Role of Sodium Hydroxide in Bitumen Extraction: Production of Natural Surfactants and Slime Coating

  • Author / Creator
    Tamiz Bakhtiari, Marjan
  • Alkaline environment by addition of NaOH in bitumen extraction process often shows a positive effect on bitumen recovery from Athabasca oil sands by mining-extraction method. NaOH ionizes organic acids in the bitumen to produce surfactants. These species are essential for bitumen liberation. Understanding the role of NaOH in the processing of different types of oil sands ores is important in designing the processes to enhance bitumen recovery from variable oil sands ores and minimizing bitumen loss in the tailings. This study focuses on responses of 15 different ores to the addition of variable amount of NaOH in generation/release of natural surfactants from the ores. An existing FTIR technique was modified to quantify the concentration of carboxylic surfactants in tailings water. The results showed that the concentration of carboxylic type of surfactants in tailings water depends not only on the amount of NaOH addition, but also on bitumen content and composition, concentration of divalent cations and concentration of carbonate/ bicarbonate ions in the ores. The content of pyrite in the fines fraction of the solids was found also to affect the release of carboxylic type of natural surfactants in tailings water. The critical role of NaOH addition in levitating bitumen slime coating (bitumen-clay interaction) on a single ore using QCM-D method was also studied. The QCM-D measurements showed that illite clay particles formed layers of slime on bitumen in tailings water prepared at weak alkaline conditions while kaolinite did not. A key contribution of this work was to identify the positive effect of humic acids released from ores processed at high pH (pH > 10) on avoiding the slime coating of bitumen by clays. After determining a strong adsorption of humic acids by illite clays, the results of QCM-D measurements showed that the presence of humic acid released in tailings water at high pH reduced slime coating of bitumen by illite clay particles, which was initiated by the presence of surfactants in tailings water. The results revealed that the reduction in the slime coating was attributed to the increased hydrophilicity of the bitumen layer and steric hindrance caused by adsorbed humic acids on both bitumen and illite surfaces.

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    Doctor of Philosophy
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