CLAY MINERALS

Smectites

The most common smectite minerals range in composition between three end-members: montmorillonite, beidellite, and nontronite. All are dioctahedral, but they differ in the composition of the tetrahedral and octahedral sheets.

Montmorillonite

Montmorillonite belongs to the smectite family and is composed of two silica-based tetrahedral sheets with water molecules within the interlayer sheets and are easily available for the incoming contaminants. Organoclays are obtained when there is inorganic–organic ion exchange in the interlayers of the clays which can be proven as an effective adsorbate for organic and aromatic pollutants

TC is used as broad spectrum of antibiotics in human, animals, and in agriculture, and their adsorption on montmorillonite has been proven in many studies when it comes to its surface charge interaction between the adsorbate and the adsorbents (Browne et al., 1980; Parolo et al., 2008). Most of the mechanism postulates a cationic exchange–controlled process on the montmorillonite at relatively lower pH, and the intercalation between the interlayer spacing of the montmorillonite were speculated as well.

The removal of chlorpheniramine (CP), prominently used antihistamines in human and veterinary medicines, by Ca-montmorillonite was studied in Li et al. (2011). CP adsorption on clay made the slate structures between the clays to swell and have the molecule embeded within the spacing. The isotherm in this study showed a Langmuir fit with a capacity of over 0.72 mmol/g (Li et al., 2011).