Chitosan-based hydrogel system for efficient removal of Cu[II] and sustainable utilization of spent adsorbent as a catalyst for environmental applications.

The growing requirement for clean potable water requires sustainable methods of eliminating heavy metal ions and other organic contaminants. Herein, we synthesized a novel dual-purpose magnetically separable chitosan-based hydrogel system (CSGO-R@IO) that can efficiently remove toxic Cu pollutants from water. FT-IR, XRD, SEM-EDX, VSM, XPS analyses were used to characterize the synthesized hydrogel. The CSGO-R@IO hydrogel showed high swelling capacity (1036.06 %), prominent adsorption capacity for Cu ions (119.5 mg/g), and good recyclability up to four cycles. The adsorption data of Cu ions on hydrogel fitted better to the Langmuir isotherm model (R = 0.9942), indicating spontaneous monolayer adsorption of Cu ions on a homogenous surface. The adsorption kinetic studies fitted better with the pseudo-second-order model (R = 0.9992), suggesting that the adsorption process was controlled by chemisorption. We also showed a sustainable way to convert harmful Cu pollutants into valuable Cu nanoparticles for catalysis, and Cu nanoparticles loaded hydrogel (CSGO-R@IO/Cu) had high catalytic activity. Hence, building attractive multipurpose hydrogel systems will give us new ideas about how to design and use new adsorbents to clean water in real life. They will also help in recycle metals (copper and maybe others) to conserve resources.