Matching Items (24)
Filtering by
- All Subjects: chemical engineering
- Genre: Masters Thesis
- Creators: Emady, Heather
- Creators: Torres, Cesar
Description
To further the efforts producing energy from more renewable sources, microbial electrochemical cells (MXCs) can utilize anode respiring bacteria (ARB) to couple the oxidation of an organic substrate to the delivery of electrons to the anode. Although ARB such as Geobacter and Shewanella have been well-studied in terms of their microbiology and electrochemistry, much is still unknown about the mechanism of electron transfer to the anode. To this end, this thesis seeks to elucidate the complexities of electron transfer existing in Geobacter sulfurreducens biofilms by employing Electrochemical Impedance Spectroscopy (EIS) as the tool of choice. Experiments measuring EIS resistances as a function of growth were used to uncover the potential gradients that emerge in biofilms as they grow and become thicker. While a better understanding of this model ARB is sought, electrochemical characterization of a halophile, Geoalkalibacter subterraneus (Glk. subterraneus), revealed that this organism can function as an ARB and produce seemingly high current densities while consuming different organic substrates, including acetate, butyrate, and glycerol. The importance of identifying and studying novel ARB for broader MXC applications was stressed in this thesis as a potential avenue for tackling some of human energy problems.
ContributorsAjulo, Oluyomi (Author) / Torres, Cesar (Thesis advisor) / Nielsen, David (Committee member) / Krajmalnik-Brown, Rosa (Committee member) / Popat, Sudeep (Committee member) / Arizona State University (Publisher)
Created2013
Description
A new photocatalytic material was synthesized to investigate its performance for the photoreduction of carbon dioxide (CO2) in the presence of water vapor (H2O) to valuable products such as carbon monoxide (CO) and methane (CH4). The performance was studied using a gas chromatograph (GC) with a flame ionization detector (FID) and a thermal conductivity detector (TCD). The new photocatalytic material was an ionic liquid functionalized reduced graphite oxide (IL-RGO (high conductive surface))-TiO2 (photocatalyst) nanocomposite. Brunauer-Emmett-Teller (BET), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and UV-vis absorption spectroscopy techniques were employed to characterize the new catalyst. In the series of experiments performed, the nanocomposite material was confined in a UV-quartz batch reactor, exposed to CO2 and H2O and illuminated by UV light. The primary product formed was CO with a maximum production ranging from 0.18-1.02 µmol(gcatalyst-hour)-1 for TiO2 and 0.41-1.41 µmol(gcatalyst-hour)-1 for IL-RGO-TiO2. A trace amount of CH4 was also formed with its maximum ranging from 0.009-0.01 µmol(gcatalyst-hour)-1 for TiO2 and 0.01-0.04 µmol(gcatalyst-hour)-1 for IL-RGO-TiO2. A series of background experiments were conducted and results showed that; (a) the use of a ionic liquid functionalized reduced graphite oxide -TiO2 produced more products as compared to commercial TiO2, (b) the addition of methanol as a hole scavenger boosted the production of CO but not CH4, (c) a higher and lower reduction time of IL-RGO as compared to the usual 24 hours of reduction presented basically the same production of CO and CH4, (d) the positive effect of having an ionic liquid was demonstrated by the double production of CO obtained for IL-RGO-TiO2 as compared to RGO-TiO2 and (e) a change in the amount of IL-RGO in the IL-RGO-TiO2 represented a small difference in the CO production but not in the CH4 production. This work ultimately demonstrated the huge potential of the utility of a UV-responsive ionic liquid functionalized reduced graphite oxide-TiO2 nano-composite for the reduction of CO2 in the presence of H2O for the production of fuels.
ContributorsCastañeda Flores, Alejandro (Author) / Andino, Jean M (Thesis advisor) / Forzani, Erica (Committee member) / Torres, Cesar (Committee member) / Arizona State University (Publisher)
Created2014
Description
Due to depletion of oil resources, increasing fuel prices and environmental issues associated with burning of fossil fuels, extensive research has been performed in biofuel production and dramatic progress has been made. But still problems exist in economically production of biofuels. One major problem is recovery of biofuels from fermentation broth with the relatively low product titer achieved. A lot of in situ product recovery techniques including liquid-liquid extraction, membrane extraction, pervaporation, gas stripping and adsorption have been developed and adsorption is shown to be the most promising one compared to other methods. Yet adsorption is not perfect due to defect in adsorbents and operation method used. So laurate adsorption using polymer resins was first investigated by doing adsorption isotherm, kinetic, breakthrough curve experiment and column adsorption of laurate from culture. The results indicate that polymer resins have good capacity for laurate with the highest capacity of 430 g/kg achieved by IRA-402 and can successfully recover laurate from culture without causing problem to Synechocystis sp.. Another research of this paper focused on a novel adsorbent: magnetic particles by doing adsorption equilibrium, kinetic and toxicity experiment. Preliminary results showed excellent performance on both adsorption capacity and kinetics. But further experiment revealed that magnetic particles were toxicity and inhibited growth of all kinds of cell tested severely, toxicity probably comes from Co (III) in magnetic particles. This problem might be solved by either using biocompatible coatings or immobilization of cells, which needs more investigation.
ContributorsWang, Yuchen (Author) / Nielsen, David Ross (Thesis advisor) / Andino, Jean (Committee member) / Torres, Cesar (Committee member) / Arizona State University (Publisher)
Created2012
Description
The diversity of industrially important chemicals that can be produced biocatalytically from renewable resources continues to expand with the aid of metabolic and pathway engineering. In addition to biofuels, these chemicals also include a number of monomers with utility in conventional and novel plastic materials production. Monomers used for polyamide production are no exception, as evidenced by the recent engineering of microbial biocatalysts to produce cadaverine, putrescine, and succinate. In this thesis the repertoire and depth of these renewable polyamide precursors is expanded upon through the engineering of a novel pathway that enables Escherichia coli to produce, as individual products, both δ-aminovaleric acid (AMV) and glutaric acid when grown in glucose mineral salt medium. δ-Aminovaleric acid is the monomeric subunit of nylon-5 homopolymer, whereas glutaric acid is a dicarboxylic acid used to produce copolymers such as nylon-5,5. These feats were achieved by increasing endogenous production of the required pathway precursor, L-lysine. E. coli was engineered for L-lysine over-production through the introduction and expression of metabolically deregulated pathway genes, namely aspartate kinase III and dihydrodipicolinate synthase, encoded by the feedback resistant mutants lysCfbr and dapAfbr, respectively. After deleting a natural L-lysine decarboxylase, up to 1.6 g/L L-lysine could be produced from glucose in shake flasks as a result. The natural L-lysine degradation pathway of numerous Pseudomonas sp., which passes from L-lysine through both δ-aminovaleric acid and glutaric acid, was then functionally reconstructed in a piecewise manner in the E. coli L-lysine over-producer. Expression of davBA alone resulted in the production of over 0.86 g/L AMV in 48 h. Expression of davBADT resulted in the production of over 0.82 g/L glutaric acid under the same conditions. These production titers were achieved with yields of 69.5 and 68.4 mmol/mol of AMV and glutarate, respectively. Future improvements to the ability to synthesize both products will likely come from the ability to eliminate cadaverine by-product formation through the deletion of cadA and ldcC, genes involved in E. coli's native lysine degradation pathway. Nevertheless, through metabolic and pathway engineering, it is now possible produce the polyamide monomers of δ-aminovaleric acid and glutaric acid from renewable resources.
ContributorsAdkins, Jake M (Author) / Nielsen, David R. (Thesis advisor) / Caplan, Michael (Committee member) / Torres, Cesar (Committee member) / Arizona State University (Publisher)
Created2012
Description
Granulation is a process within particle technology where a liquid binding agent is added to a powder bed to create larger granules to modify bulk properties for easier processing. Three sets of experiments were conducted to screen for which factors had the greatest effect on granule formation, size distribution, and morphological properties when wet granulating microcrystalline cellulose and water. Previous experiments had identified the different growth regimes within wet granulation, as well as the granule formation mechanisms in single-drop granulation experiments, but little research has been conducted to determine how results extracted from single drop experiments could be used to better understand the first principles that drive high shear granulation. The experiment found that under a liquid solid ratio of 110%, the granule growth rate was linear as opposed to the induction growth regime experienced at higher liquid solid ratios. L/S ratios less than 100% led to a bimodal distribution comprised of large distributions of ungranulated powder and large irregular granules. Insufficient water hampered the growth of granules due to lack of enough water bridges to connect the granules and powder, while the large molecules continued to agglomerate with particles as they rotated around the mixer. The nozzle end was augmented so that drop size as well as drop height could be adjusted and compared to single-drop granulation experiments in proceeding investigations. As individual factors, neither augmentation had significant contributions to granule size, but preliminary screens identified that interaction between increasing L/S ratio and decreasing drop size could lead to narrower distributions of particles as well as greater circularity. Preliminary screening also identified that decreasing the drop height of the nozzle could increase the rate of particle growth during the 110% L/S trials without changing the growth mechanisms, indicating a way to alter the rate of steady-state particle growth. This paper screens for which factors are most pertinent to associating single-drop and wet granulation in order to develop granulation models that can ascertain information from single-drop granulations and predict the shape and size distribution of any wet granulation, without the need to run costly wet granulation experiments.
ContributorsLay, Michael (Author) / Emady, Heather (Thesis advisor) / Muhich, Christopher (Committee member) / Holloway, Julianne (Committee member) / Arizona State University (Publisher)
Created2019
Description
Carbon dioxide (CO2) levels in the atmosphere have reached unprecedented levels due to increasing anthropogenic emissions and increasing energy demand. CO2 capture and utilization can aid in stabilizing atmospheric CO2 levels and producing carbon-neutral fuels. Utilizing hollow fiber membranes (HFMs) for microalgal cultivation accomplishes that via bubbleless gas-transfer, preventing CO2 loss to the atmosphere. Various lengths and geometries of HFMs were used to deliver CO2 to a sodium carbonate solution. A model was developed to calculate CO2 flux, mass-transfer coefficient (KL), and volumetric mass-transfer coefficient (KLa) based on carbonate equilibrium and the alkalinity of the solution. The model was also applied to a sparging system, whose performance was compared with that of the HFMs. Typically, HFMs are operated in closed-end mode or open-end mode. The former is characterized by a high transfer efficiency, while the latter provides the advantage of a high transfer rate. HFMs were evaluated for both modes of operation and a varying inlet CO2 concentration to determine the effect of inert gas and water vapor accumulation on transfer rates. For pure CO2, a closed-end module operated as efficiently as an open-end module. Closed-end modules perform significantly worse when CO2-enriched air was supplied. This was shown by the KLa values calculated using the model. Finally, a mass-balance model was constructed for the lumen of the membranes in order to provide insight into the gas-concentration profiles inside the fiber lumen. For dilute CO2 inlet streams, accumulation of inert gases -- nitrogen (N2), oxygen (O2), and water vapor (H2O) -- significantly affected module performance by reducing the average CO2 partial pressure in the membrane and diminishing the amount of interfacial mass-transfer area available for CO2 transfer.
ContributorsShesh, Tarun (Author) / Rittmann, Bruce E. (Thesis advisor) / Green, Matthew (Committee member) / Torres, Cesar (Committee member) / Arizona State University (Publisher)
Created2018
Description
Rotary drums are commonly used for their high heat and mass transfer rates in the manufacture of cement, pharmaceuticals, food, and other particulate products. These processes are difficult to model because the particulate behavior is governed by the process conditions such as particle size, particle size distribution, shape, composition, and operating parameters, such as fill level and rotation rate. More research on heat transfer in rotary drums will increase operating efficiency, leading to significant energy savings on a global scale.
This research utilizes infrared imaging to investigate the effects of fill level and rotation rate on the particle bed hydrodynamics and the average wall-particle heat transfer coefficient. 3 mm silica beads and a stainless steel rotary drum with a diameter of 6 in and a length of 3 in were used at fill levels of 10 %, 17.5 %, and 25 %, and rotation rates of 2 rpm, 6 rpm, and 10 rpm. Two full factorial designs of experiments were completed to understand the effects of these factors in the presence of conduction only (Case 1) and conduction with forced convection (Case 2). Particle-particle friction caused the particle bed to stagnate at elevated temperatures in Case 1, while the inlet air velocity in Case 2 dominated the particle friction effects to maintain the flow profile. The maximum heat transfer coefficient was achieved at a high rotation rate and low fill level in Case 1, and at a high rotation rate and high fill level in Case 2. Heat losses from the system were dominated by natural convection between the hot air in the drum and the external surroundings.
This research utilizes infrared imaging to investigate the effects of fill level and rotation rate on the particle bed hydrodynamics and the average wall-particle heat transfer coefficient. 3 mm silica beads and a stainless steel rotary drum with a diameter of 6 in and a length of 3 in were used at fill levels of 10 %, 17.5 %, and 25 %, and rotation rates of 2 rpm, 6 rpm, and 10 rpm. Two full factorial designs of experiments were completed to understand the effects of these factors in the presence of conduction only (Case 1) and conduction with forced convection (Case 2). Particle-particle friction caused the particle bed to stagnate at elevated temperatures in Case 1, while the inlet air velocity in Case 2 dominated the particle friction effects to maintain the flow profile. The maximum heat transfer coefficient was achieved at a high rotation rate and low fill level in Case 1, and at a high rotation rate and high fill level in Case 2. Heat losses from the system were dominated by natural convection between the hot air in the drum and the external surroundings.
ContributorsBoepple, Brandon (Author) / Emady, Heather (Thesis advisor) / Muhich, Christopher (Committee member) / Holloway, Julianne (Committee member) / Arizona State University (Publisher)
Created2019
Description
Reactive inkjet printing (RIJP) is a direct-write deposition technique that synthesizes and patterns functional materials simultaneously. It is a route to cheap fabrication of highly conductive features on a versatile range of substrates. Silver reactive inks have become a staple of conductive inkjet printing for application in printed and flexible electronics, photovoltaic metallization, and more. However, the high cost of silver makes these less effective for disposable and low-cost applications.
This work aimed to develop a particle-free formulation for a nickel reactive ink capable of metallizing highly pure nickel at temperatures under 100 °C to facilitate printing on substrates like paper or plastic. Nickel offers a significantly cheaper alternative to silver at slightly reduced bulk conductivity.
To meet these aims, three archetypes of inks were formulated. First were a set of glycerol-based inks temperature ink containing nickel acetate, hydrazine, and ammonia in a mixture of water and glycerol. This ink reduced between 115 – 200 °C to produce slightly oxidized deposits of nickel with carbon content around 10 wt %.
The high temperature was addressed in a second series, which replaced glycerol with lower boiling glycols and added sodium hydroxide as a strong base to enhance thermodynamics and kinetics of reduction. These inks reduced between 60 and 100 °C but sodium salts contaminated the final deposits.
In a third set of inks, sodium hydroxide was replaced with tetramethylammonium hydroxide (TMAH), a strong organic base, to address contamination. These inks also reduced between 60 and 100 °C. Pipetting or printing onto gold coated substrates produce metallic flakes coated in a clear, thick residue. EDS measured carbon and oxygen content up to 70 wt % of deposits. The residue was hypothesized to be a non-volatile byproduct of TMAH and acetate.
Recommendations are provided to address the residue. Ultimately the formulated reactive inks did not meet design targets. However, this thesis sets the framework to design an optimal nickel reactive ink in future work.
This work aimed to develop a particle-free formulation for a nickel reactive ink capable of metallizing highly pure nickel at temperatures under 100 °C to facilitate printing on substrates like paper or plastic. Nickel offers a significantly cheaper alternative to silver at slightly reduced bulk conductivity.
To meet these aims, three archetypes of inks were formulated. First were a set of glycerol-based inks temperature ink containing nickel acetate, hydrazine, and ammonia in a mixture of water and glycerol. This ink reduced between 115 – 200 °C to produce slightly oxidized deposits of nickel with carbon content around 10 wt %.
The high temperature was addressed in a second series, which replaced glycerol with lower boiling glycols and added sodium hydroxide as a strong base to enhance thermodynamics and kinetics of reduction. These inks reduced between 60 and 100 °C but sodium salts contaminated the final deposits.
In a third set of inks, sodium hydroxide was replaced with tetramethylammonium hydroxide (TMAH), a strong organic base, to address contamination. These inks also reduced between 60 and 100 °C. Pipetting or printing onto gold coated substrates produce metallic flakes coated in a clear, thick residue. EDS measured carbon and oxygen content up to 70 wt % of deposits. The residue was hypothesized to be a non-volatile byproduct of TMAH and acetate.
Recommendations are provided to address the residue. Ultimately the formulated reactive inks did not meet design targets. However, this thesis sets the framework to design an optimal nickel reactive ink in future work.
ContributorsDebruin, Dylan Jerome (Author) / Torres, Cesar (Thesis advisor) / Rykaczewski, Konrad (Thesis advisor) / Hildreth, Owen (Committee member) / Arizona State University (Publisher)
Created2019
Description
While the solution diffusion model and pore flow model dominate pervaporation transport mechanism modeling, a new model combining the solution diffusion and viscous flow models is validated using membranes with large scale defects exceeding 2 nm in diameter. A range of membranes was characterized using scanning electron microscopy and x-ray diffraction (XRD) to determine quality and phase characteristics. MFI zeolite membranes of He/SF6 pure gas permeation ideal selectivities of 25, 15, and 3 for good, medium, and poor quality membranes were subjected to liquid pervaporations with a 5% ethanol in water feed, by weight. Feed pressure was increased from 1 to 5 atm, to validate existence of viscous flow in the defects. Component molar flux is modeled using the solution diffusion model and the viscous flow model, via J_i=F_i (γ_i x_i P_i^sat )+(ρ )/M_W ∅/μ_ij x_i P_h. A negative coefficient of thermal expansion is observed as permeances drop as a function of temperature in all three membranes, where ϕ=((ϵr_p^2)/τ∆x). Experimental parameter ϕ increased as a function of temperature, and increased with decreasing membrane quality. This further proves that zeolitic pores are shrinking in one direction, and pulling intercrystalline voids larger, increasing the (ϵ/τ) ratio. Permiabilities of the bad, medium, and good quality membrane also decreased over time for both ethanol and water, meaning that fundamental membrane characteristics changed as a function of temperature. To conclude, the model reasonably fits empirical data reasonably well.
ContributorsWilliams, Suzanne Jean (Author) / Lin, Jerry Y.S. (Thesis advisor) / Emady, Heather (Committee member) / Mu, Bin (Committee member) / Arizona State University (Publisher)
Created2016
Description
Synthetic biology and metabolic engineering has aided the production of chemicals using renewable resources, thus offering a solution to our dependence on the dwindling petroleum resources. While a major portion of petroleum resources go towards production of fuels, a significant fraction also goes towards production of specialty chemicals. There has been a growing interest in recent years in commercializing bio-based production of such high value compounds. In this thesis the biosynthesis of aromatic esters has been explored, which have typical application as flavor and fragrance additive to food, drinks and cosmetics. Recent progress in pathway engineering has led to the construction of several aromatic alcohol producing pathways, the likes of which can be utilized to engineer aromatic ester biosynthesis by addition of a suitable enzyme from the acyltransferase class. Enzyme selection and screening done in this work has identified chloramphenicol O-acetyltransferase enzyme(CAT) as a potential candidate to complete the biosynthetic pathways for each of 2-phenethyl acetate, benzyl acetate, phenyl acetate and acetyl salicylate. In the end, E. coli strains capable of producing up to 60 mg/L 2-phenethyl acetate directly from glucose were successfully constructed by co-expressing CAT in a previously engineered 2-phenylethanol producing host.
ContributorsMadathil Soman Pillai, Karthika (Author) / Nielsen, David (Thesis advisor) / Wang, Xuan (Committee member) / Torres, Cesar (Committee member) / Arizona State University (Publisher)
Created2016