Influence of potassium humate on the swelling properties of a poly(acrylic acid-co-acrylamide)/potassium humate superabsorbent composite

A novel superabsorbent composite, poly (acrylic acid-co-acrylamide)/potassium humate (PAA-AM/KHA), was prepared by aqueous solution polymerization from acrylic acid, acrylamide, and potassium humate (KHA) with N,N'-methylenebisacrylamide as a crosslinker and potassium peroxydisulfate as an initiator. The effects of incorporated KHA on the water absorbency, swelling rate, and reswelling capability were investigated. The swelling property of PAA-AM/KHA in various saline solutions was studied systematically. The results show that the comprehensive properties and especially salt-resistant ability of PAA-AM/KHA were enhanced. There was a linear relationship between the saturated water absorbency and the minus square root of the ionic strength of the external medium, and the water absorbency of PAA-AM/KHA in various salt solutions had the following order: NH4Cl(aq) = KCl(aq) = NaCl(aq) > MgCl2(aq) > CaCl2(aq) > AlCl3(aq) > FeCl3(aq). Moreover, the polymeric net structure of PAA-AM/KHA was examined with respect to that of poly(acrylic acid-co-acrylamide). The results indicate that the polymeric net of PAA-AM/KHA was improved by the introduction of a moderate amount of KHA into the superabsorbent composite and made more suitable for agriculture and horticulture applications. (C) 2007 Wiley Periodicals, Inc.