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Fabrication of 3D Sponge@AgBr-AgCl/Ag and Tubular Photoreactor for Continuous Wastewater Purification under Sunlight Irradiation

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posted on 06.08.2019, 15:41 by Weihang Kong, Shilin Wang, Di Wu, Cuirong Chen, Yusheng Luo, Yuetian Pei, Baozhu Tian, Jinlong Zhang
Semiconductor photocatalysis is promising for the remediation of organic pollutants in environmental wastewater. At present, the main bottlenecks of relative research lie in how to more effectively improve the sunlight activity of photocatalysts and realize their reutilization. Herein, we assembled AgBr-AgCl/Ag on the skeletons of melamine sponge (MS) by immobilizing Ag nanowires (NWs) on MS skeletons, transferring Ag into AgBr-AgCl, and further reducing part Ag+ into metallic Ag. The microstructures of MS@AgBr-AgCl/Ag were characterized by the means of scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). It was found that AgBr-AgCl/Ag NWs were successfully loaded on the skeletons of MS to form a 3D structure, and there existed a composite structure between AgBr and AgCl. The transient photocurrents and electrochemical impedance analyses revealed that the AgBr-AgCl composite structure effectively decreased the impedance of charge carrier transfer, and consequently MS@AgBr-AgCl/Ag NWs displayed much higher photocurrent than MS@AgBr/Ag NWs and MS@AgCl/Ag NWs. The photocatalytic activities of the samples were evaluated by degrading antibiotic sulfadiazine (SD) and five organic dyes (fuchsin basic, methyl orange, acid orange 7, malachite green, and rhodamine B). Beneficial from the excellent visible-light response and charge carrier separation properties, MS@AgBr-AgCl/Ag NWs displayed the optimal photocatalytic activity among these samples. Radical trapping experiments demonstrated that O2 and h+ are the main reactive species responsible for organic contaminant degradation. Based on the results of high performance liquid chromatography–mass spectra (HPLC-MS), the possible structures of the main intermediates toward SD degradation were proposed. By filling MS@AgBr-AgCl/Ag NWs into glass tubes and connecting them together, we fabricated a tubular fixed-bed photoreactor for continuous wastewater purification. Overall, this work provides a reference for constructing visible light driven photocatalysts and fixed-bed photoreactors used for the environmental wastewater purification under sunlight irradiation.