Behavior of PAH/mineral associations during thermodesorption: impact for the determination of mineral retention properties towards PAHs

Abstract

Polycyclic aromatic hydrocarbons (PAHs) associated with two minerals (silica sand and bentonite) presenting opposite retention properties were analyzed with a thermodesorption (Td)-GC-MS coupling in order to validate this technique as a new and rapid way to evaluate the solid sorption properties. Two analysis modes were used, evolved gas analysis (EGA) and Td with cryo-trap. EGA allowed a real-time monitoring of the compounds desorbed during a temperature program and gave a first screening of the samples while Td gave more precise indications on compound abundances for selected temperature ranges. When associated with silica sand, PAHs were released at relatively low temperatures (<300 °C) close to corresponding boiling point, whereas for the PAH/bentonite mixture, PAHs were desorbed at much higher temperatures; they were also present in much lower abundance and were associated with mono-aromatic compounds. With bentonite, the PAH abundances decreased and the mono-aromatics increased with the increasing PAH molecular weight. These results indicated a clear PAH retention by the bentonite due to polymerization, followed by a thermal cracking at higher temperatures. The Td-GC-MS was proven to efficiently underline differences in retention properties of two minerals, and this study highlights the great potential of this technique to evaluate compound/matrix bond strength and interaction.

Archaeometric evidence for the earliest exploitation of lignite from the bronze age Eastern Mediterranean

“…In this case, the impact of the substrate is minimal, given that the calcium in the hydroxyapatite matrix of the dental calculus does not promote the formation of PAHs 93 Furthermore, to produce PAHs from thermal cracking a minimum temperature of c. 700 °C is required 93 , 94 , which is significantly higher than the temperatures reached here, preserving the signatures introduced in antiquity. The instrument parameters used for this study were selected on the basis of previous work carried out on optimizing PAH detection and analyses 92 , 93 , 95 , 96 .…”

Fate of pyrene on mineral surfaces during thermal remediation as a function of temperature

“…Polymerization and oxidation of the PAHs was observed by day 60 in the presence of bentonite, smectite, and goethite, and mineralization to CO 2 was observed at higher temperatures (100 °C) after longer periods (80–160 days). 18–21 Also, hematite amended soils were shown to increase removal of PAHs, with >60% of PAHs removed after treatment at 400 °C for 30 min. 22 Metal oxide minerals which contain Lewis acid sites have also been shown to catalyze PAH transformation reactions.…”

Multistep thermodesorption coupled with molecular analyses as a quick, easy and environmentally friendly way to measure PAH availability in contaminated soils

“…In this study, a link between the aging of the contaminated soil and the ability to thermodesorb PAHs is suspected. Indeed, it can be admitted that there is a link between the availability of a compound, the strength to which this compound is retained to the matrix and the energy required to break this bond [32]. The increase in the temperature would bring higher energy capable of desorbing molecules bound with increasing strength.…”