Multicomponent ion exchange on synthetic zeolites

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Tezin Türü: Doktora

Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Fen Bilimleri Enstitüsü, Fen Bilimleri Enstitüsü, Türkiye

Tezin Onay Tarihi: 2014

Öğrenci: ELİF BEŞEL DÜZGÜN

Danışman: HAYRETTİN YÜCEL

Özet:

Zeolites are natural and synthetic microporous crystalline aluminosilicates with ion-exchange and molecular sieve properties. Zeolites consist of a three-dimensional framework of (SiO4)4- and (AlO4)5- tetrahedras, connected by a shared oxygen atom. The presence of aluminum in the aluminosilicate framework introduces a net negative charge. Zeolites are mostly used in ion exchange, adsorption processes and catalytic applications. The objective of the study was to determine and model the multicomponent ion exchange behavior of Zeolite 13X for lead, cadmium and zinc ions. For this purpose, Pb2+- Na+ , Cd2+-Na+ and Zn2+ - Na binary systems, Cd2+- Pb2+ - Na+ ternary systems and Cd2+- Pb2+ - Zn2+ - Na+ quaternary systems were investigated in batch and column operations. Breakthrough capacities and column efficiencies were determined at different concentrations, mesh ranges and flow rates. Optimum total concentration were determined as 0.05 N, optimum flow rate as 10 mL/min, optimum particle size range as 0.6-0.7 mm (25/30 mesh ranges). Ion exchange of Pb2+, Cd2+ and Zn2+on to NaX zeolite was modelled using the Langmuir, Freundlich, Tempkin, DR, Redlich Peterson, Sips and BET isotherms. Among all the isotherms tested, Redlich Peterson isotherm gave the best fit for all metals with the highest R2 and lowest ARE values. The Modified Langmuir Model, Jain and Snoeyink Model, SRS Model, Extended SIPS Model and IAST Model were used to fit the multicomponent ion exchange data; but only SRS Isotherm Model was observed to fit the experimental data with high linear coefficient of determination. Pseudo-second order kinetic equation describe the batch system kinetics well. W&M model indicated that the intra-particle diffusion is not the only rate controlling step, Finally possible mass transfer controlling mechanism in the column experiments was determined as solid diffusion. Solid-phase diffusion coefficients were evaluted as 4.3x10-6 cm2/min for Pb2+- NaX exchange; 4.6x10-6 cm2/min for Cd2+- NaX exchange and 2.2x10-6 cm2/min for Zn2+- NaX exchange