Study of Adsorption and Electrosorption with Surface-Modified Granule Activated Carbons for Dilute Perchlorate Solution
Date Issued
2011
Date
2011
Author(s)
Chen, Shih-Kai
Abstract
The activated carbon was used as adsorbent to remove perchlorate anions from the solution in this study. In order to increase the efficiency of adsorption and adsorbed amount, the surface modification of activated carbon and electrosorption process were used. The characteristics of perchlorate adsorption by activated carbon had been investigated by proposed adsorption model.
The SEM images showed that the CTAC molecules were deposited on the surface and the shape was cotton-like. The surface of E-Ni activated carbons was covered densely and the particle size were about 15-20 nm. The point of zero charge were investigated that 4.38 for granular activated carbon, 5.30 for CAC-preloaded activated carbon and 5.97 for E-Ni activated carbons.
The Langmuir isotherm model was used for the equilibrium relation between the activated carbon and perchlorate anions. The saturated adsorbed amount of perchlorate was 17.87 mg/g-GAC which anion in the solution was perchlorate only. When 0.1 M of sulfate anions were in the solution, the equilibrium adsorbed weight was decreased to 10.09 mg/g-GAC because of competing adsorption. The saturated adsorbed amount of GAC/CTAC increased to 31.34 mg/g-GAC/CTAC. The heat of adsorption for perchlorate was estimated to be -27.57 kJ/mol and was classified as physical adsorption.
In order to understand the kinetic adsorption phenomena, the pseudo-first-order kinetics adsorption model was used to characterize the circulating adsorption operations. Lower pH value induced a higher zeta potential of activated carbons and the adsorbed weight of activated carbons was increased from 5.616 mg/g-GAC to 6.246 mg/g-GAC. With the presence of 0.1 M sulfate anions, theadsorbed amount was decreased. The applied positive potential on the activated carbons could increase the adsorbed weight and kinetic adsorption rate constant effectively because the electrostatic attraction increase the moves of anions to surface. The study showed that low common anion concentration, higher zeta potential and positive electric potential applied could improve the adsorbed amount and decrease the adsorption time.
Subjects
Activated carbon adsorption
Perchlorate
Electrosorption
Type
thesis
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