hydrometallurgisissa

Hydrometallurgisissa is a Finnish term referring to hydrometallurgical processes. Hydrometallurgy is a branch of extractive metallurgy that utilizes aqueous chemistry to recover and purify metals from ores, concentrates, and recycled or residual materials. This contrasts with pyrometallurgy, which uses high temperatures.

The key steps in hydrometallurgical processes typically include leaching, solution purification, and metal recovery. Leaching involves dissolving the desired metal from the solid material into an aqueous solution using lixiviants such as acids, bases, or salts. Common lixiviants include sulfuric acid for copper and uranium, cyanide for gold and silver, and ammonia for nickel and copper.

Following leaching, the pregnant leach solution, which contains the dissolved metal, undergoes purification. This stage aims to separate the target metal from impurities. Techniques employed include solvent extraction, ion exchange, precipitation, and membrane filtration. Solvent extraction involves transferring the metal ions from the aqueous phase to an organic phase. Ion exchange uses resins to selectively adsorb metal ions. Precipitation removes impurities as solid precipitates.

Finally, the purified metal is recovered from the solution. Common recovery methods include electrowinning, where an electric current is used to deposit the metal onto a cathode, and precipitation, where the metal is precipitated as a solid compound, often followed by smelting or refining. Cementation, where a more reactive metal displaces the target metal from solution, is another recovery method. Hydrometallurgy is widely used for the extraction of copper, gold, silver, nickel, cobalt, zinc, and uranium, and is increasingly important for recycling electronic waste and recovering valuable metals from secondary sources.