PROJECT PROGRESS REPORT BIWEEKLY 2
FORMALDEHYDE DETECTION AND REMOVAL IN
DIRECT ALCOHOL FUEL CELL EFFLUENT
Submitted To
The 2013 Summer NSF CEAS REU Program
Part of
NSF Type 1 STEP Grant
Sponsored By
The National Science Foundation
Grant ID No.: DUE-0756921
College of Engineering and Applied Science
University of Cincinnati
Cincinnati, Ohio
Prepared By
Jenna Simandl, Civil Engineering, University of Alabama
Cuong Diep, Chemical Engineering, University of Cincinnati
Sidney Stacy, Biomedical Engineering, University of Cincinnati
Report Reviewed By
Dr. Anastasios Angelopoulos
REU Faculty Mentor
Associate Professor
School of Energy, Environmental, Biological & Medical Engineering
University of Cincinnati
1. Introduction.
Ultraviolet/Visible light spectrophotometry is a technique that detects changes in
absorption of ultraviolet or visible light within a medium due to the presence of a
chemical compound of interest. In this work, a Nafion membrane, also referred to
as a perfluorosulfonic acid (PSA) membrane, is used as the medium. The PSA
membrane is a copolymer membrane consisting of dispersed hydrophilic PSA
regions within a hydrophobic tetrafluoroethylene matrix. Because of this
morphology, it has transport properties that allow movement of cations and the
immobilization of many dye molecules such as resorcinol. In addition, the
hydrophilic PSA regions can act as acid catalysts. Consequently, in the presence of
different volatile organic compounds, such as formaldehyde and acetone, the
immobilized resorcinol will react, producing a color change, providing a visible
detection of these compounds.
The US National Toxicology Program recognizes formaldehyde as a carcinogen.
Formaldehyde is a compound used in the manufacturing of many household
products, such as cleaning solutions, cosmetics, and wood fixatives [1].
Formaldehyde is also a by-product of alcohol fuel cells, which convert chemical
energy into electricity through an oxidation-reduction reaction. The production of
aldehydes from alcohol fuel cells is a symptom of inefficiency of the cell, as well as a
contaminant to the environment. Because this optical sensing technique detects the
presence of formaldehyde, it can be applied to fuel cell system effluent to monitor its
efficiency and to monitor hazardous emission levels of formaldehyde.
This optical sensing method can also be used for the detection of acetone, which can
be used as a surrogate for formaldehyde during feasibility testing due to easier use
and safety. Acetone is an organic compound that is produced by the human body
and excreted through human breath or urine [2]. It has been found that there is a
correlation between acetone concentration in human breath and blood glucose
levels [3]. When breath acetone concentrations are monitored, this correlation can
provide a noninvasive diagnostic technique for diabetic patients.
Previous studies have determined that in the presence of water, there is no
response in the visible spectrum during attempts to catalyze the reaction between
resorcinol and acetone in PSA membrane. According to Worrall et al. (2013), this
result is in sharp contrast to the significant visible response observed with dry
acetone. Water is known to de-protonate the PSA sites and dilute the membrane
acidity, which deactivates the catalytic properties of the membrane. Because of this
change, the organic compound is no longer reacting with the dye within the
membrane, preventing its detection. A membrane additive has been selected to
potentially mitigate water interference and cease the de-protonation of hydrogen
ions in the PSA membrane.
2. Materials and Methods.
Following previous work by Worrall, et al., a Nafion membrane is soaked in 4mL of
12g/L resorcinol dye in ethanol for 31 minutes. After drying, this membrane is then
soaked in a solution of VA additive oil overnight. After the membrane is immersed in
each of these solutions and completely dried, it is ready for exposure testing.
The spectroscopy software, SpectraSuite, is calibrated with a bare Nafion
membrane to eliminate background influence. Next, the membrane with resorcinol
and VA additive is tested for absorption levels using the UV/Vis spectrophotometer
prior to exposure of acetone.
The membrane is then suspended in a round bottom flask using Teflon tape and a
piece of gold plated stainless steel. A known concentration of acetone and water is
injected into the flask and the flask is capped with a Teflon seal. The flask is placed
in a water bath at 60C for 15 minutes, allowing the membrane to be exposed to the
volatized acetone at a known relative humidity. The membrane is removed from the
flask for the response to be measured.
3. Results and Discussion
Upon exposure to acetone, the membranes changed color from a transparent light
peach to a bright yellowy orange. This response confirms that the VA additive is
mitigating water interference since a color change occurred in the presence of
water. The color change is explained by the drastic shift in absorption of the
membrane at a wavelength of 400.69 nm, marking the reaction between resorcinol
dye and the acetone [4]. The increase in absorption over the near UV-visible light
spectrum and an example of the color change is shown in Figure 1.
Figure 1. UV-vis absorption spectra of PSA membrane containing resorcinol exposed
to 4 ppm acetone with and without VA additive. Inset: resorcinol-imbibed PSA
membrane after exposure to acetone in water (colorless sample contains no VA
while orange sample is with VA).
A water uptake study was performed to determine whether or not the VA additive
was preventing catalyst de-activation by preventing water from entering
membrane. The uptake of water in a bare membrane was compared to the uptake of
water in a VA oil soaked membrane using weight measurement. It was observed
that there is no change in weight uptake between the membranes, confirming that
the additive is not excluding water. Therefore, it is hypothesized that the additive is
preventing the sulfonic acid group deprotonation in the membrane even in the
presence of water.
To further test this hypothesis, a cation exchange study was performed. The
prepared resorcinol and VA additive soaked membranes were soaked in known
concentrations of a cesium (Cs) solution. The Cs cation is known to exchange with
protons in the membrane. The exposure methodology was repeated with these
membranes. As shown in Figure 2, the VA additive is mitigating cesium exchange up
to a certain concentration.
Figure 2. The color change of the PSA membrane in the presence of acetone, water,
and cesium and the effect of cesium concentration on the performance of the
additive
4. Conclusions
Our data indicates that the VA additive is successful at mitigating interferences from
water and salt for the detection of acetone. This initial work also suggests that a
similar approach (VA incorporation) can be used to detect formaldehyde in the
water-abundant environment of a fuel cell effluent. Our future investigations will
focus on testing this hypothesis. Our group has spent a signification portion of the
past week learning to operate a fuel cell test stand with this goal in mind.
5. References.
[1] Sun, W., Sun, G., Qin, B., Xin, Q. “A fuel-cell-type sensor for detection of
formaldehyde in aqueous solution,” Science Direct, Vol. 128, No. 2007, pp. 193-198.
[2] Kalapos, M. P. (2003). “On the mammalian acetone metabolism: from chemistry
to clinical implications,” Biochim Biophys Acta, Vol. 1621, No. 2, pp. 122-139.
[3] Chuji, W., Mbi, A., and Shepherd, M. (2010). “A Study on Breath Acetone in
Diabetic Patients Using a Cavity Ringdown Breath Analyzer: Exploring Correlations
of Breath Acetone With Blood Glucose and Glycohemoglobin A1C,” Sensors Journal
IEEE, Vol. 10, No. 1, pp. 54-63.
[4] Worrall, A. D., Bernstein, J. A., Angelopoulos, A. P. (2013). “Portable method of
measuring gaseous acetone concentrations,” Talanta, Vol. 112, No. 1, pp. 26-30.