MBA-crosslinked Na-Alg/CMC as a smart full-polysaccharide superabsorbent hydrogels

A novel superabsorbent hydrogel composed of carboxymethylcellulose (CMC) and sodium alginate (Na-Alg) was prepared by using methylenebisacrylamide (MBA) as a crosslinking agent. Ammonium persulfate (APS) was used as an initiator. For investigation of the effect of reaction variables on water absorbency of the hydrogels, the synthetic conditions were systematically optimized through studying the influential factors, including temperature, Na-Alg/CMC weight ratio and concentration of MBA and APS. Increase in MBA and APS concentration results in the decrease in water absorbency of the hydrogels. The water absorbency of the hydrogels increased with increasing of reaction temperature and Na-Alg/CMC weight ratio up to 85 °C and 0.54, respectively. The hydrogel was identified using FT-IR spectroscopy and SEM pattern. These behaviors were discussed according to structural parameters. The influence of variables such as pH, particle size and MBA concentration on the swelling kinetics of the hydrogels was investigated. The water absorbency of these hydrogels in various salt solutions was studied. The tendency of the absorbency for these hydrogels in salt solutions is in the order Na+ > Ca2+ > Al3+ for NaCl, CaCl2 and AlCl3 aqueous salt solutions. The results showed that the water absorbency for the hydrogels in monovalent cations salt solutions is in order LiCl > NaCl > KCl. Crosslinked Na-Alg/CMC hydrogels exhibited a reasonable sensitivity to the pH.