Electrophoretic Properties of Oil Sands Tailings And Constituent Clays In Aqueous Suspensions

Abstract

Abstract Electrophoretic mobilities of various clays and their mixtures were measured atseveral temperatures in solutions having different pH values and differentconcentrations of added electrolytes (NaCI and CaCI2). Similarmeasurements have been made on kaolinite suspended in both real and syntheticoil sands tailings water. Further electrophoretic measurements have been madeon oil sands tailings sludge solids suspended in " clean" solutions and inboth real and synthetic tailings water. Results of these measurementsand others that are cited are consistent with the view that the stability ofsuspensions of fine minerals (mostly clays) in oil sand tailings issubstantially due to the properties of mixed clay colloids and possibly also tointeractions of these clays with bituminous organic substances that are sotightly bound to the clays that they are not removed by " ordinary" chemical treatment. Introduction Present commercial recovery of bitumen from the Athabasca oil sands of Alberta is accomplished by way of treatment of mined oil sands with largeamounts of hot water, as reviewed by Camp(J) and by Berkowitz and Speight(2). We are here concerned with the tailings or " pondwater" problem associated with this process, as reviewed by Camp(3) and by Kessick(4). This pondwater problem can be described concisely as thelarge-scale accumulation of water. fine minerals (mostly clays) and unrecoveredbitumen from the hot water process that is used for recovery of bitumen frommined oil sands; much of the water contains too much suspended solids forrecycling, and the slowly settling " solids" contain too much water forappropriate disposal. Similar tailings problems involving fine clays are commonin other mineral processing industries. Previous investigations of oil sands tailings have focussed either on the water(including dissolved substances) or on the suspended solids (including theirinteractions with the water). Results of investigations of the aqueous phasehave been reported recently by Burchfield and Hepler(5), who havealso reviewed earlier related investigations. Investigations of the suspendedsolids have been reviewed extensively by Kessick(4); here we citeonly some more recent investigations(6–19), with titles thatgenerally indicate the kinds of investigations carried out. Although there are substantial differences between the analytical results fromdifferent investigators, partly because different investigators have workedwith different samples, it is now well established that the principalconstituents of tailings fines from the Athabasca oil sands are clays(kaolinite, illite, montmorillonite, etc.) and silica. These findingshave led to our choices of specific systems for investigations. (Figure in full paper) Because our investigations are concerned with the electrophoreticproperties of oil sands tailings and of certain clays in aqueous suspensions, we call particular attention to the following earlier investigations. May and Smelley(13) have reported the results of their electrophoreticinvestigations of Florida phosphatic day wastes and have cited earlierinvestigations that illustrate the relevance of such investigations to theirproblem which is partly similar to our tailings problem. We also callattention to four investigations(20–23) of electrophoreticproperties of aqueous day suspensions and the relationships of theseelectrophoretic properties to other properties.