Selective Cobalt (II) Exchange Properties of Na-2-Mica and Na-ETS-4

Co ²⁺ exchange isotherms and Kielland plots were determined for highly-charged sodium swelling mica (Na-2-mica) and sodium Engelhard Titano-Silicate-4 (Na-ETS-4). The results showed that both Na-2-mica and Na-ETS-4 were highly selective for Co ²⁺ at X̄ _Co (equivalent fraction) of < 0.3. X-ray diffraction (XRD) patterns after 2Na ⁺ → Co ²⁺ exchange process were examined to check for change in d ₀₀₁-spacing of Na-2-mica. As the uptake of Co ions increased, strong ~14 Å phase (two-layer hydrate) of Na-2-mica increased, while the ~12 Å phase (one-layer hydrate) decreased. These synthetic ion exchangers have a great potential for decontamination of radioactive or stable cobalt from waste water and soils.