Laccase Immobilization On Chitosan/Nano Biochar Modified Membrane Paper For 17β-estradiol Degradation

Endocrine disrupting chemicals(EDCs)are a kind of pollutant widely existing in environment,food and consumption product,such as bisphenol A(BPA),17β-estradiol(E2)and acetylene estradiol(EE2),etc.These chemicals will interfere with the development of the organism’s endocrine system and organs that respond to endocrine signals,and interfere with the synthesis and metabolism of hormones,leading to the imbalance of internal endocrine and pathological changes of the reproductive system.17β-estradiol(E2)is a kind of specific pollutant which is extremely toxic that has detected in surface water,ground water and soil.E2 would cause a profound effect on the human body and the environment even at nanograms per liter.As a result,effective degradation of E2 from water is extremely crucial.Enzyme catalyst technology is more selective,environmentally friendly and reacted rapidly compared with physical and chemical methods.Laccase is an oxidizing enzyme with widely substrates,and only needs oxygen to complete catalytic reaction.Enzyme immobilization could utilize to cover the shortage of laccase corresponding to inactive easily and hard to reuse.Enzyme immobilization would improve stability and reusability of laccase,making laccase catalyzed process more economical.Moreover,cellulose filter paper is a kind of fibrous material with macropore which is environmental and with low price,and has the properties of highly hydrophilic.Biochar has a large amount of pores and large specific surface area which is a common support for enzyme immobilization.After hydrothermal treatment,the number of mesoporous and specific surface area would increase.In this study,hydrothermal modified cellulose filter paper would be utilized as support to make laccase immobilized chitosan and nano biochar modified membrane paper(CS-HBC-MP/Lac)for E2 degradation in water.Removal Efficiency and mechanism was explored.In addition,the catalytic activity,thermal and p H stability,storage stability and reusability were examined.This study provided theoretical basis and technical support for the removal of estradiol(E2)from water by CS-HBC-MP/Lac.Conclusions from the above research:(1)Large amount of laccase has been immobilized onto chitosan and nano biochar modified membrane paper through adsorption,covalent bonding,precipitation and cross-linking.Obtained CS-HBC-MP/Lac had achieved the activity of 7.96 m U/cm~2.The successful immobilization of laccase was confirmed by SEM.Compared with free laccase,immobilized laccase has a wider p H and temperature range,and its stability has been improved.(2)Laccase immobilized chitosan and nano biochar modified membrane paper(CS-HBC-MP/Lac)could be stored at-20℃in dried condition on account of the microenvironment provided by chitosan and hydrothermal biochar retained more than95%of initial activity after 60 days.(3)Laccase immobilized chitosan and nano biochar modified membrane paper(CS-HBC-MP/Lac)showed highest catalyst activity at p H 5.0,30℃.CA-HBC-MP/Lac could remove more than 93%of E2(1 mg/L,3 m L)in 10 minutes.After 10times using,E2 degradation efficiency still achieved over 90%.