Common ion effect to assist lm separation

Abstract

The instant invention relates to an improvement in the liquid membrane process for removing soluble materials from solution. More specifically, in a process wherein soluble materials are removed from solution by contacting said solution with an emulsion, the external phase of which is immiscible with said solution and permeable to said soluble materials and the internal phase contains a reactant which reacts with said soluble material and converts said soluble material to a material which is insoluble and thus trapped in the internal phase, the improvement which comprises maintaining the concentration of said reactant in the internal phase of the emulsion at a level at which the concentration of said soluble material in the internal phase of the emulsion is less than the concentration to which it is desirable to lower said soluble material in said solution. Preferably the solution is aqueous and said soluble material is a salt. In a preferred embodiment of the instant invention the concentration of fluoride ion in an aqueous solution is lowered to less than 6 ppm by contacting said solution with an emulsion containing a soluble calcium salt in the internal phase. The concentration of calcium in said internal phase is maintained at a level sufficient to provide a concentration of less than 6 ppm soluble fluoride ion in said internal phase.