Effect of Hydrogen Ion on Cation-Exchange Processes

The other interfacial process involving hydrogen ion is the cation-exchange process in the interlayer space. When montmorillonite is suspended in water or in an electrolyte solution, a part of exchangeable cations can be dissolved. In Table 2.7, the relative quantity of calcium ions dissolved in water or in acidic solutions is shown. 

As seen in Table 2.7, the lower the pH, the greater quantity of calcium ions dissolved. The dissolved calcium ions are substituted by hydrogen ions in the interlayer space. In other words, the cations in the interlayer space of montmorillonite react with water itself, and a hydrogen-calcium cation-exchange reaction takes place  

The Quantities of Calcium, Silicon, Aluminum, and Magnesium Dissolved into Solution from Montmorillonite Expressed as the Percentages of the Total Silicon, Aluminum, and Magnesium Content of Montmorillonite at Different Equilibrium pH Values (m = 10 mg Ca-Montmorillonite, V= 20 cm3 HCI04 Solution with Different pH, T=20°C, t = 1 h) 

Source Reprinted from Nagy et al. 1997, with permission from Elsevier. 

FIGURE 2.6 Hydrogen ion-exchange isotherm in Ca-montmorillonite/hydrogen-ion exchange. T = 20°C. 

---