[Fe-Mn Binary Oxide Impregnated Chitosan Bead (FMCB): An Environmental Friendly Sorbent for Phosphate Removal]

Fe-Mn binary oxide impregnated chitosan bead (FMCB), an environmental friendly sorbent for phosphate removal, was fabricated through impregnating Fe-Mn binary oxide into chitosan matrix. The FMCB was characterized by SEM and BET surface area measurement. The adsorption behavior of phosphate on the FMCB was systemically investigated. The FMCB showed a porous and fibrous structure, with a high BET specific surface area of 248 m²·g^-1 and a pore volume of 0.37 m³·g^-1. It had a much higher phosphate adsorption capacity than pure chitosan bead. Langmuir model was more suitable for describing the adsorption behavior and the maximal adsorption capacity was as high as 13.3 mg·g^-1 at pH 7.0.The kinetic data were well fitted by the pseudo second order model. The phosphate adsorption on FMCB was pH-dependent and decreased with increasing solution pH. Coexisting Ca²⁺ and Mg²⁺ enhanced slightly the adsorption of phosphate, while the coexisting anions hindered the phosphate adsorption in the order of SiO₃^2- > CO₃^2- > SO₄^2-≥Cl^-. The phosphate-loaded FMCB could be effectively regenerated using NaOH solution and repeatedly used. In column tests, about 800 bed volumes of simulated groundwater containing 3 mg·L^-1 were treated before breakthrough (phosphate concentration in effluent reached 0.5 mg·L^-1).