Advancing the Technology Readiness of Membrane Catalyst-film Reactors for Nitrate Removal

189357-Thumbnail Image.png
Description
Due to the use of fertilizers, concentrations of harmful nitrate have increased in groundwater and surface waters globally in the last century. Water treatment plants primarily use separation techniques for nitrate treatment, but these technologies create a high nitrate concentration

Due to the use of fertilizers, concentrations of harmful nitrate have increased in groundwater and surface waters globally in the last century. Water treatment plants primarily use separation techniques for nitrate treatment, but these technologies create a high nitrate concentration brine that is costly to dispose of. This dissertation focuses on catalytic hydrogenation, an emerging technology capable of reducing nitrate to nitrogen gas using hydrogen gas (H2). This technology reduces nitrate at rates >95% and is an improvement over technologies used at water treatment plants, because the nitrate is chemically transformed with harmless byproducts and no nitrate brine. The goal of this dissertation is to upgrade the maturity of catalytic nitrate hydrogenation systems by overcoming several barriers hindering the scale-up of this technology. Objective 1 is to compare different methods of attaching the bimetallic catalyst to a hollow-fiber membrane surface to find a method that results in 1) minimized catalyst loss, and 2) repeatable nitrate removal over several cycles. Results showed that the In-Situ MCfR-H2 deposition was successful in reducing nitrate at a rate of 1.1 min-1gPd-1 and lost less than 0.05% of attached Pd and In cumulatively over three nitrate treatment cycles. Objective 2 is to synthesize catalyst-films with varied In3+ precursor decorated over a Pd0 surface to show the technology can 1) reliably synthesize In-Pd catalyst-films with varied bimetallic ratios, and 2) optimize nitrate removal activity by varying In-Pd ratio. Results showed that nitrate removal activity was optimized with a rate constant of 0.190 mg*min-1L-1 using a catalyst-film with a 0.045 In-Pd ratio. Objective 3 is to perform nitrate reduction in a continuous flow reactor for two months to determine if nitrate removal activity can be sustained over extended operation and identify methods to overcome catalyst deactivation. Results showed that a combination of increased hydraulic residence time and reduced pH was successful in increasing the nitrate removal and decreasing harmful nitrite byproduct selectivity to 0%. These objectives increased the technology readiness of this technology by enabling the reuse of the catalyst, maximizing nitrate reduction activity, and achieving long-term nitrate removal.
Date Created
2023
Agent

Christianity and Social Justice: Resolving Internal Tension, Speaking Spiritual Truths, and Articulating an Ethic for Challenging Times

136009-Thumbnail Image.png
Description
Social and economic turmoil in the wake of the Great Recession have resurrected longstanding political and social tensions. Jumping on the bandwagon revival of "conservatism" in American politics demonstrated by sizable Republican gains in the 2010 midterm elections, conservatives in

Social and economic turmoil in the wake of the Great Recession have resurrected longstanding political and social tensions. Jumping on the bandwagon revival of "conservatism" in American politics demonstrated by sizable Republican gains in the 2010 midterm elections, conservatives in faith-based communities have revived so-called "social issues," particularly seeking to roll back LGBT and reproductive rights. I aim to underscore the internal tensions that exist between policy choices of social and fiscal conservatives. Through a critical reading of the Bible and a comparative discussion about the role of government in modern-day economies, I seek to interrogate the longsstanding assumptions that have connected Scripture, laissez-faire economics, and Republican policies. Finally, acknowledging the multiplicity of perspectives that life experience may bring, I articulate a Christian case for social justice and offer an embodied methodological praxis as a basis for further inquiry.
Date Created
2012-05
Agent