Minerals
The term “mineral” refers to the naturally occurring substance in which metals or their compounds can be found in the earth.
Ores
Ores are the minerals from which metals can be economically and readily mined.
Native ores
These ores contain metals like silver, gold, platinum, etc. in their free form.
Metallurgy
This term refers to the entire process of separating a pure metal from one of its ore.
Gangue or Matrix
Most ores contain silicates that are worthless, such as dirt, sand, and stones. These undesirable impurities found in ores are referred to as matrix or gangue.
The process of concentrating ores, also known as ore-dressing, involves removing unwelcome silica and earth impurities from the ore.
Physical techniques and chemical processes are used to concentrate ore.
Chemical techniques and Physical techniques include:
Hand-picking
This method is utilized when the contaminants are easily distinguishable from the ore and can be done so with the naked eye.
Gravity separation
Hydraulic washing, or levigation: These methods of separation rely on the distinction between the specific gravities of the ore and gangue particles.
Magnetic separation
This technique can be used to separate components that are magnetic in nature, such as ore or impurities.
Smelting
This process involves reducing the ore to the molten metal at a high temperature. (b) Reduction to free metal Strong reducing agents like C, H2 CO, Al, Mg, etc. are employed to remove electropositive metals like Pb, Fe, and Sn.
Auto-reduction process
This term refers to the self-reduction procedures.
Electrolytic process
By electrolyzing the oxides, hydroxides, or chlorides of highly electropositive metals like Na, K, Mg, Ca, Al, etc. in a fused state, the oxides of these metals are removed. For instance, cryolite and alumina are electrolyzed to produce Al.
Refining
The process of removing impurities from metals that have been extracted is known as refining.
Chromatography is founded on the idea that the various elements in a mixture may be separated.
Metal separation from its concentrated ore, concentrated ore must be transformed into a form that can be reduced to metal in order to extract the metal. Metals are separated from concentrated ore using two main processes.
Conversion to oxide and metal reduction from oxide.
Ore is transformed into metal oxide.
The process of calcining involves heating ore to a high temperature in order to remove volatile compounds.
Roasting
The process of heating ores in the presence of too much oxygen.
Sulfide ores are mostly employed in this procedure.
While some metal oxides are exceedingly difficult to reduce, others can be reduced rather quickly. In any event, heating is necessary. Gibbs energy interpretations are used to comprehend the variance in the temperature needed for thermal reductions (pyrometallurgy) and to foretell which element will work best as a reducing agent for a specific metal oxide ( MxOy ). The equation states how the Gibbs energy, G, changes for every process at any given temperature:
G = H T S, where H represents the method’s enthalpy change and S its entropy change.
- The reaction will only take place if the value of G is negative. If S is positive, increasing the temperature (T) would result in a rise in T-value S’s (H T-S), which would cause G to become.
- If the net value of G for the two potential reactions is negative and the reactants and products of the two reactions are combined in a system, the reaction will take place. Therefore, coupling the two reactions, obtaining their sum, and then determining the magnitude and sign of G are all steps in the interpretation process. Gibbs energy (G) vs. T graphs for the production of the oxides in the Ellingham Diagram make it simple to understand this linkage.
An adequate reducing agent for the reduction of oxides is provided by Ellingham Diagram. We can forecast the viability of ore thermal reduction using such representations.
a) Iron from iron oxide: Chemical impurities are removed. Silica (SiO2), an acidic chemical contaminant, is contained in the ore.
To remove Silica, a basic flux such as quicklime (CaO) is applied.
The source of CaO is limestone (CaCO3), which under the extreme heat of the furnace breaks down into CaO and CO2.
Calcium silicate, or CaSiO3, is created when the contaminant SiO2 interacts with CaO and is known as slag.
b) Iron Extraction: In the presence of a reducing agent called coke, the pure hematite ore ferric oxide (Fe2O3) is reduced to iron (carbon).
Carbon monoxide, a potent reducing agent that is created when coke
(C) and Carbon dioxide react, reduces the oxidant Fe2O3 to iron (Fe)
Slag, or calcium silicate (CaSiO3), floats on top of molten iron because it is lighter than the metal. This stops the molten iron from oxidizing in the furnace’s presence of oxygen.
Separate collections are made of the molten iron and the slag.
Zinc (Zn) extraction from Zinc Oxide (ZnO)
Coke is used in the reduction of zinc oxide. Compared to copper, this situation has a higher temperature. The oxide is produced into briquettes for heating with coke and clay.
ZnO + C(coke)→Zn + CO at 673K
By quickly freezing, the metal is distilled off and collected.
READ MORE: Chemistry Class 12 Chapter 5 – Surface Chemistry
Purification of the metal
Any method of metal extraction usually leaves some impurities behind. Depending on the differences in the characteristics of the metal and the impurity present, different procedures are utilized to obtain metals of high purity. Below is a list of a few of them
- Distillation
- Liquation
- Electrolysis
- Zone refining
- Vapour phase refining
- eChromatographic methods
Distillation
For low-boiling metals like zinc and mercury, this is quite helpful. To obtain the pure metal as distillate, the impure metal is evaporated.
Liquation
Using this technique, a low melting-point metal, such as tin, is forced to flow along an inclined surface. It separates from the higher melting impurities as it passes through the sloping surface.
Electrolytic refining
The impure metal serves as the anode in this process. The cathode is a strip of the same metal in its purest form. They are placed in an appropriate electrolytic bath that has soluble metal salt in it. Less basic metals end up in the anode mud while the more basic metals stay in the solution.
The responses are
Anode: M M n + ne
Cathode : M n + +ne M
Zone refining
This method is based on the idea that impurities are more soluble in the metal’s melt than in its solid state.
Vapour phase refining
This process breaks down the metal into its volatile component. After that, it breaks down into pure metal. The two prerequisites are as follows:
- The metal should combine with an accessible reagent to generate a volatile chemical.
- The volatile ingredient needs to break down quickly so that recovery is simple.
Mond Nickel Refining Procedure
This procedure involves heating nickel while a stream of carbon monoxide is present, creating the volatile complex nickel tetracarbonyl.
Ni+4CO becomes Ni(CO)4 at 330–350K.
The carbonyl is heated to a higher temperature, where it disintegrates to produce pure metal.
Ni(CO) 4 = Ni + 4 CO at 450 to 470 K
Zirconium or Titanium Refining Process by Van Arkle:
Chromatographic techniques
The idea behind these techniques is that different parts of a mixture will adsorb on an adsorbent in various ways.
A liquid medium is used to transport the mixture through the adsorbent. On the column, various components are adsorbed at various depths. Later, using the appropriate solvents, the adsorbed components are eliminated.
Column chromatography after the jump, In this procedure, an Al2O3 column is created in a glass tube, and the moving medium contains a liquid solution of the component parts. This is especially helpful for purifying elements that are only found in trace amounts and whose impurities have many chemical characteristics with the element that needs to be purified
Metals’ Uses:
Aluminum Uses
- Food ingredients are wrapped in aluminium foil.
- Paints and lacquers employ the metal’s fine dust as an ingredient.
- Chromium and manganese are also extracted from their oxides using aluminium.
- Aluminum wires are employed as electrical conductors.
- Aluminum alloys are extremely valuable since they are lightweight.
Copper Uses
- It is utilized to create steam pipes and electrical wiring.
- Additionally, it is utilized in alloys for coins, bronze, and brass.
Zinc’s Functions
- Iron is galvanized using it.
- It’s applied in cells.
- Brass and germane silver are two alloys that include zinc.
- Utilized as a reducing agent is zinc..
Iron’s Uses
- It is used to create tools and machines as well as cars, ship hulls, building structural components, bridges, and aircraft.
- Steel is made from iron and is frequently used in industrial and civil engineering.
- Hospital equipment is also made of stainless steel, which is widely used in kitchenware, appliances, and cookware due to its great corrosion resistance.
