Crucial role of humic substance type in Cr(VI) reduction by humic substance-Fe(III) coprecipitates but not in adsorption.

Autor: Wang H; State Key Laboratory of Environmental Criteria and Risk Assessment, and State Environmental Protection Key Laboratory of Simulation and Control of Groundwater Pollution, Chinese Research Academy of Environmental Sciences, Beijing, 100012, PR China; Beijing Key Laboratory of Water Resources & Environmental Engineering, China University of Geosciences, Beijing, 100083, PR China., Gong X; State Key Laboratory of Environmental Criteria and Risk Assessment, and State Environmental Protection Key Laboratory of Simulation and Control of Groundwater Pollution, Chinese Research Academy of Environmental Sciences, Beijing, 100012, PR China; Beijing Key Laboratory of Water Resources & Environmental Engineering, China University of Geosciences, Beijing, 100083, PR China., Zhang Y; Chinese Academy for Environmental Planning, Beijing, 100020, PR China., Liu F; Chinese Academy for Environmental Planning, Beijing, 100020, PR China., Zhang J; Beijing Key Laboratory of Water Resources & Environmental Engineering, China University of Geosciences, Beijing, 100083, PR China. Electronic address: jzh@cugb.edu.cn., Yuan Y; State Key Laboratory of Environmental Criteria and Risk Assessment, and State Environmental Protection Key Laboratory of Simulation and Control of Groundwater Pollution, Chinese Research Academy of Environmental Sciences, Beijing, 100012, PR China., Samuel B; Beijing Key Laboratory of Water Resources & Environmental Engineering, China University of Geosciences, Beijing, 100083, PR China; Department of Water and Sanitation, University of Cape Coast, Cape Coast, Ghana., Tan W; State Key Laboratory of Environmental Criteria and Risk Assessment, and State Environmental Protection Key Laboratory of Simulation and Control of Groundwater Pollution, Chinese Research Academy of Environmental Sciences, Beijing, 100012, PR China., Xi B; State Key Laboratory of Environmental Criteria and Risk Assessment, and State Environmental Protection Key Laboratory of Simulation and Control of Groundwater Pollution, Chinese Research Academy of Environmental Sciences, Beijing, 100012, PR China., Chen H; Beijing Key Laboratory of Water Resources & Environmental Engineering, China University of Geosciences, Beijing, 100083, PR China.
Jazyk: angličtina
Zdroj: Environmental pollution (Barking, Essex : 1987) [Environ Pollut] 2024 Dec 15; Vol. 363 (Pt 1), pp. 125057. Date of Electronic Publication: 2024 Sep 30.
DOI: 10.1016/j.envpol.2024.125057
Abstrakt: Wetlands exhibit a self-purification effect on Cr(VI) owing to the adsorption and reduction capabilities of their humic substance (HS)-Fe(III) coprecipitates. However, the similarities and differences in the adsorption and reduction of Cr(VI) by different types of HS-Fe(III) coprecipitates remains unknown. In this study, fulvic acid (FA)- and humic acid (HA)-Fe(III) coprecipitates were synthesized with initial C/Fe ratios ranging from 0.25 to 15, and a comparative analysis of their adsorption and reduction effects was conducted. The results showed that FA- and HA-Fe(III) coprecipitates exhibit similar abilities to adsorb Cr(VI) by forming inner-sphere complexes with ferrihydrite (Fh), as well as with FA/HA. The association between FA/HA and Fe(III) not only blocked certain FeOH adsorption sites, but also enhanced the electrostatic repulsion towards Cr(VI), resulting in a proportionate decrease in their adsorption ability. For reduction, inductive and intrinsic reduction were involved in both FA- and HA-Fe(III) coprecipitates. However, the synergism/antagonism differed with the inherent sites (e.g., phenolic hydroxyl, ArOH) and activated sites (e.g., alcoholic hydroxyl, AlOH). Based on the size differences between FA and HA, the AlOH contained in FA was more easily activated by Fe(III) than that in HA, owing to the shorter induction path required. Thus, consistent synergism was observed in FA-Fe(III) coprecipitates regardless of Fe(III) species. In contrast, synergism was only observed in HA-Fe(III) coprecipitates containing Fh, because the inductive ability of Fe(III) cations was too weak to activate AlOH through the longer path. Moreover, with irreversible consumption of AlOH, intrinsic reduction became the dominant pathway at concentrations >1 mM Cr(VI). The preferential elimination of ArOH subsequently led to a transition to antagonism. These outcomes deepen our scientifical understanding of the environmental effects of HS-Fe(III) coprecipitates and offer new perspectives for exploring their potential applications in the remediation of Cr-contaminated sites.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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Databáze: MEDLINE
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