Facile synthesis of ball-milling and oxalic acid co-modified sludge biochar to efficiently activate peroxymonosulfate for sulfamethoxazole degradation: 1O2 and surface-bound radicals

A novel approach of ball milling and oxalic acid was employed to modify sludge-based biochar (BOSBC) to boost its activation performance for peroxymonosulfate (PMS) towards efficient degradation of sulfamethoxazole (SMX). 98.6% of SMX was eliminated by PMS/BOSBC system within 60 min. Furthermore, PMS/BOSBC system was capable of maintaining high removal rates for SMX (>88.8%) in a wide pH range from 3 to 9, and displayed a high tolerance to background electrolytes including inorganic ions and humic acid (HA). Quenching experiments, electron paramagnetic resonance (EPR) analysis, in-situ Raman characterization and PMS decomposition experiments confirmed that the non-radicals of O-1(2) and surface-bound radicals were the main contributors to SMX degradation by PMS/BOSBC system. The results of ecotoxicity assessment illustrated that all transformed products (TPs) generated in PMS/BOSBC system were less toxic than that of SMX. After five reuse cycles, PMS/ BOSBC system still maintained a high removal rate for SMX (77.8%). Additionally, PMS/BOSBC system exhibited excellent degradation performance for SMX in various real waters (Yangtze River water (76.5%), lake water (74.1%), tap water (86.5%), and drinking water (98.1%)). Overall, this study provided novel insights on non-metal modification for sludge-based biochar and non-radical mechanism, and offered a feasible approach for municipal sludge disposal.

Automated summary

A novel approach using ball milling and oxalic acid to modify sludge-based biochar was found to enhance its activation performance for degrading sulfamethoxazole. The system showed high removal rates for sulfamethoxazole at different pH levels and had good tolerance to background electrolytes. Non-radicals and surface-bound radicals were identified as the main contributors to the degradation process. The transformed products generated in the system were less toxic than sulfamethoxazole. After multiple reuse cycles, the system maintained a high removal rate. This study provides valuable insights for the treatment of municipal sludge.