Selective recuperation of copper by supported liquid membrane (SLM) extraction

In the first stage, a comparison of described and commercialised copper extractants and diluents was made by means of conventional extractions. The investigated criteria were: the distribution ratio, the kinetics and the selectivity of copper extraction and stripping. A salicylaldoxime dissolved in kerosene, LIX 860 is giving the best distribution ratio, with a fast extraction and a very fast and complete stripping with sulphuric acid 300 g/l. Below pH 2.5, the selectivity for copper is high (only Fe3+ was partially co-extracted). However, Acorga M 5640 provides the highest selectivity. In the second stage, experimental studies on the Lifetime of several supporting membranes as well as on the stability of the supported liquid membrane showed that Celgard (C) X10-240 has the smallest pore size and provide the highest stability. At least, the working parameters, investigated in a pilot scale continuous SLM extraction, show a permeability coefficient, varying between 1 and 7.10(-2) m h(-1). It is not influenced by the flow velocity and is dependent, not only on LIX-860 concentration and pH, but also on the copper feed concentration. Moreover, the three parameters are interacting. After a working time of 500 h, the permeability had fallen to 40% of its start value. (C) 1998 Elsevier Science B.V.