Cleaning Up

Biomining and Cleaning Up

Apart from Gold, Copper and Silver, companies have attempted to extract other metals from a low-grade ore using biomining. They include Zinc, Cobalt, Uranium and Nickel. Also, they are often mined at low concentration.

The metals can also be located in rocks and thus, can be extracted through bioleaching as well. A classic example is an experience at the Talvivaara mine in Finland, where Nickel and Zinc were discovered and removed from a schist through heap bioleaching. Talvivaara mine has mined over twenty-six tons of minerals (nine thousand tons of Nickel and seventeen tonnes of Zinc) barely four years after they started operations.

The metals may be present in the rock as sulphides or oxides, depending on the geographical locations. However, some are included within oxides and pose a severe threat to metal extraction through the conventional method. On the other hand, a group of biotechnology researchers devise a means using microbes to break through the oxides to collect the metals.

The same microbe utilised during a traditional biomining is used but does not involve oxygen except during anaerobic situations. In the latter case, the microbes facilitate the oxidation of sulphuric compounds in rocks using oxygen. For instance, they may change ferric iron to ferrous iron. The researchers used this method to extract Nickel from mineral goethite.

It is hoped that the same method works for similar oxidised situations. This discovery contributes to the list of possibilities that brightens the future of biomining. For instance, one may utilise the same method to extract a type of REEs (neodymium). It is no doubt that REEs are the future of metal technologies, although it has dominated certain countries such as China.

Another function of biomining is known as Clean-up. One can utilise the processes of biomining to clean old and abandoned mines. The old mines often contain deposits of ore that was discarded for different reasons.

Johnson commented that metal contained in those waste may outnumber those yet to be extracted from the ground. Bioleaching occurs naturally with deposited old discovered mineral, which often has properties to pollute the environment. However, the processes of biomining ensure the safe extraction of metal without contaminating the environment. The common forms of biomining or bioleaching are

Heap Leaching

This process refers to gathering materials into heaps in preparation for leaching. Metals are obtained after the lapse of a specific time when one would have sprayed water-soluble containing microbes on it.

In-Situ Leaching

In this method, the mineral is in its raw state when the leaching process starts. A microbe (Thiobacillus) is used to prepare a water solution passed through an already drilled hole in the metal ore.

Dump Leaching

Dump leaching is the methods of placing low-valued ore or waste rock in an enclosed hole and then bioleach it to collect the metals.

Agitated Leaching

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.