Reconciliation of Solute Concentration Data with Water Contents and Densities of Multi-Component Electrolyte Solutions

Abstract

Density and chemical masses are two of the most important parameters tracked in chemical plant flowsheets. Unfortunately, chemical plant laboratories commonly avoid density and solvent concentration measurements. Without these data, it is difficult to reconcile solute concentrations reported by the laboratories with the total mass and volume tracked in flowsheets. In this paper, the Laliberté-Cooper density model is used in conjunction with a numerical algorithm to simultaneously estimate both density and water content from measured solute concentrations for aqueous electrolyte solutions. The algorithm numerically optimizes the water content until the sum of the water and solute concentrations (in mass per volume units) equals the density predicted by the Laliberté-Cooper model for that composition. The algorithm was tested against an experimental dataset of simulated nuclear waste supernatant solutions containing mixtures of ten different electrolytes with total ionic strengths up to 8 mol⋅L⁻¹. The algorithm was able to predict the measured densities with an R² of 0.9912 and an average relative percent error of just 0.05%. The model error was not correlated to the estimated water content or any of the electrolyte concentrations. Thus, the algorithm can be successfully used to simultaneously predict density and water content of aqueous electrolyte solutions containing many electrolytes at high concentrations from analytical data reported in moles or mass of solute per volume.