Removal of β-estradiol in wastewater using laccase immobilized by biochar and carbon nano tube
Laccase is a class of Cu-containing polyphenol oxidase with high catalytic oxidation ability.The immobilized laccase technique has attracted an increasing attention in organic wastewater treatment.In this study,wood-and bamboo-derived biochars(WB and BB)or carbon nano tube(CNT)were used to immobilize laccase by the adsorption and embedding methods for the removal of β-estradiol(E2)in aqueous environment.At 25 ℃ and pH=5,80％activity of the immobilized laccase on WB,BB,and CNT was preserved after 120 h storage.After 5 cycles,the residual activity of the immobilized laccase was 27％～58％.Combined with scanning electron microscopy and Fourier transform infrared spectroscopy,it was confirmed that laccase was successfully loaded on carbon-based materials.Within only 8 h,42.92％,47.66％,and 43.92％of 50 mg·L-1 E2 were removed by WB-,BB-,and CNT-immobilized laccases using the adsorption method,while 84.08％,87.2％,and 87.86％of 50 mg·L-1 E2 were removed by WB-,BB-,and CNT-immobilized laccases using the embedding method.The results showed that the immobilized laccase using the embedding method had a better removal efficiency for E2 due to its stronger stability onto biochars and CNT.In addition,K+and Mn2+ions could interfere with electron transfer of laccases,then affect the activity of laccases,diminish E2 removal.The aim of this work can provide a guidance for designing immobilized laccase for organic wastewater treatment.
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