Remediation and improvement of 2,4-dichlorophenol contaminated soil by biochar-immobilized laccase

In this paper, laccase was immobilized with the adsorption-crosslinking method in which biochar was used as the carrier and glutaraldehyde was used as the crosslinking agent. Firstly, the optimal immobilization conditions and optimal operating conditions were investigated, and then the stability of both free laccase and immobilized laccase was compared. Finally, the 2,4-dichlorophenol contaminated soil was remedied with both free laccase and immobilized laccase, and the improvement on the remediation of the contaminated soil by immobilized laccase was analysed through the ecological evaluation. The results showed that in the optimal immobilization condition, the biochar with a particle size of 30 mesh should be selected, and glutaraldehyde with a volume fraction of 4% and 20 mL of laccase solution should be added to complete the 6-hour adsorption operation and 4-hour crosslinking operation. The stability of immobilized laccase was better than that of free laccase, and the thermal deactivation kinetic equation for the free laccase was lnA = −0.7657t + 0.4344 and the thermal deactivation kinetic equation for the immobilized laccase was lnA = −0.1048t + 0.0608, respectively. The degradation ability of immobilized laccase for 2–4 dichlorophenol was better than that of free laccase. The degradation rate of 2,4-dichlorophenol was 44.4% in the free laccase group and 64.6% in the immobilized laccase group. The ecological evaluation showed that the biochar-immobilized laccase had a positive effect on the soil ecological environment in the remediation process of the soil and can improve the remediation of the contaminated soil to some extent.