One-step conversion of chemical excess sludge into functional catalyst to activate peroxymonosulfate for sulfamethoxazole degradation: Performance and mechanisms

The safe disposal of excess sludge generated from chemical wastewater treatment processes has attracted worldwide concern because of its high yield and toxicity. In our work, purified terephthalic acid excess sludgederived biochar (PTABC) was prepared via one-step pyrolysis without additives. The prepared catalyst was demonstrated to degrade sulfamethoxazole (SMX) via the activation of peroxymonosulfate (PMS). The inhibitory effects of anions were negligible. The reactive oxygen species were investigated based on the radical scavenging experiments and electron paramagnetic resonance technique. Additionally, the electron transfer process was investigated via electrochemical measurements. The results show that the non-radical pathways take a leading role in the degradation of SMX and the corresponding contributions of sulfate radical (SO4 center dot-), hydroxyl radical (center dot OH) and non-radical pathways in PTABC-700/PMS system for SMX degradation were 12.59%, 3.28%, and 84.13%, respectively. Active sites of PTABC-700 responsible for SMX degradation were also proposed. Overall, this study provides a promising strategy for converting excess sludge into functional catalysts and achieving treatment of SMX-contaminated wastewater.