Metal Ion Adsorption by Chitosan and Alginate Gel Nanoparticles and Microparticles

Chitosan and alginate are both low-cost natural materials used for the removal of metal ions from aqueous solutions. In this research, three different concentrations of chitosan gel nanoparticles were synthesized by ionic cross-linking with sodium tripolyphosphate and characterized by zeta-sizing and TEM.  The adsorption capability of Cu²⁺ from copper sulfate solution onto chitosan nanoparticles, calcium-alginate gel microbeads and alginate-chitosan combination particles at fixed pH has been explored.

Results show that the equilibrium adsorption properties of chitosan nanoparticles have similar trends to those of alginate microbeads, and the adsorption capacity varies with the synthesis concentration of chitosan nanoparticles. In addition, the adsorption for both chitosan nanoparticles and alginate microbeads behaves differently in low concentration copper sulfate solution and high concentration solution. The Langmuir isotherm fits the low concentration region well and correlation coefficients were determined. In contrast, approximately linearly increasing adsorption was observed at higher solution concentrations. Alginate-chitosan combination particles were found to have intermediate maximum adsorption capacity and similar Langmuir adsorption equilibrium constant with alginate microbeads in low concentration copper sulfate solution. The adsorption capabilities of combination particles could be predicted by the weight ratio of calcium-alginate gel microbeads and chitosan gel nanoparticles.