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Characterization of Oxygen Mass Transfer in Viscous Fluids


Technical Approach

The technical approach can be broken into two parts:

  1. Fluid screening for side reactions with high-performance liquid chromatography (HPLC) and UV-Vis
  2. Use of excess sodium sulfite to calculate oxygen transfer rates (OTR)

Fluid Screening with HPLC/UV-Vis

UV-Vis spectroscopy using a HPLC was implemented to determine whether side reactions may occur. This was performed for PEG 3350 and sodium sulfite, as well as ethylene glycol (EG) and sodium sulfite in order to determine if a noticeable shift in absorption occurred. A change in absorption indicates that a reaction occurred, changing the absorbance of the products. An indication of side reaction(s) would present a problem as this would interfere with oxygen concentration data collection.

The HPLC/UV-Vis results for EG (above) and the results for PEG (below). Both analyses focus on 276 nm because that is the wavelength a sulfite ion may be present. Take a look at the y-axis in each image. The EG shows a noticeable change, whereas the PEG shows little to no change; this rules out EG as a potential candidate fluid.

The Steady-State Excess Sodium Sulfite Method

The sodium sulfite method utilizes stoichiometry to measure oxygen concentration drops within the tank. This method was used in conjunction with the dynamic method, which regresses an exponential curve to determine OTR. Interactions with the fluids in the system make it difficult to measure exactly, as the chemical mechanism proceeds by free radical propagation.

Graphical visual of the steps to complete the sodium sulfite method and dynamic method.
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