Multi-stage extraction process

A process for multi-stage extraction in an apparatus comprising a multiplicity of separating stages connected in series, wherein each said separating stage comprises an extraction and a reextraction chamber, and wherein a raffinate phase containing a substance is brought into contract with an extractant in the extraction chamber to extract said substance and the extractant is brought into contact with an extract phase in the reextraction chamber to reextract said substance, wherein the extractant is a continuous phase and the raffinate and extract are dispersed phases, the extractant is conveyed in cross-flow to the extract and raffinate phases within the same separating stage in each case, the raffinate and extract phases are conveyed through some or all of the separating stages in counter-current flow and

• a. said raffinate phase is a first liquid having a first density and said extractant phase is a second liquid having a second density, wherein said first density is greater than or less than said second density, and
• b. said extract phase is a third liquid having a third density, wherein said third density is less than said second density if said first density is greater than said second density, and wherein said third density is greater than said second density if said first density is less than said second density, so that a circulating flow of the extractant is maintained between the extraction and reextraction chambers solely due to the density differences of the dispersed phases in relation to the continuous phase.