This set of Extractive Metallurgy Multiple Choice Questions & Answers (MCQs) focuses on “Purification of Leach Liquor”.
1. Which of the following is the immediate process after leaching?
a) Separation of solids
b) Purification of leach liquor
c) Addition of solids to the leach liquor
d) Bacterial leaching
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Explanation: After performing a leaching process, the solids are separated from the leach liquor. This process is followed by the purification of leach liquor. Separation is done using some common processes like sedimentation, filtration, decantation etc.
2. Which of the following process cannot be applied for the purification of leach liquor?
a) Precipitation
b) Ion-exchange
c) Fractional distillation
d) The Service Provider
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Explanation: Purification of leach liquor is done to remove the impurities and the undesired solutes from it. Purification can be done using three different processes – Precipitation, Ion-exchange process and solvent extraction.
3. Leach liquor can be purified through precipitation under controlled conditions of pH.
a) True
b) False
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Explanation: Under controlled conditions of pH concentration, leach liquor can be purified through precipitation. It can also be purified using some special additives. Analytical chemistry is made use in these reactions.
4. What is brought in contact with leach liquor during the ion exchange process?
a) Inorganic resin
b) Organic resin
c) Metallic salt
d) Non-metallic salt
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Explanation: During Ion-exchange process, Leach liquor comes in contact with an organic resin. This organic resin contains an active compound which exchanges a radical with an anion in the solution. Impurities are mostly cations. Leaching of uranium ores is done like this using sulphuric acid.
5. What is the difference in Ion-exchange and solvent extraction process?
a) In Solvent Extraction, the inorganic resin is used
b) In Solvent Extraction, the solution is heated
c) In Solvent Extraction, organic liquid is used
d) In ion-exchange process solution is heated
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Explanation: Solvent extraction process is very much similar to Ion-exchange process. The only difference in solvent extraction is the use of organic liquid instead of resin. This is the reason it is also known as liquid-liquid extraction. A very common solvent is kerosene containing EHPA.
6. Why is the solvent extraction process more commonly used than ion-exchange process?
a) It is faster
b) It is slower
c) It heats the final solution
d) It involves liquid and not ion
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Explanation: Solvent extraction process is faster than the ion-exchange process. It uses two liquids to agitate and accelerate the transfer of metallic values from one phase to another. Effectively it is carried out by agitating two liquids together. This is the reason solvent extraction is more commonly used than ion-exchange process.
7. Why is the thermodynamic equilibrium of the ion-exchange process necessary?
a) The reaction takes place far away from equilibrium
b) The reaction takes place near-equilibrium
c) Reaction is reversible
d) Reaction is exothermic
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Explanation: Thermodynamic equilibrium of not only ion-exchange but also solvent extraction is necessary. The reaction for both the processes is irreversible. These reactions also take place near equilibrium. Therefore, the equilibrium distribution of soluble species among the phases is important.
8. Between which of the following liquids does the mass transfer across the interface occurs during solvent extraction?
a) Two similar liquids
b) A liquid and a resin
c) A liquid and a solid
d) Two dissimilar liquids
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Explanation: In the solvent extraction process, mass transfer across the interface takes place between two dissimilar liquids. The liquids agitate to accelerate the transfer of metallic values.
9. What is the ratio of the concentration of a solute in two phases referred to as in equilibrium?
a) Extraction coefficient
b) Solvent extraction
c) Extraction factor
d) Solvent coefficient
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Explanation: At equilibrium, the ratio between the concentrations of solute in two phases is called the extraction coefficient. It is expressed as E(o/a) = Cio/Cia. In the expression ‘o’ and ‘a’ refers to organic and aqueous phase respectively.
10. Extraction factor is the measure of the distribution between the densities of the phases.
a) True
b) False
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Explanation: The given statement is incorrect. Extraction factor is the term used for the quantity to measure the distribution between the volumes of the phases which are actually used. It is defined as
Ef = (VoCio) / (VaCia).
11. When is the solvent extraction process more effective?
a) Extraction coefficient is low
b) Extraction factor is low
c) Extraction coefficient is high
d) Va/Vo ratio is high
View Answer
Explanation: The solvent extraction process is very effective when the extraction coefficient is high. The separation will take place easily and effectively when the extraction coefficient is high or the extraction factor is high. It can also be enhanced by multiple contacting. Extraction factor and extraction coefficient are related to each other as Ef = (Vo/Va). E(o/a).
Sanfoundry Global Education & Learning Series – Extractive Metallurgy.
To practice all areas of Extractive Metallurgy, here is complete set of Multiple Choice Questions and Answers.
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