Liquid–liquid phase equilibria in nicotine (aqueous) solutions

Liquid–liquid equilibria were measured for solutions containing: (1) nicotine, and one of the solvents PEG 200 or ethyl-lactate, and the ionic liquid 1-ethyl-3-methylimidazolium ethyl sulphate (ECOENG 212®); (2) a (nicotine + water) mixture of close to critical composition and one of the co-solvents PEG 200, or glycerol, or ethyl-lactate; and (3) a (nicotine + water) mixture and one of the salts ECOENG 212®, or sodium chloride, or sodium phosphate. The objective of these measurements was to assess the possibility of using environmentally friendly solvents for extraction/separation of nicotine from its (aqueous) solutions. PEG 200, glycerol and ethyl-lactate proved to be good co-solvents of nicotine in water. On the other hand, the inorganic salts Na3PO4 and NaCl showed remarkable salting-out effects in nicotine aqueous solutions, achieved using very small quantities of these salt. The effects of the ionic liquid (molten salt) ECOENG 212®, were, however, much more complex. Depending on its concentration in the solvent, it exhibited either a co-solvent (salting-in) effect or an anti-solvent one. This behaviour is very interesting both from the fundamental and the applications point of view.

► The work improves comprehension of complex nicotine (aqueous) solutions.
► Promotion of possible sustainable, ionic-liquid based tunable solvents for nicotine.
► Cheap salts, NaCl and Na3PO4, trigger strong demixing in nicotine aqueous solutions.
► Very small quantities of NaCl and Na3PO4 required for demixing in aqueous nicotine.
► Ionic liquid ECOENG 212® is both co- and anti-solvent in aqueous nicotine solutions.