Arsenic removal from water using a one-pot synthesized low-cost mesoporous Fe–Mn-modified biosorbent

Abstract

This paper investigates the removal of arsenic from water using an environmentally friendly modified biosorbent, chitosan coated with Fe–Mn binary oxide (Chit-FeMn), simply prepared with an one-pot low-cost procedure by simultaneous oxidation and coprecipitation. The sorbent was characterized by SEM, EDS, XRD, FTIR, BET specific surface area, and point of zero charge (pH_pzc) measurements. The kinetic data fitted a pseudo-second order model for both As(III) and As(V), suggesting chemical adsorption on the sor­bent surface and that intra-particle diffusion is not the only rate-limiting step during adsorption. The adsorption isotherms were best fit to the Freundlich model, and the non-monolayer adsorption model for arsenic on Chit-FeMn is therefore proposed. Below pH 9, the effect of pH on As(III) and As(V) rem­oval by Chit-FeMn was insignificant, with As removals remaining above 85 %. Cl^- and NO₃^- had negligible influences on As(III) and As(V) removal, whereas PO₄^3-, SiO₃^2-, CO₃^2- and SO₄^2- were observed to compete with arsenic species for adsorption sites. The adsorbent was successfully applied to remove arsenic from real arsenic contaminated groundwater samples to below 10 µg L^-1 sug­gesting that Chit-FeMn is a promising candidate for the low cost removal of both As(V) and As(III) during drinking water treatment.