Preparation, swelling behaviors and application of polyacrylamide/attapulgite superabsorbent composites

A series of superabsorbent composites, polyacrylamide/attapulgite (PAMA), were prepared from acrylamide (AM) and attapulgite micropowder in aqueous solution, using N,N'-methylenebisacrylamide (MBA) as a crosslinker and ammonium persulfate (APS) as an initiator and then saponified with sodium hydroxide solution. This paper focuses on swelling behaviors of the PAMA superabsorbent composites in various saline solutions. The results indicate that saline solutions can weaken the swelling abilities of the PAMA compsites greatly. Water absorbency of the PAMA composites with 20 and 40 wt% attapulgite in aqueous chloride salt solutions has the following order: Li+=Na+=K+, Mg2+>Ca2+=Ba2+ all through the range of concentration investigated. However, swelling properties of the composites are complicated in CuCl2(aq), AlCl3(aq) and FeCl3(aq) solutions and are related to saline solutions concentration. The deswelling behavior of PAMA composites is more obvious in univalent chloride salt solutions than in divalent and trivalent ones. The influence of kind and valence of anions on swelling ability of the composites is limited and almost the same. Moreover, reswelling capability, practical water retention ability in sand soil of the composites and the effect of pH on water absorbency of the PAMA composites were investigated. The PAMA composite shows good water retention and reswelling ability in sand soil, and may be used as a recyclable water-managing material for the renewal of and and desert environment. Copyright (C) 2006 John Wiley & Sons, Ltd.