Applications of Electrolysis:
Electrolytic Refining of Metals:
The process of electrolytic refining of metals is used to remove impurities from ores. Here in this process, a block of raw metal is used as anode, a dilute salt of this metal is used as electrolyte and plates of this pure metal are used as cathode.
Electrolytic Refining of Copper:
To understand the process of electrolytic refining of metals, we will discuss an example of electrolytic refining of copper. The copper extracted from its ore, known as blister copper, is 98 to 99 percent pure but can be easily refined to 99.95 percent pure for electrical use by an electrorefining process.
In this process of electrolysis, we use a block of impure copper as anode or positive electrode, copper sulphate with sulfuric acid as electrolyte and pure copper plates coated with graphite, cathode or negative. used as electrodes.
Copper sulfate dissociates into positive copper ions (Cu++) and negative sulfate ions (SO4 − − ). The positive copper ion (Cu++) or cations will move to the negative electrode made of pure copper where it takes an electron from the cathode, and the Cu becomes an atom and accumulates on the graphite surface of the cathode.
On the other hand, SO4 − − will move towards the positive electrode or anode where it will gain electrons from the anode and form the radical SO4 but since the radical SO4 cannot exist alone, it will attack the copper of the anode and form CuSO4 . This CuSO4 will then dissolve and dissociate in solution as positive copper ions (Cu++) and negative sulfate ions (SO4 − − ). These positive copper ions (Cu++) will then move to the negative electrode where they take electrons from the cathode, and become Cu atoms and deposit on the graphite surface of the cathode. In this way the impure raw copper will be transferred and deposited on the graphite surface of the cathode.
Metal impurities of the anode also combine with SO4, forming metal sulfates and dissolving in the electrolyte solution. Impurities such as silver and gold, which are not affected by the sulfuric acid-copper sulfate solution, will settle out as anode sludge or sludge. At regular intervals in electrolytic copper refining, the deposited copper is removed from the cathode and anode and replaced with a new block of raw copper.
Note: In the process of electrolytic refining of metals or simply electrorefining, the cathode is coated with graphite to facilitate the removal of accumulated chemicals. And This is one of the very common applications of electrolysis.
The process of electroplating is theoretically the same as electrorefining – the only difference is that instead of a graphite-coated cathode, we have to place an object on which to electroplat. Let’s take an example of a brass key that is to be plated with copper using copper electroplating.
We have already mentioned that copper sulfate dissociates in its solution into positive copper ion (Cu++) and negative sulfate ion (SO4 − − ). For copper electroplating, we use copper sulfate solution as electrolyte, pure copper as anode and an object (brass key) as cathode. A pure copper rod is connected to the positive terminal and a brass key is connected to the negative terminal of the battery. While the copper rod and key are immersed in the copper sulfate solution, the copper rod will behave as the anode and the key will behave as the cathode. Since the cathode or brass key is connected to the negative terminal of the battery, it will attract positive cations or Cu++ ions and when they reach the Cu++ ions on the surface of the brass key they will gain electrons from it, the neutral copper. will become The atoms are deposited as a uniform layer on the surface of the brass key. Sulfate or SO4 − − ions migrate to the anode and remove copper from it into solution as described in the electrorefining process. For proper and uniform copper plating, the object (here it is a brass key) is slowly rotated in the solution.
The reproduction of objects by electrodeposition on some type of mold is called electroforming. This is another very useful example among the many applications of electrolysis. For this we first need to take an impression of the objects on wax or other wax-like materials. The surface of the wax mold, on which the exact impression of the object is made, is coated with graphite powder to conduct it. The mold is then immersed in an electrolyte solution as the cathode. During the electrolysis process, the electrolyte metal will be deposited on the graphite-coated impressed surface of the mold. After obtaining a layer of the desired thickness, the article is removed and the wax is melted down to obtain the regenerated object in the form of a metal shell. A popular use of electroforming is the reproduction of gramophone record discs. The actual recording is done on a wax texture record. This wax mold is then coated with gold powder to make it conductive. The mold is then dipped in a blue vitriol electrolyte as the cathode. The solution is kept saturated using a copper anode. Electroforming copper on a wax mold produces a master plate that is used to stamp large numbers of shellac discs.