US3909403A

US3909403A - Process of treating waste water

Info

Publication number: US3909403A
Application number: US407760A
Authority: US
Inventors: Akira Abe; Yoshio Usui
Original assignee: Fuji Photo Film Co Ltd
Current assignee: Fujifilm Holdings Corp
Priority date: 1972-10-23
Filing date: 1973-10-18
Publication date: 1975-09-30
Anticipated expiration: 1992-09-30
Also published as: JPS5143312B2; BR7308276D0; JPS4964251A

Abstract

In a process of removing ferricyanide ions and/or ferrocyanide ions from a waste solution or water containing these ions formed in photographic processings by bringing the waste solution in contact with a weakly-basic anion-exchange resin to absorb the ferricyanide ions and/or ferrocyanide ions on the anion-exchange resin, an alkaline concentrate of the ferricyanide ions and/or ferrocyanide ions is formed by immersing the weakly-basic anionexchange resin having absorbed thereon the ions and after adding to the concentrate a strong alkali, a hypochlorite, and bromide ions to increase the pH of the concentrate to above 12, the mixture is heated to temperatures over 50*C at normal pressure, whereby the ferricyanide ion and/or ferrocyanide ions are decomposed.

Description

United States Patent [1 1 Abe et al.

[ 1 Sept. 30, 1975 PROCESS OF TREATING WASTE WATER [75] Inventors: Akira Abe; Yoshio Usui, both of Tokyo, Japan [22] Filed: Oct. 18, 1973 [2]] Appl. N0.: 407,760

[30] Foreign Application Priority Data Oct. 23, 1972 Japan 47-l06060 [52] US. Cl 210/32; 96/60 BF; 210/37 [51] Int. Cl. B01D 15/04; BOlD 15/06 [58] Field of Search 96/50 R, 60 R, 60 BF, 92; 210/24, 30, 32, 37; 423/22; 75/101 BE ['56] References Cited UNITED STATES PATENTS 2,515,930 7/1950 Seary 6/60 R 2,61 L699 9/1952 Zappert, 96/60 R 2,61 L700 9/l952 Brunner, Jr. et al.... 96/60'R 2,944,895 7/l960 West et al. 961/60 R 3,001,868 9/l96l Aveston ct a1 423/22 OTHER PUBLICATIONS Chemical Abstracts: 72:59556a; 69:80027b;

Primary ExaminerSamih N. Zaharna Assistant Examiner-Robert H. Spitzer Attorney, Agent, or FirmSughrue, Rothwell, Mion, Zinn & Macpeak [57] ABSTRACT In a process of removing ferricyanide ions and/or fcrrocyanide ions from a waste solution or water containing these ions formed in photographic processings by bringing the waste solution in Contact with a weaklybasie anion-exchange resin to absorb the ferricyanide ions and/or ferrocyanide ions on the anion-exchange resin, an alkaline concentrate of the tcrricyanide ions and/or ferrocyanide ions is formed by immersing the weakly-basic anion-exchange resin having absorbed thereon the ions and after adding to the concentrate a strong alkali, a hypochlorite, and bromide ions to increase the pH of the concentrate to above 12, the mixture is heated to temperatures over 50C at normal pressure, whereby the ferricyanide ion and/or ferrocyanide ions are decomposed.

19 Claims, N0 Drawings PROCESS OF TREATING WASTE WATER BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process of treating waste water containing ferricyanide ions and/or ferrocyanide ions. More particularly, the. invention relates to a process of treating waste water containing ferricyanide ions and/or ferrocyanide ions from photographic processings. 1

The explanation of the invention given hereinafter is with respect to the treatment of waste water in photographic processings as a specific example but. it will be easily understood that the subject of thisinvention is not limited to the photographic case only and the in? vention can be widely applied to general industrial waste solutions containing ferricyanideions and/or fer.-

rocyanide ions, such as a waste solution in galvanizing or printing and a waste solution used for the syntheses of dyes, pigments, etc., as an oxidizing agent. I

2. Description of the Prior Art The processing steps for photographic materials include frequently a bleach step. The bleach step is a step in which a metal such as silver formed by development is converted into silver ions using an oxidizing agent and the bleach step is included usually in the processings of silver halide color photographic materials on photographic materials for the silver dye bleach method as well as in the reduction processings of photographic materials for making printing plates.

The reduction operation as described above is the step of oxidizing the metallic silver formed by development into silver ions and dissolving the silver ions. Thus, the reduction operation is conducted, when the image density of a photographic material becomes higher than an appropriate value after developrnent caused by excessive light exposure, to reduce the image density to the appropriate range oris conducted to control the properties of the dot imagesof a photographic printing plate formed by developing .a photographic material for making .a printing plate. 5

As a reducer used for the reductionv step, Farmers reducer consisting of a solution containing a ferricya-v nide and a thiosulfate has widely been used. Although a permanganate oratpersulfate can also be used for the reducer as anotheroxidizing agent than the ferricyanide, the Farmers reducer containing the ferricyanide and the thiosulfate ismost excellent due to its-usable oxidation-reduction actions of them and hence the fa-'- tigued reducer must be dischargd.- Also, since the reducer is used in such a manner that a printing plate is,

after being wetted well with water, immersedin the reducer, withdrawn from the reducer, and then washed.

with water orthat the reduceris applied onto the surface ofa printing plate while washingthe surface of the I printing plate continuously with water, thus the reducer is contained in the washing water. Consequently, the waste water from the reduction step contains ferricyanide ions and/or ferrocyanide ions, which are there duction products of the ferricyanide ions, together with I the thiosulfate. l

The ferricyanide ions and/or the ferrocyanide ions are quite stable complex ions having almost no toxicity but it is known that when'those ions are subjected to photochemical oxidation, they are decomposed to form toxic free cyanides (see, e.-g:., Yu Yiu Lurc and V. A. Panova; Behavior of Cyano Compounds in Water Ponds, Gidrokhim; Materialy, 31133-143 (1964), and George Edgar and Morris Lipschuets; Toxicity of Ferroand Ferricyanide Solutions to Fish and Determination of the Cause of Mortality, Trans. Am. Fish $00., 78,192 (1948)).

According to the present discharge standards into rivers, theallowable limit in Japan for the amount of cyanide is one ppm. The ferricyanide ions and/or ferrocyanide ions have the latent toxicity as described above and hence the aforesaid standard is as a matter of course applied to those ions as well. Therefore, it is necessaray to take some counteraction in the case of discharging waste water containing those ions.

The concentration of the ferricyanide ions and/or ferrocyanide ions in the waste water from the reduction step using Farmers reducer is fairly low because a large amount of water is used for washing in the reduction step but the concentration is nevertheless higher than the discharge standard as indicated above: Furthermore, sincelfree cyanide formed by the photochemical decomposition of ferricyanide ions and/or ferrocyanide ions is quite high in toxicity as mentioned above, the ferricyanide ions and/or ferrocyanide ions present even in a considerably low concentration must be removed.

As the processes of removing those ferricyanide ions and/or ferrocyanide ions from wastesolutions containing them, there are known a process of removing them by precipitation utilizing the reaction thereof and iron salt, an electrodialysis process, a reverse osmosis process, a combustion process, a pyrolysis process, and an ion exchange process.

The process of removing ferricyanide ions and/or ferrocyanide ions by precipitation as the result of the reaction with an iron salt utilizes the phenomenon of the formation by these ions of Prussian Blue by the reaction with iron salt ions (see, Japanese Pat. application However, this process has the disadvantage that a long time is required to precipitate the particles of Prussian Blue since the particles are very fine and, in particular, when the waste solution to 'be treated is low in concentration and contains a large amount of water such as the waste water from the reduction step or waste water of the reducer, the process requires equipment with a large capacity. This process has further the disadvantage that since the precipitates formed contain ferricyanide and/or ferrocyanide, they may not be discharged as they are and hence must be treated further.

Electrodialysis and reverse osmosis may be effective processes for treating waste water containing ferricyaamount of water such as the waste water from the reduction step,-'-a" verylargeequipment is requiredand hence the cost for the equipment is quite high.

The combustion process is a process of evaporating water and decomposing the residue unde'r'heating to a high temperature by means of a heavy oil. burner, etc.

However, in order to apply this process to the waste reducer solution containing ferricyanide ions and/or ferrocyanide ions, a quite large amount of heat is necessary due to the large water content. Also, ferricyanide ions damage the combustion furnace due to their strong oxidative power and further if the temperature in the combustion furnace is lowered, undecomposed cyanide is discharged in the combustion products. Moreover, since the waste reducer solution contains a thiosulfate, sulfur dioxide gas is generated on combustion, which causes air pollution.

The pyrolysis process is a process wherein a strong alkali is added to the solution containing the ferricyanide ions and/or ferrocyanide ions to adjust the pH of the solution over 12 and after heating the solution to temperatures over 50C at normal pressure, a hypochlorite is added thereto to decompose by oxidation the ferricyanide ions and/or the ferrocyanide ions contained in the solution (Japanese Pat. application No. 50,932/1971).

In this process the ferricyanide ions and/or ferrocyanide ions are decomposed into iron oxide, carbon dioxide, carbonate, nitrogen and ammonia. The advantage of this process is that, in contrast to the process of pre cipitating or concentrating ferricyanide ions and/or ferrocyanide ions, such as the process of precipitating utilizing the reaction with an iron salt, a reverse osmosis process, and an electrodialysis process, the ferricyanide ions and/or ferrocyanide ions are completely decomposed into innocuous components and hence this process is a complete final treatment eliminating the necessity of further treatment.

However, since the waste reducer solution contains a large amount of water, the process requires also a large amount' of heat and large scale equipment as in the case of the combustion process. Furthermore, since the waste reducer solution contains a thiosulfate, the hypochlorite added to decompose by oxidation the ferricyanide ions and/or ferrocyanide ions is readily reduced by the thiosulfate thereby losing its oxidative power.

Therefore, the treatment of ferricyanide ions and/or ferrocyanide ions in a waste solution containing these ions in low concentration by the aforesaid pyrolysis process is a quite expensive.

As an economical process of treating waste water containing ferricyanide ions and/or ferrocyanide ions in low concentration, a process of treating the waste solution using a weakly-basic anion-exchange resin (see, Japanese Pat. Publication Nos. 92,1 15/1971, 22,907/1972, and 52,267/1972, and US. Pat. application, Ser. No. 307,265, filed Nov. 16, 1972) has been proposed. This process is quite profitable as compared to other processes as indicated above in the case of recovering ferricyanide ions and/or ferrocyanide ions as a concentrate from a large volume of waste water containing these ions in low concentration.

However, the ferricyanide ions and/or ferrocyanide ions treated by this ion-exchange process are still in the form of ferricyanide and/or ferrocyanide ions and thus the problem of pollution occurs in discharging such residues. Namely, the ionexchange process has the disadvantage that it is not a complete final treatment for the waste solution.

SUMMARY OF THE INVENTION An object of this invention is, therefore, to provide an economical and complete treatment process for removing efficiently ferricyanide ions and/or ferrocyanide ions from waste water or a solution containing the ferricyanide ions and/or ferrocyanide ions together with thiosulfate ions in an innocuous dischargeable form.

This invention provides a process of treating waste water containing ferricyanide ions and/or ferrocyanide ions which comprises bringing the waste water containing these ions in contact with a weakly-basic anionexchange resin, removing the weakly-basic anionexchange resin having adsorbed thereon the ions from the waste water, immersing the weakly-basic anionexchange resin having the ions adsorbed thereon in an alkaline solution to provide an alkaline concentrated solution of the ions, adding to the concentrated solution a strong alkali, a hypochlorite, and bromide ions to adjust the pH of the solution to above 12, and heating the mixture to temperatures above C at normal pressure, whereby the ferricyanide ions and/or the ferrocyanide ions are decomposed.

According to another embodiment of this invention there is further provided a process of treating waste water containing ferricyanide ions and/or ferrocyanide ions which comprise bringing the waste water contain ing the ions in contact with a weakly basic anionexchange resin in the presence of at least one of borate ions, a weak acid, and a weak acid salt, removing the weakly-basic anion-exchange resin having adsorbed thereon the ions from the waste water, immersing the weakly-basic anion-exchange resin having the ions adsorbed thereon in an alkaline solution to provide an alkaline concentrated solution of the ions, adding to this solution a strong alkali, a hypochlorite, and bromide ions to adjust the pH of the solution to above 12, and heating the mixture to temperatures above 50C, whereby the ferricyanide ions and/or the ferrocyanide ions are decomposed.

DETAILED DESCRIPTION OF THE INVENTION It has already been discovered that when waste water containing ferricyanide ions and/orferrocyanide ions together with thiosulfate ions is treated with a weaklybasic anion-exchange resin, the thiosulfate ions are not adsorbed but the ferricyanide ions and/or ferrocyanide ions only are selectively adsorbed by the resin with good efficiency as described in the specification of Japanese Pat. application No. 92,115/1971.

The inventors have further investigated the pyrolysis of ferricyanide ions and/or the ferrocyanide ions and have discovered that the presence of bromide ions is necessary for completely decomposing the ferricyanide ions and/or ferrocyanide ions into innocuous materials. Namely, the inventors have conducted the pyrolysis of a solution containing ferricyanide ions and/or ferrocyanide ions for investigating the pyrolysis of waste reducer solution and have confirmed that l to 10% by weight of the ferricyanide ions and/or ferrocyanide ions always remain in the treated solution, in other words, the decomposition reaction in the pyrolysis is not complete. Thus, the inventors have also investigated the influence of various materials on the pyrolysis when they are present in the pyrolysis system and as the results thereof, have discovered that ferricyanide ions and/or ferrocyanide ions are completely decomposed by the pyrolysis only when bromide ions are prsent in the pyrolysis system,

Based on the above discovery that the presence of bromide ions is essential in the pyrolysis of ferricyanide ions and/or ferrocyanide ions, the inventors have developed a complete decomposition treatment of ferricyanide ions and/or ferrocyanide ions as an economical and final treatment for waste water containing ferricyanide ions and/or ferrocyanide ions together with thiosulfate ions, by combining the treatment of the waste water with a weakly-basic anion-exchange resin and the pyrolysis of a concentrated solution of ferricyanide ions and/or ferrocyanide ions in the presence of bromide ions. The process of this invention is an excellent complete treatment for such'waste water.

That is to say, when a waste solution containing ferricyanide and/or ferrocyanide ions and thiosulfate ions is contacted with a weakly-basic anion-exchange resin, the thiosulfate ions are not adsorbed by the ionexchange resin and only ferricyanide ions and/or the ferrocyanide ions are adsorbed on the ion-exchange resin. Therefore, the eluate obtained on regenerating the anion-exchange resin containing the adsorbed ions contains the ferricyanide and/or ferrocyanide ions only and does not contain any thiosulfate ions. Consequently, the eluate can bepy'rolyzed without.and reductive action of the thiosulfate on the hypochlorite, etc., and hence with the addition of a small amount of ions can be decomposed effectively and economically.

However, even when the eluate containing ferricyanide ions and/or ferrocyanide ions without thiosulfate ions is subjected to a pyrolysis treatment, 1 to 10% by weight of the ferricyanide and/or ferrocyanide ions still remain undecomposed. In other words, the complete decomposition of the ferricyanide ions and/or ferrocyanide ions requires the present of bromide ions as described above. By conducting the pyrolysis in the presence of bromide ions in accordance with this invention, the ferricyanide ions and/or the ferrocyanide ionscan be completely decomposed. In the process of treating a waste solution containing ferricyanide and/or ferrocyanide ions and thiosulfate ions by the combination of the treatment with a weakly-basic anion-exchange resin and a pyrolysis treatment, the complete decomposition of the ferricyanide and/or ferrocyanide ions becomes possible only by conducting the pyrolysis in the presence of bromide ions in accordance with this invention. The abovedescribed excellent effects are not obtained by the simple combination of the treatment with a weakly-basic anion-exchange resin and the pyrolysis treatment.

Also, since the eluate from the anion-exchange treatment is obtained as a solution concentrated about 100 to 500 times, the amount of waste water to be subjected to the pyrolysis is H100 to 1/500 of the volume of the original waste solution or water before the anionexchange resin treatment. Thus, the equipment for the pyrolysis may be small and the amount of heat required for the pyrolysis may be small, which results in reducing greatly the cost of the treatment.

In the case of treating ferricyanide ions and/or ferrocyanide ions by pyrolysis, the efficiency of the pyrolysis reaction increases with increasing concentrations of the ferricyanide ions and/or ferrocyanide ions.

That is to say, the higher the concentration of the ferricyanide ions and/or the ferrocyanide ions, the less is the amount of a chlorine compound such as a hypochlorite which may be required, which is economical. Ordinarily, the concentration of ferricyanide ions and- /or ferrocyanide ions most suitable for the pyrolysis treatment is l0,00020,000 p.p.m. as free cyanide ions and the concentration of ferricyanide ions and/or ferrocyanide ions in the eluate recovered from the anionexchange resin treatment is in the aforesaid most suitable range for the pyrolysis.

Also, the regeneration of the weakly-basic anionexchange resin is conducted usually with an alkaline solution, the eluate from the anion-exchange resin treatment has a high pH, and hence it is unnecessary to add additional alkali, if the alkalinity issufficiently high, in the case of conducting the pyrolysis, which is also an advantage of this invention.

Thus, according to the process of this invention, ferricyanide ions and/or ferrocyanide ions present together with thiosulfate ions in waste water from photographic processings or other industrial processings are adsorbed on a weakly-basic anion-exchange resin and then the eluate from the regeneration treatment of the anion-exchange resin is subjected to the pyrolysis treatment in the presence of bromide ions to decompose completely the ferricyanide ions and/or the ferrocyanide ions in it.

On the other hand, Japanese Pat. application No. 22,907/1972 discloses a process of treating waste water containing ferricyanide ions and/or ferrocyanide ions with a weakly-basic anion-exchange resin in the presence of borate ions and further Japanese Pat. application No. 52,267/1972 discloses a similar process in which a weak acid and/or a weak acid salt is used in place of the borate ions.

With those processes it has been confirmed that the exchange facility of a weakly-basic anion-exchange resin to ferricyanide ions and/or ferrocyanide ions .is increased and also the reduction in facility of the anionexchange resin after regeneration is greatly reduced by the presence of the above-described material or materials.

As the result of further investigating the aforesaid prior inventions, the inventors have also discovered that ferricyanide ions and/or ferrocyanide ions in a waste solution containing these ions together with thiosulfate ions can be completely decomposed by combining the above-described principal process of this invention and the aforesaid process of the prior invention. Namely, when waste water containing ferricyanide and/or ferrocyanide ions and thiosulfate ions is treated with a weakly-basic anion-exchange resin after adding thereto at least one of borate ions, a weak acid, and a weak acid salt and then the eluate recovered from the regeneration treatment of the anion-exchange resin is subjected to a pyrolysis after adding bromide ions to the eluate, the ferricyanide ions and/or the ferrocyanide ions can be completely decomposed as in the case of the principal process of this invention in which no additives such as the borate ions, the weak acid, and the weak acid salt are added. Furthermore, in this case ferricyanide ions and ferrocyanide ions are selectively adsorbed by the weakly-basic anion-exchange resin, the thiosulfate ions are not adsorbed by the anionexchange resin, and hence no difficulties based on the reductive action of the thiosulfate in the pyrolysis are encountered. In other words, in the process of this invention at least one of borate ions, a weak acid, and a weak acid salt can be added to the waste water containing the aforesaid ions for further improving the ionexchange capacity of the weakly-basic anion-exchange resin and preventing the reduction in the ion-exchange capacity of the anion-exchange resin without obstructing the effects and the features of this invention. In the second embodiment of the process of this invention, the capacity or facility of the weakly-basic anionexchange resin can be increased without obstructing the complete decomposition of the ferricyanide ions and/or the ferrocyanide ions in the waste water.

Thus, according to the second embodiment of the process of this invention, at least one of borate ions, a weak acid, and a weak acid salt is added to waste water containing ferricyanide and/or ferrocyanide ions and thiosulfate ions, the waste water is treated with a weakly-basic anion-exchange resin, and the eluate obtained in the regeneration of the anion-exchange resin is subjected to a pyrolysis treatment in the presence of bromide ions.

The weakly-basic anion-exchange resins which can be used in the process of this invention are those composed of matrices such as sytrene-divinylbenzene copolymer, a methacrylatedivinylbenzene copolymer, a phenol-formaldehyde copolymer, etc., having at least one of primary amines, secondary amines, and tertiary amines as the ion-exchange group. That is to say, if the weakly-basic anion-exchange resin has at least one of a primary amine, a secondary amine, and a tertiary amine, the matrix of the anion-exchange resin can be of any kind of resin, can be prepared in any manner, can have any polymerization degree and any fine structure such as, e.g., a gel structure, a porous structure, etc., and can be processed in any manner.

Typical commercially available weakly-basic anionexchange resins are those sold under the trade names of Diaion WA-lO, Diaion WA-l I, Diaion WA-20, Diaion WA-ZI, and Diaion WA-3O (made by Mitsubishi Chemical Industries Co., Ltd.), Amberlite IRA-45, Amberlite IRA-93, Amberlite IR-4B, and Amberlite IRP-58 (made by JAPAN Organo Co., Ltd), and Dower-44 (made by Dow Chemical Co.). The weakly-basic anion-exchange resins used in this invention are, however, not limited to these materials as illustrated above. The structures of a few anion-exchange resins of the abovedescribed commercially available materials are shown below:

Diaion WA-lO:

Diaion WA:

Diaion WA-301 wherein m and n are an integers.

The particularly regenerable weakly-basic anionexchange resins of those which can be used in the process of this invention are those having tertiary amine as the ion-exchange functional group and of them a par ticularly excellent weakly-basic anion-exchange resin is Diaion WA-lO. When a weak acid and/or a weak acid salt is present, those weakly-basic anion-exchange resins have the highest ion-exchange facility to ferricyanide ions and/or ferrocyanide ions per volume of the resin and can be most easily regenerated.

As the weakly-basic anion exchangc resin, there are a free-base type and a salt type but the commercially available ones are generally free base type resins. Both the free base type resin and the salt type resin can be used in this invention but the free base type resin is generally used from the standpoint of availability.

The Weakly-basic anion-exchange resin ionexchanged by ferricyanide ions and/or ferrocyanide ions is generally regenerated using an alkaine solution. As the alkaline solution, there are illustrated an aqueous solution of an alkali metal hydroxide such as sodium hydroxide, and potassium hydroxide, an aqueous solution of an alkali metal carbonate such as sodium carbonate and potassium carbonate, and an aqueous solution of ammonia. In the case of using the salt-type weak-basic anionexchange resin, the resin is regenerted with an aqueous hydrochloric acid solution or an aqueous sodium chloride solution. The concentration of the regeneration agent or eluent is about 1 to 20% by weight, in particular 2 to 10% by weight.

Examples of compounds containing borate ion which can be used in this invention are boric acid, metaboric acid, and water-soluble borates such as sodium borate, potassium borate, ammonium borate, and sodium metaborate. Boric acid and/or the borates as illustrated above can be added to the waste water containing ferricyanide ions and/or ferrocyanide ions from photographic processings or other industrial processings and in particular, in the case of photographic processings, boric acid and/or the borate can be added to a photographic processing solution such as a bleach solution, a blix solution, and a reducer. The amount of boric acid and/or the borate used in this invention is usually in the range of 1/10 to 10 times the total of the moles of the ferricyanide ions and the ferrocyanide ions in the waste water from photographic processings or in a photographic processing solution such as a bleach solution, a blix solution, and a reducer. In particular, it is preferred that an amount ranging from 1/5 to 10 times the total of the moles of the ferricyanide ions and/or the ferrocyanide ions be used.

Examples of compounds including the weak acid and/or the weak acid salt which can be used in this invention are organic acids such as acetic acid, citric acid, maleic acid, fumaric acid, oxalic acid, tartaric acid, formic acid, malonic acid, phthalic acid, succinic acid, and the like; the alkali metal salts of theseorganic acids; the ammonium salts of these organic acids; inorganic weak acids such :as phosphoric acid, boric acid, sulfurous acid, and the like; the alkali metal salts of these inorganic acids, and the ammonium saltsof these inorganic acids. The weak acid and/or the weak acid salt as'illustrated above can be added "to the waste watercontaining ferricyanide ions and/or ferrocyanide ions and also in theease of photographic'processings,

it can be added to the processing solution suchas a reducer. For example, when theammonium salt is used for the treatment of the waste water .Farmersreducer, thesame effect is obtained by using ammonium thiosulfate as the thiosulfate. The. amount of the weakacid and/or the weak acid salt is in the range of 1/10 to.10

times the total numberof-molesof the ferricyanide ionsand/or the ferrocyanide ions in the waste water..ln particular, it is preferred that an amount ranging from 1/5 to times the total number of moles of the ferricyanide ions and/or ferrocyanide ions be-used.

According to the process of this invention waste water containing ferricyanide ions and/or ferrocyanide ions'in any concentration can be treated but the process of this invention can be particularly advantageously applied to waste water containingferricyanide ions and/or ferrocyanide ions in aconcentration lower than 3,000 p.p.m., in particular to waste waterhaving aconcentration lower-then 1,000 ppm.

The processof this inventionis also applicable to waste water containing thiosulfateions in an amount of lower than about 150 times the total numberof moles.

of the ferricyanide ions and ferrocyanide ions contained in the waste water. The process is preferably applied to waste water containing thiosulfate ions in an amount of. lower than 100 times the total number of moles of the ferricyanide ions and/or. the ferrocyanide ions therein and in particular the I process is applied more particularly to waste water containing thiosulfate ions in an amount of lower than 50 times the total number of moles of the ferricyanide ions and/or the ferrocyanide ions. o

The contact between the waste water containing ferricyanide and/or ferrocyanide ions and thiosulfate ions.

and the weakly-basic anion-exchange resin can be practiced by any method.

In general, the contacting iswith the weakly-basic an-. ion-exchange resin filled in a cylindrical vesselor a column to provide a layer or zone of the ion-exchange resin and then the wastewater is passed through theion-exchange resin layer or zone from the top to the bottom but as the case may be, the waste water may be passed from the bottom tothe top. According to a manner such as is mentioned abov.e, ferricyanide ions and- /or ferrocyanide ions" can be continuously. removed from the waste water. As the case may be, however, the ion-exchange. treatment can be conducted by adding the weakly-basic anion-exchange resin to thewaste water stored-followed by stirring, allowing "the :ion exchange resin to settle, and recovering the resin by filtration. *However, an advantage in using .the ion-. exchange resin is that the treatment can be continuously conducted and hence passing the waste water continuously througha weakly-basic anionexchange resin column is preferred to the-above described batch method. I

The regeneration of the weakly-basic anionexchange resin thus ion-exchanged with the ferricyanide ionsand/or the ferrocyanide ions is conducted using. analkaline aqueous .solution, As the alkaline aqueous solution, there are illustrated aqueous solutions of art-alkali metal hydroxide such as sodium hydroxide and potassium hydroxide-,an aqueous solution of an alkali metal carbonate such, as sodium carbonate and potassium carbonate, and an aqueous solution of ammonia. The concentration of the solution used for the regeneration is about 1 to-20% by weight, preferably 2 to 10% by weight.

The contact between the alkaline aqueous solution and the weakly-basic anion-exchange resin having ions absorbed thereon can be conducted by any manner. For example, the technique described above in the contact between the waste water and the anionexchange resin can be utilized in the regeneration method also.

By conducting the regeneration of theweakly-basic anion-exchange resin, the ferricyanide ions and/or the ferrocyanide ionsare removed fromthe weakly-basic. anion-exchange resin, that is to say, the solution or the eluate containing the ferricyanide ions and/or the ferrocyanide ions is removed or recovered from the ionexchange system. The eluate contains usually the ferri-' cyanide ions and/or ferrocyanide ions in a high concentration of ordinarily 10,000 to 100,000 ppm. The eluate can be quite conveniently subjected to pyrolysis since it has a high alkalinity and further it contains no salts such as a thiosulfate.

Examples of compounds. containing. bromide ions which can be used the pyrolysis in thepresent invention are alkali metal bromides such as potassium bromide and sodium bromide; alkaline earth metal bromides such-as calcium bromide, barium bromide, and magnesium bromide; and meta] bromides such as aluminum bromide and iron bromide. Ammonium bromide can be also used in this invention for the same purpose. Basicallyflthe water-soluble bromies other than those heavy metal bromides catalytically promoting the decomposition of the hypochlorite, suchas copper bromide and nickel bromide, can be used in this invention. The concentration of the bromide-ions depends-upon the concentration of the ferricyanide ions and/or the ferrocyanide ions but his better to use an aqueous solution of thebromide having a content of higher than 0.1 glliter as'bromide ions. A particularly preferred content of thebromide ions is over 0.5 g/liter.

Since the alkali metal bromides and ammonium bromide are readily available, usually they are used for the pyrolysis treatment.

Examples of the alkali which can be used in the pyrolysis of this invention are alkali metal hydroxides such as'sodium hydroxide and potassium hydroxide and alkali metal carbonates such as sodium carbonate and potassium carbonate. That is to say, the alkali used for the regeneration of the weakly-basic anion-exchange resin having thereon the ferricyanide ions and/or ferrocyanide ions can be used for the pyrolysis in situ.

Examples of suitable hypochlorites .which can be used in the pyrolysis are sodium hypochlorite, potassium hypochlorite, and calcium'hypochlorite. Furthermore, chlorine can alsobe usedfor the purpose. The addition of the alkali is conducted so that the pH of the system is above 12 and in particular better results are obtained the closer the pH is to 'a-pl-l of-'l4. The eluate used for the regeneration of the weakly-basic anionexchange resin inthis invention usually has a pH higher than 12 and in such a case it is unnecessary to add an alkali to the pyrolysis system, which is quite convenient.

The process of this invention can be applied to any waste solutions containing ferricyanide and/or ferrocyanide ions and thiosulfate ions and in particular is suitable for the treatment of waste water from photographic processings.

In the steps of processing silver halide color photographic materials, a solution containing a ferricyanide is used as a bleach solution and a solution containing a thiosulfate is used as fix solution. Therefore, by developing silver halide color photographic materials, waste water containing ferricyanide and/r ferrocyanide ions and thiosulfate ions is formed or discharged. Such waste water can contain acid sodium phosphate, potassium alum, and a pH adjusting agent such as sodium hydroxide, glacial acetic acid, sodium acetate, sodium phosphate, etc. Also, in the processing of reversal silver halide color photographic materials, a bleach solution containing a ferricyanide is used in combination with a fix solution containing a thiosulfate, which results in forming waste water containing ferricyanide and/or fer rocyanide ions and thiosulfate ions. Furthermore, it sometimes happens that the ferricyanide and/or ferrocyanide ions and thiosulfate ions are carried over in the washing water from the fix solution in which the ferricyanide and/or ferrocyanide ions have been carried over.

The waste water containing such ferricyanide and/or ferrocyanide ions and thiosulfate ions is passed through a weakly-basic anion-exchange resin, the ferricyanide ions and/or the ferrocyanide ions are recovered by regenerating the anion-exchange resin as a concentrated solution of these ions without the thiosulfate ions, and then the ferricyanide ions and the ferrocyanide ions contained in the concentrated solution can be completely decomposed into innocuous materials by subjecting the solution to pyrolysis in the presence of the bromide ions. That is to say, in the pyrolysis of this invention, the ferricyanide ions and/or the ferrocyanide ions are decomposed into ferric hydroxide, ferric ox ide, nitrogen, carbon dioxide, and alkali metal carbonates. The ferric hydroxide and ferric oxide thus formed can be easily removed from the solution using known techniques and the amount thereof is generally quite small. Namely, according to the process of this invention, a solution containing ferricyanide ions and/or ferrocyanide ions and not containing any thiosulfate ions can be obtained from waste water containing ferricyanide and/or ferrocyanide ions and thiosulfate ions as the concentrated solution thereof, which is quite convenient for the subsequent pyrolysis treatment. As described above, with the removal of thiosulfate, the loss of the oxidizing agent such as a hypochlorite can be prevented and further since the solution containing the ferricyanide ions and/or the ferrocyanide ions is obtained as a concentrated solution, the efficiency of the pyrolysis is increased and the volume of the solution to be treated in the pyrolysis is small. Therefore, the process of this invention provides quite excellent economical advantages such various aspects as chemicals, equipment, and energy which are used.

Also, since according to the process of this invention the pyrolysis is 100 percent efficient due to the presence of the bromide ions, the ferricyanide ions and/or the ferrocyanide ions can be completely converted into innoculous materials and thus the problem of discharging precipitates containing these noxious materials encountered in the case of employing various aggregation and precipitation processes can be completely eliminated. Thus, the waste water containing ferricyanide ions and ferrocyanide ions can be completely treated in an economical manner by the process of this invention. As described above, a quite large advantage can be obtained by combining the process of using the weaklybasic anion-exchange resin for the treatment of waste water containing ferricyanide and/or ferrocyanide ions and thiosulfate ions and the process of pyrolyzing the eluate containing the ferricyanide ions and ferrocyanide ions only recovered from the regeneration treatment for the anion-exchange resin in the presence of bromide ions according to the process of this invention.

The process of this invention has the following excellent characteristics:

I. Since large and expensive equipment as in the case of employing an electrodialysis, a reverse osmosis, and an aggregation and precipitation process is not required, the space requirements can be small and the equipment cost is low in the process of this invention.

2. Since precipitates containing ferricyanide ions and/or ferrocyanide ions as encountered in the case of employing various aggregation and precipitation processes are not formed in the process of this invention, pollution problems by discharging the waste treated in the process of this invention does not result.

3. There are no problems of causing pollution with undecomposed cyanide gas, sulfur dioxide gas, and smoke as in the case in employing a combustion pro cess and furthermore a large amount of fuel is not required.

4. Since the anion-exchange resin can be used repeatedly after regeneration, which is also a step of the process of this invention, the process is quite economical.

5. The process of this invention is excellent in comparison with the conventional simple pyrolysis from the standpoint that the ferricyanide ions and/or the ferrocyanide ions can be completely decomposed and also the chemicals, energy, and equipment necessary for the process of this invention can be less, which makes this process quite economical.

Now, the invention will be explained further in greater detail by reference to the following examples but the invention is not to be interpreted as being limited to the examples only. Unless otherwise indicated, all percents and parts are by weight.

EXAMPLE 1 In a plastic column having an inside diameter of 4 cm was filled 500 ml of a weakly-basic anion-exchange resin, Diaion WA-lO (trade name, made by Mitsubishi Chemical Industries Co., Ltd.), a solution prepared by diluting Farmers reducer having the composition shown below by about times with water and adding 0.3 g/liter of boric acid was passed through the ionexchange resin as an example of waste water, and then the composition of the water passed through the ionexchange resin column was analyzed.

Composition of Farmers Reducer: Solution A: 37.5 g of ferricyanide was dissolved in water to make a solution of 500 ml.

Solution B: 480 g of anhydrous sodium thiosulfate was dissolved in water to make a solution of 2 liters.

Immediately before use, Solution A was mixed with I Solution B in a volume ratio of l 4.

The sample waste water thus prepared had the following compositionf Ferricyanide ions and ferrocyanide ions:

[Fe(CN) and Fe(CN) 100 p.p.m. as CN- Anhydrous Sodium Thiosulfate (Na S O 2.7

g/liter Boric Acid (H BO 0.3 g/liter The sample waste water prepared above was passed through the ion-exchange resin column and the water processed by the ion-exchange resin was analyzed after processing 1 liter and then 100 liters of the waste water. The results obtained are shown in the following table.

Table 1 Material Present After Treating After Treating 1 Liter I Liters Ferricyanide ions less than 0.5 less than 0.5 and ferrocyanide ions p.p.m. as CN" p.p.m. as CN Anhydrous sodium 26 g/liter 2.7 g/liter thiosulfate The analysis of the ferricyanide ions and ferrocyanide ions was conducted by measuring the spectral absorption of the visible portion of the blue color formed by adding a diluted sulfuric acid solution of 5% ferrous sulfate. The analysis of sodium thiosulfate was conducted by iodometry.

From the above results it was confirmed that the thiosulfate was adsorbed by the weakly-basic anionexchange resin to a lesser degree while the ferricyanide ions and the ferrocyanide ions were selectively adsorbed.

Furthermore, when the sample waste water was treated with the ion-exchange resin, 220 liters of the sample water could be treated in one run until the content of the ferricyanide ions and ferrocyanide ions in the treated water was higher than I p.p.m. as CN'.

After treating 220 liters of the waste water, the ionexchange resin was regenerated using 1 liter ofa 4% by weight aqueous solution of sodium hydroxide and the eluate recovered in the regeneration was subjected to a pyrolysis treatment. The eluate had the following composition: pH: 13.9.

Ferricyanide ions and ferrocyanide ions: p.p.m. as CN- The eluate having the above composition was placed in five beakers in an amount of 200 ml each and after adding thereto aqueous sodium hypochlorite solution (containing 123.0 g/liter of NaOCl) in the amount as shown in Table 2, the mixture was maintained at 85C to conduct the reaction for 2 hours. Furthermore, 8- g of sodium hydroxide was added to the mixture in the beakers ofTest No. 2 and Test No. 4 and 0.4 g of potassium bromide .was added in the beaker of Test Number After 2 hour's the reaction was over, water was added to the mixture to make the total volume 200 ml to compensate for the evaporated water and then the content of the ferricyanide and the ferrocyanide remaining in the solution was measured.

The measurementof 'the total cyanide content was conducted according to the methods of HS-K0102- 29.1.2 and .IISKO102-29.2. I

Theresults obtained are shown in the following table.

Table 2 Test No. NaOCl NaOI-l KBr Total Cyanide Content Remaining (p 1 I g None None 520 2 I85 g 8 g None 2,120 3 27.8 g None None 410 4 27.8 g 8 g None 880 5 18.5 g None 0.4 g Undetected From the above results, it was confirmed that the ferricyanide ions and the ferrocyanide ions present in the eluate recovered from the ion-exchange resin regeneration percent were decomposed when the bromide ions were present.

EXAMPLE 2 An aqueous solution containing 10.6 g/liter of potassium ferricyanide (K [Fe(CN) and 13.5 g/liter of potassium ferrocyanide (K [Fe(CN) 3H O) was prepared and it was experimentally confirmed using this aqueous solution that the presence of the bromide ions was essential for completely decomposing the ferricyanide ions and the ferrocyanide ions in the pyrolysis treatment.

That is to say, 25 g of sodium hydroxide and 25 g of sodium hypochlorite (an aqueous solution of 103 g/liter of sodium hypochlorite was used) were added to 500 ml of the aqueous solution prepared above and the resultant solution was maintained at 85C with the reaction being conducted for 6 hours. In the cases of test numbers 7-10, the bromide as shown in Table 3 was added to the solution before heating in an amount of 0.5 g as bromide ions,

After reacting for 3 hours or 6 hours, the total cyanide content remaining was measured in each case. The analysis of the total cyanide content was made according to the methods of JIS-K0lO2-29.1.2 and HS- K0l02-29.2.

Table 3 Test No. Bromide After Reacting After Reacting for 3 Hours for 6 Hours 6 None 2,450 ppm 2,200 ppm 7 KBr Undetected Undetected 8 Nl-l Br Undetected Undetected 9 CaBr Undetected Undetected l0 AlBn Undetected Undetected From the above results it was confirmed that only when the bromide ions were present did the pyrolysis reaction of the ferricyanide ions and the ferrocyanide ions proceed to the extent of 100 percent.

EXAMPLE 3 plate while washing the surface with water continuously to conduct the reduction and collecting the washing water containing the Farmers reducer.

Composition of Farmers Reducer:

Solution A: 37.5 g of potassium ferricyanide was dissolved in water to make 500 ml of total volume.

Solution B: 650 ml of ammonium thiosulfate (70% solution) was dissolved in water to make 2 liters of total volume.

Immediately before use, Solution A was mixed with Solution B in a volume ratio of l 4.

The concentration of the ferricyanide ions and/or the ferrocyanide ions in the Farmers reducer waste water varied over the range of to about 200 p.p.m. as total cyanide but the mean concentration of these solutions was about 100 p.p.m. as total cyanide. The waste water was passed through the above-described ion-exchange resin column until the concentration of the ferricyanide ions and the ferrocyanide ions in the treated water became greater than 1 p.p.m. as total cyanide content.

Then, after washing the anion-exchange resin with water, the anion-exchange resin was regenerated by passing through the anion-exchange resin liters of an aqueous 6% potassium hydroxide solution at a rate of 500 ml/min. Then, after washing the anionexchange resin sufficiently with water, the above-described waste water was passed through the anion-exchange resin col umn and then the anion-exchange resin was regenerated again. This ion-exchange and regeneration cycle was repeated a total of four times. The amount of the waste water passed through the ion-exchange resin column until the content of the ferricyanide ions and ferrocyanide ions in the treated waste water became greater than 1 p.p.m. as total cyanide content was 4 tons on the average in each case. The amount, the pH, and the total cyanide content in the eluate recovered in the fourth regeneration treatment were as follows.

Amount of the eluate: 14 liters pH: 13.7 Total cyanide content: l7,l00 p.p.m.

Then, an aqueous solution of sodium hypochlorite (containing 123 g/liter of NaOCl) was added to 500 ml of the eluate having the above composition so that the content of the sodium hypochlorite became 0.5 g and after further adding to the solution ammonium bromide at a level of 0.5 g as bromide ions, the mixture was heated to 8085C for 2 hours to conduct the reaction. Thereafter, water was added to the mixture to make 500 ml in total volume to compensate for the evaporated water and the analysis of the total cyanide content was conducted. The analysis in each case was conducted according to the method of JIS K0l02-29.l.2 and .115 K0l02-29.2. The total cyanide content was 0.03 p.p.m.

EXAMPLE 4 In each of the two cylinders having an inside diameter of 4.5 cm was filled 30 ml of a weakly-basic anionexchange resin, Diaion WA-ll (trade name, made by Mitsubishi Chemical Industries Co., Ltd.). Then, a solution prepared by diluting by 100 times a bleach solution having the following composition with water was passed through one of the ion-exchange resin columns at a rate of 300 ml/min.

Composition of the Bleach Solution:

Ferricyanide: lOO g Potassium bromide 30 g Water to make 1 liter A solution prepared by diluting by times a bleach solution having the above composition with water and further adding thereto 1.0 g/liter of boric acid was passed through another ion-exchange resin column at a rate of 300 ml/min.

The amount of the treated solution until the ferricyanide ions were detected (treatment facility) was measured for each ion-exchange resin column. Then, the ion-exchange resin column in which the ferricyanide ions were detected in the treated solution was regenerated in the same way as described in Example 1 and then a solution prepared by diluting by 100 times the bleach solution with water or a solution prepared by diluting by 100 times the bleach solution with water and adding thereto 1.0 g/liter of boric acid was passed through the regenerated ion-exchange resin column. The results obtained are shown in the following table.

Test Additive to Diluted Treatment Facility liter As shown in the above table, where no boric acid was added to the diluted bleach solution, the weakly-basic anion-exchange resin showed no ionexchange capacity for the ferricyanide ions but where boric acid was added to the diluted bleach solution, the anionexchange resin showed a good ion-exchange facility to the ferricyanide ions. Also, the treatment facility of the weakly-basic anion-exchange resin was quite high in the case of adding boric acid and further, the reduction in treatment facility of the anion-exchange resin after regeneration was quite low in the case of adding boric acid.

Then, when the ferricyanide ions and ferrocyanide ions present in the eluate recovered from the regeneration step of the anion-exchange resin were decomposed in the same way as described in Example 1, they were completely decomposed.

EXAMPLE 5 In each of two cylindrical columns having an inside diameter of 4.5 cm was filled 300 ml of a weakly-basic anion-exchange resin, Diaion WA-l I (trade name, made by Mitsubishi Chemical Industries, Co., Ltd.). A solution prepared by diluting by 100 times a bleach solution having the following composition with water was passed through one of the ion-exchange resin columns at a rate of 300 ml/min.

Composition of Bleach Solution:

loo' I v l liter Ferricyanide: Potassium bromide: Water to make.

solution having the above composition with water and adding thereto 2.0 g/liter of sodium dihydrogenphosphate was passed through another ion-exchange resin column at a rate of 300 ml/min. Then, the amount of the solution passed through each ion-exhange resin column until the ferricyanide ions were detected in the treated solution (treatment facility) was measured in each case.

Thereafter, the anion-exchange resin which showed the ferricyanide ions in the treated solution was regenerated in the same way as described in Example 1 and then a solution prepared by diluting by 100 times the bleach solution of the solution prepared by diluting by 100 times the bleach solution and adding 2.0 g/liter of sodium dihydrogenphosphate was passed through the regenerated ion-exchange resin column., The results obtained are shown in the following table.

Test Additive to Diluted Treatment Facility phosphate 2.0 g/ liter As shown in the above table, where no sodium dihydrogenphosphate was added to the diluted bleach solution, the weakly-basic anion-exchange resin showed no ion-exchange facility for the ferricyanide ions, while in the case of adding sodium dihydrogenphosphate, the anion-exchange resin showed good ion-exchange facility for the ferricyanide ions. Furthermore, in the case of adding sodium dihydrogenphosphate, the treatment facility of the anion-exchange resin was quite high and further the reduction in the treatment facility of the anion-exchange resin after regeneration was quite low.

Then, when the ferricyanide ions and the ferrocyanide ions in the eluate recovered from the regeneration treatment of the anion-exchange resin were decomposed in the same way as describedin Example 1, they were completely decomposed.

While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing-from the spirit and scope thereof.

What is claimed is: I

1. A process of treating waste water containing ferricyanide ions and ferrocyanide ions which comprises bringing said waste water containing these ions into contact with a weakly-basic anion-exchange resin for adsorption of ferricyanide and ferrocyanide ions on said resin, removing said weakly-basic anion-exchange resin having adsorbed thereon ferricyanide and ferrocyanide ions from said waste water, immersing said .18 weaklwb asic, anion-exchange resin having said ferricyanide and ferrocyanide,..ions adsorbed. thereoninto an alkaline solu tionitb' provide .an alkaline concentrated solution of ,said, ferricyanide. and .ferrocyanide ions, adding .to.is aid alkaline concentrate'd" solution a strong alkali, a hypochlorite,.andbromide ions, so that the pH of saidsolution is above 1 2, and heating said solution to temperatures wabout 509C .:at? normal. pressure,

whereby said ferricyanide and ferrocyanide ions are decomposed, wherein said bromide ions serve to accelerate the heat decomposition of ferricyanide ions and ferrocyanide ions during said heating.

2. The process of claim 1, wherein said bringing of said waste water into contact with said weakly-basic anion-exchange resin is in the presence of at least one group consisting of boric acid, metaboric acid, or

water-soluble borate salts.

6. The process of claim 5, wherein said borate ions are present in an amount of from US to 10" times the total of the moles of said ferricyanide ions and said ferrocyanide ions present.

7. The process of claim 2, wherein said weak acid is selected from the group consisting of an organic acid and an inorganic acid.

8. The process of claim 7, wherein said organic acid is selected from the group consisting of acetic acid, citric acid, maleic acid, fumaric acid, oxalic acid, tartaric acid, formic acid, malonic acid, phthalic acid, or succinic acid, and wherein said inorganic acid is selected from the group consisting of phosphoric acid, boric acid, or sulfurous acid.

9. The process of claim 2, wherein said weak acid salt is a member selected from the group consisting of an alkali metal salt or an ammonium salt of a member selected from the group consisting of a weak organic acid and a weak inorganic acid.

10. The process of claim 9, wherein said weak acid salt is a member selected from the group consisting of an alkali metal salt and an ammonium salt of a member selected from the group consisting of acetic acid, citric acid, maleic acid, fumaric acid, oxalic acid, tartaric acid, formic acid, malonic acid, phthalic acid, succinic acid, phosphoric acid, boric acid, and sulfurous acid.

11. The process of claim 2, wherein said member selected from the group consisting of said weak acid and said weak acid salt is present at from 1/10 to 10 times the total numer of moles of said ferricyanide ions and said ferrocyanide ions in said waste water.

12. The process of claim 1, wherein said waste water additionally contains thiosulfate ions.

13. The process of claim 1, wherein said waste water is waste water from photographic processings.

14. The process of claim 1, wherein said ferricyanide ions and said ferrocyanide ions are present in said waste water at a concentration lower than 3,000 ppm.

15. The process of claim 1, wherein said alkaline solution comprises a solution of a member selected from ions are from a compound containing bromide ions, said compound being a member selected from the group consisting of an alkali metal bromide, an alkaline earth metal bromide, a water soluble metal bromide, or

ammonium bromide.

19. The process of claim 18, wherein said bromide ions are present at a concentration of higher than 0.1 g/liter.

Claims

1.A PROCESS FOR TREATING WASTE WATER CONTAINING FERRICYANIDE IONS AND FERROCYANIDE IONS WHICH COMPRISES BRINGING SAID WASTE WATER CONTAINING THESE IONS INTO CONTACT WITH A WEAKLYBASIC ANION-EXCHANGE RESIN FOR ADSORPTION OF FERRICYANIDE AND FERROCYANIDE IONS ON SAID RESIN, REMOVING SAID WEAKLY-BASIC ANION-EXCHANGE RESIN HAVING ADSORBED THEREON FERRICYANIDE AND FERROCYANIDE IONS FROM SAID WASTE WATER, IMMERSING SAID WEAKLY-BASIC ANION-EXCHANGING RESIN HAVING SAID FERRICYANIDE AND FERROCYANIDE IONS ADSORBED THEREON INTO AN ALKALINE SOLUTION TO PROVIDE AN ALKALINE CONCENTRATED SOLUTION OF SAID FERRICYANIDE AND FERROCYANIDE IONS, ADDING TO SAID ALKALINE CONCENTRATED SOLUTION A STRONG ALKALI, A HYPOCHLORITE, AND BROMIDE IONS SO THAT THE PH OF SAID SOLUTION IS ABOVE 12, AND HEATING SAID SOLUTION TO TEMPERATURES ABOUT 50*C AT NORMAL PRESSURE, WHEREBY SAID FERRICYANIDE AND FERROCYANIDE IONS ARE DECOMPOSED, WHEREIN SAID BROMIDE IONS SERVE TO ACCELERATE THE HEAT DECOMPOSITION OF FERRICYANIDE IONS AND FERROCYANIDE IONS DURING SAID HEAING.

2. The process of claim 1, wherein said bringing of said waste water into contact with said weakly-basic anion-exchange resin is in the presence of at least one member selected from the group consisting of borate ions, a weak acid and a weak acid salt.

3. The process of claim 2, wherein said waste water additionally contains thiosulfate ions.

4. The process of claim 3, wherein said waste water is waste water from photographic processings.

5. The process of claim 2, wherein said borate ions are from a compound containing borate ions, said compound containing borate ions being selected from the group consisting of boric acid, metaboric acid, or water-soluble borate salts.

6. The process of claim 5, wherein said borate ions are present in an amount of from 1/5 to 104 times the total of the moles of said ferricyanide ions and said ferrocyanide ions present.

11. The process of claim 2, wherein said member selected from the group consisting of said weak acid and said weak acid salt is present at from 1/10 to 105 times the total numer of moles of said ferricyanide ions and said ferrocyanide ions in said waste water.

15. The process of claim 1, wherein said alkaline solution comprises a solution of a member selected from the group consisting of an alkali metal hydroxide, an alkali metal carbonate, or ammonia.

16. The process of claim 15, wherein the concentration of said alkali solution is about 1 to 20% by weight.

17. The process of claim 1, wherein said hypochlorite is a member selected from the group consisting of sodium hypochlorite, potassium hypochlorite, calcium hypochlorite, or chlorine in an aqueous alkaline solution.

18. The process of claim 1, wherein said bromide ions are from a compound containing bromide ions, said compound being a member selected from the group consisting of an alkali metal bromide, an alkaline earth metal bromide, a water soluble metal bromide, or ammonium bromide.