Re: Soil-Based Microbial Fuel Cells
Posted: Wed Oct 19, 2016 3:52 pm
Hi CMS,
If you have enough reagent to set up a standard curve and samples, you should be able to read results on the spectrophotometer. You would set up a standard curve from about 0 to 50 ppm and then read the OD of the samples and interpolate from the standard curve. This would work as long as the standard curve is linear.
Since there is the possibility of doing a quantitative assay, it might be best to purchase the reagents separately instead of the test kit.
Here is a link for the details of setting up a lead analysis method. I have not read it in detail yet, but I can see there are some very toxic reagents involved, so this might not feasible.
https://www.cdc.gov/niosh/pdfs/78-158d.pdf
You can also search for dithizone reagent for sale. It looks like the eBay has the cheapest price.
Sigma Aldrich also sells this reagent and they have some research articles that describe how to use the reagent. Look at the bottom of the page for the peer-reviewed papers:
http://www.sigmaaldrich.com/catalog/pro ... ®ion=US
Measuring the lead tolerance of the bacteria in your sample will be a good experiment to do.
Plating lead. You have a number of experiments that you are planning to do in your project. One experiment is to use the soil from the lead-contaminated garden soil and see what happens to the lead in that sample when you set up in the anode chamber of the MFC. The second part is to use the electrons generated in the anode chamber that are sent to the cathode chamber to reduce Pb+2 (lead ions) to Pb (lead metal). Lead metal is much less toxic compared to lead ions.
To set up a conventional MFC, you will aerate the cathode chamber with lots of oxygen so that the electrons and hydrogen ions from the anode chamber will be transferred to oxygen to create water. (the platinum catalyst facilitates this reaction.) I do recommend setting up a standard MFC first just to make sure you have a set up that is working.
To set up a lead plating MFC, you would put lead acetate in the cathode chamber and exclude oxygen, so that the electrons will be transferred to Pb+2 (in solution) to reduce it to Pb(0), solid lead. This process is called plating and the Pb should be deposited on the cathode electrode.
Go back and read the copper plating paper for more on this topic.
The Wikipedia article on reduction/oxidation reactions may help in understanding the chemistry. The carbon food source that you feed the MFC microbes will be oxidized to produce energy and the oxygen or Pb +2 in the cathode chamber will be reduced. Reduction/oxidation reactions always occur together in complementary reactions.
https://en.wikipedia.org/wiki/Redox
Donna
If you have enough reagent to set up a standard curve and samples, you should be able to read results on the spectrophotometer. You would set up a standard curve from about 0 to 50 ppm and then read the OD of the samples and interpolate from the standard curve. This would work as long as the standard curve is linear.
Since there is the possibility of doing a quantitative assay, it might be best to purchase the reagents separately instead of the test kit.
Here is a link for the details of setting up a lead analysis method. I have not read it in detail yet, but I can see there are some very toxic reagents involved, so this might not feasible.
https://www.cdc.gov/niosh/pdfs/78-158d.pdf
You can also search for dithizone reagent for sale. It looks like the eBay has the cheapest price.
Sigma Aldrich also sells this reagent and they have some research articles that describe how to use the reagent. Look at the bottom of the page for the peer-reviewed papers:
http://www.sigmaaldrich.com/catalog/pro ... ®ion=US
Measuring the lead tolerance of the bacteria in your sample will be a good experiment to do.
Plating lead. You have a number of experiments that you are planning to do in your project. One experiment is to use the soil from the lead-contaminated garden soil and see what happens to the lead in that sample when you set up in the anode chamber of the MFC. The second part is to use the electrons generated in the anode chamber that are sent to the cathode chamber to reduce Pb+2 (lead ions) to Pb (lead metal). Lead metal is much less toxic compared to lead ions.
To set up a conventional MFC, you will aerate the cathode chamber with lots of oxygen so that the electrons and hydrogen ions from the anode chamber will be transferred to oxygen to create water. (the platinum catalyst facilitates this reaction.) I do recommend setting up a standard MFC first just to make sure you have a set up that is working.
To set up a lead plating MFC, you would put lead acetate in the cathode chamber and exclude oxygen, so that the electrons will be transferred to Pb+2 (in solution) to reduce it to Pb(0), solid lead. This process is called plating and the Pb should be deposited on the cathode electrode.
Go back and read the copper plating paper for more on this topic.
The Wikipedia article on reduction/oxidation reactions may help in understanding the chemistry. The carbon food source that you feed the MFC microbes will be oxidized to produce energy and the oxygen or Pb +2 in the cathode chamber will be reduced. Reduction/oxidation reactions always occur together in complementary reactions.
https://en.wikipedia.org/wiki/Redox
Donna