title: Equilibrium and kinetic ion exchange studies of Pb2+, Cr3+, Fe3+ and Cu2+ on natural clinoptilolite.
abstract: In the present study ion exchange of Pb2+, Cu2+, Fe3+ and Cr3+ on natural clinoptilolite is examined at 27 +/- 1 degree C and initial concentration of 10 meq/dm3. Equilibrium is favorable for Pb2+, unfavorable for Cu2+ and sigmoid for Cr3+ and Fe3+. Selectivity series deduced from equilibrium isotherms is Pb2+ > Cr3+ > Fe3+ > Cu2+, while when maximum exchange levels (MELs) are considered, selectivity series is Pb2+ > Cr3+ approximately = Cu2+ > or = Fe3+. Cu2+ manifests the higher value of diffusion coefficient in the clinoptilolite particles among the metals studied, equal to 1.40 x 10(-9) cm2/s. According to the fixed bed experiments the upflow rate (5-15 Bed Volumes (BV)) is influencing the breakthrough point for all metals studied. The breakthrough point varies between 12.3 BV for Pb2+ and 1.18 for Cu2+. Flow rate is also influencing the operating capacity, giving values between 0.433 meq/g(clinoptilolite) for Pb2+ and 0.053 for Fe3+. Breakthrough point values confirm the selectivity order deduced from the equilibrium isotherms, while operating capacity values confirm the selectivity order deduced from MEL experiments.
authors.affiliation: Department of Chemical Engineering, National Technical University of Athens, Greece.
authors.forename: V J
authors.initials: VJ
authors.lastname: Inglezakis
authors.forename: M D
authors.initials: MD
authors.lastname: Loizidou
authors.forename: H P
authors.initials: HP
authors.lastname: Grigoropoulou
mesh_terms: D007474:Ion Exchange; D007700:Kinetics; D019216:Metals, Heavy / Q000737:chemistry*; D013696:Temperature; D014873:Water Pollutants / Q000032:analysis*; D017641:Zeolites / Q000737:chemistry*
chemical_list: D019216:Metals, Heavy; D014873:Water Pollutants; C083175:clinoptilolite; D017641:Zeolites