Bioleaching Definition & Process

What is bioleaching or biomining?

Bioleaching (or biomining) is a process in mining and biohydrometallurgy (natural processes of interactions between microbes and minerals) that extracts valuable metals from a low-grade ore with the help of microorganisms such as bacteria or archaea.

Bioleaching techniques are often more effective than traditional mining applications and can even be used to clean mine tailings sites.

Metals extracted from bioleaching include:

• Gold
• Copper
• Silver
• Cobalt
• Uranium
• Zinc
• Nickel

How does the bioleaching process work?

There are many types of bioleaching processes, and copper is the most common. A few of the most popular types of bioleaching extract metals from ore by retrieving sulfide minerals using bacteria that receive energy from non-carbon compounds.

Below are a few approaches to bioleaching:

Direct v. Indirect Bioleaching

Direct bioleaching uses minerals that are easily receptive to oxidation to create a direct enzymatic strike using the microorganisms to separate the metal and the ore.

In indirect bioleaching, microorganisms are not in direct contact with minerals during the process. However, leaching agents are created by microbes, which still oxidise the ore.

Some advantages of bioleaching include:

• Bioleaching can stabilise sulphate toxins from the mine without causing harm to the environment.
• Poisonous sulfur dioxide emissions harm the environment and can cause health problems for miners, and bioleaching avoids this process entirely.
• Bioleaching is more cost-effective than smelting processes.
• Some Bioleaching offers a different way to extract valuable metals from low-grade ores that have already been processed.

The Commercial Process

Commercial metal extraction is a quicker process that can be optimized through humidity, potential hydrogen (pH), temperature, and chemical elements.

The 3 most common commercial biomining processes are:

1. Slope Leaching

Fine ore is kept in a large, slope-shaped dump. During slope leaching, a water solution made of inoculum is continuously sprayed over the ore. After that, the leach liquor (or remaining liquid) is gathered at the bottom and processed for supplemental metal recovery.

2. Heap Leaching

In this technique, the ore is arranged in large heaps. During heap leaching, an aqueous mixture of microorganisms is sprinkled over the leach pile. Then, the solution is collected and processed to help recover even more metal.

3. In-situ Leaching

The ore remains in its natural state while the leaching process takes place. Water that contains thiobacillus is pushed through drilled passageways within the ore. The leach fluid is then stored until it is time for metal recovery.

What's next for bioleaching?

The world of tomorrow relies on how we produce the global demands of today. As technology continues to progress, there will be more room for improvements in how the industry works.