Hildebrand Department of Petroleum and Geosystems Engineering, University of Texas at Austin, 200 E Dean Keeton St, Austin, TX 78712, USA.
Hildebrand Department of Petroleum and Geosystems Engineering, University of Texas at Austin, 200 E Dean Keeton St, Austin, TX 78712, USA.
J Colloid Interface Sci. 2022 Feb 15;608(Pt 3):2321-2329. doi: 10.1016/j.jcis.2021.10.154. Epub 2021 Nov 6.
The effect of salinity on Pickering emulsion stability to coalescence under dynamic forces present during flow in porous media for applications including enhanced oil recovery is poorly understood. Recent work suggests the absence of significant electrostatic repulsion in brine prompts unattached particles to assemble into inter-droplet networks that increase emulsion stability. We hypothesize that emulsions stabilized by nanoparticles coated with (3-glycidyloxypropyl)trimethoxysilane (GLYMO) will generate particle networks in brine and exhibit greater stability to coalescence than in deionized water (DI).
We stabilized decane-in-water emulsions with GLYMO-coated silica nanoparticles at various particle concentrations using brine and DI as the aqueous phase. We imaged the emulsions to calculate droplet diameters, then centrifuged the emulsions and weighed the volume of decane released to determine the extent of coalescence. We compared these measurements to evaluate the effect of salinity on emulsion stability.
Emulsions demonstrate greater dynamic stability and smaller droplet diameters with increasing nanoparticle concentration and salinity. Controlling for differences in droplet size, we observe that brine reduces the emulsion coalescence rate by a factor of 78 ± 23 relative to DI. This difference supports and quantifies past work suggesting that unattached nanoparticles aggregate in brine and increase overall emulsion stability, whereas nanoparticles in DI remain separated.
在多孔介质中流动时存在的动态力会影响盐度对 Pickering 乳液稳定性的影响，从而影响到提高采收率等应用，然而目前对于这种影响的理解还很有限。最近的研究表明，海水中缺乏显著的静电排斥作用会促使未附着的颗粒组装成液滴间的网络，从而提高乳液的稳定性。我们假设，用（3-缩水甘油丙基）三甲氧基硅烷（GLYMO）涂覆的纳米颗粒稳定的乳液在盐水中会形成颗粒网络，并且比在去离子水中（DI）更能抵抗聚结。
我们使用盐水和 DI 作为水相，用 GLYMO 涂覆的二氧化硅纳米颗粒在不同的颗粒浓度下稳定了正十二烷-水乳液。我们对乳液进行成像以计算液滴直径，然后离心乳液并称重释放的正十二烷的体积，以确定聚结的程度。我们将这些测量结果进行比较，以评估盐度对乳液稳定性的影响。
随着纳米颗粒浓度和盐度的增加，乳液表现出更大的动态稳定性和更小的液滴直径。在控制液滴大小差异的情况下，我们观察到盐水使乳液聚结速率相对于 DI 降低了 78 ± 23 倍。这一差异支持并量化了过去的研究结果，即未附着的纳米颗粒在盐水中聚集并提高了整体乳液稳定性，而 DI 中的纳米颗粒则保持分离。
