Preparation and slow‐release property of a poly(acrylic acid)/attapulgite/sodium humate superabsorbent composite

A novel poly(acrylic acid)/attapulgite (APT)/sodium humate (SH) superabsorbent composite was synthesized through the graft copolymerization reaction of acrylic acid on APT micropowder and SH with N,N′‐methylene bisacrylamide as a crosslinker and ammonium persulfate as an initiator in an aqueous solution. Various effects on the water absorbency, including the amounts of the crosslinker, initiator, APT, and SH, were investigated. The superabsorbent composite was characterized with Fourier transform infrared spectroscopy and scanning electron microscopy. The superabsorbent composite synthesized under optimal synthesis conditions with an APT concentration of 20% and an SH concentration of 20% exhibited absorption of 583 g of H₂O/g of sample and 63 g of H₂O/g of sample in distilled water and in a 0.9 wt % NaCl solution, respectively. The slow‐release property of SH from the superabsorbent composite into water was measured, and a test of the water retention of the superabsorbent composite in soil was also carried out experimentally with and without the superabsorbent composite. The results showed that the superabsorbent composite had not only good water retention but also an additional slow‐release property of SH. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 37–45, 2007