Removal of triclosan via sorption and redox reactions in the presence of nano-MnO₂-biochar composites

To improve the removal of triclosan in groundwater and soil with nano-MnO₂ and biochar, a novel nano-MnO₂-biochar composite is synthesized, and its applicability to the removal of triclosan under anaerobic conditions is examined via batch experiments. Compared to either MnO₂ or biochar alone (84% and 67% of triclosan), the as-fabricated nano-MnO₂-biochar composite exhibits markedly enhanced triclosan removal via sorption and chemical reactions, showing complete removal in 12 h in the presence of 10 g of the synthesized nano-MnO₂-biochar composite in 200 mL of solution. Under the given conditions, the release of chloride in solution, responsible for 34.6% of initial chlorine in triclosan indicates the dechlorination of triclosan and is supported by liquid chromatography-mass spectrometry analysis. The oxidation of Mn³⁺ to Mn⁴⁺ in MnO₂, as confirmed by X-ray photoelectron spectroscopy, along with the formation of Mn²⁺ in solution, demonstrate that redox reactions are involved in the removal of triclosan by the nano-MnO₂-biochar composite. The present results support the applicability of the nano-MnO₂-biochar composite for the removal of triclosan or other organic contaminants in subsurface environments.