Removal of Cs1+, Sr2+ and Co2+ from aqueous solutions by adsorption on natural clinoptilolite

The adsorption properties of local clinoptilolite (Serbia) towards Cs+, Co2+, and Sr2+ were investigated by batch equilibration technique. The influence of equilibration time, initial metal cation concentration, solution PH and presence of EDTA on these properties was studied and discussed. Kinetic data were found to be well fitted with pseudo-second order kinetic model. Cs+ is preferably adsorbed by the natural clinoptilolite, followed by Sr2+ and CO2+. The Langmuir adsorption isotherm was used to determine the adsorption capacities from both single and mixed metal solutions. At PH range of 3-12 the adsorption of Cs+ remains almost constant, while at low PH (2-3) the adsorption is lesser. At initial PH range of 2-10 adsorption of Sr2+ remains approximately stable, whereas at initial PH > 10 adsorption increases significantly. The adsorption of Co2+ is low at low PH but increased remarkably with increasing PH and precipitated at pH > 8. Cs+ adsorption on the clinoptitolite was not affected by the presence of EDTA, while the presence of EDTA hinders the adsorption of Co2+ and Sr-2+ on clinoptilolite. (c) 2006 Elsevier B.V. All rights reserved.