The eect of external stimuli on the uranyl ions uptake capacity of poly(N-vinyl 2-pyrrolidone/itaconic acid) hydrogels prepared by gamma rays  O. Kanto glu a, * , M. S ß en b , O. G uven b a Turkish Atomic Energy Authority, Ankara Nuclear Research and Training Centre, Kazan, 06983, Ankara, Turkey b Department of Chemistry, Hacettepe University, 06532, Beytepe, Ankara, Turkey Abstract The eect of external stimuli such as pH of the solution, ionic strength and temperature on the uranyl ions uptake capacity of poly(N-vinyl 2-pyrrolidone/itaconic acid) (P(VP/IA)) hydrogels was investigated. Polyelectrolyte P(VP/IA) hydrogels with varying compositions were prepared in the form of rods from ternary mixtures of N-vinyl 2-pyrrolidone/ itaconic acid/water. Uranyl adsorption capacity of hydrogels were found to increase from 26.7 to 70 (mg UO 2 2 /g dry gel) with decreasing pH of the swelling solution. Adsorption studies have shown that other stimuli, such as temperature and ionic strength of the swelling solution have also in¯uence on the uranyl ions uptake capacity of P(VP/IA) hydrogels. Ó 1999 Elsevier Science B.V. All rights reserved. PACS: 82.70.G; 68.18 Keywords: Hydrogel; Poly(N-vinyl 2-pyrrolidone/itaconic acid); Adsorption; Uranyl uptake 1. Introduction Polymeric substrates are being continuously developed and used for the purpose of complexa- tion with metal ions either for ion-exchange or selective adsorption purposes. These polymeric li- gands are tailor synthesized to remove certain metal ions or groups from aqueous media. The introduction of maleic or itaconic acid type mo- nomeric units into acrylamide and N-vinyl 2- pyrrolidone based hydrogels imparted chelating properties to these hydrogels. The complexation of these diprotic acidic groups with some heavy metal ions provided an ecient way of their removal from aqueous systems by poly(acrylamide/maleic acid) hydrogels [1]. Same hydrogels were proven to be very eective in the uptake of uranyl ions from aqueous solutions [2]. A further enhancement in the uranyl ion uptake of these gels is achieved by pre-structuring them during radiation induced crosslinking process [3]. Radiation synthesis of P(VP/IA) hydrogels and their network character- ization and eect of external stimuli on the equi- librium degree of swelling were very well demonstrated in our previous studies. In this Nuclear Instruments and Methods in Physics Research B 151 (1999) 218±221 www.elsevier.nl/locate/nimb * Corresponding author. 0168-583X/99/$ ± see front matter Ó 1999 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 8 - 5 8 3 X ( 9 9 ) 0 0 1 0 1 - 9