Since the surfaces of cantaloupes are highly rough or irregular, Salmonella enteric and other bacteria can easily attach to these surfaces and are difficult to remove. Cetylpyridinium chloride (CPC) is the active ingredient of some antiseptic oral mouth rinses and has a broad antimicrobial spectrum with a rapid bactericidal effect on Gram-positive pathogens. Delmopinol hydrochloride (delmopinol) is a cationic surfactant that is effective for treating and preventing gingivitis and periodontitis. The application of delmopinol or CPC to cantaloupe surfaces may be an alternative post harvest technique to reduce the frequency and level of Salmonella contamination. Cantaloupe (Athena and Hale's Best Jumbo (HBJ) cultivars) rind plugs were inoculated with a broth culture of Salmonella Michigan. After 15 min, plugs were sprayed with 10 ml of a 1% delmopinol solution, or a CPC solution (0.5 or 1.0%) or distilled water (Control), and held at 37 oC for 1 hr or 24 hr. For additional samples, the chemical treatments were applied 15 min before pathogen inoculation. Melon plugs were submerged in Butterfield's Phosphate Buffer, shaken, sonicated and solutions were enumerated on Tryptic Soy Agar. The texture quality and color of additional melon samples were evaluated after delmopinol or CPC spray treatments and storage at 4 oC. A 1.0% application of CPC reduced Salmonella levels up to 2.34 log CFU/ml (Athena) and 4.95 log CFU/ml (HBJ) in comparison to the control (p<0.01). A 1.0% delmopinol treatment reduced Salmonella levels as much as 3.1 log CFU/ml in comparison to the control (p<0.01) on both cultivars. In general, the log recovery of Salmonella on cantaloupes treated with delmopinol or CPC solutions, after 1 hr storage, was significantly lower (p<0.05) than the recovery from control cantaloupes, but Salmonella recovery was not significantly different after 24 hr. No significant differences were observed in the texture and color of melons treated with delmopinol or CPC after 14 days. A surface spray application of delmopinol hydrochloride or cetylpyridinium chloride could be an alternative antimicrobial post-harvest treatment that could make cantaloupes surfaces more susceptible to sanitizers or enhance physical removal of bacteria. / Ph. D.

Neste trabalho foram obtidos filmes de óxido de tungstênio pelo método sol-gel modificado, tendo como precursor o tungstato de sódio dihidratado (Na2WO4.2H2O) e como agente estruturante o surfactante cloreto de dodeciltrimetilamônio (DTAC). O comportamento dos sistemas em meio aquoso foi avaliado por medidas de pH, condutividade e viscosidade. Foram avaliadas duas metodologias de obtenção dos filmes de óxido de tungstênio: a primeira consistiu na obtenção de filmes de tungstato de sódio, através de sistemas contendo 10 mmol.L-1 de Na2WO4.2H2O em diferentes concentrações de DTAC, por casting, e conversão do tungstato de sódio a óxido de tungstênio pela acidificação dos filmes; a segunda metodologia consistiu na conversão dos sistemas aquosos contendo 20 mmol.L-1 de Na2WO4.2H2O, em diferentes concentrações de DTAC, em ácido tungstico, obtenção dos filmes por spin coating e, calcinação em presença de ar. Os filmes foram obtidos em substratos de silício (100) recobertos com dióxido de silício e avaliados por Difração de Raios-X, Espectrometria de retroespalhamento Rutherford, Espectroscopia Raman, Microscopia Eletrônica de Varredura e ensaios fotocatalíticos. As alterações na concentração precursor e agente estruturante não afetaram significativamente o pH e a viscosidade dos sistemas precursores. A determinação da concentração micelar crítica (cmc) do DTAC, obtida através da condutividade, foi de 13 mmol.L-1 e 9,88 mmol.L-1 para os sistemas contendo 10 e 20 mmol.L-1 de Na2WO4.2H2O, respectivamente. Em ambas metodologias o produto final foi o óxido de tungstênio em forma de disco e placas. As espessuras dos filmes obtidos na primeira metodologia variaram de 4 a 5 μm e as estruturas tiveram diâmetros médios de 4,37 μm e 114 nm. Na segunda metodologia as espessuras foram de 0,5-1,0 μm e as estruturas obtidas tiveram diâmetros médios em torno de 95-103 nm. Os filmes obtidos apresentaram atividade fotocatalítica, uma vez que duplicaram a velocidade da reação de degradação do corante alaranjado de metila em relação ao sistema sem o filme. / In this work tungsten oxide films have been obtained bymodified sol-gel method, with sodium tungstate dehydrate (Na2WO4.2H2O) as the precursor and the cationic surfactant dodecyltrimethylammonium chloride (DTAC) as structuring agent.The behavior in aqueous media of precursor/structuring agent systems was characterized by pH, conductivity and viscosity measurements. Two methods for obtaining tungsten oxide films were evaluated: the first consisted in obtaining sodium tungstate films from the systems containing 10 mmol.L-1 of Na2WO4.2H2O at different DTAC concentrations, by casting, converting the sodium tungstate to tungsten oxide; the second method consisted in the conversion of the aqueous systems containing 20 mmol.L-1 of Na2WO4.2H2O at different DTAC concentrations to tungstic acid, obtaining the films by spin coating and, posteriorly, calcination in the presence of air. The films were obtained on silicon substrate (100) with a 50 nm layer of silicon dioxide and were characterized by X-ray diffraction, Rutherford backscattering spectrometry, Raman spectroscopy, Scanning Electron Microscopy and photocatalytic tests. The precursor concentration and structuring agent do not affect significantly the pH and the viscosity of the precursor systems in aqueous media.The values of critical micelle concentration (CMC) of DTAC, obtained by the conductivity, were of13 mmol.L-1 and 9,88 mmol.L-1, for the systems containing 10 and 20 mmol.L-1 de Na2WO4.2H2O, respectively.In both adopted methods the final product is the tungsten oxide, with nano and micrometric structures in the form of discs and plates. The thickness of the films obtained in the first method varied from 4 to 5 μm and the structures presented an average diameter around 4,37 μm and 114 nm. The thickness of the films obtained with the second methodvariedfrom0,5to 1 μm and the structures presented an average diameter from 95 to103 nm.The obtained tungsten oxide films presented photocatalytic activity, since doubled the reaction rate of methyl orange dye degradation with respect to the system without the film.

Neste trabalho foram obtidos filmes de óxido de tungstênio pelo método sol-gel modificado, tendo como precursor o tungstato de sódio dihidratado (Na2WO4.2H2O) e como agente estruturante o surfactante cloreto de dodeciltrimetilamônio (DTAC). O comportamento dos sistemas em meio aquoso foi avaliado por medidas de pH, condutividade e viscosidade. Foram avaliadas duas metodologias de obtenção dos filmes de óxido de tungstênio: a primeira consistiu na obtenção de filmes de tungstato de sódio, através de sistemas contendo 10 mmol.L-1 de Na2WO4.2H2O em diferentes concentrações de DTAC, por casting, e conversão do tungstato de sódio a óxido de tungstênio pela acidificação dos filmes; a segunda metodologia consistiu na conversão dos sistemas aquosos contendo 20 mmol.L-1 de Na2WO4.2H2O, em diferentes concentrações de DTAC, em ácido tungstico, obtenção dos filmes por spin coating e, calcinação em presença de ar. Os filmes foram obtidos em substratos de silício (100) recobertos com dióxido de silício e avaliados por Difração de Raios-X, Espectrometria de retroespalhamento Rutherford, Espectroscopia Raman, Microscopia Eletrônica de Varredura e ensaios fotocatalíticos. As alterações na concentração precursor e agente estruturante não afetaram significativamente o pH e a viscosidade dos sistemas precursores. A determinação da concentração micelar crítica (cmc) do DTAC, obtida através da condutividade, foi de 13 mmol.L-1 e 9,88 mmol.L-1 para os sistemas contendo 10 e 20 mmol.L-1 de Na2WO4.2H2O, respectivamente. Em ambas metodologias o produto final foi o óxido de tungstênio em forma de disco e placas. As espessuras dos filmes obtidos na primeira metodologia variaram de 4 a 5 μm e as estruturas tiveram diâmetros médios de 4,37 μm e 114 nm. Na segunda metodologia as espessuras foram de 0,5-1,0 μm e as estruturas obtidas tiveram diâmetros médios em torno de 95-103 nm. Os filmes obtidos apresentaram atividade fotocatalítica, uma vez que duplicaram a velocidade da reação de degradação do corante alaranjado de metila em relação ao sistema sem o filme. / In this work tungsten oxide films have been obtained bymodified sol-gel method, with sodium tungstate dehydrate (Na2WO4.2H2O) as the precursor and the cationic surfactant dodecyltrimethylammonium chloride (DTAC) as structuring agent.The behavior in aqueous media of precursor/structuring agent systems was characterized by pH, conductivity and viscosity measurements. Two methods for obtaining tungsten oxide films were evaluated: the first consisted in obtaining sodium tungstate films from the systems containing 10 mmol.L-1 of Na2WO4.2H2O at different DTAC concentrations, by casting, converting the sodium tungstate to tungsten oxide; the second method consisted in the conversion of the aqueous systems containing 20 mmol.L-1 of Na2WO4.2H2O at different DTAC concentrations to tungstic acid, obtaining the films by spin coating and, posteriorly, calcination in the presence of air. The films were obtained on silicon substrate (100) with a 50 nm layer of silicon dioxide and were characterized by X-ray diffraction, Rutherford backscattering spectrometry, Raman spectroscopy, Scanning Electron Microscopy and photocatalytic tests. The precursor concentration and structuring agent do not affect significantly the pH and the viscosity of the precursor systems in aqueous media.The values of critical micelle concentration (CMC) of DTAC, obtained by the conductivity, were of13 mmol.L-1 and 9,88 mmol.L-1, for the systems containing 10 and 20 mmol.L-1 de Na2WO4.2H2O, respectively.In both adopted methods the final product is the tungsten oxide, with nano and micrometric structures in the form of discs and plates. The thickness of the films obtained in the first method varied from 4 to 5 μm and the structures presented an average diameter around 4,37 μm and 114 nm. The thickness of the films obtained with the second methodvariedfrom0,5to 1 μm and the structures presented an average diameter from 95 to103 nm.The obtained tungsten oxide films presented photocatalytic activity, since doubled the reaction rate of methyl orange dye degradation with respect to the system without the film.

Neste trabalho foram obtidos filmes de óxido de tungstênio pelo método sol-gel modificado, tendo como precursor o tungstato de sódio dihidratado (Na2WO4.2H2O) e como agente estruturante o surfactante cloreto de dodeciltrimetilamônio (DTAC). O comportamento dos sistemas em meio aquoso foi avaliado por medidas de pH, condutividade e viscosidade. Foram avaliadas duas metodologias de obtenção dos filmes de óxido de tungstênio: a primeira consistiu na obtenção de filmes de tungstato de sódio, através de sistemas contendo 10 mmol.L-1 de Na2WO4.2H2O em diferentes concentrações de DTAC, por casting, e conversão do tungstato de sódio a óxido de tungstênio pela acidificação dos filmes; a segunda metodologia consistiu na conversão dos sistemas aquosos contendo 20 mmol.L-1 de Na2WO4.2H2O, em diferentes concentrações de DTAC, em ácido tungstico, obtenção dos filmes por spin coating e, calcinação em presença de ar. Os filmes foram obtidos em substratos de silício (100) recobertos com dióxido de silício e avaliados por Difração de Raios-X, Espectrometria de retroespalhamento Rutherford, Espectroscopia Raman, Microscopia Eletrônica de Varredura e ensaios fotocatalíticos. As alterações na concentração precursor e agente estruturante não afetaram significativamente o pH e a viscosidade dos sistemas precursores. A determinação da concentração micelar crítica (cmc) do DTAC, obtida através da condutividade, foi de 13 mmol.L-1 e 9,88 mmol.L-1 para os sistemas contendo 10 e 20 mmol.L-1 de Na2WO4.2H2O, respectivamente. Em ambas metodologias o produto final foi o óxido de tungstênio em forma de disco e placas. As espessuras dos filmes obtidos na primeira metodologia variaram de 4 a 5 μm e as estruturas tiveram diâmetros médios de 4,37 μm e 114 nm. Na segunda metodologia as espessuras foram de 0,5-1,0 μm e as estruturas obtidas tiveram diâmetros médios em torno de 95-103 nm. Os filmes obtidos apresentaram atividade fotocatalítica, uma vez que duplicaram a velocidade da reação de degradação do corante alaranjado de metila em relação ao sistema sem o filme. / In this work tungsten oxide films have been obtained bymodified sol-gel method, with sodium tungstate dehydrate (Na2WO4.2H2O) as the precursor and the cationic surfactant dodecyltrimethylammonium chloride (DTAC) as structuring agent.The behavior in aqueous media of precursor/structuring agent systems was characterized by pH, conductivity and viscosity measurements. Two methods for obtaining tungsten oxide films were evaluated: the first consisted in obtaining sodium tungstate films from the systems containing 10 mmol.L-1 of Na2WO4.2H2O at different DTAC concentrations, by casting, converting the sodium tungstate to tungsten oxide; the second method consisted in the conversion of the aqueous systems containing 20 mmol.L-1 of Na2WO4.2H2O at different DTAC concentrations to tungstic acid, obtaining the films by spin coating and, posteriorly, calcination in the presence of air. The films were obtained on silicon substrate (100) with a 50 nm layer of silicon dioxide and were characterized by X-ray diffraction, Rutherford backscattering spectrometry, Raman spectroscopy, Scanning Electron Microscopy and photocatalytic tests. The precursor concentration and structuring agent do not affect significantly the pH and the viscosity of the precursor systems in aqueous media.The values of critical micelle concentration (CMC) of DTAC, obtained by the conductivity, were of13 mmol.L-1 and 9,88 mmol.L-1, for the systems containing 10 and 20 mmol.L-1 de Na2WO4.2H2O, respectively.In both adopted methods the final product is the tungsten oxide, with nano and micrometric structures in the form of discs and plates. The thickness of the films obtained in the first method varied from 4 to 5 μm and the structures presented an average diameter around 4,37 μm and 114 nm. The thickness of the films obtained with the second methodvariedfrom0,5to 1 μm and the structures presented an average diameter from 95 to103 nm.The obtained tungsten oxide films presented photocatalytic activity, since doubled the reaction rate of methyl orange dye degradation with respect to the system without the film.

Orientador: Marcos Nogueira Eberlin / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-13T13:39:14Z (GMT). No. of bitstreams: 1 Saraiva_SergioAdriano_M.pdf: 1299368 bytes, checksum: c1436b432ed4c86c7d3658aa29976bfc (MD5) Previous issue date: 2008 / Resumo: As matérias-primas graxas (óleos e gorduras vegetais e animais) e os produtos sintetizados a partir destes insumos são misturas complexas, com aplicações e valores agregados variados. As técnicas disponíveis para caracterizar a composição graxa destas matrizes são muitas vezes restritas, exigindo a necessidade de procedimentos laboriosos. Este trabalho engloba a aplicação de técnicas avançadas de espectrometria de massas (MALDI-MS e ESI-MS) na caracterização de óleos e gorduras vegetais amazônicos (matérias-primas graxas) e surfactantes catiônicos (produtos sintetizados a partir de matéria-prima graxa), sem o emprego de processos de derivatização química ou separação cromatográfica. Espectrometria de massas com ionização por MALDI (MALDI-MS) foi empregada na análise dos óleos de andiroba (Carapa guianensis), castanha do Pará (Bertholletia excelsa), maracujá (Passiflora spp.), buriti (Mauritia flexuosa) e das gorduras das sementes de cupuaçu (Theobroma grandiflorum), murumuru (Astrocaryum murumuru) e ucuúba (Virola sebifera), que foram caracterizados através da composição dos triglicerídeos (TAGs). Obtiveram-se perfis distintos de TAGs para cada óleo e gordura amazônico. Conseqüentemente, a técnica se mostrou adequada para tipificação dos óleos e gorduras estudados, podendo ser adotada como um método rápido e confiável para controle de qualidade destas importantes matérias-primas amazônicas. Em relação aos surfactantes catiônicos, foi desenvolvido um procedimento simples e rápido para identificação e caracterização destas moléculas (incluindo a distribuição de homólogos) em produtos amaciantes têxteis por espectrometria de massas com ionização por electrospray (ESI-MS). À medida que diferentes surfactantes catiônicos podem ser utilizados em amaciantes têxteis, a técnica empregada permite identificar o tensoativo que foi adotado na formulação do produto, sem emprego de padrões de referências. Também é possível verificar casos de falsificação e utilização de moléculas catiônicas que conferem propriedades amaciantes inferiores / Abstract: Fatty raw materials (animal, vegetable oils and fats) and synthesized products from these sources are complex mixtures with diverse applications and added values. Available techniques to characterize the fatty composition of these matrixes are many times restricted and require laborious procedures. This work reports the application of advanced mass spectrometry techniques (MALDI-MS and ESI-MS), without employment of chemical derivatization or chromatographic separation, for characterizing Amazonian rain forest fats and oils (fatty raw materials) and cationic surfactants (products made from fatty raw materials). MALDI-mass spectrometry (MALDI-MS) was applied to characterize the triacylglycerol composition from oils of Andiroba (Carapa guianensis), Brazil Nut (Bertholletia excelsa), Passion Fruit (Passiflora spp.), Buriti (Mauritia flexuosa) and fats from seeds of Cupuaçu (Theobroma grandiflorum), Murumuru (Astrocaryum murumuru) and Ucuúba (Virola sebifera). Characteristic profiles of triacylglycerols (TAG) were obtained for each oil and fat, confirming that the technique is appropriated for the typification of studied samples and can be applied as a reliable and fast method to quality control of these important Amazonian rain forest raw materials. With regard to cationic surfactants, a simple and fast procedure was developed to identify and characterize these molecules (including the homologue distribution) in liquid fabric softeners by electrospray-mass spectrometry (ESI-MS). As different cationic surfactants can be used in fabric softeners, the applied technique allows the identification of the specific tensoative adopted in every formulation, without using reference standards. Also, it is possible to check counterfeit samples and use of some cationic surfactants that confer lower softness / Mestrado / Quimica Organica / Mestre em Química

Orientador: Watson Loh / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-12T12:43:41Z (GMT). No. of bitstreams: 1 Bernardes_JulianadaSilva_D.pdf: 3716800 bytes, checksum: 697cfd08d77b6bb1c1d45598c8324907 (MD5) Previous issue date: 2008 / Resumo: Polieletrólitos associam-se fortemente com surfatantes de carga oposta em meio aquoso, levando a uma separação de fases que resulta em uma fase concentrada, rica em polieletrólito e surfatante, em equilíbrio com uma fase diluída constituída pelos contra-íons. A fase concentrada pode ser constituída de interessantes estruturas supramoleculares advindas das propriedades de auto-organização destes sistemas, que aliadas à possibilidade de modificaremse a geometria da mesofase e as distâncias entre os agregados, tornam estes sistemas ferramentas importantes em processos de fabricação de estruturas micro e mesoporosas e em sistemas de liberação controlada de drogas. O estudo do equilíbrio de fases de sistemas constituídos por polieletrólitos e surfatantes de cargas opostas em água não é tão simples devido ao grande número de componentes presentes no sistema, porém é possível reduzir a quantidade de componentes através da síntese do sal complexo ¿puro¿ (polieletrólito-surfatante), facilitando dessa forma a análise dos diagramas de fases gerados. Neste trabalho o comportamento de fases de sais complexos formados pelo íon surfatante hexadeciltrimetilaônio (CTA) e pelo polieletrólito (PA) em água e na presença de diferentes solventes orgânicos foi investigado. Três efeitos principais foram analisados: efeito da natureza do solvente orgânico; efeito da adição de uma série homóloga de álcoois e efeito da hidrofobicidade do contra-íon polimérico. Os resultados obtidos indicam que a polaridade do solvente orgânico utilizado influencia intensamente nas estruturas formadas pelo sal complexo. Em geral, observou-se a predominância de estruturas lamelares em sistemas contendo co-surfatantes (n-álcoois) e a predominância de estruturas hexagonais em sistemas contendo p-xileno e ciclohexano. A hidrofobicidade do contra-íon polimérico não gerou mudanças significativas nos diagramas de fases obtidos. / Abstrat: Association between charged polymers and oppositely charged surfactants in aqueous solutions may lead to phase separation forming a concentrated phase rich in polyions and surfactant ions, and a more dilute phase, which mostly contains simple ions. The concentrated phases may display a variety of supramolecular structures with diverse and interesting features due to self-assembling properties of these systems, which have found applications in the field of controlled drug delivery and in templating the synthesis of materials with tailored geometries. A complete description of the phase equilibrium in these systems is quite demanding, because addition of polyelectrolyte and oppositely charged surfactant to water leads to the formation of several components, however it is possible to reduce the number of the components by the preparation of the pure complex-salt, which allows to analyze the phase equilibrium in a controlled manner. In this work the phase behavior of complex salts formed by the surfactant ion hexadecyltrimethylammonium (CTA) and the polyacrylate (PA) in water and with different organic solvents were investigated. Three principal effects were analyzed: the effect of the organic solvent nature; the effect of n-alcohol carbon chain length and the effect of the polyelectrolyte hidrophibicity. The obtained results revealed that the organic solvent nature has a strong influence in the structure assumed by the complex salt. From the general analysis, systems containing co-surfactants (n-alcohols) a predominance of lamellar structures was observed, and in systems containing p-xylene and ciclohexane a predominance of hexagonal structures was detected. The polyelectrolyte hidrophobicity did not display significant changes in the obtained phase diagrams. / Doutorado / Físico-Química / Doutor em Ciências

L'objectif de ce travail est le développement et la caractérisation de matériaux magnétiques (magsorbants) qui pourraient être intégrés dans un procédé assisté magnétiquement dont la finalité est de compléter les procédés actuellement utilisés dans les filières de traitement des eaux. Pour s'inscrire dans une démarche d'écoconception, nos matériaux sont des billes millimétriques constituées d'une matrice biopolymère (alginate ou chitosane) dans laquelle sont encapsulées des nanoparticules magnétiques. Ces billes sont bifonctionnelles, elles possèdent des propriétés adsorbantes permettant l'extraction de polluants organiques. Mais leur originalité réside dans leurs propriétés magnétiques qui sont mises à profit pour les séparer magnétiquement de l'eau à dépolluer. Les propriétés d'adsorption des billes magnétiques vis-à-vis de polluants organiques modèles ont été étudiées en regardant l'effet de différents paramètres tels que le pH et la force ionique de la solution, la concentration initiale en polluant et le temps de contact. Dans un premier temps, les polluants modèles considérés sont des colorants chargés. Nous avons montré que les billes d'alginate sont efficaces pour adsorber le bleu de méthylène chargé positivement alors que les billes de chitosane adsorbent le méthylorange chargé négativement. Par contre, le p-nitrophénol est faiblement adsorbé par les billes d'alginate et de chitosane. Pour pallier ce problème, deux solutions ont été proposées dans le but d'augmenter l'hydrophobicité des billes. La première consiste à ajouter un tensioactif cationique aux billes d'alginate. La deuxième solution est d'encapsuler une organobentonite dans les billes. / The aim of this thesis is the development and characterization of multifunctional materials called magsorbents that could be integrated in a water-treatment process to improve current methods or to develop new methods. These materials are millimetric beads with a polymer matrix in which are encapsulated magnetic nanoparticles of maghemite; in order to develop an environment-friendly product, biopolymers such alginate and chitosan were selected for the matrix. Our materials possess adsorbing properties allowing the extraction of organic pollutants from water. The originality of these materials lies in their magnetic properties that could be exploited for their magnetic separation from the treated medium. The adsorption characteristics of the magnetics beads were assessed by using two dyes: methyl orange (negatively charged) and methylene blue (positively charged). We showed that alginate beads are efficient for the removal of positively charged pollutants while chitosan beads adsorb preferentially negatively charged pollutants. p-nitrophenol is weakly adsorbed by both, alginate and chitosan beads. To overcome this problem, two solutions have been proposed in order to increase the beads hydrophobicity. The first one is adding a cationic surfactant, cetylpyridinium chloride, into alginate beads. The second solution is to encapsulate pillared clay into alginate beads. Both solutions show their efficiency in improving p-nitrophenol adsorption by alginate beads.

The aim of this study was to determine the adsorption capacity of activated carbon and organo-zeolites for removal of pesticides in water. In order to prepare organo-zeolite, two kinds of cationic surfactants, namely, hexadecyltrimethyl ammonium bromide (HTAB) and dodecyltrimethyl ammonium bromide (DTAB) were used. Adsorption studies of cationic surfactant on zeolite were investigated in respect to initial concentration of cationic surfactant, time, and temperature. It has been found that the best fitted isotherm equation was Langmuir equation. The observed adsorption rates were found to be equal to the second order kinetic model. The activation energies of cationic surfactant adsorption was determined by using Arrhenius equation.

L'organisation des substances humiques à l'échelle moléculaire reste une question largement débattue, et à ce jour, il n'a pas été possible de trancher entre une structure polymérique en pelotte plus ou moins flexible et un assemblage supramoléculaire de molecules hétérogènes associées par des liaisons hydrogènes et des interactions hydrophobes. Dans cette thèse, nous étudions la reconformation induite par l'addition de tensio-actifs cationiques (Chlorure de C n-trimethylammonium) sur une série de substances humiques (acides fulvique et humiques) ainsi que sur de la matière organique naturelle contenue dans des eaux noires. Des mesures de turbidité, de diffusion de lumière, mobilité électrophorétique, tension de surface, spectroscopie de fluorescence, diffusion des neutrons aux petits angles, et cryomicroscopie à transmission, permettent de decrire les complexes formés entre le tensio-actif et la matière humique. L'association matière humique/tensio-actif dépend à la fois d'interactions d'origine électrostatique et hydrophobe. Une série de structures moléculaires, vésicules, disques, globules, pseudo-micelles, est observée en cryomicroscopie selon la concentration en surfactant. La séquence obtenue est cohérente avec un système catanionique, en d'autres termes une partie de la matière humique est amphiphile et s'organise en assemblage supramoléculaire. L'addition de tensio-actif modifie également fortement le spectre de fluorescence de la matière humique, les nouvelles bandes bien résolues présentes sur le spectre indiquant une restructuration majeure de l'assemblage supramoléculaire. / The structural organization of humic nanocolloids remains a matter of harsh debate, and surprisingly, it is yet not possible to decide between an arrangement of the humic matter in the form of randomly coiled macromolecules more or less connected, and a supramolecular organization of small heterogeneous molecules linked by hydrogen bonds and hydrophobic interactions. In this study, we investigate the reconformation induced by the addition of cationic surfactants (C n-trimethylammonium chloride) of varying alkyl chain length with a series of humic substances (HS) and Dissolved Organic matter (DOM) from two blackwater rivers of the Central Amazon. Turbidity measurements, Dynamic light scattering, electrophoretic mobility, surface tension, fluorescence spectroscopy, small angle neutron scattering and cryo-transmission electron microscopy (cryo-TEM), are combined to describe the Humic Substance/Surfactant complexes obtained. The association between the oppositely charged HS and cationic surfactant is driven by both electrostatic and hydrophobic interactions. A variety of molecular structures, unilamellar vesicles, disks, globules, spheroidal micelles, are visualized by cryo-TEM depending on surfactant concentration. Such sequence, consistent with those displayed by catanionic systems, provides an independent confirmation of both the amphiphilic nature of HS and of its supramolecular organization. In addition, the molecular rearrangement was investigated using single-scan fluorescence emission spectra spectroscopy, thus identifying the chemical groups responsible for the fluorescence properties in HS and DOM. The addition of cationic surfactant to HS/DOM unveils an unexpected fine structure of humic-like fluorescence through new emission peaks that are not evidenced in the references HS/DOM. An enhanced protein-like fluorescence indicating major restructuration and structural stacking/de-stacking is observed. All our results support a supramolecular organization of humic substances and DOM.

The study of protein and surfactant interactions is of great significance in a number of applications, such as the cosmetic, food or pharmaceutical industries and many others. However, they require further study due to their compositional complexity and the limitations of current analytical approaches. In this thesis, the cationic surfactant septonex in combination with two differently charged proteins lysozyme and bovine serum albumin under different physiological conditions (temperature, surfactant concentration, environment and others) was selected to study the interactions. Characterization of protein-surfactant interactions is a very important but challenging task, therefore it is essential to use appropriate approaches to explore the nature of these interactions. In order to unify the information to provide rational models, calorimetric methods (DSC, ITC) and dynamic light scattering were used. Isothermal titration calorimetry monitors the evidence for the formation of the system of the mentioned substances and information on aggregation behavior, differential scanning calorimetry characterizes the thermal stability of proteins and dynamic light scattering made it possible to monitor changes in particle size. Both proteins have been proven to interact with positive septonex, even if the lysozyme molecule is also positively charged. However, significant differences were found between the two proteins. From the obtained results it is evident that the identical charge of the protein with the surfactant has an effect on the intensity of the measurement, although all measured interactions showed an endothermic character.