Chitosan-Lignin Cryogel Beads for the Adsorption of Diclofenac in Water

The production, use, and disposal of pharmaceuticals contribute to widespread pollution of the aquatic environment. Conventional wastewater treatment plants are not designed to completely remove bioactive pharmaceuticals such as diclofenac, posing risks to aquatic ecosystems and drinking water sources. To address this challenge, we report the production of biogenic adsorbent beads for enhanced removal of anionic contaminants from water. The beads consist of glutaraldehyde-cross-linked chitosan (or quaternary amine-functionalized chitosan) combined with lignin, and a macroporous structure was introduced via freeze-drying. The resulting cryogel beads were characterized and benchmarked against two commercially available adsorbents, an activated carbon and an ion-exchange resin. Compared to these reference materials, the presented cryogel beads exhibit significantly faster diclofenac removal kinetics and a higher adsorption capacity. Furthermore, upon treatment with a brine solution, the cryogel beads can desorb diclofenac and show good performance over five adsorption-desorption cycles. The present study demonstrates the potential of biopolymer cryogel beads as sustainable materials for water treatment.