Oxidation of V(IV) by Birnessite: Kinetics and Surface Complexation

Abstract

Vanadium is a redox-active metal that has been added to the EPA's Contaminant Candidate List with a notification level of 50 μg L −1 due to mounting evidence that V V exposure can lead to adverse health outcomes. Groundwater V concentration exceeds the notification level in many locations, yet geochemical controls on its mobility are poorly understood. Here, we examined the redox interaction between V IV and birnessite (MnO 2 ), a wellcharacterized oxidant and a scavenger of many trace metals. In our findings, birnessite quickly oxidized sparingly soluble V IV species such as haggite [V 2 O 3 (OH) 2 ] into highly mobile and toxic vanadate (H n VO 4(3−n)− ) in continuously stirred batch reactors under neutral pH conditions. Synchrotron X-ray absorption spectroscopic (XAS) analysis of in situ and ex situ experiments showed that oxidation of V IV occurs in two stages, which are both rapid relative to the measured dissolution rate of the V IV solid. Concomitantly, the reduction of birnessite during V IV oxidation generated soluble Mn II , which led to the formation of the Mn III oxyhydroxide feitknechtite (β-MnOOH) upon back-reaction with birnessite. XAS analysis confirmed a bidentate-mononuclear edge-sharing complex formed between V V and birnessite, although retention of V V was minimal relative to the aqueous quantities generated. In summary, we demonstrate that Mn oxides are effective oxidants of V IV in the environment with the potential to increase dissolved V concentrations in aquifers subject to redox oscillations.

Towards Understanding Factors Affecting Arsenic, Chromium, and Vanadium Mobility in the Subsurface

“…Clays can also act as reaction surfaces for the oxidation of As(III) to As(V), again, strongly influenced by pH, ionic strength, and composition of clay surfaces [ 49 ]. Likewise, Cr(III) and V(IV) can also be oxidized to Cr(VI) and V(V) by naturally occurring mineral oxidants, most commonly Mn oxides [ 74 , 75 ]. For Cr(III), the reaction with Mn oxides is dependent on the pH of the environment; where the pH is less than 6, the reaction occurs with dissolved Cr(III) adsorbing onto the surface of solid Mn oxides, whereas for a pH greater than 8 the reaction occurs by the redox cycling of Mn the surfaces of solid Cr(III) surfaces [ 74 ].…”

Facet-Dependent Atomic Distances Shape Vanadate Adsorption Complexes on Hematite Nanocrystals

“…1,2 Vanadium has been listed in the Drinking Water Contaminant Candidate List (CCL) by the U.S. Environmental Protection Agency (EPA) since 1998, with a minimum reporting level of 0.2 μg/L. 3,4 Vanadium mainly exists as vanadate (V(V)) in the environment (Figure S1). 5 Exposure to water containing V(V) may lead to dysfunction of phosphatase in the human body and further pulmonary diseases.…”

“…Vanadium contamination due to industrial and mining activities has received public concerns owing to increasing awareness of its toxicity. , Vanadium has been listed in the Drinking Water Contaminant Candidate List (CCL) by the U.S. Environmental Protection Agency (EPA) since 1998, with a minimum reporting level of 0.2 μg/L. , Vanadium mainly exists as vanadate (V­(V)) in the environment (Figure S1). Exposure to water containing V­(V) may lead to dysfunction of phosphatase in the human body and further pulmonary diseases. , The methods of chemical precipitation, solvent extraction, and adsorption have been widely performed to remove V­(V) from wastewater. , Among these methods, adsorption is optimal because of its high efficiency, cost-effectiveness, and ease of operation. − …”

Mobility of arsenic and vanadium in waterlogged calcareous soils due to addition of zeolite and manganese oxide amendments

“…Redox-sensitive V prevails in the oxidation states of V(III), V(IV), and V(V) in the soil environment, where the latter has the highest solubility and toxicity (Larsson et al, 2017). Vanadium toxicity in aquatic and terrestrial environments is dependent on the concentration, oxidation state, and species of V (Abernathy et al, 2021). The Red River floodplain area is flat and contains clay soils with poor permeability, causing frequent flooding, and floodwater carries nutrients and metals to waterways.…”

“…Soil amendments typically act as adsorbent materials to bind toxic metals to the surface, form precipitates, or change their speciation (Indraratne et al., 2021; Zou et al., 2019). Manganese oxides alter the speciation of redox‐sensitive elements and are well‐known scavengers for PTEs in contaminated soils (Abernathy et al., 2021; Komarek et al., 2013). Zeolites are microporous aluminosilicates that can be modified to increase their metal adsorption capacity by improving the surface area, porosity, and ion exchange capacity (Zheng et al., 2021).…”