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Electrolysisê zanyari

Metalên bi electrolysisê paqijkirina

Prosesa ya metalên bi electrolysisê paqijkirina da ku ji metalên rawî yên xasrên wergeran derbas bike. Di vê procesan de, blokên metal rawî yên xasrên wergeran di anoda de hatin bikar bînin, dilûyên nekên metal ên jî dîlektrolît û platekên metalên paqij û tevkerandî yên cathode.

Copperi bi electrolysisê paqijkirina

Ji bo çêdanan prosesa ya metalên bi electrolysisê paqijkirina, dibe ku mînakê ya copperi bi electrolysisê paqijkirina bibînim. Copperi ji oreke tê gotin, ku "blister copper" di nav de hate, 98% sê 99% paqij e, lê bi prosesê electrorefining yê ser ast 99.95% paqij dibike.

Di vê prosesan de electrolysis, blokên copperi rawî yên xasrên wergeran di anoda de hatin bikar bînin, copper sulfate acidified sulfuric acid, di dîlektrolîta de û platekên copperi paqij yên bi graphite tevkerandin, di cathode de.
Copper sulfate divê were parç in positive copper ion (Cu+ +) û negative sulfate ion (SO4 − −). Positive copper ion (Cu+ +) an cations ber bi electrode negatifên paqij copperi kêm hate, electrons di cathode de hate girtin, û Cu atom hatin dibike û li ser surface graphite cathode hate depozit kirin.

Bi hêman SO4 − − ber bi electrode pozitif an anode kêm hate, electrons di anode de hate girtin û radical SO4 dibike, lê radical SO4 tune xwe nehatiye, copperi anode hatiye xerabkirin û CuSO4 dibike. Vê CuSO4 hatiye dissolvkirin û divê parç in positive copper ion (Cu+ +) û negative sulfate ion (SO4 − −). Vê positive copper ions (Cu+ +) ber bi electrode negatif kêm hate, electrons di cathode de hate girtin, û Cu atoms dibike û li ser surface graphite cathode hate depozit kirin. Bi vê raya, copperi rawî yên xasrên wergeran hate transfer kirin û li ser surface graphite cathode hate depozit kirin.

Metal impurities anode hatiye merge kirin bi SO4, metallic sulfate dibike û li ser dîlektrolîta solution hate dissolvkirin. Impurities silver û gold, ku nayê têne têkildin ji sulfuric acid-copper sulfate solution, hate settle down as anode sludge or mud. Bi interval regular electrolytic refining of copper, copper deposited hate strip out from cathode û anode û hate replace kirin bi new block of crude copper.
NB :- Ji bo process of electrolytic refining of metals or simply electro refining, cathode hatiye coated bi graphite so that the chemical deposited, can be easily stripped off. This is one of the very common applications of electrolysis.

Electroplating

Process of electroplating theoretically same as electrorefining – only difference is that, in place of graphite coated cathode we have to place an object on which the electroplating has to be done. Let’s take an example of brass key which is to be copper-platted by using copper electroplating.

Copper Electroplating

We have already stated that copper sulfate splits into positive copper ion (Cu+ +) and negative sulfate ion (SO4 − −) in its solution. For copper electroplating, we use copper sulfate solution as electrolyte, pure copper as anode and an object (a brass key) as cathode. The pure copper rod is connected with positive terminal and the brass key is connected with negative terminal of a battery. While these copper rod and key are immersed into copper-sulfate solution, the copper rod will behave as anode and the key will behave as cathode. As the cathode or the brass key is connected with negative terminal of battery, it will attract the positive cations or Cu+ + ions and on reaching of Cu+ + ions on the surface of the brass key, they will receive electrons from it, become neutral copper atom and are about to be deposited on the surface of the brass key as uniform layer. The sulfate or SO4 − − ions move to the anode and extract copper from it into the solution as mentioned in the process of electro-refining. For proper and uniform copper plating, the object (here it is brass key) is being rotated slowly into the solution.

Electroforming

Reproduction of objects by electro-deposition on some sort of mould is known as electroforming. This is another very useful example among many applications of electrolysis. For that, first we have to take the impression of objects on wax or on other wax like material. The surface of the wax mold which bears exact impression of the object, is coated with graphite powder in order to make it conducting. Then the mold is dipped into the electrolyte solution as cathode. During electrolysis process, the electrolyte metal will be deposited on the graphite coated impressed surface of the mold. After obtaining a layer of desired thickness, the article is removed and the wax is melted to get the reproduced object in form of metal shell. A popular use of electroforming is reproduction of gramophone record dices. The original recording is done on a record of wax composition. This wax mold is then coated with gold powder to make it conducting. Then this mold is dipped into a blue vitriol electrolyte as cathode. The solution is kept saturated by using a copper anode. The copper electroforming on the wax mold produces master plate which is used to stamp a large number of shellac discs.

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