Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, June 2017. / "September 2015." Cataloged from PDF version of thesis. / Includes bibliographical references (pages 195-200). / Large-scale carbon dioxide (CO₂) separation is essential in the efforts to curb climate change, with applications in power stations, natural gas purification and enhanced oil recovery. Current CO₂ capture technology is energetically intensive, and challenging to deploy in existing power stations. Electrochemical CO₂ separation is a novel technology that has the potential to reduce CO₂ capture costs. By cycling of metal ions to modulate the CO₂ affinity of amine sorbents, energy and capital requirements can be significantly cut. The feasibility of this approach was previously demonstrated with a proof-of-concept device, but was limited by low energy efficiency and instability. This thesis describes a systematic effort to optimize this technology by exploring its design space, and identifying conditions for robust, energy efficient operation. The large effect of electrolytes on activation kinetics was explored via galvanostatic pulse voltammetry and bench-scale experiments. In the presence of halide electrolytes, energy efficiency was improved for short times, but bench-scale experiments showed an increase in resistance for longer operation, possibly due to electrolyte inclusion in the metal deposit. For the set of the electrolytes tested, nitrates were found to drive the most stable kinetics at moderate energy efficiencies. To explore the electrochemical cell performance for a range of designs and operating conditions, a modeling framework combining thermodynamics, electrode reactions and mass transfer was developed. Model predictions suggest the cell will operate in a mixed kinetic-mass transfer regime at the desired current densities. Model results further predict that introducing flow field disturbances to induce mixing between the bulk and boundary layer will improve energy efficiency significantly. A bench-scale system with modular internals was constructed and used to investigate performance effects of flow field designs. Model predictions were found to be in good qualitative agreement with experimental results. Under optimized conditions, an almost 70% lower voltage at 50 A/m2 was demonstrated. Electrochemical impedance spectroscopy experiments provide further evidence to the mixed kinetics-mass transfer regime of operation. A detailed energy and cost analysis was performed, and results suggest that this technology can cut capture costs significantly if the performance improvement can be sustained for longer operation. / by Aly Eldeen O. Eltayeb. / Ph. D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1995. / Includes bibliographical references (leaves 226-233). / by Alexandros Koulouris. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1987. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Vita. / Bibliography: p. 316-326. / by Thomas P. Gandek. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2010. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 131-135). / Solvents play an important role in crystallization, a commonly used separation and purification technique in the pharmaceutical, chemical and food industries. They affect crystal properties such as particle size distribution, morphology, polymorphism etc. and therefore have consequences for the downstream processing of the solid material. Current solvent selection techniques for solution crystallization remain ad hoc and typically do not have a theoretical underpinning. Elucidation of the interactions between solvent and solute molecules and the mechanism underlying the solvent effects on each aspect of the crystal properties would be a major aid for the rational selection of solvents and also the development of crystallization processes. In this work we studied the effect of solvent on the polymorphism and morphology of organic crystals using molecular modeling techniques. The two most important contributions of this thesis are listed below. 1. We studied the self-assembly of solute molecules in solutions prior to nucleation for two polymorphic systems, tetrolic acid and glycine, using molecular dynamics simulations. We tested the existence of a link between the structure of the clusters formed in solution and the polymorphism of the crystals. Our results show that the link hypothesis succeeds in explaining the polymorph selection of tetrolic acid from different solvents. However it fails for glycine and thus should be used with caution. 2. We designed a computer-aided rational solvent selection procedure for improving the morphology of needle-like 2,6-dihydroxybenzoic acid form 2 crystal. We also experimentally grew 2,6-dihydroxybenzoic acid form 2 crystals using the solvent mixture suggested by computer simulations, which do exhibit reduced aspect ratios. This computer-aided selection procedure can not only quickly identify an effective solvent or solvent mixture, but also provide mechanistic understandings of the underlying chemistry. It can also be extended to improve the morphology of other needle-like organic crystals easily. / by Jie Chen. / Ph.D.

Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1981. / MIT copy bound with: Solute concentration effects on the rejection of rigid macromolecules from microporous membranes / by Debasish Tripathy [1981] / Includes bibliographical references (leaf 32). / byt Frank Andrew Ubel, III. / B.S.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2016. / Cataloged from PDF version of thesis. / Includes bibliographical references. / One of the important problems in the field of orthopedic medicine is the ability to create a stable bone-materials interface with an implant, particularly when faced with the difficult condition of bone infection. Only recently have we come to understand the significance of addressing infection during the bone wound healing process; however, to apply this understanding toward an effective treatment requires the ability to deliver exacting amounts of therapeutics of different types over the appropriate timeframes in and around the implant. This task must be accomplished while maintaining the mechanical integrity of the implant materials and allowing for bone integration on their surfaces. Here we present a novel, particularly enabling next-generation implant solution for both eradication of an established biofilm within the bone cavity and accelerated bone repair via the controlled delivery of antibiotic and growth factor in sequence from stable nanometer scale coatings on the implant surface. Infection is by far the most common reason for complications, which often lead to complete removal of implants (74.3%). Infection significantly increases morbidity, and places huge financial burdens on the patient and the healthcare system-projected to exceed $1.62 billion/year by 2020. Because infection is much more common in implant replacement surgeries, these issues greatly impact long-term patient care for a continually growing part of the population. For revision arthroplasty of an infected prosthesis, a prolonged and expensive twostage procedure requiring two surgical steps and a 6-8 week period of joint immobilization exists as today's gold standard. A single-stage revision is preferred as an alternative; however, traditional bulk polymer systems such as bone cement cannot load sufficient amounts of therapeutic to eradicate existing infection, are insufficient or infeasible for the release of sensitive biologic drugs that considerably aid in bone regeneration, and lead to substandard mechanical properties and retarded bone repair. To address these issues, we created conformal, programmable, and degradable dual therapy coatings (~500 nm thick) in a layer-by-layer fashion using the enabling nanofabrication tool of electrostatic multilayer assembly. The nanolayered construct allows large loadings of each drug, thus enabling ultrathin film coatings to carry sufficient treatment and precise independent control of release kinetics and loading for each therapeutic agent in an infected implant environment. The coating architecture was adapted to allow early release of antibiotics contained in top layers sufficient to eliminate infection, followed by sustained release above the MIC over several weeks; whereas, the underlying BMP-2 growth factor layers enabled a long-term sustained release of BMP-2, which induced more significant and mechanically competent bone formation than a short-term burst release. In rats, the successful growth factor-mediated osteointegration of the multilayered implants with the host tissue improved bone-implant interfacial strength by impressive amounts (15-fold) when compared with the bare implant control, and yields a mechanical bond 17-fold higher than that created with the use of clinically available bioactive bone cement. Here we focused on dual delivery of an antibiotic and a growth factor owing to the urgent need for enhanced infection-reducing and tissue-integrating strategies in orthopedic applications, but the excellent modularity of multilayers for incorporation and release of diverse therapeutics suggests this approach should be also applicable to different implant applications such as vascular graft and artificial heart implants for which the risks of infection are often ignored. Our findings demonstrate the potential of this layered release strategy to introduce a durable implant solution, ultimately an important step forward in the design of biomedical implant release coatings for multiple medical applications. In addition to focusing on multi-therapeutic multilayer coatings for macroscale implants and scaffolds, I have also extended the work to understand release properties of the therapeutic agents, guided by predictive mathematical modeling of the release mechanisms involved in polyelectrolyte multilayer films and cell uptakes based on the principles of polymer physics and molecular and cellular biology. The potential impact of this work is substantial: introduce the next-generation biomaterials and implantable devices, save billions of dollars in the healthcare cost, and directly benefit the rapidly growing current and future generations of patients relying on medical device. / by Jouha Min. / Ph. D.

Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1973. / Vita. / Includes bibliographical references. / by Arun K. Mehta. / Sc.D.

Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1995. / Includes bibliographical references (v. 2, leaves 280-286). / by John F. Carrier. / Sc.D.

Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1983. / MIT copy bound with: Flotation of organic molecules / by Charles W. Billings [1983] / Includes bibliographical references (leaves 83-85). / by Susan Diane Flynn. / B.S.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2011. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 194-208). / Reactive nitrogen species (RNS) derived from nitric oxide (NO) have been implicated in cancer and other diseases, but their intracellular concentrations are largely unknown. To estimate them under steady-state conditions representative of inflamed tissues, a kinetic model was developed that included the effects of cellular antioxidants, amino acids, proteins, and lipids. For an NO concentration of 1 [mu]M, total peroxynitrite (Per, the sum of ONOO- and ONOOH), nitrogen dioxide (NO2), and nitrous anhydride (N20 3) were calculated to have concentrations in the nM, pM, and fM ranges, respectively. The concentrations of NO2 and N20 3 were predicted to decrease markedly with increases in glutathione (GSH) levels, due to the scavenging of each by GSH. Although lipids accelerate the oxidation of NO by 02 (because of the high solubility of each in hydrophobic media), lipid-phase reactions were calculated to have little effect on NO2 or N20 3 concentrations. The major sources of intracellular NO2 were found to be the reaction of Per with metals and with CO 2, whereas the major sinks were its reactions with GSH and ascorbate (AH-). The radical-scavenging ability of GSH and AH- caused 3-nitrotyrosine to be the only tyrosine derivative predicted to be formed at a significant rate. The major GSH reaction product was S-nitrosoglutathione. Analytical (algebraic) expressions were derived for the concentrations of the key reactive intermediates, allowing the calculations to be extended readily. To investigate the mutagenic and toxic effects of NO on cells, methods are needed to expose them to constant, physiological levels of NO for hours to days. One way to do this is to co-culture target cells with activated macrophages, which can synthesize NO at constant rates for long periods. A novel method, developed in the laboratory of Professor G. N. Wogan at MIT, involves the use of TranswellTM permeable supports (Coming), in which a porous membrane separates two chambers in a culture dish. Target cells and macrophages are placed on the top and bottom of the insert, respectively. Although the two cell types are in close diffusional contact, the target cells can be recovered separately for viability and mutation assays. To infer the NO concentration at the level of the cells from measured rates of formation of nitrite (N02-), a reaction-diffusion model was developed to calculate NO and 02 concentrations as a function of height in the medium. In this system the oxidation of NO to NO2 competes with the diffusional loss of NO to the incubator gas. It was shown that a one-dimensional, steady-state formulation is justified. The key factors affecting NO and 02 concentrations are the total rate of respiratory 02 consumption by the cells and their net rate of NO generation. Because the overall rate of the multi-step NO oxidation is second order in NO, the fractional loss of NO from the system by diffusion increases as the NO concentration is reduced. Also, the fractional loss of NO is increased if cellular 02 consumption is elevated. The cellular NO concentration was predicted to be nearly proportional to the square root of the NO2 formation rate. Thus, in experiments in the Wogan laboratory in which NMA (an inhibitor of NO synthase) was added to the culture medium, reducing NO2 formation by 90%, the cellular NO concentration was calculated to decrease only by about two-thirds (from 1.1 [mu]M to 0.36 [mu]M). To facilitate the use of the reaction-diffusion model by other laboratories, a graphical method was developed to allow cellular NO concentrations to be estimated from measured rates of NO2 accumulation. The controlled delivery of NO2 into aqueous solutions, in the absence of NO, would be useful in investigating its rates of reaction with biological molecules and in isolating its effects on cells from those of other RNS. Two possible NO2 delivery methods were investigated theoretically. One was the direct contact of NO2 gas mixtures with stirred aqueous solutions, and the other was diffusion of NO2 through gas-permeable tubing (such as polydimethylsiloxane, PDMS) into such solutions. In gases and in water, NO2 dimerizes reversibly to form dinitrogen tetroxide (N204), which reacts rapidly with water to produce nitrite and nitrate. Thus, it was necessary to describe the coupled reaction and diffusion of NO2 and N20 4 in each kind of system. Microscopic models were developed to describe spatial variations in concentrations near the gasliquid interface, or within the tubing wall and immediately adjacent liquid. These were used to predict parameter values (such as mass transfer coefficients) in macroscopic models designed to describe bulk aqueous concentrations. Because the direct measurement of NO2 and N20 4 concentrations at the low levels desired for biological experiments is impractical, the combined models are needed to estimate bulk NO2 and N20 4 concentrations from measurable quantities such as rates of N0 2- accumulation. For direct gas-liquid contacting, the utility of a quasiequilibrium approximation (QEA) was examined. This assumes that the NO2 and N20 4 concentrations are related as for dimerization equilibrium. At relatively high NO2 concentrations in the delivery gas, the results from the QEA and exact equations were in excellent agreement. As the NO2 level was reduced, the QEA eventually fails, because NO2 increasingly resembles an unreactive species as its concentration approaches zero. However, the QEA was found to be quite accurate throughout the practical range of concentrations (0.001% to 1% NO2 gas), the relative error in total fluxes not exceeding 6%. The results show that it is desirable to use as low an NO2 concentration as is analytically feasible (such as 0.001% NO2 gas). This minimizes both the concentration of N20 4 and the effects of concentration nonuniformities in the aqueous boundary layer. For NO2 delivery through gas-permeable tubing such as PDMS, the modeling was more complicated and the results more uncertain. The main complication was due to the presence of a concentration boundary layer within the membrane next to the liquid, which required that the governing equations be rescaled for that region. The major source of uncertainty is the unknown solubility of N20 4 in PDMS. However, as the gas concentration was lowered, the results became insensitive to this parameter. For 1% NO2 gas, the estimated bulk NO2 concentrations were 7.1 pM for the direct gas contact and 0.35 pM for the gas-permeable tubing. For 0.001% NO2 gas, the estimated NO2 concentrations were 0.45 [mu]M for the direct gas contact and 0.14 [mu]M for the gas-permeable tubing. For both methods, the times to reach steady state were predicted to be quite fast, at most 10 seconds. / by ChangHoon Lim. / Ph.D.