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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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Yerba mate (YM) is widely consumed in Latin American countries, and its residues can be used as bio‐resources such as reinforced in epoxy composites. The present work aims to produce epoxy resin composites and evaluate the influence of post‐consumed YM as reinforcement. The concentrations of YM used were 5, 10, and 20% (wt/wt). Chemical, thermal, morphological, and dynamic mechanical behaviors were explored. The YM incorporation did not influence chemically on the epoxy structure and a pull‐out phenomenon was observed as YM content increased. The YM at lower concentrations (5 and 10%) led to higher values of activation energies calculated from model‐free isoconversional methods. On the other hand, the composite e/YM 20 wt% improved all dynamic‐mechanical properties. YM proved to be a suitable and cheap reinforcement for epoxy resin.

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The objective of this work was to characterize and study the behavior of the adsorption process of cellulose/biochar cryogels through isotherm models and adsorption kinetics. The cryogels were produced from a cellulose suspension obtained by mechanical fibrillation of 0.75 and 1.5% w/w unbleached long-fiber cellulose of the Pinus elliotti species. Into this suspension, 5, 10, and 20% w/w (relative to cellulose mass) biochar were added; then, the suspension was frozen and freeze-dried. After this, 2 mL of methyltrimethoxysilane (MTMS) was deposited on the cryogels. Characterization analyses were performed on the cryogels, including specific mass and porosity and sorption capacity, in addition to the study of adsorption kinetics and isotherms. The cryogels showed a porosity of above 90% and a specific gravity of less than 0.035 g cm–3. The heterogeneous sorption capacity varied according to the concentration of cellulose used, and with the addition of 5% w/w biochar in the cellulose cryogel, the highest sorption capacity was obtained, 73 g g–1 of petroleum and 54 g g–1 of SAE20W50 oil. In the study of adsorption isotherms, the Freundlich model best fitted the process. Therefore, it was concluded that the process of petroleum adsorption by the cellulose cryogel occurs in multiple layers. In addition, the cellulose/biochar cryogel developed in the present work is suitable for use in the adsorption of organic liquids.

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