Cu2O/Ag-coated wood-based biochar composites for efficient adsorption/photocatalysis synergistic degradation of high-concentration azo dyes

In order to effectively eliminate organic azo dyes with high concentrations from aqueous environments, novel adsorption/photocatalysis composites were prepared using Cu2O/Ag-coated carriers based on renewable wood-based biochar (MBC). The adsorption process of the prepared MBC@Cu2O/Ag-3 under electrostatic attraction, hydrogen bonding, and complexation effects was conformed to the proposed second-order kinetic model, and the total sorption capacity of Congo red (CR) and methyl orange (MO) reached 264.55 and 178.63 mg g−1, respectively. Moreover, the coordinated interaction of MBC, Cu2O, and Ag enhanced the visible light absorptivity, which further facilitated the effective dissociation of light-generated electrons from holes. The removal rates of CR and MO by MBC@Cu2O/Ag-3 in the presence of visible light were up to 98.4 % and 97.8 %, respectively. In addition, free radical capture and electron spin resonance (ESR) spectroscopy analyses indicated that superoxide (·O2-) and hydroxyl (·OH) radicals were major activators during the photocatalytic progression, and the adsorption/photocatalysis mechanism was elucidated through a series of characterization experiments. This work shows that the utilization of natural biomass materials for the preparation of adsorption/photocatalysis composites with high added value can significantly contribute to water environmental protection and sustainable development.