The contamination of water-saturated soils with toxic organic solvents is an important environmental problem. The organic solvents can dissolve into to the water and diffuse through the water-saturated soil by molecular diffusion, resulting in contamination of the soil and the water. The figure below illustrates a very simplified view of this situation, where liquid tetrachioroethylene (TCE, species A) rests at the bottom of a pore filled with stagnant liquid water. The depth of the organic (TCE) layer is 0.10 cm, and the total length of the pore is 3.1 cm. The top of the pore is €œcapped€ with a clay layer so that the contaminated water is contained within the pore. The diameter of the pore is not known. The density of the liquid TCE is 1.6 g/cm³, and the density of liquid water is 1.0 g/cm³. The molecular diffusion coefficient of TCE in liquid water is 8.9 × 10^-6cm²/s at 293 K. The solubility limit of TCE in water is 1.00 × 10^-6gmole/cm³of the aqueous phase. The molecular weight of TCE is 166 g/gmole.a. Initially, there is no TCE dissolved in the water. How long will it take for the TCE concentration in the water to reach 8.97 × 10^-8gmole/cm³at a position of 0.3 cm from the organic-aqueous interface?
b. What is the TCE concentration in the aqueous phase after infinite time (t †’ ˆž)?

Transcribed Image Text:

Clay barrier (cap) Impermeable material 3.1 cm Aqueous layer Liquid TCE (0.1 cm depth)