Liquid purification or separation – Processes – Liquid/liquid solvent or colloidal extraction or diffusing...
Patent
1992-03-27
1994-01-04
Spear, Frank
Liquid purification or separation
Processes
Liquid/liquid solvent or colloidal extraction or diffusing...
210644, B01D 6124
Patent
active
052757366
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to the production of pure elemental iodine.
BACKGROUND ART
Iodine (for example in the form of Lugol's solution or tincture of iodine) has long been recognized as an effective biocide. U.S. Pharmacopoeia and other similar publications in many countries have documented this property of iodine since 1830. Iodophores have been noted for their similar properties since 1960.
These iodines have been recognized for their bioactivity in man, animals, and in types of bacteria in plants and their seeds. In fact, a deficiency of iodine has been shown to prevent the attainment of maximum health, growth, and reproductive success.
It has been recently shown that the active component in all biocidal iodines is thermodynamically free iodine, which is uncomplexed or pure elemental iodine (I.sub.2), as described in the Schmidt and Winicov article "Detergent/Iodine Systems" in Soap and Chemical Specialties, August 1967. It has also been recently shown that thermodynamically free iodine when fed to a mammal has a much decreased effect upon the thyroid compared to iodide, or iodine/iodide mixtures or mixtures of polyhalides (see Thrall and Bull in their article "Differences in the Distribution of Iodine and Iodide in the Sprague--Dawley Rat" in Fundamental and Applied Toxicology, 15, 75-81 (1990)).
The term thermodynamically free iodine describes iodine that is free from complexing. Thermodynamically free iodine in aqueous solution may dissociate into many hydrolyzed forms, depending upon concentration and/or pH, for example HIO (or also known as HOI), some of which are biocidal in nature. If a solution of aqueous iodine (I.sub.2 +hydrolyzed biocidal forms where appropriate) could be reliably generated at any concentration of thermodynamically free iodine less than supersaturation, and remain stable at that level, it would allow the manufacture of many devices useful in water treatment, instrument sterilization, use as a source of nutritional iodine, plus other medicinal uses including the treatment of IDDs (Iodine Deficiency Disorders), chemical uses, and catalytic uses. For example, if a device could reliably produce a desired concentration of thermodynamically free iodine into a pH buffered fluid such that the thermodynamically free iodine remained unhydrolyzed and of known concentration despite moderate changes in ambient temperature, it would allow the treatment of many non-thyroidal IDDs and other medical conditions known to respond to treatment with iodine, such as in U.S. Pat. No. 4,816,255 of Ghent, with a much reduced toxicity (toxicity meaning thyroid complication found with other forms of iodine, iodides, iodine/iodide mixtures or polyhalides).
In an effort to produce biocidal iodine compounds, many methods, both chemical and mechanical in nature, have been devised. To date, however, these methods have had limited use and commercial success for reasons attributable to iodine's chemical and physical properties such as low solubility in H.sub.2 O, reactivity, easy contamination or the production of poly-halides and iodides and other potentially noxious adjuvants which inhibit the presence of thermodynamically free iodine, or its use in some applications.
Thermodynamically free iodine in all biocidal iodine solutions, whether alcohol/water, surfactant/water or other complexing agent/water, is confined to the water phase. Further, thermodynamically free iodine is usually found in solution in concentrations less than that of the total titratable iodine of the solution. For example, Lugol's solution, where potassium iodide (KI) is used to create a reservoir of iodine as I.sub.3.sup.- through the relationship I.sub.2 +nI.sup.- I-+I.sub.n, the solubility of elemental iodine is, increased to, for example, 1% (w/v); however, the amount of thermodynamically free iodine detectable is only circa 0.018% (w/v) or 180 ppm.
The germicidal capacity of these iodine formulations is dependent upon the continued release of thermodynamically free iodine from the reservoir of titratable iodine, as
REFERENCES:
patent: 2984623 (1961-05-01), Lee
patent: 3028299 (1962-04-01), Winicov et al.
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patent: 4296205 (1981-10-01), Verma
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patent: 4555347 (1985-11-01), O'Dowd et al.
patent: 4769143 (1988-09-01), Deutch et al.
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patent: 4996048 (1991-02-01), Bhagwat et al.
Thrall and Bull-"Differences in the Distribution of Iodine and Iodide in the Sprague-Dawley Rat"-Fundamental and Applied Toxiology, 15, 75-81 (1990).
Schmidt and Winicov-"Detergent/Iodine Systems"-Soap and Chemical Specialties", Aug. 1967.
Iomech Limited
Spear Frank
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