title: Adsorption of heavy metal cations by Na-clinoptilolite: equilibrium and selectivity studies.
abstract: This paper summarizes the conclusions of experiments conducted on the adsorption of Cd(2+), Co(2+), Cu(2+), Mn(2+), Ni(2+), Pb(2+) and Zn(2+) onto zeolite. The focus of the experiments was to establish the influence of the initial pH of the contact solution as well as the selectivity of zeolite on the efficiency of the adsorption process. To this end, experimental adsorption isotherms were established for the pH values ranging from 1 to 4 by using the Na-form of clinoptilolite (particle size range 0.5-1 mm) as an adsorbent. Langmuir, Freundlich and Dubinin-Raduschkevich isotherm models were used to validate the experimental data and the Gibbs free energy was calculated based on the distribution coefficient. From the Langmuir model, correlations between the maximum adsorption capacity and selected physical-chemical parameters of the cations studied were established. The results of the experiments suggest that the selectivity of zeolite is strongly influenced by the pH of the contact solution, dehydration energy of cations, diffusion coefficient and the pH at which the precipitation of hydroxides occurs.
authors.affiliation: Technical University of Cluj Napoca - Romania, Scientific Research Center for Environment, Food and Health Safety, North University Center of Baia Mare, Victoriei Street 76, Baia Mare 430122, Romania. Electronic address: mihalyl@yahoo.com.
authors.forename: L
authors.initials: L
authors.lastname: Mihaly-Cozmuta
authors.affiliation: Technical University of Cluj Napoca - Romania, Scientific Research Center for Environment, Food and Health Safety, North University Center of Baia Mare, Victoriei Street 76, Baia Mare 430122, Romania.
authors.forename: A
authors.initials: A
authors.lastname: Mihaly-Cozmuta
authors.affiliation: Technical University of Cluj Napoca - Romania, Scientific Research Center for Environment, Food and Health Safety, North University Center of Baia Mare, Victoriei Street 76, Baia Mare 430122, Romania.
authors.forename: A
authors.initials: A
authors.lastname: Peter
authors.affiliation: Technical University of Cluj Napoca - Romania, Scientific Research Center for Environment, Food and Health Safety, North University Center of Baia Mare, Victoriei Street 76, Baia Mare 430122, Romania.
authors.forename: C
authors.initials: C
authors.lastname: Nicula
authors.affiliation: Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, Johannesburg, South Africa.
authors.forename: H
authors.initials: H
authors.lastname: Tutu
authors.affiliation: National Institute for Research and Development of Isotopic and Molecular Technologies, Cluj-Napoca, Romania.
authors.forename: Dan
authors.initials: D
authors.lastname: Silipas
authors.affiliation: National Institute for Research and Development of Isotopic and Molecular Technologies, Cluj-Napoca, Romania.
authors.forename: Emil
authors.initials: E
authors.lastname: Indrea
mesh_terms: D000327:Adsorption; D006863:Hydrogen-Ion Concentration; D019216:Metals, Heavy / Q000737:chemistry*; D008962:Models, Theoretical; D012996:Solutions; D014874:Water Pollutants, Chemical / Q000737:chemistry*; D017641:Zeolites / Q000737:chemistry*
chemical_list: D019216:Metals, Heavy; D012996:Solutions; D014874:Water Pollutants, Chemical; C083175:clinoptilolite; D017641:Zeolites
keywords: Adsorption isotherms; Dehydration energy; Diffusion coefficient; Hydrocomplex; Zeolite stability