Effect of nickel on the adsorption of silver ions over activated carbon

Purpose The disposal of wastewater containing silver is an environmental concern. Due to the toxicity of silver, treatment of such wastewater is necessary. Real wastewater contains a complex matrix of pollutants. The purpose of this paper is to study the adsorption behavior of silver in single and binary systems (with nickel) onto granular activated carbon. Design/methodology/approach The effect of silver ions concentration and the mass of adsorbent on the adsorption behavior were analyzed. Five two-parameter isotherms (Langmuir, Elovich, Freundlich, Dubinin-Radushkevich and Temkin) were applied to investigate the adsorption mechanism. Both linear and nonlinear regressions were tested for the first three isotherms. The experimental data were also fitted to Redlich-Petersons, Sips and Toth models. Findings A direct relationship between the initial silver ion concentration and its adsorption capacity was observed, whereas an inverse relationship between the adsorbent mass and the adsorption capacity was documented. The Langmuir model was found to best-fit the data indicating monolayer adsorption behavior. The maximum uptake was 2,500 mg/g in the single adsorption system. This value decreased to 909 mg/g in the binary system. The adsorption was found to have an exothermic chemical nature. Originality/value The study of the silver adsorption in a single system is inaccurate. Real wastewater contains a complex matrix of pollutants. This research gives a clear insight into the adsorption behavior in binary systems.