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ADSORPTION IN LIQUID SYSTEMS Adsorption of solutes in liquid systems usually follow Freundlich isotherm. The correlation is given by the following equation:

Γ = aC 1 / b

(1)

Where Γ = degree of adsorption, weight of material adsorbed per unit mass of adsorbing medium (moles/mass) C = equilibrium concentration in liquid phase (molarity)

) a = empirical constant, ( moles) b ( volume b = empirical constant (dimensionless)

1− 1

1/ b

/ mass

The Freundlich isotherm may be transformed into a linear form to facilitate data analysis. 1 log Γ = log a + log C (2) b Alternatively, a Langmuir isotherm may be used. AC Γ = (3) 1 + BC where Γ = degree of adsorption C = equilibrium concentration in liquid phase A = empirical constant (volume/mass) B = empirical constant (volume/moles) Similarly, the Langmuir isotherm, may be transformed into a linear equation.

C

Γ

=

1 B + C A A

(4)

The choice of units for Γ and C is arbitrary, but the given units are suggested for convenience. Equipment and Materials Erlenmeyer flasks, funnel, burette, filter paper, thermostatic bath, acetic acid sodium hydroxide, distilled water, phenolphthalein indicator Objective: To determine an isotherm which satisfactorily describe adsorption of a given solute on activated carbon Procedure 1. Prepare 100ml portions of acetic acid solution of the following concentrations: 0.200, 0.100, 0.050, 0.025 M. Put each portion in an Erlenmeyer flask. Adsorption in Liquid Systems 24

2. Prepare a titrant of 0.25M NaOH solution. 3. Put 5g of activated carbon in each flask and immerse the flask in the thermostatic bath. Let the solutions equilibrate for about 30 minutes while shaking the contents occasionally. 4. Decant the supernatant liquid from each flask. Filter these liquids to remove the excess suspended adsorbent. Determine the concentration of acetic acid in the filtrate by titration. Analysis 1. Calculate the degree of adsorption based on the initial and final...