Study On The Performance Of Modified Sludge Biochar Adsorption And Coupled Persulfate For The Degradation Of Chlorinated Organic Pollutants

2,4-Dichlorophenol（2,4-DCP）is a typical chlorinated organic compound widely present in the aqueous environment,with strong stability and difficult degradability,posing a serious threat to human health and environmental safety.Persulfate（PS）oxidation is an efficient and thorough treatment technology for 2,4-DCP,but its activation mode and oxidation mechanism still need to be investigated in depth.Given the large amount of municipal sludge produced in China and the urgent need for rational treatment and disposal,this study prepared sludge biochar and its modified materials through high-temperature pyrolysis of municipal sludge and investigated their adsorption performance on 2,4-DCP,as well as the oxidation performance and degradation mechanism after coupling with PS in the removal of 2,4-DCP.The following are the key research findings and conclusions:（1）Preparation and characterization of sludge biochar materials.Sludge biochar（SDBC）was prepared from municipal sludge by slow pyrolysis at high temperature under nitrogen atmosphere,porous sludge biochar（PSDBC）was prepared by acid modification,and porous sludge biochar loaded with zero-valent iron（ZVI@PSDBC）was prepared by carbothermal reduction method.SEM,BET,FT-IR,XRD and XPS were used to investigate the morphological and structural characteristics of the obtained sludge biochar materials,and the results showed that PSDBC and ZVI@PSDBC had rough surface,abundant pore structure and high graphitization degree,and Fe⁰ nanoparticles were successfully doped into ZVI@PSDBC.（2）Study on the adsorption performance and mechanism of PSDBC for 2,4-DCP.The effects of various factors on the adsorption performance of PSDBC were investigated.At25℃,the saturated adsorption capacity of PSDBC for 2,4-DCP was 30.855 mg/g.The adsorption kinetics and adsorption isotherm model fitting revealed that the adsorption of2,4-DCP by PSDBC belonged to chemisorption and multi-layer adsorption process on the heterogeneous surface.Thermodynamic fitting parametersΔG^θ<0,ΔH^θ>0,ΔS^θ>0indicated that the adsorption process could be carried out spontaneously,and the process was endothermic,which could increase the disorder degree of the solid-liquid interface.（3）Study on the performance and degradation mechanism of 2,4-DCP by PSDBC/ZVI@PSDBC activated persulfate.The effects of different factors on the degradation of 2,4-DCP were investigated.Under the optimal reaction conditions,PSDBC/PS and ZVI@PSDBC/PS systems could respectively remove 98.8%and 99.8%of 2,4-DCP（50 mg/L）within 20 min,and the mineralization rates in these two systems could reach 73.7%and 91.6%respectively within 60 min.There were both radical and non-radical mechanisms in the catalytic systems.In the radical pathway,SO₄^·-and·OH were mainly involved in the oxidative degradation of 2,4-DCP;while in the non-radical pathway,besides the oxidation of ¹O₂,there was a direct electron transfer process between catalysts,PS and 2,4-DCP.（4）The environmental practicability of PSDBC and ZVI@PSDBC was explored.Thereusability of PSDBC and ZVI@PSDBC was good.After four cycles,the degradation rates of 2,4-DCP by the synergistic systems of these two materials with PS could still reach 89.4%and 91.2%,respectively.The treatment effects of PSDBC adsorption and ZVI@PSDBC/PS catalytic oxidation on actual wastewater were verified.Under the optimal process,the removal rates of COD and TOC in water samples could reach 42.9%and 48.1%respectively,which had a practical application prospect.