Liquid purification or separation – Processes – Ion exchange or selective sorption
Patent
1993-11-19
1995-09-19
Cintins, Ivars
Liquid purification or separation
Processes
Ion exchange or selective sorption
210669, 210691, 210694, 210759, C02F 900
Patent
active
054513243
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method of treating liquid effluents containing organic compounds which are required to be destroyed or eliminated before disposing of them through the drains. Liquid effluents is intended to mean all kinds of waste water of industrial origin. This method can be applied very well to liquid photographic effluents in aqueous solution resulting from the processing of films and photographic papers.
There are many works on the treatment of liquid effluents such as color photographic development solutions or baths, the majority using peroxides, hydrogen peroxide or activated carbon. There are also more sophisticated treatment methods in which several reagents are used, separately or together.
In particular a method will be cited which uses a mixture of peroxides and ozone, described in U.S. Pat. No. 4,332,687, and which aims essentially at eliminating heavy metals.
The method in the Swedish Patent SE 7801323 will also be cited, which describes a two-stage treatment, first of all by means of hydrogen peroxide and then by means of activated carbon and/or an ion exchange resin. Instead of hydrogen peroxide, various types of oxidants can be used, alone or in combination, such as chlorine, chlorine dioxide, peroxides or ozone.
Another method will also be cited, described in the published patent application JP 63-039682, in which the effluents originating from photographic processing baths are condensed, and then the condensate is treated with inorganic peroxides in the presence of clay, and then with activated carbon.
Because of the increasing strictness of the standards relating to the disposal of effluents, it is necessary to continue to improve the effluent treatment methods. Moreover, the methods above-mentioned do not normally make it possible to dispose of the effluents thus treated into the environment without any other treatment, unlike the effluents treated by the method according to the invention.
The method according to the invention makes it possible to treat liquid effluents containing organic compounds, such as paraphenylene diamines or hydroquinone derivatives. These effluents are in particular color or black and white photographic developers. The method according to the invention also makes it possible to treat other organic compounds forming part of photographic film and paper processing solutions.
This method comprises the stages consisting of: oxidising action at a pH of between 6 and 9; and agent.
The resulting liquid, after separation of the absorbent, is sufficiently purified to be discharged directly into the environment.
It will be understood that the method according to the invention consists of three principal stages, first of all a primary oxidation in an alkaline medium, then a secondary oxidation in a neutral medium and finally a subsequent absorption treatment.
The primary oxidation is carried out in a strongly alkaline medium (pH.gtoreq.10), advantageously at a pH of between 11 and 13, and aims to break up the organic molecules present into smaller entities.
The quantity and concentration of the hydrogen peroxide can vary to a great extent and are chosen according to the COD (chemical oxygen demand) of the solution to be treated and the degree of destruction desired. In practice, the quantity of oxygen contributed by the hydrogen peroxide expressed in grams per liter is between 0.5 and 3 times the COD of the bath to be treated expressed in grams per liter.
The neutralisation of the reaction product can be carried out, for example, with an acid such as phosphoric acid, prior to the secondary oxidation or along with it, by adding a quantity of acid sufficient to obtain a pH of between 9 and 6. In other words, stages (b) and (c) of the method can be merged.
As a reagent for the secondary oxidation, a peroxy compound can be used, for example peroxyacids or their salts, such as permonosulphuric acid, a permonosulphate, a perdisulphate or peracetic acid. Naturally, this peroxy compound must be a colorless product, active at a neutral pH and not comprising any
REFERENCES:
patent: 3655343 (1972-04-01), Galeano
patent: 3767572 (1973-10-01), Bober et al.
patent: 4332687 (1982-06-01), Daignault et al.
patent: 4416786 (1983-11-01), Knorre et al.
Caillault Oliver A. G.
Gehin Guy M.
Cintins Ivars
Eastman Kodak Company
Everett John R.
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