Facile synthesis of ternary Ag/AgBr-Ag2CO3 hybrids with enhanced photocatalytic removal of elemental mercury driven by visible light

Abstract

A novel technique for photocatalytic removal of elemental mercury (Hg0) using visible-light-driven Ag/AgBr-Ag2CO3 hybrids was proposed. The ternary Ag/AgBr-Ag2CO3 hybrids were synthesized by a simple modified co-precipitation method and characterized by N2 adsorption-desorption, scanning electron microscope (SEM), X-ray diffraction (XRD), UV–vis diffused reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS) and electron spin resonance (ESR) techniques. The effects of AgBr content, fluorescent lamp (FSL) irradiation, solution temperature, SO2 and NO on Hg0 removal were investigated in detail. Furthermore, a possible reaction mechanism for higher Hg0 removal was proposed, and the simultaneous removal of Hg0, SO2 and NO was studied. The results showed that a high efficiency of Hg0 removal was obtained by using Ag/AgBr-Ag2CO3 hybrids under fluorescent lamp irradiation. The AgBr content, FSL irradiation, solution temperature, and SO2 all exhibited significant effects on Hg0 removal, while NO had slight effect on Hg0 removal. The addition of Ca(OH)2 demonstrated a little impact on Hg0 removal and could significantly improve the SO2-resistance performance of Ag/AgBr(0.7)-Ag2CO3 hybrid. The characterization results exhibited that hydroxyl radical (OH), superoxide radical (O2−), hole (h+), and Br0, were reactive species responsible for removing Hg0, and the h+ played a key role in Hg0 removal.