Durability Indicatives of Hydrogel for Agricultural and Forestry Use in Saline Conditions

This research tested the hypothesis that the interaction between time and salinity reduces the water absorption potential of a hydrogel - Poly (Acrylamide-co-Potassium Acrylate) and influence the degradation of residual acrylamide monomer. The experimental design was completely randomized split-plot with four replications. The treatments were time periods (30, 60, 90 and 120 days) and levels of salinity of the hydrating solution (distilled water = 0.003, 0.5; 1.5; 3.0 and 6.0 dS m-1). Swelling, hydrogel composition, and residual acrylamide monomer concentration were evaluated. The hydrogel showed lowest water absorption potential (8.1 g g-1) in a saline solution of 4.20 dS m-1 after 120 days. The C/N ratio of the hydrogel increased by up to 47% in a hydrating solution with an EC of 4.4 dS m-1 at 120 days. Additionally, there was an observed shift in the wavelength of methylene, amide, and acrylate bands, that indicates degradation. Residual acrylamide monomer concentration was <0.5 mg g-1 (safe for agricultural use). After 120 days up to 85% of the residual acrylamide monomer was degraded. About the water absorption potential, the results suggest that under semi-arid conditions hydrogel durability for forestry and crops applications may be impaired by the salinity of the hydrating solution.