Na-4-mica: Cd2+, Ni2+, Co2+, Mn2+ and Zn2+ ion exchange

Abstract

Selective cation exchange for divalent transition metals of Cd, Ni, Co, Mn and Zn has been investigated with the high-charge-density sodium fluorophlogopite mica, Na-4-mica. The Na-4-mica was easily and economically prepared by the crystallization from a mixture of NaF, MgO and metakaolin, the latter serves as an inexpensive aluminosilicate source. Ion exchange isotherms for Cd 2+ , Ni 2+ , Co 2+ , Mn 2+ and Zn 2+ were obtained at room temperature and the thermodynamic functions of the ion exchange equilibria were calculated. The 2Na + →M 2+ exchange with the Na-4-mica showed the following selectivity: Zn 2+ >Ni 2+ ≈Co 2+ ≈Cd 2+ >Mn 2+ . The interlayer structure of the hydrated Na-4-mica with the open interlayer space in the range 12.1-13.9 A was retained during the ion-exchange reaction, indicating the possibility of the reversible 2Na + ⇄M 2+ exchange. The basic selective cation exchange studies of the high-charge-density ion exchanger are of relevance in recovery of metals from waste solution, and waste water treatment and disposal.