Mercury pollution in aquatic systems poses a critical environmental challenge due to its high mobility, toxicity, and bioaccumulation potential. In this study, the synthesis of floating alginate–bentonite (FAB) and floating alginate– β -zeolite (FAZ) composites was optimized using a central composite design, with buoyancy as the key functional parameter to facilitate material recovery and large-scale applicability. The composites were comprehensively characterized by X-ray diffraction, attenuated total reflectance–Fourier transform infrared spectroscopy, thermogravimetric and differential thermogravimetric analysis, field emission scanning electron microscope, N 2 adsorption–desorption isotherms, and pH p zc analysis (point of zero charge), and subsequently evaluated for Hg(II) adsorption. The optimized formulations, FAB 1.0 and FAZ 1.0 , exhibited buoyancies above 98% and adsorption capacities of 33 and 28 mg g −1 , respectively, under single-cycle operation. Notably, both materials showed a marked improvement in removal efficiency upon reuse, reaching 93% for FAB 1.0 and 71% for FAZ 1.0 after three adsorption–desorption cycles. Spectroscopic and thermal analyses revealed specific interactions between alginate carboxylate groups and aluminosilicate surface sites, which enhanced structural cohesion, thermal stability, and resistance to repeated regeneration. The integration of design-of-experiments with the synthesis of floating, regenerable alginate–aluminosilicate composites provides a sustainable and operationally advantageous strategy for Hg(II) removal from mining-impacted waters. The high buoyancy, reusability, and ease of recovery without energy-intensive separation steps position FAB 1.0 in particular as a competitive candidate for scalable and environmentally responsible water treatment applications.
Son-Tafur et al. (2026) studied this question.