In this study, uranyl ion adsorption from aqueous solutions has been investigated by chemically crosslinked acrylamide/sodium acrylate (CASA) hydrogels. Adsorption studies were investigated by the spectroscopic method. CASA hydrogels with various compositions were prepared from ternary mixtures of acrylamide (A), sodium acrylate (SA), and water by free radical polymerization in aqueous solution, using multifunctional crosslinkers such as ethylene glycol dimethacrylate (EGDMA). Uranyl ion adsorption from aqueous solutions was studied by the batch sorption technique at 258C. The effect of uranyl ion concentration and mass of adsorbent on the uranyl ion adsorption were examined. In experiments of sorption, L-type sorption in the Giles classification system was found. Some binding parameters, such as initial binding constant (K i ), equilibrium constant (K), monolayer coverage (n), site-size (u), and maximum fractional occupancy (Ô ) for the CASA hydrogel-uranyl ion binding system, were calculated using the Langmuir linearization method. Finally, the amount of sorbed uranyl ion per gram of dry hydrogel (q) was calculated to be 4.44 Â 10 À4 -14.86 Â 10 À4 mol uranyl ion per gram for CASA hydrogels. Adsorption of uranyl ion (percentage) was changed within a range of 12.86-46.71%.

ABSTRACT:A series of chemically cross-linked hybrid composite hydrogel systems containing polysaccharide/clay polyelectrolyte based on the acrylamide/sodium methacrylate (AAm/SMA) and ɩ-carrageenan and clay such as montmorillonite were synthesized with free radical solution polymerization by using ammonium persulfate/N,N,N',N'-tetramethylethylenediamine as a redox-initiating pair in the presence of poly(ethylene glycol) diacrylate as a cross-linker. Fourier transform infrared spectroscopy (FT-IR) analysis and scanning electron microscopy (SEM) technique were applied for characterization. The hydrogels, the semi-interpenetrating polymer networks (semi-IPNs), and the hybrid composite hydrogel systems that were synthesized in this study have shown high water absorbency. Some swelling and diffusion properties were calculated, and they were discussed for the hybrid hydrogel systems prepared under various formulations. They were used in experiments on sorption of water-soluble cationic dye such as Safranin T (ST). The sorption of ST into the polymeric systems was studied by a batch sorption technique at 25°C. For equilibrium sorption studies, dye removal capacity, adsorption percentage, and partition coefficient of the hydrogels, the semi-IPNs, and the hybrid composite hydrogel systems are investigated. Consequently, the hydrogels, the semi-IPNs, and the hybrid composite hydrogel systems developed in this study could serve as a potential device for water and dye sorbents. Some materials such as the hydrogels, the semi-IPNs, and the hybrid composite hydrogel systems developed in this study with the ability to absorb water in high amounts could be used as a water and dye sorbents because of their potential applications in agriculture, environment, separation processes, and water purification. C

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In this report, uranyl ion sorption performance from aqueous solutions has been investigated by highly swollen novel polymer/clay-composite biosorbent-based acrylamide (AAm)/2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) hydrogels and semi-IPNs composed of carboxymethyl cellulose (CMC) and/or montmorillonite (MMT). For this, AAm/AMPS hydrogels with CMC and/or MMT were prepared by free radical polymerization in an aqueous solution of monomers, CMC and MMT using ammonium persulfate/N,N,N',N'-tetramethylethylenediamine as a redox-initiating pair in the presence of poly(ethylene glycol)diacrylate as a cross-linker. Swelling experiments were performed in water at 25°C, gravimetrically. Some swelling kinetic and diffusion parameters were calculated. Water diffusion was found to be non-Fickian in character. The sorption performance of uranyl ions into the hydrogels was studied by a spectrophotometric method at 25°C. Sorption capacity, removal efficiency, and partition coefficient of the hydrogels were investigated. Removal efficiency was changed within a range of 20.52-67.68%.

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