Immobilizing laccase on kaolinite and its application in treatment of malachite green effluent with the coexistence of Cd (П).

Malachite green effluent with the Coexistence of Cd (П) was efficiently decolorized by kaolinite-laccase (Kaolin-Lac). Laccase from Trametes versicolor was immobilized onto the kaolinite through physical adsorption contact. The optimal conditions were 180 min of immobilization time and 0.8 mg/mL of enzyme solution. Kaolin-Lac could obtain a loading efficiency of 88.22%, a loading capacity of 12.25 mg/g, and the highest activity of 839.01 U/g. Moreover, the process of immobilization increased its pH stability and operational stability. Kaolin-Lac retained above 50% of the original activity and nearly 80% decolorization for MG after 5 cycles. In the presence of 3, 5-Dimethoxy-4-hydroxybenzaldehyde (SA), Kaolin-Lac could degrade over 98% of malachite green. The coexistence of Cd (П) was beneficial to the decolorization of malachite green by Kaolin-Lac. The structural and morphological features of kaolinite, Kaolin-Lac and Kaolin-Lac after degradation were determined by scanning electron microscopy-energy spectrum analysis (SEM-EDS) and Fourier transform infrared spectroscopy (FTIR). Cadmium appeared on the Kaolin-Lac after degradation. After immobilization and degradation, the surface groups on kaolinite were changed. Kaolin-Lac showed its more potential continuous employment than free laccase in practical malachite green dyes effluent mixed with Cd (П).