BIOMINING RAWLINGS PDF
Biomining-A useful approach toward metal extraction Abstract: Biomining is the extraction of specific metals from their ores through .. Rawlings, D.E., Biomining [Douglas E. Rawlings, D. Barrie Johnson] on *FREE* shipping on qualifying offers. Biomining uses microorganisms to recover metals, . Editorial Reviews. From the Back Cover. Biomining is the biotechnology that uses Biomining – Kindle edition by Douglas E. Rawlings, D. Barrie Johnson.
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Copper has been one of mankind’s most important metal resources since the beginning of civilization, and to this day it holds and important role in the functioning of modern society. It’s main uses include piping, coinage, electronics, and even antibiotics Wikipedia: Inglobal copper consumption topped 21 billion tons Copper Development Associationand that kind of demand has led to the development of sophisticated mining techniques. biomniing
Copper is rarely found in its native form; most often it exists as ores made up of various copper sulfides and oxides that have little practical value of their own Australian Atlas of Minerals, Resources, and Processing Centres.
As such, methods for mining copper involve long and complex chemical processes to produce metal from the ores.
This involves using harsh chemical reagents to pull the ore from the rock, and subsequent treatment to further isolate the metal and extract pure copper. These processes are energetically expensive, and they create a significant amount of pollutant chemicals such as sulfur dioxide and cyanide Copper Mining Info .
A viable alternative to these harmful procedures is biomining, or the use of bacterial metabolic processes to assist in the solubilization of metal ores. They grow in subterranean mineral deposits and even sewer pipes Slonczewski and Fosterand their activity has been linked to the processing of mineral ores Rawlings Modern biomining processes are large-scale operations that involve the mining of ores and processing for several months Fig.
Either through strip-mining or blasting, raw ore is obtained for extraction of copper. The ores obtained from mining are crushed and piled up to 10 meters high atop plastic irrigation pads, whereupon water seeded with acid, called the lixiviant, is irrigated through the heaps and collected Fig. After performing the next steps to extract the copper dissolved in the leach liquor, it is recycled and used to irrigate the heap again Rawlings The isolation of copper metal from leach liquor is a two-step process Wikipedia: Copper Extraction Techniques .
The leach liquor obtained after heap irrigation has a very low concentration of copper dissolved into it, around 0. Through solvent extraction, the copper is transferred from the dilute liquor to a more concentrated solution. Afterward, the dissolved copper ions are transformed to solid copper metal through a process called electrowinning that uses an electric current to reduce the dissolved metal and deposit it onto a cathode, at which point the solid elemental copper metal can be employed for its many uses Siddiqui et al.
There has been much debate over how At. Although it has been proposed that the bacterium produces enzymes which directly mediate the reaction, studies have shown that iron is the only metal ion used to produce energy Mignone and Donati Copper is not a metabolite of At. Rather, it occurs through an abiotic reaction between the copper ores and the ferric ions and protons produced by the metabolic activities of the bacteria.
These reactions regenerate the reduced iron and sulfur compounds that the bacteria reuptake to start the cycle anew.
These respiratory pathways produce the reactive species that initiate mineral solubilization Leduc and Ferroni Copper sulfide ores are solubilized in a reaction where ferric iron complexed with sulfate dawlings the copper compounds and becomes reduced to ferrous iron while generating copper sulfates and elemental sulfur Hutchins et al. Copper oxides like azurite are somewhat less susceptible to attack by ferric iron; however, they are highly soluble in the low-pH solution produced by the bacterial production of sulfuric acid Iasillo This cycling of iron and sulfur maintains an energetically favorable situation for the bacteria; any ralwings iron or sulfuric acid produced tends to undergo reduction with mineral ores to be subsequently re-oxidized by At.
This cycling does not occur in a free-floating environment, however; the bacteria produce an extracellular biofilm made of polysaccharides and lipids which binds them to the mineral substrate and retains the iron and sulfur compounds as they go through the redox cycle Fig.
The biofilm also helps to retain the bacterial cultures in heaps during irrigation Sand and Gehrke A study done on the copper solubilizing activity of At.
The reason for this increased activity is connected to the D strain’s resistance to sulfite SO 3 2-a toxic intermediate in sulfur oxidation.
Sulfite hinders the activity of iron oxidase, an important enzyme in the bacterium’s iron oxidation pathway which provides ferric ions for the solubilization of sulfides Sugio et al. Most organisms including At. However, the D strain has a sulfite reductase that is more resistant to sulfite and thus can oxidize it faster, resulting in a lowered sulfite concentration that doesn’t inhibit the iron oxidation pathway Sugio et al.
One cause for concern regarding the bikmining of the process in regards to the organism is the makeup of the microbial community in a heap reactor. Studies on the composition of the bacterial community have showed that under lower-nutrient conditions and in the presence of certain toxic metals such as arsenic At. This is problematic because the metabolic activities of these other species do not produce the ferric ions responsible for solubilizing copper sulfates.
Improvement of the nutrient conditions in the heap reactor can increase the At. A more inexpensive and immediately practical way than genetic modification to improve biomining is through optimization of industrial techniques. In situ biomining does away biommining the ore mining process altogether; acidified leach liquor is pumped directly into the ground and the copper is solubilized utilizing preexisting bacteria in the ore deposits.
Biomining – Google Books
The copper-rich liquor is extracted from wells dug beneath the deposits Rawlings By eliminating the physical act of ore mining, a significant portion of the costs is cut from the process. Bioming has proved to be a cheaper, more efficient, and more environmentally-friendly alternative than non-biologically mediated techniques for copper mining, and the chemolithotrophic bacteria At.
Much research is still underway to develop improvements, and future applications have included using biologically-engineered bacteria to mine extraterrestrial bodies such as the moon and large biomiing Ragozzine Whatever directions biomining will take in the future, it will doubtlessly prove to be immensely beneficial in a future with dwindling resources.
Retrieved April 30, Iasillo E Metallurgical test program for copper leaching projects.
Biochemical Engineering Journal In Biohydrometallurgy and the Environment Towards the 21st Century. Part Aed. Amils R and Ballester A.
Copper Mining Using Acidothiobacillus
Elsevier Rawlings DE Heavy metal mining using microbes. Research in Microbiology A useful approach toward metal extraction. American-Eurasian Journal of Agronomy 2 2: Applied and Environmental Microbio. From MicrobeWiki, the student-edited microbiology resource.
The use of reactors in biomining processes | Acevedo | Electronic Journal of Biotechnology
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