In this study, polyethyleneimine was combined with magnetic Fe3O4 nanoparticles through the bridging of carboxyl-functionalized ionic liquid, and laccase was loaded onto the carrier by Cu2+ chelation to achieve laccase immobilization (MCIL-PEI-Cu-lac). The carrier was characterized by Fourier transform infrared spectroscopy, scanning electron microscope, thermogravimetric analysis, X-ray diffraction analysis, magnetic hysteresis loop and so on. MCIL-PEI-Cu-lac has good immobilization ability; its loading and activity retention could reach 52.19 mg/g and 91.65%, respectively. Compared with free laccase, its thermal stability and storage stability have been significantly improved, as well. After 6 h of storage at 60 °C, 51.45% of the laccase activity could still be retained, and 81.13% of the laccase activity remained after 1 month of storage at 3 °C. In the pollutants removal test, the removal rate of 2,4-dichlorophenol (10 mg/L) by MCIL-PEI-Cu-lac could reach 100% within 10 h, and the removal efficiency could still be maintained 60.21% after repeated use for 8 times. In addition, MCIL-PEI-Cu-lac also has a good removal effect on other phenolic pollutants (such as bisphenol A, phenol, 4-chlorophenol, etc.). Research results indicated that an efficient strategy for laccase immobilization to biodegrade phenolic pollutants was developed.
Keywords: ionic liquids; laccase; magnetic polyethyleneimine nanoparticles; phenolic pollutants.