Removal Mechanism Of Bisphenol A And Azo Dye In Water By Enzyme-immobilized Biochar Composites

Compared with the traditional physical and chemical environmental remediation methods,enzyme biocatalysis method has the advantages of better specificity and shorter operation cycle.Laccase has attracted much attention as a biocatalyst with a wide range of substrate oxidation capabilities.However,free laccase is hard to be recovered and easily inactivated,so it is expensive to use in practice.Enzyme immobilization technology can help laccase retain catalytic activity,facilitate preservation and transportation,achieve reuse at the same time,and can continue to participate in catalytic reaction for a long time.Biochar has a wide range of sources,is environmentally friendly and low-cost.It is often used in the research of soil improver and adsorbent in recent years.It has the potential to be an enzyme immobilized carrier.In this paper,biochar was selected as the carrier material for laccase immobilization.Laccase immobilized magnetic biochar（L-MBC）and laccase immobilized biochar copper alginate beads（L-BCA）were used to remove bisphenol A and methyl orange in water respectively.This study provides theoretical basis and technical means for the study of enzyme-immobilized biochar composites and the remediation of water polluted by bisphenol A and azo dyes.Conclusions from the above studies:（1）A large number of laccases were successfully and stably immobilized on magnetically separated biochar by adsorption,precipitation and crosslinking,and the magnetic biochar was prepared by co-precipitation.The enzyme loading of the L-MBC was 1.424 mg/mg more than 30 times higher than that of the adsorption method.T The successful immobilization of laccase was also confirmed with FTIR,SEM and EDS.By comparing the free laccase and L-MBC,it was found that the immobilized laccase by this method had a wider working range of pH and temperature,and its stability was improved.（2）The L-MBC can achieve the removal rate of bisphenol A to 100%within 75min,at the same time,the high reusability that the removal rate of bisphenol A can still maintain more than 85%after 7 times of use.The L-MBC can remove the bisphenol A by adsorption and biodegradation of laccase,and finally a detoxified product is obtained.After inspection,the L-MBC can still remove bisphenol A well in environmental water,so it has the potential to be used for actual environmental remediation.（3）Laccase was encapsulated in copper alginate with biochar in the form of crosslinked aggregates,and the L-BCA beads with a diameter of 2-3 mm were successfully prepared.Due to the microenvironmental protection provided by biochar and copper alginate,the stability of the composite ball was greatly improved compared with other methods,and 81.87%of the activity was retained after storage at room temperature for 30 days.（4）The L-BCA exhibited the highest enzyme catalytic activity on the substrate ABTS at a pH of 3.5-4.0 and a temperature of 40℃,and had a wider range of adaptation compared to free laccase.At the same time,the composite sphere can effectively remove methyl orange as a typical azo dye of 10 mg·L^-1,and the decolorization rate can reach 80.09%.After evaluation,it also had good reusability.