Phenanthrene sorption and desorption

Figures 9 and 10 show phenanthrene sorption and desorption isotherms measured for the peat and the shale. The values of organic carbon-normalized are 21.7 and...

Figure 9. Phenanthrene sorption and desorption data for Canadian peat (sorption time = 21 days desorption time =14 days) (Adapted from ref 21).

Fig. 8.47 Phenanthrene adsorption-desorption hysteresis observed for Lachine and Chelsa humic acid aggregate the hysteresis index is given by n. Reprinted from Huang W, Peng, P. Yu, Z. and Fu J (2003) Effects of organic matter heterogeneity on sorption and desorption of organic contaminants by soils and sediments. Appl Geochem 18 955-972. Copyright 2003 with permission of Elsevier...

Karickhoff (1980) and Karickhoff et al. (1979) have studied sorption and desorption kinetics of hydrophobic pollutants on sediments. Sorption kinetics of pyrene, phenanthrene, and naphthalene on sediments showed an initial rapid increase in sorption with time (5-15 min) followed by a slow approach to equilibrium (Fig. 6.7). This same type of behavior was observed for pesticide sorption on soils and soil constituents and suggests rapid sorption on readily available sites followed by tortuous diffusion-controlled reactions. Karickhoff et al. (1979) modeled sorption of the hydrophobic aromatic hydrocarbons on the sediments using a two-stage kinetic process. The chemicals were fractionated into a labile state (equilibrium occurring in 1 h) and a nonlabile state. 

Figure 3.20 Sorption and desorption of phenanthrene from sediment, (a) Concentration in sediment as a function of equilibrium concentration in solution after 4 sorption steps followed by 49 repetitive desorption steps, (b) Concentration in solution after desorption. Numbers denote equilibrium time (days) for desorption steps. [Reproduced with permission from A. T. Kan, G. Fu, M. Hunter, W. Chen, C. H. Ward, and M. B. Thomson, Environ Sci. Technol. 32, 892 (1998). Copyright 1998, American Chemical Society.]...

A recent study reported by LeBoeuf and Weber 49) illustrates the impact of rubbery and glassy matrices on long term sorption/desorption behavior of phenanthrene. In that study, both sorption and desorption isotherm data for these systems were fit to the Freundlich equation, as a simple means for characterizing relative linearity... 

Johnston AE, Goulding KWT, Poulton PR (1986) Soil acidification during more than 100 years under permanent grassland and woodland at Rothamsted. Soil Use Manage 2 3-10 Kahn SU (1982) Bound pesticides residues in soil and plant. Residue Rev 84 1-25 Kan AT, Chen W, Tomson MB (2000) Desorption kinetics from neutral hydrophobic organic compounds from field contaminated sediment. Environ Pollution 108 81-89 Kang SH, Xing BS (2005) Phenanthrene sorption to sequentially extracted soil humic acids and humans. Environ Sci Technol 39 134-140... 

It can be observed from the results that soil composition has a profound influence on the desorption and solubilization behaviors of phenanthrene. It is much more difficult to desorb and solubilize phenanthrene from glacial till than from kaolin, probably due to the strong binding characteristics of phenanthrene to organic matter. The hydrophilicity and concentration of the surfactant/cosolvent affects phenanthrene desorption and solubilization significantly. As hydrophilic surfactants are less prone to sorption onto soil particle surfaces, more surfactant molecules are available for micellar solubilization, resulting in better performance. In addition, more micelles are available for phenanthrene solubilization at higher surfactant concentrations. 

The various stabilities of complexes, the formation of an acidic front in the soil, and the unknown sorption/desorption processes of phenanthrene in the presence of heavy metals and kinematics of these processes necessitated the creation of eight experimental systems. Therefore, each electrokinetic cell (from Cl to C8), representing a different system, has introduced a new contribution to the entire experiment. Subsequently, each system had a different sequence of conditioning liquids supply and time of contaminant removal. 

The intra-particle diffusion of Phenanthrene is studied for three lithological components with different sorption/desorption properties sandstone, light-colored limestone and dark-colored limestone. Parameters of these lithological components resemble data published by Kleineidam et al. (1999) and are summarized in Table 3.1. 

For the numerical modelling of Phenanthrene desorption, again fom runs (run 5-8, see Tab. 3.2) were performed, with hydraulic conditions and lithological compositions according to the preceding sorption runs. It was assumed that initially all litho-components are at sorption equilibrium, and that the concentration of dissolved Phenanthrene in the interparticle space equals 40 (tg/L. Desorption was initiated by setting the Phenanthrene concentration at the column inflow to zero. 

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