Science Buddies: "Ask an Expert"

Hello,

I am currently in the process of developing my science fair proposal, and I'm kind of confused with soil-based and benthic mud microbial fuel cells. Is there a difference in their constructions? Do I have to build a different kind of fuel cell for soil-based samples? If so, are there any tutorials online for it? I'm hoping that I can simply use soil samples in the common tutorials you find on the internet, such as this one:
https://www.sciencebuddies.org/science- ... p026.shtml.
Please let me know if there actually will be a difference if I use benthic mud samples or soil samples. I'm worried that soil bacteria will generate less electricity.

Thank you!

Hi,

You have picked a very interesting and challenging topic for your science project. The project link you provided from this website includes a kit that helps avoid construction and leaking problems involved with making your own fuel cell.
The molecular basis of the microbial fuel cell is electron transfer by anaerobic bacteria that use something other than oxygen as an electron acceptor in cell respiration to produce energy. You can find anaerobic bacteria in a rich organic soil sample or in the soil at the bottom of a stream or lake, so you could use either as a source of bacteria with equally good results.

I recommend that you do a search on the topic of anaerobic respiration so you will become an expert on the topic; also do check out the bibliography from the background section of the project guide.

What experiment are you thinking about doing?

Please let me know if you have any other questions.

Donna Hardy

Thanks for the quick reply!

I'm working on an advanced project so I can go to CWSF again (although currently without a mentor and with limited resources), so I don't want to be using a kit to make my microbial fuel cell . Yes I am currently doing research on how the fuel cell works.

I'm not sure where rich soil can be found? I am planning to gather soil near a river but not at the bottom of it where lots of anaerobic bacteria live... I also read that bacteria in soil are mostly aerobic. Do you think this will affect my results? I heard that they can still undergo anaerobic respiration though.

My experiment will probably be dealing with bacteria that can absorb heavy metals /other pollutants in water in a microbial fuel cell. So I will be looking at bacteria strains from different locations that can produce the highest voltage and decontaminate the most pollutants from water (such as heavy metals and turbidity). I will then isolate the top three strains and send them for sequencing? Hopefully if I have time, I can compare the DNA on Blast.

Thank you!

Crazy_Mad_Scientist

I just came across the Wikipedia page on microbial fuel cells, and it stated that the construction of the soil-based cell was different than the other 2 chambered cell using sludge. Is it actually necessary to change the constructions?

Thanks again

Hi,

Thanks for the update. I have provided advice on MFC's in the past and was not aware there was a difference in MRC design with different soil sources. There might be a difference in specific species from different soil sources, but there should be anaerobic bacteria in any type of soil sample.

Your project idea is intriguing. I have not seen a project on cloning the MRC bacteria before.

I will check the references on the Wikipedia article and get back to you with an explanation within a day.

Donna

Hi,

I checked out the Wikipedia article, and here is my interpretation of the information in the section titled “soil based.”

The first paragraph describes a basic MFC, which is based on soil microorganisms that transfer electrons to the anode electrode, which is anaerobic. The electrons are transferred to the cathode electrode, which is exposed to oxygen. The transfer of electrons creates the current that you can measure. This is a universal description that applies to all MFC’s.

The second paragraph describes a design for a MFC where the anaerobic and aerobic sections of the MFC are not physically divided into two chambers The reference for this paragraph is the instruction manual for an education kit that you can purchase. The directions say you can use any type of soil.

http://www.mudwatt.com/pages/how-mudwatt-works

The third paragraph describes a MFC design that allows flow of wastewater through the anaerobic chamber. This type of MFC is called a sediment microbial fuel cell, but the mechanism is the same as other MFC’s; the microbes transfer the electrons to the anode electrode, which then flow to the cathode electrode. The aerobic and anaerobic chambers appear to be divided in this design. The literature reference for this paragraph is a review article from a scientific journal. I recommend reading this article and including it your literature cited section.

http://pubs.rsc.org/en/content/articlep ... c5ew00020c

The last paragraph describes an application of a SMFC for charging a battery and a desalination application.

So, the information appears to present different designs for MFC’s, but I could not find any information that showed that different soil types require different designs. You should be able to pick any design that you want to make and then use any type of soil. The anaerobic conditions in the anode chamber along with a suitable food source will naturally allow selection of anaerobic bacteria in the soil. You can pick any design you want to make.

I like your idea of working on heavy metal remediation. If you include a specific metal in your MFC as an electron acceptor, the metal will be reduced to a different form using the electroactive microorganisms. For example, here is a reference that describes the recovery of copper and energy from a solution of copper sulfate.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4473641/

Is there a specific metal contamination problem in your local area that you would like to investigate? This would make an excellent topic for your project.

How much time do you have to complete your project? You will probably want to run your MFC for at least 2-4 weeks(longer is better), so you won’t be able to compare too many soil sources, unless you have multiple MFC’s.

Do you have a specific MFC design that you would like to use? I recommend focusing on this part of the project after you have finalized your research question:

https://www.sciencebuddies.org/science- ... ndex.shtml

Let me know what you decide to do.

Donna

Hi Donna,

Thanks a lot for the explanation! I think I understand the terminology and concepts a lot better now. I think I will go with a modified version of the Science Buddies two-chambered microbial fuel cell design, and hopefully construct two to three cells at a time so that I can conduct multiple trials.

There is a local garden that is apparently contaminated with lots of heavy metals:
http://www.cbc.ca/news/canada/british-c ... -1.2857662

Hopefully I can obtain some soil samples there and beside the Fraser river, since their may be heavy metal contamination at those sites, thus harboring mutated bacteria capable of surviving high concentrations of the metals.

I don't think that there is a specific site I want to investigate. I'll just be measuring 3-5 different heavy metal concentrations throughout the experiment. Do you think that collecting multiple samples every few days is a good idea? I'm worried that opening the lid to collect samples will disrupt anaerobic bacteria (because oxygen is being introduced), and that the voltage will go down due to less bacteria present in the cell... Should I isolate the bacteria later on and conduct tests on them afterwards instead?

I have plenty of time to conduct the experiments, since district fair is in March and regional fair is in April. However I still want to complete my first trial before February since that is the school science fair.

This year I want to conduct an experiment without using equipment from a lab (except when identifying bacteria and sequencing Dna). This way I can construct all the equipment I need at home. I already have plans to make an arduino-controlled incubator when isolating the bacteria on petri dishes.

I greatly appreciate your help Thanks Donna!

Hi CRazy_Mad_Scientist,

Excellent. Your project question could be, “Can a MFC be used to remove lead from contaminated soil?” or something similar. Do think about your project question to be as this will determine the details of your experiment.

Your project will more dramatic and focused if you concentrate on just one problem, such as lead contamination.. It is not possible to solve all environmental contamination problems with one experiment so you should not try to do multiple metals. The presentation will be very effective if you can show how to solve the one local contamination problem.
The best source of lead-reducing bacteria should be in the contaminated soil itself, if you can get a sample from the garden soil. The bacteria in the lead-contaminated soil should be enriched for species that have been growing in the presence of the Pb. Perhaps you can find a suitable carbon source to add to encourage them to grow faster.

I am have trouble searching for articles on lead/Pb as this seems to be confusing to Google. I’ll work on this more tomorrow, but see what you can find also. You will need a method to measure Pb.

You should be able to contact a local mentor at UBC. Try contacting the researcher mentioned in the article to see if you can get any additional advice on this topic. It sounds like you are thinking about all of the important details needed for a project, but it’s always good to have more expert advice if possible.

Your MFC design sounds like it will work well. The key to achieving high current in a MFC is the surface area of the anode electrode and no leaks. The anaerobic bacteria will form a biofilm on the electrode surface to transfer electrons as they grow, so a higher surface area will work better.

This is definitely a project you can do at home, except for the cloning, of course. However, do you have a location that will maintain a constant temperature over time, preferably as high as possible? At least 22 degrees Centigrade, but up to 30 would work well. The growth of bacteria will depend on the temperature and you will want to compare results of experiments done over time. Anaerobic bacteria smell terrible as they are growing, so this is not something you can do inside the house.

Donna

Hi Donna,

Yes, my project question will be something similar to that. Most studies I read about bio remediation always test the presence of several metals. Do you think that testing simply one metal will make my project too simple?

I did some research last night on Pb quantification:
https://www.researchgate.net/post/What_ ... oscope_AAS

He stated that the Chaney/Mielke extraction/analysis can be used. However I would need to get my hands on some equipment from a local university. I can also use qualitative chemical reactions, but they won't indicate the concentrations... If I'm using only testing for 1 metal, I can measure the byproducts that form while the bacteria metabolize the metals.

I think that I will conduct the heavy metal remediating experiments separately after getting the voltage and bacteria from the microbial fuel cells. It's too much of a risk to open the lid, like you said.

I was thinking that I would only construct the microbial fuel cells in my basement first, and then add the soil in my garage . I can set up a heater in the garage to maintain 25-30 degrees Celsius throughout the experiment.

Thank you so much Donna!

By the way my chemistry teacher can help me with some chemical reactions to detect presence of heavy metals qualitatively (with color). However I don't think that it will be useful with my project since I want to know the exact concentrations . I think I will go with my other two methods. I will do more research on atomic absorption spectroscopy and look for local labs with the spectrometer tomorrow.

Crazy_Mad_Scientist

Hi CMS,

The wet chemistry method for lead quantitation might be suitable for your project.

The exact project question is definitely up to you and what you think you can do. My impression of what you are planning to do is that it’s going to be a huge amount of work with one metal and perhaps an overwhelming amount of work if you try to do all of the metals. In my opinion, it’s better to do an excellent job on a smaller defined problem, rather than trying solve all problems with one project.

At the science fair, you will need to get the attention of the science fair judges and convince them that you have done a significant project that might solve one of the world’s problems. The impact of trying to solve one important problem (lead contamination or something else) might be more effective than trying to solve the problem with all of the metals in one project. You can explain how your project will help to solve the problem.

If you decide to concentrate on lead, your background section can include the problems with lead contamination through history from Roman times through the present including the water contamination in Flint Michigan and the problem at your local community garden. Your project on the local community garden will show how this one important problem can be solved.

You can leave the exact project question open for the moment, but definitely decide before you start the first experiment. Do consult with your teacher on this important question and get a second opinion.

I thought of one major problem in doing a project on lead. Using a MFC fuel cell to convert soluble lead from a soil sample, which is present as Pb+2 to elemental Pb, which is not soluble, is that this would make the lead less toxic, but would not remove the potential for human toxicity because the lead would still be present in the soil. If you were processing water that was contaminated with soluble lead ions and converting them to the insoluble metal to remove them, that might help eliminate the problem. However, you do need more information on this topic so you can do a valid project. Perhaps the lead expert at UBC could provide additional advice on this question.

For your project, you will need to become an expert in microbiology, electricity, engineering, cloning, and metal chemistry.

Assuming for the moment, that you will continue to work on lead, here is some background on lead chemistry.
Here is an abstract reporting the reduction of lead dioxide in a microbial fuel cell for the purpose of producing electricity. I did not try to request the article, which should include more details, but this report seems to indicate that microorganisms can use lead as a terminal electron acceptor, which is what we expected.

https://www.researchgate.net/publicatio ... _Fuel_Cell

This article provides good background on problem of lead contamination in water

http://scholarworks.umass.edu/cgi/viewc ... t=intljssw https://en.wikipedia.org/wiki/Lead

This article had good information on lead chemistry and toxicity in humans.

http://www.luc.edu/faculty/afitch/Artic ... istics.pdf

Here is the link for information on the scientific review committee from this website. Since you will be working with unknown microorganisms and toxic metals, you may need to have prior approval from your local scientific review committee before you do your project. Do not skip this step as your project could be disqualified at the time of judging if proper approvals are not obtained before you do any experiments. Ask your teacher for help if you need more information.

Scientific review committee https://www.sciencebuddies.org/science- ... _src.shtml

Your basic project idea is excellent, but the underlying premise needs a little more discussion. Please check out the section on choosing a topic from the link this website about how to be successful at a top science competition for more comments:

https://www.sciencebuddies.org/science- ... cess.shtml

Donna

Hello Donna,

I think I can use a qualitative soil test kit that can indicate ppm concentrations of lead : http://www.leadinspector.com/learn/how-to-use/

I have been reading a number of papers concerning bio remediation of heavy metals, and I found that most studies revealed that the main mechanism behind the removal of the metals is bio adsorption. What is useful is that dead microbes can also contribute to the remediation. Here is one of the studies I read: http://file.scirp.org/pdf/ABB20120300017_83240845.pdf. However the bacteria will only be able to absorb a certain amount of metal. On the other hand, if the certain strain of bacteria I'm using can actually degrade the metal or reduce it into a less toxic form, I would need to include an experiment showing the toxicity of the "degraded" metal samples on Daphnia Magna. I can understand now why finding multiple heavy metal concentrations would be a lot of work .

In the meantime I will try to contact some UBC researchers for additional help.

Last year I researched a lot on microbiology, so I'm very familiar with isolation and microbiology techniques. However I did not learn chemistry in school yet (I think I'm going to learn it in last term or possibly in 2 years). I will hopefully do some more research on any chemistry material later on.

Thank you for the papers! They were very informative!

Last year the science fairs I attended did not require that I have my project approved by the scientific review committee. They stressed more on ethics forms. How can I find out if I need to have my project approved? I checked my fair but they didn't have any information on it, except for display safety requirements.

Thank you!

Hi CMS,

You are welcome!

The kit looks good and would be an eady way to test lead. The only problem is that the kit is that the chemistry is not explained. For the science fair, you will need to know how this test works. It’s likely that the test is based on the formation of an insoluble sulfur compound:

http://pubs.acs.org/doi/abs/10.1021/ac3 ... ode=ancham

To find out how the test works, you can call or e-mail the company and confirm the chemical basis for the formation of the black color and explain that you need to know the chemical reaction for your science project. Also ask if there are any other metals that interfere with analysis and ask if they can suggest controls for you to use (positive and negative).

Your analysis of the literature on bioremediation is very astute. However,please remember that you don’t have to solve the entire problem of lead remediation in one science project. You are trying a completely different approach to lead remediation, which is to convert the soluble lead ions to elemental lead to reduce the toxicity. The traditional approach to lead contamination is to add phosphate, which forms a salt that has very ow solubility, and reducing the lead ions is similar, but unique.

For the science fair, you need to understand the problem of lead contamination and explain how your project fits into the big picture. Bioremediation is part of the story, but perhaps your project is a better idea that will help solve the problem more quickly and efficiently. It is true that once the Pb is converted to the elemental form, it is still present and has the potential for toxicity, however, perhaps for next year’s project you could devise a way to safety remove the Pb from soil. Pb is very dense, like gold, so perhaps you could adapt gold mining techniques to cleaning up lead-contaminated soil? You have more than enough to do this year, so don't add anything else to your project. But do think about what the next step would be if you were to continue your project.

I finally found some useful information about the toxicity of elemental lead (Pb)

https://toxnet.nlm.nih.gov/cgi-bin/sis/ ... @DOCNO+231

In a microbial fuel cell, you will be reducing the Pb+2 to elemental Pb, which is much less toxic than the lead ion because it is an insoluble solid. The colorimetric test you will be using measures soluble lead, so you should see a reduction in the lead concentration as the microbes reduce the Pb+ to Pb.

Here is an older, but excellent reference on methods of lead analysis. It explains the chemistry of lead. Since you haven’t had chemistry yet, please do read this paper and let me know if you have any questions about the chemistry. Understanding lead chemistry is important for your project.

http://www.luc.edu/faculty/afitch/Artic ... istics.pdf

Here is a recent review article that summarizes the problem with lead poisoning. I love review articles because they include information from lots of other published papers, so you can get all of the information by reading just one article. The sections from introduction through ionic mechanism of lead toxicity include important background information for your project. If you need more detail on a topic, you can check out the 102 papers in the bibliography.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3485653/

For your project, it would be excellent if you could run a control MFC using a soluble lead salt such as lead acetate or lead nitrate as the electron receptor to show that your microbes can use lead for their respiration (like humans use oxygen). Can you find out if you can get a suitable lead compound? Ask your teacher or the UBC researcher for help if you have trouble.

We need to get more information about the scientific review process. In our local science fairs in the US, we always make sure students get the required approval so if there’s no problem when they go on to higher levels of competition. Did you ask your teacher?

How are you doing on finding MFC construction materials?

Donna

Hi Donna,

Yes I will definately contact the company if I end up using the test kit . If not my science teacher is an expert at chemistry and can help me run a few qualitative tests to review presence of lead. I am not quite sure if the bacteria will undergo bioabsorption or lead reduction like you mentioned.

I can find most of the materials to construct the microbial fuel cell mentioned in science buddies, but I realized that conducting multiple cells at a time with a control will be difficult since it uses a lot of resources. I may only compare two-three souces of soil: Fraser river, contaminated garden, and the control. Do you have any suggestions for building simpler and smaller fuel cells with less supplies? Of course I could build many large dual-chambered fuel cells, but it would be kind of expensive.

I also have another problem with heating right now. I don't want to be building the mfc in my house because it would stink, but my garage would be very cold on the other hand. I can build an incubator easily but it would be hard to fit so many mfcs in one incubator. Do you have any suggestions for places to put the mfc?

I will ask my teacher about the scientific review commitee after the long weekend.

Thank you so much for your amazing help!

Hi,

It would be sufficient to compare results of the contaminated garden soil and with one of the other soils. The presence of Pb+2 would be a controlled parameter in both cells. It would be great if you could do more, but not absolutely essential.

Bruce Logan from Penn State University has probably published more articles on the MFC than anyone else. Here is a review paper from him on MFC design:

https://www.researchgate.net/profile/Ko ... 000000.pdf

Here is a simple design that might work well if you invested in good electrodes with high surface area.

http://www.instructables.com/id/DIY-Mic ... Cell-easy/

Try to minimize junctions that require gluing. If you do have to glue pieces together, make sure you use water-resistant glue. Sprinkler pipes that are designed to be threaded together for a watertight seal seem to work well.

MFC bacteria can grow at lower temperatures, but will grow more slowly. If you can't achieve 22-30 degrees Centigrade, try for 15-20 degrees C. Again, temperature will be another one of your controlled parameters. The rate of bacterial growth generally doubles with every increase of 10 degrees Centigrade up to the maximum temperature.

Unfortunately, science projects are always done in the winter. When you write the section of the project where you explain what you would do differently if you had the chance, be sure to mention that you would do the project in the summertime.

Donna

Hi Donna,

Thanks for the advice! I think I secured my mfc design!

Here is an overview of all the experiments and test I might do:

1. Obtain soil samples from the Fraser river and contaminated garden. Build mfc and place moistened soil in the anode. A small sample of the soil from either location will be plated on agar and colonies will be counted. The top three largest colonies may be identified via pcr if there is time.

2. Feed mfc with substrates along with a small amount of lead contaminated water throughout the whole 2-4 weeks of experimentation. (Lead concentrations will gradually be increased to encourage growth of lead-reducing bacteria.) Multimeter readings will be recorded.

3. After 2-4 weeks soil bacteria will be swabbed onto agar plates with varying concentrations of lead as to find the highest concentration where bacteria can survive. Colonies will be counted via gimp. The top three largest colonies will be identified via pcr and compared on blast if dna sequencing is performed.

4. Top 3 colonies will be grown in seperate nutrient broth tubes with the highest level of lead concentration (found in less step) with one tube containing all three colony bacteria. After 24 hours, lead concentrations will be identified using the lead kit.

Everything will be completed in about 6-7 months. 2-3 trials will be completed depending on the amount of time there is.

Hi CMS,

You are making excellent use of your holiday. The overall plan looks very good.

I recommend making a detailed list of all materials needed for each experiment and a detailed protocol for each step as well. This will help you think about small details in advance and ensure that you have all materials available. I will post some additional comments and questions to help with the planning process.

First comment. The bacteria that can use Pb+2 as an electron receptor are probably going to be obligate anaerobes. This means that they will die if you expose them to oxygen. So, you will need a different medium to grow them.

How many MFC’s are you going to build?

Donna

Hi Donna,

Haha thank you!

I was thinking that I can quickly swab the bacteria onto petri dishes and transfer them to an anerobic chamber:

https://www.sciencebuddies.org/science- ... #procedure

This should work well with both the agar and the liquid media since the chamber would only contain around 3%-5% oxygen. For the liquid mediums, I will put the tubes into a glass jar with the match.

I am hoping to build 4 microbial fuel cells so I can conduct 2 trials simultaenously. However if heating is a problem I will only conduct 1 trial at a time. I'm not in a hurry to finish my project since I have around 5 months until district fair and 7 months until nationals (if I make it).

I will post a detailed list of all materials and steps tomorrow. By the way how often should I add the substrate solution? I've been looking everywhere to find an answer...

The two sites I found below stated that vinegar and water would make a good substrate. The second site is actually from a project at the CWSF several years ago!

http://www.wired.co.uk/article/how-to-m ... -fuel-cell

https://secure.youthscience.ca/virtualc ... &regionid=

Thank you!

CMS

Hi CMS,

The protocol with the anaerobic chamber will work well for growing facultative anaerobic bacteria. Many of the bacteria that have been isolated from MFC's can grow anaerobically and aerobically.

Please see if you can find any information on the identify of bacteria that can reduce Pv+2. You need to find out if they prefer glucose, acetate, or perhaps butyrate as a carbon source. If you can't find any research topic, then you will have to pick one carbon source as this will be a controlled parameter.

I will look for some references also.

Donna

Hi CMS,

Here are some references that might be useful. I need to read these carefully also.

1. Article describing growth of sulfate reducing bacteria to convert lead to insoluble lead sulfides. Optimum growth conditions include sodium lactate as a carbon source; also investigated optimum temperature, pH, and time for this application.

http://www.sciencedirect.com/science/ar ... 8107001397

2. Metal recovery using microbial fuel cells; includes examples of every metal, except Pb, but could be used as a model for your project. .

http://spot.colorado.edu/~zhre0706/pape ... Review.pdf

3.https://www.researchgate.net/publicatio ... monitoring

Donna

Hi Donna,

Unfortunately I could not find any research papers about reduction of Pb+2 in microbial fuel cells . Do you think that I should go with a mixture of acetate and glucose? I don't think that I can obtain sodium lactate from my school.

Thank you for the papers! I have read throught the majority of them. However for article 1, I could not obtain the full article. Is there another way that I can find the results to that study?

Quick question: is the compression fitting used in the science buddies tutorial a compression coupling? I visited my local hardware store and it was the closest thing that looked like it.

Thank you!

Hi CMS,

ou are right. It is hard to find research articles on this topic.

I had based the suggestion of working on lead reduction based on the following abstract. Unfortunately, the article can only be obtained by providing personal information to the Chinese authors, which may not be a good idea.

https://www.researchgate.net/publicatio ... _Fuel_Cell

Here’s an article on using microbial fuel cells to recover heavy metals. Unfortunately, I cannot access the article, but the reference list is included that may yield information. However, I could not see any references that were specifically on Pb

http://link.springer.com/article/10.100 ... 014-0474-2

Here is a paper that describes exactly what you want to do, except with copper. The authors used a MFC to reduce copper ions to copper metal . Copper is a valuable metal so it is worthwhile to develop a recovery process using a MFC. One of the technical problems with a MFC is high resistance, so please note the specific steps the authors used to minimize resistance in their MFC. For your project, you need to do exactly the same reaction, only using Pb+2 as the electron acceptor.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4473641/

One of the additional challenges you have for a lead project is that lead is a toxic element so you will inhibit microbial growth if you use a concentration that’s too high. We need to find a reference that suggests a suitable concentration of Pb+2 to use.

I’ll keep looking.

Donna

Hi CMS,

I had a thought about funding for your project. Ask the UBC researcher if there any source of grant money available for your project on lead removal. Ask the same question of whoever has jurisdiction over the lead-contaminated garden. You can describe your project and explain how it might help the community. You can add up the approximate cost of items that you need to purchase from your list of required materials .

I have not found a reference on using a MFC for lead recovery yet. However in the meantime, here is some more background information for your project. There are a variety of subjects that you will need to be able to explain to the science fair judges, so this will help you to prepare:

1. Electrochemistry of lead: In a microbial fuel cell, you will be measuring the flow of electrons, or current, from the anode (anaerobic chamber) of the MFC to the cathode (aerobic chamber). You need the complete circuit to be able to measure the voltage and current.

This website includes a good description of half-cell potentials and redox (reduction/oxidation) reactions.

http://chemcollective.org/chem/electroc ... tecell.php

2. Here’s an article that reviews the process for electrodeposition of lead. Lead is apparently easy to electroplate, and the reduction of Pb+2 to Pb is what you are interested in.

http://www2.bren.ucsb.edu/~dturney/port ... ing/08.pdf

The reduction of Pb+2 to Pb (0) has a reduction potential of -0.13 V. If this is paired with an oxidation reaction that generates more than 0.13 V, then electrons will flow from the anode to the cathode and you will be able to measure voltage and current, as long as the resistance is not too high.

3. Valence electrons of lead: This website has a good diagram that shows the electron configuration of lead.

http://environmentalchemistry.com/yogi/periodic/Pb.html

The element has 82 protons and 82 electrons for a net neutral charge. There are 5 electron shells that are completely filled and 4 electrons in the 6th shell. The outer 4 electrons are available for chemical reactions. (Refer to the shell model which shows a dot for each electron). These outer electrons are named 6s2 and 6p2 and they can escape from the atom through a chemical reaction called oxidation to create a lead ion that has a +2 charge (missing 2 electrons) or a +4 charge (missing 4 electrons). The molecule that receives the electrons from Pb will be reduced. Oxidation and reduction reactions always occur together.

4. Anaerobic respiration. Humans and other animals use oxygen as an electron acceptor to produce energy from food. This is called aerobic respiration. Some microbes use an element other than oxygen for an electron acceptor to produce ATP (energy) in a process called anaerobic respiration. The microbes in the anode chamber of a MFC transfer the electrons to the anode electrode and the electrons then flow to the cathode chamber.

https://en.wikipedia.org/wiki/Anaerobic_respiration

5. Solubility of lead compounds. This website shows the solubility of various lead compounds on grams/100 mL. Many lead salts have low solubility and this feature has been used to reduce the toxicity of lead in environmental samples. The traditional treatment of lead-contaminated soils is to add phosphate fertilizer, which forms insoluble lead phosphate. The authors of the one paper I found yesterday used sulfide-producing anaerobes to precipitate lead as lead sulfide.

https://en.wikipedia.org/wiki/Solubility_table

Note that lead acetate has a solubility of 44.3 grams per 100 mL at 20 degrees C compared to lead phosphate with a solubility 3.4 x 10-4 and lead sulfide at 6.76 x 10 -13, or 0.000000000000676 grams/100 mL.

Donna

Hi Donna,

The third paper was very informative! I have noted some construction aspects to avoid high resistance. By the way I am still looking for a UBC professor since there are few that work with bacteria bioremediation and mfcs. Here are some of the professors that seem knowledgable in this field:

http://www.chbe.ubc.ca/profile/susan-baldwin/

http://engineering.ok.ubc.ca/faculty/de ... berts.html

http://biochem.ubc.ca/person/lindsay-eltis/

This is a good lab I can contact if there is anything that requires sophisticated equipment:

https://navigator.innovation.ca/en/navi ... ologyGroup

I'm not too worried about expenses right now, especially since grants for students are so hard to get... Last year all of the platinum projects at the CWSF were done at home without a mentor or a lab

However if my project begins to get pricey, I can apply for the Safoni Biogenius Challenge, as they offer a $750 research grant.

Wow thanks for all the papers! I will try to finish them hopefully by tonight. I have a few projects so I will take some time off my research. I will be writing my full science fair proposal that I need to submit to my teacher tomorrow.

I think that this paper would do for lead tolerance: http://www.sid.ir/en/VEWSSID/J_pdf/80620105601.pdf

and this one: http://www.bioline.org.br/pdf?ja06032

I have a few more papers bookmarked but I haven't gotten to read them yet.

Also do you recommend that I start writing in my lab notebook now?

Thank you!

Hi CMS,

Any of these UBC faculty members has expertise that would be helpful if they could mentor you. Here is a summary of their backgrounds. Dt. Baldwin’s and Dr. Roberts’ expertise seems more relevant for your project as they both are experts in microbiology and engineering. Dr. Ellis has expertise in molecular biology, and this would help in the second part of your project.

Susan Baldwin Bioprocess engineering, anaerobic fermentation, bioremediation. reaction kinetics
Deborah Roberts microbiology water quality engineering, treating contaminated water.
Lindsay Ellis microbiology molecular biology

I would write each researcher an e-mail message and very briefly describe your unique science project and ask for help. Ask for a referral if the person you are asking cannot help. At this point, it seems like you just need someone to review your project and make suggestions. Don’t take it personally if you don’t receive any response; professors are incredibly busy and October is grant proposal time, so they may be focused on this. However, it would be fantastic if someone could provide advice for your project
. .
I will read the papers you found and send back comments later today.

You can start writing in your notebook as soon as you make your list of materials and have your plans. Just write a few brief notes every time you do something on your project.

Donna

Hi CMS,

The UBC lab sounds like a good resource. I wonder if they have any extra incubators available. You should also find out if Dr. Eskicioglu could provide advice for your science project.

The reference on heavy metal resistance in microorganisms has good background information, but consider this reference a poor example of data presentation. The second article has much better data presentation and includes some interesting data on microbial lead-resistance.

Donna

Hi Donna,

I was thinking that I would send them a copy of my detailed proposal to the professors if they agreed to look over it. This way I can get feedback, and maybe a lab to work in on the last part of my project (pcr and genetics).

I understand when professors don't respond to my emails . Before deciding on this idea, I sent many emails for possible mentorship. However I didn't receive any replies. However this time I'm not asking for lab space immediatly so I hope that they do reply.

I found that the microbial fuel cells I will construct will be fairly small, so I think I can build a large enough incubator at home (with a styrofoam box and lightbulb and arduino to control temperature).

I will start on a detailed methods and materials procedure:

1. Construct microbial fuel cell as described in https://www.sciencebuddies.org/science- ... p026.shtml. Soil samples will be collected 5cm below ground, and will be immediatly transferred to mfc chamber after dampening with water. Equal weights of soil will be measured in the 2 mfcs constructed. Mfcs will be immediatly incubated at 20 - 25 degrees celcius. Multimeter readings will be taken after a stable current is established (in order to show increase in voltage).

Major supplies needed: incubator, carbon cloth, aquarium pump, compression joints.

Note: a few innovations will be applied to the cells; in the anode, a tube will be attached to a bottle to deliver substrates by drip-drop. The tube will be placed next to the biofilm (where the electrode base is). Another tube will be attached to a container filled with water to remove excess gas from the anode. The whole mfc will be placed on top of a plastic container to catch leaks.

Methods to reduce internal resistance: reduce distance between electrodes, increase ion concentration in salt bridge (increase conductivity).

Agar dishes will be made with limited exposure to oxygen. Bacteria from the soil sample will be plated and stored in an anaerobic bacteria at 25 degrees celcius for 24 - 48 hours. Colonies will be counted via computer imaging software (which I plan to code). Top three biggest colonies will be identified via biochemical methods if there is time. If colonies cannot be analyzed biochemically, colony morphology and colours will be analyzed on the computer.

By the way do you recommend that I use graphite for electrodes? This study used graphite rods from HB pencils: http://www.omicsonline.org/open-access/ ... ?aid=57993

I will write the other steps in another post.

Thanks!
CMS

Hi CMS,

I would not recommend sending out your detailed protocol unless you know there is someone who is available to review it. Do wait until you get some sort of positive response from one of the professors.

Perhaps you could call Dr. Eskicioglu’s UBC lab and ask if there is someone available who could help you. There might be a graduate student available who could help. The School of Engineering phone number is (250) 807-8544. As an introduction, perhaps you could think of one question about your project (such as what would be the best electrode material for your MFC) and start with that. If you get a positive response, you could proceed with the request for a review, and possibly, a local mentor.

A small microbial fuel cell would be perfect. You will just need to show that your concept will work. A light bulb in a Styrofoam box should be perfect for a 30 degree Centigrade incubator.

For the anode chamber you will want to use the carbon source that will allow the maximum amount of bacterial growth and an electrode with the maximum surface area. From all of the papers that we have reviewed lately, do you recall which conditions allowed for maximum power generation? That’s what you want to do. I will check the references also.

You will be converting the Pb+2 to Pb0 in the cathode chamber. Lead does not conduct electricity well, so would not be a good material for an electrode. We read one paper that used Pb02 as a cathode electrode material. I don’t know if it is possible to electroplate Pb onto graphite. This question needs to be answered before you can build your MFC.

Donna

Hi CMS,

Anode electrode: Here is a recent reference that reviews the power generated with different anode, cathode, microbe, and substrate combinations. Let me know if you can’t access this paper. Excluding the platinum electrode, which would be cost-prohibitive, for your project, it looks like you would get good results with either a carbon paper or graphite anode electrode. The anode electrode is one of your controlled parameters, so pick the one that you can easily obtain.

ww.sciencedirect.com/science/article/pii/S1110016815000484

Substrate: It looks like sewage sludge is generally the best carbon source for MFC power generation. However, this type of sample is of unknown composition, so you should pick a carbon source with a known molecular structure. Glucose looks like a good choice, but acetate or lactate would also work. Pick one that you can obtain easily. The substrate and concentration is a controlled parameter, so make one choice.

Cathode electrode: This review article has the best description of the chemistry and requirements for the cathode chamber that we have seen. Table 3 shows good results with carbon, graphite, graphite felt, and other materials. Since you want to reduce Pb in the cathode chamber , you need to figure out how to optimize conditions so that the Pb +2 will be the final electron acceptor. You can add a soluble lead salt, such as lead acetate or lead nitrate, but you will probably also want to add a catalyst as described in the paper.

This is a 2015 reference and the author of the paper might be available to give you some advice on the composition of a cathode chamber that could be used to convert Pb+2 to Pb. Why don’t you send an e-mail message to Dr. Rahimnejad and briefly describe your project and ask for advice? His e-mail address is included in a link by his name at the top of the paper.

You should also read the sections on the cation exchange membrane (CEM) which allows transfer of the protons to the cathode chamber.

Here is another reference that used ammonia-treated carbon cloth and phosphate buffer to enhance power generation. The ammonia treatment at 700 degrees C would be outside of the scope of your project. You can file this idea away as a change you would make if you had unlimited resources. The phosphate buffer idea should be easy enough for you to do.

tps://pdfs.semanticscholar.org/a2a3/e24035e02bc0ff08b976ef1cbb74447e0317.pdf

Donna

Hi CMS,

Going back to the copper article that you are trying to model, the authors used copper metal as the cathode electrode. This makes sense because the copper ions were electroplated onto the copper electrode.

The author of this paper says that the details of the MFC set up for copper plating are in the following reference. However, I can’t seem to find the reference cited in the paper. Can you send an e-mail message to this author also and ask for the experimental set-up reference? You can also ask for suggestions for your project. The author is Pau Rodenas Motos and the e-mail address in the Netherlands is [email protected].

Kuntke P., Sleutels T., Saakes M., Buisman C. J. N. (2014). Hydrogen production and ammonium recovery from urine by a Microbial Electrolysis Cell. Int. J. Hydrogen Energy 394771–4778. 10.1016/j.ijhydene.2013.10.089

You should also note that these authors used acetate as the carbon source and they had to adjust the pH during the experiment.

Lead can be electroplated onto copper. I’m not sure how well It will plate onto graphite.

https://www.youtube.com/watch?v=rJocKumgFlk

Donna