Biomining .. The Latest Technologies for Gold and Metal Extraction

Biomining is the process of using microorganisms (microbes) to extract economically valuable minerals from ore rocks or mine waste. It can also be employed to remediate sites contaminated with metals

Methods of Gold and Metal Extraction

Precious metals are often associated with solid minerals. Some microbes can oxidize these minerals, allowing them to dissolve in water. This is the fundamental process behind most biomineralization operations, used for minerals that can be more easily recovered when dissolved compared to solid rocks

Different Biomining techniques are also utilized for minerals that microbes cannot dissolve, but these techniques help to break down surrounding minerals, facilitating the direct recovery of the target metal from the remaining rocks

Currently Biologically Formed Minerals

Most current biomineralization operations target precious metals such as copper, uranium, nickel, and gold, typically found in sulfide minerals. Microbes are particularly adept at oxidizing sulfide minerals and converting metals like iron and copper into more easily soluble forms

While some metals like gold are not directly dissolved through this microbial process, they have become more accessible to traditional mining techniques because the surrounding metals are dissolved and removed by microbial processes. When the target metal is directly dissolved, this process is known as “bioleaching,” and when the metal of interest is more easily accessible or “enriched” in the remaining material, it is termed “biooxidation.” Both processes involve bacterial reactions that can occur anywhere microbes, rocks, and essential nutrients like oxygen are present

Processes Used in Biomining

:The most common processes used in Biomining are

Heap Leaching: The freshly extracted materials are directly piled into heaps and then bioleached

Dump Leaching: Low-grade ore or rock waste is placed in a lined pit, and then it is bioleached to remove additional valuable minerals from the waste heap

Stirred Tank Leaching: Crushed rocks are placed in a large vessel that is stirred to evenly distribute microbes and materials, accelerating the biooxidation process

The leaching times can vary from days to months, making this process slower than conventional mineral extraction techniques. Heap and dump leaching are among the oldest and most established biomineralization techniques, but stirred tank leaching has become more common for minerals resistant to leaching, including some copper sulfides like chalcopyrite