Hello!
I hope everyone is enjoying their time at their labs, and is making great progress with their projects. This is my first time being part of a research group, and I am beyond excited to have this opportunity! I appreciate the welcoming attitude of everyone I have met through this experience so far. Over the past two weeks I have been familiarizing myself with everything that goes on in our lab, and getting used to what our day to day work consists of. I am working in Dr. Verduzco’s lab, which focuses on the development of complex polymeric materials. My mentor, Amit Jain, is specifically working on a desalination process known as Membrane Capacitive Deionization, or MCDI. Essentially, the way MCDI works is you send salty water through the MCDI cell where a voltage is applied and then removed (or reversed). When the voltage is applied, the adsorption cycle takes place in the cell. Ions are temporarily absorbed into the activated carbon material, which results in a flow of fresh water. After the voltage is removed, or in some cases reversed, the desorption cycle takes place. The ions are released back into the water, which results in a brine waste water solution. The MCDI cell is comprised of 5 main parts. The first layer in the cell is an activated carbon electrode, which is made from flow coating a graphite sheet with an activated carbon slurry we prepare in our lab. The next layer is a cation exchange membrane that has either been flow coated directly onto the activated carbon electrode, or is one of the commercial IEMs we received that is separate from the electrode. The function of the ion exchange membrane is to block counter ions from being absorbed into the electrodes, which would lower the efficiency of the cell. After the cation exchange membrane, we have a plastic mesh spacer that separates the cation exchange side from the anion exchange side, and then the anion exchange membrane followed by another activated carbon electrode.
Inside the MCDI Cell: Here you can see the plastic mesh layer on top of the activated carbon electrode coated with a cation exchange membrane.
For my project, I will be focusing on the improvement of the electrode synthesis. Many factors can cause the electrodes to appear and perform abnormally, so I will be testing out multiple solutions to the issues we face. Below is my problem statement rough draft, and I would be happy to receive feedback on it!
MCDI, or Membrane Capacitive Deionization, is a promising method developed to purify water. The MCDI cell is comprised of two activated carbon electrodes, where one electrode is coated with a cation exchange membrane and the other with an anion exchange membrane. Currently, the electrodes we use for our MCDI cell appear and perform abnormally due to issues that arise from the synthesis process, including improper drying, uneven coating, and insufficient coating. Each electrode varies too much to be able to get accurate and usable data when these issues are present. I will be exploring the use of heat throughout the synthesis process, increasing the viscosity of the IEMs, using double coatings for the IEMs, and using different methods to hold the electrodes in place during the crosslinking stage to improve the electrodes and their performance.
This is an example of one of our most common issues with the electrodes. There should be three sections clearly defined, but the edges of the ion exchange membrane coatings are clearly uneven, making them useless for testing in the MCDI cell.
Here I am analyzing one of our successful electrodes after preparing several with inadequate coatings for testing.
I am very excited to begin testing my own experiments in the coming week, and to analyze some of the electrodes in the SEM on Monday. I will be posting updates soon of how everything works out!
-Cierra