Environmental Engineering Reference
In-Depth Information
∏
N
j=1,2,…,N
x
(5.27)
a
eq
XK
=
c
C
ij
j
j
i
i
=
1
where,
K
j
eq
is the equilibrium constant for aqueous reaction
j
. The rate of
accumulation of component
i
due to aqueous reaction
j
(
R
j
aq
) is:
(5.28)
RaR
ji
aq
=
ji
j
The total rate of accumulation of component
i
due to all aqueous reactions
is given as:
N
N
∑∑
R
aq
=
X
R
aq
=
X
a R
(5.29)
i
ji
ji
j
j
=
1
j
=
1
5.3.5.3 Precipitation/dissolution reactions
It is important to incorporate the precipitation/dissolution reactions in
the mass transport model. In precipitation reactions, the chemical compo-
nents are assumed to be composed of products expressed as:
∑
N
c
j
=1,2,…,N
p
(5.30)
P
→
b C
j
ij
i
i
=
1
Where,
P
j
is the chemical formula for precipitate
j
,
b
ij
is the stoichio-
metric coefficient in precipitate j for component
i
, and N
p
is the number
of precipitates for component
i
. The production of the precipitate will not
occur until the solution is saturated. Therefore, the law of mass action is
written as:
N
∏
b
j
=1,2,…,N
p
(5.31)
SP
K
≥
c
C
ji
j
i
i
=
1
where,
K
j
SP
is the solubility product equilibrium constant for precipitate
j
. The total rate of production of component
i
due to precipitation/dissolu-
tion reactions (
R
j
p
) is:
N
N
∑∑
p
p
p
R
=
p
R
=
p
b R
(5.32)
i
ij
ji
j
j
=
1
j
=
1
where,
R
j
p
is the rate of production of precipitate
j
.
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