The recent lowering of the arsenic MCL from 50 ppb to 10 ppb in 2006 will cause many utilities to implement new technologies for arsenic removal. Most of the affected utilities are expected to use adsorption onto solid sorbents for arsenic removal, especially in the arid Southwest, where conserving and re-using water is of utmost importance. This would cause the generation of more than 6 million pounds of arsenic residuals every year, which then would be disposed of in landfills. This thesis effort focuses on the testing of different aluminum and iron (hydr)-oxide based sorbents that are likely to be used for arsenic removal and assessing the behavior of these Arsenic Bearing Solid Residuals (ABSRs) under landfill conditions. It was demonstrated that the Toxicity Characteristic Leaching Procedure (TCLP) test underestimates the arsenic mobilization in landfills. Desorption of arsenic from ABSRs was quantified as a function of the range of pH and concentrations of competitive anions like phosphate, bicarbonate, sulfate and silicate and NOM found in landfills. The effect of pH is much more significant than the anions and NOM. Arsenic release due to competition of different anions is neither additive nor purely competitive. Landfill conditions were simulated inside long-term, continuous flow-through column reactors, and arsenic mobilization from sorbents was measured under those conditions. The results indicate that under reducing conditions, and in the presence of other competitive anions and high organics, microbes reduce arsenate to arsenite, which is a much more mobile species. Fe(III) is also reduced to Fe(II) under these conditions. Arsenic is transported in the particulate phase, associated with the iron, much more than in the dissolved phase. It was also observed that the sorbent itself might leach away at a faster rate than the arsenic sorbate causing a depletion of surface sites and a sudden spike in the release rate of arsenic, after a long residence time. Finally, investigation of different solid sorbents indicate, that the rate of leaching and the form of arsenic released varies widely and is independent of the respective adsorption capacities, even under similar leaching conditions.

Post-combustion carbon capture, wherein the CO2 produced as a result of coal combustion is trapped at the power plant exhaust, is seen as a bridging technology to reduce CO2 emissions and combat climate change. This capture process will however impose a parasitic load on the power plant and technologies need to be developed to minimize this energy penalty. This research focuses on a technology which uses solid sorbents fashioned into a hollow fiber form that allows water-moderated thermal cycling as a means of trapping CO2 from flue gas. While hollow fiber technology has intrinsic advantages over competing liquid amine and packed bed technologies, the materials used to fabricate hollow fibers and the fabrication process itself need to be optimized in order to result in competitive, robust hollow fiber sorbents. This dissertation focuses on the material selection process for each component of the hollow fiber platform and discusses ways to optimize the fiber and barrier layer formation. Different materials were evaluated to function as the solid sorbent, the matrix polymer and the barrier layer; and eventually their performance was measured against past work in this area.