Fabrication of ZnAl-LDH mixed metal-oxide composites for photocatalytic degradation of 4-chlorophenol

• Published in: Environmental science and pollution research international 2022-06, Vol.29 (26), p.39441-39450
• Main Authors: Xia, Guanghua, Zheng, Yumei, Sun, Zhiyin, Xia, Shengjie, Ni, Zheming, Yao, Jiachao
• Format: Article
• Language: English
• Subjects: Aquatic Pollution; Atmospheric Protection/Air Quality Control/Air Pollution; Catalytic activity; Cerium oxides; Chlorophenol; Decomposition reactions; Density functional theory; Earth and Environmental Science; Ecotoxicology; Environment; Environmental Chemistry; Environmental Health; Environmental science; Fabrication; Fourier transforms; Free radicals; Hybrid composites; Hydroxides; Hydroxyl radicals; Infrared spectroscopy; Intermediates; Metal oxides; Performance degradation; Photocatalysis; Photodegradation; Reaction kinetics; Reaction mechanisms; Recyclability; Research Article; Spectroscopy; Spectrum analysis; Synthesis; Theoretical density; Tin dioxide; Waste Water Technology; Wastewater; Water Management; Water Pollution Control; X-ray diffraction
• ISSN: 0944-1344; 1614-7499
• DOI: 10.1007/s11356-022-18989-3

In this work, two different types of ZnAl-layered double hydroxide (LDH) mixed metal-oxide composites (CeO 2 and SnO 2 ) were synthesized and applied for the photodegradation of 4-chlorophenol (4-CP) in wastewater. The fabricated CeO 2 /ZnAl-LDH and SnO 2 /ZnAl-LDH were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, UV–visible diffuse reflectance spectroscopy (UV–vis DRS), and theoretical density functional theory (DFT) calculations, suggesting that the band gaps of the synthesized hybrid composites were much lower than those of traditional ZnAl-LDH. In addition, the photocatalytic activity for 4-CP degradation and reaction kinetics were investigated to evaluate the catalytic behavior of the prepared composites. The results indicated that the photocatalytic process in this case followed a pseudo-first-order kinetic model, and SnO 2 /ZnAl-LDH illustrated the optimum performance for 4-CP degradation with an efficiency of 95.2% due to its stability and recyclability. Additionally, the reaction mechanism of 4-CP photodegradation was studied over SnO 2 /ZnAl-LDH; it presented that 4-CP could be oxidized by hydroxyl radicals, holes, and superoxide radicals, where hydroxyl radicals were identified as the dominant active species during the degradation process. Finally, decomposition intermediates were measured to deduce the reaction pathway of 4-CP, and three tentative pathways were proposed and discussed.