Carboxymethyl cellulose and gelatin composite hydrogel for environmentally friendly urea delivery

Abstract

The global agricultural expansion drives a rising demand for urea-based fertilizers, yet the widespread issue of rapid leaching challenges farmers, diminishing efficacy. This study aimed to develop a hybrid hydrogel from carboxymethyl cellulose (CMC) and pharmaceutical waste gelatin (GE), using glutaraldehyde (GA) as a cross-linking agent for slow release of urea fertilizer. The effects of CMC to GE mass ratios, GA concentration, and urea loading methods on hydrogel production were studied. CMC and GE solutions were mixed, cross-linked for 24 h at room temperature, and dried at 60 °C for 48 h. SEM analysis revealed increased urea particles in the hydrogel with higher urea content. FT-IR spectroscopy confirmed CMC, GE, and urea presence, with the urea functional group becoming more apparent as the urea content increased. Higher GA concentrations resulted in slower urea release in water. The best sample was the 1:3 CMC:GE-5 G/6 U, with a CMC to GE ratio of 1:3, a GA concentration of 5% by volume, and the direct addition of 6 g of urea during hydrogel formation. This sample had a urea loading of 51.25% and cumulative release of 80.71%. Notably, it exhibited sustained urea release over 17 cycles compared to commercial urea’s three cycles.