A novel pomegranate peel-derived biochar for highly efficient removal of sulfamethoxazole by activation of peroxymonosulfate through a non-radical pathway

The selection of biomass waste as a raw material for the preparation of metal-free catalysts for the activation of peroxymonosulfate (PMS) for the degradation of organic pollutants is a promising "waste-to-waste" treatment approach. In this study, high-efficiency and environmentally friendly pomegranate peel-derived biochar (PPCs) was prepared by activation and pyrolysis of waste pomegranate peels and used as metal-free catalysts to activate PMS for degradation of sulfamethoxazole (SMX). Batch experiments showed that different activators affected the activation efficiency of PPCs for PMS. Compared with ZnCl2 and KHCO3, KOH possesses excellent corrosion micropore-making function. In addition, under the activation of KOH, the PPC3 sample owned high CO and graphite N ratios and good electrochemical properties, which led to stronger catalytic degradation ability of SMX. In the PPC3/PMS system, 10 mg/L of SMX was completely removed within 15 min with a mineralization rate of 85.39% and possible degradation pathways for SMX were proposed. Quenching experiments and EPR tests showed that 1O2 exerted a major contribution in the catalytic system, with •OH playing a secondary role, and electrochemical measurements indicated that non-radical electron transfer was also involved in the catalytic process. This non-radical pathway enables the catalytic system to exhibit excellent performance even in a wide pH range and in the presence of multiple anions. This study not only demonstrates a novel biochar for activation of PMS as an efficient catalyst, but also provides a pathway for value-added reuse of pomegranate peels.