Regeneration of granular activated carbon adsorbent by peroxymonosulfate activation with MnO2/MnFe2O4

The regeneration of spent adsorbent is crucial in terms of environmental and economic aspects. In this study, MnO2/MnFe2O4 was synthesized by an impregnation-precipitation method and investigated as a perox-ymonosulfate (PMS) catalyst for the regeneration of granular activated carbon (GAC) after adsorption of ofloxacin (OFL). MnO2/MnFe2O4 exhibited high catalytic activity for the regeneration of GAC with PMS, and the adsorbed OFL was effectively removed from GAC surface. Singlet oxygen was found to be the dominant reactive species in this process, while O-2(center dot-) and SO4 center dot- participated in the degradation of intermediates. At neural pH, the regeneration efficiency of the spent GAC after the adsorption of OFL, tetracycline hydrochloride, ciprofloxacin and methylene blue reached 100 %, 100 %, 87.2 % and 84.2 %, respectively. MnO2/MnFe2O4 and GAC exhibited good stability and reusability in this process, and the regeneration efficiency was still above 90 % in the fifth cycle. The results suggest the potential application of PMS activation with magnetic catalyst in the regeneration of GAC after adsorption of organic pollutants.