Adsorption model organic compounds

The C, values for Sb faces are noticeably lower than those for Bi. Just as for Bi, the closest-packed faces show the lowest values of C, [except Bi(lll) and Sb(lll)].28,152,153 This result is in good agreement with the theory428,429 based on the jellium model for the metal and the simple hard sphere model for the electrolyte solution. The adsorption of organic compounds at Sb and Bi single-crystal face electrodes28,152,726 shows that the surface activity of Bi(lll) and Sb(lll) is lower than for the other planes. Thus the anomalous position of Sb(lll) as well as Bi(lll) is probably caused by a more pronounced influence of the capacitance of the metal phase compared with other Sb and Bi faces28... 

Goss, K.-U., Conceptual Model for the Adsorption of Organic Compounds from the Gas Phase to Liquid and Solid Surfaces, Environ. Sci. Technol, 31, 3600-3605 (1997). 

Special care must always be exercised in the study of parts-per-billion concentrations of organics in water to ensure minimal losses due to sample degradation, adsorption or absorption to process materials, and other similar losses. These issues were addressed by dividing the measurement procedures into two parts (1) sample preparation and (2) analytical method, or finish. Because well-defined sample preparation steps were not available from the literature for the quantitative determination of parts-per-billion concentration levels of most of the model organic compounds in water, a considerable amount of effort was placed on the development of appropriate procedures for such measurements. In particular, each method was developed with the indent to have a procedure that could verify the presence of appropriate concen-... 

Adsorption of Model Organic Compounds on Surfactant Treated Cellulose Fibres... 

The experimental study of the adsorption of organic compounds on electrodes began in the first decade of the previous century with Gouy s electrocapillary work. Since then it has attracted considerable attention, mainly because it affects the mechanism of most of the processes occurring on electrodes. The first attempts to present a theoretical description of the effect of the electric field on adsorption appeared in 1925 and 1926 by Frumkin, who formulated the macroscopic model of condensers in parallel. The interpretation of the electrosorption of organic compounds at a molecular level was initiated by Butler" in 1929, but it was the work of Bockris and co-workers in 1963 that put the bases of the contemporary microscopic modelling. The main contribution by Bockris et al. was the introduction of the concept of the competition between solvent and adsorbate molecules for adsorption and the reorientation of the adsorbed molecules on the electrode upon the variation of the electric field. ... 

Dachs, J. and Bayona, J.M. (1997). Langmuir-derived model for diffusion- and reaction-limited adsorption of organic compounds on fractal aggregates. Environ. Sci. Technol., 31, 2754-2760. 

Some adsorptive kinetic models were used in different works of adsorption of organic compounds in organophilic clays, including models of Lagergren, also called models of pseudo-first order and pseudo-second order, represented by Equations 13 and 14 (Akgay, 2004, 2005 Cavalcanti et al., 2008 Yilmaz Yapar, 2004). 

The meticulous study of the effects of adsorption of organic compounds on the electrocapillary curves of mercury, which was accomplished by Frumkin at the Karpov Institute, led to the discovery of the famous isotherm that now bears his name (the Frumkin isotherm [7]). Whereas the Langmuir isotherm was based on the somewhat naive assumption that adsorbed species did not interact, Frumkin showed that such interactions were often very strong indeed. In addition, Frumkin combined his results with an electrical model of two capacitors in parallel, which later became the prototype for many multistate models. 

Goss, K.U., Conceptual model for the adsorption of organic compounds from the gas phase to liquid and solid surfaces. Environmental Science andTechnology, 1997.31(12) 3600-3605. 

Fig. 3. A model integrated adsorption/electrothermal regeneration/cryogenic vapor recovery system for volatile organic compounds [91]. Reprinted from Gas Sep. Purif, Volume 10, Lordgooei, M., Carmichael, K. R., Kelly, T. W., Rood, M. J. and Larson, S. M., Activated carbon cloth adsorption cryogenic system to recover toxic volatile organic compounds, pp. 123-130, Copyright 1996, with permission from Elsevier Science.

In the presence of NAPL, the concentration of contaminants in the soil moisture (Cw) can be calculated simply from the solubility of the compounds (equation 3 in Table 14.3). Adsorption of contaminants to the soil particles is a much more complex phenomenon, which depends both on contaminant properties and on soil characteristics. The simplest model for describing adsorption is based on the observation that organic compounds are preferentially bound to the organic matter of soil, and the following linear equation is proposed for calculating the adsorbed concentration (Cs) ... 

Models describing the adsorption of water-miscible organic compounds on natural materials have not been correlated with field observations under typical injection-zone conditions. Few computer codes contain algorithms for calculating the distribution of species between the adsorbed and aqueous states. 

The Langmuir model has been used to describe adsorption behavior of some organic compounds at near-surface conditions.137 However, three important assumptions must be made ... 

Table IV uses DBCP to illustrate the effect of soil organic carbon concentration on leaching mobility. In the very low organic carbon soil, there is almost no adsorption for the compound and the leaching model breaks down because it predicts penetration depths greater than the water penetration. In these cases the prediction is adjusted to show compound and water penetration depths as the same.

Adsorption and Film Formation. Inhibition of HC1 corrosion by organic compounds is a complicated multi-step process. Nevertheless, the effect of an inhibitor on corrosion of a metal is often treated mathematically with an equilibrium adsorption model for displacement of water (19,20) ... 

The evidence presented in the literature on the dominance of a partition mechanism in the process of adsorption of a nonionic organic pollutant onto SOM does not mean, for instance, that the physical adsorption model based on weak chemical forces of interaction can be ignored or excluded [82,99,107,109, 114,115,183,192,204-218]. The following summary is a critical evaluation for reconsidering the universal applicability of the partitioning model to various nonionic compounds onto SP0M [82,84,92,103,113,130,182,184,185,187,193, 219,220,222-226] ... 

The adsorption of some neutral organic compounds on the individual faces of zinc single-crystal electrodes was described by the Frumkin-Damaskin theory with the use of two parallel capacitors model [14]. For pc-Zn electrode, a departure from the two parallel capacitors model due to the energetic inhomogeneity of the surface was observed. 

The other isolation methods evaluated employed solid adsorbents to isolate the model solutes (6-8). The first of these used XAD-4, a macroreticular, polystyrene-divinylbenzene resin (Rohm and Haas), into which trimethylamine groups had been introduced (9). The purpose of the resulting quaternary ammonium functional groups was to allow more efficient adsorption of acidic compounds without an appreciable loss of capacity for hydrophobic compounds. This feature is important because the vast majority of the organic matter in potable water is neutral or acidic in nature (JO). 

Malcolm et al. (14) and Thurman et al. (15) noticed that the adsorption of solutes onto XAD-8 macroreticular resin could be predicted by means of a linear correlation between the logarithm of the capacity factor and the inverse of the logarithm of the water solubility of each compound. Their investigation, however, was limited to approximately 20 selected organic compounds in individual aqueous solutions. By comparing the results shown in Table II and the water solubility properties of each model compound used in this study (see Table I), it appears that the predictive model could serve for a first estimate of the recovery of multisolute solutions at trace levels. However, low recoveries and the erratic behavior of several compounds included in this study suggest that additional factors need to be considered. 

In addition to the ability of TGA to quantify the thermal character of soil and sediment organic matter, it has been employed to study the adsorption of volatile organic compounds onto soil and sediment organic matter. For example, Boussehain et al. (1986) used TGA to study alcohol adsorption on charcoals, from which adsorp-tion/desorption isotherms were developed at various temperatures and adsorption models were used to lit experimental data. In addition, Risoul et al. (2002) performed laboratory pilot studies on thermal desorption of polychlorinated biphenyls (PCBs) from a contaminated soil. This study indicated that TGA appears to be a promising tool to determine optimum operating thermal extraction conditions. 

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