Sodium alginate and chitosan are added to a CaCl2 solution to prepare calcium-alginate.chitosan and calciumalginate gels. After dehydration through stoving, two types of adsorbent particles are obtained. The adsorption process of the particles obtained for low concentrations of Sr2+ satisfies a second-order kinetic equation and the Freundlich adsorption model. The thermodynamic behaviors of the particles indicate that adsorption occurs via a spontaneous physical process. XPS pattern analysis is used to demonstrate the adsorption of Sr2+ by calcium alginate and chitosan. By building an interaction model of the molecules of chitosan and alginate with Ca2+ and Sr2+ to calculate energy parameters, Fukui index, Mulliken charge, and Mulliken population, adsorption of Sr2+ on the molecular chains of chitosan as well as the boundary of calcium-alginate.chitosan is observed to show weak stability; by contrast, adsorption between molecular chains is high.

Keywords: Ca-alginate-chitosan; adsorption; Sr2+; kinetics; thermodynamics.