Magnetic Polyethyleneimine Nanoparticles Fabricated via Ionic Liquid as Bridging Agents for Laccase Immobilization and Its Application in Phenolic Pollutants Removal

Abstract

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.