Surface Chemistry · Question 2

Adsorption of phenol from its aqueous solution on to fly ash obeys Freundlich isotherm. At a given temperature, from 10 mg g-1 and 16 mg g-1 aqueous phenol solutions, the concentrations of adsorbed phenol are measured to be 4 mg g-1 and 10 mg g-1, respectively. At this temperature, the concentration (in mg g-1) of adsorbed phenol from 20 mg g-1 aqueous solution of phenol will be . Use: 10 2 = 0.3

Answer

15.5 to 16.5

Solution

Freundlich isotherm: xm = kC1/n

104 = ( 1610 )1/n ⇒ 2.5 = 1n 1.6

2.5 = 1 - 2(0.3) = 0.4; 1.6 = 4(0.3) - 1 = 0.2 ⇒ 1n = 2

k = 4102 = 0.04

At C = 20: xm = 0.04 202 = 16 mg g-1

Answer: 16