Cellulose-based hydrogels derived from wastepaper for slow release of urea in chilli pepper cultivation

Conventional fertilizers often release nutrients too rapidly, leading to nutrient leaching, reduced fertilization efficiency, and environmental pollution of nearby water sources. To address this challenge, this study developed a slow-release urea system using hydrogels synthesized from recycled wastepaper. Cellulose fibers derived from wastepaper were blended with polyvinyl alcohol (PVA) as a network-forming component, carboxymethyl cellulose (CMC) as a binder, and epichlorohydrin (ECH) as a crosslinking agent to prepare cellulose-based hydrogels. Among the tested formulations, the cellulose/CMC/PVA hydrogel with a 3:3:4 ratio (CCP334) showed the highest swelling capacity and was selected for urea loading studies. Urea, used as a model fertilizer, was incorporated at different concentrations to determine the optimal loading conditions. The cellulose hydrogel exhibited a maximum loading capacity of 54.10% at 2.5% urea concentration. Release studies conducted in distilled water, topsoil, and coco peat demonstrated a sustained nutrient delivery: 86.25% release in water (10 days), 63.13% in coco peat (20 days), and 86.88% in topsoil (60 days). The release behavior followed the Korsmeyer–Peppas model with n values < 0.45, indicating Fickian diffusion.