Ion exchange and dewaterability of clay sludges

Two clay gel systems, a sample of settled oil sands clay tailings and a montmorillonite gel, were effectively dewatered by conversion to calcium forms by ion exchange, followed by freezing and thawing in the case of the montmorillonite gel and by either centrifugation or freezing and thawing in the case of the oil sands slime. Maximum dewatering was shown to be associated with complete conversion to the calcium forms. The implications of caustic recovery during the process are discussed.