Liquid-liquid equilibria of water + ethanol + castor oil and the effect of cellulose nanocrystal/Fe3O4 and lignin/Fe3O4 nanoparticles

Abstract

Castor oil has been proposed as a renewable solvent for the liquid extraction of ethanol from water as an alternative to more traditional energy intensive distillation-based methods. The liquid–liquid equilibrium (LLE) of the ternary system water + ethanol + castor oil was determined at 295.15 K using high performance liquid chromatography (HPLC). Castor oil was herein treated as a pseudo-component with the molecular weight of the triglyceride of ricinoleic acid. The experimental data was fitted to the UNIQUAC and NRTL models to obtain parameters for castor oil, and binary interaction parameters for castor oil/ethanol and castor oil/water pairs. The separation factors and distribution coefficients of water and ethanol were calculated at ethanol concentrations ranging from 2.73 ± 0.35 to 55.8 ± 1.1 wt%, with a high separation factor of 12.7 ± 3.3, and a distribution coefficient of 0.352 ± 0.078, at the lowest ethanol concentration tested. Moreover, iron oxide-coated cellulose nanocrystals (CNC@Fe3O4) and Kraft lignin-coated iron oxide (lignin@Fe3O4) nanoparticles (NPs) were added to the castor oil + water + ethanol mixtures at 0.01 g/g mixture, to investigate the effect of the NPs in altering the LLE of the system. It was found that the NPs had a negligible (<1%) effect on the thermodynamic equilibrium, which opens the possibility of using them in advanced applications such as the magnetically controlled demulsification of stable dispersions generated during liquid–liquid extraction process.