Adsorption of PAH

More recently Simcik [84] has shown that adsorption of PAHs to the surface of a rain drop may be much more important than previously thought and has modified Eq. 9 to include surface adsorption ... 

The phase that is most commercially available contains a weak TT-electron acceptor mononitrophenyl bonded to the sUica and usually contains a propyl spacer arm. This packing interacts with analytes through rr-donor interactions. Other nitrophases exist and, as the number of nitro groups increases on these acceptor-type phases, an increased retention of aromatic donor compounds occurs. The phases of 3-(2,4-dinitroanilino)-propyl and (2,4,6-trinitronanilino)-propyl have shown preferential adsorption of PAHs, alkyl aromatic hydrocarbons, and polyarylalkanes, in comparison to aminopropyl silica [3]. 

Moreover, because of the presence in the tank of many types of materials (including natural organic particulates, polymeric devices, semi-permeable membranes and solid sorbents used for other types of measurements), a partial adsorption of PAHs leading to concentration depletion, at least at the beginning of the exercise, of the dissolved (free) PAHs is also highly plausible. This may also contribute to some extent to the low concentrations found for the four PAHs (ANTH, BaA, CHRY, and PYR) from samplings T4 to T9. 

People exposed to PAHs in conjunction with particulates from tobacco smoke, fossil-fuel combustion, coal fly ash, and asbestos fibers are at increased risk of developing toxic effects, primarily cancer. Even people not susceptible to the toxic effects of PAHs may become affected when exposure occurs in conjunction with exposure to particulates (NRC 1983). This enhanced effect results from the adsorption of PAHs onto the particulates. They are vacuolized into cells, and distributed differently in tissues depending on the size and type of particulate matter. This increased PAH uptake may result in more efficient induction of AHH activity at low PAH concentrations. This activity also increases the dose to the gastrointestinal tract as a result of mucocilliary clearance (NRC 1983). This synergistic action between PAHs and particulate matter in air pollution has been associated with the occurrence of stomach cancer in humans (Fraumeni 1975). 

The adsorption of PAHs was a combination of two factors, van de Waals force and a thermodynamic gradient determined by the hydrophobicity driving them out of the solution. Adsorption was dominated by van der Waals attractive forces between instantaneous and induced dipole moments of molecules (Gauthier et al., 1987). Dipole moments depended upon the polarizability and could be estimated by the sum of bond moments in the molecule. An increase in the numbers of C=C double bonds should contribute to molecular polarizability and thereby increase the van der Waals attraction strength. As a result, heavy molecular weight PAHs with more C=C double bonds should be adsorbed more efficiently to sediment particles. 

Fig. 23 AR ,p, i.e. difference in specific water relaxation induced by adsorption of PAH to iatex particles. Left in aqueous solution. Right in 0.25 M NaCi soiution.

Fig 25 ARisp for the adsorption of PAH to latex particles precoated with two double layers of (PAH/PSS). Solid symbols PAH adsorbed in H2O, open symbols in 0.25M NaCI. The precoated particles serve as reference, and represents the water immobilisation due to adsorption of the fifth layer. 

To assess the feasibility of reduction of PAH emissions by temperature-assisted adsorption of PAH on fly ash in the bag-filter house of coal-fired installations, it is necessary to gain an insight into the adsorption behaviour of PAH on fly ash. Insufficient knowledge of this behaviour is available from the literature. 

For the evaluation of the importance of carbon content on the adsorption behavioiu, we will separate a sample into several size fractions, in order to preconcentrate the fly coke. It was found, however, that many carbon particles are larger than any other component of the apeldoom fly ash TNO 3. So, the fraction of particles>180 pm mostly contains unbumt carbon particles. Separation and analysis of this fraction, after spiking the fly ash, may answer the question of preferred adsorption of PAH onto carbon. 

A proper choice of the dipping time presupposes a study of the adsorption kinetics. In situ measurements of the adsorption of PAH (from a 0.01 M solution with 0.5 M MnCl2 added) on a PSS-coated optical waveguide showed that the adsorption is practically completed after 3 minutes [107]. It was shown that the kinetics of adsorption are not transport limited. Similar results hold for subsequent polyelectrolyte adsorption. Ellipsometric measurements of the thickness of... 

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