The Study About The Mechanisms Of Biochar-Mediated Fenton-Like Systems In The Treatment Of Wastewater Contaminated With Antibiotics

More and more pollution events caused by antibiotics in the environment have attracted mang attentions in recent years.How to deal with the residues of antibiotics in the environment efficiently and environmentally has become a hot topic in the field of environmental governance.Biochar,a green material pyrolyzed from common solid waste,possesses high catalytic potential in the removal of refractory pollutants from water due to its persistent free radicals?PFRs?.In this study,biochar-mediated Fenton-like systems were used to treat the wastewater contaminated by antibiotics,and achieved good results.Meanwhile,the reaction mechanism and influencing factors of the biochar-mediated Fenton-like systems were also investigated.The main contents of this study are as follows:?1?Swine manure biochar?SBC?,pyrolyzed from the most common solid waste,were utilized in Fenton-like systems to remove sulfamethazine?SMT?and achieved good results which the best removal rate can over 80%in 30 min.Adsorption experiments demonstrated that SBC possesses the poor SMT adsorption capacity due to its mineral surfaces and pore-filling effect was the main mechanism for SMT sorption on the SBC.Electron Paramagnetic Resonance?EPR?and XPS analysis revealed that there were oxygen-centered persistent free radicals?PFRs?and carbon-centered PFRs with an adjacent oxygen atom existed in SBC while oxygen-centered PFRs played a major role in the catalytic process and had a trend to convert to carbon-centered PFRs after the reaction.It was found that the electron transfer pathways were the most likely catalytic mechanism of SBC and contribution of·OH was dominant through Electron capture experiments and Linear sweep voltammetry?LSV?measurements.Proposed degradation pathways of SMT in SBC/H₂O₂ systems were also elucidated.Moreover,the acidic or alkaline condition can promote the catalytic ability of SBC while dissolved salts like NaCl had a dual effect on the SMT degradation owing to its different concentrations.Real wastewater application suggested that SBC600/H₂O₂ system possess excellent catalytic efficiency and good adaptability.?2?The influences of biomass types?bamboo,corn stalk,and pig manure?and its compositions?metals and phenolic compounds?on the formation of PFRs in biochar were investigated by electron paramagnetic resonance?EPR?.It was found that the amounts of PFRs in biochar would decrease sharply with the decrease of the initial metals and phenolic compounds existed in biomass,and the effect of metals contents on PFRs formation was much greater than that of phenolic compounds contents.This finding was supported by the results obtained from elemental analysis and molar H/C analysis of three types of biochar,which suggested that pig-manure biochar?PM500?had the highest concentrations of PFRs of 14.13×10¹88 spins/g due to the high content of metals and phenolic compounds in pig manure.All the three biochar/H₂O₂ systems can remove tetracycline efficiently,and the EPR trapping experiment as well as Linear sweep voltammetry?LSV?measurements in biochar/H₂O₂ systems showed that·OH was the dominant reactive radical and electrons transfer pathways might be responsible for the activation of H₂O₂ by biochar.Possible degradation pathways of the tetracycline in biochar/H₂O₂ systems were also proposed.Besides,high degradation efficiency and good stability were observed in real wastewater application of the PM500/H₂O₂ system.These findings provided a novel and high practicability reuse process of swine manure and a clearer insight into the formation mechanisms of PFRs in biochar.And a better strategy for biochar preparation and application in Fenton-like system was also present.