Efficient removal of Cd2+ ion from water by calcium alginate hydrogel filtration membrane

Abstract

Calcium alginate (CaAlg) hydrogel filtration membrane was prepared using urea as pore-forming agent. The effects of preparation and operating conditions on the removal rate of Cd²⁺ were researched. The removal mechanism of Cd²⁺ and the anti-fouling property of CaAlg membrane were investigated. The removal rate of the CaAlg filtration membrane reached over 99.5% within 120 min when 20 mg/L Cd²⁺ was used, and the flux was 15.5 L/m²h at 0.1 MPa when the thickness of the membrane was 0.28 ± 0.08 mm. However, the removal rate of Cd²⁺ was below 10.0% when the same concentration Cd²⁺ solution was adsorbed by CaAlg membrane with the same size. Energy dispersive spectroscope analysis demonstrated that the removal of Cd²⁺ depended on the adsorption and ion exchange of Ca²⁺ by Cd²⁺. CaAlg membrane exhibited a higher removal rate for Cd²⁺ (almost 100%). It was the filtration process that promoted the adsorption and ion exchange of Cd²⁺ in CaAlg hydrogel.