Synthesis and characterization of multifunctional poly(acrylic acid-co-acrylamide)/sodium humate superabsorbent composite

A novel multifunctional superabsorbent composite from acrylic acid (AA), acrylamide (AM) and sodium humate (SH), PAA-AM/SH, was prepared by aqueous solution polymerization, using N,N′-methylenebisacrylamide as a crosslinker and ammonium persulfate as an initiator. In this paper, factors influencing water absorbency of the superabsorbent composite were investigated, and then the optimal synthesis conditions were obtained as follows: the amount of crosslinker, initiator and humate, molar ratio of AA to AM, initial monomer concentration and neutralization degree of AA were 0.10 wt%, 0.40 wt%, 30 wt%, 1.2 mol mol−1, 2.02 mol L−1 and 50%, respectively. Water absorbencies for the superabsorbent composite in distilled water and in 0.9 wt% NaCl solution were investigated. Results obtained from this study indicate that the multifunctional superabsorbent composite with a humate content of 30 wt% exhibited a maximum water absorbency of 1100 g g−1 in distilled water and 55 g g−1 in 0.9 wt% NaCl solution, respectively. Thermal stability and polymerization process of the crosslinked superabsorbent composite were characterized by thermogravimetric analysis and FTIR, respectively.