Environmental Engineering Reference
In-Depth Information
movement of chlorine through the water to the surface of the adsorbent particle, is
0.0017 cm
s. The second, resistance to movement of chlorine into the solid particle,
is 0.000 65 cm
/
s. If all of the chlorine is to be removed and the solid adsorbent
initially has no chlorine, what is the maximum flux of chlorine in mg
/
/
cm
2
·
s?
3.19 A solution of 48% sucrose (sugar) by weight contains a small quantity of impurities.
The impurities will be removed with a carbon adsorbent. The equilibrium follows a
Freundlich isotherm,
Y
mX
n
, where
Y
has units of mg impurity
=
/
kg sugar and
X
has units of mg impurity
/
kg carbon. The isotherm constants are
n
=
2.2 and
m
=
10
−
7
.
(a) For a single-stage process, how much carbon per 1000 kg of feed solution is
needed to reduce the impurity level from 20 mg to 2.5% of its original value?
(b) Consider a countercurrent operation in which 5 kg of carbon is contacted with
1000 kg of the feed solution. How many stages are needed to reduce the impurity
level from 20 mg to 1 mg?
3.20 Adsorption of organics using activated carbon follows a linear isotherm: (
x
8
.
0
×
m
)
KC
e
.
To process a volume
V
of fluid containing an initial concentration
C
0
of organics, it
is suggested to divide the total mass
M
of sorbent into three equal parts and contact
the fluid with
M
/
3 mass of sorbent in three consecutive batch contacts, allowing
equilibrium to be reached with each contact.
(a) Find the concentration after each batch contact in terms of initial concentration
C
0
and constants.
(b) Find the total amount of organics sorbed in terms of
C
0
and constants.
(c) Explain the advantages and disadvantages of this approach compared to a single
contact with mass
M
of sorbent.
/
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