Genipin-Crosslinked Water Hyacinth/Chitosan Sponges as Green Adsorbents for Reactive Dye Removal

Bio-based adsorbents for removing pollutants were prepared using composite sponges with porosities greater than 80%. Herein, we report for the first time the preparation of macroporous sponges via freeze-drying of a chitosan solution and water hyacinth fiber (WHF). Genipin, a chemical crosslinker, was utilized in the process. The results showed that genipin increased the resistance to compression of the sponges while also improving their water and thermal stability. The composite sponges effectively removed C.I. reactive orange 16 (RO16) from water, with adsorption capacities ranging from 37.86 to 95.77 mg/g at pH 7. After 24 h, nearly complete dye removal was achieved with an initial dye concentration of 20 mg/L and an adsorbent dose of 2.5 g/L. The adsorption isotherm followed the Freundlich model, and the adsorption kinetics followed the pseudo-second-order model. The WHF/chitosan sponge could be reused for up to four cycles. These findings demonstrate the potential of the prepared sponges as bio-based adsorbents for the treatment of dye-contaminated wastewater.