Promoting charge separation of biochar-based Zn-TiO2/pBC in the presence of ZnO for efficient sulfamethoxazole photodegradation under visible light irradiation.

A novel and effective photocatalyst namely titanium dioxide doped with zinc elements stacked on reed straw biochar which was pretreated by acid (Zn-TiO2/pBC) with visible light response was successfully prepared by a simple modified sol-gel method firstly. The prepared samples were characterized by scanning microscopy (SEM), energy dispersive X-ray spectrum (EDS), X-ray diffraction (XRD), nitrogen adsorption-desorption (BET) and UV-Vis diffuse reflectance spectra (DRS). The photocatalytic activity of Zn-TiO2/pBC was further investigated through the photodegradation of sulfamethoxazole (SMX). Compared with TiO2 and TiO2/pBC, Zn-TiO2/pBC had better photocatalytic activity under visible light due to zinc elements effectively inhibiting the agglomeration of TiO2 and hindering the combination of photogenerated electrons and holes. The removal rate of SMX could reach 81.21%, which was 1.37 times higher than that of TiO2/pBC(300). Three common anions (SO42-, Cl-, NO3-) existing in the Yellow River exhibited detrimental effects on the SMX photodegradation to a certain degree. It might mainly occurred hydroxylation, cleavage of SN bond and opening of isoxazole ring reactions during the photodegradation process of SMX. Meanwhile, there might be four main degradation pathways proposed throw the LC/MS/MS analysis. Finally, good reusability and stability illustrated Zn-TiO2/pBC owned good practicality and feasibility for removal of organic pollutants in environment remediation area.