Fabrication and swelling properties of a novel superabsorbent composite derived from waste coal gangue

In this work, novel superabsorbent composites made of starch-grafted-polyacrylic acid/coal gangue were prepared via aqueous solution polymerization. The starch-g-polyacrylic acid/coal gangue (St-g-PAA/CG) composite with 10 wt.% CG showed the maximum water absorbency in distilled water (560 g·g−1) and a 0.9 wt.% NaCl solution (102 g·g−1). Moreover, this superabsorbent composite exhibited fine thermal stability and its swelling behavior was dependent on pH. In general, the swelling kinetics of the superabsorbent composites fitted with the Scott’s kinetic model. These composites not only showed excellent water absorption reversibility after five absorption/drying cycles, but also exhibited considerable environmental responsiveness after the swelling medium was changed from distilled water to the 0.9 wt.% NaCl solution. Based on these results, the prepared superabsorbent composites can be applied in several fields such as horticulture, agriculture, health care, and controlled drug delivery, while ensuring comprehensive utilization of solid wastes.