Abstract
Effects of imogolite addition on colloidal stability of montmorillonite and kaolinite were examined to clarify the colloidal properties of imogolite which coagulates in alkaline condition. One to one mixture of montmorillonite and imogolite coagulated at any pH. Observation through transmission electron microscope revealed that montmorillonite and imogolite, including the mixture with lower imogolite concentration, mutually flocculated (formed a domain) at any pH. Non-deferrated kaolinite coagulated below pH 5.9 and dispersed above pH 6.0, whereas 5% imogolite added sample showed the opposite stability. Deferrated kaolinite dispersed above pH 4.2, whereas 10% imogolite added sample coagulated at any pH. All the imogolite added samples microscopically flocculated both under acidic and alkaline conditions. In acidic conditions, it was attributed to the electrostatic attraction between permanent negative charge of crystalline clay minerals and variable positive charge of imogolite. In alkaline conditions, it was considered to be resulted by the neutralized surface charge of imogolite.
