Vanadium (V) is wide spread and essential element in the environment. However, the high concentration of V, due to human activity such as fossil fuels and mining activities, can become toxic to terrestrial plants and marine systems. Vanadium commonly exists as tetrahedral oxyanion monovanadate (V(V)O43-) in the environment. Polyvanadate has tetrahedral structure as well except decavanadate (e.g. V10O286-), which is the only octahedral oxyanion among V species. Iron oxides such as hematite (Fe2O3) is ubiquitous in subsurface sediments and soils and can control the mobility of the contaminant metals due to their high surface area and reactivity. Previous studies focus on vanadium adsorption onto ferrihydrite and hematite through solution analysis and Infrared technique. The aim of this project is to characterise the adsorption mechanisms and bonding environment of V(V)O43- onto hematite under varying environmental systems including pH (3-14), adsorbent concentrations and ionic strength, applying multi-technique approach such as geochemical modelling (PHREEQC), Attenuated Total Reflection-Fourier Transform Infrared Spectroscopy (ATR-FTIR), X-ray Absorption Spectroscopy (XAS). PHREEQC and ATR-FTIR analysis on V adsorption to hematite indicated monovanadate and polyvanadate (except decavanadate) were dominant in alkaline condition, while decavanadate played an important role under acidic and neutral systems and suggested an octehedral adsorption complex. Future work using Extended X-ray Absorption Fine Structure (EXAFS) analysis details the V adsorption mechanisms onto hematite in a molecular scale. This is associated with aqueous chemical analysis, PHREEQC, ATR-FTIR to provide a comprehensive dataset for determining the mono- or poly- vanadate species and their environmental mobility in a variety of geochemical scenarios.

Multi-technique approach on the adsorption of mono- and poly-vanadate (V(V)O43-) onto hematite

ACS Spring Meeting 2021

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