Matching Items (16)
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- All Subjects: public health
- Creators: School of Human Evolution & Social Change
- Creators: Chemical Engineering Program
Description
Microbial fuel cells (MFCs) promote the sustainable conversion of organic matter in black water to electrical current, enabling the production of hydrogen peroxide (H2O2) while making waste water treatment energy neutral or positive. H2O2 is useful in remote locations such as U.S. military forward operating bases (FOBs) for on-site tertiary water treatment or as a medical disinfectant, among many other uses. Various carbon-based catalysts and binders for use at the cathode of a an MFC for H2O2 production are explored using linear sweep voltammetry (LSV) and rotating ring-disk electrode (RRDE) techniques. The oxygen reduction reaction (ORR) at the cathode has slow kinetics at conditions present in the MFC, making it important to find a catalyst type and loading which promote a 2e- (rather than 4e-) reaction to maximize H2O2 formation. Using LSV methods, I compared the cathodic overpotentials associated with graphite and Vulcan carbon catalysts as well as Nafion and AS-4 binders. Vulcan carbon catalyst with Nafion binder produced the lowest overpotentials of any binder/catalyst combinations. Additionally, I determined that pH control may be required at the cathode due to large potential losses caused by hydroxide (OH-) concentration gradients. Furthermore, RRDE tests indicate that Vulcan carbon catalyst with a Nafion binder has a higher H2O2 production efficiency at lower catalyst loadings, but the trade-off is a greater potential loss due to higher activation energy. Therefore, an intermediate catalyst loading of 0.5 mg/cm2 Vulcan carbon with Nafion binder is recommended for the final MFC design. The chosen catalyst, binder, and loading will maximize H2O2 production, optimize MFC performance, and minimize the need for additional energy input into the system.
ContributorsStadie, Mikaela Johanna (Author) / Torres, Cesar (Thesis director) / Popat, Sudeep (Committee member) / Barrett, The Honors College (Contributor) / Chemical Engineering Program (Contributor)
Created2015-05
Description
Iodide-based ionic liquids have been widely employed as sources of iodide in electrolytes for applications utilizing the triiodide/iodide redox couple. While adding a low-viscosity solvent such as water to ionic liquids can greatly enhance their usefulness, mixtures of highly viscous iodide-containing ILs with water have never been studied. Thus, this paper investigates, for the first time, mixtures of water and the ionic liquid 1-butyl-3-methylimidazolium iodide ([BMIM][I]) through a combined experimental and molecular dynamics study. The density, melting point, viscosity and conductivity of these mixtures were measured experimentally. The composition region below 50% water by mole was found to be dramatically different from the region above 50% water, with trends in density and melting point differing before and after that point. Water was found to have a profound effect on viscosity and conductivity of the IL, and the effect of hydrogen bonding was discussed. Molecular dynamics simulations representing the same mixture compositions were performed. Molecular ordering was observed, as were changes in this ordering corresponding to water content. Molecular ordering was related to the experimentally measured mixture properties, providing a possible explanation for the two distinct composition regions identified by experiment.
ContributorsNgan, Miranda L (Author) / Dai, Lenore (Thesis director) / Nofen, Elizabeth (Committee member) / Barrett, The Honors College (Contributor) / Chemical Engineering Program (Contributor)
Created2015-05
Description
Growing hotspots of unvaccinated children corroborate with states that have highly permissive vaccination policies. State-based nonmedical exemption (NME) policies such as religious or philosophical exemptions make it easy for parents to opt out of vaccinating their children thus lowering herd immunity and increasing the risk of outbreaks. Recent studies have revealed that Phoenix is the metropolitan area with the highest number of nonmedical exemptions in the country with vaccination rates below herd immunity. This thesis investigates the role of the law in enabling low vaccination rates and develops a set of policy recommendations that lawmakers may use as a tool to restore these rates to herd immunity levels. To do this, an in-depth literature review was performed and supplemented with a case study of California’s policy response to the 2014 Disneyland measles outbreak. This information was synthesized into an in-depth policy analysis addressing the political, social, practical, and economic factors of the issue and four potential policy responses for state lawmakers. Based on the analysis and California’s example, eliminating nonmedical vaccine exemptions was identified as the most effective policy option to reach the intended goal of restoring vaccination rates to herd immunity levels. This policy option is both the most cost-effective and productive in reaching herd immunity but infringes the most on parental rights and will be met with the most significant political pushback. Despite these challenges, lawmakers should take this policy step to protect our community and the most vulnerable among us.
ContributorsSaxon, Mary Elizabeth (Author) / Reddy, Swapna (Thesis director) / Speer, Matthew (Committee member) / School of Human Evolution & Social Change (Contributor) / Barrett, The Honors College (Contributor)
Created2019-05
Description
Nitrate (NO3- ) and selenate (SeO42-) are common contaminants found in mining wastewater. Biological treatment has proved successful using bacteria capable of respiring NO3- into nitrogen gas and SeO42- into Se°. The Membrane Biofilm Reactor (MBfR) utilizes biofilm communities on the surface of hollow-fiber membranes to transform oxidized water contaminants into innocuous reduced products. For this project, I set up two MBfRs in a lead and lag configuration to reduce NO3- [input at ~40-45 mg NO3-N/L] and SeO42- [0.62 mg/L], while avoiding sulfate (SO42-) [~1600-1660 mg/L] reduction. Over the course of three experimental phases, I controlled two operating conditions: the applied hydrogen pressure and the total electron acceptor loading. NO3- in the lead MBfR showed average reductions of 50%, 94%, and 91% for phases I, II, and III, respectively. In the lag MBfR, NO3- was reduced by 40%, 96%, and 100% for phases I, II, and III. NO2- was formed in Stage I when NO3- was not reduced completely; nevertheless NO2- accumulation was absent for the remainder of operation. In the lead MBfR, SeO42- was reduced by 65%, 87%, and 50% for phases I, II, and III. In the lag MBfR, SeO42- was reduced 60%, 27%, and 23% for phases I, II, and III. SO42- was not reduced in either MBfR. Biofilm communities were composed of denitrifying bacteria Rhodocyclales and Burkholderiales, Dechloromonas along with the well-known SeO42--reducing Thauera were abundant genera in the biofilm communities. Although SO42- reduction was suppressed, sulfate-reducing bacteria were present in the biofilm. To optimize competition for electron donor and space in the biofilm, optimal operational conditions were hydrogen pressures of 26 and 7 psig and total electron acceptor loading of 3.8 and 3.4 g H2/m2 day for the lead and lag MBfR, respectively.
ContributorsMehta, Sanya Vipul (Author) / Rittmann, Bruce (Thesis director) / Ontiveros-Valencia, Aura (Committee member) / Chemical Engineering Program (Contributor) / School of International Letters and Cultures (Contributor) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
Microbial fuel cells (MFCs) facilitate the conversion of organic matter to electrical current to make the total energy in black water treatment neutral or positive and produce hydrogen peroxide to assist the reuse of gray water. This research focuses on wastewater treatment at the U.S. military forward operating bases (FOBs). FOBs experience significant challenges with their wastewater treatment due to their isolation and dangers in transporting waste water and fresh water to and from the bases. Even though it is theoretically favorable to produce power in a MFC while treating black water, producing H2O2 is more useful and practical because it is a powerful cleaning agent that can reduce odor, disinfect, and aid in the treatment of gray water. Various acid forms of buffers were tested in the anode and cathode chamber to determine if the pH would lower in the cathode chamber while maintaining H2O2 efficiency, as well as to determine ion diffusion from the anode to the cathode via the membrane. For the catholyte experiments, phosphate and bicarbonate were tested as buffers while sodium chloride was the control. These experiments determined that the two buffers did not lower the pH. It was seen that the phosphate buffer reduced the H2O2 efficiency significantly while still staying at a high pH, while the bicarbonate buffer had the same efficiency as the NaCl control. For the anolyte experiments, it was shown that there was no diffusion of the buffers or MFC media across the membrane that would cause a decrease in the H2O2 production efficiency.
ContributorsThompson, Julia (Author) / Torres, Cesar (Thesis director) / Popat, Sudeep (Committee member) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
This study examines associations between clean water, sanitation, mosquito net usage, and immune biomarkers among the Tsimane, a remote subsistence population of forager-horticulturalists with a high pathogen load. Interviews with heads of household (n=710, aged 18-92, median age 40 years) were conducted to ascertain household water sources, ownership and usage of mosquito nets, and latrine use. In this sample, 21% of households used latrines, 20% always boiled their water, and 85% used mosquito nets. Regression models estimate their associations biomarkers of pathogen exposure, including white blood cell count (WBC), hemoglobin (Hb), eosinophils, and sedimentation rate (ESR). Controlling for age, sex, and distance from the closest market town, latrine use (Std. β = -0.11, p= 0.017) and boiling water (Std. β = -0.08, p= 0.059) are associated with lower WBCs. Latrine use is marginally associated with higher hemoglobin (Std. β = 0.09, p= 0.048), but not boiling water (p= 0.447). ESR trends toward lower levels for households that always boil water (Std. β= -0.09, p= 0.131), but is not associated with latrine use (p=0.803). Latrine use was significantly associated with lower eosinophil counts (Std. β= -0.14, p=0.013), but not boiling water (p=0.240). Mosquito nets are not associated with any of these biomarkers. Both boiling water and latrine use are associated with better health outcomes in this sample. These results suggest that scarce public health resources in rural subsistence populations without malarial risk may wish to prioritize boiling water and latrine use to improve health outcomes.
ContributorsDinkel, Katelyn Aubree (Author) / Trumble, Benjamin (Thesis director) / Costa, Megan (Committee member) / Jehn, Megan (Committee member) / School of Mathematical and Statistical Sciences (Contributor) / School of Human Evolution & Social Change (Contributor) / School of Life Sciences (Contributor) / School of International Letters and Cultures (Contributor) / Barrett, The Honors College (Contributor)
Created2019-05
Description
Alternative ion exchange membranes for implementation in a peroxide production microbial electrochemical cel (PP-MEC) are explored through membrane stability tests with NaCl electrolyte and stabilizer EDTA at varying operational pHs. PP-MEC performance parameters \u2014 H2O2 concentration, current density, coulombic efficiency and power input required \u2014 are optimized over a 7 month continuous operation period based on their response to changes in HRT, EDTA concentration, air flow rate and electrolyte. I found that EDTA was compatible for use with the membranes. I also determined that AMI membranes were preferable to CMI and FAA because it was consistently stable and maintained its structural integrity. Still, I suggest testing more membranes because the AMI degraded in continuous operation. The PP-MEC produced up to 0.38 wt% H2O2, enough to perform water treatment through the Fenton process and significantly greater than the 0.13 wt% batch PP-MEC tests by previous researchers. It ran at > 0.20 W-hr/g H2O2 power input, ~ three orders of magnitude less than what is required for the anthraquinone process. I recommend high HRT and EDTA concentration while running the PP- MEC to increase H2O2 concentration, but low HRT and low EDTA concentration to decrease power input required. I recommend NaCl electrolyte but suggest testing new electrolytes that may control pH without degrading H2O2. I determined that air flow rate has no effect on PP-MEC operation. These recommendations should optimize PP-MEC operation based on its application.
ContributorsChowdhury, Nadratun Naeem (Author) / Torres, Cesar (Thesis director) / Popat, Sudeep (Committee member) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
During the COVID-19 pandemic, increased burdens have been placed on the Arizona healthcare system, and its healthcare providers. Using a survey with a sample of N=308 prescribing providers and nurses in the Arizona healthcare system, the impact of COVID-19 on the wellbeing of healthcare providers was assessed. The survey used measures to evaluate for physical and emotional wellbeing, burnout, stressors associated with COVID-19, and work-life experiences, and found an overall negative impact on the wellbeing of healthcare workers during the COVID-19 pandemic with increased levels of reported stress and tiredness, concern for the health of family and loved ones, concern for the hardships of patients, lack of alignment between organizational priorities and personal values, and low levels of support and appreciation from socially and from leadership at work.
ContributorsJohnson, Emma Carina (Author) / Schuster, Roseanne (Thesis director) / Michalec, Barret (Committee member) / School of Molecular Sciences (Contributor) / School of Human Evolution & Social Change (Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
Description
The ongoing Global Coronavirus Pandemic has been upheving social norms for over a year at this point. For countless people, our lives look very different at this point in time than they did before the pandemic began. Quarantine, Shelter in Place, Work from Home, and Online classes have led global populations to become less active leading to an increase in sedentary lifestyles. The final impact of this consequence is unknown, but emerging studies have led to concrete evidence of decreased physical and mental wellbeing, particularly in children. VirusFreeSports was the brainchild of three ASU Honors students who sought to remedy these devastating consequences by creating environments where children can participate in sports and exercise safely, free of the threat COVID-19 or other transmissible illnesses. The ultimate goal for the project team was to build traction for their idea, which culminated in a video pitch sent to potential investors. Although largely created as an exercise and we did not create a full certification course, merely a prototype through a website with sample questions to gauge interest, the project was a success as a large target market for this product was identified that showed great promise. Our team believes that early entrance to the market, as well as the lack of any other competitors would give the team a tremendous advantage in creating an impactful and influential service.
ContributorsVrbanac, Matthew Thomas (Co-author) / Tanveer, Samad (Co-author) / Israel, Natasha (Co-author) / Byrne, Jared (Thesis director) / Lee, Chris (Committee member) / Kunowski, Jeff (Committee member) / Chemical Engineering Program (Contributor, Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
Description
This study compares vaccine hesitancy during the COVID-19 pandemic with previous studies on vaccine hesitancy to evaluate the major driving factors behind COVID-19 vaccine hesitancy among undergraduate students at Arizona State University (ASU). Undergraduate students were surveyed with questions regarding different aspects of vaccines, including personal vaccination history, opinions on the COVID-19 vaccine, knowledge of the COVID-19 vaccine, and reasoning behind vaccination status. The survey was distributed through school listservs within ASU. Close-ended questions underwent statistical analysis on IBM SPSS and open-ended questions were analyzed using content analysis. Results indicated that the main driving factors behind vaccine hesitancy are believing in natural immunity, familial influence, lack of trust behind the technology of the COVID-19 vaccine, and preferring the risk of COVID-19 infection over the risk of COVID-19 vaccination. The main driving factors behind vaccine hesitancy appear to be similar to driving factors in the past, with an increase of mistrust surrounding the vaccine.
ContributorsD'Agostino, Annabelle (Author) / Stotts, Rhian (Thesis director) / Marsteller, Sara (Committee member) / Barrett, The Honors College (Contributor) / School of Life Sciences (Contributor) / School of Human Evolution & Social Change (Contributor)
Created2023-05