In this article, graft copolymerization of N-vinyl-2-pyrrolidone onto xanthan gum initiated by potassium peroxydiphosphate/Ag+ system in an aqueous medium has been studied tinder oxygen free nitrogen atmosphere. Grafting ratio, grafting efficiency, and add on increase on increasing the concentration of potassium peroxydiphosphate (2.0 x 10(-3) to 12 x 10(-3) mol dm(-3)) Ag+ (0.4 x 10(-3) to 2.8 x 10(-3) mol dm(-3)), and hydrogen ion concentration from 2 x 10(-3) to 14.0 x 10(-3) mol dm(-3). Maximum grafting has been obtained when xanthan gum and monomer concentration were 0.4 g dm(-3) and 16 x 10(-2) mol dm(-3), respectively, at 35 degrees C and 120 min. Water swelling capacity, swelling ratio, metal ion uptake, and metal retention capacity have also been studied, and it has been found that graft copolymer shows enhancement in these properties than pure xanthan gum. The graft copolymer has been characterized by FTIR and thermal analysis. (C) 2008 Wiley Periodicals, Inc. J Appl Polym Sci 111: 2872-2880, 2009