Synthesis and Characterization of Biobased Superabsorbent Hydrogels: Cross-Linked Sodium Alginate‑g‑Poly(Potassium...

Excessive use of chemical fertilizers and petroleum-based synthetic polymers leads to low nutrient-use efficiency, environmental pollution, nonbiodegradability, and economic losses in modern agriculture. Environmentally friendly, biodegradable superabsorbent hydrogels derived from renewable biobased polysaccharides, are capable of controlled nutrient release and enhanced soil water-retention capacity. The aim of this article is to synthesize novel polysaccharide-based slow-release material designed to be applied in agriculture. The hydrogel was synthesized via graft copolymerization of potassium acrylate onto sodium alginate using N,N'-Methylenebis-(acrylamide) as a cross-linker and ammonium persulfate as an initiator in aqueous solution. The physical, chemical, structural, and morphological characteristics of the hydrogel were thoroughly investigated using solid-state ¹³C nuclear magnetic resonance (NMR), attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and energy dispersive X-ray analysis (EDX). Swelling and deswelling ratios were evaluated to characterize the water absorption and release behavior of the superabsorbent hydrogel. Compression tests were performed on samples allowed to swell for varying durations in order to assess their mechanical stability and resistance to deformation under simulated soil pressure conditions. Furthermore, the hydrogel's interactions with urea were examined by evaluating its swelling capacity in urea-containing media and monitoring the controlled release of urea over time using ultraviolet spectroscopy (UV), demonstrating its potential as a nutrient delivery system in agricultural applications. This multifunctional material has potential applications in agriculture together with active substances such as fertilizers or soil conditioners, offering enhanced efficiency and environmental sustainability.