Divalent and trivalent ion exchange with zeolite A

Abstract

~~The ion-exchange isotherm for Ca2+ exchange with sodium zeolite A was determined at 25 OC by using a novel solid uptake analytical scheme and a Langmuir adsorption model, resulting in an improved value for the thermodynamic equilibrium constant. Ion-exchange isotherms and approximate thermodynamic equilibrium constants were also determined for calcium zeolite A exchange with Pb2+, Cd2+, and Cu2+. Pb2+ and Cd2+ exchanges were found to be reversible, whereas Cu2+ exchange was not, probably due to Cu(OH),(s) precipitation upon or within the zeolite.Ion exchange was attempted but found to be irreversible with C$+, Hg2+, Fe3+, and A13+. Except for Cr3+, these ions caused zeolite A structure degradation, probably through extensive proton exchange. Cr3+ exchanged partially and then formed a precipitate. Data obtained in this work provide an improved understanding of the possible environmental water effects of zeolite A.

Ion Exchange of Zeolite Na-Pc with Pb2+, Zn2+, and Ni2+ Ions

“…The selectivity for Pb is sufficient large to consider that the material can remove Pb efficiently from aqueous solutions containing Pb salts, especially at low concentrations. The observed increased selectivity for Pb vs. Na is common and is reported in many synthetic and natural zeolites including zeolites X and Y, zeolite A, clinoptilolite, and mordenite (Wiers et al, 1982;Blanchard et al, 1984). The reverse exchange reaction is considerably slower and displays a limited but noticeable hysteresis (Figure 4).…”

“…The ion-exchange properties of many common synthetic zeolites such as NaX, NaY, and NaA were thoroughly examined in the past, mainly because of their wide utilization in detergents and ammonium exchangers (Sherry and Walton, 1967;Barrer et al, 1968aBarrer et al, , 1968bGal et al, 1971;Maes and Cremers, 1975;Townsend, 1981, 1982;Wiers et al, 1982;and many others). The use of zeolites in wastewater purification offers the advantage of a highly improved cation-exchange performance relative to natural counterparts.…”

Synthetic zeolites and other microporous oxide molecular sieves

“…Zeolite NaA was known to have high selectivity and capacity for calcium, and its application as a builder in heavy-duty powder detergents was developed in the 1970s, primarily by scientists at Henkel (59, 60, ‡ ‡ ) in Germany and Procter and Gamble (61,62) in the U.S. Round NaA zeolite particles, a few micrometers across, are small enough to pass through the openings in the weave of the fibers in clothing and are not filtered out to form encrustations on the cloth.…”

Sodium, Calcium, and Ammonium Exchange on Clinoptilolite from the Fort Laclede Deposit, Sweetwater County, Wyoming

“…This illustration shows that there is no marked hysteresis in the exchange under the test conditions, that the zeolite preferentially takes up Ca-'-over Naat low to moderate loadings of Ca:-, and that the preference for Ca 2 § is somewhat greater at the higher temperature. To put these observations into a quantitative form, the equilibrium constants were determined using the Kielland plots, such as that shown in Figure 6, and following the procedure outlined by Wiers et al (1982). The thermodynamic equilibrium constants for the replacement of two Na ~ by one Ca ~-on the Fort LaClede clinoptilolite are 6 at 63~ and 2 at 30~ As noted above, shapes of the Kielland plot curves are unknown; therefore, to perform the required integration, simple curves were chosen to represent the experimental data.…”