Accelerated Membrane Aging

Voiceover

Presenter(s)(s)

Steven Beuther

Presentation Number

706

Abstract or Description

The Earth’s population poses a growing problem of water shortage. As the supply of high-quality water is reduced, higher emphasis is placed on water reuse. Membrane filtration enables reuse of water. A polymeric material employed in making water filtration membranes is polyvinyl difluoride, or

PVDF. When membranes are used and cleaned over a long period of time, they deteriorate. With this in mind, this project aims to analyze the surface chemistry of the PVDF membrane as it ages. Membranes deteriorate over the course of approximately a decade, so for the purposes of this experiment membranes were subjected to an accelerated aging procedure to reduce the time scale necessary. A membrane’s age can be quantified as the product of the concentration of the cleaning agent and the duration of cleaning. These two variables can be viewed as contributing on approximately equal footing so that increasing the concentration can shorten the cleaning time proportionally. The procedure will commence by casting a PVDF membrane to simulate those used in industry. The membranes will then be rinsed, soaked in bleach, and rinsed again. After all of the cleaning, contact angle measurements will be performed on the surface. Once the surface is analyzed, the surface chemistry will shed light on the qualities of the membranes during multiple stages of their operation.

Mentor

Volodymyr Tarabara

Comments

Charles Yoo4 years ago

I think that you did a good job with your presentation. It was very informative and the research topic is interesting. I had one question with regards to your results for the surface energies of the PVDF/PVP and PVP membranes. You said that as the aging process went on, the bleach stripped away the PVP in the PVDF/PVP membrane. Once the PVP is leached out, why isn't the surface energy the same as the surface energy for the aged pure PVDF membrane?

• • 1 comment

Steven Beuther4 years ago

Thank you for your comment! Once we got our data back, we were surprised that the PVDF/PVP ended lower than the pure PVDF. Right now, we believe that this is because of the pore sizes of the membranes. Including PVP in the initial casting of the membranes effects the porosity of the membrane. Not only that, but PVP is sort of layered throughout the membrane, so once it is removed the is going to be some gaps left in the aged membrane which will effect the surface energy.

Greg Swain4 years ago

Well done Steve. You made a clear and informative recording for the viewer and you explained the data quite well. I have a couple of questions as food for thought - is there an equation that you used to relate the measured contact angle to a surface energy and do you have any optical or electron micrographs of your polymer membranes at different stages of the membrane aging? You made nice progress on this project and learned about accelerated degradation testing. Nice work!!

• • 5 comments

Steven Beuther4 years ago

I do not believe that we have any micrographs, but I can tell you about the equation that we used. The equation we used relates the contact angle of the probe liquid, the solid surface free energy, and the liquid surface free energy. This allows us to obtain the energy at the interface, which is used for the total surface energy. However, as we are using four probe liquids, this complicates the calculations quite a lot. If I remember correctly, the final equation has more than twelve terms in it and would require a large chunk of time to explain on its own. For the sake of ease for the presentation, we decided to leave it out.