A method and an apparatus for the extraction of a solute from an aqueous feed solution into an aqueous stripping solution are described. The apparatus comprises vessel means for containing a continuous non-polar carrier liquid, the carrier liquid having therein a chemical having an affinity for ions of at least one species in said solute in said feed solution; means for providing at least one stream of each of said feed (42) and stripping solutions (46) through said carrier liquid in said vessel means; electrode means (30, 32, 34, 36) for applying a first and a second high voltage electrostatic field to each of said feed and stripping solution streams respectively, so as to cause said streams to break up into a multiplicity of small droplets; baffle means (26) positioned between the electrode means for establishing said first and second high voltage electrostatic fields, said baffle means allowing the movement of said carrier liquid but minimizing transfer across the baffle of feed and stripping solutions; mutually separate receiving means for collecting said feed and stripping solutions after they have passed through said first and second high voltage electrostatic fields, respectively; the apparatus being characterized by further including means for providing and controlling the first (100) and second high voltage electrostatic fields (102) such that the first and second voltages are different and controllable.
The present invention is directed to an improved process for the recovery of metal ions from metal-containing aqueous solutions using a supported liquid membrane (SLM) whereby the pH of the metal-containing solution is preferably adjusted to between 5.5 and 8 and ammonia or other weak base is present in the metal-containing solution in a concentration sufficient to form a complex between the weak base and metal ions present in the solution. The present invention permits enhanced recovery of metal in the solution without any need to adjust the pH of the solution during the SLM process.
