| In this research, laboratory studies demonstrated that some anions greatly competed with perchlorate for adsorption sites, thus reducing the capacity of surfactant tailored granular activated carbon (GAC) to remove perchlorate.;It was observed that thiosulfate, an oxyanion and intermediate-valence sulfur species, competed with perchlorate for adsorption sites onto granular activated carbons that were tailored with quaternary ammonium surfactant. A reduced capacity of 50% of the surfactant tailored GAC was observed when Rapid Small Scale Column Tests (RSSCT) were employed. Rapid Small Scale Column Tests that employed Redlands, CA groundwater, with perchlorate of 30 microg/L, showed that 33,000 bed volumes of groundwater was processed through Arquad 2C-75 tailored GAC, before perchlorate was observed in the effluent at 6 microg/L. When the same water had 1000 microg/L of thiosulfate, 17,000 BV of Redlands, groundwater was processed through the surfactant tailored carbon before perchlorate was observed at 6 microg/L. It was determined that an implementation of a pretreatment step that utilized 2,500 microg/L of chlorine, diminished the effects of thiosulfate, by oxidizing the thiosulfate anion to sulfate and thus, returned the surfactant tailored GAC capacity to 90% of its capability. With this pre-treatment method, the surfactant tailored GAC technology can be a viable method in the removal of perchlorate from groundwater, in the presence of intermediate-valence sulfur species.;Nitrate, another oxyanion that is common in ground waters, was also observed to strongly compete with perchlorate for adsorption sites on activated carbon loaded with quaternary ammonium surfactant. It was observed that at 3 times the concentration of the initial nitrate of 30 mg/L in Fontana, CA groundwater, the surfactant tailored GAC capacity to adsorbed perchlorate was reduced to 46%. Additional experiments demonstrated that surfactant tailored GAC works best at removing perchlorate from aqueous systems at low nitrate concentrations.;This research also evaluated the scaling technology that employed the RSSCT scaling equations for proportional diffusivity. The proportional diffusivity model was designed to predict the performance of pilot and field scale experiments by utilizing smaller fixed bed columns over a shorter test period. The proportional diffusivity model used an intra-particle coefficient of 1. A comparison of pilot scale tests and RSSCT indicated that the RSSCT design that employed the proportional diffusivity model, and used surfactant tailored GAC, over predicted the removal of perchlorate, by a ratio of 0.58. This result differs from activated carbon that was not tailored with surfactants, in that proportional diffusivity accurately predicts the performance of pilot scale tests. These results suggest that intra-particle diffusivity does not linearly correlates to particle radius when activated carbon was tailored with surfactants, as was demonstrated with non tailored activated carbon. An intra-particle diffusivity coefficient that is 0.5 less than the coefficient used for proportional diffusivity scale was evaluated. Results showed that RSSCT that used a diffusivity coefficient of 0.5 under predicted the model for the pilot scale system and gave a ratio of 0.38. |
