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Title: Multicomponent liquid ion exchange with chabazite zeolites

Abstract

In spite of the increasing commercial use of zeolites for binary and multicomponent sorption, the understanding of the basic mass-transfer processes associated with multicomponent zeolite ion-exchange systems is quite limited. This study was undertaken to evaluate Na-Ca-Mg-Cs-Sr ion exchange from an aqueous solution using a chabazite zeolite. Mass-transfer coefficients and equilibrium equations were determined from experimental batch-reactor data for single and multicomponent systems. The Langmuir isotherm was used to represent the equilibrium relationship for binary systems, and a modified Dubinin-Polyani model was used for the multicomponent systems. The experimental data indicate that diffusion through the microporous zeolite crystals is the primary diffusional resistance. Macropore diffusion also significantly contributes to the mass-transfer resistance. Various mass-transfer models were compared to the experimental data to determine mass-transfer coefficients. Effective diffusivities were obtained which accurately predicted experimental data using a variety of models. Only the model which accounts for micropore and macropore diffusion occurring in series accurately predicted multicomponent data using single-component diffusivities. Liquid and surface diffusion both contribute to macropore diffusion. Surface and micropore diffusivities were determined to be concentration dependent.

Authors:
; ;
Publication Date:
Research Org.:
Oak Ridge National Lab., TN (United States)
Sponsoring Org.:
USDOE, Washington, DC (United States)
OSTI Identifier:
10191341
Report Number(s):
ORNL/TM-12403
ON: DE94001780; TRN: 93:024149
DOE Contract Number:
AC05-84OR21400
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: Oct 1993
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ION EXCHANGE; MASS TRANSFER; DIFFUSION; ZEOLITES; SODIUM; CALCIUM; MAGNESIUM; CESIUM; STRONTIUM; MICROSTRUCTURE; POROSITY; 400105; SEPARATION PROCEDURES

Citation Formats

Robinson, S.M., Arnold, W.D. Jr., and Byers, C.W. Multicomponent liquid ion exchange with chabazite zeolites. United States: N. p., 1993. Web. doi:10.2172/10191341.
Robinson, S.M., Arnold, W.D. Jr., & Byers, C.W. Multicomponent liquid ion exchange with chabazite zeolites. United States. doi:10.2172/10191341.
Robinson, S.M., Arnold, W.D. Jr., and Byers, C.W. Fri . "Multicomponent liquid ion exchange with chabazite zeolites". United States. doi:10.2172/10191341. https://www.osti.gov/servlets/purl/10191341.
@article{osti_10191341,
title = {Multicomponent liquid ion exchange with chabazite zeolites},
author = {Robinson, S.M. and Arnold, W.D. Jr. and Byers, C.W.},
abstractNote = {In spite of the increasing commercial use of zeolites for binary and multicomponent sorption, the understanding of the basic mass-transfer processes associated with multicomponent zeolite ion-exchange systems is quite limited. This study was undertaken to evaluate Na-Ca-Mg-Cs-Sr ion exchange from an aqueous solution using a chabazite zeolite. Mass-transfer coefficients and equilibrium equations were determined from experimental batch-reactor data for single and multicomponent systems. The Langmuir isotherm was used to represent the equilibrium relationship for binary systems, and a modified Dubinin-Polyani model was used for the multicomponent systems. The experimental data indicate that diffusion through the microporous zeolite crystals is the primary diffusional resistance. Macropore diffusion also significantly contributes to the mass-transfer resistance. Various mass-transfer models were compared to the experimental data to determine mass-transfer coefficients. Effective diffusivities were obtained which accurately predicted experimental data using a variety of models. Only the model which accounts for micropore and macropore diffusion occurring in series accurately predicted multicomponent data using single-component diffusivities. Liquid and surface diffusion both contribute to macropore diffusion. Surface and micropore diffusivities were determined to be concentration dependent.},
doi = {10.2172/10191341},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Fri Oct 01 00:00:00 EDT 1993},
month = {Fri Oct 01 00:00:00 EDT 1993}
}

Technical Report:

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  • Planned near-term and long-term upgrades of the Oak Ridge National Laboratory (ORNL) Process Waste Treatment Plant (PWTP) will use chabazite columns to remove {sup 90}Sr and {sup 137}Cs from process wastewater. A valid equilibrium model is required for the design of these columns and for evaluating their performance when influent wastewater composition changes. The cations exchanged, in addition to strontium and cesium, are calcium, magnesium, and sodium. A model was developed using the Wilson equation for the calculation of the solid-phase activity coefficients. The model was tested against chabazite column runs on two different wastewaters and found to be valid.more » A sensitivity analysis was carried out for the projected wastewater compositions, in which the model was used to predict changes in relative separation factors for strontium and cesium subject to changes in calcium, magnesium, and sodium concentrations.« less
  • Improved precipitation and ion-exchange methods are being developed to decontaminate Oak Ridge National Laboratory (ORNL) process wastewaters containing small amounts of {sup 90}Sr and {sup 137}Cs while minimizing waste generation. A wide range of potential processes have been tested in laboratory-scale scouting tests. Based on the data from these scouting tests, several alternative flowsheets have been developed for long-term upgrade of the facility. The primary objective of these proposed flowsheets is to minimize secondary waste generation, particularly liquid wastes, and produce a nonhazardous waste form that can be safely stored with minimum surveillance. The most promising process consists of passingmore » wastewater through a series of columns containing chabazite zeolite, an inorganic ion-exchange material, to remove both cesium and strontium. The flowsheet has the advantage of being a simple, reliable process that produces one type of solid waste. The feasibility of this process has been demonstrated using pilot-scale equipment at the Process Waste Treatment Plant (PWTP). A single near-full-scale column has also been tested at the PWTP for cesium removal. This report summarizes the results of both chabazite tests performed at the PWTP in 1987. 16 refs., 12 figs., 3 tabs.« less
  • The objective of this program is to screen catalysts and determine operating conditions for maximizing gas and char production from the pyrolysis of coal gasification tars. The product yields from cracking a bituminous coal tar in a fixed-bed reactor were determined at various temperatures in the presence and absence of some packing materials. Synthetic zeolites, Linde LZ-Y82, Norton Zeolon 900-H (mordenite), Davison 13-X, and ultra-stable faujasite (H-Y), as well as a natural zeolite, chabazite, showed strong catalytic activity. In contrast, molecular sieves 5-A and natural erionite having smaller pore diameters were found to be much less active. Clay minerals suchmore » as kaolinite, montmorillonite and Kieselguhr exhibited catalytic activities which were similar to those of the zeolites with small pore sizes, but they were still far more effective than quartz particles. Based on the assumption of first-order kinetics, the activation energies for the tar conversion were evaluated for several packing materials. It was found that the zeolite LZ-Y82 was remarkably effective in converting tar to chars and gases in the temperature range of 350 to 500/sup 0/C, although this effectiveness decreased very rapidly with a continuous tar feed carried by an inert gas. Among the factors involved for catalytic effectiveness are (1) the effective pore size greater than about 0.7 nm (or 7A), (2) large internal surface area accessible to the tar vapor, and (3) large number of strongly acidic sites. 22 references, 6 figures, 22 tables.« less
  • Nitrogen adsorption isotherms were measured for four samples of chabazite, which were collected from different geographical locations, and for a Linde 5A synthetic zeolite. All isotherms were Type I and obeyed the Langmuir adsorption model. Surface areas and pore diameters were calculated from the adsorption data. The MP method was used to determine the pore volume distribution for each sample. The results indicated that all of the chabazite samples had nearly identical properties, and these properties were also very similar to those of the Linde 5A synthetic zeolite.