Good for the adsorption study

1. CIVIL ENGINEERING DEPARTMENT
NATIONAL INSTITUTE OF TECHNOLOGY PATNA
PATNA - 800 005
Nityanand Singh Maurya
Water Treatment
(Adsorption)

2. Adsorption:
 Surface phenomena
 Accumulation or concentration of substance at a surface
 Adsorbate and Adsorbent
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Adsorption
Types of adsorbent (material):
 Activated carbon
 Activated silica
 Activated alumina
 Charcoal
 Biological materials

3. Adsorption…
Types of adsorbent (size):
 Powder (PAC)
 Granular (GAC)
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4. Adsorption…
Adsorption experiment
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5. Adsorption…
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6. Adsorption…
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7. Adsorption…
Adsorption Isotherm Models (relationship between q and Ce):
 Langmuir
 Freundlich
Langmuir:
e
m e
e
Q bC
Q 
1 bC
Where
Qe
Qm
b
Ce
=solid phase sorbate concentration, mg/g
= quantity of sorbate required for monolayer coverage of the sorption sites. It is
also known as monolayer capacity (mg/g)
= Constant related to the heat of adsorption,
= equilibrium concentration of the solute, mg/L
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8. Adsorption…
Langmuir Model:
Freundlich Model:
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9. Adsorption…
Batch adsorption process:
Initially q = 0, C = C0
As adsorption proceeds, the system
follows a path on the straight line
At equilibrium, the system is represented
by the point of intersection of the straight-
line adsorption path and the curved
adsorption isotherm
Slope of adsorption path = -V/W
Equation of path line, q=-(V/W)(C0-C)
dq/dC = -V/W
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10. Adsorption…
Single stage system:
q= 𝑉(𝐶0
−𝐶1
)
𝑊
w= 𝑉(𝐶0
−𝐶1
)
𝑞
If system follows a Freundlich isotherm:
w= 𝑉(𝐶0
−𝐶1
)
𝐾
𝐶
1/𝑛 1
If system follows a Langmuir isotherm:
w= 𝑉(𝐶0−𝐶1)(1+𝑏𝐶1)
𝑏
𝑞
𝑚
𝐶
1
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11. Adsorption…
Solution:
Given data
C0 = 0.12 mg/L
Ce = 0.05 mg/L
Kf = 2.6
1/n = 0.73
Amount of PAC = //
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12. Adsorption…
Multiple stage system:
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13. Adsorption…
Multiple stages having equal carbon amount: W1 = W2
If system follows Freundlich isotherm:
w= 𝑉(𝐶0
−𝐶1
)
1
𝐾𝐶1/𝑛
𝑉
(
𝐶
0
− 𝐶1
)
=
𝑉
(
𝐶
1
−𝐶2
)
𝐾
𝐶
1/𝑛
𝐾
𝐶
1/𝑛1
2
(𝐶0− 𝐶1
)
=
(𝐶1−𝐶2
)
𝐶1
/
𝑛
𝐶1
/
𝑛
1 2
If system follows Langmuir isotherm:
(𝐶0− 𝐶1)(1+𝑏
𝐶
1
)
𝐶
1
=
(𝐶1− 𝐶2)(1+𝑏
𝐶
2
)
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𝐶
2

14. Adsorption…
Optimal division of a fixed carbon to maximise overall solute removal :
W1 + W2 = W
If system follows Freundlich isotherm:
K𝐶1/𝑛
1
K𝐶1/𝑛
2
W1
𝑊1 = 𝑉(
𝑊2 = 𝑉(
C1
𝐶
0−𝐶1
)
𝐶
1−𝐶2
)
W2=(W-W1)
Plot a graph between
Amount of carbon used in stage 1 (g) : X-axis
Effluent concentration from stage 2 (g/L) : Y-axis
C2
0 500
50 450
100 400
150 350
200 300
250 250
300 200
350 150
400 100
450 50
500 0
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15. Adsorption…
Total carbon = 500 g; first stage C0 = 1 g/L, Liquid Vol = 100 L each, determine
optimal division of the carbon for minimal concentration of the effluent (2nd
stage)
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16. Adsorption…
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17. Adsorption…
Two stage counter current treatment:
Total amount of carbon required to reduce the concentration of a contaminant to a specified
level in a multistage system may be made even smaller by use of countercurrent flow of liquid
and solid as shown below:
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18. Adsorption…
Application PAC and GAC:
Application of GAC in adsorption column:
• Downflow mode
• Upflow mode
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19. Adsorption…
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Breakthrough = 5 % of C0
Exhaustion of media = 95 % of C0
Mass Transfer Zone (MTZ):
The area of the GAC bed in which sorption is occurring is called MTZ
Application of GAC in adsorption column:

20. Adsorption…
Length and shape of breakthrough curve is a function of
 Hydraulic loading rate
 Characteristics of activated carbon
 Characteristics of adsorbate
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21. Adsorption…
Length and shape of breakthrough curve
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22. Design of Adsorption Column
Bed – depth – service time approach (Bohart and Adam model)
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23. Design of Adsorption Column……
Bed – depth – service time approach (Bohart and Adam model)……
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24. Design of Adsorption Column……
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Bed – depth – service time approach (Bohart and Adam model)……
Laboratory Procedure:
Steps
1. Pass water through an adsorption column (known diameter and adsorbent amount) at
constant flow rate and measure effluent concentration of target pollutant.
2. As the effluent concentration reaches at defined breakthrough concentration, the time
of breakthrough is noted together with the column depth.
3. Now the second column is added in series and the experiment is continued.
4. Finally, when the last (third) column reaches breakthrough, the test is concluded.
5. Upon completion of above procedure, the columns are used with fresh GAC, and the
experiment is repeated at different flow rate.
6. Note down C0, Ce and V
, time and depth.
7. Plot the data (Time versus Depth) will give a straight lines for each flow rate.
8. The slop and intercept of each line are obtained, and from them the constants K, N0 and
D0 are calculated.

25. Design of Adsorption Column……
Bed – depth – service time approach (Bohart and Adam model)……
Laboratory Procedure:
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Experiment No Flow rate (m3/m2.min) Bed Depth (m) Time(h) Through Volume (m3)
1 0.081 0.61 600 1.48
1.22 1520 3.77
1.83 2450 6.07
2 0.163 1.22 430 2.13
2.44 1110 5.5
3.66 1780 8.82
3 0.326 1.52 180 1.78
3.05 530 5.25
4.57 900 8.92
4 0.652 1.52 70 1.39
4.57 430 8.52
7.62 800 15.85

26. Design of Adsorption Column……
Bed – depth – service time approach (Bohart and Adam model)……
Laboratory Procedure:
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27. Design of Adsorption Column……
Bed – depth – service time approach (Bohart and Adam model)……
Laboratory Procedure:
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Experiment
No
Flow rate
(m3/m2.min)
Bed Depth
(m)
Time(h) Through
Volume (m3)
Velocity
(m/h)
Slope Intercept
1 0.081 0.61 600 1.48 4.86 1519 350
2 0.163 1.22 430 2.13 9.78 555 250
3 0.326 1.52 180 1.78 19.56 236 180
4 0.652 1.52 70 1.39 39.12 121 120
Experiment No Flow rate
(m3/m2.min)
N0 (kg/m3) K (m3/kg.h) D0 (m)
1 0.081 185 0.363 0.23
2 0.163 135 0.508 0.45
3 0.326 115 0.706 0.76
4 0.652 118 1.06 0.99

28. Design of Adsorption Column……
Bed – depth – service time approach (Bohart and Adam model)……
Laboratory Procedure:
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29. Design of Adsorption Column……
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Empty Bet Contact Time Method
(Read from Metcalf and Eddy book)