Implementation of the adsorbent iron-oxide-coated natural rock (IOCNR) on synthetic As(III) and on real arsenic-bearing sample with filter

This study examined the As(III) adsorption efficiency on an iron-oxide based adsorbent, iron-oxide-coated natural rock (IONR), and proposes an in situ two-step mechanism, oxidation of As(III) to As(V) and its subsequent adsorption on IOCNR. In the batch study, within 6 h of contact time and at a dose of 13 g L−1, ∼98.5% As(III) (declined to ∼0.01 mg L−1) removal was achieved from the water medium, when the initial concentration was 0.6 mg L−1 at room temperature. The As(III) adsorptive capacity of IOCNR was calculated using the Langmuir isotherm 1.647 mg g−1. The effects of various parameters for As(III) adsorption, including contact time, dose, pH, initial As(III) concentrations, the presence of common cations and anions, along with some organic contaminants, were evaluated. Spontaneity and favorable adsorption of As(III) on IOCNR were evidenced from the negative Gibbs free energy changes and dimensionless equilibrium parameter. As(III) removal efficiency of the exhausted and NaOH-regenerated IOCNR decreased in the second-cycle operation. As(III) removal efficiency of IOCNR was comparable to that of the commercially available patented adsorbent LEWATIT FO36. The adsorptive behavior of IOCNR from real arsenic-bearing sample was also evaluated. Finally, small-scale household filter “SHITAL-2013” was designed and the effluent water quality was analyzed.