Lattice Model for water-solute mixtures

TL;DR

This paper introduces a lattice model for water-solute mixtures using an adapted associating lattice gas approach, successfully reproducing various excess properties and phase behaviors of different types of solutions.

Contribution

The study develops a lattice model that captures the phase behavior and excess properties of water-solute mixtures with different interaction types, aligning qualitatively with experimental data.

Findings

Model reproduces phase diagrams with gas, low and high density liquid phases.

Qualitative agreement with excess volume and enthalpy of various aqueous solutions.

Different interaction parameters simulate behaviors of small alcohols, large alcohols, and ionic liquids.

Abstract

A lattice model for the study of mixtures of associating liquids is proposed. Solvent and solute are modeled by adapting the associating lattice gas (ALG) model. The nature of interaction solute/solvent is controlled by tuning the energy interactions between the patches of ALG model. We have studied three set of parameters, resulting on, hydrophilic, inert and hydrophobic interactions. Extensive Monte Carlo simulations were carried out and the behavior of pure components and the excess properties of the mixtures have been studied. The pure components: water (solvent) and solute, have quite similar phase diagrams, presenting: gas, low density liquid, and high density liquid phases. In the case of solute, the regions of coexistence are substantially reduced when compared with both the water and the standard ALG models. A numerical procedure has been developed in order to attain series of results at constant pressure from simulations of the lattice gas model in the grand canonical ensemble. The excess properties of the mixtures: volume and enthalpy as the function of the solute fraction have been studied for different interaction parameters of the model. Our model is able to reproduce qualitatively well the excess volume and enthalpy for different aqueous solutions. For the hydrophilic case, we show that the model is able to reproduce the excess volume and enthalpy of mixtures of small alcohols and amines. The inert case reproduces the behavior of large alcohols such as, propanol, butanol and pentanol. For last case (hydrophobic), the excess properties reproduce the behavior of ionic liquids in aqueous solution.