Abstract
[Display omitted]
► Alginate demonstrated superior adsorption capacity for Cu2+ vs. chitosan. ► Langmuir isotherm fits low concentration adsorption data (0.5–50mM). ► Freundlich isotherm fits high concentration adsorption data (50mM–1M). ► Cu2+ tended to adsorb on one alginate subunit and two chitosan subunits. ► Chitosan–alginate combination particles possess mass-averaged adsorption capacity.
Chitosan and alginate are natural carbohydrate materials used to remove heavy metal ions from aqueous solutions. In this research, chitosan gel nanoparticles were formed by ionic cross-linking with sodium tripolyphosphate and characterized by zetasizing and TEM. The equilibrium adsorption capability of chitosan nanoparticles and calcium-alginate gel microbeads for Cu2+ from copper sulfate solutions at fixed pH has been explored. Results show that the adsorption behavior of chitosan and alginate in the low concentration region follows the Langmuir isotherm. Approximately linearly increasing adsorption behavior was observed at higher solution concentrations. Chitosan gel nanoparticles exhibit a minor increase in adsorption capacity compared to other forms of chitosan. Alginate has significantly higher capacity than chitosan, which can be attributed to a comparatively higher density of adsorption sites. Combination particles consisting of alginate microbeads coated with chitosan nanoparticles possess an intermediate maximum adsorption capacity, corresponding to the weight ratio of the alginate and chitosan.