Metal-free activation of persulfates by corn stalk biochar for the degradation of antibiotic norfloxacin: Activation factors and degradation mechanism.

This study investigated the degradation of norfloxacin by persulfate activated with corn stalk biochar. The results demonstrate that corn stalk biochar is a green and low-cost carbon material with excellent catalytic activity for the metal-free activation of persulfate to degrade norfloxacin. The removal rate of norfloxacin increased with the increase in the dosage of persulfate, but the increased ratio gradually decreased. With alcohols and phenols as free radical trapping agents, it was determined that norfloxacin degradation by SO- 4· and HO· in the biochar/persulfate system occurred mainly on the surface or boundary layer of biochar. pH has an important effect on norfloxacin degradation in the biochar/persulfate system. Norfloxacin degradation performances under different initial pH conditions are decreased according to the following order: (initial pH 6.5) > (initial pH 3.4) > (initial pH 10.6). The effects of pH on norfloxacin degradation in the biochar/persulfate system was mainly realized through affecting norfloxacin adsorption on corn stalk biochar surface.