EPFL Research Post # 1
Hi everyone, I just finished a two week internship at the Swiss Federal Institute of Technology Lausanne (EPFL) in the Laboratory of Advanced Separations (LAS). Here, my project was to experimentally develop a carbon capture membrane from a polymer. The methods being used were novel and had not been tried before.
The goal of this project was to develop a spiral-wound (SW) module and test it on house gas, N2, and CO2. Essentially, an SW is a carbon capture membrane wrapped around an aluminum rod several times. By layering the carbon capture membrane on itself over and over, it allows the whole SW to have a much lower permeability. Permeability is the ability for a membrane to have air pass through it – high permeance means more air passes through, and low permeance means less air passes through – measured in liters per minute (LPM). Our goal was to get a permeance, or flow rate, of less than 1 LPM.
In the past, this project had been done with a membrane of only polyethersulfone (PES). The new step that we were introducing was coating a polymer called polydimethylsiloxane (PDMS) onto the PES with the goal of decreasing permeability.
The first step was to develop the PDMS coating. Based on previous results, we decided to use a 30% ratio of monomer to solvent. This ratio proved to likely be the best option for industrially scaling. We aimed to measure 1.04 g of monomer in 8 vials. We used the actual measurements of the monomer to find the amount of heptane (solvent) to put in the vials. After the heptane was put in the vials, we applied parafilm on each one and put them in the sonic bath. Monomer is a gel-like substance and heptane is liquid, so the sonic bath applied sonic waves to the vial to combine the monomer and heptane. Once the samples are no longer viscous, we remove them from the sonic bath and put them on the magnetic agitator for 5 minutes. Magnetic pills are put in each vial and the magnetic agitator creates a magnetic field around it, spinning the pill. This serves the purpose of agitating the mixture and mixing the monomer and heptane. After they are removed from the magnetic agitator, they go back in the sonic bath for 5 minutes to ensure that the solution is homogeneous. Then, we add the catalyst. The amount of catalyst is simply 0.1 multiplied by the amount of monomer. After the catalyst is added, the reaction immediately starts happening. Once the catalyst is added, the samples need to be parafilmed and put in another bath which is heated to about 65 degrees C. This bath also has a magnetic agitator in it, so the samples will be agitated throughout. The vials are put in this bath for 1 hour and 15 minutes. Once the time is up, the PDMS coating is finished.
The next step is plating the PES membrane. During the time the PDMS is cooking, we prepare the plates with the PES membrane. We take aluminum plates and tape some PES membrane to them. The method of taping is very specific as it prevents bubbles from forming. We first take a small piece of tape and place it in the middle of the smaller side. Then, using a rod to flatten the membrane, we take small pieces of tape and apply them to the longer sides and finally put a piece of tape on the other small side. Then, we apply long pieces of tape on all the sides to prevent any liquid from getting underneath the membrane. Once the samples are done, we take them to the spin coater. The aluminum plate is placed on the spin coater and is run at 2500 rpm to ensure it does not fall. Then, we pour all the samples of PDMS on the membrane, covering as much area as possible. Then, the spin coater is run on 2500 rpm for 1 minute. After this, the membrane is done and is put in the oven at 140 degrees C for 24 hours.
That is all we did in the first week. I will write another post about making the spiral wounds and the results as well as next steps for the project.