Crosslinking of Tannin and Cassia fistula Gum Engenders a Smart Hydrogel for Controlled Release of Thiamethoxam

In this study, Cassia fistula (CF) gum and Tannin from Acacia catechu (ACT), potentially used to produce CFAC-g-SAH for effective controlled-release of agrochemicals. The synthesized hydrogels were thoroughly characterized by 13C NMR, FT-IR, SEM, XRD, and TGA. CFAC-g-SAH was compared with ACT and CF hydrogels. The swelling studies of the synthesized hydrogel were measured by varying amounts of crosslinker and biopolymer, yielding the highest swelling for CFAC-g-SAH 185 g·g−1. Release kinetics of synthesized hydrogels were studied by the Korsmeyer–Peppas, Higuchi and first-order kinetics models. The loading percentages of thiamethoxam were 58.49, 36.39, and 42.43% for CFAC-g-SAH, CF-g-SAH, and ACT-g-SAH, respectively. The CFAC-g-SAH hydrogel outperformed ACT-g-SAH and CF-g-SAH in highest swelling and longest release duration. A sustained release up to 40 h was achieved using CFAC-g-SAH, followed by a non-Fickian release mechanism. Thus, the synthesized CFAC-g-SAH emerges as a promising controlled-release device for agrochemicals with the potential to mitigate the environmental impact of pesticides.