Glutamic acid containing supermacroporous poly(hydroxyethyl methacrylate) cryogel disks for UO₂²⁺ removal

Supermacroporous cryogel with an average pore size of 10-200μm in diameter was prepared by cryopolymerization of N-methacryloyl-(l)-glutamic acid (MAGA) and 2-hydroxyethyl methacrylate (HEMA). The poly(HEMA-MAGA) cryogel was characterized by surface area measurements, FTIR, swelling studies, elemental analysis and SEM. The poly(HEMA-MAGA) cryogel had a specific surface area of 23.2m²/g. The equilibrium swelling ratio of the cryogel is 9.68g H₂O/g for poly(HEMA-MAGA) and 8.56g H₂O/g cryogel for PHEMA. The poly(HEMA-MAGA) cryogel disks with a pore volume of 71.6% containing 878μmol MAGA/g were used in the removal of UO₂²⁺ from aqueous solutions. Adsorption equilibrium of UO₂²⁺ was obtained in about 30min. The adsorption of UO₂²⁺ ions onto the PHEMA cryogel disks was negligible (0.78mg/g). The MAGA incorporation significantly increased the UO₂²⁺ adsorption capacity (92.5mg/g). The adsorption process is found to be a function of pH of the UO₂²⁺ solution, with the optimum value being pH 6.0. Adsorption capacity of MAGA contained PHEMA based cryogel disks increased significantly with pH and then reached the maximum at pH 6.0. Consecutive adsorption and elution cycles showed the feasibility of repeated use for poly(HEMA-MAGA) cryogel disks.