Scope of Biomining For extraction of metals from minerals in space

by Tryammbak Kansal, Taha Ali Khan, Shubhjeet Singh

Biomining can be defined as the process which is used to extract metal from minerals with the help of microorganisms. Different types of microorganisms used for this purpose are autotropic, Fe-, S-oxidizing microorganisms. They generally produce ferric iron and sulfuric acid to covert insoluble metal sulfides(or oxides) to water-soluble metal sulphate for e.g- conversion of (Cu2S) to soluble copper sulphate. Similar chemicals can also be used as a pretreatment process to penetrate the structure of a mineral therefore allowing chemicals to have better penetration. When vital metal is recovered into a solution, it is known as bioleaching(or biomining).

Biomining can be done with the help of reactors as it would require a continuous supply of aeration for the proper growth of microorganisms to the process more efficiently. This process seems to be a domain of chemistry rather than biology at first glance but we need microorganisms to produce leaching chemicals so that process can go on. Moreover, microorganisms produce an exopolysaccharide layer which serves as a reaction place that gets attached to the mineral. Extraction of metals such as copper, gold mainly uses this method on a commercial scale. This process can also be used for the extraction of uranium and rare earth metals which are not so easy to extract. Biomining was demonstrated in ISS to have a better understanding of how this process will happen in micro-gravity and low temperature. They used bacteria such as (S. desiccabilis, B. subtilis, C. metallidurans) to do biomining. These bacterias were selected as they can survive low temperatures and will require very fewer nutrients and water. These bacterias also have a risk level 1 so that it won't harm any astronauts and scientists even used a fixative to stop the process wherever they want to. The mineral used for this experiment was "Basalt" which is present in abundance in both moon and mars and contains rare earth metal. A specialized Biomining reactor was used to carry out an experiment in ISS. Experiment results showed that there was statistically no difference in the growth rate of all 3 microorganisms though Sphingomonas desiccabilis enhanced the leaching concentration of metal. It should be noted that Basalt rock wasn't crushed and the reactor wasn't stirred. These factors play a major role as they enhance the leaching process.

Hence the above-conducted experiment done in ISS validated that it is possible to do biomining in the microgravity of different celestial bodies such as the moon and mars at a viable cost.

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