Effect of solvent addition on bitumen–air bubble attachment in process water

Abstract

Bitumen–air bubble attachment is an essential element for bitumen recovery from oil sands by flotation. Effect of solvent addition to bitumen on bitumen–air bubble attachment in an industrial process water was investigated by determining the minimum time required to achieve the bitumen–air bubble attachment, known as induction time. Proper addition of solvent to bitumen significantly reduced the induction time of bitumen–air bubble attachment, more so for naphtha than for toluene and reaching optimal at 10wt% solvent added to bitumen. The measurement of bubble coalescence time and total organic carbon content in the resulting process water revealed a critical role in bitumen–air bubble attachment of air bubble interfacial properties controlled primarily by surfactants in the process water and water chemistry. Increasing the solvent addition to bitumen led to an increased migration of natural surfactants to the bitumen–water interface. At a given solvent dosage, more surfactants adsorbed at toluene–diluted bitumen–water interface than at naphtha–diluted bitumen–water interface. Interestingly, zeta potentials of diluted bitumen droplets in the process water exhibited a maximum at about 10wt% of solvent addition to bitumen for both toluene and naphtha. At an identical dosage of solvent, toluene–diluted bitumen in the tailings water possesses a more negative zeta potential than naphtha–diluted bitumen. Finally, a possible adsorption mechanism of ions and surfactants accumulating at the diluted bitumen–water interface under the impact of solvent addition is proposed.