Synthesis, characterization and swelling behavior of superabsorbent wheat straw graft copolymers

Swelling behavior is an important characteristic for superabsorbents. A wheat straw-based superabsorbent (WS-SAB) was prepared by graft copolymerization of acrylic acid, acrylic amide and dimethyl diallyl ammonium chloride onto the cellulose of wheat straw, and its swelling and deswelling behavior was investigated. The product had a water absorbency of 133.76 g/g in distilled water and 33.83 g/g in 0.9 wt.% NaCl solution. Fourier transform infrared spectroscopy and scanning electron microscopy indicated that the monomers were successfully grafted onto the wheat straw. The largest swelling capacity was at pH 6. The effect of ions on the swelling was in the order: Na+ > K+ > Mg2+ > Ca2+ and Cl->SO42-. The swelling capacity did not change after several times of water absorption and release.