Environmental Engineering Reference
Adsorption Isotherm and Adsorption Capacities
ApplicationoftheempiricalFreundlichisotherm(Freundlich 1906 ) (Eq. 5 ) and its
linearized form (Eq. 6 ), given by
showed that the plots of log q e vs. log C e were linear ( r from+0.96to+0.98forluoride
and + 0.95 to + 1.00 for arsenite). The values of the adsorption coefficient ' n ' obtained
n < 1 for both the cases and indicates favourable adsorption on the adsorbents.
The values of the Freundlich adsorption capacity, K f , on untreated and acid
treated bamboo dust are in the order of B1 (0.39 mg 1-1/n L 1/n g −1 ) < B2 (1.56 mg 1-1/n
L 1/n g −1 )<B4(2.26mg 1-1/n L 1/n g −1 ) < B3 (2.32 mg 1-1/n L 1/n g −1 ) for fluoride adsorption,
and B1 (0.66 ʼg 1-1/n L 1/n g −1 ) < B3 (3.13 ʼg 1-1/n L 1/n g −1 ) < B2 (3.23 ʼg 1-1/n L 1/n g −1 )<B4
(9.09 ʼg 1-1/n L 1/n g −1 ) for arsenite adsorption.
Langmuir adsorption isotherm models the monolayer coverage of the sorption
surfaces and assumes that sorption take places on a structurally homogeneous sur-
face of the adsorbent. This isotherm (Langmuir 1916 ) is given by the equation:
) + (
The Langmuir plots of C e / q e vs. C e are also linear ( r from + 0.99 to + 1.00 in fluo-
ride adsorption and+0.98 to+1.00 in arsenite adsorption). Langmuir equilibrium
coefficient, b ,hasvaluesof0.04-0.11Lg −1 for fluoride and 0.005-0.070 L g −1 for
arsenite adsorption. Langmuir monolayer adsorption capacity, q m , has the values
8.70mgg −1 (B1),17.24mgg −1 (B2),20.41mgg −1 (B3)and20.41mgg −1 (B4)for
luoride adsorption and 111.23 ʼg g −1 (B1),112.74 ʼg g −1 (B2), 123.00 ʼg g −1 (B3)
and 123.92 ʼg g −1 (B4)forarseniteadsorption.
adsorbent materials as it has been found that q m values increase on acid activation.
The amount adsorbed per unit mass of the adsorbent also increases on acid activa-
tion.Acid activation increases the adsorption capacity compared to the untreated
bamboo dust, which is due to the increase in surface area and anion exchange