3. Electronic Theses and Dissertations (ETDs) - All submissions
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Item A CO2 capture technology using carbon nanotubes with polyaspartamide surfactant(2016-07-13) Ngoy, Jacob MasialaTechnologies for the separation of CO2 from flue gas require a feat of engineering for efficient achievement. Various CO2 capture technologies, including absorption, adsorption, cryogenics and membranes, have been investigated globally. The absorption technology uses mainly alkanolamine aqueous solutions, the most common being monoethanolamine (MEA); however, further investigation is required to circumvent its weakness due to degradation through oxidation, material corrosion and high energy costs required for regeneration. Attractive advantages in adsorption technology, including the ability to separate the more diluted component in the mixture with a low energy penalty, have been a motivation for many researchers to contribute to the advancement of adsorption technology in CO2 capture. The challenge in CO2 adsorption technology is to design a hydrophobic and biodegradable adsorbent with large CO2 uptake, high selectivity for CO2, adequate adsorption kinetics, water tolerance, and to require low levels of energy for regeneration processes. The existing adsorbent such as activated carbon, silica gel, zeolites, metal organic frameworks and others, have been ineffective where moisture occurs in flue gas. This work provides an advanced adsorption technology through a novel adsorbent, MWNT-PAA, designed from the noncovalent functionalization of multi-walled carbon nanotubes (MWNTs) by polyaspartamide (PAA) as product of amine grafted to polysuccinimide (PSI). Three types of PAA were prepared using ethylenediamine (EDA), 1, 3 propanediamine (PDA) and monoethanolamine (MEA) drafted to PSI to give PSI-EDA, PSI-PDA and PSI-MEA respectively. The CO2 adsorption capacity was 13.5 mg-CO2/g for PSI-PDA and 9.0 mg-CO2/g for PSI-MEA, which decreased significantly from PSI where the CO2 adsorption capacity was 25 mg-CO2/g. PSIEDA was selected as PAA, because the CO2 adsorption capacity was 52 mg-CO2/g which doubled from PSI. The polymer polyethylenimine (PEI), the most commonly polymer used in CO2 capture, was found to be non-biodegradable, while the polymer PAA showed the presence of CONH as a biodegradable bond functionality, occurring in the MWNT-PAA, as confirmed through Fourier Transform Infrared (FTIR) analysis. The adsorbent MWNT-PAA was demonstrated to have a water tolerance in the temperature range 25-55 ℃, where CO2 adsorption capacity increased with the increase of water in the adsorbent. The highest CO2 adsorption capacity recorded was 71 mg-CO2/g for the moist MWNT-PAA using 100% CO2 and 65 mg-CO2/g for the mixture of 14% CO2 with air. Under the same conditions, the dry MWNT-PAA adsorbed 70 and 46 mg-CO2/g respectively (100%, 14% CO2). The 2 regenerability efficiency of the MWNT-PAA absorbent was demonstrated at 100 ᵒC; after 10 cycles of adsorption-desorption 99% of adsorbed gas was recovered in the desorption process. The heat flow for the thermal swing adsorption system resulted in the net release of heat over the complete cycle; a cycle includes adsorption (heat release) and desorption (heat absorbance). Thus, this MWNT-PAA adsorbent demonstrates an advantage in terms of overall energy efficiency, and could be a competitive adsorbent in CO2 capture technology.Item Polymer and carbon nanotube bound folic acid and methotrexate for cancer therapy(2011-04-19) Ngoy, Jacob MasialaFolic acid (FA) is an amino acid that helps in the replication of normal cells and it deficiency may lead to oncogenic cells development. Methotrexate (MTX) on the other hand is a highly potent drug against leukemia and other neoplasias, which can induce toxic side effects and drug resistance to target cells. The principal objective was to develop a bioconjugate that will enhance therapeutic effectiveness of these agents (FA and MTX) using functionalized carbon nanotubes and polymer toward cancer cells. Furthermore, bioreversible binding to a watersoluble and biocompatible carrier polymer and carbon nanotubes are advanced technology designed to circumvent critical pharmacological and efficacious biological action. The formation of biofissionable bond (CONH) for drug release was evaluated in this work by using nuclear magnetic resonance (NMR) spectra with D2O as solvent, and infrared (IR) spectra to identify the necessary peak shifts for the bioreversible conjugation of FA and MTX as anticancer drug. Polyaspartamide and carbon nanotubes (CNTs) were both functionalized and used as carriers for solubility behavior, steric accessibility and reactivity of anchoring sites, aiming to enhance therapeutic effectiveness of MTX. In order to obtain the polymeric carrier, to polysuccinimide (PSI) synthesized via polycondensation of aspartic acid was attached 3-(N,N–dimethylamino)propylamine (DMP) and 1,3-propylenediamine (PDA) for solubility behavior and reactivity of anchoring of the drug respectively. This, through the use of an ester 2-(1H-benzotrial-1-yl)-1,1,3,3- tetramethylurium hexafluorophosphate (HBTU), as coupling agent led to the polymer drug conjugate after reacting with FA. The reaction was subjected to the polymer cleavage which caused the dropping of yield after chromatography and dialysis operations. After kinetic reaction investigation, the optimum reaction time was set within the range of 120-130 minutes for an optimum yield of coupling within the range of 80-85% where the incorporation of FA in the polymer was maximum though the polymer cleavage. In addition, CNTs obtained via chemical vapour deposition (VCD) was covalently functionalized at RT, 50ºC and 100ºC with a mixture of sulphuric and nitric acids to generate the phenol and carboxyl groups on the surface, and at 230 ºC with aspartic acid to generate only the carboxyl group. It resulted that the mol ratio (OH/COOH) was increasing, the size of f-CNTs was decreasing from 80, 30 to 20nm and the water solubility was increasing with the increase in temperature from RT, 50ºC to 100ºC. The carboxyl on the surface of f-CNTs was attached to DMP and FA through HBTU to get f-CNTs-FA conjugate. This resulted to the prodrug with different sizes of 50nm and 170nm with 94% and 101.3% incorporation of folic acid respectively. CNTs noncovalently coated with polysuccinimide (PSI) in DMF at 160ºC were attached to DMP and PDA. Thereafter, FA reacted with PDA via HBTU to give a prodrug of 60nm with 105.3% FA incorporation. The f-CNTs functionalized with polymer can be more beneficial due to the size for the cell penetration and average molecular weight for renal clearance. Therefore the biomedical evaluation is recommended for future work.