SU1219679A1 - Method of silver electrolyte reclamation - Google Patents

Description

The invention relates to galvanized pins, in particular, to a method for the regeneration of spent dicyanoargenic tatno-rhodanide electrolyte (TCARE) for applying silver coatings, as well as coatings with silver alloys. DSARE also includes synergide-rich, ferrocyaninated electrolytes, which are chemical analogues of DTARE.

The aim of the invention is to ensure the continuity of the process, accelerate regeneration, eliminate unnecessary adjustment for silver and increase the life of the electrolyte.

A positive effect is achieved by introducing into the electrolyte a substance selected from the oxynite group, reel, mainly acetone cyan hydrin.

The amount of oxynitrile required for regeneration of the CEARE is found by the formula

1 -h M., V

. V; i,

 107, 867 - 1000 - p

where h is the concentration of PKC, g / l;

V is the volume of the regenerated,

ml; M is the molecular weight of oxynitrile,

g;

P is the density of oxynitrile, g / cm. The decomposition of the RCC characterizes the following equation

 , i-SCN

.2 ", - (SCN) J A, (CN); + ZRj-C-Rj42H

Where

sn

R ,, - - -c.Hj ....

During the operation of the CEARE, as a part of it, there is an accumulation of the Rod Ag silver complex (SCN) (RCS). This leads to a deterioration in the quality of the pads, the formation of a pitting on the surface to be coated, and a deterioration in the adhesion to the substrate. The presence and accumulation of PCS in DCARE prevents the co-precipitation of silver with the alloying metal, for example, with antimony, and the production of electroplating by the alloy. The main reasons for the formation and accumulation of CSWs in DCARE are: the accumulation in the electrolyte of foreign metal salts due to cementation occurring on the de-energized surface; ingestion of residues of acids or exposure to vapors in DCARE; anodic and imbalance

79.

cathodic processes during the deposition of silver alloys.

In order to ensure the stability of the CEARE - the prevention of acidification

The electrolyte is added with an equimolar amount of alkali, perime substantially caustic potassium, in relation to the added amount of oxynitrile. Hydrogen (1+) released by the reaction

carbonates contained in DCARE are bonded. If the input quantities of oxynitriles are small (on the order of 1 ml / l), and the carbonate content in the CEAR exceeds the allowable amounts, the introduction of alkali into the electrolyte is optional.

Example 1. Take 1000 ml of the electrolyte composition, g / l: Ag (in the form of KAg (CN) 38; Ag (in the form of РКС) 2;

KSCN 250; 60

With overweighing, 2 ml of glycolic acid nitrile (α-hydroxy-nitrile) are added. Silver is coated from the regenerated electrolyte at current densities O, -1-2.0 A / dm.

PRI mme R 2. Take 1000 ml of the electrolyte composition, g / l: Ag (in the form of KAg {CN), 25; Ag (as PKC) 5; (CN) g 40; KSCN 150; .

With stirring, 12.5 ml of 2-hydroxy-2-nitro-1-butane (-methyl-ethyl-oxynitrile,) is added to the solution. Silver coated from regenerated electrolyte at current densities

0.3-0.5 A / dm:

PRI me R 3. Take 1000 ml

electrolyte composition, g / l: Aj (in the form of KAg (CN)) 10; Ag (as PKC) 15; KSCN 250; thirty.

Option 1. While stirring, 25.5 ml of acetone cyanohydrin (-2-hydroxy-2-nitrile-propane-dimethyl-oxynitrile) and 15.6 of potassium hydroxide are added. In this case, an amount of

acetone cyanohydrin, equivalent to the content of RCS in DCARE.

Option 2. While stirring, add 30 ml of acetone cyanohydrin

and 18.4 g potassium hydroxide. In this case, an excess of acetone cyanohydrin is used. The introduction of excess-acentone-gianhydrin does not degrade the quality of coatings obtained from regenerated electrolyte.

Silver from both solutions is coated at current densities of 0.3-0.5 A / dm.

If the spent electrolyte is significantly contaminated by harmful impurities (salts of copper, zinc, iron, etc.), the silver is first regenerated from the spent electrolyte. Thereby, purification of these impurities is achieved.

Acetone cyanohydrin is the most available reagent, although other oxynitriles can also be used along with it.

The table shows a comparative description of the known methods of regeneration and the proposed method. The electrolyte of the following composition is subjected to regeneration, g / l: silver (in the form of PKC) 10; in the form of potassium dicyano argentate 10, potash 30

duration of regeneration

slime

Determination of residual silver concentration in DCARE

Correction of electrolyte with potassium dicyanoargentate

Silver regeneration from filtered sludge

Determined by the area of the auxiliary cathode and the amperage, for example, during a real load, Q 1 dmVl D 1, time 150 min

19679

As can be seen from the table, the proposed method ensures the continuity of the silvering process, a high regeneration rate, the elimination of silver corrections, and an increase in the lifetime of the silver electrolyte.

The quality of the coatings obtained from the electrolyte regenerated 10 according to the invention is not inferior to the quality of the coatings obtained after regeneration in a known manner. Multiple regeneration of electrolyte, according to the proposed method, 15 does not lead to a deterioration in the quality of coatings.

The invention can find application in the regeneration of silver plating electrolytes.

Cooling the solution to the working temperature

Filtering and returning the solution to the electrolyzer

Dilution with water to the desired volume

It is determined by 1–2 min type and heat exchanger capacity, usually 120–180 min (not including the solution cooling time to operating temperature)

About 10 g / l No

DCARE + silver-BCARE-silver-containing precipitate containing

requiring non precipitation

Editor P, Kossey

Compiled by Y. Pozdeeva TehredL. Oliynyk Proofreader L. Pilipenko

Order 1237/38 Circulation 615 Subscription VSHPI USSR State Committee

for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5

- ™ ---- - ----- - - - --.-. - .. - .- --..and ....-. .one--. - - -. „

Branch ShSh Patent, Uzhgorod, st. Project, 4

Table continuation

Not

Ready for

application

DTsARE

Claims (1)

METHOD FOR REGENERATING SILVER ELECTROLYTES, mainly dinanoargentate-rhodanide, including the decomposition of the silver rhodanide complex, characterized in that, in order to ensure the continuity of the process, accelerate the regeneration of eliminating unnecessary silver adjustment and increase the life of the electrolyte, the decomposition is carried out by a substance selected from the oxynitrile group introduced in stoichiometric amounts with respect to the thiocyanate silver complex. _ § SU.,., 1219679