Polyfluorinated compounds (PFCs) are a class of anthropogenic chemicals that have been found in groundwater and wastewater around the world. Perfluoroctane sulfonate (PFOS) and perfluoroctanoic acid (PFOA) are primarily used for industrial surfactants, and aqueous film forming foams (AFFFs). These PFCs and many of their constituents have been found to be carcinogenic to humans and other animals. A simple method for defluorination of these compounds is needed. Advanced oxidation of PFOS, PFHxS, and PFBS-k was carried out using activated sodium persulfate through ultrasonic irradiation with the following condition; [PFC] = 20 millimolar (mM), [Na2S2O8] = 25 mM, pH = 7, and 25°C. Fluoride concentrations were quantified by ion chromatography (IC). In laboratory experiments, batch reactions of PFBS solutions were conducted in purified water at different pH conditions and N2S¬2O8: PFBS molar ratios of 1:1, 2:1, 10:1, and 100:1 respectively. Solution pH was maintained at 7 using HNO3. Of the three compounds, PFHxS had the greatest defluorination (11%) after 120 minutes reaction time. However, PFBS-K had the greatest increase in defluorination (115%) between the control ultrasound (US) experiment and the combination experiment. When Na2S2O8 was increased, the defluorination ratio of PFBS decreased. This decrease was partly attributed to scavenging reactions between SO4¯• and S2O8²¯. These results show a synergism between ultrasonic irradiation and activated sodium persulfate as a form of advanced oxidation. Recommendations for further research into defluorination of PFOS and its constituents by ultrasonic degradation include: the use of high performance liquid chromatograph with accompanying mass spectrometry (HPLC/MS), the use of an ultrasonic probe with alternate frequencies, and the effects of surface tension on defluorination.
| Identifer | oai:union.ndltd.org:wpi.edu/oai:digitalcommons.wpi.edu:etd-theses-2253 |
| Date | 06 July 2018 |
| Creators | Gray, Kevin M |
| Contributors | John A. Bergendahl, Advisor, Paul P. Mathisen, Committee Member, Jose Alvarez Corena, Committee Member |
| Publisher | Digital WPI |
| Source Sets | Worcester Polytechnic Institute |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Masters Theses (All Theses, All Years) |
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