Adsorption is a reversible process which is shown by solids like activated charcoal, zeolite, silica clay, alumina etc.The solute present in the feed continuously interacts with the absorbent and gets adsorbed

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2. ADSORPTION
 Adsorption is a reversible process which is shown by
solids like activated charcoal, zeolite, silica clay, alumina
etc.
The end product which is separated is called the
absorbate.
The material used for purification is called adsorbent.
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3. ADVANTAGES
 It occurs very fast.
 It does not cause denaturation of bio molecules.
 It is an economic process.
 It is highly specific process.
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ADSORPTION ISOTHERM
 It indicates the graphical representation of the adsoption
equilibria.
 It is obtained by plotting the concentration of solute to be
adsorbed in the adsorbent against the concentration of the
solute present in the liquid phase.
 It can be of three types:
1. Linear Isotherm
2. Langmuir Isotherm
3. Freudlich Isotherm

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LINEAR ISOTHERM
Cα
[S]
K Cα= KS
Where,
Cα = concentration of product in the
solid phase.
S = concentration of solute in the
liquid phase.
LANGMUIR ISOTHERM
1/
Cα
1/ Co
1/ [S]
Slope= k/Co
Cα= Co S/K+S
80%-90% of proteins show
langmuir isotherm

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FREUDLICH ISOTHERM
Cα
[S]
Cα= K Sn
All types of antibiotics, varieties of bio
molecules show freudlich isotherm.
The value of
N>1 = detoriates adsorption process
N<1 = promotes adsorption process

7. CONTINUOUS ADSOPTION PROCESS
 CSTR is used for continuous adsorption process.
 The solute present in the feed continuously interacts with
the absorbent and gets adsorbed.
 In continuous process steady state conditions are not
achieved.
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8. AGITATOR
FSi
FS
The Change in accumulation of adsorbate per unit time in the
given vessel can be calculated
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 Total accumulation of the solute in the reactor = initial
concentration in feed – final solute concentration in the exit feed
– solute adsorbed by the adsorbent.
 Which is given by the mass balance equation:
and (1-ε) V dCα/dr = Vr --Eq. 2, {On substituting eq. 2 in eq. 1 we get}
Where, ε– void fraction
V – volume inside the vessel
r – adsorption process of adsorbate per unit volume of
feed per unit time
ΣV∫ds/dt = Fsi - Fs - (1-ε) V dCα/dr --Eq. 1

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 If diffusion is the only force for adsorption of desired solute.
r = K’A(Si-S*) -- Eq. 3
Where, r – rate of adsorption per unit volume per unit feed
K’- mass transfer coefficient
A - surface area of adsorbent
Si- initial solute conc. In the feed
S*- hypothetical conc. of solute which is in equilibrium with
the adsorbent
{Now we’ll substitute the value of eq. 3 in eq. 2}
ΣV∫ds/dt = Fsi - Fs - V K’A(Si-S*) -- Eq. 4

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 Freundlich Isotherm -- Cα= K’ S*n
Therefore, S*= (Cα/ K’) 1/n -- Eq. 5
{on substituting the value of eq. 5 in eq. 4}
ΣV∫ds/dt = Fsi - Fs - V K’A(Si- (Cα/ K’) 1/n )
This is the equation for continuous adsorption when only
diffusion is occurring.

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If diffusion along with some irreversible reaction is
occurring for adsorption of desired solute.
-- Eq. 1
r = DK”A(Si-S*) -- Eq. 3
Where, r – rate of adsorption per unit volume per unit feed
D- Diffusion coefficient
A - surface area of adsorbent
K”- Reaction constant
Si- initial solute conc. In the feed
S*- hypothetical conc. of solute which is in equilibrium
with the adsorbent.
ΣV∫ds/dt = Fsi - Fs – V √ DK”A(Si-S*)

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FIXED BED/ FLUIDIZED BED ADSOPTION
PROCESS
FSi
FS
ΣV ∫ds/dt = Fsi - Fs – [ (1-ε) V (dCα/dr) ]
Total accumulated
solute in the vessel
at time T
Flow rate of feed
entering – feed
leaving the vessel
Solute conc.
adsorbed on
adsorbent

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