Removal of Organics by Reactivated Carbon

摘要

Limited studies with regenerated carbons revealed that the change in adsorptive capacity of the carbons because of regeneration was insignificant. The major emphasis of the project was placed on the competitive adsorption of chloroform on granular activated carbon in the presence of humic acid. A lignite base carbon, ICI HD-4000, a product of the ICI Americas, Inc., was used for the entire study. The adsorptive capacity of the carbon for humic acid was quite low, only 0.68 mg TOC/g of carbon at a liquid phase concentration of 1 mg TOC/l. The humic acid molecule suffers from steric hindrance within the micropores of HD-4000, 50% of which with radii 100 A or larger while that of humic acid molecule is 50-80A. This results in slow kinetics of adsorption. The mass transfer for humic acid is controlled primarily by film transfer. The adsorption of chloroform was one order of magnitude greater than that of humic acid, but still quite low; 5 mg CHCl3/g was adsorbed at a solute concentration of 300 microgram/l. The film diffusion coefficient for chloroform was 1.25 x .00125 cm/sec, two orders of magnitude greater than that of humic acid. The overall mass transfer of chloroform seems to be controlled by intraparticle diffusion. From equilibrium tests in slurry reactor and continuous column studies, no competition between humic acid and chloroform was apparent. However, conceivably, in tall columns or where carbon is presaturated with humic acid, some competition may be observed.