Mesoporous Carbon Materials Prepared From Sewage Sludge By Hydrothermal Carbonization Coupled With Chemical Activatedmethod And Template Method For Adsorption Of Phenolic Compounds In Wastewater

A large amount of sewage sludge by-products are generated duringbiological treatment of wastewater,which has caused widespread environmental problems.The resource utilization of sewage sludge is an important means to solve the sludge problems.Due to the biological toxicity of phenolic compounds,the effective disposal of phenolic wastewater from industrial processes has become one of the hot topics in water environment management.In order to enrich the resource utilization ways of sewage sludge and achieve efficient recovery of phenolic compounds from phenolic wastewater,this study was carried out to prepare residual sludge-based mesoporous carbon materials by low-energy hydrothermal carbonization method coupled with chemical activation method and template method and evaluate their adsorption performance on phenolic compounds（phenol,m-Cresol,dichlorophenol,trichlorophenol,and p-nitrophenol）in phenolic wastewater using a static method.The results of mesoporous carbon material preparation showed that the adsorption performance of mesoporous carbon material produced by hydrothermal carbonization on phenolic compounds was better than the direct activation treatment of sewage sludge,and Zn Cl₂activation was better than KOH activation.The average pore size of mesoporous carbon material prepared by hydrothermal carbonization of sludge and then activated by 40%Zn Cl₂with an addition ratio of 3:1 at 600℃for 2h was 5.75 nm,along with a specific surface area of 412.40 m²/g,while that prepared from hydrothermal carbonization of sludge and regulated by Triblock copolymer F127 template with a dosing ratio of 0.25:1 was as high as 549 m²/g with an average pore size of 3.54 nm.The adsorption results show that the adsorption of the two optimized mesoporous carbon materials on the five phenols is described by Langmuir isothermal model,with the maximum theoretical adsorption capacity of 31.18 mg/g,49.96 mg/g,118.38 mg/g,106.67 mg/g,79.33 mg/g;22.30 mg/g,44.19 mg/g,100.57mg/g,99.22 mg/g,58.087 mg/g.The adsorption kinetics is fitted well by the pseudo-secondary kinetic equation,and both physical and chemical adsorption are observed,together with an exothermic process.There is competitive adsorption when the five phenols are co-existed in a phenolic wastewater and the adsorption effect of chemically activated mesoporous carbon material was 2,4-dichlorophenol>2,4,6-trichlorophenol>p-nitrophenol>m-Cresol>phenol,and the adsorption of2,4-dichlorophenol and 2,4,6-trichlorophenol by the template-modulated mesoporous carbon material reached 89%of the total adsorption.Not favorable for phenol and m-Cresol at p H>9,2,4-dichlorophenol,p-nitrophenol at p H>7,2,4,6-trichlorophenol adsorption at p H>6.The best desorption effect on phenol after adsorption of phenolic compounds,the maximum phenol desorption at 200℃is 87.5%,and Maximum phenol desorption efficiency of 92%for 0.5 mol/L concentration of KOH.