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Aiming at investigating the use of alternative materials for the production of thermal insulation and, mainly, to replace the carbon structures (graphene and nanotubes), extensively used in the development of aerogels, the present study had the objective to produce cellulose/biochar aerogels and to evaluate their properties. The aerogels were produced from Pinus elliottii cellulose fibers and biochar produced from these fibers. The materials were characterized in their physical, thermal and mechanical properties. They were extremely light and porous, with a density between 0.01 and 0.027 g cm -3 and porosity between 93 and 97%. Several percentages of biochars were added to the cellulose suspension (0-100% w/w). The use of 40 wt% biochar provided a 60% increase in the compressive strength of the aerogel in relation to the cellulose aerogel. Besides that, the addition of this carbonaceous structure did not influence significantly the thermal conductivity of the aerogels, which presented a thermal conductivity of 0.021-0.026 W m -1 K -1 . The materials produced in the present research present a great potential to be used as insulators due to the low thermal conductivity found, which was very similar to the thermal conductivity of the air and also of commercial materials such as polyurethane foam and expanded polystyrene.

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The production of a material with rigid, multifunctional three-dimensional porous structure at a low cost is still challenging to date. In this work, a light and rigid carbon foam was prepared using rice husk as the basic element through a simple fermentation process followed by carbonization. For the fermentation process, the amount of biological yeast (7.5 g for the carbon foam CA-1P and 5 g for the carbon foam CA-2P) was used to evaluate its influence on the morphology of the foams. In order to prove that the heat treatment made in the foam alters the hydrophilic character of the rice husk foam, a chemical treatment with steam deposition was carried out. The foams were characterized by the following analyzes: apparent density, micrograph, thermogravimetry, contact angle, water sorption capacity and thermal conductivity. Visually, the CA-1P foams presented a structure with larger pores due to the greater amount of yeast used in its formulation. The heat treatment of rice potato foams proved to be as efficient as the chemical treatment for water contact angle above 90º, proving the ability of the foams to repel water/moisture. The thermal conductivity of the foams (0.029 and 0.026 W m-1 K-1 for CA-1P and CA-2P, respectively) was close to the conductivity of polyurethane foams (0.032 W m-1 K-1). Thus, the method used in the production of the carbon foams produced from the rice husk proved to be effective. In addition, the foams produced have the potential to be used for thermal insulation.

A utilização de adsorventes é uma maneira eficaz para a remoção do óleo em terra ou água. Os aerogéis são uma classe de adsorventes, que são caracterizados pela sua estrutura altamente porosa e o seu baixo teor de sólidos, o que confere ao material uma elevada capacidade de adsorção de petróleo. No presente trabalho, foi avaliada a influência da concentração de celulose e metiltrimetoxissilano (MTMS) na capacidade de adsorção de petróleo do aerogel. Os aerogéis produzidos apresentaram baixa massa específica (menor que 0,025 g cm-3) e elevada porosidade (maior que 95%). Pelas micrografias é possível visualizar alterações na superfície da fibras, com a formação de um filme, enquanto que na análise dos espectros obtidos, bandas características do silano foram identificadas nas amostras com tratamento químico. A hidrofobicidade dos aerogéis foram evidenciadas pelas medidas do ângulo de contato da superfície dos mesmos com a água, sendo obtidos valores superiores a 120°. A capacidade de adsorção dos aerogéis atingiu 78 g g-1 para o meio homogêneo e 53 g g-1 para o meio heterogêneo. Palavras-chave Aerogéis, celulose, adsorção, petróleo.