CAPES / A indústria têxtil brasileira ocupa um importante papel na economia e se posiciona entre as 10 maiores produtoras mundiais. Seus efluentes, gerados no processo de tingimento dos tecidos, contém cargas de 15 a 50% de corantes, além de outros contaminantes. Com vistas à remediação ambiental destes efluentes, o resíduo do processamento dos fios de algodão (RA), que é coletado na própria unidade fabril, revelou-se um material atraente para a remoção de corantes após sua derivatização química com ácido monocloroacético (AMCA) ou cloreto dietilaminoetil.cloridrato (DEAE+reagente), obtendo matrizes iônicas do tipo carboximetil-RA (CM--RA) e dietilaminoetil-RA (DEAE+-RA), respectivamente. Estas matrizes foram obtidas através de delineamentos experimentais, sendo que para a CM--RA foram avaliados os fatores: a) concentração de NaOH; b) volume de isopropanol e c) quantidade de AMCA, enquanto que para a DEAE+-RA, os fatores foram: a) concentração de NaOH e b) quantidade de DEAE-reagente. Tais matrizes foram ensaiadas, respectivamente, quanto à eficiência na retenção de corantes: catiônico, C.I. Basic Blue 41 (BB 41) e aniônico, C.I. Reactive Red 239 (RR 239), em experimentos em coluna e batelada. Também foi avaliada a biodegradabilidade desses materiais utilizando enzimas celulolíticas. Para as melhores matrizes obtidas foram realizados experimentos adicionais quanto à eficiência de retenção dos corantes (concentração inicial, tempo de contato e adição de sais), a biodegradabilidade após a retenção dos corantes e o ensaio de regeneração das matrizes. Para a CM--RA, a eficiência de captação de corante catiônico foi predominantemente determinada pela concentração de álcali. A inclusão do maior volume de isopropanol resultou em incremento da eficiência, entretanto, com custo adicional não justificável. A melhor matriz obtida na ausência de isopropanol apresentou valores de retenção para os testes em coluna e batelada maior que um produto comercial do tipo carboximetilcelulose. Para o teste de biodegradabilidade, as amostras derivatizadas tiveram hidrólises próximas aos controles com adição de NaOH. Para o DEAE+-RA, a principal variável responsável pela eficiência da retenção de corantes foi a quantidade do derivatizante, sendo que nos ensaios em coluna e batelada a resposta foi semelhante ao obtido com um produto comercial DEAE-Celulose. Através do teste de biodegradabilidade observou-se que a derivatização reduziu a porcentagem de hidrólise quando comparada aos seus controles com NaOH. Para as melhores matrizes, o ensaio de concentração inicial de corantes indicou que a retenção é maior com o aumento da concentração. Quanto à adição de NaCl, houve redução da retenção de corante na matriz carboximetilada enquanto para a dietilaminoetilada a influência foi positiva acima de 50 mM. A presença de corante reduziu em 4,10 e 37,36 % a hidrólise das matrizes carboximetilada e dietilaminoetilada, respectivamente. No presente trabalho, os derivados CM--RA e DEAE+-RA se revelaram eficientes para a remoção dos corantes BB 41 e RR 239, respectivamente, podendo assim se apresentar como uma alternativa no tratamento de efluentes têxteis. / The Brazilian textile industry occupies an important role in the economy and ranks among the 10 largest world producers The effluents generated in the process of fabrics dyeing contain 15 to 50% of dyes and others contaminants. With a view to environmental remediation of these effluents, the processing of cotton yarn waste (cotton dust waste - CDW) that is collected in the plant itself, proved to be an attractive material for the removal of the residual dyes effluents after the chemical derivatization with monochloroacetic acid (MCAA) or diethylaminoethyl chloride.hydrochloride (DEAE+reagent), thus originating matrices carboxymethyl- CDW (CM--CDW) and diethylaminoethyl-CDW (DEAE+-CDW), respectively. These matrices were obtained using experimental designs, when for CM--CDW three factors were evaluated: a) concentration of NaOH; b) volume of isopropanol and c) amount of MCAA, while for DEAE+-CDW, the factors were: a) concentration of NaOH and b) amount of DEAE+reagent. These matrices were tested for their effectiveness in the retention of dyes: the cationic, C. I. Basic Blue 41 (BB 41) and the anionic, C. I. Reactive Red 239 (RR 239), both in column and batch experiments. Also, the biodegradability of these materials was tested. For the best matrices obtained, additional experiments regarding the retention efficiency of the dyes (initial concentration, contact time and addition of salts) and matrices biodegradability after the dye retention were also carried out. For the CM--CDW, the efficiency of uptake of the cationic dye was predominantly determined by the concentration of alkali. The inclusion of the higher volume of isopropanol in the pretreatment step resulted in improved efficiency, but with an additional cost not justifiable. The best matrix obtained in the absence of isopropanol showed retention values for column and batch experiments with respective efficiencies of 3.9 and 2 times higher than a commercial CM-cellulose. For the biodegradability test, the samples of experimental design showed close enzymatic hydrolysis compared with the controls with alkali. For the DEAE+-CDW, the main variable for the efficiency of dye retention is predominantly determined by the amount of DEAE+reagent. The maximum retention of the anionic dye was obtained in columns while the batch alternatve performance was close to that of a commercial DEAE-Cellulose. The biodegradability test revealed that the derivatization with DEAE+reagent reduced the percentage of hydrolysis by cellulases when compared to the controls with NaOH. The initial concentration test of dye indicated that the retention increases with increased dye concentration and contact time to reach equilibrium which was higher in the higher concentrations in both matrices. The addition of NaCl decreased the dye retention for the carboxymethylated matrix and for the diethylaminoethylizated matrix the influence was positive only after addition of 50 mM. The presence of dye in the matrices derivatized reduced the hydrolysis in 4.10 and 37.36 % for carboxymethylated and diethylaminoethylizated matrices, respectively. Therefore, the CM--CDW and DEAE+- CDW derivatives of CDW proved effective for the removal of the dyes BB 41 and RR 239, respectively, and thus both represent important alternatives in the treatment of colored textile effluents.

CAPES; Fundação Araucária / A caulinita é um argilomineral empregado em diversos setores industriais e, em decorrência da elevada disponibilidades na crosta terrestre são realizadas modificações químicas para a obtenção de diferentes estruturas do material buscando ampliar sua utilização. Foram realizadas ativações com ácidos fosfórico e sulfúrico nas concentrações de 5 e 10 mol L-1, e tratamentos térmicos em 850, 1100 e 1200 ºC visando a aplicação deste argilomineral na adsorção do corante têxtil Reactive Blue 203. As amostras foram caracterizadas por Difratometria de Raios X (DRX), Espectroscopia na Região do Infravermelho com Transformada de Fourier (FTIR), Análise Termogravimétrica (TGA), Análise Térmica Diferencial (DTA) e Microscopia Eletrônica de Varredura (MEV). Nos espectros de FTIR das amostras calcinadas houve o desaparecimento das absorções características da hidroxila, além do surgimento de vibrações atribuídas a metacaulinita, que é formada a partir da calcinação da caulinita. Pelo DRX foi possível confirmar as alterações da estrutura, pois o difratograma apresentou característica de material amorfo quando calcinado em 850 °C, enquanto que nas temperaturas de 1100 e 1200 °C o material voltou a apresentar estrutura cristalina, devido a formação da mulita. Essas modificações também são evidentes na análise térmica, sendo que o evento ocorrido na curva termogravimétrica entre 420 ºC e 700 ºC refere-se à desidroxilação do material e consequentemente, à formação da metacaulinita. Já a análise térmica diferencial apresentou um pico exotérmico na região de 1000 ºC, correspondendo à conversão da metacaulinita em mulita. Entretanto, a análise de MEV não demonstrou mudanças na morfologia do material. O ponto de carga zero obtido para a caulinita foi de 4,41, correspondendo ao valor de pH em que a carga superficial é zero, sendo que em valores de pH superiores a este a caulinita estará mais propícia a adsorver substâncias catiônicas e em valores de pH inferiores, aniônicas. A caulinita apresentou maior quantidade de sítios ácidos, uma vez que ambas as análises resultaram em valores de pH inferiores a 7, característicos de argilominerais com estrutura lamelar, devido a presença das hidroxilas internas e do alumínio, uma vez que trata-se de um aluminossilicato. No teste de adsorção com o corante têxtil Reactive Blue 203 a caulinita sem tratamento se sobressaiu perante as demais amostras, com melhor ajuste da isoterma de Sips e cinética de pseudo-segunda ordem. Os parâmetros termodinâmicos indicam que se trata de um processo espontâneo e endotérmico e evidenciam que ocorre uma adsorção química. / The kaolinite is a clay mineral used in several industrial sectors and, due to the high availability in the earth's crust, chemical modifications are made to obtain different structures of the material in order to expand its use. Activations were carried out with phosphoric and sulfuric acids at concentrations of 5 and 10 mol L-1, and thermal treatments at 850, 1100 and 1200ºC for the application of this clay in the adsorption of Reactive Blue 203 textile dye. The samples were characterized by X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric Analysis (TGA), Differential Thermal Analysis (DTA) and Scanning Electron Microscopy (SEM). In the FTIR spectra of the calcined samples, the characteristic hydroxyl absorptions disappeared, as well as the appearance of vibrations attributed to metacaulinite, which is formed from calcination of kaolinite. By XRD, it was possible to confirm the changes in the structure, since the diffractogram showed a characteristic of amorphous material when calcined at 850 °C, while in the temperatures of 1100 and 1200 °C the material returned to present crystalline structure, due to the formation of the mullite. These changes are also evident in the thermal analysis, and the event occurring in the thermogravimetric curve between 420 ºC and 700 ºC refers to the dehydroxylation of the material and, consequently, to the formation of metakaolin. The differential thermal analysis showed an exothermic peak in the region of 1000 ºC, corresponding to the conversion of metacaulinite to mullite. However, SEM analysis did not show changes in material morphology. The zero charge point obtained for kaolinite was 4.41, corresponding to the pH value at which the surface charge is zero, and at pH values higher than that kaolinite will be more propitious to adsorb cationic substances and in values of pH lower, anionic. The kaolinite presented higher amount of acidic sites, since both analyzes resulted in pH values lower than 7, characteristic of clay minerals with lamellar structure, due to the presence of internal hydroxyls and aluminum, since it is an aluminosilicate. In the adsorption test with the Reactive Blue 203 textile dye, the untreated kaolinite stood out in the other samples, with better adjustment of the Sips isotherm and pseudo second order kinetics. The thermodynamic parameters indicate that it is a spontaneous and endothermic process and evidence that a chemical adsorption occurs.

CAPES / A indústria têxtil brasileira ocupa um importante papel na economia e se posiciona entre as 10 maiores produtoras mundiais. Seus efluentes, gerados no processo de tingimento dos tecidos, contém cargas de 15 a 50% de corantes, além de outros contaminantes. Com vistas à remediação ambiental destes efluentes, o resíduo do processamento dos fios de algodão (RA), que é coletado na própria unidade fabril, revelou-se um material atraente para a remoção de corantes após sua derivatização química com ácido monocloroacético (AMCA) ou cloreto dietilaminoetil.cloridrato (DEAE+reagente), obtendo matrizes iônicas do tipo carboximetil-RA (CM--RA) e dietilaminoetil-RA (DEAE+-RA), respectivamente. Estas matrizes foram obtidas através de delineamentos experimentais, sendo que para a CM--RA foram avaliados os fatores: a) concentração de NaOH; b) volume de isopropanol e c) quantidade de AMCA, enquanto que para a DEAE+-RA, os fatores foram: a) concentração de NaOH e b) quantidade de DEAE-reagente. Tais matrizes foram ensaiadas, respectivamente, quanto à eficiência na retenção de corantes: catiônico, C.I. Basic Blue 41 (BB 41) e aniônico, C.I. Reactive Red 239 (RR 239), em experimentos em coluna e batelada. Também foi avaliada a biodegradabilidade desses materiais utilizando enzimas celulolíticas. Para as melhores matrizes obtidas foram realizados experimentos adicionais quanto à eficiência de retenção dos corantes (concentração inicial, tempo de contato e adição de sais), a biodegradabilidade após a retenção dos corantes e o ensaio de regeneração das matrizes. Para a CM--RA, a eficiência de captação de corante catiônico foi predominantemente determinada pela concentração de álcali. A inclusão do maior volume de isopropanol resultou em incremento da eficiência, entretanto, com custo adicional não justificável. A melhor matriz obtida na ausência de isopropanol apresentou valores de retenção para os testes em coluna e batelada maior que um produto comercial do tipo carboximetilcelulose. Para o teste de biodegradabilidade, as amostras derivatizadas tiveram hidrólises próximas aos controles com adição de NaOH. Para o DEAE+-RA, a principal variável responsável pela eficiência da retenção de corantes foi a quantidade do derivatizante, sendo que nos ensaios em coluna e batelada a resposta foi semelhante ao obtido com um produto comercial DEAE-Celulose. Através do teste de biodegradabilidade observou-se que a derivatização reduziu a porcentagem de hidrólise quando comparada aos seus controles com NaOH. Para as melhores matrizes, o ensaio de concentração inicial de corantes indicou que a retenção é maior com o aumento da concentração. Quanto à adição de NaCl, houve redução da retenção de corante na matriz carboximetilada enquanto para a dietilaminoetilada a influência foi positiva acima de 50 mM. A presença de corante reduziu em 4,10 e 37,36 % a hidrólise das matrizes carboximetilada e dietilaminoetilada, respectivamente. No presente trabalho, os derivados CM--RA e DEAE+-RA se revelaram eficientes para a remoção dos corantes BB 41 e RR 239, respectivamente, podendo assim se apresentar como uma alternativa no tratamento de efluentes têxteis. / The Brazilian textile industry occupies an important role in the economy and ranks among the 10 largest world producers The effluents generated in the process of fabrics dyeing contain 15 to 50% of dyes and others contaminants. With a view to environmental remediation of these effluents, the processing of cotton yarn waste (cotton dust waste - CDW) that is collected in the plant itself, proved to be an attractive material for the removal of the residual dyes effluents after the chemical derivatization with monochloroacetic acid (MCAA) or diethylaminoethyl chloride.hydrochloride (DEAE+reagent), thus originating matrices carboxymethyl- CDW (CM--CDW) and diethylaminoethyl-CDW (DEAE+-CDW), respectively. These matrices were obtained using experimental designs, when for CM--CDW three factors were evaluated: a) concentration of NaOH; b) volume of isopropanol and c) amount of MCAA, while for DEAE+-CDW, the factors were: a) concentration of NaOH and b) amount of DEAE+reagent. These matrices were tested for their effectiveness in the retention of dyes: the cationic, C. I. Basic Blue 41 (BB 41) and the anionic, C. I. Reactive Red 239 (RR 239), both in column and batch experiments. Also, the biodegradability of these materials was tested. For the best matrices obtained, additional experiments regarding the retention efficiency of the dyes (initial concentration, contact time and addition of salts) and matrices biodegradability after the dye retention were also carried out. For the CM--CDW, the efficiency of uptake of the cationic dye was predominantly determined by the concentration of alkali. The inclusion of the higher volume of isopropanol in the pretreatment step resulted in improved efficiency, but with an additional cost not justifiable. The best matrix obtained in the absence of isopropanol showed retention values for column and batch experiments with respective efficiencies of 3.9 and 2 times higher than a commercial CM-cellulose. For the biodegradability test, the samples of experimental design showed close enzymatic hydrolysis compared with the controls with alkali. For the DEAE+-CDW, the main variable for the efficiency of dye retention is predominantly determined by the amount of DEAE+reagent. The maximum retention of the anionic dye was obtained in columns while the batch alternatve performance was close to that of a commercial DEAE-Cellulose. The biodegradability test revealed that the derivatization with DEAE+reagent reduced the percentage of hydrolysis by cellulases when compared to the controls with NaOH. The initial concentration test of dye indicated that the retention increases with increased dye concentration and contact time to reach equilibrium which was higher in the higher concentrations in both matrices. The addition of NaCl decreased the dye retention for the carboxymethylated matrix and for the diethylaminoethylizated matrix the influence was positive only after addition of 50 mM. The presence of dye in the matrices derivatized reduced the hydrolysis in 4.10 and 37.36 % for carboxymethylated and diethylaminoethylizated matrices, respectively. Therefore, the CM--CDW and DEAE+- CDW derivatives of CDW proved effective for the removal of the dyes BB 41 and RR 239, respectively, and thus both represent important alternatives in the treatment of colored textile effluents.

Rural people around the 4 km2 Orathupalayam Dam in southern India live in one of India’s most polluted areas. The people were once restricted mainly by scarcity of water but today they cannot drink their well water or cultivate their soil. The dam, created to store floodwater from the Noyyal River, also stores effluent water from the more than 700 dyeing and bleaching industries situated in the town of Tiruppur, 20 km upstream. Although most industries have treatment plants they do not treat total dissolved solids (TDS) and thus NaCl becomes one of the major components of the effluent. 75 to 100 million litres of effluents are released every day. Through water sampling in open and bore wells, and with the help of GPS, ArcView and Surfer it could be concluded that high TDS levels and concentrations of Cl-, Ca2+, Mg2+ and Na+ were associated with the dam. A definite spatial pattern of the spreading of polluted water could be determined. Water from the dam was fed to the ground water all around the dam and also affected the groundwater more than 4 km to the southeast. Soil samples and interviews with farmers made it clear that land irrigated with dam water or affected well water soon became uncultivable. The water destroyed the soil structure and seeds did not germinate after irrigation with polluted water. Through interviews it could be concluded that the local people around the dam paid a large part of the externalities of the polluting activities of the textile industries in terms of negative health effects and lost agricultural land, water resources, fishing and working opportunities. These problems have mostly been caused by the high salt concentration in the effluents but it is unclear to what extent other substances have caused or might cause harmful effects to the environment, people and animals.

In recent years, environmental authorities in Sweden are reporting about high content of antimony in waste water that is discharging from polyester textile dyeing industries. It is known from available scientific publications that, antimony and its compound is harmful for both human and environment. While dyeing of polyester textiles have a commercial importance and in regards to the environmental issues, the industries are looking for the factors those results in high concentrations of antimony in their dyeing waste water. Dyeing of polyester textile requires high-temperature application in association with dyes and process aid chemicals. The waste water that is being produced after dyeing contains a complex mixture of chemicals, where antimony is one of that mixture. To comply with the industries interest, this master thesis work involved the exhaust dyeing of polyester fabrics/yarns and analyzing the dyeing waste water, to determine the amount of antimony diffusion. According to literature studies, the antimony compounds are widely used as catalyst for polyethylene terepthalate (PET) polymerization and hence antimony is present in polyester textiles. The entire experimental work intended to understand the variation of antimony concentration and the factors that are causing high antimony diffusion from polyester textiles during dyeing. The materials which are polyester yarn and fabrics were collected from 3 different dyeing industries of Sweden and the materials were in 9 different types. From material analysis (before dyeing) it has been found there were variations in antimony concentration among the materials. The process parameters that have varied during exhaust dyeing were dyeing temperature, cycle time and process aid chemical (leveling agent) adding options. With the variation in process parameters, the dyeing has performed and the dyeing waste waters have analyzed through inductively coupled plasma sector field mass spectroscopy (ICP-SFMS). The expectations from the experiments were, under specific dyeing process and with same antimony concentration, the materials varying in filament/fiber diameter; big diameter filament/fiber will diffuse less antimony compared to the small diameter filaments. Also, process-wise the antimony diffusion ratio among the materials will accordingly follow the Fick’s diffusion model. To face the environmental issues with sustainability, entire thesis work could provide concentrated knowledge’s with literature evidence for the dyeing industries. As literature study indicates, the dyeing temperature, temperature ramp set and cycle time play major factor while comparing for the expected diffusion ratio. As a gentle process parameter, comparatively lower temperature and cycle time results lower antimony diffusion. The use of levelling agent could be reduced to a level with the appropriateness while added for dyeing. Also, a strong follow-up is needed in the supply chain, for lowering the initial antimony content in the materials. Overall, the findings of this thesis work also keep an importance to do further research on the polyester textile, as during the experiments most of the materials haven’t reacted accordingly as they were expected to react with the Fick’s diffusion model.

<p align="justify">Les laques de garance, les pigments artistiques dont les procédés de fabrication étaient souvent des secrets jalousement gardés, ont depuis longtemps éveillé l'intérêt des chimistes. Le premier mode opératoire de laque de garance décrit scientifiquement est dû à Marggrave en 1754, chimiste allemand célèbre surtout pour la découverte du sucre de betterave. L'élucidation de la structure chimique de l'alizarine par Graebe en 1868 est une des étapes fondatrices de la chimie organique. Il a ensuite vite été reconnu que, dans les laques, l'alizarine se trouve sous forme de complexes d'aluminium. Plusieurs structures ont été proposées dans la littérature pour les complexes d'alizarine et d'aluminium. Le site de complexation de l'aluminium y est constitué soit par les fonctions carbonyle en C-9 et phénolate en C-1 (site céto-phénolate), soit par les deux fonctions phénolates en C-1 et C-2 (site diphénolate).</p> <p><p align="justify">Nos résultats montrent que, au moins en solution aqueuse diluée et acide, le site de complexation est le céto-phénolate et la stoechiométrie 1:1. En solution plus concentrée et neutre ou légèrement basique, il peut également se former des complexes de stoechiométrie 1:2, dont la couleur est par ailleurs pratiquement identique à celle des complexes de stoechiométrie 1:1. Quand les réactifs sont mis en présence en rapport stoechiométrique et neutralisés par NaOH (aluminium:alizarine:NaOH 1:2:5), les complexes 1:2 ainsi formés peuvent même polymériser en formant entre eux des liaisons Al-O-Al. Cependant, dans la pratique de la préparation des laques, aujourd'hui comme dans le passé, l'aluminium est présent en large excès par rapport à l'alizarine. Dans ces conditions, les complexes, au lieu de polymériser, s'adsorbent à la surface des grains d'alumine formés par l'aluminium en excès. Nous n'avons trouvé aucune indication de la formation de complexes 2:4. Il est probable que de tels complexes ne sont, comme les gels que nous avons obtenus dans certaines conditions, que des cas particuliers, non représentatifs de la structure des laques réelles. La stoechiométrie des complexes et leur état physique ne seraient que des caractéristiques secondaires. Dans le cas des laques utilisées comme pigments, il s'agirait de complexes 1:2 et probablement aussi 1:1, adsorbés sur les grains d'alumine via des liaisons Al-O-Al.</p><p><p align="justify">La compétition entre ions H+ et Al3+ pour les phénolates est à la base de la libération des molécules d'alizarine dans les méthodes classiques d'extraction des colorants des laques par un acide pour leur analyse par HPLC. Nos résultats montrent que la concentration en ions H+ nécessaire pour libérer les colorants est proportionnelle à la concentration en ions Al3+ en solution. Dans la pratique, le pH nécessaire est très bas, ce qui a pour conséquence négative d'hydrolyser certaines des molécules colorantes constitutives des laques. L'addition d'ions F- permet de pallier ce problème. En formant des complexes avec les ions Al3+, les ions F- relèvent assez le pH minimum d'extraction pour éviter l'hydrolyse des colorants moins stables (glycosides, pseudopurpurine.), et donnent de plus des rendements d'extraction souvent meilleurs que ceux obtenus avec les autres acides (HCl, H2SO4, TFA). L'addition d'ions Li+, qui par leur petite taille peuvent plus facilement se glisser à l'intérieur des complexes, et d'agents chélatants tels que le DFOM, qui contribuent à capter les ions Al3+, améliore encore l'extraction des colorants. </p><p><p align="justify">Des propriétés telles la granulométrie, la porosité et l'hygroscopicité des laques sont celles de l'alumine qui constitue leur substrat. Les analyses de différentes laques d'extraits de Rubiacées montrent :<p>- la présence fréquente de pseudopurpurine et de glycosides; ces colorants ne sont détectés qu'après extraction à pH ~ 2 (extraction par HF), parce qu'à pH plus acide ils sont hydrolysés.<p>- la teneur en différents colorants est influencée non seulement par l'espèce de plante, mais aussi par le mode de préparation des laques. </p><p><p align="justify">La couleur apparente et les spectres dans le visible des chélates aluminium-anthraquinone sont bien distincts de ceux des mêmes colorants en l'absence d'aluminium. Les paramètres L*a*b* et leur équivalent en coordonnées cylindriques L*c*h*, calculés à partir des spectres de réflectance, permettent de caractériser la couleur des objets, telle qu'elle serait perçue sous une lumière de spectre donné et par un "observateur de référence". On constate que la teinte des laques dépend surtout de la nature des colorants présents sous forme de chélates d'aluminium. La saturation dépend surtout du rapport aluminium/colorant, et augmente avec celui-ci, ce qu'on peut attribuer à un meilleur rendement de la formation de complexes quand l'aluminium est présent en plus large excès.</p> <p><p align="justify">Pour mieux comprendre les facteurs affectant la permanence des laques, une approche est de soumettre des laques préparées dans des conditions connues à des tests de vieillissement accéléré par une lampe à arc de xénon. Une première étude de ce type menée sur des laques sous forme de poudres fixées sur des filtres montre que dans les laques fort concentrées au départ, la majorité des colorants peut être dégradée sans que la couleur perceptible ait fort changé. A l'observation au microscope, on constate que les grains les plus petits ont tendance à décolorer plus vite. Cependant globalement le principal facteur affectant l'évolution de la couleur est la concentration en colorants. Il semble donc que les complexes de colorants adsorbés à la surface de la porosité interne des grains d'alumine soient protégés de la lumière par les complexes adsorbés dans les couches plus externes, et que cette protection soit proportionnelle à la concentration en colorant. La photodégradation est probablement oxydative. Elle est d'ailleurs beaucoup plus lente pour les teintures d'alizarine sur laine, grâce probablement aux propriétés réductrices de la laine. Il faut donc s'attendre à ce que, dans les polychromies, la présence des liants ralentisse le vieillissement en limitant la diffusion de l'oxygène, ce qui n'était pas le cas dans nos laques poreuses vieillies au contact de l'air. C'est là un des aspects que la suite des études de vieillissement accéléré devrait tenter d'éclaircir.</p><p> / Doctorat en sciences appliquées / info:eu-repo/semantics/nonPublished

MENVSC / Department of Ecology and Resource Management / In this study, the efficacy of bentonite clay, pre-treated magnesite and their nanocomposite on the removal of Congo red dye from aqueous solution was explored. Batch experimental approach was a technique used to fulfil the goals of this study. A number of operational parameters were optimised, and they include effects of shaking time, adsorbent dosage, initial CR dye concentration, initial solution pH and temperature. Findings of the study revealed that the optimum conditions that are suitable for the removal of CR dye are 20 minutes, 0.5 g of dosage, 120 mg/L, 250 rpm, and pH = 7. This has achieved > 99% removal efficacy of CR dye for the nanocomposite and reduced it to below the South African National Standard (SANS) 241 water quality specifications. Furthermore, kinetic studies revealed that bentonite clay, pre-treated magnesite, and their nanocomposite fitted very well to pseudo-second-order kinetics than pseudo-first-order kinetics. The regression analysis was observed to be 1, 0.9, and 0.9 for bentonite clay, pre-treated magnesite, and their nanocomposite respectively. Adsorption isotherms indicated that CR removal by bentonite clay, pre-treated magnesite, and their nanocomposite fitted well to Langmuir adsorption isotherm than the Freundlich adsorption isotherm hence indicating mono-layer adsorption. Thermodynamic values for CR removal were observed to be: ΔH0 (kJ mol-1) = 43.86, 30.67, and 24.88 for bentonite clay, pre-treated magnesite, and their nanocomposite respectively. This indicates that the reaction is endothermic. The positive ΔS0 (kJ mol-1 K-1) values for bentonite clay and 25 °C for pre-treated magnesite confirms that there is an increase in the degree of randomness at solid/solution interface during the removal of CR ions from aqueous solution. The negative values of ΔG0 (kJ mol-1) for 40 – 70 °C on bentonite and the entire range for the nanocomposite suggest the spontaneity and feasibility of CR adsorption whereas the positive ΔG0 (kJ mol-1) for bentonite clay suggest a non-spontaneous nature of adsorption. As such, pre-treated magnesite/bentonite clay nanocomposite demonstrated superior adsorption capacity in relation to individual materials and other materials reported in literature. / NRF

PhD (Physics) / Department of Physics / Dye sensitized solar cells (DSSCs) have attracted rapid interest over the recent years with prospect of emerging as a viable alternative to conventional silicon based solar cells. The photoanode of DSSCs comprises of dye molecules anchored to the surface of semiconductors such as TiO2. However, the major drawback of Titanium dioxide (TiO2) is its wide band gap (3.0 eV to 3.2 eV) which limits its photocatalytic activities to the ultraviolet region of the electromagnetic spectrum. Understanding the interaction of dye molecules with the surfaces of TiO2 is crucial for optimizing light-harvesting, photoconversion function and photocurrent densities in DSSCs. The three polymorphs of TiO2 are anatase, brookite and rutile. The optical properties of brookite semiconductor have not been much studied although brookite has been reported to have good photocatalytic properties. In this work, Density functional theory (DFT) computational approach was used through various computational softwares which are CASTEP, GAUSSIAN, GAUSSUM, GPAW, ASE, and AVOGADRO with B3LYP, LANL2DZ, PBE, and GGA functional to explore the photocatalytic properties of the typical ruthenium N3 complex, polyenediphenyl-aniline dye moiety, croconate dye molecules and three modelled surfaces of brookite which are (TiO2)5, (TiO2)8 and (TiO2) 68 for application in DSSCs. We also studied the absorption of the corresponding dye molecules on the three surfaces of brookite TiO2. Our findings showed strong binding ability, good electronic coupling, efficient charge separation, spontaneous electron injection and good spectral properties upon adsorption of the dye molecules to brookite TiO2 semiconductor clusters. Our findings on the optical absorption spectra of ruthenium N3 dye, croconate dye and polyenediphenyl-aniline dye molecule absorbed on (TiO2)5 and (TiO2)8 brookite cluster shows bathocromatic shift of the absorption maxima to higher wavelength and improve optical response of TiO2 brookite cluster. A red spectra shift and absorption over a wide range of the solar spectrum in the visible and near infra-red region of the solar spectrum was achieved upon absorption of the ruthenium N3 complex and polyenediphenyl-aniline dye molecules on (TiO2)5 and (TiO2)8 brookite cluster. The results generally suggest that the absorption of dye molecules on TiO2 brookite cluster improves its spectra responsivity in the UV region and makes it possible to absorb over the whole spectrum range, that is, the UV, visible and near infra – red region of the solar spectrum. Our findings also showed good electron injection kinetics from the dye to TiO2 brookite clusters, which suggests higher photocurrents density and open circuit voltage in DSSCs. / NRF

Bei der postmortalen Befunderhebung an Zähnen im Rahmen der Identifikation unbekannter Leichen besteht die Möglichkeit, dass zahnfarbene Füllungen übersehen oder fehlgedeutet werden. Daraus entstehende Diskrepanzen zu den antemortalen Daten können zu Problemen bei der Identifikation führen. Ziel der Ar-beit war daher die Ermittlung einer zuverlässigen und praxistauglichen Methode zum sicheren Erkennen von zahnfarbenen Zahnfüllungen bei der postmortalen Befunderhebung. Dazu wurden 50 menschliche Zähne mit zahnfarbenen Füllungen versorgt und mittels UV-Licht, digitaler IR-Fotografie, digitalem Röntgen, CT und einer Schmelzfärbemethode bezüglich der Erkennbarkeit der Füllungen untersucht. Die geeignetsten Methoden wurden zusätzlich anhand von Farbfotografien in Fragebögen beurteilt. Die Schmelzfärbemethode erwies sich als die genauste Methode, aber auch mit Hilfe der UV-Fluoreszenz konnten mit 97% nahezu alle Füllungen erkannt werden. Die Röntgendiagnostik ermöglichte das Erkennen von 80% der vorhandenen zahnfarbenen Füllungen. Das CT ist unzuverlässig und die Infrarot-Fotografie ist ungeeignet für diese Fragestellung. Im Ergebnis dieser Studie kann die verbesserte Schmelzfärbung als sicherste Me-thode zur postmortalen Identifikation von zahnfarbenen Füllungen empfohlen wer-den. Als zuverlässige und schnelle „Screening Methode“ ist die Untersuchung mittels UV-Fluoreszenz geeignet. Für den sicheren Einsatz der UV-Fluoreszenz in der Rechtsmedizin sollten die Fähigkeiten der Rechtsmediziner im Umgang mit dieser Methode anhand praktischer Übungen geschult werden.

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