Liquid purification or separation – Processes – Chemical treatment
Reexamination Certificate
1998-12-11
2001-04-10
Barry, Chester T. (Department: 1724)
Liquid purification or separation
Processes
Chemical treatment
C210S755000, C210S756000
Reexamination Certificate
active
06214241
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method of treating an effluent containing sorbic acid and/or its salt from a sorbic acid (inclusive of its salt) production line, a method of reducing the BOD of said effluent, and an effluent disposal device for use in the treatment of said effluent.
BACKGROUND OF THE INVENTION
Sorbic acid and its salts (e.g. potassium salt) are antifungal and effective in preserving food so that they are in broad use as food additives.
The representative commercial technology for the production of sorbic acid or a salt thereof comprises reacting crotonaldehyde with ketene to give a polyester, decomposing the polyester with an acid or alkali to give sorbic acid or a salt thereof in crude form, and purifying the crude sorbic acid or salt by crystallization. This crystallization is generally effected by dissolving said crude sorbic acid or salt in hot water and cooling the solution to cause sorbic acid or its salt to separate out or by dissolving said crude sorbic acid in an aqueous alkaline solution to give an alkali metal sorbate solution and adjusting the solution to pH about 2-3 with an acid such as hydrochloric acid to thereby cause sorbic acid crystals to separate out.
In the above production process, large amounts of effluents containing sorbic acid or its salt are formed in the step of producing crude sorbic acid from said polyester and the subsequent crystallization step. For example, in the step where the polyester is decomposed with hydrochloric acid to give crude sorbic acid, the filtrate after recovery of sorbic acid contains not only organic matter inclusive of sorbic acid and reaction byproducts but also tarry matter so that its BOD (biological oxygen demand) is of the order of tens of thousands to hundreds of thousands parts per million (ppm). Moreover, said organic matter may comprise as many as 50 or more different substances. The filtrate in said crystallization step also contains sorbic acid or its salt and substantially the same amount of other organic matter (about 30-40 kinds of substances) and its BOD is as high as 2000-10000 ppm. Incidentally, the solubility of sorbic acid in water is about 0.1-0.3 weight % at room temperature, although it is increased to about 3 weight % at elevated temperature.
Generally, these effluents are subjected to an activated sludge or other biological treatment and then allowed to drain into a public waterway. However, the effluent from the above sorbic acid production and purification line has such a high BOD value that the load on the biological treatment system is large and therefore, its disposal requires an enormous equipment and running expenditure.
As alternative technologies for the production of sorbic acid, there are known the process which comprises decomposing &ggr;-vinyl-&ggr;-butyrolactone and the process which comprises decomposing acetoxyhexenoic acid which is the reaction product of butadiene with acetic acid. However, in these processes, too, large volumes of effluents containing sorbic acid or its salt are discharged in the production and purification stages, thus presenting the same problems as mentioned above.
Meanwhile, there has been reported a method which comprises acidifying a dilute aqueous solution of sorbic acid or its salt, concentrating it to about 5-fold the initial concentration by the reverse osmosis technique, and recoverying sorbic acid or its salt from said aqueous solution. However, the membrane effluent shows a high BOD value and cannot be directly allowed to drain into a public waterway.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide a method for efficient reduction of the BOD of an effluent containing sorbic acid or its salt.
It is another object to provide a method for efficiently reducing the load on the biological system for the treatment of an effluent containing sorbic acid or its salt.
It is still another object of the invention to provide an effluent disposal device by which the BOD of an effluent containing sorbic acid and/or its salt can be efficiently reduced.
The inventor of the present invention did an intensive investigation for accomplishing the above objects and found that the BOD of an effluent containing sorbic acid and/or its salt can be remarkably reduced by subjecting the effluent to the herein-disclosed specific step(s). The present invention has been developed on the basis of the above finding.
The present invention, therefore, provides a method of treating an effluent containing sorbic acid and/or its salt which comprises a step of treating said effluent with a hypohalogenous acid or a salt thereof. This treatment technology optionally includes a step in which the effluent treated with said hypohalogenous acid or salt is further subjected to a biological treatment.
The present invention further provides a method of treating an effluent containing sorbic acid and/or its salt which comprises a step of subjecting said effluent to membrane separation or to activated carbon treatment, and a step of subjecting the membrane downstream fluid (filtrate) or the activated carbon-treated effluent to biological treatment.
In the above method, the membrane separation may be performed with a nanofiltration membrane. Furthermore, the effluent containing sorbic acid and/or its salt may be adjusted to pH 7 or higher in advance of the membrane separation.
The present invention in another aspect provides a method of reducing the BOD of an effluent containing sorbic acid and/or its salt which comprises (1) treating said effluent with a hypohalogenous acid or a salt thereof, or (2) subjecting said effluent to membrane separation or activated carbon treatment and then to biological treatment.
The invention in still another aspect provides an effluent disposal device comprising a means of treating an effluent containing sorbic acid and/or its salt with a hypohalogenous acid or a salt thereof.
The present invention further provides an effluent disposal device comprising (1) a membrane separation means for separating an effluent containing sorbic acid and/or its salt or a means for treating the effluent with activated carbon, and (2) a biological means for treating the membrane downstream fluid (filtrate) or the activated carbon-treated effluent biologically.
REFERENCES:
patent: 3707770 (1973-01-01), Timmins et al.
patent: 3876536 (1975-04-01), Pradt et al.
patent: 4155975 (1979-05-01), Riley
patent: 4160656 (1979-07-01), Junkermann
patent: 5054434 (1991-10-01), Wax et al.
patent: 0473290A2 (1992-03-01), None
patent: 0473459A2 (1992-03-01), None
patent: 0608200A1 (1994-07-01), None
Chemical Abstracts, vol. 77, No. 14, Oct. 2, 1972, Abstract No. 92558d.
Chemical Abstracts, vol. 76, No. 10, Mar. 6, 1972, Abstract No. 49590a.
Barry Chester T.
Birch & Stewart Kolasch & Birch, LLP
Daicel Chemical Industries Ltd.
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