Study On The Catalytic Degradation Of BPA In Heterogeneous Fenton System By Landfill Leachate Coagulant Sludge Biochar

Advanced oxidation technology based on sulfate radical has the characteristics of high treatment efficiency and short cycle,and showed incomparable advantages in removing trace endocrine disruptors from water.In this paper,a variety of biochar materials were prepared from the concentrated sludge of landfill leachate by oxygen-limited pyrolysis.The crystal structure,functional groups,surface morphology and chemical composition of these materials were analyzed by XRD,FTIR,XPS and FESEM-EDS characterization methods.Taking bisphenol A（BPA）,a typical endocrine disruptor,as the target pollutant,the adsorption capacity of biochar and its activation capacity for perbisulfate（PMS）were investigated.By optimizing the reaction conditions and using free radical quenching agent to identify the species of reactive oxygen species in the system,the possible activation mechanism was proposed.The research results could provide a new direction for the removal of micro endocrine disruptors in water,and a theoretical basis for the comprehensive utilization of the concentrated landfill leachate and its coagulant sludge.Firstly,the concentrated landfill leachate was pretreated with polyferric sulfate（PFS）,and a variety of biochar（BC）materials were prepared from the coagulant sludge.The adsorption capacity of BC materials on BPA was investigated.Meanwhile,the materials were characterized by XRD,FTIR and FESEM.It is confirmed that the adsorption capacity of BC material decreases with the increase of pyrolysis temperature and residence time.In this experiment,BC3002 material has the best adsorption performance for BPA;In an acidic environment,the BPA adsorption removal effect was better,which is mainly related to the existence of pollutants.Through kinetic fitting analysis,it was confirmed that the adsorption behavior is an exothermic reaction,and the adsorption capacity decreases with the increase of temperature.Secondly,a heterogeneous Fenton system was constructed by combining BC material with PMS to remove BPA from simulated wastewater.The effect of reaction conditions on the removal efficiency of BPA and the stability of BC material were investigated.The results show that the activation ability of BC material increases with the increase of pyrolysis temperature and residence time.In this experiment,BC7504material has the best activation performance for PMS.Through the free radical quenching experiment,it was found that·OH and SO₄^-·existed in both systems.After four consecutive reactions,the BC3002 material could still maintain a considerable stability during the process of effectively activating PMS to degrade BPA.However,the ferromagnetic components contained on the surface of the BC7504 material have been significantly reduced,resulting in a decrease in its activation efficiency for PMS.Last but not least,with garbage landfill site leachate actual coagulation sludge as raw material,a variety of sludge biochar（SBC）materials was prepared under the condition of different pyrolysis.Then,the SBC materials of BPA in simulated wastewater adsorption performance and its activation on the PMS performance was examined.Further more,a series of characterization of SBC materials before and after the reaction was made to elucidate the possible catalytic reaction mechanism.The results show that the raw material composition,pyrolysis temperature and residence time have great influence on the properties and reaction capacity of biochar materials.In this experiment,SBC3002 material has the best adsorption and removal effect on BPA,while SBC4502 material has the best activation performance on PMS,which is mainly due to the difference in the number and types of active points on the surface of the material due to different pyrolysis temperatures.Through the free radical quenching experiment,it is known that·OH and SO₄^-·exist in both systems,and·OH played a leading role in BPA degradation process.After four successive reactions,both SBC3002and SBC4502 maintained a satisfactory activation capacity and stability.The products in the reaction process were identified by LC-MS,the possible degradation pathway of BPA and the activation mechanism of biochar on PMS were further proposed.