Freeze-thaw synthesis of potassium copper hexacyanoferrate immobilized magnetic hydrogel for the effective removal of Cesium

Abstract

The magnetic hydrogel (KCuHCF/Fe3O4/PVA) was synthesized with a simple procedure using non-toxic and cost-effective precursors for adsorption of Cs$^+$ in aqueous solutions. Freezing/thawing the binding matrix of poly(vinyl) alcohol was utilized for good mechanical property and easy molding. The citric acid coated Fe$_3$O$_4$ was added into the hydrogel matrix (MHPVA-gel) for facilitating the dispersion of nano-sized KCuHCF particles and rapid separation from the aqueous solution by using magnetic field. The adsorption behavior of MHPVA-gel was fitted well with the Langmuir-Freundlich isotherm and the pseudo-second-order kinetic model. The MHPVA-gel exhibited both-high Cs$^+$ adsorption capacities (101.63 mg/g) and distribution coefficient Kd value (1.18 x 106 mL/g at 8.3 ppm Cs$^+$). Sorption of 96% Cs$^+$ to MHPVA-gel was finished in less than 4h (at 8.3 ppm Cs$^+$). In terms of selectivity, the MHPVA-gel showed above 98% removal efficiency in 0.1M competing cations condition at 1 ppm Cs$^+$. Moreover, the MHPVA-gel exhibited the high Kd value (4.77 x 104 mL/g) in seawater at 1 ppm Cs$^+$ which was more competitive condition with other ions. The MHPVA-gel is a promising material for treating radioactive waste water containing cesium ions.