UPDATE #1

Hello, everyone!

Weeks 1 and 2 are successfully out of the way and the experience thus far has been amazing. Meeting my fellow REUs during the first week was such a delight being that everyone was so nice and welcoming, including the program coordinators, my mentor, and lab professor. My mentor, Jun Kim, mentioned to me in meeting that he read my personal statement, which included information about my previous research in detecting/using ARGs and ARBs by PCR methods and would introduce me to his colleagues working on NDM-1, one of the species I worked with. This was a pleasant surprise for me and immediately marked in my mind that this experience would contain so much growth by making connections.

As for research, we will be using Capacitive Deionization (CDI), a promising and energy efficient technology that removes salt ions from brackish and sea water upon applying an electrical voltage difference between two porous electrodes. There are many forms of CDI, such as flow-by, flow through, MCDI, FCDI, hybrid CDI, inverted CDI, etc. However, all of those CDI removes all ions present in water, i.e. no ion-selectivity. This summer, Jun and I will be focusing on achieving selective removal of heavy metals by adding nano-structured material on top of the CDI electrode. For this we will be pairing LDH (layered double hydroxide) material with CDI to selectively remove the heavy metals we are focusing on, Cu and Pb.

The LDH (layered double hydroxide) material. NaCl: 5.318 g/100 mL; CuCl2: 0.776 g/100 mL

We tested out the material’s permeability by a diffusion cell and took samples every other hour. Over time, we noticed that the diffusion cell would leak from the middle where the LDH material was (not good!), so after finishing the rest of the duration of that test and running it through ICP to measure the concentration vs. time, there was an increase in both Cu and Na, but not as high as we liked. To fix the leaking problem, we borrowed a clamp from Amit that was more sturdy and robust.

Preparing the dilution for our samples.

Diffusion cell.
Left: acceptor side
Middle: LDH and membrane (with Amit’s clamp)
Right: donor side

But, lo and behold, it was still leaking!! After again finishing the duration of our samples and running it through ICP, we analyzed the problem. As it turns out, the LDH material had aggregated powder in certain areas, creating a non-flat surface. While the water moved through it, the non-flat surface made it to where there was extra space for it to leak out during transportation. To fix this problem we will be cutting the LDH material to fit the inner radius of the two gaskets that seal the cell together.

Before we do that, though, we will be conducting a test with the LDH material through an electrodialysis cell. That is our plan for this week.

-Elisabeth Villarreal