A novel biopolymer-based superabsorbent hydrogel was synthesized through chemical crosslinking by graft copolymerization of partially neutralized acrylic acid onto the hydrolyzed collagen, in the presence of a crosslinking agent and a free radical initiator. The Taguchi method, a robust experimental design, was employed for the optimization of the synthesis reaction based on the swelling capacity of the hydrogels. This method was applied for the experiments and standard L-16 orthogonal array with three factors and four levels were chosen. The critical parameters that have been selected for this study are crosslinker (N,N'-methylene bisacrylamide), initiator (potassium persulfate), and monomer (acrylic acid) concentration. From the analysis of variance of the test results, the most effective factor to control equilibrium swelling capacity was obtained and maximum water absorbency of the optimized final product was found to be 500 g/g. The surface morphology of the gel was examined using scanning electron microscopy. Furthermore, the sorption capacity of the hydrogel toward bivalent metal ions was evaluated. Therefore, the hydrogel may be considered as a candidate to develop as an efficient biopolymer-based chelating hydrogel for water treatment. (c) 2006 Wiley Periodicals, Inc.