FI67356C - FOERFARANDE FOER AOTERVINNING AV CYANIDER FRAON SPOLLOESNINGARERHAOLLNA FRAON ELUTFAELLNINGSPROCESSER - Google Patents

Description

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Patent · och registrerttyreleen AmUm uthfd odi utukrtft · * pubdcarad 30.11.o-4 (32) (33) (31) Pjrydetty utuoikuu »—8 * fird prior ** 29.01.79 Brasi1ia-Brasi 1 ien (BR) PI 7900707 (71 ) (72) Michael Franz-Xaver Peuser, Rua Princesa Isabel, 266, 18 °. And.

Ap. 188, BR-0 ^ 601 Sao Paulo S.P.,

Jose Benedito Bartolo, Rua Sao Nicolau 210, BR-09900 Diadema SP, Brazil-Brazil (BR) (7 * 0 Oy Koister Ab (5 * 0 Method of rinsing solutions from cyanides or electroprecipitation processes) - Application of the spinning solution frän elutfä11 ningsprocesser

The invention relates to a process for recovering cyanides from complex cyanide-containing rinsing solutions obtained from an electroprecipitation process.

The electroplating industry has sought more economical and practical systems and methods for cleaning flushing solutions. The methods developed in this sector of electrochemistry are complex and require specialized personnel to operate the equipment. The methods are expensive due to high energy costs and specialized labor. It is well known that large amounts of chemical products are lost in the electroplating industry and large amounts of heavy metal-containing sludges are formed during treatment to decompose toxins.

It has been found that the recovery of cyanides from cyanide-containing rinsing solutions obtained from electroprecipitation processes can be performed using chemical products to convert soluble cyanide 67356 to insoluble cyanide, allowing the cyanide to be removed by filtration or precipitation. Insoluble cyanide can then be easily reused industrially.

It is known that the treatment of cyanide-containing rinsing solutions is carried out mainly using a detoxification process in which the cyanide is decomposed. Another known method, the recovery process, is based on evaporating the solvent from the rinsing solutions, using energy to concentrate the liquids, after which the liquids are reused in the respective baths. Other methods using ion exchangers are known and involve large capital investments for equipment as well as the loss of chemical products.

The present invention relates to a process for recovering cyanides from complex cyanide-containing rinsing solutions obtained from electroprecipitation processes of zinc, copper, cadmium, silver, gold and their alloys. The process is characterized in that the cyanide is precipitated by adding a salt of the same metal present in the complex cyanide dissolved in the rinsing solution, after which the cyanide is recovered, e.g. by filtration.

The process according to the invention makes it possible to completely precipitate the cyanides in insoluble form together with the cyanide metals and to recover them for industrial reuse.

Depending on the amount of cyanide contained in the rinsing solution, a sufficient amount of metal salt is added, in which the metal is the same as the metal associated with the cyanide in the rinsing solution and the electroplating bath. For example, zinc sulphate and / or chloride may be used for cyanide-containing zinc bath rinsing solutions or copper sulphate and / or chloride for cyanide-containing copper bath rinsing solution, together with acid or base salts of all types which control the pH of the rinsing solution, the cyanide and cyanides in the form of complex salts are converted into a simple metal cyanide which is insoluble in the water contained in the rinsing solution at a suitable pH without the release of cyanide gases.

Any cyanide in the water is thus converted to an insoluble salt and removed from the rinsing solution by precipitation or filtration.

Il 67356 By using separate rinsing tanks for each type of metal in the metal-precipitation process without the risk of mixing the metals, the metal cyanides can be reused directly in the corresponding baths after rinsing (insoluble precipitate) with filters or precipitation with water until the rinsing water reaches a density of other soluble components.

No specialized technical personnel or special equipment are required to perform the method according to the invention. The process also does not produce chemical products that must be disposed of later. It effectively regenerates valuable chemical products from waters. The value of the metal salt used for precipitation is 1 / 2-1 / 6 of the value of the reclaimed material.

To demonstrate the technical and economic advantage of the method according to the invention, two examples are presented:

Example 1: cyanide-containing zinc bath having the following composition: 60 g / l zinc cyanide, price Cr $ 130.00 / kg = Cr $ 7.80 50 g / l sodium cyanide, price Cr $ 100.00 / kg = Cr $ 5 5.00 70 g / l sodium hydroxide, price Crg 18.00 / kg = Crg 1.26 one liter zinc bath Cr # 13.06

When one liter of zinc bath is sprayed into the rinsing tank, the following substances are needed to precipitate soluble cyanide and some sodium hydroxide: -200 g of zinc sulphate, price Cr # 14.00 / kg = Cr $ 2.80 The value of the recovered and precipitated substance is afterwards: -120 g of zinc cyanide, price Cr $ 130.00 / kg = Cr # 15.60 16 g zinc hydroxide, price Cr $ 40.00 / kg = Cr # 0.64 Value of recovered material Crg 16.24 This means that the value of recovered material is 5 , 8 times the value of the substance to be recovered. After this treatment, the water is free of cyanides and heavy metals, leaving only sodium sulphate and small amounts of sodium hydroxide, which can be easily neutralized.

6735 6

Example 2: cyanide-containing copper bath with the following composition: 60 g / l copper cyanide, price Cr $ 180.00 p / kg = Cr $ 10.80 81 g / l sodium cyanide, price Cr $ 100.00 p / kg = Cr $ 8.10 15 g / l sodium hydroxide, price Cr? 18.00 p / kg = Cr $ 0.27 per liter of copper bath Crg 19.17

Thus, one liter of copper bath, when sprayed into the rinsing tank, needs the following amount of substances to precipitate soluble cyanide: 161 g of copper chloride, price Cr $ 111.60 p / kg = Cr # 17.96.

The value of the recovered and precipitated material is then as follows: 210 g of copper cyanide, price Cr $$ 180.00 p / kg = Crj2 37.80.

The value of the reclaimed material is thus 2.1 times higher than the value of the metal salt used in the recovery. There are no cyanides or heavy metals in the water after treatment and only sodium chloride remains, which is not a problem in water treatment.

The above two examples clearly show the advantage of the method according to the invention.

Conventional methods for treating cyanide-containing waters give the following values for the chemicals used to decompose unrecovered cyanides:

Example 1: for one liter of zinc bath: - 360 g of chloride = Cr £ 2.88 410 g of sodium carbonate = Crg 7.38

Total Cr # 10.26

Example 2: per liter of copper bath: - 43 g of chloride = Cr $ 3.44 4 90 g of sodium carbonate = Crg> 8.82

Total Crg> 12.26 These costs do not yet include filtration and sludge separation costs, equipment capital investment, and operating costs for the storage of these wastes in sufficient facilities.

In most countries, copper, zinc, cadmium, silver, gold and cyanides are imported materials, so losses of these products should be avoided. From an ecological point of view, it is also important that industrial waste can be treated efficiently.

Il 5 67356

The high toxicity of cyanides is well known and therefore great attention is paid to their handling in the galvanizing industry.

The method according to the invention makes it possible to treat cyanide-containing wastewater in a simple manner without expensive equipment and without ecological adverse effects.

The following reaction equations show the reactions of insoluble copper cyanide with potassium cyanide in solution to form a soluble: copper cyanide complex salt. In addition, they show how the soluble copper cyanide complex salt, with the addition of copper chloride, is converted to insoluble copper cyanide during the treatment of the lipstick solution: - 1) CuCN + KCN = K (Cu (CN),) - 2) K (Cu (CN) 2) + KCN = K2 ( Cu (CN) 3) - 3) K2 (Cu (CN) 3) = K2 (Cu (CN) 2) ~ (Cu (CN) 3) 2_ (Cu (CN) 4) 3 “- 4) (Cu (CN) CN) ",.) ^ '2'3 + nCuCl = nCuCN insoluble

Z f ό f H

In formula 4, copper chloride can be replaced by copper sulfate.

By using insoluble zinc cyanide with sodium cyanide in a zinc bath system, a soluble zinc cyanide complex salt is obtained, which is precipitated with zinc sulphate in the rinsing solution treatment step according to the following formula: 2-

Zn (CN). + Zn SO. = 2Zn (CN) 0, insoluble.

4 4 L ·

The precipitation formula can be generalized by marking the metal with the symbol M:

(M (CN) -..) 1,2,3 + nMCl = nMCN

• YZ. f 3 t 4 M (CN) 4 "+ MSO 4 = nM (CN) 2

If necessary, together with metal salts, salts and / or acids and / or gases can be added to the lipstick solutions to regulate the pH of the water and / or acids to correct the valence of the metal ions.

Claims (4)

A process for recovering cyanides from complex cyanide-containing rinsing solutions obtained by electroprecipitation processes of zinc, copper, cadmium, silver, gold and their alloys, characterized in that the cyanide is precipitated by adding the same metal salt present in the rinsing solution, after which the cyanide is recovered, e.g. by filtration. Process according to Claim 1, characterized in that the precipitated metal cyanide is washed with water until the washing water reaches a density of 1,000, i.e. 0 ° Be. Process according to Claim 1 or 2, characterized in that, in addition to the metal salt, gases and / or acids are added to change the valences of the metal ions in the rinsing solution and / or to adjust the pH of the water. Process for recovering cyanide from a complex cyanide-containing rinsing solution obtained from an electroprecipitation of copper according to claim 1, characterized in that sodium hydrogen sulphite and sodium sulphite, optionally sulfur sulphite and optionally sulfur sulphite are added to the rinsing solution together with copper salt, preferably copper sulphate or copper chloride. during the precipitation, the pH is 1.5-4.0, preferably 2.0-3.0, and pure copper cyanide is recovered.