Magnetite interaction with arsenic during sorptive removal from groundwater: a mechanistic study

Abstract

A magnetic mixed iron oxide, magnetite (Fe₃O₄), was synthesized in the laboratory and characterized before its use as sorbent for arsenic removal. The characterization techniques used were X-ray diffraction (XRD), specific surface area, zeta potential and particle size measurements. The sorbent was applied for arsenic removal, without any pre or post treatment, from groundwater. The efficiency of sorption can only be improved by understanding the sorbent–sorbate interaction. For onsite monitoring of the sorbent-sorbate interaction, an electrochemical investigation using cyclic voltammetry (CV) measurement was developed. The study confirmed that the sorption of As(III) on Fe₃O₄ is dynamic (reversible) whereas that of As(V) is static (irreversible) in nature. Detailed investigation after the sorption was carried out utilizing X-ray photoelectron spectroscopy (XPS) measurement. The complexation of As(III)-Fe₃O₄ and As(V)-Fe₃O₄ without any redox transformation was evident from the XPS data. By careful examination of the results, a mechanism of arsenic removal by Fe₃O₄ was proposed.

Graphical Abstract

Keywords:

• Mechanism of sorption
• arsenate
• arsenite
• magnetite
• XPS
• electrochemical study

Acknowledgments

Authors thank Dr. C. N. Patra, Head, Analytical Chemistry Division, BARC for his support. Authors thank the operation crew of Dhruva reactor for their support during sample irradiation for radiotracer preparation.

Additional information

Funding

The author(s) reported there is no funding associated with the work featured in this article.