In this article, the synthesis of kappa-carrageenan-g-methacrylic acid has been reported by free radical polymerization initiated by Potassium peroxymonosulphate/glycolic acid redox pair under nitrogen atmosphere. The reaction conditions have been optimized by varying the reaction conditions, including the concentration of monomer, peroxymonosulphate, glycolic acid, sulphuric acid, kappa-carrageenan along with reaction time and temperature. It has been observed that the maximum yield has been obtained at time 120 min, temperature 40 degrees C, at 20 x 10(-2) mol dm(-3) concentration of methacrylic acid, 1.0 g dm-3 concentration of kappa-carrageenan and 16 x 10(-3) mol dm(-3) concentration of per-oxymonosulphate. The graft copolymer is characterized by Forier Transform Infrared Spectroscopy and Thermal analysis. Water swelling capacity of graft copolymer has been determined. Intrinsic viscosity has been obtained for both grafted and ungrafted kappa-carrageenan. Metal ion sorption and flocculation performance of synthesized graft copolymer has been studied with respect to the ungrafted substrate. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 114: 3896-3905, 2009