Novel biopolymeric chitosan-urea-based core-shell hydrogel for use in sustainable agriculture

Abstract

Agricultural sustainability is a major issue in recent times, deficiency of water as well as insufficient fertilizer to the crop is a main reason for it. This work is focused on core-shell hydrogel aiming to overcome the agricultural issues of water as well as deficiency of fertilizer to the plant. The core-shell hydrogel was prepared by incorporating urea in κ-carrageenan to be part of the controlled release mechanism of the core of the hydrogel. Chitosan was used for the shell structure to prepare over the core and cross-linked by the cations of the salts. The prepared hydrogel was termed as Chitosan-κ-carrageenan-Urea (CK-CU). Four different types of hydrogels were prepared with the different compositions named as CK-CU 2, CK-CU 5, CK-CU 7.5 and CK-CU 10 as varying with the ratio of 2 %, 5 %, 7.5 % and 10 % of urea respectively. The core-shell morphology structure was verified with Scanning electron microscopy (SEM) in which the complete coverage of the κ-carrageenan core by a consistent chitosan shell has been verified. Fourier transform infrared spectroscopy (FTIR) was utilized to confirm the composition of the hydrogel. Thermo-gravimetric analysis (TGA) was also performed for checking the thermal endurance of the hydrogel. The release rate of the urea was determined under Ultraviolet Visible spectroscopy. The swelling index, dewatering, and urea release rate of optimized CK-CU 10 hydrogel were found to 121 %, 21.22 %, and 70.4 % respectively. The developed Core-Shell hydrogel exhibits significant promise as a vehicle for fertilizer and as a soil conditioner in agricultural applications especially in arid and semi-arid areas.