Method for counter-current liquid-liquid extraction in a sub-millimetre conduit

A method for counter-current liquid-liquid extraction in a sub-millimetre conduit, the method being implemented from an initial stream of liquid drops in the conduit, said stream comprising alternating drops of a first liquid and drops of a second liquid less wetting than the first liquid and immiscible with the first liquid, one of the two liquids comprising a component to be extracted towards the other of the two liquids;

• the method comprising the following steps:
• a) applying a first pressure gradient along the conduit with a pressure difference sufficiently large to generate a visco-inertial flow displacing a first volume of drop stream according to said first gradient and generating a film of first liquid displaced along an opposite orientation to said first gradient, the film being located between the drops of second liquid and the conduit;
• b) stopping the application of the first pressure gradient;
• c) applying a second pressure gradient along the conduit, in the opposite orientation to the first pressure gradient applied in the step a) and lower, in absolute value, than the first pressure gradient applied during the step a) to generate a viscous-capillary flow displacing a second volume of drop stream according to said second gradient;
• and
• d) stopping the application of the second pressure gradient.