The interfacial activity of asphaltenes, naphthenic acids, and naphthenates has been amply studied in the literature, as they are involved in the formation and stabilization of bitumen and heavy crude oil emulsions. While most of the literature evaluates one component at a time, in this work these bitumen components were separated one at a time from Athabasca bitumen, and the surface activity of the resulting fraction was evaluated as a function of pH, solvent aromaticity (heptane/toluene mixtures, known as heptol, at volume ratios 50/50 and 80/20), and temperature for selected systems. The interfacial activity was evaluated in two ways: via dynamic interfacial tension during adsorption on a bitumen drop of constant volume, and via dynamic interfacial tension during drop volume cycling. The adsorption data were interpreted using a model that combined multicomponent adsorption kinetics inspired by Langmuir–Freundlich kinetics with the Fainerman surface equation of state. The volume cycling experiments were interpreted using the compression relaxation model, which segregates adsorption/relaxation effects from elastic phenomena at interfaces. Overall, the adsorption data confirmed that naphthenic acids are the fastest adsorbing species that tend to dominate the interface, but that asphaltenes adsorb, almost irreversibly, at longer time scales and likely forming a sublayer previously proposed in the literature. The dilatational elasticity of the interface seems to be highly influenced by that asphaltene sublayer, which softens at high pH at room temperature, or at 80 °C independently of the pH of the system.

中文翻译：

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沥青组分的界面活性

沥青质，环烷酸和环烷酸酯的界面活性已经在文献中进行了充分的研究，因为它们参与了沥青和重质原油乳液的形成和稳定化。尽管大多数文献一次评估一种组分，但在这项工作中，这些沥青组分一次与Athabasca沥青分离了一次，所得级分的表面活性被评估为pH，溶剂芳香性（庚烷/甲苯）的函数。混合物，体积比分别为50/50和80/20的庚烷，以及所选系统的温度。通过两种方式评估界面活性：通过吸附在恒定体积的沥青液滴上的动态界面张力，以及通过液滴循环过程中的动态界面张力。吸附数据使用模型进行解释，该模型将Langmuir-Freundlich动力学启发的多组分吸附动力学与Fainerman表面状态方程相结合。使用压缩松弛模型解释了体积循环实验，该模型将吸附/松弛效应与界面处的弹性现象区分开来。总的来说，吸附数据证实了环烷酸是最快的趋于支配界面的吸附物种，但沥青质几乎不可逆地以较长的时间尺度吸附，并可能形成先前文献中提出的亚层。界面的膨胀弹性似乎受到沥青质亚层的强烈影响，该沥青质亚层在室温下于高pH下会软化，