Metal Extraction: Hydrometallurgy and Electrometallurgy (Module 1-6)

Question 1

Also called Hydrometallurgy

Answer 1

Aqueous solution processing

Question 2

It is concerned with the production of metals or metallic compounds from ___ and ___ wherein the chemical reactions involved are carried out in aqueous solutions at a specific temperature and pressure.

Answer 2

ores and metal scraps

Question 3

What is the usual temperature and pressure of hydrometallurgy?

Answer 3

<300 deg. Celsius and <300 psi

Question 4

What are the general steps in hydrometallurgy?

Answer 4

1. Leaching
2. Solution purification and concentration
3. Metal winning

Question 5

What are the two general types of leaching?

Answer 5

1. Concentration leaching
2. Separation leaching

Question 6

What are the common types of leaching?

Answer 6

1. In situ
2. Dump (Percolation leaching)
3. Heap (Percolation leaching)
4. Agitation
5. Pressure leaching

Question 7

It is the use of an aqueous solvent in the dissolution of the ore or some minerals in the ore.

Answer 7

Leaching

Question 8

In this general type of leaching, the desierd mineral/metal is dissolved

Answer 8

Concentration leaching

Question 9

In this general type of leaching, undesirable mineral or constituent is removed or dissolved; residue removed is the valuable product.

Answer 9

Separation Leaching

Question 10

This is the solution used to dissolve the minerals.

Answer 10

Lixiviant

Question 11

This common type of leaching is done in place where lixiviant is directly introduced to the ore deposit.

Answer 11

In-situ Leaching

Question 12

In In-situ leaching, the enriched solution is also called ____?

Answer 12

Leach Liquor

Question 13

In this common type of leaching, the run-of-mine ores are collected and dumped in an identified location.

Answer 13

Dump Leaching

Question 14

In this common type of leaching, the lixiviant is sprayed over the dump, percolates, and the leach liquor is collected at the base of the dump.

Answer 14

Dump Leaching

Question 15

In this common type of leaching, ore is piled into smaller heaps on the ground which underwent surface preparation.

Answer 15

Heap Leaching

Question 16

In this common type of leaching, the lixiviant is sprayed over the heap, percolates and the leach liquor is collected at the collection ditch at the base.

Answer 16

Heap Leaching

Question 17

This common type of leaching involves mixing ground and classified ore with the leach solution in agitation tanks.

Answer 17

Agitation Leaching

Question 18

Agitation in agitation leaching enhances what by increasing contact frequency of the lixiviant with unreacted minerals?

Answer 18

Reaction Kinetics

Question 19

This common type of leaching involves mixing ground and classified ore with the leach solution in pressure vessels (autoclaves)

Answer 19

Pressure Leaching

Question 20

Temperature and pressure of what range are achievable in pressure leaching?

Answer 20

> 200 deg Celsius and >20 atm

Question 21

Reaction kinetics is fastest in what common type of leaching?

Answer 21

Pressure Leaching

Question 22

This involves the removal of the undesirable constituents in the leach liquor (or pregnant solution) and preconcentration of the metal in the solution.

Answer 22

Solution purification and concentration

Question 23

What are the two methods under solution purification and concentration?

Answer 23

a. Ion Exchange
b. Solvent Extraction

Question 24

This method uses synthetic polymeric resins designed to exchange ions for ions in solution.

Answer 24

Ion Exchange

Question 25

In this method, a distributive process wherein the valuable metal is allowed to partition itself between two immiscible phases.

Answer 25

Solvent Extraction

Question 26

In ion exchange, what type of solution is produced after the sorption process in which dilute pregnant solution was subjected to?

Answer 26

Barren Solution

Question 27

(In ion exchange) After the sorption process, the ions are flooded with stripping solution, which then produces what solution?

Answer 27

Enriched pregnant solution

Question 28

In solvent reaction, the two main processes are ____ and ____.

Answer 28

Extraction and Stripping

Question 29

What are the two methods under metal winning?

Answer 29

a. Precipitation b. Electrolytic Deposition

Question 30

What are the three types of precipitation under metal winning?

Answer 30

a. Recrystallization b. Precipitation with gases c. Precipitation by metals

Question 31

This method uses electrons for the reduction of metal ions

Answer 31

Electrolytic Deposition

Question 32

The recovery of Ni and Co uses precipitation with what gas?

Answer 32

H2S

Question 33

In precipitation with H2S, the H2S generator is usually connected with what process?

Answer 33

Precipitation

Question 34

In precipitation with H2, cobalt is usually converted from ___ to ___.

Answer 34

from 3+ to 2+

Question 35

In pyrometallurgy, copper is usually extracted between ____ wt% copper, whereas in hydrometallurgy, it is extracted between ___ wt% copper.

Answer 35

20-35 0.6-8.0

Question 36

T/F: The choice between pyro and hyrometallurgy also depends on the amenability of dissolving tha valuable mineral using available solutes.

Answer 36

False. Available solvents.

Question 37

T/F: One downside of pyrometallurgy is the presence of volatile toxic elements upon melting such as As, Sb, Pb, and Hg.

Answer 37

True

Question 38

T/F: Another factor in choosing between pyro- and hydrometallurgy is the cost of minng and bringing the ore to the surface.

Answer 38

True

Question 39

It is also called electrometallurgical extraction.

Answer 39

Electrometallurgy

Question 40

It involves the electrolysis or decomposition of either an aqueous solution of a fused salt (molten salt) by the passage of an electric current.

Answer 40

Electrometallurgy

Question 41

T/F: Electrometallurgical processes can be divided into two.

Answer 41

True

Question 42

There are electrometallurgical processes conducted at high temps and include production by electrolysis of metals such as ___ and ___ from their fused salts.

Answer 42

aluminum and magnesium

Question 43

There are electrometallurgical processes carried out below ____ deg. Celsius using aqueous solutions and include electrolytic extraction (also known as _____) and refining as well as electroplating.

Answer 43

70 electrowinning

Question 44

Electrowinning uses ___ anode while electrorefining uses ____ anode.

Answer 44

inert soluble

Question 45

T/F: Cathode is always oxidized.

Answer 45

False. Cathode is always reduced.

Question 46

Anode reactions depend on the electrolyte used and whether the anode is ____ or ____.

Answer 46

soluble or inert

Question 47

T/F: Anodes are usually made of mixed metal oxides (MMO)

Answer 47

True

Question 48

What is the goal of electrowinning?

Answer 48

Extract the desired metal from the solution

Question 49

In electrorefining, the soluble anode consists of ____ metal to be refined.

Answer 49

impure

Question 50

In electrorefining, electrolyte consists of an aqueous solution of a ___ of the metal being refined.

Answer 50

salt

Question 51

In electrorefining, anode ___ is produced

Answer 51

mud