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.

Copper Ion-Activated UiO-66-NH2 Immobilized Laccase for Boosting Enzyme Stability and Organic Pollutant Removal

“…The identified diffraction peaks at 2θ = 30.1°, 35.4°, 43.1°, 53.4°, 57.2°, and 62.5°correspond to (220), (311), (400), (422), (511), and (440) crystal planes of Fe 3 O 4 as indexed in the Powder Diffraction File #77-1545 for Fe 3 O 4 nanoparticles with magnetic properties report in literature. 11 The XRD pattern of UiO-66-NH 2 exhibited characteristic peaks at 2θ = 7.3°, 8.5°, and 25.7°, consistent with previous reports. 26,27 The XRD pattern of MCIL@Cu-UiO-66-NH 2 -GA was similar to that of UiO-66-NH 2 , indicating that the incorporation of MCIL, Cu ion doping, and GA did not alter the crystal structure of the matrix UiO-66-NH 2 .…”

“…The Fe 3 O 4 was synthesized following a previously established protocol . To prepare ILs-modified magnetic Fe 3 O 4 nanoparticles, we made some modifications to the previous report. , Specifically, 3 g of Fe 3 O 4 nanoparticles was dispersed in toluene and 15 mmol of CPTMO under nitrogen protection at 95 °C for 7 h. Next, the obtained solid was washed with ethanol multiple times and separated using a magnet. After that, the solid was dispersed with imidazole (15 mmol) in chloroform and stirred at 35 °C for 24 h under a nitrogen atmosphere.…”

“…Coating composite carriers (MNPs) with ionic liquids (ILs) not only prevents aggregation but also improves microenvironmental conditions. 10,11 Moreover, these functional groups can be utilized for further surface functionality.…”

“…Surface modification of magnetic nanoparticles (MNPs) is a convenient strategy to enhance their stability and functionalization. Coating composite carriers (MNPs) with ionic liquids (ILs) not only prevents aggregation but also improves microenvironmental conditions. , Moreover, these functional groups can be utilized for further surface functionality. Although the magnetic structure overcomes the size effect of the nanocarrier, enzyme activity is reduced due to binding with the MOF. , The development of a suitable MOF design that enhances both enzyme activity and stability remains an urgent challenge.…”

“…11,25 Specifically, 3 g of Fe 3 O 4 nanoparticles was dispersed in toluene and 15 mmol of CPTMO under nitrogen protection at 95 °C for 7 h. Next, the obtained solid Scheme 1. Schematic Illustration of the Synthesis of MCIL@Cu-UiO-66-NH 2 -GA, Laccase Immobilization,…”