Formaldehyde, a hazardous and toxic substance, can be found in most resin treated durable press fabrics. The current formaldehyde regulations are limited to worker exposure in an industrial setting and the possibility of government regulation of formaldehyde release from textiles is of concern to the textile industry. The most common test of formaldehyde release used by the U.S. textile industry is the AATCC Test Method 112, a colorimetric determination based on the Hantzsh reaction between ammonia, formaldehyde, and acetylacetone. The chromophore formed is 3,5-diacetyl-1,4-dihydrolutidine (DDL). In the AATCC test the ammonia and acetylacetone are in the Nash reagent and the formaldehyde is extracted from the fabric by trapped steam. The formaldehyde in solution and the Nash reagent are mixed and the color developed. The purpose of this study was to determine if a more effective formulation of the Nash reagent than currently used by industry can be produced. The reaction between the Nash reagent and formaldehyde is first order in formaldehyde, therefore pseudo-first order kinetics was used as the basis of the study. Reagent effectiveness was determined by comparisons and calculations based on the molar extinction coefficient, maximum absorbance, and rate constant. The study was set up in phases to investigate the effect of different ammonia sources, the effects of varying concentrations of the reactant components, the effect of ageing, and the effect of different temperatures on the formation of DDL. In the final phase the best reformulated reagent was compared to the Nash reagent under the conditions of the AATCC Test Method 112. Several reformulations were found to be comparable to Nash, but none was found to be more effective in formaldehyde detection. This study has shown some of the complexities of the reaction and that the Nash reagent is not able to obtain 100% conversion of formaldehyde to DDL. Therefore, any test that uses the Nash reagent is underestimating the releasable formaldehyde concentration in the fabric. / Ph. D.

Call number: LD2668 .T4 1984 T78 / Master of Science

published_or_final_version / abstract / Chemistry / Doctoral / Doctor of Philosophy

M.Sc.(Nanoscience) / The synthesis and application of gold nanoparticles (AuNPs) has been intensively studied worldwide. However, the toxicity of these nanoparticles is still a concern. We considered that various physiochemical methods used to synthesize AuNPs are energy driven, costly and require the use of harmful chemicals. Thus, this makes them not environmentally-friendly. The aim of this study was therefore to synthesize AuNPs via a greener route using Aspalathus linearis tea leaves. The AuNPs were used to coat eight commercial antifungal discs (i.e. amphotericin B, fluconazole, clotrimazole, econazole, flucytosine, ketoconazole, miconazole and nystatin) against four Aspergillus spp. for enhanced antifungal activity. The aqueous extract of A. linearis was characterized by high performance liquid chromatography and liquid chromatography–mass spectroscopy. The AuNPs were characterized using ultravioletvisible (UV-vis) spectroscopy, dynamic light scattering, nanoparticle tracking analysis, Fourier transforms infrared spectroscopy (FTIR), high-resolution transmission electron microscopy and X-ray diffraction. The toxicity of the synthesized AuNPs was studied by 3-(4, 5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) assay and xCELLigence test on HepG-2 cell lines and results revealed very little to no toxicity of the AuNPs. The pristine antifungal and AuNPs coated antifungal discs were characterized by FTIR, scanning electron microscopy (SEM) and antifungal activity performed using the disc diffusion method. A strong resonance peak was observed at 529 nm of the AuNPs measured using UV-vis spectroscopy. Average size of AuNPs was ~44±1 nm and demonstrated excellent in-vitro stability under various solutions (5% NaCl, phosphate buffered saline) at varying pH levels. The SEM images revealed that the AuNPs were attached onto the coated antifungal discs when compared with the pristine antifungal discs. Antifungal results indicated that AuNPs significantly (p<0.001) enhanced the antifungal activity of the coated antifungal discs against the tested fungi when compared to the pristine antifungal discs. The AuNPs coated econazole disc exhibited the greatest (broad spectrum) activity than other antifungal agents tested. In conclusion, A. linearis can be used as a reducing agent in the synthesis of stable AuNPs. Furthermore, the AuNPs coated antifungal discs demonstrated considerable antifungal activity over the pristine antifungal discs...

Resumo: O produto comercial Roundup®, contendo o glifosato como principal ingrediente ativo, é vendido mundialmente por ser um herbicida sistêmico, pós-emergente e não seletivo. Além disso, a alta eficiência no processo de remoção de plantas indesejadas e o aumento de culturas transgênicas favorecem seu uso extensivo. Embora não seja considerado um sério contaminante para o homem, o controle e monitoramento destes herbicidas são muito importantes. Desta forma, o presente projeto propõe o desenvolvimento de sistemas de screening e métodos analíticos limpos que possam ser aplicados à determinação de glifosato, uma vez que a literatura dispõe de poucos métodos de análise que visam à aplicação dos princípios da Química Verde. Os métodos propostos neste estudo foram espectroscopia de reflectância difusa, espectrofotometria e sistemas em fluxo, empregando análise por injeção em fluxo (FIA) e multi-bombas (MPFS), com detecção na região do UV-Vis. Os métodos de análise propostos são baseados na reação entre glifosato e p-dimetilaminocinamaldeído (p- DAC), em meio acidificado, com um máximo de reflecção ou absorção em 495 nm. Após a otimização das condições experimentais e validação dos métodos propostos, através de parâmetros como linearidade da curva analítica, exatidão, precisão, limite de detecção, limite de quantificação, recuperação e estudos de possíveis íons interferentes, estes foram aplicados em amostras de herbicidas comerciais e águas (naturais e de consumo humano). Os resultados obtidos na determinação de glifosato nas amostras de herbicidas comerciais empregando reflectância difusa concordaram com os resultados obtidos empregando análise por injeção em fluxo, os quais apresentaram teores de 378,8 g L-1 para a amostra A, 392,4 g L-1 para a amostra... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The commercial product Roundup®, containing the glyphosate as its main active ingredient, is marketed worldwide because it is a nonsystemic, post-emergent and nonselective herbicide. Moreover, the high efficiency in the process of the removal of unwanted plants and the increase in the introduction transgenic plants favor their extensive use. Although it has not been considered a serious contaminant to humans the control and monitoring of this herbicide are very importants. The present project proposes the development of screening systems and clear analytical methods that can be applied to determine the presence of glyphosate, since in the literature there are few methods of analysis that apply Green Chemistry's principles. The proposed methods in this study were diffuse reflectance spectroscopy, spectrophotometry and flow systems, employing flow injection analysis (FIA) and multi-pumping (MPFS), with detection in the Uv-vis region. The proposed analysis methods are based in the reaction between glyphosate and p-dimethylaminocinnamaldehyde (p-DAC), in acid medium, it presents a reflection or absorption maximum in 495 nm. After the optimization of the experimental conditions and validation of the proposed methods, through parameters such as: linearity of the analytical curve, accuracy, precision, limit of detection, limit of quantification, recovery and study of possible interference ions, these were applied to commercial herbicides and water samples (naturals and for human consumption). The results obtained in the determination of glyphosate in the commercial herbicides employing diffuse reflectance were agree with the results obtained by employing flow injection analysis, which presented levels of 378.8 g L-1 to the A sample, 392.4 g L-1 to the B sample and 330.6 g L-1 to the C sample... (Complete abstract click electronic access below) / Orientador: Helena Redigolo Pezza / Coorientador: Leonardo Pezza / Banca: Ademir dos Santos / Banca: Matthieu Tubino / Banca: Carlos Roberto Bellato / Banca: Graziella Ciaramella Moita / Doutor

The decomposition behavior of several mining reagents (i.e., xanthate, dithiocarbamate, dithiophosphate and dithiophosphinate) used widely in mineral processing operations was studied. Decomposition has been reported to generate toxic compounds such as CS₂ (carbon disulfide) and COS (carbonyl sulfide), causing severe concerns to SHE (safety, health and environment). With the global trend of becoming sustainable/green and the increasingly strict regulations, the mining industry is facing an unprecedented pressure to handle the problematic reagents that can lead to the adverse impacts. Unfortunately, the interests of the prior research are biased on the performance of the reagents to optimize the efficiency and lower the cost, while the examination of the decomposition behavior is almost neglected. Under the circumstance of poor endeavor found in the prior investigations, the knowledge gap awaits to be filled in a systematic and integrated manner to recommend countermeasures for those problematic reagents. It can be seen from those fragmented studies collected from literature that only a limited understanding of thermal or aqueous decomposition behavior is achieved. It is far from sufficient for industrial guidance of mitigation. One key reason is the lack of robust methods to investigate decomposition under various conditions that are interesting to the mining companies (e.g., the flotation conditions). Consequently, the method development has always been considered of the utmost importance upon the start of this work to align with our overall goal of understanding the decomposition behavior under the various conditions. Three methods under a consistent strategy were designed to examine the decomposition under three conditions from Simple (in aqueous solutions alone), to Complex (in ore pulp under flotation conditions), to Specific (in solution containing metal ions). These three conditions were chosen based on the general interests from several prominent mining companies (Vale, Barrick, Freeport McMoRan and Newmont) to understand the decomposition mechanism and kinetics. The Simple is to serve as control for all other conditions. Besides, most of the prior studies in the literature are only conducted for the Simple condition. Therefore, the Simple is to resolve all discrepancies and conflicts, and provide a relatively comprehensive summary of the decomposition under the control condition. The Complex puts decomposition in a new environment that has never been explored before: the ore pulp under the simulated batch flotation conditions. Conclusions drawn from this part provide the most practical guidance for industrial mitigation. The Specific goes after the Complex to thoroughly understand the effect of a specific factor on decomposition. The decomposition responding to the variation of a certain factor is followed within a closed system with the compositional changes measured in all phases. The integrated analysis enables the correlation of the decomposition behavior to its original causes, which are the interactions of the reagent with other components in the system. Through the systematic investigation of decomposition of various reagents under various conditions, it is concluded that decomposition depends heavily on those parallel or sequential interactions that occur along with the decomposition reaction. For example, the decomposition reaction of xanthate throughout our entire study is regarded as ROCS₂⁻→CS₂. When xanthate forms xanthic acid, monothiocarbanate or dixanthogen with the change of pH, its breakup into CS₂ is altered. When xanthate interacts with Cu²⁺ forming Cu₂X₂, decomposition is depressed, but with Fe³⁺ forming FeX₃ decomposition is promoted. The CS₂ generated from decomposition could interact with OH- to form CS₃²⁻ or dissolve in solution or adsorb on minerals, leading to the decrease of CS₂ detected. The bonding properties between the –CS₂ moiety and other atoms or radicals in the molecule affect the stability of the reagents and the subsequent decomposition. The necessity to include a list of the side-interactions as complete as possible is key to understand and predict the decomposition behavior. With experimental efforts taken to develop methodologies to measure the decomposition under various conditions, the attempt to model the decomposition behavior is also initiated in this work. Based on the conclusions from experimental results, major components determining the output of the final decomposition products are identified. Unsurprisingly, the decomposition reaction together with its parallel and sequential interactions is critical. Simulation using Matlab to assess the decomposition of a simplified system containing SIBX and Cu²⁺ ions has achieved preliminary success by matching well with the experimental measurements. This establishes the groundwork for furthering the simulation of more complex systems and model development. Reagents decompose differently, although they might be applied to function similarly during an operation. As flotation collectors used for sulfide ore beneficiation, dithiocarbamate and xanthate possess some similarities in the decomposition in terms of generating CS₂. Their decomposition also decreases with the chain length. On the other hand, the decomposition of dithiophosphate and dithiophosphinate are different as the breakup of the molecule is mainly at their alkyl chain to generate moieties such as olefins. Compared to the studies carried out to understand the performance of the reagents when being used, research on decomposition requires more attention. Therefore, derivative work can be conducted based on results achieved in this work. For example, it is useful to further examine how reagents decompose after adsorbing on the mineral surfaces. It complements the knowledge to thoroughly understand decomposition at different spots within a complex system. The chemical fate studies of mining reagents with respect to the understanding the decomposition open up the window of developing methodologies to examine adverse behaviors. The experimental setups are applicable to simulate various conditions under which the reagent is being used and generating the adverse impacts. The strategy of analyzing decomposition within a complex system as shown in this study also provides insight into systematically investigating the other types of adverse behaviors.

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The use of standard soil tests to assess waste materials has become a common practice in waste management. However, the suitability of using standard soil tests on waste materials is questionable. Therefore, this investigation was undertaken to compare commonly used chemical extraction methods for their ability to extract elements from soil, waste, and soil-waste mixtures. This was carried out by: · Assessing the effects of extraction time on the extractability of Al,Ca, Co, Cu, Fe, Mg, Mn, Ni, Pb, S, Si, and Zn; · Assessing the comparability between single and sequential extraction. Two manganese rich wastes namely electro-winning waste (EW) and silicate-rich smelter slag (SS) and an acid soil (Inanda, Ia) were used for this study. Waste amended soils were obtained by incubating the EW and SS with Ia soil at field capacity at a rate of 20 g kg-1 and 120 g kg-1 soil respectively, and were sampled at day 0, 7, 28, 56, and 140. The effect of extraction time was assessed on the EW, SS, and Ia soil with carbonated water used in the acid rain test conducted at 16, 20, 30, and 50 hours. The equilibration time was different for different materials and elements. The concentration of Al and Zn did not change appreciably with increasing extraction time in the EW. Similar results were found for Mg, S, and Si in the SS and S in the Ia soil. This was attributed to ‘equilibrium’ being reached before 16 hours. The equilibration time of 20 hours which would release the exchangeable and specifically adsorbed elements was obtained for Co, Mg, Si, S, and Mn in the EW. The concentration of Ca decreased with extraction time in the EW and was attributed to readsorption. The concentration of Ca and Mn in the SS and Al, Fe, and Si in the Ia soil increased with extraction time and the ‘equilibrium’ was not reached even after 50 hours. This was attributed to the release of elements due to dissolution of minerals. In the comparison between Community Bureau of Reference (BCR) sequential and batch extraction, the concentrations of Ca, Co, Mg, Mn, and S were higher in batch extraction than in sequential extraction, particularly for the EW and the EW treated soils. This was possibly caused by the readsorption of released elements during water extraction. On the contrary, sequential extraction had higher concentration of Al and Fe compared to batch extraction for the EW, Ia soil, SS treated soils, and EW treated soils. These were attributed to a continued desorption of elements and dissolution of minerals due to exposed surfaces which occurs in sequential extraction. The comparison between single and sequential extraction for the BCR sequential extraction showed that hydroxylammonium chloride (HAC) applied in sequential extraction had higher concentration of Al, Co, Fe, Pb, and Zn than the single HAC extraction. This was probably due to incomplete dissolution of minerals, precipitation of amorphous minerals, and readsorption of released elements occurring for a single HAC extraction. These were minimised for hydrogen peroxide (H2O2) extraction and hence comparability between single and sequential H2O2 extraction was observed. This was probably due to the presence of complexing agent in the extracting reagent which would minimise the formation of secondary precipitates and hence, improved dissolution of minerals was obtained. Similarly, the concentrations of elements were comparable between single and sequential aqua regia extraction. These results indicated that comparability is improved between single and sequential extraction when aggressive conditions are used. The results from this investigation indicated that when chemical extraction methods are applied to wastes, the effects of the waste properties on the results of extraction need to be well understood. Consequently, when the chemical extraction methods are used in waste management scenarios certain modifications might have to be made. These modifications include the use of a high solution:solid ratio and an extracting solution which has high complexing ability / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2010.

Thesis (Ph. D.)--University of Hong Kong, 2008. / Also available in print.

Thesis (doctoral)--Rijksuniversiteit te Utrecht, 1983. / Summary in English. Spine title: Allenylmetaal-reagentia en hun omzetting in allenen, allynen en enige heterocycli. Additional references inserted. Description based on print version record. Includes vita and bibliographies.