Halide removal from water using silver doped magnetic-microparticles

Abstract

This study proposes the use of new materials based on core-shell structure magnetic microparticles with Ag⁰ (Ag(0)-MPs) on their surface to remove bromides and chlorides from waters intended for human consumption. Hydrogen peroxide was used as oxidizing agent, Ag(0)-MPs is thereby oxidized to Ag (I)-MPs, which, when in contact with Cl^- and Br^- ions, form the corresponding silver halide (AgCl and AgBr) on the surface of Ag-MPs. The concentration of Cl^- and Br^- ions was followed by using ion selective electrodes (ISEs). Silver microparticles were characterized by high-resolution scanning electron microscopy and X-ray photoelectron spectroscopy, while the presence of AgCl and AgBr on Ag-MPs was determined by microanalysis. We analyzed the influence of operational variables, including: hydrogen peroxide concentration in Ag-MP system, medium pH, influence of Cl^- ions on Br^- ion removal, and influence of tannic acid as surrogate of organic matter in the medium. Regarding the influence of pH, Br^-and Cl^- removal was constant within the pH range studied (3.5-7), being more effective for Br^- than for Cl^- ions. Accordingly, this research states that the system Ag-MPs/H₂O₂ can remove up to 67.01% of Br^- ions and 56.92% of Cl^- ions from water (pH = 7, [Ag-MPs]₀ = 100 mg L^-1, [H₂O₂]₀ = 0.2 mM); it is reusable, regenerated by radiation and can be easily removed by applying a magnetically assisted chemical separation process.

Keywords: Advanced oxidation process; Halide removal; Silver microparticles.