ABSTRACT The objective of this work was to evaluate and compare the potential of polyurethane and kapok (Chorisia speciosa) residues as sorbent materials in the treatment of diesel spillage. To determine the sorption capacity, gravimetric tests were performed in static medium at room temperature and at different temperatures (10, 15 and 28 °C) and varying the time of contact between the sorbent material and diesel. It was observed that the sorption process occurs at a high velocity, with saturation point achieved in the first 5 minutes of contact, and the natural fiber presents higher sorption capacity compared to the polyurethane residue due to the low viscosity of diesel oil, that contributes to reduce de entrapment inside the porous foam. It has also been observed that the polyurethane residue exhibits an increase in sorption capacity with time and temperature increase. Scanning electron microscopy (SEM) analysis have shown that the main morphological property involved in smooth oil sorption was the high porosity associated with a small porous diameter. The kapok presented sorption capacity of 37 g/g in equilibrium demonstrating its great potential of application as a sorbent material for the treatment of diesel spillage.

Abstract This study aims to develop a nano-sized fluoridated layered double hydroxide (LDH)-based release system via hydrothermal treatment for the controlled delivery of fluoride (F-) ions in the oral environment. The synthesis of conventional LDH-type (C-LDH) precursor nanomaterials was conducted using a co-precipitation method at constant pH, and the nanoparticulate-LDH (N-LDH) was synthesized by a hydrothermal procedure. Fluoride LDH (F-LDH) products were obtained through indirect synthesis using the precursor ion-exchange technique by varying the agitation time (2 and 24 h) and temperature (25 and 40 °C) to produce 12 material samples. The materials were characterized by energy dispersive x-ray, hexamethyldisilazane, digital radiography x-ray, Fourier-transform infrared, thermogravimetric analysis, and scanning electron microscopy. Additionally, the F-release kinetic profile was evaluated for 21 d in neutral and acid media with mathematical model analysis. Products with varying F-quantities were obtained, revealing specific release profiles. In general, there was a higher F-release in the acid medium, with emphasis on F-LDH-8. Fluoride-LDH and controlled fluoride delivery was successfully obtained, proving the potential of these nanomaterials as alternative anti-caries agents.

Resumen Las enzimas inmovilizadas son catalizadores de gran interés industrial, ya que unen las ventajas de la catálisis heterogénea con la alta selectividad y las condiciones de operación suaves de las enzimas. El biochar es un material carbonoso poroso, que tiene la característica de que es un fuerte candidato para incorporar enzimas en su estructura. Otro hecho relevante es la posibilidad de cambios y adaptaciones por condición de síntesis en la estructura de Biochar debido a las necesidades de la aplicación. En este contexto, el objetivo de este trabajo fue el estudio de la inmovilización de lipasa en un biochar producido por pirólisis (600 ° C) de un residuo agrícola llamado tocón de yuca. Se evaluaron diferentes concentraciones enzimáticas (0.1, 0.25 y 0.5 g / L) para determinar la afinidad entre la enzima y el biochar. Los resultados obtenidos mostraron que la enzima estudiada se podía inmovilizar fácilmente en el biochar, obteniendo como rendimiento de inmovilización 61.2% cuando se usa la mayor concentración de enzima.

Abstract The immobilized enzymes are catalysts of great industrial interest, as it unites the advantages of heterogeneous catalysis with the high selectivity and mild operation conditions of the enzymes. Biochar is a porous carbonaceous material, which have characteristic that it makes a strong candidate to incorporate enzymes in its structure. Another relevant fact is the possibility of changes and adaptations by synthesis condition in the biochar structure due to the application needs. In this context, the objective of this work was the study of immobilization of lipase (type II, code l3126, Sigma Aldrich) in a biochar produced by pyrolysis (600oC) from an agricultural residue called cassava stump. It was evaluated different enzymatic concentrations (0.1, 0.25 and 0.5 g/L) in order to determine the affinity between the enzyme and biochar. The obtained results showed that the enzyme studied could be easily immobilized in the biochar, obtaining as immobilization yield 61.2% when using the highest concentration of enzyme.

Resumo As enzimas imobilizadas são catalisadoras de grande interesse industrial, pois unem as vantagens da catálise heterogênea com a alta seletividade e condições de operação moderada das enzimas. Biochar é um material carbonoso poroso, que possui característica que faz forte candidato a incorporar enzimas em sua estrutura. Outro fato relevante é a possibilidade de mudanças e adaptações por condição de síntese na estrutura do Biochar devido às necessidades de aplicação. Neste contexto, o objetivo deste trabalho foi o estudo da imobilização da lipase em um biochar produzido por pirólise (600o C) a partir de um resíduo agrícola denominado cepa de mandioca. Foram avaliadas diferentes concentrações enzimáticas (0,1; 0,25 e 0,5 g / L) para determinar a afinidade entre a enzima e o biocarvão. Os resultados obtidos mostraram que a enzima estudada pode ser facilmente imobilizada no biocarvão, obtendo como imobilização rendimento de 61,2% quando se utiliza a maior concentração de enzimas.