| A particularly common cause of off-flavors and odors in public water supplies is 2-methylisoborneol (MIB). This harmless organic compound is produced by microorganisms and exhibits an amazingly low odor threshold concentration of 7–15 parts per trillion. Of the few technologies that can effectively remove and/or destroy MIB, activated carbon is perhaps the most widely used. Granular and powdered activated carbons are frequently employed (with great success) to adsorb MIB from drinking waters. However, activated carbon is a costly alternative due to its limited capacity for adsorption.; The research herein was initiated to develop methods for enhancing the MIB adsorption capacity of a commercially available activated carbon. Currently, no prior research has focused on enhancing MIB uptake, although there have been numerous efforts to improve adsorption of other aqueous contaminants. For the most part, the work in this thesis focuses on the effects of heat treatments in reducing environments. Carbon samples were treated in atmospheres of nitrogen, hydrogen, methane, steam, and combinations thereof. Subsequent MIB adsorption performance was determined via mini-column tests, which mimicked full-scale filter-bed adsorbers.; It was discovered that heat treatments in nitrogen impeded MIB adsorption performance in minicolumns. As compared to untreated material, nitrogen-treated carbons processed fewer bed volumes before initial MIB breakthrough occurred. Hydrogen treatments, on the other hand, were found to significantly enhance MIB breakthrough performance. Efforts to reproduce the effects of hydrogen treatment while using steam and/or methane revealed that low-temperature (375°C) steam treatments were fairly effective (though not as effective as hydrogen) while methane treatments severely hindered MIB adsorption. Interestingly, treatments in mixtures of steam and methane were among the most effective treatments tested herein.{09}Following exposure to a mixture of steam and methane at 1000°C, an experimental carbon processed four times more water than untreated material and two times more water than hydrogen-treated material before initial MIB breakthrough occurred. Porosity and surface charge analyses indicated that MIB adsorption performance in fixed-bed adsorbers is strongly tied to internal pore volume within specific pore size ranges. Furthermore, it was discovered that acidic functional groups, especially those located on external surfaces, could cause MIB diffusion limitations that accelerate MIB breakthrough in minicolumns. This phenomenon was linked to the poor performance of nitrogen-treated carbon (see above) and also to that of carbons treated in steam at 1000°C. |
