Method of processing waste solutions


(57) Abstract:

The method of processing the treated solutions containing organic complexes of heavy metals, sulfur compounds and nitrogen and other compounds that may be present in the fixing and the like photographic baths and photochemical production, is that the spent solution is sprayed in the at least one spray chamber or device in the flow of hot oxidizing gas, in particular, generated in industrial plants or incineration, with the addition of nitrate ions and calcium ions. 7 C.p. f-crystals, 1 table.

The invention relates to a method of processing waste solutions from fixing, etc., of the photographic baths and photochemical production containing organic complexes of heavy metals and compounds of sulfur and nitrogen.

Up to the present time of fixing, bleaching and fixing other baths, for example, baths containing silver, silver was extracted by electrolysis, ion exchange (with iron filters) or by reacting with a solution of sulfide. The result has been a complete removal of the silver solution and possibly other heavy metals, such what's solutions were burned or incinerated together with household garbage. This, however, there are problems associated with environmental pollution. Fixing baths, in particular, have a high chemical oxygen demand (COD), high nitrogen content in Kjeldal and contain complex compounds of heavy metals. The COD value of such solutions is to 80000 mg/l, and nitrogen content on Kjeldal 20000 mg/l At the discharge into the sewer amount of pollution equivalent number of people (i. e. ) is determined by the formula i.e. 0/136 (COD + 4,57 N). When the discharge into the sewer for 24 h 1000 l of spent solution contamination will be i.e. 1/136x(80000+4,h) 1257.

Thus, 365 m3waste solutions in the year cause pollution in 1257 i.e. Burning waste solutions together with household waste due to the high sulphur content leads to severe environmental pollution by sulphur dioxide.

It was proposed to oxidize waste solutions of hydrogen peroxide, chromic acid, potassium permanganate, chlorine bleaching solution, and so on, However, the oxidation process in this way is not until the end, and, furthermore, the method is very expensive.

A method of processing waste solutions by atomization exhaust RA is x calcium ions and nitrate, and recycling the spent solution. However, this method is environmental pollution.

The present invention is to provide a method for processing waste solutions of the above type, which would not have these disadvantages. The object of the present invention, therefore, is the above method, in which the spent liquor is sprayed into the flow of hot oxidizing gas, in particular, generated in industrial plants or the combustion furnace and at least one spray chamber or in the same place with the addition of nitrates and calcium ions.

In particular, the spent solution is sprayed into the hot gas stream so that the temperature of only the sprayed material with additives increased to more than 50, sometimes up to more than 100aboutC. Preferably, the pH of the spent solution was reduced to less than 5. This can be done by using acid or by acid gas components that are often present in industrial waste gases. In these conditions occur numerous reactions between the hot gas and sprayed liquid, resulting from the spent solution is removed of razli calcium sulfate, which can be removed as sludge. Heavy metals, in particular, in the acidic environment, leaving the organic complex compounds, and the latter is decomposed with the formation of exhaust gases, such as nitrogen, carbon dioxide and water vapor. Heavy metal ions can be precipitated from the spent solution by alkalizing and silver may be removed, for example, by adding sodium chloride.

The exhaust products from the combustion chamber waste solutions it is advisable to return and again sprayed into the hot gas stream. In the return flow each time it passes through the stage at which it can be removed by various components. For example, the circulating stream may be subjected to electrolysis or cementation with iron for separation of metals. The advantage of cementation in addition is that the solution process is enriched with iron. With increasing pH of the circulating flow above 5 can be precipitated hydroxides of heavy metals. For this purpose it is preferable to add calcium hydroxide. Residues at various stages, can be removed by conventional means, for example by sedimentation or filtration. the de Kitchen salt or other soluble chloride. You can however enter the halide and the flow of hot oxidizing gas. In many cases, the halide is already present in industrial gases.

Below the invention will be explained on the example of the treatment of spent fixing solutions in the photographic industry. Such waste solutions containing various metal complexes, in particular ethylenedinitrilotetraacetic (EDTA) complexes of copper, iron, silver, chromium and Nickel. To ensure adequate content of nitrate and calcium such spent solutions add calcium nitrate. The thus treated exhaust solution is subjected to reaction with the hot oxidizing gas is formed, for example, in a furnace for burning. This interaction is performed by spraying the spent solution in the hot gas stream so that the temperature of the solution together with additives would rise above 50, and in certain places even above 100aboutC. in Addition, it is necessary that the pH of the spent solution was below 5, which can be done by acidification or by acidic components already present in the gas stream.

Under these conditions, the spent solution with additives as b is="ptx2">

So, present in the waste solution of the thiosulfate transformed into an insoluble calcium sulfate according to the following reaction scheme


SO2+oxidant+(cat.Cu++Fe+++Ag+euz.) _ SO3< / BR>
SO3+H2O _ 2H++SO-4-< / BR>
SO-4-+Ca++_ CaSO4< / BR>
Precipitated calcium sulfate can be easily removed.

In addition to the calcium sulphate may be precipitated sulphate of lead according to the following reaction

SO-4-+Pb++_ PbSO4< / BR>
Thus, ions Pb++can be removed from the used hot gas.

Ammonium ions present in the waste solution or hot gas, interact with nitrate-ions in the spent solution from the reaction

NH+4+NO-3NH4NO3N +2H2O+(1/2)O

Released during oxygen contributes to the further degradation due to oxidation of complex compounds present in the extract solution.

Similar transformations occur with the present amines, such as R-NH and R1-NH-R2to finish.

Organic compounds of heavy metals such as EDTA complexes, gradually oxidized by the oxidizing agents contained in the hot gas stream. These reactions are catalytically accelerated eye-catching free ions of Fe++, Cu++Hg++and Ag++.

As the EDTA complex of iron is the most stable complex, all other above-mentioned metals are in the form of free ions from their EDTA complexes due to an excess of Fe+++. Last, if necessary, is introduced into the system. In the EDTA decomposes according to the following reaction scheme:

EDTA complex metal MeH2EDTA


H2EDTA+oxidant+cat __ N +xCO +yH2O

the pH of the liquid withdrawn from the stage of spraying wash liquid), is brought to a value higher than 5 by adding thereto calcium hydroxide. The result is the precipitation of heavy metals as hydroxides.

Ag+remaining in solution can be precipitated by adding a solution of chloride or bromide. The halides may be introduced in the gas flow or already be present in it. Deposition of silver occurs by the following reactions

Ag++Cl-__ AgCl4and PbSO4. Ammonium salts and amines are removed in the form of N2H2O and oxygen. And finally EDTA complexes and other organic compounds are completely oxidized to CO2N2O, and N2. The spent solution, purified during continuous circulation from harmful components, can be together with gas quietly dropped. The precipitated solid components can be collected for recycling or disposal in such a way as not to harm the environment.

P R I m m e R. the Flow of hot gas produced in the furnace for combustion, is subjected to contacting in a reactor of the type Venturi with waste fixing the washing liquid. Obtained when the combustion gas contains fly ash, which is a large number of heavy metals, acid gases HB5, HCl, HF, SO2, NOx and gases such as N2O2, CO and CO2. To exhaust solution, playing the role of a washing liquid in a continuous process that systematically add auxiliary materials, namely "Ajax" and M. I. R.". "Ajax" is a mixture of CA(OH)2and Ca(NO3)2and "M. I. R." a mixture of Cu(NH3)++, NH4+, NO3-, Cl-BF4, CrO "M. I. R." determined the content of NH4and Cu++.

In the used fixing solution was determined by the content of heavy metals, NH4+Ca++, SO4--, Br-, Cl-and the amount of dry matter.

During the process was continuous deposition of a solid material, composed of CaSO4, PbS4CaF2, AgBr, AgCl, SiO2and hydroxides of heavy metals.

In the beginning of the process contents of the reactor was 12 m3waste fixing solution. At the end of test 17 days after the start, the reactor was 12 m3wash liquid. During the test through the reactor was dropped to 75 m3waste fixing solution and added 1.3 m3"M. I. R., and 15 m3"Ajax".

The results are shown in the table. From the table of results we can draw the following conclusions:

1. Is almost complete decomposition of the complexes, since the solution heavy metals are not detected. Significantly reduced COD.

2. Is almost complete decomposition of NH4+ and NO3-.

3. Thiosulfate decomposes to form sulfur and sulfate.

4. Perhaps almost postulados decomposition of waste fixing solution of photochemical production. Similarly you can, however, decompose, and other waste solutions containing complex compounds of metals, for example, from the electronic industry and electroplating plants, wastewater from laboratories with high COD, ammonia baths, sulfamethazine waste water, etc.

Although the inventive method is illustrated using the above example, it is obvious that other variants and modifications within the present invention.

1. METHOD of PROCESSING WASTE SOLUTIONS mainly photographic baths and photochemical production by atomization of the spent solution into the flow of flue gases at a temperature above the 50oWith the addition of absorbers containing calcium ions and nitrates, and recycling the spent solution, characterized in that the spent solution is acidified to pH < 5.

2. The method according to p. 1, wherein the exhaust solution is added an excess of ions of Fe+++.

3. The method according to PP.1 and 2, characterized in that make up the contents of F+++in the recycled stream.

4. The method according to PP. 1 and 3, characterized in that zirconium, what is the pH of the circulating solution to support more than 5.

6. The method according to p. 5, characterized in that the pH of the circulating solution provide by the introduction of calcium hydroxide.

7. The method according to PP.1 to 6, characterized in that the worked solution add halide.

8. The method according to p. 7, characterized in that the halide is introduced into the waste gas stream.


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