Cellulose nanofiber/sodium alginate/chitosan aerogel spheres for adsorbing cationic dyes

To develop sustainable materials for textile dye wastewater purification, this study utilized renewable biopolymers to fabricate cellulose nanofiber/sodium alginate (CNF/SA) hydrogel spheres via metal-ion crosslinking. Subsequently, chitosan was dissolved in an environmentally friendly citric acid solution and integrated into the CNF/SA matrix through crosslinking, followed by freeze-drying to obtain cellulose nanofiber/sodium alginate/chitosan (CNF/SA/CTS) aerogel spheres. Comparative characterization and adsorption performance studies revealed that the introduction of chitosan into the CNF/SA system formed a ternary composite material (CNF/SA/CTS) with a denser and more stable three-dimensional network structure, enriched with abundant functional groups, such as amino groups. This material maintained good structural stability and adsorption performance across a wide pH range and after multiple adsorption-desorption cycles. Notably, CNF/SA/CTS exhibited a strong adsorption capacity for various dyes, including methylene blue, crystal violet, methyl orange, and malachite green. The maximum adsorption capacity for cationic dyes reached as high as 1371.1 ± 54.8 mg/g, outperforming the corresponding CNF/SA binary material. The adsorption process followed pseudo-second-order kinetics and the Langmuir isotherm model, and was determined to be spontaneous and endothermic. This study confirms the significant potential of CNF/SA/CTS aerogel spheres as an ideal green adsorbent, highlighting the promising sustainable application prospects of biomass-based composite materials in wastewater treatment.