NL8020027A - RECOVERY OF CYANIDES FROM FLUSHING WATER FROM CYANIDE PROCESSES FOR THE ELECTROLYTIC COATING OF METALS. - Google Patents

Description

N.o. 29,455 ® ®20 Q 27; Recovery of cyanides from rinsing water from cyanide processes for the electrolytic coating of metals.

The present invention relates to a simple method for the precipitation, recovery and reuse of cyanides from rinse water, which is applicable in industrial methods of electrolytic coating of metals. In the field of electroplating, systems and methods are sought that are more economical and practical for the treatment and detoxification of rinse water. The work developed in this field of electrochemistry is very complicated, requires specialized workers, involves a large 10 outlay in energy use and the costs of specialized workers. The high consumption of chemicals in electroplating is known, with the detoxification of the toxic components resulting in suspensions and residues, which are rich in heavy metals and which are thereby lost.

The recovery of cyanides from rinse water from the cyanide processes for the electrolytic coating of metals languages aims to treat chemical products! of rinsing water with cyanides, whereby the! Soluble cyanides are converted into insoluble cyanides; making it possible to remove it by filtration or settling. The insoluble cyanides can therefore be used; easy to be used industrially. The subordinate; | a method introduced in the art of electrochemistry; 25 represents an advance over the traditional treatment of residues from electroplating; i i processes.

It is well known to those skilled in the art that; the treatment of the cyanide-containing rinsing water mainly by the detoxification process of the destruction i; | of the cyanides is carried out. Another method is | Known as "recycling" is based on the evaporation of the: solvent in the rinse water using energy; to concentrate the liquids which are then used in the respective baths.

Also known are the methods in which ion exchange

J-jOCL: 'Ei'oLC

8020027 2 traders are employed which involve high capital investment for equipment and loss of chemical products due to their destruction.

The present process allows for the total precipitation of the cyanides in their insoluble form along with the metals of the cyanides as well as their recovery and industrial reuse.

According to the content of the cyanides in the rinse water, appropriate amounts of metal salts are added, which correspond to the metal of the cyanides in the rinse water and in the galvanic bath. For example, the zinc sulfate or chloride for the rinse water of the cyanides containing zinc baths, or the copper sulfate or chloride for the rinse water of the cyanides containing copper baths, are combined with acidic or alkaline salts, which increase the pH of the rinse water and the valence of the metal ions control, according to the type of metal, therewith a sequence; Empty conversion of the total free cyanide and the cyanide united in complex salts to obtain a simple metal containing cyanide, insoluble in water, with an appropriate pH in the rinse water without developing cyan gases.

The total cyanide in the rinse water is converted to an insoluble salt and can therefore be removed from the rinse solution by settling or filtering. ;

Is used for any type of metal in the process for; the electrolytic coating of metals can be separated by rinsing without danger of mixing of the metals with each other, then the precipitated metal cyanides can be used by this process called "recovery" of cyanides from rinsing water! of cyanide processes for the electrolytic coating of metals "re-used directly in the respective galvanic baths j after washing them (the insoluble precipitate) in filters or by settling with water, until the rinse water reaches a density of 1000 or 0 ° Bé, which frees the precipitated cyanides from all other soluble constituents.

The same method proposed here also serves for the precipitation and / or recovery of cyanides from any 40 cyanide-containing liquid used in the electrolytic coating of zinc, cadmium, copper, silver, gold and their alloys.

The initial tests already demonstrate the simplicity of the process of recovering cyanides from rinse water from the cyanide processes for the electrolytic coating. metals without the need for technically trained personnel and without special installations, nor are chemicals used for subsequent destruction. The process completely recovers the valuable chemicals from the water, with the value of the metal salts for precipitation and recovery being two to six times lower than the value of the recovered material.

To demonstrate the technical and economic value of the process for the "recovery of cyanides from rinse water from the cyanide processes for electrolytic coating of metals", two examples will be mentioned: first case: cyanide-containing zinc bath with the following composition: 60 g / 1 zinc cyanide of Cr & 130.00 = Cr $ 7.80 20 50 g / 1 sodium cyanide of Cr $ 100.00 = Cr $ 5.00 70 g / 1 caustic soda of Cr $ 18.00 = Cr £ l> 1.26 = Cr $ 13.06.

When one liter of zinc bath is removed into the rinsing reservoir, the following is required to precipitate the soluble cyanides and part of the caustic soda: material: i 200 g of zinc sulfate of Cr $ 14.00 / kg = CrS 2, 80.

: The value of the recovered material is then i: 30; 120 g zinc cyanide of Cr $ 130.00 / kg = Cr ^ 15.60! ! 16 g zinc hydroxide from Crife 40.00 / kg = Cr $ 0.64; j = Cr $ 16.24.

That means the 5.8-fold value of the reclaimed! ; one material compared to the material used i 35 for recovery. The water after this treatment is free from cyanides, free from heavy metals, and contains only sodium sulfate and traces of sodium hydroxide, which is easy to neutralize.

| Second case: cyanide-containing copper bath with the following 40 composition: 8020027 4 60 g / 1 copper cyanide of Cr $ 180.00 / kg = Cr & 10.80 81 g / 1 sodium cyanide of Cr $ 100.00 / kg = Cr $ 8, 10 15 g / 1 caustic soda of Cr $ 18.00 / kg = Cr $ 0.27 = Cr $ 19.17.

When one liter of copper bath is discharged into the rinsing reservoir, it is necessary to precipitate the insoluble cyanides: 161 g of copper chloride of Cr $ 111.60 / kg = Cr $ 17.96.

The value of the recovered material is then as follows: 210 g of copper cyanide from 0 $ 180.00 / kg = Cr $ 37.80.

The value of the recovered material is therefore 2.1 times higher than the material used for the recovery.

The water after the treatment is then free of cyanides, free of heavy metals and only sodium chloride remains, which is no problem for the wastewater treatment.

The two exemplary cases show well the technical and economic value of the "recovery of cyanides from rinse water from cyanide processes for the electrolytic coating of metals".

Traditional methods of treating cyanide-containing water show the following values regarding the use of chemicals for the destruction of the non-regenerable cyanides: first case: consuming one liter of zinc bath: 360 g of chlorine = Cr $ 2 .88 410 g of caustic soda = Cr & 7 * 38 total = Cr & 10.26.

Second case: for one liter of copper bath the following is used: [430 g chlorine = Cr £ 1> 3.44; 490 g caustic soda = Cr $ 8.82! I total = Cr & 12.26. ί i These costs do not yet represent costs for the filtration i; 35 and separation of the suspension, for the capital investment for equipment and the operating costs of the storage! of these residues in suitable places.

In these comparative tests, the physical values are; international constants, Values expressed in money 40 can show the cost of the products per country.

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The monetary values are to be regarded as a comparison and in Brazil about 50 Brazilian cruzeiros correspond to one US dollar. (1.00 = Cr $ 50.00). In most countries copper, zinc, cadmium, silver, gold and 5 cyanides are imported products, which justifies avoiding the loss of these products in the electroplating industry's rinse water.

The electroplating industry faces challenges in adhering to the standards of the public 10 control bodies responsible for preserving and protecting the environment. They require adequate and complete treatment of chemical industrial waste products.

Very well known is the great toxicity of the cyanides, which justifies the rigorous and necessary control of the public bodies in the electroplating industry.

Thus, the method of "recovering cyanides from rinsing water from cyanide processes for the electrical coating of metals" is the only one that allows the treatment of cyanides containing wastewater, while at the same time benefiting the user through the recovery of materials, by visual inspection of the process, eliminating the need for expensive equipment and avoiding environmental degradation.

The method of recovering cyanides from rinse water from cyanide processes for the electrolytic plating of metals may also be an applicable technique for other cyanide recovery processes. where the importance for chemistry and electrochemistry in all countries need not be discussed.

! Let the following four chemical reaction equations! seeing the course of the reaction of insoluble copper cyanide (CuCN) | 55 with the potassium cyanide dissolved to form the complex salt of soluble copper cyanide, further shows how it dissolves; bare copper cyanide complex by adding copper chloride is converted into insoluble copper cyanide at the rinse water treatment stage: 8020027 ♦ 6 1.) CuCN + KCN = K (Cu (CN) 2) 2.) K (Cu (CN) 2) + KCN = K2 (Cu (CN) 5): 3.) K2 (Cu (CN) 5) κ2 (Cu (CN) 2) "^ (Cu (CN) 3) 2" 5 (Cu (CN) ^) ^ "" 4.) (Cu (CN) q 7 i.) ^ '2' ^ "'+ nCuCl = nCuCN insoluble.

12 it

In the fourth comparison, there are no problems with the exchange of copper chloride by copper sulfate.

Using the insoluble zinc cyanide Zn (CN) 2 with the sodium cyanide to form zinc baths gives the soluble complex salt of the zinc cyanide, which can be precipitated with zinc sulfate at the rinsing water treatment step according to the reaction equation ZnCCN) ^ 2 ”+ ZnSO ^ = 2 Zn (CN) 2 insoluble.

15 The equation for precipitation can be generalized

, -M- being considered as a symbol of a metal, the atomic weight of which is between 60 and 200, permitting the object of the recovery of the cyanides and the respective metals from the rinse water .: 20 (M (CN) 0.11.5 "+ nMCl = nMCN

M (CN) 2 ”+ MSO2 = nM (CO2).

Thus, the technical and economic importance proposed by the recovery of cyanides from rinse water from the cyanide processes of the electrolytic coating of metals can be seen in the addition of metal salts together with salts and / or acids to control the pH of the water and together with salts, gases and / or acids to correct the valency of the metal ions, if required.

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Claims (6)

1. Recovery of cyanides from rinse water from cyanide processes for the electrolytic coating of metals proposed by a simple method of precipitating, recovering and industrially re-using the cyanides from rinse water, which are conventionally used in the usual methods of the electrolytic coating of metals are lost. The electroplating industry requires an economical and practical system for the treatment of rinsing water. This has been included in the technical sector of electrochemistry, in particular in the recovery of waste products from rinsing water. It is characterized by the addition of chemical products that the soluble cyanides present in the rinse water are converted into insoluble cyanides by a chemical reaction, thereby enabling recovery and reuse for industrial purposes. This recovery should take place by the usual settling or filtration methods. 2. Recovery of cyanides from rinsing water from the metal electrolytic coating cyanide processes according to claim 1, characterized by the total precipitation of insoluble cyanides in the rinsing water accompanied by the metals from the residual cyanides in order to attempt such industrial recovery According to the amount of cyanide in the rinse water, there must be additions of appropriate amounts of metal salts corresponding to the metal associated with the cyanide in the rinse water and the electrolytic coating of the metal bath. 3. Recovery of cyanides from rinsing water from the; cyanide processes for the electrolytic coating of metals; languages according to claims 1 and 2, characterized in; note that the total amount present in the water; cyanide has been converted to an insoluble salt, allowing easy extraction from the rinse water through settling or filtering and the precipitated metal cyan; nide can be re-used directly in the respective galvanic baths after they have been rinsed. The insoluble precipitate will be obtained in pure form 8020027 * v for reuse in the filters or settling reservoirs after the wash water has reached a density of 1000 or 0 ° B; under these conditions it is cyanide. precipitate separated from other insolubles. Recovery of cyanides from rinse water according to the cyanide processes for the electrolytic coating of metals according to claims 1,2 and 3, characterized by the addition of metal salts, the metals of the salts having an atomic weight of more than 60 and, if necessary, together with salts, gases and / or acids, which change the valency of the metal ions present in the rinse water, and / or combined with salts and / or acids to correct the pH of the water. 5 · Recovery of cyanides from rinse water from the 15 cyanide processes for the electrolytic coating of metals; languages according to claims 1, 2, 3 and 4, characterized in that it is also used for the precipitation and recovery of any cyanide-containing liquid used for the electrolytic coating 20 'process of zinc, copper, cadmium, silver or gold and their alloys. 6. Recovery of cyanides from rinsing water from the cyanide processes for the electrolytic coating of metals according to claims 1, 2, 3 »4- and 5» characterized by a generalized chemical equation, wherein the symbol -M- represents a metal with a atomic weight between 60 and 200, and the general eligible formula is thus represented: (M (CN) 0, + nMCl + nMCN »2» 4-30 m (CN) ^ - + MSO ^ = nM (CN) 2 . ******* 8020027