Thermal Program Desorption Mass Spectrometry of PAHs from Mineral and Organic Surfaces

Abstract

This research investigated the release of polycyclic aromatic hydrocarbons (PAHs) from spiked materials using thermal desorption mass spectrometry. Experimental methods were developed to obtain real-time PAH desorption data through use of a thermal program desorption probe. Data analysis techniques were investigated to explore the thermal desorption profiles of milligram-size samples. Peak temperatures of desorption were observed to vary among PAHs and among sorbents. For the same absorbent, peak temperatures increased with an increase of PAH molecular weights. For the same PAH, peak temperatures increased as the sorbent varied from sand to alumina to XAD-4 to kaolin. These results have been interpreted in terms of a combined model that include both an activation energy and a desorption/volatilization rate coefficient.

Model verification of thermal programmed desorption‐mass spectrometry for estimation of release energy values for polycyclic aromatic hydrocarbons on mineral sorbents

“…These temperature ramp rates were chosen based on machine limitations (ramp rates from 10 to 100Њ/min in 10Њ increments) and previous work conducted by Talley et al [6], which found consistent results using a 10Њ/min temperature ramp rate. These temperature ramp rates were chosen based on machine limitations (ramp rates from 10 to 100Њ/min in 10Њ increments) and previous work conducted by Talley et al [6], which found consistent results using a 10Њ/min temperature ramp rate.…”

“…As recommended by Talley et al [6], all sample vials generally were filled to approximately one-eighth capacity to limit Thermal programmed desorption of PAHs on mineral sorbents interparticle-diffusional influences. Due to its lower density, kaolin sample vials were filled with slightly greater volume.…”

“…In order to build upon the method developed by Talley et al [6], Equation 2 was utilized for all further calculations. In order to build upon the method developed by Talley et al [6], Equation 2 was utilized for all further calculations.…”

“…For application to the TPD data, E ranged from 20 kJ/mol to 140 kJ/mol to encompass the range of values found by Talley et al [6] for similar mineral sorbents and ranged from 10 2 to 10 16 to include the values calculated from experimental data [13]. The model was then applied to thermograms of individual mass homologs.…”

Model study on sorption of polycyclic aromatic hydrocarbons to goethite

“…Based on the occurrence of PAHs in low-organic matter groundwater environments and supported by experimental studies, it is supposed that the mineral phase can play a significant role in the retention of PAHs in soils. A number of sorption studies were performed with pure, well characterized mineral sorbents [16][17][18][19][20][21][22]. There are several competing mechanisms used to explain the sorption of PAHs to the mineral surfaces.…”