Thermodynamics of adsorption of uranyl ions onto amidoximated poly(acrylonitrile)/poly(N-vinyl 2-pyrrolidone) interpenetrating polymer networks

The interaction of uranyl ions (UO22+) with interpenetrating polymer networks (IPNs) based on amidoximated poly(acrylonitrile)/poly(N-vinyI 2-pyrrolidone) was examined. The adsorption capacity of IPN hydrogels as well as the adsorption kinetics and the effect of temperature on UO22+ ion adsorption were investigated. Thermodynamic quantities and kinetic parameters were calculated with adsorption isotherm data. The initial adsorption-rate values for each temperature were calculated, and the corresponding rate constants decreased with increasing temperature. The adsorption enthalpy, entropy, and free energy of the UO22+ ion with., amidoximated IPN hydrogels were calculated from basic thermodynamic relations. It was assessed that adsorption occurred by strong electrostatic interactions with an adsorption enthalpy of -31.5 kJ/mol. (C) 2004 Wiley Periodicals, Inc.