Surfactants exist in atmospheric aerosols mixed with inorganic salts and can significantly influence the formation of cloud droplets due to bulk–surface partitioning and surface tension depression. To model these processes, we need continuous parametrizations of the concentration dependent properties of aqueous surfactant–salt solutions for the full composition range from pure water to pure surfactant or salt. We have developed density functions based on the pseudo-separation method and Young’s mixing rule for apparent partial molal volumes for solutions that mimic atmospheric droplets of marine environments. The developed framework requires only model parameters from binary water–salt and water–surfactant systems and includes the effect of salinity on micellization with composition-dependent functions for the critical micelle concentration (CMC). We evaluate different models and data available in the literature to find the most suitable representations of the apparent partial molal volume of sodium chloride (NaCl) in aqueous solutions and the CMC of selected atmospheric and model surfactants in pure water and aqueous NaCl solutions. We compare model results to experimental density data, available in the literature and obtained from additional measurements, for aqueous solutions containing one of the ionic surfactants sodium octanoate, sodium decanoate, sodium dodecanoate or sodium dodecylsulfate mixed with NaCl in different relative ratios. Our model follows the experimental trends of increasing densities with increasing surfactant concentrations or increasing surfactant–salt mixing ratios both, below and above the CMC, capturing the effect of the inorganic salt on the surfactant micellization.

中文翻译：

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离子表面活性剂和盐的三元水溶液的组成依赖密度

表面活性剂存在于与无机盐混合的大气气溶胶中，由于体积-表面分配和表面张力降低，可以显着影响云滴的形成。为了模拟这些过程，我们需要对从纯水到纯表面活性剂或盐的整个组成范围的表面活性剂 - 盐水溶液的浓度相关特性进行连续参数化。我们已经开发了基于伪分离方法和杨氏混合规则的密度函数，用于模拟海洋环境大气液滴的溶液的表观偏摩尔体积。开发的框架只需要来自二元水 - 盐和水 - 表面活性剂系统的模型参数，并包括盐度对胶束化的影响，以及临界胶束浓度（CMC）的组成依赖函数。我们评估了文献中可用的不同模型和数据，以找到水溶液中氯化钠 (NaCl) 表观偏摩尔体积的最合适表示以及纯水和 NaCl 水溶液中所选大气和模型表面活性剂的 CMC。对于包含离子表面活性剂辛酸钠、癸酸钠、十二烷酸钠或十二烷基硫酸钠之一以不同相对比例与 NaCl 混合的水溶液，我们将模型结果与在文献中可获得并从额外测量中获得的实验密度数据进行比较。我们的模型遵循随着表面活性剂浓度的增加或表面活性剂-盐混合比的增加而增加密度的实验趋势，低于和高于 CMC，