Extraction of metal ions in aqueous polyethylene glycol–inorganic salt two-phase systems in the presence of inorganic extractants: Correlation between extraction behaviour and stability constants of extracted species

The use of aqueous polyethylene glycol–inorganic salt two-phase systems for the extraction of metal ions has a great potential due to their durability, non-toxicity and relative low cost. The aqueous phases can be easily separated by centrifugation, and the operation is possible in a range of experimental conditions. The experimental results have shown that for a given aqueous two-phase system, the extraction behaviour of metal ions in presence of inorganic extractants is mainly dependent on the stability of extracted species. In this paper we review our results obtained at metal ion extraction using inorganic extractants and discuss three major types of extraction behaviours.