Salt-Dependent Liquid–Liquid Equilibria and Pyridine Partitioning in Water + Pyridine + 2‑Ethyl-1-hexanol Systems with KCl and CaCl₂

Aqueous phases containing 5 and 10 wt % KCl and CaCl₂ were systematically studied. Experimental results show that both inorganic salts expand the two-phase region, promote pyridine partitioning into the rich-organic phase, and enhance separation efficiency.

The pyridine distribution coefficient and separation factor generally increase with the salt concentration. Relative to the salt-free system, the average separation factor rises by approximately 42.01% and 111.10% for 5 and 10 wt % KCl, respectively, and by 19.17% and 74.27% for the corresponding CaCl₂ concentrations, respectively. Experimental LLE data were correlated using NRTL and UNIQUAC activity coefficient models, with RMSD below 1.02%.