Micronutrient-loaded biopolymer as slow-release behavior

Hydrogels are 3-dimensional cross networked polymeric materials that can absorb and retain a large amount of water. Nature-derived hydrogels are biodegradable, low cost, non-toxic and biocompatible. Here we developed agricultural waste-derived hydrogel in which cellulose was extracted from rice straw and Carboxymethyl Tamarind Kernel Gum (CMTKG) (made from tamarind’s seed) was collected from market. CMTKG and Rice Straw Cellulose (RSC)-based superabsorbent hydrogels by in situ incorporation of Copper (Cu) were synthesized by graft copolymerization using epichlorohydrin as a crosslinker. Cu-loaded CMTKG-RSC superabsorbent hydrogel (CSH) was applied as a carrier vehicle for Cu micronutrient release for applications in the field of agriculture. The synthesized CSH was characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), and UV–visible spectrophotometer analysis. The prepared CSH was analyzed regarding its swelling, deswelling, water retention, recyclability, and biodegradation. The synthesized CSH observed to have a water absorption capacity (663 – 832% in distilled water) with entanglement of Cu with weak physical forces. The water absorption kinetics exhibited that the rate-controlling step was Fickian diffusion, revealing a slower diffusion rate of water transport into the hydrogel network. The CSH showed a slow release of Cu with ~80% release within 184 h in distilled water. Different kinetic models were studied to observe the release kinetic parameters. The Peppas–Sahlin model was the best-fitted model among all studied models, revealing Cu release controlled by Cu diffusion with polymeric relaxations. Considering these findings, the synthesized hydrogel can be used as a water reservoir for agriculture and reducing irrigation in plants. Slow release of micronutrients (such as Cu) from CSH also enhances the plant growth.