Purification utilizing liquid membrane with electrostatic coalescence
AssigneeDavy International (Oil & Chemicals) Limited
InventorGraham A. Davies
Life of this patent
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Abstract
A liquid membrane technique is disclosed for recovery of dissolved species from aqueous solutions thereof in which, by appropriate tailoring of the emulsion, electrostatic precipitation can be used successfully in the recovery of the species from the interior phase of the emulsion. The emulsion is so prepared that the droplet size of the interior phase of the emulsion is in the range of from about 0.3 micrometers to about 10 micrometers, with the majority of the droplets lying in the range of from about 0.8 micrometers to about 3 micrometers. The electrostatic field is preferably at least 1 kilovolt per centimeter up to 7.5 kilovolts per centimeter or more.
Claims20
In a liquid membrane process for the recovery of a dissolved species from an aqueous solution thereof which comprises:
- providing an emulsion comprising droplets of an aqueous interior phase surrounded by a hydrophobic exterior phase which is immiscible with the aqueous solution, which is permeable to said species, and which contains a non-ionic oil-soluble surfactant, the aqueous interior phase comprising a component capable of rendering said species non-permeable;
- mixing the aqueous solution with the emulsion thereby to effect intimate contact therebetween and to permit said species to permeate the exterior phase, to desorb from the exterior phase into the interior phase, and to be rendered non-permeable in the interior phase;
- separating the emulsion from the aqueous solution now depleted in said species;
- breaking the separated emulsion thereby to effect coalescence of the aqueous interior phase;
- and
- recovering coalesced interior phase containing said species,
- the improvement comprising:
- forming the emulsion by emulsifying the aqueous interior phase in the hydrophobic exterior phase under controlled shear conditions so as to produce droplets of interior phase in the hydrophobic exterior phase substantially all of a size lying in the range of from about 0.3 to about 10 micrometers with the majority of the droplets distributed over the range of from about 0.8 to about 3 micrometers;
- and
- breaking the separated emulsion by subjection to an electrostatic field.
In a continuous process for the recovery of a dissolved species from an aqueous feed solution thereof which comprises:
- supplying to an emulsification zone a hydrophobic exterior phase which is immiscible with the aqueous solution, which contains an oil-soluble surfactant and a hydrophobic organic solvent, and which is permeable to said species, and an aqueous interior phase which comprises a component adapted to promote the desorption of said species from the exterior phase into the interior phase;
- mixing the interior and exterior phases in said emulsification zone so as to form therein a water-in-oil type emulsion;
- contacting the aqueous solution with the water-in-oil type emulsion in a contact zone so as to permit said species to permeate the exterior phase, to desorb from the exterior phase into the interior phase and to be rendered non-permeable in the interior phase;
- separating emulsion from the aqueous solution in a separation zone, the aqueous solution now being depleted in said species;
- breaking separated emulsion in an emulsion breaking zone;
- recovering from the emulsion breaking zone oil-soluble surfactant and solvent, as well as coalesced interior phase containing said species;
- and
- recycling oil-soluble surfactant and solvent to the emulsification zone;
- the improvement comprising:
- effecting said mixing step under controlled shear conditions so as to form in said emulsification zone a water-in-oil type emulsion having an interior phase droplet size in the range of from about 0.3 micrometers up to about 10 micrometers with the majority of the droplets distribute over the range of from about 0.8 to about 3 micrometers;
- passing separated emulsion from the separation zone to an electrostatic coalescence zone in which an electrostatic field is maintained so as to effect coalescence of droplets of the interior phase;
- recovering from the electrostatic coalescence zone exterior phase and coalesced interior phase containing said species;
- and
- recycling exterior phase to the emulsification zone.
Dependencies are inferred from the claim text.