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The objective of this research was to assess the competitive adsorption mechanism between atrazine and three dyes of increasing molecular size, and to eliminate the difficulties encountered when using natural organic matter. Phenolic resin-based activated carbon filters (ACFs) received as twilled weave fabrics were used in adsorption experiments. These were designated ACF-10, ACF-20 and ACF-25 in order of increasing activation and pore size heterogeneity. The ACFs were cut into small pieces, dried at 105C, and stored in a dessicator to minimize moisture contact and possible oxidation. The target micropollutant chosen for this study was the pesticide, atrazine. To facilitate rapid and accurate analysis of low atrazine concentrations, C-labelled atrazine was used. Samples were prepared by mixing 2.5 mL aliquots of 0.22 um filtered sample with 18 mL of scintillation cocktail and analyzing the resultant fluorescence with a scintillation counter. The specific activity of C-atrazine batches varied from 56.3 uCi/mg to 38.7 uCi/mg. Based on this, the limit of detection for 95 percent confidence varied between 0.05-0.10 ug/L. Three dyes of increasing molecular size were used as competing adsorbates: Methylene Blue (MB), Malachite Green (MG) and Congo Red (CR). Dye concentrations were quantified by visible spectrophotometry at wavelengths 661nm, 617nm and 497nm for MB, MG and CR, respectively. The limit of detection was approximately 0.1 uM. The adsorption study consisted of the following 7 day isotherm tests: single solute adsorption of atrazine and each of the dyes in deionized-distilled water (DDW), simultaneous adsorption of atrazine with each dye, dye preloading followed by atrazine adsorption, and atrazine preloading followed by dye contact.

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Published: 01/01/1999 ISBN(s): 1583210016 Number of Pages: 8File Size: 1 file , 190 KB