Creating nanoporosity in Na, Ca and Mg exchanged erionite zeolite (original) (raw)
Related papers
Changes in Porous Parameters of the Ion Exchanged X Zeolite and Their Effect on CO2 Adsorption
Molecules, 2021
Zeolite 13X (NaX) was modified through ion-exchange with alkali and alkaline earth metal cations. The degree of ion exchange was thoroughly characterized with ICP, EDS and XRF methods. The new method of EDS data evaluation for zeolites was presented. It delivers the same reliable results as more complicated, expensive, time consuming and hazardous ICP approach. The highest adsorption capacities at 273 K and 0.95 bar were achieved for materials containing the alkali metals in the following order K < Na < Li, respectively, 4.54, 5.55 and 5.94 mmol/g. It was found that it is associated with the porous parameters of the ion-exchanged samples. The Li0.61Na0.39X form of zeolite exhibited the highest specific surface area of 624 m2/g and micropore volume of 0.35 cm3/g compared to sodium form 569 m2/g and 0.30 cm3/g, respectively. The increase of CO2 uptake is not related with deterioration of CO2 selectivity. At room temperature, the CO2 vs. N2 selectivity remains at a very high stab...
Ion exchange kinetics and thermodynamics of hydrosodalite, a narrow pore zeolite
Journal of Porous Materials, 2014
The ion-exchange properties of a synthetic hydrosodalite (Na-hS) have been investigated by kinetic and thermodynamic analysis of exchange reactions of the original sodium form for lithium, potassium and calcium forms. Kinetic curves, modelled by a Langmuir-type equation, revealed that exchange rate for lithium and for potassium are of the same order, whereas they are two order faster than for calcium. Thermodynamic analysis of the cation exchange isotherms pointed out that sodalite is selective for sodium over the other three cationic forms examined, which is consistent with the preference exhibited by the sodalite type for sodium environments, either in natural or in laboratory crystallization. Na/Li and Na/Ca exchanges are incomplete, whereas unexpectedly Na/K exchange turns out to be complete, even though K + dimension exceeds the width of the access window to sodalite cages. The obtained results have been discussed in terms of Eisenman-Sherry theory, pointing out agreements and discrepancies.
Critical Admission Temperature of H2 and CH4 in Nanopores of Exchanged ERI Zeolites
Nanomaterials, 2019
Due to the nanoporous nature of zeolitic materials, they can be used as gas adsorbents. This paper describes the effect of critical admission temperature through narrow pores of natural ERI zeolites at low levels of coverage. This phenomenon occurs by adsorption of CH4 and H2 on pores in natural erionite. The zeolite was exchanged with aqueous solutions of Na+, Mg2+, and Ca2+ salts at different concentrations, times, and temperatures of treatment. Experimental data of CH4 and H2 adsorption were treated by the Langmuir equation. Complementarily, the degree of interaction of these gases with these zeolites was evaluated by the evolution of isosteric heats of adsorption. The Ca2+ and Mg2+ cations favor the adsorption phenomena of H2 and CH4. These cations occupy sites in strategic positions Ca1, Ca2, and Ca3, which are located in the nanocavities of erionite zeolites and K2 in the center of 8MR. Following the conditions of temperature and the exchange treatment, ERICa2 and ERINa3 sampl...
ION EXCHANGE OF ZEOLITE Na-Pc WITH Pb 2+, Zn 2+, AND Ni 2+ IONS
This paper examines the ion-exchange properties of synthetic zeolite Na-P0, which was produced from perlite-waste fines and has a SiO2:A1203 ratio of 4.45:1 and a cation-exchange capacity (CEC) of 3.95 meq g ~. Although equilibrium is attained rapidly for all three metals, exchange is incomplete, with At(max) (maximum equilibrium fraction of the metal in the zeolite) being 0.95 for Pb, 0.76 for Zn, and 0.27 for Ni. In both Na ~ 89 and Na --* 89 exchange, the normalized selectivity coefficient is virtually constant for :~A~ (normalized equilibrium fraction of the metal in the zeolite) values of --<0.6, suggesting a pronounced homogeneity of the available exchange sites. The Gibbs standard free energy, AG ~ of the Na ---) 89 exchange calculated from the normalized selectivity coefficient is -3.11 kJ eq and, for the Na ~ 1/2Zn exchange, it is 2.75 kJ eq ~.
RSC Adv., 2015
Development of zeolite based adsorbents with high adsorption capacity and selectivity is the key requirement for efficient and economic separation processes. However, less attention has been given so far towards understanding the mechanism of adsorption on the zeolites. In the present study adsorption of carbon monoxide, methane and nitrogen on zeolite-X exchanged with magnesium, calcium, strontium and barium cations was carried out using a volumetric gas adsorption method. Calcium, strontium, and barium ion exchanged zeolite-X shows increase in carbon monoxide, methane and nitrogen adsorption capacity. Strontium exchanged zeolite-X shows carbon monoxide adsorption capacity of 28.4 molecules per unit cell and calcium exchanged zeolite-X shows methane and nitrogen adsorption capacity of 18.8 and 13.8 molecules per unit cell, respectively at 303 K and 760 mm Hg pressure, maximum among the alkaline earth metal ion exchanged zeolite-X samples. However, barium exchanged zeolite-X shows methane/nitrogen selectivity of 1.78, maximum among the studied samples.
BINARY ION EXCHANGE ISOTHERMS IN NaY ZEOLITE
The ion exchange of Na for Cr/K, Cr/Mg and Cr/Ca in Y and X zeolites was studied using breakthrough curves. It was observed that Cr 3+ ions were able to remove some competitive ions that had already been exchanged at the zeolitic sites, producing a sequential ion exchange. Some mass transfer parameters such as length of unused bed, overall mass transfer coefficient, operational ratio and dimensionless variance were studied. Chromium uptake was influenced much more by the competing ion in the NaX zeolite columns. The dimensionless variance indicated that Cr/K solution produced a greater axial dispersion than the Cr/Mg and Cr/Ca systems, probably due to some interaction between Cr 3+ and K + ions. The order of dynamic selectivity, provided by the cation uptake, was Cr 3+ > Ca 2+ , Cr 3+ > Mg 2+ and Cr 3+ > K + for NaY zeolite and Ca 2+ ≈ Cr 3+ , Mg 2+ > Cr 3+ and Cr 3+ > K + for NaX zeolite. Due to the more favorable mass transfer parameters and higher affinity for Cr 3+ , it was concluded that NaY zeolite was more efficient at chromium uptake in competitive systems.
Binary ion exchange of metal ions in Y and X zeolites
Brazilian Journal of Chemical Engineering, 2003
The ion exchange of Na for Cr/K, Cr/Mg and Cr/Ca in Y and X zeolites was studied using breakthrough curves. It was observed that Cr3+ ions were able to remove some competitive ions that had already been exchanged at the zeolitic sites, producing a sequential ion exchange. Some mass transfer parameters such as length of unused bed, overall mass transfer coefficient, operational ratio and dimensionless variance were studied. Chromium uptake was influenced much more by the competing ion in the NaX zeolite columns. The dimensionless variance indicated that Cr/K solution produced a greater axial dispersion than the Cr/Mg and Cr/Ca systems, probably due to some interaction between Cr3+ and K+ ions. The order of dynamic selectivity, provided by the cation uptake, was Cr3+ > Ca2+, Cr3+ > Mg2+ and Cr3+ > K+ for NaY zeolite and Ca2+ » Cr3+, Mg2+ > Cr3+ and Cr3+ > K+ for NaX zeolite. Due to the more favorable mass transfer parameters and higher affinity for Cr3+, it was concluded that NaY zeolite was more efficient at chromium uptake in competitive systems.
Kinetics of ion exchange in quasi-crystalline aluminosilicate zeolite precursors
Microporous and Mesoporous Materials, 2005
The kinetics of binary ion exchange of Ca 2+ and Mg 2+ for Na + in quasi-crystalline and crystalline zeolite A has been investigated. Diffusion of either divalent cation into crystalline zeolite NaA is relatively fast, while the exchanges are slower in the quasi-crystalline precursor materials. The diffusion coefficient for Mg 2+ exchange (D (Mg) ) into crystalline zeolite A is an order of magnitude lower than that of Ca 2+ (D (Ca) ), due to the larger hydration sphere of the Mg 2+ ion. However, the ratio (D (Ca) :D (Mg) ) was found to scale with the degree of crystallinity of the sample. Calcium and magnesium ions diffuse into the quasi-crystalline materials at comparable rates; this phenomenon is ascribed to the presence of larger pores in the quasi-crystalline structure, as compared to the crystalline material. Low impact mechanical treatment of quasi-crystalline zeolite precursors further decreases the difference between D (Ca) and D (Mg) , while the crystallinity of the material is not noticeably decreased.