Matching Items (9)
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- All Subjects: wastewater
- Creators: Chemical Engineering Program
- Member of: Barrett, The Honors College Thesis/Creative Project Collection
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
The primary objective of this research project is to develop dual layered polymeric microparticles with a tunable delayed release profile. Poly(L-lactic acid) (PLA) and poly(lactic-co-glycolic acid) (PLGA) phase separate in a double emulsion process due to differences in hydrophobicity, which allows for the synthesis of double-walled microparticles with a PLA shell surrounding the PLGA core. The microparticles were loaded with bovine serum albumin (BSA) and different volumes of ethanol were added to the PLA shell phase to alter the porosity and release characteristics of the BSA. Different amounts of ethanol varied the total loading percentage of the BSA, the release profile, surface morphology, size distribution, and the localization of the protein within the particles. Scanning electron microscopy images detailed the surface morphology of the different particles. Loading the particles with fluorescently tagged insulin and imaging the particles through confocal microscopy supported the localization of the protein inside the particle. The study suggest that ethanol alters the release characteristics of the loaded BSA encapsulated in the microparticles supporting the use of a polar, protic solvent as a tool for tuning the delayed release profile of biological proteins.
ContributorsFauer, Chase Alexander (Author) / Stabenfeldt, Sarah (Thesis director) / Ankeny, Casey (Committee member) / Barrett, The Honors College (Contributor) / Harrington Bioengineering Program (Contributor)
Created2015-05
Description
Imaging analysis of local drug delivery is important because in both studies involving chemotherapy targeted toward glioblastoma and antimicrobial addressing infection, the drug concentration and distribution are unknown. There are a variety of studies focused on the local delivery of drug to a targeted location, but we are presenting a way of quantifying the concentration of the drug and the distribution of the drug during a period of time. This study aims to do that by utilizing Materialise Mimics to analyze the MRI images of local drug delivery in glioblastoma in canines and antimicrobial gel in rabbit femurs. The focus of the technique is to register the anatomy in T1-weighted spin echo images to the drug delivery in T2 flow attenuated inversion recovery (FLAIR) images in order to see where the drug went and did not go relative to the anatomical part. Both studies focus on addressing effective volumes of drug to a designated anatomical area, in which the delivery can be difficult as it involves bypassing the blood brain barrier in the first study and achieving effective volumes while preventing toxicity to the kidneys in the second study. The goal of this project lies in determining the drug volumes and location for the specified duration and anatomical part.
ContributorsJehng, Hope (Author) / Caplan, Michael (Thesis director) / Sirianni, Rachael (Committee member) / Chemical Engineering Program (Contributor) / School of International Letters and Cultures (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
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
The objective of this research is to create biodegradable mats with tunable characteristics such as fiber diameter and surface area. The drug delivery mats enable spatially controlled delivery of disease-specific therapeutics. Using a large electric potential to draw fibers from a solution flowing at a specific rate, the polymer fibers reach a grounded target several inches away. The biodegradable polymer used in this study was poly(lactic acid-co-glycolic acid) (PLGA). PLGA solutions ranging from 0.5 to 27 wt.% were prepared by dissolving the block copolymer in a solvent mixture containing tetrahydrofuran (THF) and dimethylformamide (DMF) at a 3:1 weight ratio. They were then electrospun at needle-to-target distances of 7, 14, and 18 cm and rates ranging from 0.8 to 4 mL/h. The range of voltage used was between 8 – 15 kV, which was based on the observation of the formation of a Taylor cone, largely affected by on the environment and weather (e.g., temperature and humidity in the lab). A 27 wt.% PLGA solution, electrospun at 1 mL/h at a voltage of 11.25 kV and needle-to-target distance of 14 cm produced uniform fibers with an average fiber diameter of 0.985 m. All other parameters outside the range given created beaded fibers. In addition, solution rheology was performed on some of the PLGA solution to measure viscosity, which is directly correlated to the fiber diameter of the electrospun mats. Observing the impact of solvent on fiber spinning and fiber diameter brings about many positive results in developing fully characterized and well-understood fibrous mats for drug delivery. The nanoscale fibers will be used as drug delivery mats and, therefore, the biodegradation kinetics of the polymers will be studied. Next, parameters of the polymers as well as the polymeric mats will be correlated to the degradation-mediated release of small molecule therapeutics (e.g., peptides, drugs, etc.) such that time-resolved dosing profiles can be created.
ContributorsLent, Madeline (Author) / Green, Matthew (Thesis director) / Holloway, Julianne (Committee member) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2016-12
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
The goal of this research project is to create a Mathcad template file capable of statistically modelling the effects of mean and standard deviation on a microparticle batch characterized by the log normal distribution model. Such a file can be applied during manufacturing to explore tolerances and increase cost and time effectiveness. Theoretical data for the time to 60% drug release and the slope and intercept of the log-log plot were collected and subjected to statistical analysis in JMP. Since the scope of this project focuses on microparticle surface degradation drug release with no drug diffusion, the characteristic variables relating to the slope (n = diffusional release exponent) and the intercept (k = kinetic constant) do not directly apply to the distribution model within the scope of the research. However, these variables are useful for analysis when the Mathcad template is applied to other types of drug release models.
ContributorsHan, Priscilla (Author) / Vernon, Brent (Thesis director) / Nickle, Jacob (Committee member) / Harrington Bioengineering Program (Contributor, Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
Description
Current methods measuring the consumption of prescription and illicit drugs are often hampered by innate limitations, the data is slow and often restricted, which can impact the relevance and robustness of the associated data. Here, wastewater-based epidemiology (WBE) was applied as an alternative metric to measure trends in the consumption of twelve narcotics within a collegiate setting from January 2018 to May 2018 at a Southwestern U.S. university. The present follow-up study was designed to identify potential changes in the consumption patterns of prescription and illicit drugs as the academic year progressed. Samples were collected from two sites that capture nearly 100% of campus-generated wastewater. Seven consecutive 24-hour composite raw wastewater samples were collected each month (n = 68) from both locations. The study identified the average consumption of select narcotics, in units of mg/day/1000 persons in the following order: cocaine (528 ± 266), heroin (404 ± 315), methylphenidate (343 ± 396), amphetamine (308 ±105), ecstasy (MDMA; 114 ± 198), oxycodone (57 ± 28), methadone (58 ± 73), and codeine (84 ± 40). The consumption of oxycodone, methadone, heroin, and cocaine were identified as statistically lower in the Spring 2018 semester compared to the Fall 2017. Universities may need to increase drug education for the fall semester to lower the consumption of drugs in that semester. Data from this research encompasses both human health and the built environment by evaluating public health through collection of municipal wastewater, allowing public health officials rapid and robust narcotic consumption data while maintaining the anonymity of the students, faculty, and staff.
ContributorsCarlson, Alyssa Rose (Author) / Halden, Rolf (Thesis director) / Gushgari, Adam (Committee member) / School of Human Evolution & Social Change (Contributor) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2020-05