HYDROMETALLURGY

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

HYDROMETALLURGY | general steps

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

Comminution/mineral
beneficiation of the starting
material (optional)

▪ to control fineness of the
feed material

Roasting (optional)

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

Leaching

to dissolve the valuable metal/mineral
into the leach liquor

Metal/Mineral Recovery

▪ final extraction of the metal from the solution

Solid/Waste treatment

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

LEACHING

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

• Leaching Reagents also caled as

Lixiviant

LEACHING | leaching reagents/lixiviants

Water
Acids
Bases
❑ Aqueous Salts

Mineral to Lixiviant

Oxides

Dilute H2SO4

Mineral to Lixiviant

Sulfates

Dilute H2SO4 or H2O

Mineral to Lixiviant

Sulfides

FeSO4 solution

Mineral to Lixiviant

Alumina

NaOH solution

Mineral to Lixiviant

Cu/Ni compounds

(NH4)2CO3

Dump Leaching

▪ 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

Heap Leaching

▪ 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

In-Situ Leaching

“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.

Percolation/Vat Leaching

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

Agitation Leaching

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

Pressure Leaching

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

Bacterial Leaching

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

SPC

SOLUTION PURIFICATION AND CONCENTRATION

SOLUTION PURIFICATION AND CONCENTRATION

Separation
Purification
Enrichment

Pregnant Solution/Pregnant Liquor

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

Enriched Solution

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

Barren Solution

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

Ion Exchange

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

Ion Exchange involves

sorption followed by elution.

Resin

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

Eluant

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

Eluate

Solution produced from the elution process containing the captured ions

Ion Exchange | SORPTION

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

Adsorption Process

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

Carbon-in-Leach

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

Carbon-in-Pulp

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

Solvent Extraction

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

EXTRACTION

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

Solutions For Extraction

First

Water Solution

Solutions For Extraction

Second

Organic Solvent

STRIPPING

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

metal winning

PRECIPITATION
ELECTROMETALLURGY

PRECIPITATION

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

ELECTROMETALLURGY

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