A Comparative Study of Arsenic Removal from Drinking Water Using Zero-Valent Iron (ZVI) and Magnetite/Reduced Graphene Oxide (MrGO) Coated Sand in Column Systems

Arsenic contamination in drinking water is a pressing global issue, with over 250 million individuals lacking access to water that meets the World Health Organization's recommended limit of 10 µg/L. Arsenic, a confirmed carcinogen, poses significant health risks, necessitating efficient and cost-effective removal strategies. Adsorption remains one of the most prevalent methods for arsenic removal, employing materials such as metal oxides, graphene-based metal oxides, nanocomposites, and carbonaceous materials and organic-metallic frameworks. One of the most researched materials for the removal of arsenic from drinking water is Zero-Valent Iron (ZVI).  However, ZVI, while widely utilized, exhibits limitations including reduced efficacy for As(III), extended reaction times, sensitivity to competing ions, narrow operational pH and DO range, and iron leaching into the water. This study explores the potential of magnetite/reduced graphene oxide (MrGO)-coated sand as an advanced alternative. MrGO's structural synergy, combining highly adsorptive magnetite nanoparticles with the enhanced stability and properties of reduced graphene oxide, addresses many of ZVI’s shortcomings. However, its application in column studies as a fixed nanoparticle remains underexplored, limited to theoretical and batch studies and pelletized or layered column studies. A novel approach to arsenic removal by integrating MrGO-coated sand and ZVI in column systems is presented in this work. The study evaluates their performance independently and in combination, focusing on removal efficiency, operational range, and cost-effectiveness. This includes the development of MrGO-coated sand for enhanced applicability in column systems and the optimization of MrGO-to-ZVI ratios to achieve maximum removal efficiency under conditions representative of real-world groundwaters. Preliminary findings suggest that MrGO-coated sand demonstrates the ability of the material to adequately remove arsenic while maintaining a broader operational conditions compared to ZVI. By investigating optimal ratios and conditions, this study aims to balance performance with economic feasibility, providing a scalable solution for arsenic-contaminated water treatment, contributing to the advancement of arsenic removal technologies and highlighting the potential of reduced-graphene-oxide-based materials in addressing critical water quality challenges.

Acknowledgement: This study is supported by TUBITAK (The Scientific and Technological Research Council of Turkey) 1001 Project with Grant Number 123Y025 and Research Fund of the Middle East Technical University, Research Universities Support Program (ADEP) with Grant Number ADEP-311-2022-11172