Effect of various environmental conditions on the swelling property of PAAm/PAAcK superabsorbent hydrogel prepared by ionizing radiation

Polyacrylamide/potassium polyacrylate (PAAm/PAAcK) superabsorbent hydrogels were prepared by using ionizing radiation for possible use in agricultural purposes. The influence of environmental conditions such as water quality, fertilizer salts, soil pH, and surrounding temperature on PAAm/PAAcK water absorbency and retention was investigated. The water absorbency apparently decreased with an increase in the valence and ionic strength of the salt solutions. The swelling of PAAm/PAAcK immersed in the solutions containing fertilizer of different nitrogen sources followed the order: Urea > NH4NO3 > (NH4)(2)SO4. The PAAm/PAAcK water absorbency in solutions containing different types of phosphate sources was in the order: H3PO4 > KH2PO4 > K2HPO4. However, the water absorbency of PAAm/PAAcK in the solution of different types of potassium salts followed the order: KCl > K2SO4 > K2HPO4. PAAm/PAAcK hydrogel is fully swollen at pH 6. The relation between the ability of PAAm/PAAcK to retain water against time at different temperatures was studied. As the environmental temperature increases, the water retention of PAAm/PAAcK decreases. Potential application of PAAm/PAAcK in agriculture was evaluated. (c) 2006 Wiley Periodicals, Inc.