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Effects of excess sludge composting process, environmentally persistent free radicals, and microplastics on antibiotics degradation efficiency of aging biochar
Summary
Researchers examined how microplastics (specifically polystyrene) added to sewage sludge affect a biochar's long-term ability to degrade antibiotics in compost environments. After composting, the antibiotic-degrading efficiency of biochar decreased — and decreased more when polystyrene microplastics were present — primarily because composting reduced the reactive free radicals that drive antibiotic breakdown. This matters because biochar is increasingly proposed as a tool for removing antibiotic contaminants from waste streams, and microplastic co-contamination of sludge could undermine this function over time.
Simulation of microbial aging biochar in compost is an important index for evaluating the biochar degradation efficiency of antibiotics. In this study, biochar was prepared by adding microplastics (MPs) to sludge, and the degradation effect of biochar/(peroxymonosulfate, PMS) on antibiotics was evaluated during the compost aging process of biochar. After the compost aging of biochars, the antibiotic degradation efficiency of HPBC500, HPBC500 + polystyrene (PS), HPBC900/PMS, and HPBC900 + PS/PMS decreased by 6.47, 15.2, 10.16, and 10.33 %, respectively. Environmentally persistent free radicals (EPFRs) and defect structure were the main contributors to the activation of PMS. EPFRs produced through PS pyrolysis of biochar exhibited strong reactivity but poor stability during the degradation of antibiotics. Biochar enhanced the growth of microorganisms in compost but reduced its specific surface area. The antibiotic degradation efficiency of the biochar was positively correlated with the concentration of EPFRs. This study elucidated the durability of different biochar toward antibiotic degradation.