This set of Environmental Biotechnology Multiple Choice Questions & Answers (MCQs) focuses on “Metal Recovery by Bioleaching Process”.
1. Which commercial bioleaching processes among the following involves piling up of uncrushed waste rock?
a) In Situ
b) Dump Leaching
c) Heap Leaching
d) Vat Leaching
View Answer
Explanation: Dump leaching involves uncrushed waste rock which is piled up. It is an industrial process to extract rare metal ores or copper. This process is similar to heap leaching but in case of dump leaching the ores are taken directly from the mines.
2. What percentage of total world copper production do bioleach of copper alone contributes?
a) 10%
b) 17%
c) 25%
d) 33.3%
View Answer
Explanation: Bioleaching of copper is practiced in many countries including Australia, Canada, Chile, Mexico, Peru, Russia and the United States of America. Copper recovery from bioleaching accounts for about 25% of the world copper production.
3. The maximum temperature that may reach in the interior dump of copper bioleaching is ______
a) 120°C
b) 100°C
c) 90°C
d) 70°C
View Answer
Explanation: The maximum temperature may reach to 90°C in the interior dump of copper bioleaching. The interior of the dump consists a range of thermophilic microorganisms and it reaches a temperature of 90°C.
4. Some heterotrophic bacteria are present in the copper dumps which indirectly affect metal ________ by affecting the growth and activity of metal solubilizing _______
a) solubilization; bacteria
b) solubilization; fungi
c) activity; bacteria
d) activity; fungi
View Answer
Explanation: Some heterotrophic bacteria indirectly affect metal solubilization by affecting the growth and activity of metal solubilizing bacteria. Metal solubilization is one of the main factors of activity and growth and most of the leaching of copper includes strains of bacteria and not fungi.
5. Which of the following mechanism is used for bioleaching of uranium?
a) Direct Leaching Mechanism
b) Indirect Leaching Mechanism
c) Acid Leaching Mechanism
d) Alkali Leaching Mechanism
View Answer
Explanation: Bioleaching of uranium is only done by indirect mechanism. Indirect mechanism is used as Acidithiobacillus ferrooxidans does not directly interact with uranium minerals.
6. Acidithiobacillus sp. is used to extract what kind of metal ore?
a) Oxide
b) Carbonate
c) Silicate
d) Sulphate
View Answer
Explanation: Sulphate ores are extracted with the help of Acidithiobacillus species. In case of oxide, carbonate and silicate, Acidithiobacillus sp. cannot be used as it lacks the ability to extract the metal.
7. Which leaching agent is used for the slow decomposition of refractory gold ores?
a) Nickel
b) Sulphur
c) Cyanide
d) Molybdenum
View Answer
Explanation: Cyanidation process is used to help the refracted gold ores to decompose slowly. Cyanide is used as it binds easily with gold ores and makes it soluble in water and this allows the gold to separate from rock.
8. In the studies of Joffe and Sperll, it was observed that ________ is efficient for solubilizing Ni but the presence of ______ had adverse effect on leaching.
a) T. ferrooxidans; cobalt
b) T.trioxidanes; molybdenum
c) T. ferrooxidans; molybdenum
d) T. trioxidanes; cobalt
View Answer
Explanation: T. ferrooxidans is efficient for Ni recovery but the presence of Mo makes it difficult. To overcome this, a mixture of heterotrophic denitrifying bacteria is used to effectively leach both nickel and molybdenum.
9. Which type of ore is the major source of nickel?
a) Oxide
b) Sulfide
c) Carbonate
d) Ferrous
View Answer
Explanation: Sulfide till date has been the most important and majorsource ore for nickel. Oxide often has minimum amount of nickel, cobalt and chromium. Carbonate and ferrous is not at all used as a nickel source.
10. Bacterial leaching is possible with low concentrations and requires little energy inputs.
a) True
b) False
View Answer
Explanation: Traditional methods of leaching like smelting and roasting require high concentration of ores and is also expensive. While bacterial leaching is possible with low concentrations and requires little energy inputs. Bioleaching is also environment friendly and also the extraction yields over 90%.
Sanfoundry Global Education & Learning Series – Environmental Biotechnology.
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