Preparation Of Laccase-based Materials And Its Application Study On Malachite Green Removal In Water

Malachite green(MG)is a high water-soluble triarylmethane compound.Besides occurring as a disinfectant,antibacterial and fungicide agent in fish farming,it is also used extensively for dyeing paper,textiles.MG is carcinogenic,mutagenic and teratogenic to human beings because it could bind DNA to form complexes through intercalation and electrostatic interactions.In order to remove MG from aqueous solution quickly and efficiently and reduce environmental risks,two different catalytic materials with laccase activity were designed and synthesized based on the good degradation efficiency of laccase on MG,and studied their effectiveness in removing MG.Magnetic laccase nanoflowers(MNFs-Lac)were successfully prepared through Fe₃O₄ magnetic nanoparticles encapsulated into the interior of laccase nanoflowers using laccase as the organic component.MNFs-Lac were flower-like crystals with diameters of?10?m,which had excellent enzyme activity and magnetic recycling ability.Under optimized conditions(0.3 m M Hobt,pH 4.5,35^oC,25 mg·L^-1,1.5g·L^-1),MNFs-Lac can remove 99%MG within 15 min,and the results of reusability tests by magnetic separation showed that after 18 cycles of use,the removal efficiency of MG was still as high as 90%.The natural enzymes are expensive and the enzyme activity is greatly affected by the environment.Therefore,our study also designed and synthesized Copper-Tannic acid(Cu-TA)nanozyme with laccase-like activity.Compared with natural laccase,this nanozyme not only had better storage,pH,temperature,salt ion adaptability and stability,but also promoted its activity under condition of high temperature and high salt ion concentration.In addition,Cu-TA nanozyme could adsorb and degrade MG simultaneously.This performance further improved the work efficiency of enzyme while saving the cost of metarials.The influence factors on MG removal were investigated.At room temperature(25±2^oC),pH 6,25 mg·L^-1 MG,0.3 m M Hobt,only 45 mg·L^-1 Cu-TA nanozyme could remove 98%MG within 30 min.With the increase of Na Cl salt ion concentration(0-0.3 M),the removal efficiency of 25 mg·L^-1MG increased from 87%to 98%by 30 mg·L^-1 Cu-TA nanozyme,which laid the foundation for the application of Cu-TA nanozyme in wastewater.These results show that both MNFs-Lac and Cu-TA nanozymes have the characteristics of fast and high efficiency of MG removal.The excellent recycling performance of MNFs-Lac and the environmental tolerance of Cu-TA nanozyme have potential application value on the treatment of actual wastewater.