ABSTRACT
Reactive solvent extraction makes use of specific chemical reactions in order to
promote or achieve a separation task. Commercially available liquid ion exchangers are
widely used in that respect. The nature of the chemistry starts with Van der Waals’
interactions, covalent or ionic binding which may be supported by steric effects.
Additional effects can result from solvents and cosolvents (modifiers) and surfactants
present in the system. After a short introduction into the chemistry the focus of this
chapter will be on reactive equilibria and mass transfer and its impact on the
performance of extraction columns and their current applications. The first extraction processes were with solid extraction in the extraction of
perfumes, waxes, pharmaceutical active oils in an operation quite similar to a modern
Soxhlet apparatus. An extraction pot with an age of about 3500 BC was found 250
km north of Baghdad (see Fig. 1) and extraction instructions were documented by a
Sumerian text of 2100 BC [1]. The next major improvements were in the medieval
age with new solvents like ethanol, mineral acids, and amalgams used to extract and
purify metals. The first extraction of a metal was reported by Peligot [2] who used
diethylether to extract uranyl nitrate which gave a basis to uranium extraction within the ‘‘Manhattan’’ project in the 1940s [3]. Reactive solvent extraction was then a
niche for pyrometallurgically difficult-to-separate metals (Nb/Ta, Zr/Hf) until the
1960s when there was a breakthrough with copper extraction. LIX (liquid ion ex-
changer) chemicals [4] were size-selective extractants for separation of copper from
iron which allowed copper recovery from low-grade ores after a sulfate-leaching pro-
cess. Meanwhile the use of liquid ion exchangers has expanded to a large array of ions
and neutral solutes in hydrometallurgical, environmental, petrochemical, chemical,
and biochemical applications [5-9].
