biolixiviatie

Biolixiviatie is the Dutch term for bioleaching, a process that uses microorganisms to mobilize metals from ores or mine wastes by oxidizing sulfide minerals or reduced sulfur compounds. It is commonly applied to copper sulfide ores and tailings, especially when ore grades are too low for conventional mining and smelting. The method is implemented mainly in heap leaching and in stirred-tank reactors.

The mechanism relies on chemolithoautotrophic bacteria such as Acidithiobacillus ferrooxidans, Acidithiobacillus ferrivorans and Leptospirillum ferrooxidans. These microbes oxidize ferrous iron (Fe2+) to ferric iron (Fe3+) and oxidize reduced sulfur compounds to sulfate. The ferric iron and the acidic environment chemically or biologically dissolve metal sulfides (for example chalcopyrite), releasing metal ions into solution and generating sulfuric acid, which helps sustain leaching. Oxygen supply, nutrients, temperature control and pH management are important to maintain microbial activity.

Process and operation typically involve grinding the ore to a small particle size, then placing it in heaps or feeding it to tank reactors. The microbial culture is introduced, and conditions are kept acidic (pH around 1–3) with adequate aeration and nutrients. After leaching, the pregnant leach solution is processed to recover the metal by precipitation, solvent extraction, or electrowinning.

Applications and limitations: bioleaching is widely used for copper recovery from sulfide ores and low-grade stockpiles; it is also explored for nickel, cobalt and other metals in sulfide minerals and tailings. Advantages include lower energy use and reduced greenhouse gas emissions compared with smelting, but drawbacks include slow kinetics, sensitivity to ore composition and environmental conditions, and the need for careful management of acidic effluent to avoid acid mine drainage.