Continuous Monitoring and Removal of Formaldehyde Vapor in Ambient Air Using Polymer Catalyst Membranes
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University of Cincinnati / OhioLINK
2013
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ndltd-OhioLink-oai-etd.ohiolink.edu-ucin13844280492021-08-03T06:20:21Z Continuous Monitoring and Removal of Formaldehyde Vapor in Ambient Air Using Polymer Catalyst Membranes Ravi, Srivathsan Chemical Engineering Formaldehyde perfluorosulfonic acid membrane optical response sensor An optical sensor has been developed to selectively respond to the presence of formaldehyde with less than one part per million (ppm) sensitivity but sufficiently portable for field and home use. The approach is based on the use of solid acid catalyst membranes to promote the formation of immobilized colored product from organic vapors present in the ambient. This approach has not previously been explored for formaldehyde detection. The limitations of other methods of detection of formaldehyde for potential real-time application at homes or offices are that they are expensive, bulky and less durable. With the growing interest for a low cost, portable, fast and sensitive sensor to detect low levels of formaldehyde in indoor air and the classification of formaldehyde as a carcinogen by the U.S. Department of Health and Human Services in 2011, the proposed project is very timely.The solid acid catalyst used in this study is a perfluorosulfonic acid (PSA) membrane that acts both as a durable support for an incorporated dye molecule (resorcinol) and as catalyst for the reaction between the dye and formaldehyde. Product identification was carried out by using the Electrospray Ionization technique which confirmed the formation a large polymer network product due to the addition and condensation reaction between resorcinol and formaldehyde. This unique chemical product that is formed within the membrane as a result of the reaction ensures a highly selective optical response in the visible region of the electromagnetic spectrum. Experiments were conducted with four different aldehydes namely; acetaldehyde, glutaraldehyde, benzaldehyde, butyraldehyde to confirm the selectivity of this catalytic optode approach towards formaldehyde. This approach avoids the multi-sensor arrays otherwise employed to provide selectivity when more generic chemical processes are used for optical sensing (i.e., protonation/deprotonation and metalloporphyrin ligand binding). Such improved selectivity using visible light is the basis for the high degree of miniaturization that is possible utilizing this approach. Evaluation of membranes of different thicknesses revealed that the kinetic response of the color change is analogous to a Fickian diffusion process and suggests that the optical response is limited by mass transfer. The diffusion coefficient of formaldehyde into the membrane was determined using the initial slope method for an ambient agent concentration that is time — independent and found to be 2.24*10-12 m2/s for a 7 mil membrane at 5000 ppm exposure. Water interference studies were carried by conducting the formaldehyde exposure at 100% relative humidity which indicated the absorbance degrades in the presence of water. Consequently, this approach is not suitable for detection of liquid-phase formaldehyde concentrations or in high humidity environments. 2013 English text University of Cincinnati / OhioLINK http://rave.ohiolink.edu/etdc/view?acc_num=ucin1384428049 http://rave.ohiolink.edu/etdc/view?acc_num=ucin1384428049 unrestricted This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws. |
| collection |
NDLTD |
| language |
English |
| sources |
NDLTD |
| topic |
Chemical Engineering Formaldehyde perfluorosulfonic acid membrane optical response sensor |
| spellingShingle |
Chemical Engineering Formaldehyde perfluorosulfonic acid membrane optical response sensor Ravi, Srivathsan Continuous Monitoring and Removal of Formaldehyde Vapor in Ambient Air Using Polymer Catalyst Membranes |
| author |
Ravi, Srivathsan |
| author_facet |
Ravi, Srivathsan |
| author_sort |
Ravi, Srivathsan |
| title |
Continuous Monitoring and Removal of Formaldehyde Vapor in Ambient Air Using Polymer Catalyst Membranes |
| title_short |
Continuous Monitoring and Removal of Formaldehyde Vapor in Ambient Air Using Polymer Catalyst Membranes |
| title_full |
Continuous Monitoring and Removal of Formaldehyde Vapor in Ambient Air Using Polymer Catalyst Membranes |
| title_fullStr |
Continuous Monitoring and Removal of Formaldehyde Vapor in Ambient Air Using Polymer Catalyst Membranes |
| title_full_unstemmed |
Continuous Monitoring and Removal of Formaldehyde Vapor in Ambient Air Using Polymer Catalyst Membranes |
| title_sort |
continuous monitoring and removal of formaldehyde vapor in ambient air using polymer catalyst membranes |
| publisher |
University of Cincinnati / OhioLINK |
| publishDate |
2013 |
| url |
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1384428049 |
| work_keys_str_mv |
AT ravisrivathsan continuousmonitoringandremovalofformaldehydevaporinambientairusingpolymercatalystmembranes |
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1719435141969870848 |