Sustainable hydrogel from biowaste: Synthesis and characterization of pectin and starch-based hydrogels derived from fruit peel

Abstract

Arid regions such as the United Arab Emirates face persistent challenges in agricultural productivity due to water scarcity, poor soil quality, and the overuse of chemical fertilizers. As a sustainable alternative, biodegradable hydrogels offer promising solutions owing to their high swelling capacity, water retention ability, and controlled release of water and nutrients. This study explored the synthesis and characterization of eco-friendly hydrogels derived from pectin and starch extracted from orange and banana peels, respectively. These biopolymers are cross-linked using calcium and polyvinyl alcohol, forming hydrogels suitable for agricultural applications. The quality of the extracted biopolymers was assessed by analyzing moisture content, ash content, equivalent weight, solubility, and pectin methylation degree. The results confirmed high purity, with low ash contents of 2.16% (pectin) and 2.31% (starch), and moisture contents of 17.66% and 10%, respectively, indicating good stability and storage potential. The low methoxy pectin content resulted in a degree of methylation of 6.08%, which was favorable for gel formation. Structural and morphological characterization via FTIR, SEM, and SEM-EDX revealed well-defined functional groups, a highly interconnected porous morphology, and structural integrity of the hydrogels even after 20 days of biodegradation. Swelling and pot experiments demonstrated that both hydrogels effectively retained soil moisture for up to 12 days, with swelling ratios ranging from 300% to 350% of their original weight. Biodegradation studies indicated that starch-based hydrogels degraded faster (78.76% weight loss) than pectin-based hydrogels did (67%), likely due to differences in pore size and structural compactness. Overall, the results validate the feasibility of producing sustainable, biodegradable hydrogels from fruit peel waste, with significant potential for water conservation and soil enhancement in arid agricultural systems.