Standard Test Method for Distribution Coefficients of Inorganic Species by Batch Method

Importancia y uso:

4.1 The distribution coefficient, K_d, is an experimentally determined ratio quantifying the distribution of a chemical species between a given fluid and solid material sample under certain conditions, including the attainment of constant aqueous concentrations of the species of interest. The K_d concept is used in mass transport modeling, for example, to assess the degree to which the movement of a species will be delayed by interactions with the local geomedium as the solution migrates through the geosphere under a given set of underground geochemical conditions (pH, temperature, ionic strength, etc.). The retardation factor (R_f) is the ratio of the velocity of the groundwater divided by the velocity of the contaminant, which can be expressed as:

where:

ρ_b   =   bulk density of the porous medium (mass/length³), and η_e   =   effective porosity of the medium (unitless) expressed as a decimal.

4.2 Because of the sensitivity of K_d to site specific conditions and materials, the use of literature derived K_d values is strongly discouraged. For applications other than transport modeling, batch K_d measurements also may be used, for example, for parametric studies of the effects of changing chemical conditions and of mechanisms related to the interactions of fluids with solid material.

Subcomité:

C26.13

Volúmen:

12.01

Número ICS:

13.080.99 (Other standards related to soil quality), 71.040.40 (Chemical analysis)

Palabras clave:

adsorption; attenuation; batch sorption; distribution coefficient; geochemical; ground water; ion exchange capacity; isotherm; liquid migration; short-term batch;