Agradeço a Deus, de quem advêm todas as coisas, por me fornecer a vida, por me permitir reconhecer a bondade dele de me trazer até aqui e de ter colocado pessoas tão especiais em meu caminho. Agradeço aos meus pais, Rosana e João, e aos meus irmãos, Alessandro e Viviane, que sempre me incentivarem a seguir os meus sonhos e objetivos e nunca mediram esforços em meu favor. A todos os amigos que estiveram comigo nessa jornada, aqueles com quem compartilhei os primeiros meses do mestrado, que tornaram os momentos de estudo e a vida mais leves e divertidos. Meu agradecimento eterno àqueles que fizeram toda a diferença desse período e que vou levar para sempre no coração, Bruna, Érica, Igor, Karine, Laryssa, Luis, Olga, Roberta e Thais. A todos do NucBio, pela parceria, compreensão e companheirismo. A todos os "membraneiros", em especial Natália e Lidiane, pelos conhecimentos compartilhados, pelos materiais fornecidos, pela paciência e auxílio. Ao Altamirando Costa Ribeiro Neto pela ajuda prestada. Ao Rodolfo Brandão pelas consultorias técnicas, programas instalados e problemas resolvidos. À minha orientadora, Prof.ª Dr.ª Miria Hespanhol Miranda Reis por aceitar me orientar e por toda compreensão ao longo desses dois anos. Agradeço o apoio, ensinamentos, prontidão e confiança, que foram imprescindíveis para o meu crescimento acadêmico e pessoal. Agradeço também minha co-orientadora Prof.ª Dr.ª Vicelma Luiz Cardoso, por todas as ideias e dicas sempre que solicitadas. Aos professores membros da banca examinadora, Prof. Dr. Antonio Eduardo da Hora Machado e Prof.ª Dr.ª Fabiana Regina Xavier Batista, pelas contribuições.

Biocides are used against microbiological damage. Encapsulation can increase their physicochemical stability and allow for controlled release. The characteristics of the biocides influences the encapsulation methods and are related here.

Palladium membranes represent a suitable alternative to obtain high purity hydrogen for industrial applications. The modeling of hydrogen permeation through composite membranes is important to understand gas separation systems. Here, experimental and calculated hydrogen flux data through composite palladium/alumina membranes were compared. A dense palladium film of 2.4 μm thick was deposited on a porous support and the produced composite membrane presented infinite hydrogen/nitrogen selectivity. Experimental molecular hydrogen flux at 100 kPa and 723 K was 0.1015 ± 0.0009 mol m−2 s−1. Calculated molecular hydrogen fluxes with the conventional permeation model, without considering external mass transfer and support resistances, were at least 5.7 times greater than experimental data. However, calculated hydrogen flux was only 6.7% lower than the experimental flux at 100 kPa and 723 K when external mass transfer and support resistances were included in the conventional permeation model. Thus, external mass transfer resistances and the permeation through the porous support should be considered for a suitable description of hydrogen fluxes through composite palladium membranes.

Supported palladium (Pd)/silver (Ag) composite membranes have been investigated for hydrogen separation mainly in order to avoid hydrogen embrittlement, improve hydrogen permeance and reduce membrane cost. The electroless method is recommended for the co-plating of Pd and Ag on a substrate surface. However, Ag precursor has a higher redox potential than Pd and, thus, Ag is preferentially deposited, which compromises the membrane selectivity to hydrogen. Here we investigated the morphology and elemental composition of supported palladium (Pd)/silver (Ag) composite membranes produced by different methods. The first membrane was produced from a plating solution of 80 wt% of Pd and 20 wt% of Ag. The membrane surface presented several large dendritic crystals that not grown in a direction to form a dense metallic film. According to EDS results, the membrane surface presented similar Pd and Ag composition, which confirms the preferential Ag deposition. At room temperature, this membrane presented a nitrogen flux of 0.35 mol m-2 s-1 at 200 kPa of transmembrane pressure. Thus, the formed membrane is not suitable for hydrogen separation. The second membrane was formed by adding small amounts of Ag to the plating solution during the electroless process. The final plating solution contained 75 wt% of Pd and 25 w% of Ag. The membrane thickness was 2 µm, but the membrane morphology was not totally dense. According to EDS results, the Ag composition was greater than the Pd composition, especially at the membrane top surface. This membrane also presented high nitrogen permeance probably due to the holes formed on the membrane surface. Thus, although the controlled addition of Ag is recommended to form dense membranes, the Ag was preferentially deposited over the Pd when starting with the highest rate of Ag addition. Adding lower Ag rates at the beginning could be helpful to avoid the preferential Ag deposition.

Supported palladium (Pd)/silver (Ag) composite membranes have been investigated for hydrogen separation mainly in order to avoid hydrogen embrittlement, improve hydrogen permeance and reduce membrane cost. The electroless method is recommended for the co-plating of Pd and Ag on a substrate surface. However, Ag precursor has a higher redox potential than Pd and, thus, Ag is preferentially deposited, which compromises the membrane selectivity to hydrogen. Here we investigated the morphology and elemental composition of supported palladium (Pd)/silver (Ag) composite membranes produced by different methods. The first membrane was produced from a plating solution of 80 wt% of Pd and 20 wt% of Ag. The membrane surface presented several large dendritic crystals that not grown in a direction to form a dense metallic film. According to EDS results, the membrane surface presented similar Pd and Ag composition, which confirms the preferential Ag deposition. At room temperature, this membrane presented a nitrogen flux of 0.35 mol m-2 s-1 at 200 kPa of transmembrane pressure. Thus, the formed membrane is not suitable for hydrogen separation. The second membrane was formed by adding small amounts of Ag to the plating solution during the electroless process. The final plating solution contained 75 wt% of Pd and 25 w% of Ag. The membrane thickness was 2 µm, but the membrane morphology was not totally dense. According to EDS results, the Ag composition was greater than the Pd composition, especially at the membrane top surface. This membrane also presented high nitrogen permeance probably due to the holes formed on the membrane surface. Thus, although the controlled addition of Ag is recommended to form dense membranes, the Ag was preferentially deposited over the Pd when starting with the highest rate of Ag addition. Adding lower Ag rates at the beginning could be helpful to avoid the preferential Ag deposition.