Bioleaching - Science topic

Identifying and counting the exact number of active sites on an adsorbent can be challenging. However, several techniques can help estimate the active site density and provide valuable information about the adsorption process. Here are some common methods:

Bioleaching of WEE viability and sustainability depends on several factors: most importantly: the bioreagent that microbes produce, its concentration, pulp density and time of the process. generally, microbes are able to leach metals with much lower acid concentrations than similar chemical processes due to their fascinating live continuous factory which produces more than 200 chemical compounds, all of which can contribute to the dissolution of metals. What has been the challenge for decades for bioleaching is slow kinetic but recently researchers have found a solution that is using fast-growing bacteria that can produce organic acids, the good thing about these types of bacteria is that we already have developed biomanufacturing processes with these bacteria so adoption of technology for bioleaching will not be that hard, also the time of the process significantly reduces, LCA and TEA studies have shown that these type of bacteria that we call it heterotrophs can provide the lowest environmental impact and highest profit margin compared to all currently metal extraction methods,

here is a great reference:

Bioleaching is considered to be an environmentally friendly alternative to traditional pyrometallurgical methods, as it does not generate as much waste and reduces the energy requirements for metal extraction.

Therefore, it is worth pursuing further studies in bioleaching as it has the potential to revolutionize the iron ore extraction industry. I would like to invite you to read my recent article on this subject, which provides some latest insights into the latest developments in this field.

Dear Ali Behrad Vakylabad You are completely right. Reducing particle size does not always work. I have a similar experience when I was working on copper slag bioleaching. The positive impact of reducing particle size has been observed until 5 microns, however, under 5 microns, we observed less efficiency in copper recovery, since the column had been chocked and oxygen circulation faced diffculties.

Please look at the following below links which may help you in your analysis:

Thanks

Also to consider, what do you want the PhD for? Are you wanting a career in academia or industry? What is your interest like regarding computational work? Or are you more interested in experimental work? Or a mix? A masters is obviously a shorter investment than a PhD. A Masters with no thesis is about 1 year, a MS with thesis is about 2 years. I spent time with two internships, the master's thesis and took about 3 years. Later the PhD in a different school on a different topic.

One advice I would offer is be flexible. I can say that plans never seem to work out the way you think they will. If you want the PhD then there is no guarantee it will work out as you imagine (that is not necessarily a bad thing). I once planned on getting my degree and schooling done, get a job, get married, have kids. I ended up getting married then kids, then finished my degree, and then a job. You never know what life will bring and how your research will go.

As for your topics, this is not my thesis topic, but I do like more options 3-7. However, some of the froth flotation topics could combine and work in a larger study that could come together for a PhD so if I only stuck to 3-7 I could miss a chance to work on topics that compliment and that would make a potentially more cohesive study. I did some early work with flotation so don't ignore that work as I did not call the number. If there's something you have a passion about, it might be worth trying to work that into your decision. "If you love what you do, you never work a day in your life." Having passion for whatever you choose will help you along the way because not all days will go well and sometimes you may have doubts.

Also, back to a career path, would you in the end want an industrial career or an academic one? Picking areas of research you want to grow your knowledge and expand takes time. At the same time my advisor did some work in nuclear isotopes and later worked in the pulp and paper areas of research. He did not stay in just one area but found things he was interested in and made those areas of study. If you have the foundation of how to use the scientific method you can ideally work in any field you want. Figure out your problem statement, collect information, develop models and later test them. Then come to some conclusions on that work in the end. Good luck on the start of your graduate studies. There is more than one right answer so don't go crazy over making a decision.

I think it depends on the target. if you want to produce iron to be processed further to make steel products, it is not economically viable as simple physical methods such as gravity and magnetic separation can be used to produce iron concentrate. But, if you want to produce a product such as nano based iron as a career material, it could be a good choice.

Dear Mr. Bhowmick,

you are right that bog iron ore is no longer a feasible target for the exploitation of Fe. It was only done on the Jutland peninsula , Denmark, for a limited period of time and during wartimes in Germany. Iron ranks among the commodities where you do not face any shortage during the near future. Thus botanical extraction of Fe will certainly not be feasible in view of the large banded Fe formations. There is only one ore mineralization known to me which has been "harvested" in an economic way similar to what you are going to accomphlish with Fe. It is algal gold in rivulets and creeks. It is biological concentrated and it is replenished within men´s lifetime. The supergene organic accumulation only worked in areas where you encounter high background values of gold. You can compare the mechanism of gold concentration with your bog iron ores. Algal structures are still to be seen in the Au nuggets and prove the afore-mentioned ore-forming process.

Kind regards

H.G.Dill

It is extremely dependent to the type of waste, economic factors and location of plant. For instance, in countries with high costs of energy, the leaching and bioleaching methods can be a good alternative for pyrometallurgical methods. In some countries the environmental laws are very rigid. Again biohydrometallurgical methods can be used. In addition, for wastes with high volume and low metals concentration it would be better to use the hydrometallurgical methods because these methods are more economic and save energy.

Yes it is feasible and some researches have been done in this regard. You can find complete information in this topic at following paper:

Bioleaching can be extensively use for metals extraction from coal gangue, however its details are dependent to the gangue properties.

If valuable metals (such as gold) were concentrated in pyrite (as one of coal gangues) you can use acidophilic bacteria to biooxide the pyrite and liberate or dissolve the valuable metals. If valuable metals are concentrated in aluminosilicates you can use microorganisms that produce organic acids.

Thank you Sina Ghassa

Hi,

As you rightly afraid that autoclave (with that high temperature and high pressure) may have some impact on the mineral characteristics and leachability of minerals. So in this regard, I would use any bactericide (such as thymol) to suppress any microbial growth (including indegenous ones). Please see some articles that use thymol in the abiotic controls (instead of autoclaving).

1. Bioleaching of a complex nickel–iron concentrate by mesophile bacteria

2. The effect of ferrous and ferric iron on sphalerite bioleaching with Acidithiobacillus sp.

3. Bioleaching Of Copper From Black Shale Ore Using Mesophilic Mixed Populations In An Air Up-Lift Bioreactor.

Nearest will be Mn..

Thank you for the information Mark .

The case of bacterial multimetal resistance  is a bit different from resistance to single metal but is more worthy as a tool for bioremediation. I am particularly interested to tolerance and resistance strategy and the cellular, biochemical and molecular mechanism involved there. How does escape mechanism and tolerance in course of time evolves as an adaptive  strategy and means of detoxification and/or removal?

Genetically engineered consortia could be deployed in industrial heap and tank leaching operations to improve bioleaching and biooxidation processes. However, it is crucial to consider that the tailored consortia have to compete with other microbes and their associated consortia in the non-sterile leaching environment. Usually this is not too much of a problem as the fastest growing species is usually the one leading to increased leaching. Depending on the ore leached, however, in particular chalcopyrite ores, high redox potential, which is associated with dominant iron-oxidizing microbes such as Acidithiobacillus ferrooxidans or Leptospirillum ferrooxidans is not practically a realistic strategy till day as the leaching process will decease and stall after an initial high rate of recovery.

With the advbancement of GE technology scientist would overcome the present stumbling blocks and the ability to design and manipulate microbial consortia may allow them to enhance mineral recovery in biomining processes beyond the yields  observed with naturally occurring consortia.

Dear Swaroop,

Pulp density and dilution factors are the two main factors have to be considered...

ICP/AAS analysis will provide the Cu concentration in wt/vol (e.g. mg/L), first it has to be convenrted to wt/wt (e.g. mg/g).. For instance, if xx mg/L is your ICP result, then

Cu leached = (xx mg/L X dilution factor X volume of the leachant (or culture))  / grams of chalcopyrite

So, the result gives Cu leached per gram of sample (mg/g is the unit)..

And then the Cu recovery can be calculated as given below,

Cu recovery = (Cu leached per gram of chalcopyrite / Total Cu present per gram of Chalcopyrite) X 100.

Regards,

Manivannan

Perhaps look into repeated measures ANOVA for your time series data to determine the statistical significance. Otherwise, you could visually assess the difference between strains by drawing error bars of the standard error of the mean for replicates on a plot. An example this is in Figure 5 on the linked paper.

Hi, Ayse Tuba Kocaman.

This result is by the chemical properties of chalcopyrite. The chalcopyrite is a mineral-consuming acid. which is the chemical or mineralogical analysis of your mineral? What is the content of your chemical control?

Dear Dr. Naik,

as already mentioned by Dr. Keiter, there are many rocks in question.

Rock salt disolves in water, siliceous rocks need HF.

I cannot list all rock types.

H.G.Dill

Dear Mohammad,

You should play with the parameters of this equation:

F/C = (c – t)/(f – t)

Rafik

Old mining operations produced huge amounts of heaps and slags. Considering depleting reserves, those so called waste piles will be our future mine deposits. Bioleaching methods could be integrated to each type of mining heaps and processed slag piles to effectively recover desired metals, even to recover metals which are in their oxide forms. I think the most challenging part is to recover metals from carbonate bearing heaps, considering their acid neutralizing capacity. 

You may perform some experiment this way, but the results will not be statistically valid and hence you will never get reproducible results.

Dear Dr Sandeep Panda

I think the best method for chalcopyrite bioleaching depended on grade and refractory of this mineral.

I think that best method for primary and refractory copper sulfide such as; chalcopyrite is Geo-Coat process.

All The Best

Dr. Sajjad Jannesar Malakooti

You are absolutely at right direction. Bioleaching is valuable for leaching of copper from Fe-Cu-S. You can use different acidophiles to conduct this process. You may find literatures. But the process is very slow than acid leaching.

You may try chemical or bio beneficiation. It depends on the composition of dross.

What pH are you talking about?

Any acidification in a complex medium will cause hydrolysis of some of the components, especially at high temperatures. All depends if that is a problem for you or not. Some manufacturers indicate that the pH of some media can be lowered with lactic or tartaric acid. Quite common in some fungal media

There are several buffers at low pH, e.g. citrate, phosphate,..., but keep in mind the osmolarity of the medium. It can have a detrimental effect on some bugs.

Also, if you are preparing solid media, the agar will hydrolyse too, at least partially. For this you can autoclave separately the media and the agar and mix them together when they cool down.

Mouna,

I don't think that neutral pH bioleaching is adventageous and I didn't study on neutral pH bioleaching but, here is a summary of circumneutral pH leaching that I used in one of my unpublished reports, citing Schippers (2004). Check out the references below that might answer your multiple questions. 

"...When the pH of the environment is increased to circumneutral (pH 5.5 – 7.4) and alkaline conditions, bioleaching is no longer a matter of the subject as ferric iron is out of its stability limits (Schippers, 2004). Moderately acidophilic bacteria like Thiomicrospira frisia and Thiomonas intermedia take place in metal sulfide oxidation (Brinkhoff et al., 1999) by oxidizing the sulfur moiety of the acid soluble metal sulfur to generate protons (Schippers, 2004). As Fe(II) oxidizers are not present at an environment with neutral pH, only the intermediate sulfur compounds can be oxidized of an acid soluble metal sulfide, which are formed by chemical oxidation (Schippers, 2004)...

References

Brinkhoff, T., Muyzer, G., Wirsen, C.O., and Kuever, J., 1999. Thiomicrospira kuenenii sp. nov. and Thiomicrospira frisia sp. nov., two mesophilic obligately chemolithoautotrophic sulfur oxidizing bacteria isolated from an intertidal mud flat: International Journal of Systematic Bacteriology, v. 49, p. 385–392.

Schippers, A., 2004. Biogeochemistry of metal sulfide oxidation in mining environments, sediments and soils. In: Amend, J.P., Edwards, K.J., Lyons, T.W. (Eds.), Sulfur Biogeochemistry — Past and Present. : Special Paper, 379. Geological Society of America, Boulder, Colorado, USA, pp. 49–62."

Hope this would help. 

Regards

Well lets answer your question in steps. First of all bacterial leaching is mostly use for low grade ores  or tailings, which are dumped over land. If bacterial leaching is not done, the ores will still get leached due to environmental conditions and weather conditions which can not be controlled. The leachate will pollute table water and adjoining land and fresh water bodies mostly by percolation. If a controlled leaching process is used then such pollution can be averted. Classical hydrometallurgical leaching is not affordable due to low mineral content. So is the case with other classical extraction processes. Therefore, economically  feasible process  is the bacterial leaching which does not need any major investment. Here even if the mineral can not be recovered, at least we have saved the environment and hence such a process is ecofreindly. I tell you this because basically I am a geomicrobiologist  myself.

mortor and pestle and elbow grease. Oh, and Ian is right, that Fe fluorescence can be a headache when using Cu-Kalpha radiation if you don't have an energy sensitive detector with a discriminator with high enough energy resolution.

Bacterial metabolism can change in time. To say more, it is almost bound to change in time in some situations. And as it seems this statement is correct not only for the bacterial cells. The most important reason is just as Ignacio Badiola said the metabolism of the cell. I think this also has to do quite a lot with the pH value of the environment. Some of the secondary metabolites may intefere with the pH value, therefore influencing the cells' metabolism - eventually even the cells' viabillity.

During one of my previous studies, the metabolism of the microorganisms changed probably due to the fact I inoculated the cells in plates too often and the cells slowly started to lose their unique abilities.

Dear Luis,

The Gold Mine I work for is using Bacterial oxidation. We use the same titration method that you have suggested and find it to be very effective for Fe(II). We start with 5mL of sample at pH from 1 to 2 and add 10mL of H3PO4:H2SO4 (1:1). We use 0.439 g/L Potassium Dichromate so that each mL of dichromate is equivalent to 0.1 g/L Fe(II). Diphenylamine sulfonate is the indicator.

We use a slightly different method for total Fe after reduiction of Fe(III) with Stannous Chloride. We cannot use Zinc metal as there is arsenic present from oxidation of arsenopyrite. Zinc would react with this and produce toxic arsine gas. If you want that method I can attach it also.

Storage of Acidithiobacilli et al. can also be performed without additional cryoproective agent. We are using Microbank(TM)  cryovials with good success. See www.pro-lab.com/literature/microbank-sales-literature.pdf for further information. 1 mL of culture is added to the ceramic beads in the vial . After 30 min the supernatant is discarded and the vial are frozen and stored at -80C. For inoculation you pick a bead with a sterile loop and transfer it to fresh medium.

Employing bacteria to recover metals from a range of sources remains a niche commercial activity in Europe but interest is clearly growing. Bioheap leaching requires space, whereas bioreactor-based techniques are somewhat sensitive to the ups and downs of metal prices. However, the larger the range of metals contained in a low-grade ore or process waste, the more viable are both approaches.

The existence of 'penalty' elements such as arsenic, bismuth and antimony can improve commercial viability. For instance, at Lubin, an active copper mining site in Poland that was examined within BioShale and BioMine, conventional smelting operations nearby have limited the attractiveness of biomining, but says Norris: 'This could change if any ores become available that contain enough toxic metals to make smelting less attractive.'In the case of remediation projects, BacTech's Paul Miller suggests that the intelligent way forward, particularly if the metals recovered are strategically important, would be for local and national governments to agree to step in to support a clean-up operation if metal prices dropped below a certain value.

Leptospirillum spp. are even more sensitive to organic C byproducts than At. ferrooxidans. Leptospirillum spp. also have usually a lower optimum pH and tolerates extreme low pH with some species being found in the Iron Mountain at pH close to 0 or even lower. And Leptospirillum spp. aren't inhibited by a high Fe(III)/Fe(II) ratio or redox potential, conditions in where At. ferrooxidans cannot obtain energy...

That's in general the differences in growth. Respect the solid medium, many Leptospirillum spp. were not succesfully incubated in plates, not even using overlay culturing techniques. The technique consists in plates with 2 layers of 2 different culture media, being the bottom inoculated with a heterotrophic acidophile, generally Acidophilium, which will consume the residual free carbohydrates from the agar and the produced organic carbon byproducts generated by the chemolithoautotroph cultured on the top layer.

This is why all the biomining is quite biased towards Acidithiobacillus ferrooxidans, as it was the only easily culturable acidophilic iron oxidizer for nearly 50 years, even knowing nowadays that in many cases Leptospirillum spp. completely overrules Acidithiobacillus ferrooxidans and in some cases the later is barely present.

fourth article

Best Regards

The smaller the ore granularity, the higher the chalcopyrite leaching rate, so the ores are milled fully before the experiment..Firstly, O2 diffuses into water from the gas/liquid

interface and then diffuses furthermore. It participates in reaction after it touches the ore surface. It is known that the influence of O2 on the chemical reaction is dependent

on each O2 diffusible step during the above process. The gas solubility in the water is affected by the temperature and p(O2). The pressure of O2 has direct proportion to the

O2 concentration in the water. Enhancing p(O2) promotes the O2 solubility and the oxidation speed is increased

Dear Debabrata, it is important fact which I will consider during laboratory experiment. Dear Lala, I often use Bacillus in my bioleaching experiments and I am very satisfied with bacterial activities in the bioleaching of black shale.

Bioleaching is a profitable alternative to the conventional chemical process of uranium recovery. The leaching of U from low-grade ores and solid wastes is realized by chemoautotrophic bacteria such as Acidithibacillus ferrooxidans. Uranium reducing bacteria, particularly Shewanella putrefaciens and Shewanella oneidensis, can be used for UO2 particles synthesis. The bioreduction of U(VI) in the presence of hematite particles can be a way to new catalyst fabrication. (Physicochem. Probl. Miner. Process. 49(1), 2013, 71−79 )

Yes, I do agree that the application of microbiology has promising prospects in the area of heavy metal recovery and remediation. The terminology as we all know is "Bioleaching" for recovery of metal values from ores and other such wastes and "Bioremediation" for remediation of contaminated soils and/or water. A lot of research has been devoted to these areas and is slowly gaining momentum in the field of waste management.

I have been working in these areas for the last 5 years now and recent developments are coming up to put better insights that aims for commercialization of these process.

GMO have a wide range of applications, particularly in agriculture and medicine Economic benefits of genetic modification are many.Some of these benefits are by means of development of existing primary industries. Development of highly skilled work force, attraction of foreign investment and generation of intellectual property are some of the benefits .

Management of solid waste has been established to evaluate the suitabllity for potential alternatives.The most preferable list are 1).Reduce generation of waste,2)..Reuse the materials prior to their entering the waste stream.3),Recycle generated waste materials,4).waste utilisation 5).land filling of unusable waste.

Using sea water in bioprocess industries is an excellent alternative and is a profitable means to conserve the depleting ground water. Use of sea water can prove to be low-cost and economic method as an alternative salt source for the microbe growth for the large scale production of various microbial metabolites, enzymes, etc..

In addition to the point made by Carlos, the larger the scale the more difficult it is to ensure homogeneity and to avoid dead zones

The extremophile Acidithiobacillus ferrooxidans possesses a c-di-GMP signalling pathway that could play a significant role during bioleaching of minerals.It opens a new way to explore the regulation of biofilm formation by biomining micro-organisms during the bioleaching process.

The number of biotechnological applications of IRB, including remediation of soils and sediments contaminated with metals, radionuclides and organics, is rapidly increasing.Bioleaching of iron from kaolin using Fe(III) reducing bacteria has been studied.Nickel present in goethite has been released using IRB in case lateritic ore. A lot of progress has been made towards understanding of the phylogeny, ecology and biogeochemical role of dissimilatory iron-reducing bacteria. The known phylogenetic range of iron-reducing bacteria has expanded considerably, as has the known range of iron minerals that serve as a source of Fe(III) for anaerobic respiration. You can try IRB for processing of Chalcopyrite.I think IRB may break the Chalcopyrite structure and help in releasing copper into solution.