Adsorption of Heavy Metal Ions onto Surface-Functionalised Polymer Beads. I. Modelling of Equilibrium Isotherms by Using Non-Linear and Linear Regression Analysis

Styrene-divinylbenzene copolymer beads with ionic liquid-like functionalities (ILLF) covalently immobilised on the surface were synthesised and used to remove Cd(II) and Pb(II) from aqueous solutions. The dependence of adsorption behaviour on initial pH and metal ion concentration of solution was established. Higher ILLF content causes improved adsorption performance as ILLF are involved in coordination with metal ions. Experimental data were analysed by several isotherm models using non-linear and linear regressions, the goodness of fit being assessed by various error functions. Langmuir and Temkin models successfully describe Cd(II) and Pb(II) adsorption, respectively, whereas Freundlich model provides the poorest fit for adsorption of the two metal ion species. For a particular isotherm model, the best fit is offered by its non-linear or linear forms or by both of them. The adsorption of Cd(II) and Pb(II) is favourable and spontaneous. The synthesised adsorbents have potential applications in wastewater treatment.