# Department of Civil Engineering-I.I.T. Delhi CEL 795: Water and ```Department of Civil Engineering-I.I.T. Delhi
CEL 795: Water and Wastewater Treatment Processes
HW 5 Solution
Q1: For the following information, determine Langmuir and Freundlich model constants? Also
plot Q of these models with equilibrium adsorbate concentration ranging from 0 to 10 mg/L?
Compare these two models and comment on their suitability in describing the observation?
[20 points]
Solution:
See class example; See which model describe the data well in graph paper.
Q2: For the following information, determine Langmuir model constants and adsorption
capacity of alumina for initial anthracene concentration equal to 0.000811 moles/L? Also plot Q
vs. C (t) for C (t): 0 to 10 moles/L and comment on it.
Solution:
Q=Qmax*KC/[1+KC]
so Qmax*K=22; K=375 L/mol; Qmax=22/375 (mol/kg)
C=0.000822 mol/L; Ceff=?
Q=[C0-Ceff]*V/[XV]
say 1 kg alumina was used in 1 liter sample.
Q=[C0-Ceff] (mol/kg) = 22Ceff/[1+375Ceff]
solve for Ceff; calculate % removal now;
adsorption capacity of alumina = Q=[C0-Ceff]*V/[XV]= [C0-Ceff] (mol/kg)
Q3. What is the difference between Langmuir and Freundlich adsorption isotherm
mechanisms?
Solution:
See lecture notes
Q4. Untreated drinking water has 0.02 mg/L of geosmin, which gives earthy odor. How much
removal can be achieved by adding 10 mg/L powdered activated carbon (PAC) in water?
Qeq = Kf (Ceq)1/n where Qeq is mass of geosmin adsorbed on PAC (&micro;g) per mg of PAC; Ceq is
concentraton of dissolved geosmin in water (&micro;g/L), and Kf= 0.5 (&micro;g/mg)(L/ &micro;g)(1/n) and
(1/n)=1.08.
Solution:
See approach used in Q2; here X=10 mg/L is given; reactor volume =1 liter;
C0=0.02 mg/L
Ceff=?
determine Ceff and then calculate % removal
Q5. How does adsorption happen? Differentiate between competitive and cooperation
Solution:
See lecture notes; in competitive adsorption-two ions compete for same adsorption sites and one ion
might not get completely adsorbed on sites (ex: reduction in adsorption of arsenate ions due to
sulphate ions on iron oxide sites);
(ex: Calcium ions increase adsorption of arsenate ions on iron oxide sites)
Q6. What is the difference between Langmuir and Freundlich adsorption isotherm mechanisms? What