Zinc micronutrient-loaded carboxymethyl tamarind kernel gum-based superabsorbent hydrogels: controlled release and kinetics studies for agricultural applications

Abstract

The novel zinc-loaded superabsorbent hydrogel (ZSAH) was synthesized through in situ incorporation of zinc micronutrient in carboxymethyl tamarind kernel gum cross-linked network. The synthesized ZSAH was characterized by FTIR, SEM, TGA, swelling studies, etc. and found to have good water absorption capacity (410 g/g in distilled water) and with entanglement of zinc with weak physical forces. The ZSAH thus synthesized was assessed for controlled release application in soil as well as water, to test its application in the field of agriculture. The ZSAH exhibited slow and steady release pattern of zinc with 55% release within 72 h in water, and 83% release within 80 days in soil. Under the release kinetics studies, Korsmeyer-Peppas model was found to be best explaining the zinc release pattern through ZSAH. The ZSAH followed Fickian mechanism for release and it was observed that the diffusion was independent of the structure of the polymeric network. The time for zinc release from ZSAH, predicted as per the Olson’s single exponential model, revealed significantly prolonged T99 (time for release of 99% Zn) in water (12.22 days) as also in soil (625 days). Hence, the novel synthesized ZSAH exhibited great potential as a zinc micronutrient delivery system in agriculture.