Ion-exchange equilibria of synthetic 4A zeolite with Ni²⁺, Co²⁺, Cd²⁺and Zn²⁺ions

Abstract

Linde 4A zeolite was converted to Ni, Co, Zn and Cd forms by replacing sodium ions with divalent cations. The replacement was from 82 % (Ni) up to 100 % (Cd). Chemical, T.G.A., D.T.A. and X-ray analysis of the divalent metal zeolites have been made and data on the composition of the unit cells and the thermal stability of the lattices were obtained. Ni-zeolite is unstable, its crystal lattice being completely destroyed above 70"C, whereas Co-, Zn-and Cd-zeolites are stable up to 750-850°C. The adsorption of water on the latter zeolites is reversible. Ion-exchange isotherms for Co2+, Zn2+ and Cd2+ at three temperatures were obtained and the thermodynamic functions, AGO, AHo and AS", of the ion-exchange equilibria calculated. The thermodynamic data are discussed with respect to hydration and size of the cations. A possible explanation of the instability of Ni-zeolite is suggested.* samples stored over saturated NH4Cl solution at 22-23°C.?calculations based on the weight % assuming that the silica content corresponds exactly to 12 SiOz groups per unit cell.

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

“…Similar observations were made for zeolite 4A (Gal et al, 1971) and for natural Si-rich zeolites such as mordenite (Ni for NH/ exchange; Barrer and Townsend, 1976). The channels of the faujasite-type zeolites are significantly larger than zeolite-Pc and can host six types of exchangeable sites, including type-IV sites (Breck, 1974).…”

“…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.…”

Heat of adsorption of carbon dioxyde and ethene on zeolites a exchanged with Li+, Ni2+ and Cu2+

“…The cation content may even exceed the theoretical value of 12 elementary charges per a cage, whereas the exchanging cation coneentration in the solution remains below the solubility limit. The equilibrium concentration of the divalent cation is almost zero up to an exchange level of 19% (for Ni z+) or 46% (for Cue+), a result which confirms the high selectivity of zeolite A towards divalent cations [3]. At higher exchange levels, the selectivity remains favourable for copper, but reverses for nickel, since the Ni2+/Na + ratio becomes higher in the aqueous phase than in the zeolite.…”

Ion Exchange of Divalent Cobalt and Iron with Na–Y Zeolite: Binary and Ternary Exchange Equilibria

“…This method has the decided advantage of minimal associated waste generation, process simplicity, and ease of maintenance. Cobalt exchange from aqueous media using both synthetic (10)(11)(12)(13)(14)(15)(16)(17) and naturally occurring (17)(18)(19)(20)(21)(22) zeolites has been reported. The process of cobalt exchange with zeolites has been undertaken largely with the aim of preparing solid catalysts (23)(24)(25)(26).…”