Hydrometallurgy Flashcards

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

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

▪ to control fineness of the
feed material

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

to dissolve the valuable metal/mineral
into the leach liquor

▪ final extraction of the metal from the solution

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

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

Lixiviant

Water
Acids
Bases
❑ Aqueous Salts

Dilute H2SO4

Dilute H2SO4 or H2O

FeSO4 solution

NaOH solution

(NH4)2CO3

▪ 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

▪ 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 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.

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

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

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

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

SOLUTION PURIFICATION AND CONCENTRATION

Separation
Purification
Enrichment

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

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

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

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

sorption followed by elution.

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

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

Solution produced from the elution process containing the captured ions

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

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

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

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

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

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

Water Solution

Organic Solvent

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

PRECIPITATION
ELECTROMETALLURGY

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

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