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44 notecards = 11 pages (4 cards per page)

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Hydrometallurgy

front 1

HYDROMETALLURGY

back 1

Hydrometallurgy is the treatment of ores
by dissolution in aqueous solutions which
imitates natural leaching processes.

front 2

HYDROMETALLURGY | general steps

back 2

1. Comminution/mineral beneficiation of the starting material (optional)
2. Roasting (optional)
3. Leaching
4. Solid/liquid separation
5. Metal/Mineral Recovery
6. Solid/Waste treatment

front 3

Comminution/mineral
beneficiation of the starting
material (optional)

back 3

▪ to control fineness of the
feed material

front 4

Roasting (optional)

back 4

heating of ore with excess air
▪ changes structure/composition
to make metal easier to leach
by converting metal to a more
leachable form, or by modifying
matrix to make metal m

front 5

Leaching

back 5

to dissolve the valuable metal/mineral
into the leach liquor

front 6

Metal/Mineral Recovery

back 6

▪ final extraction of the metal from the solution

front 7

Solid/Waste treatment

back 7

▪ Treatment of the liquor to be recycled in the
operation
▪ Neutralization prior to disposal

front 8

LEACHING

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involves the selective dissolution of the valuable metal in a suitable
reagent or lixiviant

front 9

• Leaching Reagents also caled as

back 9

Lixiviant

front 10

LEACHING | leaching reagents/lixiviants

back 10

Water
Acids
Bases
❑ Aqueous Salts

front 11

Mineral to Lixiviant

Oxides

back 11

Dilute H2SO4

front 12

Mineral to Lixiviant

Sulfates

back 12

Dilute H2SO4 or H2O

front 13

Mineral to Lixiviant

Sulfides

back 13

FeSO4 solution

front 14

Mineral to Lixiviant

Alumina

back 14

NaOH solution

front 15

Mineral to Lixiviant

Cu/Ni compounds

back 15

(NH4)2CO3

front 16

Dump Leaching

back 16

▪ For low grade ore (sulfide and oxide)
▪ for stripped marginal materials adjacent to the
main ore body
▪ ~20 cm particles in diameter are dumped in open
pit mines and the lixiviant is fed periodically by
sprays at the top of the dump
▪ leaching time lasts for years

front 17

Heap Leaching

back 17

▪ Ore material is piled into small heaps on
impervious grounds or on a concreted or asphalted
surface with drainage channels and pipes and a
collecting pond
▪ The lixiviant is fed in the same manner as that of
dump leaching.
▪ Leaching periods extend for several months

front 18

In-Situ Leaching

back 18

“in place” leaching
▪ This involves the dissolution of low-grade surface
deposits or worked-out underground mines without
the removal of the ore from the mine.

front 19

Percolation/Vat Leaching

back 19

▪ involves the use of tanks with false bottom,
covered with filtering medium
▪ applied to porous and sandy material, about 5mm
diameter; slimes are undesirable

front 20

Agitation Leaching

back 20

▪ used to process particles <0.5mm in diameter
▪ particles are stirred in tanks to accelerate leaching process

front 21

Pressure Leaching

back 21

carried out at elevated temperatures and pressures in reaction vessels called autoclaves
▪ used to obtain solutions of minerals which are difficult to dissolve at atmospheric pressure

front 22

Bacterial Leaching

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▪ rate of solution of certain sulfides is increased with the use of microorganisms

front 23

SPC

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SOLUTION PURIFICATION AND CONCENTRATION

front 24

SOLUTION PURIFICATION AND CONCENTRATION

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Separation
Purification
Enrichment

front 25

Pregnant Solution/Pregnant Liquor

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Solution produced when valuable metal is transferred from an ore or concentrate to a solution (transfer from a solid to a liquid) as a result of leaching

front 26

Enriched Solution

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The goal of a solution purification and concentration method is to obtain an enriched solution containing a concentrated amount of the desired valuable metal.

front 27

Barren Solution

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This is the solution from which the desired valuable metal has been removed from.

front 28

Ion Exchange

back 28

▪ Metallic ions can be removed
from an aqueous solution by
ion exchange at the surface of
an organic resin

front 29

Ion Exchange involves

back 29

sorption followed by elution.

front 30

Resin

back 30

Specifically used in ion exchange are synthetic resins because of their characteristics which can be tailored to
specific applications

front 31

Eluant

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The solvent used to wash the resin which
removes the captured ions from the resin

front 32

Eluate

back 32

Solution produced from the elution process containing the captured ions

front 33

Ion Exchange | SORPTION

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resin is contained in a column and the metal rich solution is fed through it slowly enough to allow exchange to occur

front 34

Adsorption Process

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This process uses the ability or
property of certain solids to
take up ionic or molecular
substances preferentially from
fluids

front 35

Carbon-in-Leach

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▪ Carbon is added to the leach tanks (or reaction vessel) so that leaching, and adsorption take place
in the same tanks.

front 36

Carbon-in-Pulp

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Leaching takes place in tanks dedicated for leaching followed by adsorption into carbon in tanks dedicated for adsorption.

front 37

Solvent Extraction

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▪ This involves a distributive reaction wherein the valuable metal is allowed to partition itself between two (2) immiscible phases – aqueous and organic

front 38

EXTRACTION

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Process wherein the constituent of one
solution is transferred to another solution
through an interface between them

front 39

Solutions For Extraction

First

back 39

Water Solution

front 40

Solutions For Extraction

Second

back 40

Organic Solvent

front 41

STRIPPING

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Process of recovering the desired valuable
metal from the organic solvent which
produces a purified and concentrated
solution but in a way in which the organic
solvent can still be recycled

front 42

metal winning

back 42

PRECIPITATION
ELECTROMETALLURGY

front 43

PRECIPITATION

back 43

formation of a solid product
from solution, as a result of
the addition of a reagent to
the solution

front 44

ELECTROMETALLURGY

back 44

recovery and purification of metals using electrodeposition of metals at the cathode (electrowinning)