Sorption coefficient, surface area

Equilibrium Partitioning Experiments. The equilibrium partitioning of americium-III between gray hornblende schist and rock equilibrated water was determined in batch partitioning experiments with rectangular blocks of gray hornblende schist ( 5). The surface area sorption coefficient, K, was determined to be 4.5 . 5 mL/cm where... 

While the exact sorption mechanism may not be clear, the available literature suggests the following generalizations. First, coarser particles (e.g., silica sand) exhibit less binding per mass of solid than corresponding finer particles made of the same material (e.g., porous silica). This is presumably due to the influence of increased solid surface area per mass of sorbent. Thus, values of sorption coefficients for minerals (Kimm = Cimin/Ciw.Mr) are more useful if they are normalized to the solid s surface area rather than its mass. The second tendency we see is that for any... 

Sorption coefficients quantitatively describe the extent to which an organic chemical is distributed at equilibrium between an environmental solid (i.e., soil, sediment, suspended sediment, wastewater solids) and the aqueous phase it is in contact with. Sorption coefficients depend on (1) the variety of interactions occurring between the solute and the solid and aqueous phases and (2) the effects of environmental and/or experimental variables such as organic matter quantity and type, clay mineral content and type, clay to organic matter ratio, particle size distribution and surface area of the sorbent, pH, ionic strength, suspended particulates or colloidal material, temperature, dissolved organic matter (DOM) concentration, solute and solid concentrations, and phase separation technique. 

Whereas several specific soil attributes are advocated as being responsible for DOC sorption in the mineral soil (Table V), it appears that the greater the clay or aluminum and iron oxide content of a soil, the greater its adsorptive capacity for DOC. For example, there is a positive correlation between m (the measure of the affinity of a substance for the sorbent or the partition coefficient) and soil clay content, dithionite extractable iron (Fej), and oxalate extractable aluminum (Al0) (Moore et al., 1992 Nelson et al., 1993 Kaiser and Zech, 1998). Direct measurements of the surface area of soil particles also correlate very well with DOC adsorption capacity (Nelson et al., 1993). Furthermore, Nelson et al. (1993) report that riverine DOC concentrations are negatively correlated to the clay content of watershed... 

It may be deduced from KP = Koc x foc that partition coefficients of hydro-phobic organic compounds in general are dependent upon the chemical of interest (compound-specific properties affect the value of Koc) and the matrix properties of the medium in which it resides. In addition to the fraction of organic carbon present in the sorption phase, additional environmental factors affect partitioning. These factors include temperature, particle size distribution, the surface area of the sorbent, pH, ionic strength, the presence of suspended material or colloidal material, and the presence of surfactants. In addition, clay minerals may act as additional sorption phases for organic compounds. Nevertheless, organic carbon-normalized partition... 

Where the flux J is the flow of gas. The flux is the amount of material transported per unit time through a unit surface area and according to Eq. (9-1) is proportional to the constant partial pressure difference Ap between both sides of the membrane. The proportionality constant P is called the permeability coefficient and is the product of the diffusion coefficient D and the solubility coefficient S (or sorption constant) of the gas in the membrane ... 

Seme and Muller (1987) describe attempts to hnd statistical empirical relations between experimental variables and the measured sorption ratios (R(js). Mucciardi and Orr (1977) and Mucciardi (1978) used linear (polynomial regression of first-order independent variables) and nonlinear (multinomial quadratic functions of paired independent variables, termed the Adaptive Learning Network) techniques to examine effects of several variables on sorption coefficients. The dependent variables considered included cation-exchange capacity (CEC) and surface area (S A) of the solid substrate, solution variables (Na, Ca, Cl, HCO3), time, pH, and Eh. Techniques such as these allow modelers to constmct a narrow probability density function for K s. 

Sorption of PAHs to soil and sediments increases with increasing organic carbon content and with increasing surface area ofthe sorbent particles. Karickhoff et al. (1979) reported adsorption coefficients for sorption of pyrene to sediments as follows sand-9.4-68 silt-1,500-3,600 and clay-1,400-3,800. Gardner et al. (1979) found that from three to four times more anthracene and about two times more fluoranthene, benz[a]anthracene, and benzo[a]pyrene were retained by marsh sediment than by sand. 

Results. Table XIV presents some results obtained when using this method for measuring the equilibrium partition coefficient between distilled water and several silica gels. The sorption of phenanthrene is shown to be a function of surface area for these materials. Tables XV through XVIII present the results obtained for the partitioning of a PAH... 

A typical pattern of change in the time-dependent SSA-normalized distribution coefficient, K (t), as a function of t is shown in Figure 11 for a-Al203, silica gel-40 and -100. It is clear from this Figure that sorption is completed within a few minutes, regardless of that facts that i) the two gel samples have enormous internal surface areas and ii) the particles of these solids have diameters of 63-150 pm. Complete reversible sorption is shown in Figure 12 for silica gel-40, in which both sorption and desorption isotherms coincide, indicating no hysteresis. 

In the adsorption model, the parameter x is a function of available surface area and the enthalpy of sorption. In the absorption model, x is proportional to the amount of available organic matter and inversely proportional to the activity coefficient of chemical dissolved in organic matter. Based on data for PAH sorption to urban aerosols. 

Ksa can be estimated from the snow surface sorption coefficient Tia by multiplication with the specific snow surface area SSA (m g ) and the density p of melt... 

Table II presents an analysis of several experimental observations of the sorption of TCB, dichlorobenzene (DCB), and trichloroethylene (TCE) by various minerals (6, 16). The analysis employs a coefficient, KM, the per-unit-area sorption capacity of mineral surfaces. This general estimator of the reactivity of such surfaces for organic solutes is obtained from the relationship...

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