dc.description.abstract |
In the present study, calcined and acid activated adsorbents were prepared from
Ethiopian kaolinite clay.The adsorbent preparations were conducted by thermal and
chemical(phosphoric acid) activation processes. The prepared adsorbents and raw
kaolinite clay were analyzed for morphological and chemical characterization using
XRF, FTIR, XRD and SEMinstrumental techniques. From the oxide composition analysis,
the ratio of SiO2/Al2O3was 4.08 foracid activated kaolinwhich is higher than the expected
pure kaolinite standard which allows us to classify the kaolin clay as a zeolite material.
The batch adsorption process, basic operation parameter (such as initial concentrations
of dye, temperature, contact time, and pH of the solution) were examined.It was found
that a maximummethylene blue dyeremoval efficiency of 90.04% and 93.6% were
achieved for calcined and acid activated kaolin adsorbent respectively at; initial
concentration of 20 mg/L, temperature of 30℃, contact time of 60 min, solution pH of 9
and adsorbent dose 1g/100ml.Furthermore, the adsorption kinetic models, the adsorption
isotherm models and the thermodynamic parameters were determined for the batch
adsorption experiments.The calculatedΔG
o
for acid activated and calcined kaolin
adsorbent were recorded as -0.958, 1.029 and 2.767kJ/mol and 0.244, 2.019, and 3.158
at 30
o
C, 50
o
C, and 70
o
C, respectivelyfor 20 mg/L of dye concentration and solution pH of
9.This suggests that, the thermodynamic behavior at lowest temperature is more feasible
and spontaneous as compared with the higher temperature. In addition, the ∆Hᵒ and ∆Sᵒ
value is recorded a negative value suggest that, the adsorption is exothermic.Moreover
the equilibrium data was fittedwith the Freundlich and Langmuir isotherm models,and
found that Langmuir model fitted very well for both adsorbents. Finally, the rate of the
adsorption process was investigated using Pseudo first order and Pseudo second order
kinetic models, and found to be well fitted with Pseudo first order for calcined kaolin
adsorbentand Pseudo second order kinetic models for acid activated kaolin adsorbent.
From these results it can be conclude thatacid activated kaolin adsorbent has a high
capacity for the removal of dyes in industrial wastewater.
Keywords:Kaolin, Acid activation, adsorption,methylene blue dye |
en_US |