Alum Sludge as a Potential Adsorbent for Removing Cd(ii) and Ni(ii) Ions From Aqueous Solutions – Equilibrium Studies

The present research evaluates the possibility of using alum sludge from water treatment stations(WTS) as an effective adsorbent for Ni(II) and Cd(II). The physicochemical properties weredetermined of four alum sludge, from WTS Czaniec (AS-C), WTS Kozłowa Góra (AS-K), WTSMaczki (AS-M), and WTS Będzin (AS-B). The adsorption of ions was investigated by batchexperiments at room temperature, a wide range of initial concentrations (1-1000 mg/L), and anadsorbent dose of 10 g/L. The experimental data were analysed by Freundlich, Langmuir andDubinin-Radushkevich isotherms, using linear and nonlinear regression analysis. All alum sludgeused in the study was found to have better binding capacities for Ni(II) ions than for Cd(II) ions.At the maximum initial concentration Ni(II) ions were bound in the following order: AS-K =>AS-B => AS-M => AS-C, while Cd(II) ions were bound in the following order: AS-B => AS-M=> AS-K => AS-C. The results indicated that the adsorption mechanism primarily involves ionexchange and also electrostatic interactions. It can be concluded that alum sludge is a promisingadsorption material for the removal of metal ions from aqueous solutions.