Poly(catechol) modified Fe3O4 magnetic nanocomposites with continuous high Fenton activity for organic degradation at neutral pH.

Yani Hua,Chuan Wang,Sha Wang,Juan Xiao

doi:10.1007/s11356-021-15088-7

Abstract

Fe3O4 magnetic nanoparticles (MNPs) have been widely used as a recyclable catalyst in Fenton reaction for organic degradation. However, the pristine MNPs suffer from the drawbacks of iron leaching in acidic conditions as well as the decreasing catalytic activity of organic degradation at a pH higher than 3.0. To solve the problems, Fe3O4 MNPs were modified by poly(catechol) (Fe3O4/PCC MNPs) using a facile chemical co-precipitation method. The poly(catechol) modification improved both the dispersity and the surface negative charges of Fe3O4/PCC MNPs, which are beneficial to the catalytic activity of MNPs for organic degradation. Moreover, the poly(catechol) modification enhanced the efficiency of Fe(II) regeneration during Fenton reaction due to the acceleration of Fe(III) reduction by the phenolic/quinonoid redox pair. As a result, the Fenton reaction with Fe3O4/PCC MNPs could efficiently degrade organic molecules, exampled by methylene blue (MB), in an expanded pH range between 3.0 and 10.0. In addition, Fe3O4/PCC MNPs could be reused up to 8 cycles for the MB degradation with negligible iron leaching of lower than 1.5 mg L-1. This study demonstrated Fe3O4/PCC MNPs are a promising heterogeneous Fenton catalysts for organic degradation.

Highlights

Heterogeneous Fenton technique as a promising technique for advanced oxidation processes (AOPs) has been intensively applied for theremoval of organic pollutants because of its intrinsic advantages over classical homogeneous Fenton reactions, including the wide working pH range, no iron sludge pollution, reusable catalysts, and low H2O2 consumption(Chen et al, 2017; Goncalves et al, 2020; Luo et al, 2010)
Some Fe3+ ions were chemically adsorbed on the poly(catechol) precipitates through complexation and served as the nucleation centers for the subsequent growth of Fe3O4 once ammonium hydroxide was added
The results indicated that the addition of poly(catechol) in Fe3O4/PCC magnetic nanoparticles (MNPs) enhanced the transformation of H2O2 into OH radicals

Summary

Introduction

Heterogeneous Fenton technique as a promising technique for advanced oxidation processes (AOPs) has been intensively applied for theremoval of organic pollutants because of its intrinsic advantages over classical homogeneous Fenton reactions, including the wide working pH range, no iron sludge pollution, reusable catalysts, and low H2O2 consumption(Chen et al, 2017; Goncalves et al, 2020; Luo et al, 2010). Many solid catalysts have been demonstrated to be effective in heterogeneous Fenton reactions(Li et al, 2018; Li et al, 2017). Fe3O4 magnetic nanoparticles (Fe3O4 MNPs) have received great attention in Fenton reactions(Mondal et al, 2020). Gao et al demonstrated that Fe3O4magnetitenanoparticles possessed an intrinsic enzyme mimetic activity similar to that of peroxidases in nature, which were widelyused to oxidize organic pollutant in the treatment of wastewater. Fe3O4 MNPs possessed highly effectivecatalyticactivity, which possessed ahigher binding affinity for the substrate TMB than HRP and exhibiteda40-fold higher level of activity at the same molar catalyst concentration than that of HRP (Gao et al, 2007).the Fe(II) in Fe3O4 MNPs plays an important role as the electron donor to initiate the Fenton reactions. Fe3O4 MNPs can be used as Fenton catalysts for activating H2O2(Cai et al, 2021; Xiang et al, 2021)

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Conclusion