TITLE:
Kinetic, Isotherm and Thermodynamic Studies of the Adsorption of Thymol Blue onto Powdered Activated Carbons from Garcinia cola Nut Shells Impregnated with H3PO4 and KOH: Non-Linear Regression Analysis
AUTHORS:
Idris-Hermann Tiotsop Kuete, Donald Raoul Tchuifon Tchuifon, George Nche Ndifor-Angwafor, Arnaud Tamo Kamdem, Solomon Gabche Anagho
KEYWORDS:
Garcinia Cola Nut Shell, Chemical Activation, Elemental Analysis, Non-Linear Regression, Adsorption Isotherms, Adsorption Kinetic Models
JOURNAL NAME:
Journal of Encapsulation and Adsorption Sciences,
Vol.10 No.1,
March
31,
2020
ABSTRACT: In this
work, activated carbons (ACs) prepared by chemical activation of garcinia cola
nut shell impregnated with H3PO4 (CBH2/1) and KOH (CBK1/1) were used to study
the kinetics, equilibrium and thermodynamics of the adsorption of thymol blue
from aqueous solution. The characterization of ACs showed the BET measurements
gave surface area and total pore volume respectively of 328.407 m2·g-1 and
0.1032 cm3·g-1 for CBH2/1 and 25.962 m2·g-1 and 0.03 cm3·g-1for CBK1/1;
elemental analysis showed a high percentage of carbon in both ACs. Influence of
parameters such as initial pH, contact time, adsorbent mass, initial
concentration, ionic strength and the effect of temperature on the removal of
thymol blue from aqueous solution were studied in batch mode. The studies
showed that equilibrium adsorption was attained after 60 minutes for the two
ACs, adsorption capacity increased with increasing concentration of thymol
blue, and maximum adsorption capacity was obtained at an acidic environment
with pH 2. Avrami’s non-linear kinetic expression was the best suited for
describing the adsorption kinetics of thymol blue onto ACs, while equilibrium
data showed that the three-parameter isotherms better described the adsorption
process since R2 > 0.96, and the error functions were lowest for all of
them. Maximum adsorption capacity values obtained using the three-parameter
Fritz-Schlunder equation were 32.147 mg·g-1 for CBH2/1 and 67.494 mg·g-1 for
CBK1/1. The values of the model parameters g and mFS respectively, obtained using
the Redlich-Peterson and Fritz-Schlunder III isotherms below 1, showed that the
adsorption of thymol blue by the ACs occurred on heterogeneous surfaces.
Thermodynamic analyses of the data of the adsorption of thymol blue onto ACs
revealed that the adsorption process was temperature dependent, endothermic and
spontaneous.