Applications of Equilibrium Thermodynamics - Elements of Environmental Engineering: Thermodynamics and Kinetics - page 182

4.38 2 Aspillof1,2-dichloroethane(DCE)occurredinachemicalplantproducing
pesticides. Because of the delay in cleanup some of the material seeped
into the groundwater flowing at a velocity of 1.5 m/d. The soil at the site
has an organic carbon content of 0.001, a porosity of 0.3, and a bulk density
of 1.4 g/cm 3 . The nearest community that receives drinking water from the
aquifer is located 500 m away in the direction of groundwater flow. How
long will it take for the chemical to show up in the community drinking
water? Assume no biodegradation of DCA.
4.39 3 K aw values for p , p -DDT (a pesticide) at various temperatures were
obtained for deionized water and saline water (Cetin et al., 2006). From
the data calculate the following:
(i) Δ H a → w , (ii) Δ S a → w , and (iii) Setschenow constant for salting out.

K aw /[ − ]

T ( ◦ C) Deionized Water Saline Water (0.5 M NaCl)

5 0.19 ± 0.04 1.17

15 0.52 1.9 ± 0.63

20 0.69 ± 0.15 —

25 0.97 ± 0.27 3.4 ± 0.64

35 2.8 ± 0.39 5.5

4.40 2 Hexabromobenzene (HBB) is found along with flame-retardant materials
suchasincarpets,bedding,insulation,andfurnitureaccessories.Itisfound
as a contaminant in soils and sediments in our waterways. It has a structural
formula of C 6 Br 6 , a molecular weight of 557.52, and a melting point of
327 ◦ C. (a) Determine the log K ow of HBB using a group contribution
method and a derivative method. (b) From the data in (a) determine the
aqueous solubility of BHH expressed in mol/L. (c) From the above data
determine the sediment-water partition constant K sw using an appropriate
correlation. The organic fraction of the soil is 0.05; neglect the mineral
contribution to adsorption. (d) Ten grams of soil with 10 μ g/kg of HBB
are mixed with 100 mL of water and agitated for 24 h. The solution was
allowed to reach equilibrium and the solid fraction separated. It was found
to contain HBB at a concentration of 5 μ g/kg. What is the concentration
of HBB in the water that was separated?
4.41 3 2,3-Dichlorophenol is a contaminant resulting from wood and pulp indus-
try operations. It has a molecular weight of 163, a melting point of 45 ◦ C,
and a boiling point of 210 ◦ C. (a) Obtain the octanol-water partition con-
stant of the compound; (b) from (a) obtain the aqueous solubility of the
compound; (c) obtain the vapor pressure of the compound from an appro-
priate correlation; (d) using data from (b) and (c) obtain the Henry's
constant, expressed in dimensionless molar ratio; and (e) a wastewater
stream of 100 m 2 and a depth of 1 m is contaminated with the compound
at a concentration of 1 μ g/L. A measurement of flux to air showed 10 μ g
in a chemical trap obtained in 1 h of sampling. What is the concentration
of the chemical in ambient air above the stream? Note that the individual
water- and air-side mass transfer coefficients for the chemical are 1 ×
10 − 5 m/s and 0.005 m/s, respectively.