Improved estimates of power consumption during dewatering of mine tailings using electrokinetic geosynthetics (EKGs)

Electrokinetic geosynthetics (EKGs) were developed about a decade ago, producing a material that did not experience the same corrosion problems as metal electrodes when used in electro-osmotic (EO) dewatering applications. The conductive polymeric material from which EKGs are made has the additional advantage of being able to be formed into a variety of shapes, including drainage tubes such as those used in this study. One of the primary concerns regarding EO dewatering applications is the rate of energy consumption. This paper reports experiments at three different scales, on different mine tailings materials, that illustrates the potentially misleading results obtained from small scale laboratory tests. Using large, outdoor tests, power consumption rates for treating a kaolinitic mineral sands tailings and a smectitic diamond tailings were found to be up to 30 times lower than the power consumption rates obtained from laboratory tests using small samples in a purpose built EO cell. The primary reason for the improved performance is thought to be the lower voltage gradient used in the field tests, plus the geometric advantages offered by a field layout where a greater volume of material is exposed to the EO effect than only the material directly between the electrodes, which is the case in the EO cell tests. Finally, in the field tests the EO treatment caused the early development of vertical cracks in the tailings, resulting in increased exposure of the tailings to the effects of solar drying. This effect cannot obviously be reproduced in the EO cell laboratory tests, and can be a major advantage for the in situ treatment of mine tailings lagoons, where in some materials the onset of cracking is significantly delayed by the development of an impermeable surface crust. (C) 2009 Elsevier Ltd. All rights reserved.