Photoactive Polyethylenimine-Coated Graphene Oxide Composites for Enhanced Cr(VI) Reduction and Recovery

Abstract

The application of positively charged polymers is a common treatment strategy for the sorption and separation of dissolved hexavalent chromium Cr­(VI). In particular, polyethylenimine (PEI) has been demonstrated as an effective polymer for Cr treatment due to abundant amine groups and cost-effectiveness. However, PEI as a photoactive polymer has not been previously explored for Cr treatment. Toward this, we demonstrate the significant photoactive potential of PEI for Cr sorption and reduction [to Cr (III)], delineating amine structure–function relationships. Overall, Cr­(VI) photoreduction is enhanced dramatically as a function of amine group density. Additionally, among the types of amine groups evaluated, tertiary amines are observed to be the most reactive followed by secondary and primary amines. When PEI is incorporated onto graphene oxide (GO) as a stabilizing scaffold, mass loading of PEI is a key variable for Cr­(VI) treatment performance, which is observed to be a function of PEI molecular weight and oxidation extent of GO. Finally, when combined with magnetic nanomaterials, low energy, high efficiency separation, and reuse are demonstrated. For these, sorption-based separation processes maintained excellent performance over five cycles. Taken together, this work demonstrates that PEI can serve as highly effective, multifunctional material coating(s) not only for chromium treatment but potentially for other oxidized aqueous species as well.

Method for Decontamination of Toxic Aluminochrome Catalyst Sludge by Reduction of Hexavalent Chromium

“…Studies by Zixi Fan et al and Jianhua Qu et al investigated several types of activated and deactivated biochar to effectively remove Cr (VI) from polluted industrial wastewater [27,28]. For the adsorption of chromium from solutions in the works of Paulina Janik et al and Changwoo Kim et al, graphene oxide was modified with various aminosilanes containing one, two, or three nitrogen atoms in the molecule [29,30]. In a study by Xufan Zhang et al, magnetic titanomagnegemite (Fe 2 TiO 5 ) was sulfated with H 2 S gas to increase the removal efficiency of Cr (VI) [31].…”

“…The use of nanomaterials, which are considered to be materials smaller than 100 nm, is gaining popularity. The use of some inorganic nanoparticles as reducing agents or catalysts can significantly increase the reduction rate of Cr (VI) [30]. In the works of Miroslav Brumovský et al and Qianqian Shao et al, the exploitation of sulfidized iron nanoparticles to increase the reactivity and selectivity of nZVI, with respect to the target pollutant chromium [34,35], was considered.…”