Ionic liquid-based three phase partitioning (ILTPP) is a promising technique to recover lactoferrin, a high-added value whey protein, because it combines the advantages associated with the use of ionic liquids and the feasibility of the product recovery characteristic of three phase partitioning. The recyclability of the ionic liquid is essential for the feasibility and development of ILTPP technique, due to the high cost and environmental impact associated with the discharge of this type of compounds. For this purpose, the thermodynamic characterization of the systems of interest for ILTPP, which are based on the use of 1-butyl-3-methylimidazolium trifluoromethanesulfonate (BmimTfO) and sodium dihydrogenophosphate (NaH2PO4), is here performed to determine the composition of the liquid phases in equilibrium and the distribution coefficient between them. In addition, the fraction of ionic liquid that cannot be reused in the ILTPP process has been assessed, concluding that the recyclability of this compound is highly dependent on the protein concentration in the feed stream. At high protein concentrations (2 g L-1) and moderate ILTPP efficiencies (around 80%) it is possible to recycle more than 99% of the ionic liquid, which improves both the economic and environmental performance of the ILTPP process. (C) 2014 Elsevier BM. All rights reserved.