Mediation of rhodamine B photodegradation by biochar

Significant degradation of organic contaminants in biochar sorption systems has recently been reported, demonstrating a promising potential application of biochar in pollution control. We hypothesized that the degradation of organic chemicals by biochar may be further enhanced under irradiation by UV light due to the photocatalytic activities of carbonaceous materials. Our results confirmed that UV conditions increased the degradation of rhodamine B (RhB) by up to three times compared to dark conditions. Washing biochar with ultrapure water further increased RhB photodegradation by up to ten times. This photodegradation increase was the highest for biochar produced at 1000 °C. HF treatment and the addition of biochar supernatant did not increase RhB photodegradation. Therefore, the biochar properties mediating RhB photodegradation may be related to solid particles, mostly the combination of graphite structures and organic functional groups. Based on XPS and FTIR analysis, we propose that the quinoid CO in biochar may play an essential role in RhB photodegradation. Further research on identifying the photoactive components of biochar will be fundamental for improved biochar manufacture and application.