posted on 2019-08-06, 15:41authored byWeihang 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.