From Ionotropic Gelation of Chitosan to Reusable Magnetic Sorbents for Wastewater Treatment

Chitosan, a bio-based polymer derived from chitin, has attracted significant interest as a sustainable platform for advanced sorbent materials. Ionotropic gelation using sodium tripolyphosphate (TPP) was employed to produce chitosan-based beads with controlled morphology, porosity, and stability in aqueous environments. This mild, water-based method enables the rapid formation of hydrogel-like structures through electrostatic interactions between the protonated amino groups of chitosan and the phosphate groups of TPP, eliminating the need for toxic cross-linkers and preserving the biocompatibility of the system.

To further enhance functional performance, novel engineered spinel ferrite nanoparticles were incorporated into the chitosan matrix during gelation, generating magnetic responsiveness. The resulting hybrid beads were systematically characterized in terms of structural integrity, porosity, and magnetic behavior. Optimization of the gelation parameters—particularly the chitosan/TPP ratio and the influence of surfactants—proved essential for tailoring the beads’ textural properties, surface area, and adsorption capacity.

Adsorption experiments using representative organic pollutants (synthetic dyes) confirmed that the porous, magnetically responsive beads act as efficient sorbents, combining high removal efficiency with easy recovery from aqueous medium. Regeneration studies further demonstrated reusability over multiple adsorption–desorption cycles without significant loss of performance.

Overall, the results emphasize ionotropic gelation as a versatile, sustainable, and scalable strategy for developing functional chitosan-based gels. By integrating magnetic nanoparticles, this approach enables the recovery and reuse of the sorbents, contributing to circular and environmentally friendly solutions for wastewater treatment.