A novel hydrogel was prepared from industrial waste to form a green polymer with a higher swelling capacity. This hydrogel was synthesized by two methods for chemical crosslinking, namely crosslinking by radical polymerization and crosslinking by addition reaction. In crosslinking by radical polymerization, graft copolymerization of poly(vinyl alcohol) (PVA) and polyacrylamide (PAAm) was carried out using ceric ammonium sulfate in presence of N,N',-methylenebisacrylamide, and then mixed with the black liquor resulting from alkaline pulping of rice straw. While, in crosslinking by addition reaction, the same above reagents were mixed with the black liquor in absence of the initiator. The black liquor is an industrial waste resulting from the pulping method and consists of dissolved lignin and carbohydrates. The black liquor causes environmental water pollution due to its dumping into the sea. The formed hydrogels were characterized using FT-IR spectroscopy and scanning electron microscopy (SEM). It was noted that the hydrogel prepared by radical polymerization showed high swelling capacity, 60.00%, compared to that prepared by the addition reaction, 27.27%. The hydrogels formed were used also to study the influence of sodium chloride on the absorption capacity at room temperature and swelling ratios at different temperatures and pHs. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012