Performance and mechanism of biochar-coupled BiVO4 photocatalyst on the degradation of sulfanilamide

The construction of a low-cost and efficient novel photocatalyst is extremely important for the treatment of refractory wastewater. In this work, biochar-coupled BiVO4 (CBi) photocatalysts are synthesized using a hydrothermal method. These photocatalysts are then characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), transition electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), ultraviolet visible diffuse reflection spectroscopy (UV-Vis-DRS), and photoluminescence (PL). The photocatalytic performance was also evaluated using the degradation and mineralization of sulfaniamide (4-aminobenzene sulfonamide, SA) under visible light irradiation. The results indicated that the CBi photocatalysts showed larger surface areas, stronger absorption abilities, higher separation efficiencies of photogenerated electrons and holes, and powerful transfer abilities of photogenerated electrons than the photocatalyst without biochar (CBi-0%). The CBi photocatalyst with the 20 wt% biochar (CBi-20%) exhibited an optimal photodegradation ability for SA. The degradation rate of SA was approximately 97.0% after 7 h of visible light irradiation, and the removal rate of total organic carbon (TOC) was as high as 83.4%, indicating an excellent mineralization ability. In addition, the CBi-20% photocatalyst obtained the highest mineralization rate of organic nitrogen (92.7%) and organic sulfur compounds (75.8%). Furthermore, spectroscopic techniques revealed more information regarding the degradation of the benzene ring and fluorescent groups. The fluorescence intensity and UV254 of SA were reduced by 96.5%% and 90.0%, respectively, which provided specific evidence of the potential photodegradation mechanism.