Adsorption of acetic acid on charcoal and the isotherm

Adsorption of acetic acid on charcoal and validity of Freundlich’s adsorption isotherm and Langmuir’s adsorption isotherm

Adsorption of acetic acid on charcoal is the topic of discus for to day. Adhesion of atoms, ions, bimolecules or molecules of gas, liquid or dissolved solids to a surface is called adsorption.

The amount adsorbed by any adsorbent is dependent on pressure and temperature. Thus the amount (X) adsorbed is a function of pressure (P)and temperature (T), i.e.

X= f(P,T)

A plot of P vs X, keeping temperature constant is known as adsorption isotherm.

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Freundlich’s adsorption isotherm:

Freundlich’s adsorption isotherm; represented by –

X/m = kc^1/n

where, m= the amount of adsorbing material C is the equilibrium constant of adsorbate in the solution k is the constant depending on the nature of both adsorbate and adsorbant n is another constant depending on the nature of both adsorbate.

The value of 1/n is less than unity. On taking logarithm of the equation,

log (x/m)= log k + 1/n log c —————————— (2)

If a plot of log (x/m) vs log c gives a straight line with a slope of 1/n and intercept of log k, Freundlich’s adsorption isotherm is valid

Liquid-liquid miscibility of three liquid system and one tie line

Langmuir’s adsorption isotherm:

According to Langmuir for a uni-molecular layer, the following relation holds for adsorption,

x/m = k₁k₂c/(1+k₁c)

where, k₁ and k₂ are the constant.

The above equation can be written as-

c/(x/m) = 1/ k₁k₂ + c/k₂

Thus a plot of c/(x/m) vs c gives a straight line with a slope of 1/k₂ and a intercept of 1/ k₁k₂ and shows the validity of Langmuir adsorption isotherm

Apparatus and chemicals:

Burette, pipette, Activated charcoal, 0.5N acetic acid, 0.1N NaOH, Stopped bottles, Shaking machine etc.

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Procedure:

Prepare 0.5N acetic acid and 0.1N NaOH solution.
Take 6 clean and dry stopped bottle and prepare following solutions in the table-

Bottle No	0.5N Acetic acid(mL)	Distilled watter (mL)	Amount of charcoal (g)
01.	50	0	1
02.	40	10	1
03.	30	20	1
04.	25	25	1
05.	20	30	1
06.	10	40	1

Spotted each bottle and shake for at least 1 hour.
Filter the solution through a filter paper and collect the filtrate in numbered bottle. reject first 5 mL of each filtrate.
Pipette out 10 mL of each filtrate and titrate with 0.1N NaOH solution.
Note Down the the temperature of the solution.