CS221253B2 - Winning of cyanide from electrolytic rinsing waters containing the soluble cyanides - Google Patents

Abstract

Soluble cyanides contained in rinse solutions are transformed by chemical reaction exemplified by (M(CN)<u2,3,4>u)<s1,2,3->s+ n MC1 = n MCN into insoluble precipitates which are recovered.

Description

The invention relates to a simple process for the precipitation, recovery and reuse of cyanides from rinsing water, which is industrially applicable in the electrolytic deposition of metals.

Electroplating is looking for systems and methods that are more economical and practical for the treatment and detoxification of rinsing water. Working in the electrochemical sector is very complicated, requires specialized forces, is associated with high costs, energy consumption and the need for skilled workers. There is also a high consumption of valuable chemicals in the electroplating industry, with the formation of deposits and residues that are rich in heavy metals, which are normally lost when toxic substances are detoxified.

It is well known to those skilled in the art that the treatment of cyanide-containing waste waters is mainly done by decomposing the cyanides. Another method known as "Recycling" involves evaporating water using energy to concentrate liquids, which are then reused in the respective baths.

Furthermore, methods are known in which ion exchangers using chemicals are used, associated with their decomposition losses and high installation costs.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a process for recovering cyanides from wastewater from the electrolysis of various metals containing cyanides.

According to the invention, in obtaining cyanides from the rinse waters of the cyanide electrolytic deposition processes, compounds which convert the soluble cyanides into insoluble cyanides are used for the treatment of cyanide-containing rinsing waters. This allows them to be removed by filtration or decantation. Insoluble cyanides can thus be easily reused industrially. This represents a significant advance over traditional processing of harmful substances from the electroplating processes.

The process according to the invention allows complete precipitation of cyanides in insoluble form together with cyanide metals, their recovery and industrial reuse.

In the process according to the invention, depending on the cyanide content of the rinsing water, the corresponding metal salts corresponding to the cyanide metal in the rinsing water and the galvanic bath are added. For example, zinc sulfate or zinc chloride for the rinse water of the zinc cyanide bath, or copper sulfate or copper chloride for the copper rinse water. cyanide baths, together with acidic or alkaline salts, which regulate the pH of the rinse water and the valence of the metal ions, respectively, of the metal type, in order to convert the total free cyanide and complex salts into simple water-insoluble cyanides. The pH value of the rinsing water must be suitable. No cyano gases evolve.

All cyanide in the rinsing water becomes insoluble. salts and can therefore be easily removed from the water, for example, by decantation or filtration.

If separate rinsing baths are used for each type of metal electrolytic deposition without mixing the metals together, the cyanides precipitated in this way can be reused directly in the corresponding galvanic baths after washing the insoluble precipitate on the filters or decanting with water until the water reaches a density 1.006 or 0.9991 g / cm ³ to remove precipitated cyanides from all soluble constituents.

If desired, additional salts and / or acids may be added to the metal salts to control the pH of the aqueous medium and salts, gases and / or acids to correct the valence of the metal ions.

The process according to the invention also serves to precipitate and / or recover cyanides from any cyanide liquid used in the electrolytic deposition processes of zinc, cadmium, copper, silver, gold and their alloys.

The experiments also show the simplicity of the process of recovering cyanides from the rinsing waters of the cyanide electrolytic deposition process according to the invention without the need for technically trained specialists, without special equipment, without use. of any cyanide decomposition chemicals. The process according to the invention recovers all valuable chemicals from water, the value of the metal salts used for precipitation being two to six times lower than the value of the material obtained.

In order to demonstrate the technical and economic value of the process of recovering cyanides from the rinse water of the cyanide metal electrodeposition processes of the invention, two examples are given:

1. Cyanide zinc bath, consisting of:

g / 1 zinc cyanide g / 1 sodium cyanide g / 1 sodium hydroxide

When 1 liter of zinc bath enters the rinse tank, the following material is required to precipitate soluble cyanides and a portion of sodium hydroxide:

200 g of zinc sulphate

The weight of recovered material is then:

120 g of zinc cyanide g of zinc hydroxide

This is 5.8 times the value of recovered material compared to the material used for recovery. The water is free of cyanides and heavy metals after this treatment. All that remains is sodium sulfate and a small amount of sodium hydroxide which can be easily neutralized.

Second cupro cyanide bath of the following composition g / 1 an ^{alkyl ID} cupric ^g / ^{1 alkyl} with an ^{id d} Nu g / 1 sodium hydroxide ^where, on the ^d oo ^p lachovac ^{etting Aad} RZE ^d remains one liter copper bath needs to precipitate soluble cyanides:

161 g cuprous chloride.

The weight of recovered material is then 210 g of cuprous cyanide. Thus, the value of the material obtained is 2.1 times the value of the material used for recovery.

The water after treatment no ^ides cyano and no t ^ěžké metals. Only sodium chloride ^remains in soluble form, which is not a problem in wastewater treatment.

Both examples show well the technical and economic value of the process according to the invention.

Tradmrn ^PU method ^{characterized} racovárn ^p to ^y n indicate ^Ids water following the consumption of chemical products during the decomposition of cyanide-free recovery:

Case 1:

Per 1 liter of zinc bath consumes:

360 g of chlorine

410 g of sodium hydroxide

Case 2:

On lttr ^copper 'on ^the marks ^{of la} with ^p ot ^of eibuje:

^{430 g of} chlorine

490 g of sodium hydroxide

In most countries are copper, zinc, cadmium, silver, gold and cyanide imported cloths ^l ^ so. still ^has to Prevent ztr ^I m ^{A fifth} of these products in the rinse waters elektrochtemtetóho dia ^y services (gateanotechntee).

For the electroplating industry, the problem to comply with the standards defined by public kontroJímmi bodies Toer ZOD ^p OVI ^d Aji 'to maintain ^and has oc ^h wound prostrata ^ and ^kt er ^s i ^z requires ^í dostaterné and p ^p ln ^E z ^P Rácová ^and MC ^h emic ^to industrial waste water.

The high toxicity of cyanides is well Zn ^and has the as ^p and alpha tipsify ^{H L} N ^of determined ^EXAMPLE strictly nu ^s and ^t Né kontroty prope ^h or ^{g and} n ^of gal · vanotechnickém industry.

The process of the invention is one which facilitates the processing of cyanide evaporating them at a ^{d d PRICE} EMZ user ignites ^ka recovery of material gain. O ^{p p} political control of the ^TA Úsobí é ušetn pnstroje and thereby the ^lke n ^{C O} and ^dy. In addition, environmental pollution is prevented.

^ETHOD ZIS ^{Ka á} m ^alkyl or ^{du as} waste in ^{d ky} anidovýc ^hp PROCESS elektrotytického teachings of metal ^P of ^dl ev ^y n and ^l EZÚ mfóe also use ^P ro alia ^p Úsobí ^{characterized five} n ^e it ZFE ^{Ka o} n tyanidů ^{s p f} is the Rice ^H odnota for IOTC and elektrochemn undisputed ^and in ^width in all countries.

The following four chemical equation showing the formation of an insoluble ^ him ^copper cyanide thereof (CuCN) dissolved potassium cyanide (KCN) to produce a complex salt ^{of p} mo ^s maiden him cyanide m ^edi. DATEM is ^ rn ^ I ^to extended ^p U.S. ^t n ^{and k} om ^pl ective salt ^to yamdu m ^EDI [Cu ^ bP ^{'3 "P} s ^d Anim chlorteu me ^d' n ^e it (CuCl) přecMzí the insoluble copper cyanide with proce ^and Mo ^dp and ^d the water.

7J

2J

3.) xý [cu (CN) _from J

CuCN + KCN + KCN

K ^ Cu ícrrr ^J -> C, ca (CN?

[(^ U ^ ^ N) _3]

1,2, Ъ ~ + OCUC1 --- yn ^CuCN ^ [CufCNj] •?

3 ^C u ^(CN b. * | Insoluble with sodium cyanide, yielding a soluble complex zinc cyanide salt, which can precipitate in the period of waste water treatment according to the equation

In the fourth equation there are no problems confusing copper chloride (CuCl) with copper sulfate (CuSCU).

When insoluble zinc cyanide is used as the zinc bath feed ZnjCNj (CN) * - ZnSO. - t2 Zn (CN) _z

Neroz (insoluble)

When we generalize the precipitation and wastewater equation, we obtain cyanides with the corresponding or M-symbol with atomic masses.

between 60 and 200, can be similarly from η ⁴ i ² i ³

M f _n MCt-> aMCN

M (Cn + MSO +) and M (Cn ^{) 2}

Claims (9)

SUBJECT ............ . Process for recovering cyanides from electrolytic rinsing waters containing soluble cyanides, characterized in that metal salts are added to the rinsing water by which the soluble cyanides are converted into insoluble cyanides and these are then separated by decantation or filtration. 2. A process according to claim 1, wherein metal salts corresponding to the rinsing water cyanide and galvanic bath metal content are added. 3. The process of claim 1 wherein the total rinse water cyanide content is converted into an insoluble salt, then filtered or decanted, the salt is washed until the wash water has a density of 1.006 or 0.9991 g / cm &lt; 3 &gt; se precipitated kya- The invention frees all soluble components and can be reused directly in a galvanic bath. 4. A process according to claim 1, characterized in that metal salts are added, the metals of which have an atomic mass of more than 60, and, if necessary, salts, gases and / or acids which change the valence of the metal ions in water and / or or salts and / or acids are added together to correct the pH of the aqueous medium. 5. A process according to any one of claims 1 to 4, characterized in that cyanides containing electrolysis of zinc, copper, cadmium, silver or gold or their alloys are used. 6. The method of claims 1 to 5, wherein the precipitation proceeds according to the equation nMCt → nMCN m (cn) * nM (CN wherein M represents a metal with an atomic mass of 60 to 200). 7. Method according to claim 1, 2, 3, 4, 5 and 6, characterized in that the cyanides are precipitated in the rinsing waters of the copper bath at a pH of 1.5 to 4.0, preferably at a pH of 2.0, by adding sodium bisulfite NaHSO 3 changes the pH from the alkaline range to the acid range, preferably to a pH of 2.0 without the addition of hydrochloric acid, while, if necessary, the copper valency, where the CuCN precipitate is to be copper, is changed at the same time. 8. A process according to claim 1, 2, 3, 4, 5 and 6 wherein the cyanides from the cadmium rinse water are precipitated in two stages, wherein in the first step the flow rate must be diluted to less than 17 g / l cyanide. cadmium in the form of insoluble zinc cyanide Zn (CN) 2 by the addition of an equivalent amount of zinc salt and in a second stage cadmium ions are precipitated from the rinsing water by the addition of sodium carbonate or sodium sulfide or another chemical product in the cadmium. insoluble cadmium salt. 9. A process according to claim 1, wherein zinc salts, preferably zinc sulfate, are added to a rinsing liquid from a metal surface treatment or metal quenching plant or to dissolved cyanide-containing industrial wastes to precipitate soluble cyanides. in the form of insoluble zinc cyanide.