Heterogeneous Distribution of Adsorbed Bitumen on Fine Solids from Solvent-Based Extraction of Oil Sands Probed by AFM

5 years ago

Heterogeneous Distribution of Adsorbed Bitumen on Fine Solids from Solvent-Based Extraction of Oil Sands Probed by AFM

Xin Cui, Jingyi Wang, Jun Huang, Xiaoli Tan, Hongbo Zeng, Qi Liu, Jing Liu

Mineral particles encountered in oil production and many chemical processes are generally adsorbed with organics (e.g., bitumen), playing an important role in determining their wettability and interaction behaviors. In this work, the surface properties of fine solids, collected from the solvent-based extraction of Athabasca oil sands using cyclohexane as the extraction solvent, have been systematically characterized by several complementary techniques. The fine solids were shown to be mainly composed of silica and aluminosilicate clays, analyzed using X-ray photoelectron spectroscopy and energy dispersive X-ray spectroscopy. The particle wettability was determined using the Washburn method. The mineral particle surfaces were further characterized by atomic force microscope (AFM) techniques. Various regimes on the particle surfaces with and without adsorbed bitumen were identified and distinguished using PeakForce quantitative nanomechanics AFM imaging of surface topography, adhesion, modulus, and deformation simultaneously in air. The results demonstrated that the adsorbed bitumen was heterogeneously distributed on the particle surfaces. Such surface heterogeneity was further confirmed by AFM force mapping using a hydrophobized AFM tip on fine solids in water. The force–separation profiles obtained on relatively hydrophilic mineral regimes could be well fitted by the classical Derjaguin–Landau–Verwey–Overbeek (DLVO) model, while additional hydrophobic interaction should be included in the modified DLVO model for the interactions on more hydrophobic domains (with adsorbed bitumen). This work provides a facile and useful methodology for characterizing the surface properties of fine solids in oil production, with implications for an improved understanding of the interaction mechanisms of particles suspended in bitumen products in oil production. The methodology can be readily extended to characterizing the surface properties of many other particles and substrates in a wide range of chemical processes and engineering applications.

Publisher URL: http://dx.doi.org/10.1021/acs.energyfuels.7b00396

DOI: 10.1021/acs.energyfuels.7b00396