Viscosity is an important transport property for chemical systems, especially in terms of heat and mass transfer calculations and process simulation. Accurate engineering viscosity models for aqueous electrolyte solutions are of high interest to scientists and engineers tasked with development of desalination and treatment of high salinity produced water from oil and gas productions. Such viscosity models should cover high solute concentrations, high temperature conditions, and multi-component solutions.
Many models exist for viscosity calculations of aqueous electrolyte solutions. However, these models have significant drawbacks undesirable for engineering calculations. These issues include 1) not being developed with a diverse range of electrolytes in mind, such as limiting model validation to alkali halides as solutes; 2) complex calculations requiring large numbers of parameters, as is with the Jiang-Sandler model [Jiang and Sandler, Ind. Eng. Chem. Res., 2003, 42 (25), pp 6267-6272]; and 3) lack of theoretical explanation, making calculations impossible when experimental data is not available, such as is with the original Jones-Dole [Jones and Dole, J. Am. Chem. Soc., 1929, 51 (10), pp 2950-2964] and Andrade equations [Andrade, Philos. Mag., 1934, 17 (112), pp 698-732].
Here we present a new viscosity model built on the Andrade equation to calculate the viscosity of aqueous electrolyte solutions. The ionic strength-based expression considers ion-specific contributions as either structure making or structure breaking. The ion-specific contributions are directly correlated with the charge of the ions and their size relative to the solvent, water. Organic electrolytes are known to behave differently from other electrolytes, a behavior that is accounted for within the expression. Beyond the solute concentrations, the model requires only the radius of the anions and cations that are present in order to perform calculations. The expression should find relevance in industrial calculations as the model is applicable to a broad range of electrolyte solutions, accounts for high ionic concentrations, incorporates temperature effects, and provides a mixing rule for multicomponent electrolyte systems.
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