Selective Cu²⁺ and Pb²⁺ Exchange with Highly Charged Cation Exchanger of Na-4-Mica

Abstract

Selective cation exchange for Cu and Pb has been demonstrated with the high-charge-density sodium fluorophlogopite mica, Na-4-mica. The 2Na⁺ → M²⁺ exchange reaction (M = Cu or Pb) was investigated with Na-4-micas prepared by two different synthetic processes. One was easily and economically prepared by crystallization from a mixture of NaF, MgO, and metakaolin, the latter serves as an inexpensive aluminosilicate source. Another was prepared by solution-sol-gel processing. Ion-exchange isotherms for Cu²⁺ and Pb²⁺ were obtained at room temperature. The thermodynamic functions for the initial ion-exchange reactions were calculated because the isotherms were not completed. High selectivities for both copper and lead exchange were found on the highly crystallized Na-4-mica prepared from metakaolin. Their ion-exchange capacities were 225 and 257 milliequivalents per 100 g of dry clay for Cu²⁺ and Pb²⁺, respectively. This high level decontamination of copper and lead with the highly crystallized Na-4-mica from metakaolin will be a very important separation required for purification of drinking water as well as for wastewater treatment and disposal.

ACKNOWLEDGMENT

This work was supported by the Interfacial, Transport and Separation Program, Chemical and Transport Systems, Division of the National Science Foundation under Grant CTS-9612714.