Foram sintetizadas duas novas séries de tensoativos de açúcar derivados da 2-D-glucosamina: os metil 2-acilamido-2-deóxi-6-O-sulfonato-D-glucopiranosídeos de sódio (aniônicos) e os cloretos de metil 2-acilamido-2,6-dideóxi-6-trimetilamônio-D-glucopiranosídeos (catiônicos). Os tensoativos aniônicos foram obtidos pela acilação da 2-D-glucosamina com cloretos de acila (com 8, 12 e 16 carbonos), seguida pela metilação desses derivados com metanol em meio ácido, e posterior sulfatação dos metil glucosídeos com complexo trióxido de enxofre-piridina. Os tensoativos catiônicos foram obtidos pela tosilação dos metil glucosídeos, seguida pela quaternização com trimetilamina e troca do contra-íon tosilato por cloreto com resina de troca-iônica. Esses tensoativos apresentaram c.m.c. similares a de outros tensoativos iônicos de cadeia hidrofóbica de igual comprimento, mas energias livres de transferência do grupo polar para a micela muito mais favoráveis. Esse fato foi atribuído à formação de ligações de hidrogênio entre os grupos polares do tensoativo na micela, e à hidrofobicidade do açúcar. As micelas formadas apresentaram números de agregação maiores que os obtidos para outros tensoativos, provavelmente devido às interações atrativas entre os grupos polares. / Two new sugar-based surfactant series were synthesized from 2-D-glucosamine: sodium methyl 2-acylamido-2-deoxi-6-O-sulfonate-D-glucopyranosides (anionic) and methyl 2-acylamido-2,6-dideoxi-6-trimethylamonium-D-glucopyranoside chlorides (cationic). The anionic surfactants were obtained by the acylation of 2-D-glucosamine with acyl chlorides (with 8, 12 and 16 carbons), followed by the methylation of these derivatives with methanol in acidic media, and the sulfation of the methyl glucosides with sulfur trioxide-pyridine complex. The cationic surfactants were obtained by the tosylation of methyl glucosides followed by the quaternization with trimethylamine and exchange of the tosylate contra-ion with chloride ions on an ion exchange resin. These surfactants showed c.m.c. similar to other ionic surfactants with equal hydrophobic chain lengths, but more favorable free energies of transfer of the polar head to the micelle. This fact is attributed to hydrogen bonding between the head groups of the surfactant in the micelle, and the hydrophobicity of the sugar moiety. The micelles of these surfactants showed aggregation numbers larger than those obtained for other surfactants, problably because of head-group attractive interactions.

abstract: Organic compounds are influenced by hydrothermal conditions in both marine and terrestrial environments. Sedimentary organic reservoirs make up the largest share of organic carbon in the carbon cycle, leading to petroleum generation and to chemoautotrophic microbial communities. There have been numerous studies on the reactivity of organic compounds in water at elevated temperatures, but these studies rarely explore the consequences of inorganic solutes in hydrothermal fluids. The experiments in this thesis explore new reaction pathways of organic compounds mediated by aqueous and solid phase metals, mainly Earth-abundant copper. These experiments show that copper species have the potential to oxidize benzene and toluene, which are typically viewed as unreactive. These pathways add to the growing list of known organic transformations that are possible in natural hydrothermal systems. In addition to the characterization of reactions in natural systems, there has been recent interest in using hydrothermal conditions to facilitate organic transformations that would be useful in an applied, industrial or synthetic setting. This thesis identifies two sets of conditions that may serve as alternatives to commonplace industrial processes. The first process is the oxidation of benzene with copper to form phenol and chlorobenzene. The second is the copper mediated dehalogenation of aryl halides. Both of these processes apply the concepts of geomimicry by carrying out organic reactions under Earth-like conditions. Only water and copper are needed to implement these processes and there is no need for exotic catalysts or toxic reagents. / Dissertation/Thesis / Masters Thesis Geological Sciences 2020

The global demand for potable water has increase the use of chemicals to clean or prevent undesirable biofouling in reverse osmosis membranes. Biofouling is the growth and accumulation of biomass that generates an unacceptable performance decline. To date, a thoroughly efficient and green method to remove, prevent or treat biofouling in water treatment systems has not been developed. The studies carried out during my Ph.D. aim to develop greener and more efficient biofuling prevention/cleaning methods. The first two studies introduce a polyelectrolyte coating with the atypical characteristic of being removed and reapplied under operating conditions. After the biofilm develops on the coating, both biomass and coating can be removed with brine. The application of the coating can be done in-situ without hindering membrane performance. Using this procedure, both biofilm and coating could be simultaneously removed, leaving a clean surface. The biofouled coated membrane had two-fold higher permeate flux recovery compare to the non-coated. The sacrificial polyelectrolyte coating offers a greener solution for biofouling treatment in membrane systems. As an alternative to harsh chemicals, natural deep eutectic solvents (NADES) are presented as an alternative for biofilm treatment. Our results indicate that the NADES could solubilize up to ≈70% of the main components of the biofilm. The biofilm is weakened by the biomolecule’s solubilization, which could enhance biofilm removal. NADES have a great potential to be used for biofilm and avoid the currently used solvents. The last chapter is focused on understanding the structural characteristics and stability of NADES composed of betaine, urea, and water. The NADES composition and the water content is of significant relevance for its stability and supramolecular structure. Our experimental and computational results show that water is of crucial importance to the NADES supramolecular structure and stability. Understanding the NADES characteristics leads to finding better applications and giving insights into the interaction that these solvents have with other molecules, such as biopolymers or proteins. Even though there is still further research to be done, the studies presented on this thesis are a step forward towards finding and understanding greener solutions for biofilm treatment in water treatment systems.

>Magister Scientiae - MSc / Current research classifies Type 2 diabetes as most prevalent non-communicable diseases in South Africa. Approximately 285 million people are affected globally with an expected increase to 595 million by the year 2035. Synthetic first-line drugs in the treatment of Type 2 diabetes, have been shown to have an efficacy rate of approximately 43% as a result of poor drug uptake and metabolism. Furthermore, given South Africa’s uniquely diverse botanical heritage, herbs commonly used traditional medicine have shown promise in the treatment of Type 2 diabetes.

Abstract: The aim of this research is to fabricate thin-film composite (TFC) membranes using a synthetic derivative of plant-based phenols, as a non-toxic building block for interfacial polymerization. Classical interfacially polymerized composite membranes are heavily integrated in reverse osmosis and nanofiltration applications for water and wastewater treatment and most recently for chemical and pharmaceutical industries. Implementing sustainable practices in membrane fabrication by exploiting greener alternatives to conventional chemicals can directly reduce hazardous waste and ultimately lower the global energy and environmental burdens. In this study, allyl gallate was chosen as a monomer to form selective thin films by the interfacial reaction with trimesoyl chloride on top of an asymmetrically porous polyacrylonitrile support. The advantage of the unreacted allyl groups is that they can be in the future used as post-functionalization sites. The highly volatile organic phase solvents were additionally replaced by an isoparaffinic fluid, commercially known as Isopar G. The chemical composition and morphology of the membrane was evaluated using solid-state 13C NMR, FTIR, and SEM. The optimized membrane resulted in a permeance of 12±2 and 48±14 L m-2 h-1 bar-1 for respectively pure water and methanol with a rejection in the nanofiltration range.

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Evidence suggests that the recent drastic changes in the global climate have been caused by greenhouse gases, especially CO­2. As a result, scientists are aiming to develop processes that either minimize the production of these gases or convert them into products of higher value. To that end, the catalytic properties of a two-dimensional boron-rich material were investigated. Herein is reported that such a material can reduce CO2 into benzene, C3 species, and C4 species at relatively low temperatures (225-450 ℃) and pressures (0.38 MPa). Current data suggest that a low-temperature induction period (e.g., 225 ℃) is needed to achieve the conversion of CO2 into benzene whereas the conversion of CO2 into light hydrocarbons does not require such a pretreatment. Additionally, it was found that Al1-xB2 loses its activity after approximately 17 hours. Such loss of activity may be due to the buildup of non-volatile compounds on the active sites (coking). Work presented here also indicates that Al(OH)3 species left behind after the preparation of Al1-xB2 act synergistically with the boron sheets, enhancing activity. The level of enhancement appears to depend heavily on the way Al(OH)3 is introduced into the system. Grinding amorphous boron and Al(OH)3 by hand afforded the greatest reactivity towards CO2, albeit it needs to be confirmed whether the B atoms are being actively consumed during the reaction. On the other hand, exposing Al1-xB2 to air during its synthesis yields a more reactive material, suggesting that air plays a significant role. Based on this, if the synthetic route of Al1-xB2 is optimized, it is certain to yield an industrially suitable catalyst. Finally, ∆Gºrxn calculations can be utilized to partially predict the observed product distributions, albeit more advanced calculations are needed.

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