Preparation of Functionalized Mesoporous Silica as a Novel Carrier and Immobilization of Laccase.

Amino-modified mesoporous silica (SBA-15-NH2) was prepared by hydrothermal method, which is a kind of excellent carrier for enzyme immobilization. The structure of SBA-15 was characterized by SEM and FTIR, which proved that amino group was successfully attached to the surface of SBA-15. The carrier had good mesoporous structure proved by nitrogen adsorption and desorption test. Using SBA-15-NH2 as the carrier, the optimal conditions of laccase immobilization by two different cross-linking methods were explored. At the same time, the properties of the immobilized enzyme and free enzyme were compared. The results showed that the activity of immobilized laccase by two-step method (2977.5 U/g) was much higher than that by one-step method (239.5 U/g). The optimal conditions were as follows: free laccase (35°C, pH=4.5), two-step immobilized laccase (40°C, pH=4.0), one-step immobilized laccase (35°C, pH=4.0). The two-step method was more adaptable to temperature. The pH adaptation range of the immobilized enzyme is wider, and the thermal stability is greatly enhanced. After five cycles of repeated reaction, the residual enzyme activity of two-step and one-step methods was 56% and 43% of the original. The treatment of simulated wastewater containing 2,4-dichlorophenol (2,4-DCP) by immobilized laccase was also studied. Under optimum conditions (40°C, pH=5.0, 20 mg/L), the removal of 2,4-DCP reached 89.06%. The immobilized laccase is really effective for treatment of 2,4-DCP-containing wastewater.