Chapter 4 Synthetic Clay Minerals and Purification of Natural Clays

This chapter describes synthetic clay minerals and purification of natural clays. A complete purification cycle is time consuming. However, not all the purification steps are always necessary; steps can be omitted depending on the purpose of the investigation. In contrast to soil clays, clays from geological deposits (such as bentonites, and kaolins) commonly contain only small amounts of organic materials. As such, oxidation with H2O2 or peroxodisulphate may not be required and the simplified procedure may be satisfactory. Similarly, silica does not always act as a cementing agent, and it can be removed without chemical treatment. Even small amounts of carbonates, (hydr)oxides, and organic materials can strongly influence the colloidal and rheological properties of clay pastes, slips, and dispersions. The chemical reactions involved in clay mineral purification may also cause changes to the clay mineral structure. In selecting a given purification procedure, the effect of different reactions must be duly considered.