Contamination of the environment with heavy metals, including cationic radionuclides, is a serious problem which has yet to be fully overcome. A class of potentially effective cation exchangers for sequestering heavy metals which has received little attention is K-depleted mica. The purpose of this study was to investigate the heavy-metal cation exchange properties of K-depleted phlogopite and biotite, which were prepared from a natural phlogopite and biotite, respectively, using sodium tetraphenylborate (NaTPB). The X-ray diffraction (XRD) patterns showed that interlayer K+ ions were completely replaced with exchangeable Na+ ions, resulting in the expansion of the d001 spacing of both K-depleted phlogopite and K-depleted biotite. In order to investigate the cation exchange selectivity of K-depleted phlogopite and biotite for Co 2+ and Ni2+, cation exchange isotherms and Kielland plots were constructed. The isotherms and Kielland plots indicated that both K-depleted phlogopite and biotite are highly selective for Co2+ as well as Ni2+. The XRD patterns after both 2Na+ → Co2+ and Ni2+ exchange reactions suggest that double sheets of interlayer water are present in the interlayer. These K-depleted micas are potential cation exchange materials for removal of some heavy metals such as Ni and radioactive species such as 60Co from solution.
All Science Journal Classification (ASJC) codes
- Water Science and Technology
- Soil Science
- Geochemistry and Petrology
- Earth and Planetary Sciences (miscellaneous)