Biomet

Bioleaching and BioMetallurgynt

Bioleaching & BioMetallurgy

BioMetallurgy is necessitated by the need to grow green low-carbon energy technologies that require certain metals, majorly PGMs (platinum group metals) and REEs (Rare earth elements). However, geopolitical differences posed difficulties during the search for metals, a problem that has attracted the combined efforts of the government and industries.

BioMetallurgy refers to the biotechnological procedures that deal with relations between living organisms and metal compounds (including ore). The process of BioMetallurgy is eco-friendly and not toxic. It uses little or no energy and can allow low concentration treatment.

BioMetallurgy deals with several concepts, among which are Biosorption and Bioleaching. The scope of BioMetallurgy includes oil recovery, microbial mining, bioleaching, waste management, waste management and metal recycling. Hence, bioleaching is a subset of BioMetallurgy.

Bioleaching

Bioleaching involves the use of microbes to obtain metals from low-valued minerals. The metals for which bioleaching could account are Nickel, Gold, Zinc, Copper, Uranium, Silver, and Cobalt. The process has proven effective and efficient over the typical method of extraction because

  • Mining regulates the release of sulphate toxins into the environment such that it causes no damage to it
  • Bioleaching avoids using sulphur dioxide because of its effects on the environment
  • Bioleaching costs less than the standard method of mining
  • It is suitable for most gravity conditions
  • It provides different ways to obtain metals from minerals

Types of Bioleaching

Slope Leaching

Before the process begins, the mineral is kept in an enclosed pit and then continuously sprayed with a solution containing inoculum. The remaining leach is collected at the bottom and utilised for metal recovery.

Heap Leaching

This process involves making materials that have just been freshly mined into vast heaps for bioleaching. A microbe solution is prepared and sprayed on the heaps. When the solution is settled and gathered, it is processed to obtain more metals.

Dump Leaching

Dump leaching is the methods of putting low-grade ore or waste rock in an enclosed hole and then bioleach it to strip the metals of the waste surrounding it.

In-situ Leaching

In this method, the mineral is in its unprocessed state when the leaching process starts. Thiobacillus is used to prepare a water solution passed through an already drilled passage in the mineral. The leaching liquid is stored then later used for metal recovery.

Agitated Leaching

As the name implies, it involves putting split rocks in a large tank or vessel and then shaking it to distribute the microbes and materials evenly and even hasten the bioleaching process.

It is pertinent to know that leaching is not an immediate process and may take up to months; hence bioleaching is slower than the standard mining method.

Furthermore, bioleaching may be direct or indirect. It is direct if the dissolution of metal from the sources by microorganisms is naturally occurring or uses ore that readily responds to oxidation. On the other hand, it is indirect if microorganisms are firstly utilised to produce organic acids or other solubilising elements (leaching agents) before oxidising the mineral.