Immobilization of laccase on PAMAM dendrimers modified core-shell Fe₃O₄-SiO₂ magnetic composite particles for degradation of 2,4-dichlorophenol

Polyaminoamide (PAMAM) dendrimers with different generations from 1 G to 5 G were grafted on magnetic core-shell Fe₃O₄-SiO₂ composite particles, respectively. Using Fe₃O₄ as a magnetic center and SiO₂ as the connecting layer, the PAMAM dendrimers with amino functional groups were modified on SiO₂ successfully, while laccase was immobilized to the surface of Fe₃O₄-SiO₂-PAMAM_x by covalent cross-linking using amide bond. Under the optimal conditions, the loading capacity of laccase reached 65.5 mg/g, and about 62.8 % of its initial activity of free laccase was reserved. Immobilized laccase degradated 2,4-dichlorophenol (2,4-DCP) with a degradation ratio of 91.5 % after 24 h. The degradation ratio of 82.9 % was maintained after 5 cycles of the operation, and when enhanced to the 10 cycles degradation, the degradation rate was still remained close to 80 %. Compared with free laccase, the comprehensive stability of immobilized laccase was improved significantly, and it displayed the excellent catalytic degradation ability for 2,4-DCP.