Liquid purification or separation – Processes – Liquid/liquid solvent or colloidal extraction or diffusing...
Patent
1999-07-02
2000-02-15
Therkorn, Ernest G.
Liquid purification or separation
Processes
Liquid/liquid solvent or colloidal extraction or diffusing...
656679, 656691, B01D 1508
Patent
active
060248793
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The invention relates to a process for the purification of water with a view to the separation therefrom of organic substances, particularly malodorous substances.
It more particularly applies to the elimination of natural pollutants constituted by (-)geosmine and (+)2-methyl-isoborneol.
These pollutants are organic substances produced by bioconversion of organic matter and are known as being natural pollutants of drinking water. In water reprocessing plants, these are the main olfactory pollutants contributing to a significant extent to the smell and taste of fusty soil in polluted water. These substances comply with the following formulas: ##STR2## (-)geosmine and (+)2-methyl-isoborneol are detected by human smell with a very small dose. For example, geosmine is detected in air at a rate of 0.1 ppb.
PRIOR ART
Numerous methods have been tested for eliminating these two pollutants, which are often only present in doses around 130 to 180 ng/l.
The tested methods make use of adsorption procedures, e.g. of activated carbon, lipid membrane, zeolite or divinyl benzene-styrene copolymer, filtration procedures on sand or gravel, decomposition processes by oxidation by means of ozone and/or hydrogen peroxide, or elimination by microorganisms.
Hitherto, none of the said methods, used alone, has been completely satisfactory. Recently consideration has been given to combining several procedures for eliminating these pollutants.
Thus, Koizumi et al described in Zosui Gijutsu, 18 (1), 56-60, 1992: Chemical abstract 117 (20), No. 198092 g, a process for completely eliminating 2-methyl-isoborneol from water by oxidation by means of ozone and adsorption of the oxidation products by activated carbon.
Vik et al described in Water Sci. Technol., 20 (8-9), pp 229-36, 1988: Chemical abstract 110 (10), No. 82177q, a process for eliminating geosmine and 2-methyl-isoborneol from water by oxidation by means of ozone, followed by adsorption on activated carbon.
Destailleur et al in J. Fr. Hydrol., 22 (2), pp 225-34, 1991: Chemical abstract 118 (6), No. 45353p, described a process for eliminating geosmine from water by oxidation by means of ozone and hydrogen peroxide.
DESCRIPTION OF THE INVENTION
The present invention relates to a process for purifying water making it possible to eliminate malodorous organic substances, such as geosmine and 2-methyl-isoborneol, by a different method, which is easy to put into operation and very effective, which uses a cyclodextrin able to form an inclusion complex with these substances.
Cyclodextrins or cyclomaltooligosaccharides are compounds having a natural origin formed by the linkage of .alpha.-1,4-bonded glucose units. Numerous works have shown that these compounds could form inclusion complexes with hydrophobic molecules, thus permitting their solubilization in aqueous media. Numerous applications have been developed in order to take advantage of this phenomenon, especially in the pharmaceutical field. Thus, JP-A-62/123196, proposes the use of the dimethyl derivative of .beta.-cyclodextrin for solubilizing prednisolone. WO-A-91/04026 proposes using the dimethyl derivative of .beta.-cyclodextrin for solubilizing pharmaceutical agents such as Amiodarone, Melphalam and Naproxen.
However, the use of cyclodextrins for trapping pollutants and purifying water has never been envisaged.
According to the invention, the water purification process for separating from water at least one organic substance comprises the stages consisting of: ##STR3## in which R.sup.1 represents a C.sub.1 to C.sub.12 alkyl group or the acetyl group CH.sub.3 CO--, R.sup.2 and R.sup.3 which can be the same or different, represent H or R.sup.1, R.sup.2 and/or R.sup.3 can differ from the other R.sup.2 and R.sup.3 in at least one glucose unit of the cyclodextrin, and n=5, 6 or 7 for including therein the organic substance or substances to be separated and
The cyclodextrin of formula (I) used in the invention for the purification of water can either be a disubstituted derivative (R.sup.3 =H) of natural cycl
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Baudin Cecile
Gosselin Pascal
Perly Bruno
Commissariat a l''Energie Atomique
Therkorn Ernest G.
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