Cation-exchanged montmorillonites, near

The apparent discrepancy could reside in the fact that if potassium ions are available at all, they will form a mica at temperatures near 100°C. Montmorillonite structures below these conditions (pressure and temperature) need not contain potassium at all. However, at the correct physical conditions the 2 1 portion of the montmorillonite must change greatly (increase of total charge on the 2 1 unit) in order to form a mica unit in a mixed layered mineral phase. Since neither Na nor Ca ions will form mica at this temperature, potassium will be selectively taken from solution. Obviously this does not occur below 100°C since cation exchange on montmorillonites shows the reverse effect, i.e., concentration of calcium ions in the interlayer sites. If potassium is not available either In coexisting solids or in solutions, the sodi-calcic montmorillonite will undoubtedly persist well above 100°C. 

Figure 9 illustrates better the influence of pH and molecular structure on the adsorption of 5-triazines by clay and organic matter. Maximum adsorption occurred near the pKa of each compound, suggesting that basicity was a significant factor in their adsorbability by particulate matter. Adsorption of other basic molecules by cation exchange adsorbents, including atrazine by a carboxyl resin (118), amitrole by mont-morillonite (84) and organic matter (83), and purines and pyrimidines by montmorillonite (119), exhibit similar responses. 

An impure montmorillonite clay, contaminated and other minerals it is one of the few sources in this country. Fuller s Earth was formerly —removing fatty substances from wool, this to its large surface area, which gives it great It has a high cation-exchange capacity, the cation being Ca. The only important deposit near Nutfield, Surrey. 

---