Durability indicatives of hydrogel for agricultural and forestry use in saline conditions

Abstract

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.