Multiscale modeling of mass transfer and adsorption in liquid-liquid dispersions. 1. Molecular dynamics simulations and interfacial tension prediction for a mixed monolayer of mono- and tetracarboxylic acids

Abstract

Phase space trajectories of protonated and deprotonated mono- and tetracarboxylic acid surfactants at an oil/water interface are obtained from molecular dynamics (MD) simulations and are employed to calculate the interfacial area of the molecules as a parameter for a molecular mixed monolayer model. Three simple methods, based on the available volume at the interface and the solvent accessible area, are applied to calculate the interfacial molecular areas from the MD trajectories. Experimental equilibrium interfacial tension (IFT) data for single component systems are employed with the calculated interfacial molecular areas to fully parametrize the model in order to predict the equilibrium IFT data for mixed solutions of mono- and tetraacids. The agreement between experiment and theory is found to be good. The methodology demonstrated here provides a tool to evaluate the effect of the bulk concentration and composition of various model crude oil surfactant compounds on their interfacial concentrations and composition upon the initial formation of a monolayer at a water/oil interface. In part 2 (Kovalchuk, K.; Riccardi, E.; Grimes, B. A.Multiscale Modeling of Mass Transfer and Adsorption in Liquid–Liquid Dispersions. 2. Application to Calcium Naphthenate Precipitation in Oils Containing Mono- and Tetracarboxylic Acids. Ind. Eng. Chem. Res. 2014, DOI: 10.1021/ie501296t), the parametrized monolayer model is employed to predict phase partitioning of compounds in liquid–liquid dispersions with a continuum model and the parameters determined in this work.