Yu, Kun. Copper ion adsorption by chitosan gel nanoparticles and calcium-alginate gel beads for water purification applications. Retrieved from https://doi.org/doi:10.7282/T3610XF9
DescriptionWater purification is emerging as a critical need as resources become increasingly limited. Chitosan and alginate are both low-cost natural carbohydrate materials used for the removal of heavy metal ions from aqueous solutions. The objective of this research is to enhance understanding of the process and mechanisms of copper ion adsorption by these biopolymer gel particles at multiple size scales, with the aim of guiding the next generation of biosorbent design for water purification applications. First, the equilibrium adsorption capability of copper ions from copper sulfate solution onto chitosan gel nanoparticles, calcium-alginate gel microbeads, chitosan/alginate combination particles and large alginate gel beads at fixed pH was studied. Results show that the adsorption behavior of chitosan and alginate in the low concentration region follows the Langmuir isotherm. 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. Also, adsorption kinetics of copper ions onto calcium-alginate gel microbeads, chitosan/alginate combination particles and large alginate gel beads were investigated. It was observed that the adsorption kinetics of large alginate gel beads was much faster than that of alginate microbeads and combination particles. The adsorption of copper ions on to combination particles was slightly faster than on to plain alginate microbeads. A pseudo-second order kinetic model successfully predicted the adsorption behavior over the whole range of studies, indicating that chemisorption is the rate controlling step and the chemisorption reaction is second order. Moreover, the adsorption behavior of fixed-bed columns packed with large alginate gel beads was studied by varying the column size and volumetric flow rate. The column had shorter active life at a higher flow rate, or at a smaller size. The Thomas model, Adams-Bohart model and Yoon-Nelson model successfully fit experimental data, allowing prediction of the breakthrough time.