Applications of Equilibrium Thermodynamics - Elements of Environmental Engineering: Thermodynamics and Kinetics - page 179

(i) Which isotherm (Freundlich or Langmuir) would better represent the
data?
(ii) What is the maximum adsorption capacity of carbon I and II?
(iii) If the effluent water quality for benzene is 20 μ g/L, how much of
carbon would be required per day? Which carbon type would you
recommend?
4.17 2 The sediment in University Lake near Baton Rouge is known to be con-
taminated with PCBs (predominantly trichlorobiphenyl) to an average
concentration of 10 μ g/kg. The sediment has an f oc of 0.04. Calculate
the PCB loading ina1lbcatfish dwelling in the lake.Assume equilibrium
between the various phases in the system.
4.18 2 Inorganic Hg (HgCl 2 , Hg(OH) 2 ) can be deposited to a water body via wet
and dry deposition. Consider the Henderson Lake, a small lake east of
Lafayette, Louisiana, where an Hg advisory was issued by the Louisiana
Department of Health and Hospitals in 1996. The lake is approximately
7.2 m in depth. Consider a global average atmospheric concentration of
HgCl 2 = 0.1 ng/m 3 . Estimate the deposition rate of HgCl 2 to the lake.
An average annual rainfall of 0.1 cm/h can be assumed. K aw for HgCl 2 is
2.9 × 10 − 8 .
4.19 2 Estimate the fractional mass of a pesticide (aldrin) that is washed out by
rainfall at an intensity of 1 mm/h over an area 10 4 m 2 . Appendix 1 gives
the physicochemical data for aldrin.
4.20 3 A closed storage vessel is filled with water and ethanol (mole fraction
0.002). The vessel is only 60% full. If equilibrium is established above
the solution, what is the partial pressure of ethanol in the vapor? Does
the vessel stand to explode? The OSHA explosion limit for ethanol is
1000 ppmv.
4.21 3 Vapor, aerosol, and rainwater concentrations of a PCB (2,2 ,4-isomer) in
an urban area are given below:
Vapor: 100 pg/m 3 ; aerosol: 0.3 pg/m 3 .
Estimate the total washout ratio for this compound at an ambient tem-
perature of 25 ◦ C. log K ow = 5.7, log P i (atm) =− 6.5. Compare the
theoretical and experimental washout ratios. The average surface area of
an aerosol is 1 × 10 − 6 cm 2 /cm 3 air and ρ i = 1.7 × 10 − 4 atm cm.
4.22 2 The concentration of sulfate in the atmosphere over oceans is
− 0.06 μ g/m 3 . If the water content of cloud is 1 g/m 3 , estimate the pH
of cloud water. Assume that all the sulfate exists as sulfuric acid.
4.23 2 Based on the data in Table 4.12, estimate the percent gas-phase resis-
tance for evaporation of the following chemicals from water: naphthalene,
chloroform, PCB, and ammonia.
4.24 3 Below the water table, the groundwater aquifer is a closed system with
respect to exchange of CO 2 with a separate vapor phase. Without an exter-
nal source or sink for dissolved CO 2 in groundwater (i.e., no carbonate)
the dissolved carbon concentration should be constant. Assuming that the
ground water at the water table is in equilibrium with the atmosphere with