User:Ruppryan/sandbox

General Overview:
The field of biometallurgy is incredibly vast, containing a large variety of different techniques and aims within its scope. Anything involving the interactions between microorganisms and metals can be considered a part of biometallurgy. It is a very important field in the world today, as the production of many new low-carbon technologies require, to some degree, a critical metal to function. The ones that are mainly focused on, due to their high demand, are the Platinum Group Metals (PGMs) and the Rare-Earth Elements (REEs). Currently, the two most well studied, and most often used examples of biometallurgy are bioleaching and bioremediation. The former, also sometimes called biomining, is targeted at using microorganisms in order to recover the metals in material that would otherwise simply be considered waste, such as the waste water generated from some types of mining. Normal methods are unable to recover the trace amounts of metal in the waste water, but a biotechnological approach using biomining can. Not only is it helpful when recovering metals, bioleaching is also useful in the direct extraction of metals from ore deposits. While biomining can mostly be considered using microorganisms for profitable metal recovery, bioremediation is aimed at the recovery of contaminated sites. There are many types of production that will result in a hazardous waste product being generated, which would normally take a very long time to disperse of without intervention. Using an appropriate organism, things such as heavy metals and radionuclides that contaminate an area can be neutralized or even completely removed. These two subcategories are far from the limit as well; the potential of the field will only continue to grow from here as more advanced biotechnological techniques become available for real-world application.

Bioleaching and Biomining:
Strictly speaking biomining and bioleaching can be defined as two similar parts of the same overall field. Bioleaching specifically refers to the process by which a metal is solubilized before processing occurs. This contrasts with Biomining, which is a much more generalized term involving all processes that involve the extraction and eventual recovery of metals using the biological systems of microorganisms. However, oftentimes these two terms are synonymized to the same definition, and it is important to acknowledge this distinction. Internationally, the process of biomining is used to extract copper sulfides as a pretreatment before the extraction of gold ores, while also being used to recover cobalt, nickel and zinc. As a matter of fact, roughly 5% of the globally available gold and up to 15% of the supply of copper worldwide comes from technology involving biomining. In regards to the process itself, it does not involve the use of engineered microorganisms. The environment which would necessitate the use of biomining actually restricts the use of bioengineered organisms. The vast majority of the technology used today involves the utilization of acidophilic prokaryotes that are capable of tolerating the low pH and elevated levels of toxic metals inherent to bioleach liquors. Specifically, the process focuses on microorganisms that are inherently able to oxidize iron in order to generate ferric iron and sulfuric acid. The benefits of this being that it creates an environment where these organisms thrive, while simultaneously accelerating mineral dissolution. Another crucial part of this process is that the incredibly acidic environment retains any metals that are released from the ores in the solution. When putting this technique to use, the waste material being mined is often stacked into an enormous heap, before acidophilic bacteria are introduced at regular intervals, and then “watered” with a dilute sulfuric acid solution. The solvent draining off these heaps is then collected and processed to extract the metals contained within.

Bioremediation:
An application of Biometallurgy that isn't necessarily focused on profitable recovery of precious metals, but is instead aimed at using microorganisms for environmental clean up, due to their innate heavy metal resistance.

(Insert Link to Bioremediation Page)

Biosorption:
As opposed to some of the other forms of Biometallurgy, the techniques of Biosorption are focused on the recovery of metals that are present in aqueous solutions. One of the major reasons it is being looked at is as an alternative to traditional methods of hydro-metallurgical, and pyro-metallurgical methods, which include techniques such as adsorption through ion-exchange resin, solvent extraction and using reagents to reduce precious metal precipitate. While the methods employed greatly vary, the biggest drawback for all of them is the large cost, labor and amount of time needed to employ them. Often times, there is also a large quantity of secondary waste generated as well. Biosorption on the other hand, presents a cheap and eco-friendly alternative that makes use of bacteria, fungi, algae, actinomycetes, and yeasts. The mechanism used for Biosorption takes place in the cell wall and is completely separate from the cells metabolic processes. This means that it is also possible to use a large amount of dead biomass for metal recovery, further reducing the cost of the process and also allowing it to take place in environments that may normally be too extreme for the microorganism being employed (such as high toxicity). The process can be considered very efficient: in a study using the red algae Galdieria sulphuraria to recover aqueous gold and palladium from waste water, over 90% was successfully recovered.

Additional Resources:

 * Min Gan, Shiqi Jie, Mingming Li, Jianyu Zhu, Xinxing Liu - Bioleaching of multiple metals from contaminated sediment by moderate thermophiles. Marine Pollution Bulletin. Volume 97, Issues 1–2, 15 August 2015, Pages 47-55
 * Xiaoqi Li, Delong Meng, Juan Li, Huaqun Yin, Hongwei Liu, Xueduan Liu, Cheng Cheng, Yunhua Xiao, Zhenghua Liu, Mingli Yan - Response of soil microbial communities and microbial interactions to long-term heavy metal contamination. Environmental Pollution. Volume 231, Part 1, December 2017, Pages 908-917
 * Justin A. Bogart, Connor A. Lippincott, Patrick J. Carroll, and Eric J. Schelter - An Operationally Simple Method for Separating the Rare-Earth Elements Neodymium and Dysprosium