Extraction is a complex and also a key unit operation for separating and recovery of bitumen in oil sand industry. It has been reported that calcium and magnesium ions cause reduction in bitumen recovery. Experimental evidences showed that hardness ions in water act as a binder between montmorillonite clay particles and bitumen droplets (hetero-coagulation process), resulting in a coating layer of clay particles on the bitumen surface. This layer of clay particles on bitumen droplets causes a barrier for bitumen-air bubble attachment and results in poor bitumen recovery. Therefore, if it is possible to prevent Ca and Mg ions from taking part in hetero-coagulation process then recovery should increase. In this paper, the results of a theoretical and experimental approach to handle the hardness ions effect on bitumen extraction have been reported. For enhancing recovery of bitumen in oil sand extraction operation, for the first time magnetic treated process waters were used. The idea was checked firstly by using a novel technique for investigating the interaction among components of a suspension of bitumen, montmorillonite clay and hardness ions from the interaction measurement of zeta potential distributions. The idea was checked finally by running three sets of extraction experiments in batch scale using process waters. The experimental results show that the bitumen recovery in extraction operation can be enhanced by using magnetic treated process water. (C) 2005 Elsevier B.V. All rights reserved.