Graft copolymer of k-carrageenan and N,N-dimethylacrylamide has been synthesized by free radical polymerization using peroxymonosulphate/glycolic acid redox pair in an inert atmosphere. The grafting parameters i.e. grafting ratio, add on and efficiency decrease with increase in concentration of k-carrageenan from 0.6 to 1.4gdm⁻³ and hydrogen ion from 3×10⁻³ to 7×10⁻³moldm⁻³, but these grafting parameters increase with increase in concentration of N,N-dimethylacrylamide from 16×10⁻² to 32×10⁻²moldm⁻³, and peroxymonosulphate from 0.8×10⁻² to 2.4×10⁻²moldm⁻³. The metal ion sorption, swelling behaviour and flocculation properties have been studied. The intrinsic viscosity of pure and grafted samples has been measured by using Ubbelohde capillary viscometer. Flocculation capability of k-carrageenan and k-carrageenan-g-N,N-dimethylacrylamide for both coking and non-coking coals has been studied for the treatment of coal mine waste water. The graft copolymer has been characterized by Infrared (IR) spectroscopy and thermogravimetric analysis.