Aggregation Of Silica Particles As Pseudo Oil Sands In Non-Aqueous Media

The aggregation of micron-sized silica particles in non-aqueous (i.e. hydrocarbon) media was examined on both the macroscopic and microscopic scales. The silica surfaces were either“clean”(i.e. untreated) or“treated”(i.e. with irreversibly adsorbed materials from Athabasca bitumen); the hydrocarbons were mixtures of toluene and n-heptane at various ratios (to allow for different degrees of“aromaticity”in the solvent). On the macroscopic scale, gravity settling of the silica particles in non-aqueous media was monitored, and particle-particle interactions were characterized semi-empirically by the initial rates of sedimentation. On the microscopic scale, the microscope images of suspensions of bitumen-treated silica in non-aqueous media clear presented that the particles began to manifest themselves as large aggregates, with the floc size increasing seemingly monotonically with decreasing solvent aromaticity. Moreover, the interactions between individual glass spheres (both untreated and bitumen-treated) were directly examined using micropipette technique in non-aqueous media. It was found that there were interactions existed between two untreated glass spheres in toluene and in n-heptane, and also existed between two bitumen-treated glass spheres in n-heptane. However, there were no interactions between two bitumen-treated glass spheres in toluene. The interactions (i.e. adhesive forces) between individual glass spheres were then directly quantified using the microcantilever technique (again, in non-aqueous liquids). It was found that, for untreated silica spheres, the settling rates of the suspensions were relatively insensitive to the interparticle adhesive forces. This is in contrast to the case for treated silica particles, where strong correlation was observed between the settling rate and particle-particle adhesion. The surfaces of both bitumen-treated and untreated silica particles were further investigated by X-ray photoelectron spectroscopic analysis. It was observed that N and S species that coming from bitumen materials existed on the surface of bitumen-treated silica comparing to the untreated silica particles. Supposing these bitumen staff was evenly adsorbed onto the surface of silica (in ideal situation), the thickness of this coating is less than 5 nm. Besides, the preliminary study on the gravity settling of the bitumen-treated silica particles in non-aqueous media (toluene-heptane mixture with bitumen) was also conducted. And it was found that silica settled slower when bitumen exists. These findings may have important relevance to the commercial“paraffinic froth treatment”process.