Polyacrylonitrile (PAN)-grafted sodium salt of partially carboxymethylated tamarind kernel powder (Na-PCMTKP-g-PAN, %G = 413.76 and %GE = 96.48) was prepared using the established optimal reaction conditions for ceric-initiated graft copolymerization of acrylonitrile onto Na-PCMTKP (DS = 0.15) in a homogeneous medium. The graft copolymer was hydrolyzed by 0.7N KOH solution at 9095 degrees C to yield the superabsorbent hydrogel H-Na-PCMTKP-g-PAN. The nitrile groups of Na-PCMTKP-g-PAN were completely converted into a mixture of hydrophilic carboxamide and carboxylate groups during alkaline hydrolysis, followed by in situ crosslinking of the grafted PAN chains. The products were characterized spectroscopically and morphologically. The swelling behavior of the unreported superabsorbent hydrogel, H-Na-PCMTKP-g-PAN, was studied by carrying out its absorbency measurements in low-conductivity water, 0.15M salt (NaCl, CaCl2, and AlCl3) solutions, and simulated urine (SU) at different timings. The swelling behavior of the hydrogel in different swelling media followed the second-order kinetics. The values of the various swelling characteristics were reported. (c) 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013