The hydrogel-sorbent composite beads of potassium cobalthexacyanoferrate (KCoHCF) were synthesized for separation of cesium from waste generated in the nuclear industry. Cross-linked sodium alginate, containing PVA, was used as a binding matrix for the synthesis of spherical beads of 2 mm diameter.The characterization of these beads was carried out, using TGA, SEM and BET surface area analysis techniques, which indicated the highly porous and hydrophilic nature of the beads. The sorption of cesium ions onto these synthesized beads was studied, using a radiotracer technique. To determine equilibrium sorption and kinetic parameters for different initial cesium ion concentrations, all the studies were conducted by a batch method. The experimental data were analyzed, using the different sorption isotherms, and found to be described the best by a Langmuir sorption isotherm. The monolayer capacity of KCoHCF-gel beads is found to be 15 mg g À1 of the dry beads. Sorption kinetics data were analysed, using different kinetic models. The results show that the sorption follows pseudo second-order reaction kinetics. The initial sorption rate and the rate constants for the pseudo first-order, pseudo second-order and intraparticle diffusion were evaluated, and discussed for different initial concentrations in the range 1-20 mg L À1 . The mechanism of the sorption of cesium ions onto the synthesized beads was also investigated and film diffusion was found to be the rate determining step.

A novel synthetic approach has been used to prepare sorbent hydrogel composite beads of potassium nickel hexacyanoferrate (KNiHCF), using PVA and cross-linked alginate as the binding matrix. The characterization study indicates the high hydrophilicity and high surface area of the synthesized beads. The application potential of these beads for removal of cesium ions from low level liquid nuclear waste has been studied in batch mode using a 137 Cs radiotracer. The equilibrium sorption and kinetic data are obtained at different initial cesium ion concentrations. These data are analysed using various sorption isotherm and kinetic models. It is observed that the sorption process can be best described by the Langmuir isotherm model, and the monolayer capacity of the beads is determined to be 7 mg per g of the swollen beads, which corresponds to~64 mg per g of the dry beads. The sorption of cesium ions onto the sorbent beads is found to follow pseudo second-order kinetics over the entire studied concentration range. The ion-exchange mechanism involves the exchange of cesium ions with potassium ions. The mechanism of the sorption process is also investigated using the intraparticle diffusion model and Boyd's plot, and the results indicate that the sorption of cesium ions onto the beads is a complex process, involving both intraparticle diffusion and film diffusion.

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