Degradation of phenol and sulfamethoxazole with persulfate and ozone with nano‐MnO₂–biochar composites

BACKGROUND In this study, nano‐MnO 2 –biochar composites were synthesized as catalysts to promote the oxidation of recalcitrant organic contaminants. MnO 2 nanoparticles coated on biochar were hypothesized to enhance the oxidation of phenol and sulfamethoxazole (SMX) using ozone and/or persulfate. RESULTS The optimal percentage of MnO 2 coating on the surface of biochar was determined, and the synthesis of nano‐MnO 2 ‐coated biochar was confirmed via scanning electron microscopy–energy‐dispersive X‐ray spectroscopy (EDS), X‐ray diffraction and EDS line mapping analyses. Compared with oxidation using ozone or persulfate in the presence of either nano‐MnO 2 or biochar, the synthesized nano‐MnO 2 –biochar composite markedly enhanced the oxidation of phenol and SMX. This was probably due to the spreading of MnO 2 nanorods on the surface of biochar and the synergistic involvement of nano‐MnO 2 and biochar as catalysts. X‐ray photoelectron spectroscopy analysis confirmed the involvement of Mn 3+ in MnO 2 to promote oxidation using ozone or persulfate. The coexistence of ozone and persulfate could also promote oxidation. Hydroxyl radicals (OH • ) and persulfate radicals (SO 4 −• ) were major reactive oxygen species for ozone and persulfate systems, respectively. CONCLUSION Results suggest that the synthesized nano‐MnO 2 –biochar composites may be effective catalysts for various types of advanced oxidation processes in environmental remediation.