Transforming watermelon (Citrullus lanatus) rind into durable superabsorbent hydrogels for enhanced soil water retention properties and adsorbs dye in water

Innovative superabsorbent hydrogels were synthesized from watermelon rind (WR), an abundant agricultural waste. The process involved free radical polymerization of acrylic acid (AA) and acrylamide (AAm) with WR particles activated by ammonium persulfate (APS), resulting in (AA-co-AAm)/WR hydrogels with high equilibrium swelling capacities of 749 ± 32 g/g. Notably, after eight cycles, the WR hydrogel maintained 94.88 % of its initial swelling capacity, significantly outperforming the (AA-co-AAm) hydrogel without WR (13.80 % retention). This durability, combined with excellent water retention across various soil textures and high adsorption capacity for methylene blue (MB), underscores the WR hydrogel as a superior soil moisture conservation agent. This study marks a significant advance in recycling organic waste and enhancing water management in agricultural soils, demonstrating the potential for sustainable hydrogel development. [Display omitted] •This new type of watermelon rind hydrogel has higher water-absorbent properties (749 ± 32 g/g).•The involvement of watermelon rind in the preparation of hydrogels can improve the service life of hydrogels.•The novel hydrogel in this study significantly improves soil's water retention performance.•Watermelon rind hydrogel adsorbed up to 1800 mg/g of methylene blue dye.