Investigation of Para-Aminobenzoic Acid’s Photodegradation in Different pH Environments under UVB Light

April 3, 2021   /  

Name: Jingyi Daniel Zhou
Majors: Chemistry, Mathematics
Advisors: Dr. Sarah Sobeck, Dr. Drew Pasteur

The vast use of UV-filters has been related to many recent environmental issues, including coral bleaching and inhibition of aquatic organisms’ light-dependent metabolic functions. Para-aminobenzoic acid (PABA) and its derivates are common sunscreen active ingredient that have been widely studied. Past studies have shown that polarity and pH of the solution environment are able to change the excited state processes, such as intramolecular charge transfer, that occurs following absorbance of UV light by PABA. Based on these studies, two hypotheses about the kinetics of the degradation of PABA in aqueous solutions are tested in this research: 1) the lower the pH, the slower the PABA degradation, and 2) the mechanism of PABA degradation has simpler kinetics in solutions with lower pH. This research applies mathematical modeling methods, using tools including Python and MATLAB, to test the hypotheses above and better understand the kinetics of PABA’s degradation in water. At the end of this research, a set of optimal mechanisms for PABA’s degradation at pH 2, 7, and 10 and corresponding rate constants were obtained. Even though there were some unavoidable uncertainty existing in the deconvolution model, by comparing the mechanisms mentioned above, both hypothesis 1) and 2) were still confirmed. For future work, weighting should be applied to the individual component signal in the model in order to increase quality of fitting. And finding a mathematical relationship between signal’s bandwidth in absorbance spectrum and other factors is also of interest to decrease uncertainty of deconvolution.

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Jingyi will be online to field comments on April 16:
8-10am EDT (Asia: evening, Africa/Europe: afternoon)

13 thoughts on “Investigation of Para-Aminobenzoic Acid’s Photodegradation in Different pH Environments under UVB Light”

  1. Congratulations Daniel! It has been wonderful to work with during the past 4 years. Your I.S. research showcases your abilities to tackle complex problems.

    1. Thank you, Dr. Sobeck. It is my greatest pleasure to have academic advisors like you and Dr. Pasteur.

  2. Well done Daniel! It has been enjoyable following your progress from back when you were in my General Chem II class through to now. Good luck in the future!

    1. Thank you, Dr. Edmiston. You are one of the most enthusiastic professors I’ve met during four years’ study at COW. Every time when I took your class, I could learn a lot of things both inside and outside the book.

  3. Some great data, and creative ways to do the analysis. Kinetics can be tricky when the rate law changes under different conditions. Well done!

    1. Thank you for the response, Dr. Bonvallet. Yes, I agree that it kinetics are tricky to deal with. Even though the final results matched with my hypothesis, there are still many uncertainties in the analysis process. For example, since there are no previous studies showing mathematical relationship between bandwidth of absorbance signal and other factors, it is hard to narrow down the window for bandwidth coefficient into a small range. Thus, the bandwidth coefficient is where most of uncertainties come into my deconvolution.

  4. Congratulations, Daniel. You have persevered to do good work in I.S. under challenging conditions. We wish you the best with graduate school and beyond!

    1. Thank you for everything you’ve done to assist me in finishing this project. And wish you all the best in the future.

  5. Wonderful work here, Daniel! It’s hard to believe it was just a few years ago that you were in FYS with me – and it’s been fantastic to see your growth since then.

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