6.2.3.3 Dissolution
Dissolution is a process in which solid, liquid, or gas become solutes into a liquid to
form a homogeneous solution. It defines the concentration of a pollutant in the
dissolved form and persistence of the DNAPL phase. Besides water solubility, many
parameters have an influence on the dissolution, such as groundwater velocity,
surface contact between water and DNAPL, or the diffusion coefficient of species
in water (Pankow and Cherry 1996).
Dissolution of a mixture of chlorinated compounds is influenced by the respective
solubility of each compound. Raoult’s Law—valid for ideal (or diluted) solution—
can be applied to approximate the aqueous phase concentration of each compound
i (Pankow and Cherry 1996).
C i ¼ x i à C sat
ð6:12Þ
where C i is the molar solubility of i in water in the mixture (mol L
À1 ), x i is the molar
fraction of i in the mixture (dimensionless), and C sat is the molar solubility of i in its
pure form (mol L
À1 ). This relationship can be used for mixtures of chlorinated
compounds because they have a similar chemical structure.
Mass transfer rate N (kg s
À1 ) can be expressed by the equation:
N ¼ K C Ã ΔC Ã A S
ð6:13Þ
where K c is the mass transfer coefficient (m s
À1 ), ΔC is the difference in concentration between pure phase and aqueous phase (dissolved pollutant) (kg m
À3 ), and A S is
the contact surface between the two phases (m
2 ).
6.2.3.4 Volatilization
Volatilization is the phenomenon of vaporization of a dissolved solute. Even if
Raoult’s law can be used, the mathematical relationship characterizing the equilibrium between the aqueous phase and the gas phase is the Henry’s law:
p i ¼ H Ã C i
ð6:14Þ
where p i is the partial pressure of i (Pa), C i is the concentration of i in the liquid phase
(mol L
À1 ), and H is the Henry’s law constant of i (Pa L mol
À1 ). The unit of the
Henry’s law constant can vary according to the writing of the law and the quantities
used (molar fraction, concentration, or molality).
Volatilization is an important parameter to model the fate and distribution in
groundwater of very volatile compounds, e.g., PCE or VC (Schwarzenbach et al.
2003; Alvarez and Illman 2005b).
6 In Situ Chemical Reduction of Chlorinated Organic Compounds
295
Dissolution is a process in which solid, liquid, or gas become solutes into a liquid to
form a homogeneous solution. It defines the concentration of a pollutant in the
dissolved form and persistence of the DNAPL phase. Besides water solubility, many
parameters have an influence on the dissolution, such as groundwater velocity,
surface contact between water and DNAPL, or the diffusion coefficient of species
in water (Pankow and Cherry 1996).
Dissolution of a mixture of chlorinated compounds is influenced by the respective
solubility of each compound. Raoult’s Law—valid for ideal (or diluted) solution—
can be applied to approximate the aqueous phase concentration of each compound
i (Pankow and Cherry 1996).
C i ¼ x i à C sat
ð6:12Þ
where C i is the molar solubility of i in water in the mixture (mol L
À1 ), x i is the molar
fraction of i in the mixture (dimensionless), and C sat is the molar solubility of i in its
pure form (mol L
À1 ). This relationship can be used for mixtures of chlorinated
compounds because they have a similar chemical structure.
Mass transfer rate N (kg s
À1 ) can be expressed by the equation:
N ¼ K C Ã ΔC Ã A S
ð6:13Þ
where K c is the mass transfer coefficient (m s
À1 ), ΔC is the difference in concentration between pure phase and aqueous phase (dissolved pollutant) (kg m
À3 ), and A S is
the contact surface between the two phases (m
2 ).
6.2.3.4 Volatilization
Volatilization is the phenomenon of vaporization of a dissolved solute. Even if
Raoult’s law can be used, the mathematical relationship characterizing the equilibrium between the aqueous phase and the gas phase is the Henry’s law:
p i ¼ H Ã C i
ð6:14Þ
where p i is the partial pressure of i (Pa), C i is the concentration of i in the liquid phase
(mol L
À1 ), and H is the Henry’s law constant of i (Pa L mol
À1 ). The unit of the
Henry’s law constant can vary according to the writing of the law and the quantities
used (molar fraction, concentration, or molality).
Volatilization is an important parameter to model the fate and distribution in
groundwater of very volatile compounds, e.g., PCE or VC (Schwarzenbach et al.
2003; Alvarez and Illman 2005b).
6 In Situ Chemical Reduction of Chlorinated Organic Compounds
295