Fabrication of chitosan-magnesium hydroxide hydrogels for efficient removal of copper ions

In pursuit of sustainable development, a novel chitosan-based composite gel, designated as CMgG, was successfully synthesized for removing and recovering heavy metal ions from aqueous solutions that brought about environmental contamination and engendered human health. The material was thoroughly characterized using XRD, FT-IR, SEM, and XPS. Mg(OH)₂ flakes are found effectively encapsulated by chitosan through hydrogen bonds, contributing to a stable composite gel structure. Adsorption performance was evaluated using Cu²⁺ as the target contaminant. It is shown that CMgG exhibits a high adsorption capacity of 420.7 mg g^-1 towards Cu²⁺. Notably, the removal efficiency exceeds 99 % at the initial Cu²⁺ concentration below 100 mg L^-1. Furthermore, CMgG bears excellent reusability. It maintains a removal efficiency above 99 % even after 10 consecutive adsorption-desorption cycles, indicating its outstanding long-term service life. It is revealed that the adsorbed Cu²⁺ is effectively trapped within the gel matrix in the form of Cu₄(SO₄)(OH)₆. This confirms the synergistic role of chitosan and Mg(OH)₂ in the composite, enabling simultaneous adsorption and recovery of copper ions. Meanwhile, the adsorption mechanism was fully investigated. The combination of high adsorption performance and straightforward recovery makes CMgG a robust candidate for application in the treatment of heavy metal-laden wastewater.