α-FeOOH quantum dots impregnated graphene oxide hybrids enhanced arsenic adsorption: The mediation role of environmental organic ligands

Organic ligands have great potential to modulate the structure of iron oxides mineral in the natural environment and affect those minerals' adsorption performances for arsenic species. This study was designed to examine the adsorption potential of goethite quantum dots impregnated graphene oxide hybrids (alpha-FeOOH QDs@GO) obtained through the consecutive modulation of beta-FeOOH with organic ligands acetate (Ac) and graphene oxide (GO) comparing with that of akaganeite impregnated GO (beta-FeOOH@GO) and akaganeite (beta-FeOOH). The organic modulation greatly changes the structural properties of those three iron oxides hybrids with various crystalline, morphology, particle size, and surface area, thus leading to the obviously different arsenate (As(V)) and arsenite (As(III)) adsorption performances. The maximum As(III) adsorption capacity on alpha-FeOOH QDs@GO is 147.38 mg g(-1), which is 2.52 and 4.60 times larger than that of beta-FeOOH@GO and beta-FeOOH, respectively. The maximum As(V) adsorption capacity on beta-FeOOH@GO is 69.03 mg g(-1), which is 1.62 and 4.15 times larger than that of alpha-FeOOH QDs@GO and beta-FeOOH, respectively. The arsenic adsorption mechanism on alpha-FeOOH QDs@GO reveals that hydroxyl and Ac ligand exchange were the main pathways for arsenic adsorption. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

This study investigates the adsorption potential of iron oxide minerals modulated by organic ligands and compares the adsorption performances for arsenic species. The structural properties of the iron oxide hybrids significantly changed with organic modulation, leading to different arsenate and arsenite adsorption performances. The adsorption mechanism on alpha-FeOOH QDs@GO suggests that hydroxyl and acetate ligand exchange are the main pathways for arsenic adsorption.