ENVR 133 |
| Removal of selenite from the aqueous phase using iron containing granular activated carbons (GAC) was investigated in this study. GAC was used primarily as a supporting medium and treated with ferric iron by oxidizing ferrous chloride with sodium hypochlorite (NaClO). Nitrogen adsorption-desorption analyses indicated that Brunauer-Emmett-Teller (BET) surface area, pore size and pore volume deceased with iron impregnation. Scanning electron microscope (SEM) analyses confirmed the changes in porosity and pore size of GAC after iron impregnation. Energy dispersive spectrometer (EDS) analysis showed that iron content increased after iron impregnation. Five different types of GAC were tested for iron impregnation and selenite removal. Darco GAC 12°Á20 was shown to be the most effective adsorbent among the adsorbents examined after iron impregnation. The result also indicated that GAC coated with 0.1 M iron achieved the highest selenite removal (97.3%). The removal of selenite occurred in a wide range of pH examined (i.e., 2 to 11), but efficiency decreased when pH was higher than 8.0. Adsorption kinetics showed that selenite removal efficiency reached more than 90% after 6 hours adsorption for and initial concentration of 2 mg/L and equilibrium was obtained after 48 hours. A pseudo-second-order kinetic model was found to characterize the adsorption kinetics well (R2 = 0.9991). Adsorption isotherms for two different selenite concentrations (1 mg/L and 2 mg/L) were developed and the data generally fit the Freundlich model well (R2 =0.9872). The adsorption capacity reached as high as 1.68 mg-Se/g-adsorbent at equilibrium for initial concentration of 2 mg/L. The study results suggest that the GAC-based iron-containing adsorbents can be used for efficient selenite removal from aqueous streams. |
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General Papers
6:00 PM-8:00 PM, Wednesday, August 22, 2007 BCEC -- Exhibit Hall - B2, Poster
Division of Environmental Chemistry |