Photocatalytic performance of pyrochar and hydrochar in heterojunction photocatalyst for organic pollutants degradation: Activity comparison and mechanism insight

Biochar-based photocatalysts have attracted widespread attention for the remediation of organic pollutants in water. Herein, we have successfully prepared Bi2WO6/TiO2 heterojunction photocatalysts modified by pyrochar (HC) and hydrochar (PC) to illustrate the role of two different biochar in the system. HC had a higher O elemental content and a larger specific surface area compared to PC. Under the visible light irradiation, PC with persistent radicals could facilitate the production of ·OH during the photocatalytic reaction, while the HC promoted the production of ·O2– due to the presence of oxygen-containing functional groups, which made the Bi2WO6/TiO2/HC exhibit superior photocatalytic property for sulfathiazole (STZ) degradation. The results of characterization revealed that PC could act as an electron shuttle to facilitate photo-excited electron transfer. For HC, the oxygen-containing functional groups (OFGs) could act as photosensitizers while the particles with rod structure function as an electron carrier, which could synergistically promote the photocatalytic degradation of sulfathiazole with Bi2WO6/TiO2 heterojunction. Surprisingly, the real water experiments, luminescent bacterial test, and Toxicity Estimation Software Tool program indicated that Bi2WO6/TiO2/HC and Bi2WO6/TiO2/PC exhibited excellent practicality and reduced toxicity, which could provide a prospering strategy and insight into the design of efficient biochar-based photocatalysts for environmental remediation.