Immobilization Of Laccase On Modified Biochar And Its Adsorption And Degradation Performance For 2,4-DCP

The chlorophenols,with high toxicity,are a class of persistent pollutants for environment.As a chemical intermediate or final product,it is widely used in agriculture,manufacturing,chemical industries and so on.The environmental treatment chlorophenols polluting has always been the focus for scientists.The technology that modified biochar immobilisate laccase for adsorpting and degradating 2,4-DCP was constructed in this paper.Firstly,the preparation and characterization of biochar were studied.The adsorption properties and mechanism also were studied;The feasibility and optimal conditions of laccase immobilisated on CSC(modified biochar)were determined,and CSL was defined as the material which obtained by laccase immobilisated on CSC under the optimal conditions;The degradation properties of 2,4-DCP by laccase was studied;The adsorption and degradation properties of 2,4-DCP by CSL was studied,and the removal properties of CSL to 2,4-DCP was compared with CSC's and laccase's separately under the same experimental conditions;Finally,the final products and degradation pathways of 2,4-DCP were studied.The main conclusions are as follows:(1)The surface of CSC contains a large number of functional groups such as alcoholic hydroxyl,ether and so on,and there are quaternary ammonium salt cation of CTAB(cetyl trimethyl ammonium bromide)successfully grafted onto the surface of CSC;The crystal structure of CSC is more complete than that of CS(unmodified biochar),so CSC may be a higher crystallinity molecule;The BET specific surface area of CSC is 221.352 m~2/g,the micropore pore volume is 0.16 m~3/g,the micropore pore volume accounts for 34.86%of the total pore volume,and the pore diameter is mainly distributed in 1?10 nm.(2)The optimal adsorption conditions for 2,4-DCP by CSC were as follow:the initial concentration was 200 mg/L,the dosage of CSC was 50 mg,the p H was 5.5,the time was50 min,and the temperature was room temperature.The removal rate was 42.5%,and the adsorption capacity was 85.13 mg/g under the optimal conditions.The process was mainly controlled by the chemical adsorption mechanism.The adsorption of 2,4-DCP on CSC was monolayer adsorption that occurs on the uniform surface of CSC at a high concentration solution.(3)The optimal immobilisation conditions of CSC for free laccase were as follow:the enzyme dosage was 1.75 mg/mL,the pH was 3,the time was 4 h,and the temperature was 313 K.The relative enzyme activity of CSL was 61.7%,and the immobilization capacity was 50.4 mg/g.Immobilized laccase had better thermal stability and temperature tolerance than free laccase.CSL could be reused many times.After 6 consecutive cycles of catalytic reaction,the relative enzyme activity of laccase was 27.8%of that of original enzyme activity.(4)the optimum conditions for degradation of 2,4-DCP by free laccase are as follows:pH 6,enzyme dosage 0.2 U/m L,time 7 h,temperature 308 K.The degradation process was consistent with the first-order reaction kinetics.(5)CSL had both adsorption and biodegradation for remove 2,4-DCP,and the contribution of biodegradation was greater than adsorption.The macroscopic process of the removal of 2,4-DCP by CSL showed adsorption first and then degradation.The products of 2,4-DCP adsorbed and degradated by CSL included p-benzoquinone,2-hydroxyhexane and 4-isopropylphenol.