Solid-phase fabrication of TiO2/Chitosan-biochar composites with superior UV–vis light driven photocatalytic degradation performance

Superior degradation of organic dyes in biochar-based semiconductor systems has recently been reported, demonstrating a broad application prospect in pollution control. In this paper, mesoporous TiO2/Chitosan-biochar (TiO2/CS-biochar) composite with Ti3+ and oxygen vacancies (OVs) defects was fabricated by a facile solid-phase co-calcination technique. The as-prepared TiO2/CS-biochar composites exhibited excellent and durable UV–vis light photocatalytic activity for the degradation of rhodamine B (RhB) aqueous solution, and the degradation rate constant was more than thirty times higher than that of pristine TiO2. The photocatalytic performance primarily depends on the CS-biochar content, photocatalyst dosage and RhB concentration, especially the CS-biochar content has a vital effect on the photocatalytic performance. The TiO2/CS-biochar (15 wt%) sample showed the best photocatalytic performance and could almost completely degrade RhB solution at higher concentrations. Furthermore, the possible photocatalytic mechanism of RhB over TiO2/CS-biochar was proposed based on the results of active species trapping experiment, electron spin-resonance spectroscopy (ESR) and high-performance liquid chromatography-mass spectrometry (HPLC-MS) techniques. The present work provides a novel idea for the preparation of biochar-based semiconductor composites with enhanced photocatalytic performance by solid phase co-calcination method.