Hydrometallurgy

Hydrometallurgy involve the use of aqueous solutions for the recovery of metals from ores, concentrates, and recycled or residual materials.

[1][2] Processing techniques that complement hydrometallurgy are pyrometallurgy, vapour metallurgy, and molten salt electrometallurgy.

Hydrometallurgy is typically divided into three general areas: Leaching involves the use of aqueous solutions to extract metal from metal-bearing materials which are brought into contact with them.

[5] The lixiviant solution conditions vary in terms of pH, oxidation-reduction potential, presence of chelating agents and temperature, to optimize the rate, extent and selectivity of dissolution of the desired metal component into the aqueous phase.

In solvent extraction this mixture is often referred to as the "organic" because the main constituent (diluent) is some type of oil.

The PLS (pregnant leach solution) is mixed to emulsification with the stripped organic and allowed to separate.

When dealing with electrowinning, the loaded organic is then mixed to emulsification with a lean electrolyte and allowed to separate.

The main types of metal recovery processes are electrolysis, gaseous reduction, and precipitation.

Precipitation will proceed when, through reagent addition, evaporation, pH change or temperature manipulation, the amount of a species present in the solution exceeds the maximum determined by its solubility.