Purification and characterization of smectite clay taken from Gafsa, Tunisia: Progressive elimination of carbonates

This work shows the results of various analysis on a representative clay sample from southern west of Tunisia, particularly from Oued Tfal near the town of Gafsa. The raw smectite contains some carbonate, quartz, chlorite, and anorthite. During the attack of the carbonate clay with a solution of hydrochloric acid, a change of the chemical composition and physical properties was observed. This change is dependent on several factors: the initial concentration of the acid, the nature of the clay, the ratio acid / clay...). Although treatment to 0.5 M represents a total removal of carbonates, there are probably altered layers of the clay fraction. The result shows that for a treatment with acid solutions of concentrations below 0.5 M there is gradual removal of carbonate without protonation of the clay layers. The characterization of the clay fraction shows that the sodium clay purified (OTNa) consists of a sodium montmorillonite smectite. The cation exchange capacity and the specific surface of OTNa measured using the method of methylene blue are equal to 82 meq/100g and 667 m2 / g respectively.