THE PRECIPITATION OF SOLIDS IN A LIQUID MEMBRANE EMULSION - THE CONTROL OF PARTICLE-SIZE

The precipitation of a solid from a solution generally involves several steps, viz., the purification of the solution, reaction and precipitation, separation, drying, comminution and classification of the solid. In this work, we consider the precipitation of a salt, copper oxalate, for which we have developed a process whereby separation of a desired cation, Cu2+ from a solution takes place by selective mass transfer through a membrane film. A chemical reaction and precipitation in a confined environment is carried out so that the resulting particle size of the precipitate can be controlled within the range 0.1-7-mu-m and particularly from 0.1-2.0-mu-m. The process, based on extraction using a liquid surfactant membrane with precipitation of the solid in the internal phase of the emulsion membrane, effectively eliminates the need for solution pretreatment to remove competing ions and most importantly will eliminate the need for further size modification of the precipitate.