Bitumen–solids attachment induced by cation activation.

Interactions between negatively charged bitumen and fine solids under oil sands extraction conditions were simulated using mature fine tailings (MFT) and hydrocarbon oil with dissolved carboxylic acids. Their attachment induced by cation activation was evaluated with different types of cations by simple dynamic attachment tests. The results revealed that solid hydrophobization by adsorbing surfactants was key for oil–solid attachment. Activation by multivalent metal cations was due to surface precipitation of metal hydroxides, followed by chemisorbing anionic surfactants on metal‐activated solids to form metal carboxylate complexes/precipitates, thereby hydrophobizing the solids. Activation by cationic surfactants depended on their hydrocarbon chain lengths. For short hydrocarbon chains, where hydrophobic interaction is weaker than electrostatic interaction between the added cationic and anionic surfactants, the added cations promote the adsorption of anionic surfactants by electrostatic interaction to render the solids hydrophobic. For long hydrocarbon chains where hydrophobic interaction is stronger than electrostatic interaction between the added cationic and anionic surfactants, the adsorption of anionic surfactants occurs through the hydrophobic association of the hydrocarbon chains, posing the head group towards water, thereby making the solids less hydrophobic. Activation by cationic flocculants was purely physical (hydrogen bonding and electrostatic): when the solids were turned positive by the added cationic flocculants, the added anionic surfactants then adsorbed onto the solids to render them hydrophobic. It appeared that soluble multivalent metal species (e.g., Ca2+ and Mg2+) were much less harmful to bitumen extraction than those heavy metals coated on the solids, either in the form of surface precipitates or hydrolyzed ionic species. [ABSTRACT FROM AUTHOR]