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eh\u003csup\u003e+\u003c/sup\u003e + Tetracycline \u0026rarr; CO\u003csub\u003e2\u003c/sub\u003e\u0026thinsp;+\u0026thinsp;H\u003csub\u003e2\u003c/sub\u003eO\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e(Eq.\u0026nbsp;2)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eh\u003csup\u003e+\u003c/sup\u003e + H\u003csub\u003e2\u003c/sub\u003eO \u0026rarr; HO\u003csup\u003e\u0026bull;\u003c/sup\u003e + H\u003csup\u003e+\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e(Eq.\u0026nbsp;3)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ee\u003csup\u003e\u0026ndash;\u003c/sup\u003e + O\u003csub\u003e2\u003c/sub\u003e \u0026rarr; \u003csup\u003e\u0026bull;\u003c/sup\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({\\text{O}}_{\\text{2}}^{\\text{-}}\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e(Eq.\u0026nbsp;4)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003csup\u003e\u0026bull;\u003c/sup\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({\\text{O}}_{\\text{2}}^{\\text{-}}\\)\u003c/span\u003e\u003c/span\u003e + H\u003csub\u003e2\u003c/sub\u003eO\u0026rarr;\u003csup\u003e\u0026bull;\u003c/sup\u003eO\u003csub\u003e2\u003c/sub\u003eH + \u003csup\u003e\u0026ndash;\u003c/sup\u003eOH\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e(Eq.\u0026nbsp;5)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003csup\u003e\u0026bull;\u003c/sup\u003eO\u003csub\u003e2\u003c/sub\u003eH\u0026thinsp;+\u0026thinsp;H\u003csub\u003e2\u003c/sub\u003eO \u0026rarr; H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e + HO\u003csup\u003e\u0026bull;\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e(Eq.\u0026nbsp;6)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2\u003csup\u003e\u0026bull;\u003c/sup\u003eO\u003csub\u003e2\u003c/sub\u003eH\u0026rarr; O\u003csub\u003e2\u003c/sub\u003e\u0026thinsp;+\u0026thinsp;H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e(Eq.\u0026nbsp;7)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eH\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e\u0026thinsp;+\u0026thinsp;e\u003csup\u003e\u0026ndash;\u003c/sup\u003e \u0026rarr; HO\u003csup\u003e\u0026bull;\u003c/sup\u003e + OH\u003csup\u003e\u0026ndash;\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e(Eq.\u0026nbsp;8)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHO\u003csup\u003e\u0026bull;\u003c/sup\u003e + Tetracycline \u0026rarr; CO\u003csub\u003e2\u003c/sub\u003e\u0026thinsp;+\u0026thinsp;H\u003csub\u003e2\u003c/sub\u003eO\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e(Eq.\u0026nbsp;9)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e also demonstrated that Cu-doped WO\u003csub\u003e3\u003c/sub\u003e photocatalysts exhibited higher degradation performance than the pure WO\u003csub\u003e3\u003c/sub\u003e. It was due to Cu dopants successfully narrowed the energy band-gap and induced electron-hole separation efficiency of the WO\u003csub\u003e3\u003c/sub\u003e. Therefore, the Cu-WO\u003csub\u003e3\u003c/sub\u003e generated large amounts of electrons and holes for an effective tetracycline elimination process. Along multiple ratios of Cu dopants, the 3Cu-WO\u003csub\u003e3\u003c/sub\u003e, in which the Cu doping ratio was 3% mole, exhibited the highest elimination efficiency (79.52%). It can be seen that when the Cu dopant ratio surpassed 3%, the decomposition performance of doped material decreased. This was because the limitation of Cu doping into the WO\u003csub\u003e3\u003c/sub\u003e resulted in the CuO formation onto the surface of the WO\u003csub\u003e3\u003c/sub\u003e. The distribution of CuO on the WO\u003csub\u003e3\u003c/sub\u003e surface obscured incident light reaching to the WO\u003csub\u003e3\u003c/sub\u003e to reduce optical absorption for separation of electrons and holes of the material. Therefore, the photocatalytic degradation was decreased. Hence, the 3Cu-WO\u003csub\u003e3\u003c/sub\u003e exhibited the highest photocatalytic performance for tetracycline elimination. Finally, tetracycline elimination of the recycled 3Cu-WO\u003csub\u003e3\u003c/sub\u003e, which was presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eA, indicated that the photocatalyst exhibited a constant photocatalytic performance over four cycles. The obtained XRD results of initial and recycled 3Cu-WO\u003csub\u003e3\u003c/sub\u003e were also presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eB. The peaks in the Cu-WO\u003csub\u003e3\u003c/sub\u003e XRD pattern before it was utilized as a photocatalyst for the elimination of tetracycline were similarly identical to those of the pristine Cu-WO\u003csub\u003e3\u003c/sub\u003e. The results indicated the novel stability of the photocatalyst during tetracycline elimination.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"4. Conclusions","content":"\u003cp\u003eThe study efficaciously doped Cu into WO\u003csub\u003e3\u003c/sub\u003e matrix to boost its photocatalysis for elimination of tetracycline. The doped Cu worked as nuclei for WO\u003csub\u003e3\u003c/sub\u003e crystallization leading to crystal size increase of the Cu-WO\u003csub\u003e3\u003c/sub\u003e. Thus, these WO\u003csub\u003e3\u003c/sub\u003e crystal was smaller than the Cu-WO\u003csub\u003e3\u003c/sub\u003e crystal. On the other hand, the doped Cu induced lattice deviation in the WO\u003csub\u003e3\u003c/sub\u003e. Therefore, the agglomeration of these deviated WO\u003csub\u003e3\u003c/sub\u003e crystals to large particles was greatly inhibited or WO\u003csub\u003e3\u003c/sub\u003e particles were greatly larger than the Cu-WO\u003csub\u003e3\u003c/sub\u003e particles. In addition, an intermediate level, which was lower than the WO\u003csub\u003e3\u003c/sub\u003e C\u003csub\u003eband\u003c/sub\u003e, was created by the Cu dopant resulting in band-gap energy decrease of the Cu-WO\u003csub\u003e3\u003c/sub\u003e material. The newly created level also worked as electron accepter/donor to reduce electron-hole recombination. Therefore, the Cu-WO\u003csub\u003e3\u003c/sub\u003e absorbed incident visible irradiation effectively to produce large amounts of electron-hole pairs for decomposition of tetracycline. The optimized Cu doping for maximum enhancement photocatalysis of the WO\u003csub\u003e3\u003c/sub\u003e was 3% mole. Above the ratio, the used Cu precursor formed CuO distributing on the WO\u003csub\u003e3\u003c/sub\u003e surface to eclipse incident light to the material. Thus, light absorption of the material was decreased resulting in low electron-hole production or photocatalytic degradation. Finally, the Cu-WO\u003csub\u003e3\u003c/sub\u003e exhibited novel stability during the tetracycline degradation.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis research is funded by Vietnam National Foundation for Science and Technology Development (NAFOSTED) under grant number 104.05-2021.89\u003c/p\u003e\n\u003cp\u003e- Ethical approval and consent to participate This study does not include any human or animal subjects.\u003c/p\u003e\n\u003cp\u003e- Consent to Publish All authors agreed for publication.\u003c/p\u003e\n\u003cp\u003eAuthors Contributions:\u0026nbsp;\u003cstrong\u003eNguyen Viet Khoa\u0026nbsp;\u003c/strong\u003ewrote the introduction, material synthesis, photocatalytic experiment, and recycling sections, conducted material synthesis and degradation experiment and revised the paper.\u0026nbsp;\u003cstrong\u003eNguyen Thi Hanh\u0026nbsp;\u003c/strong\u003edesigned the study, conducted materials synthesis and degradation experiments, reviewed and revised the paper.\u0026nbsp;\u003cstrong\u003eNguyen Thuy Huong\u003c/strong\u003e\u003csup\u003e\u0026nbsp;\u003c/sup\u003econducted material synthesis, SEM analysis and degradation experiment, wrote the related section.\u0026nbsp;\u003cstrong\u003ePhuong Thao\u003c/strong\u003e contributed to material synthesis,\u0026nbsp;conducted XRD analysis, wrote the related section.\u0026nbsp;\u003cstrong\u003eThanh-Dong Pham\u003c/strong\u003e conceived and designed the study, conducted degradation experiments, wrote the abstract, reviewed and revised the paper.\u0026nbsp;\u003cstrong\u003eHa Minh Ngoc\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003econducted UV\u0026ndash;Vis analysis, wrote the related section.\u0026nbsp;\u003cstrong\u003eNguyen Thi Dieu Cam\u003c/strong\u003e conducted PL analysis, degradation experiments, wrote the related section.\u0026nbsp;\u003cstrong\u003eNguyen Van Noi\u003c/strong\u003e conducted BET and UV-Vis analysis, wrote the related section.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e- Funding\u0026nbsp;This research is funded by Vietnam National Foundation for Science and Technology Development (NAFOSTED) under grant number 104.05-2021.89\u003c/p\u003e\n\u003cp\u003e- Competing interests All authors declare no competing interests\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAjel MK, Al-nayili A (2023): Synthesis, characterization of Ag-WO3/bentonite nanocomposites and their application in photocatalytic degradation of humic acid in water. 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Colloids and Surfaces A: Physicochemical and Engineering Aspects 663, 131072\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":"Cu dopant, WO3, Photocatalysis, Tetracycline removal, Recycling","lastPublishedDoi":"10.21203/rs.3.rs-4373404/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4373404/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe goal of the research was to improve photocatalytic activity of WO\u003csub\u003e3\u003c/sub\u003e by Cu doping to use for tetracycline decomposition. Firstly, the Cu dopant worked as nuclei for the crystallization of WO\u003csub\u003e3\u003c/sub\u003e leading to an increase in growth and sizes of formed crystals. However, the incorporation of Cu dopants in the WO\u003csub\u003e3\u003c/sub\u003e induced significant deviation into the WO\u003csub\u003e3\u003c/sub\u003e lattice inhibiting agglomeration of the WO\u003csub\u003e3\u003c/sub\u003e crystals to form large particles. Therefore, the crystal sizes of Cu-WO\u003csub\u003e3\u003c/sub\u003e were bigger than the WO\u003csub\u003e3\u003c/sub\u003e crystals, however, the Cu-WO\u003csub\u003e3\u003c/sub\u003e particles compared to WO\u003csub\u003e3\u003c/sub\u003e particles were smaller. By existing in the WO\u003csub\u003e3\u003c/sub\u003e lattice, the Cu dopant created an intermediate band to decrease band-gap energy and to boost electron-hole separation of the WO\u003csub\u003e3\u003c/sub\u003e. Therefore, the synthesized Cu-WO\u003csub\u003e3\u003c/sub\u003e effectively generated large electrons and holes for the decomposition of tetracycline under visible light excitation. The study investigated that 3Cu-WO\u003csub\u003e3\u003c/sub\u003e, in which the Cu doping ratio was 3% mole, showed the highest tetracycline decomposition efficiency (\u0026sim;79.5%). This was due to the doping of Cu into the WO\u003csub\u003e3\u003c/sub\u003e lattice reached a limit, excess that limitation, Cu precursor formed CuO distributing on the WO\u003csub\u003e3\u003c/sub\u003e surface to eclipse light reaching the material leading to decrease in electron-hole separation rate due to limited light absorption or decrease in photocatalytic degradation. Finally, the Cu-WO\u003csub\u003e3\u003c/sub\u003e exhibited novel stability during the degradation of tetracycline.\u003c/p\u003e","manuscriptTitle":"Investigation doping effects of Copper to enhance photocatalytic performance of Tungsten Trioxide for advanced Tetracycline elimination even under visible light","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-08-08 05:58:54","doi":"10.21203/rs.3.rs-4373404/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":"d798fcfb-1fe6-4dac-aa37-c35aaafac8bd","owner":[],"postedDate":"August 8th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2024-11-26T20:05:06+00:00","versionOfRecord":[],"versionCreatedAt":"2024-08-08 05:58:54","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4373404","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4373404","identity":"rs-4373404","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}