Fernando Dal Pont Morisso

Análise termogravimétrica da pirólise da acácia-negra (Acacia mearnsii de Wild.) cultivada no Rio Grande do Sul, Brasil

RESUMO – Este trabalho reporta um estudo experimental que objetivou a investigacao dos efeitos da temperatura, da taxa de aquecimento e do tempo na eficiencia e nos parâmetros cineticos da decomposicao da madeira de acacia-negra (Acacia mearnsii De Wild.) plantada no Rio Grande do Sul. O processo da pirolise da acacianegra foi investigado por analise termogravimetrica (TGA), e os parâmetros cineticos foram obtidos a partir de ensaios dinâmicos e isotermicos. Os ensaios dinâmicos foram conduzidos desde a temperatura ambiente ate 900 C, sob taxas de aquecimento que variaram de 2 a 50 o C.min -1 . Os ensaios isotermicos foram realizados entre 250 e 750 o C, ao aquecer a amostra ate a temperatura desejada e mantendo-se nessa temperatura por 2 h. Os dados cineticos obtidos dinamicamente foram tratados segundo os metodos de Ozawa e Kissinger. Ja os parâmetros cineticos conseguidos isotermicamente foram calculados ao considerar que a reacao de pirolise segue uma cinetica de primeira ordem em todo o intervalo de tempo e temperatura empregados. Os resultados denotaram a aplicabilidade dos metodos adotados, visto que os valores da energia de ativacao do processo de pirolise, alem de se aproximarem entre si, isto e, 170-180 kJ.mol -1 , segundo modelos dinâmicos, e 140 kJ.mol -1 , segundo o metodo isotermico, aproximaram-se tambem dos valores reportados na literatura sobre a pirolise de compostos celulosicos (150-200 kJ.mol -1 ). Os resultados contribuem para a melhor compreensao dos processos de pirolise da biomassa, em especial da acacia-negra, o que pode levar ao melhoramento das atuais praticas de conversao da biomassa em carvao vegetal.

Facile, green and scalable method to produce carrageenan-based hydrogel containing in situ synthesized AgNPs for application as wound dressing

This manuscript was focused on introducing a facile, green and scalable method to produce kappa-carrageenan (κC) hydrogel membranes containing in situ synthesized silver nanoparticles (AgNPs). In a typical protocol, κC hydrogels were obtained by heating (sol phase), followed by cooling (gel phase) the polysaccharide solution, which enabled the simultaneous synthesis of AgNPs during the heating time. The as synthesized AgNPs were characterized spectrophotometrically, and by dynamic light scattering and transmission electron microscopy. The swelling properties at different pH and the antimicrobial activity of κC-AgNP hydrogel were investigated. AgNPs were mostly spherical in shape, crystalline in nature and measuring ca. 27nm in diameter. The in situ synthesis of AgNPs changed the swelling properties of κC hydrogel and also reduces its viscosity and gelling temperature. The AgNPs were continuously released from κC hydrogel for up to 48h in a concentration sufficient to prevent the bacterial growth as confirmed by antimicrobial tests. The simplicity involved in the AgNPs synthesis combined to the good spreadability of κC hydrogel makes this method suitable for scale-up to manufacturing quantities of wound dressing.

PYROLIGNEOUS LIQUOR PRODUCED FROM ACACIA MEARNSII DE WILD WOOD UNDER CONTROLLED CONDITIONS AS A RENEWABLE SOURCE OF CHEMICALS

Acacia mearnsii de Wild (black wattle) is one of the most important trees planted in Southern Brazil for tannin extraction and charcoal production. The pyrolysis of the black wattle wood used for obtaining charcoal is performed in brick ovens, with the gas fraction being sent directly into the environment. The present study examines the condensable compounds present in the liquor produced from black wattle wood at different thermal degradation conditions, using gas chromatography coupled with mass spectrometry (GC/MS). Branches of black wattle were thermally degraded at controlled ambient and temperature conditions. Overall, a higher variety of compounds were obtained under atmospheric air pressure than under synthetic air pressure. Most of the tentatively identified compounds, such as carboxylic acids, phenols, aldehydes, and low molecular mass lignin fragments, such as guayacol, syringol, and eugenol, were products of lignin thermoconversion. Substituted aromatic compounds, such as vanillin, ethyl vanillin, and 2-methoxy-4-propeny-phenol, were also identified. At temperatures above 200 oC, furan, 2-acetylfuran, methyl-2-furoate, and furfural, amongst others, were identified as polysaccharide derivatives from cellulose and hemicellulose depolymerization. This study evidences the need for adequate management of the condensable by-products of charcoal production, both for economic reasons and for controlling their potential environmental impact.

Determinação de 2,5-hexanodiona em urina empregando cromatografia líquida de alta eficiência, após derivatização com 2,4-dinitrofenil-hidrazina

A method for quantifying urinary 2,5-hexanedione was optimized and validated. Urine samples were hydrolyzed and derivatized with 2,4-dinitrophenylhydrazine. The analyte was separated in a high performance liquid chromatography system with a diode array detector, using a C18 column (150 x 4.6 mm, p.d. 5 µm) and a mobile phase composed of phosphate buffer pH 2.3:acetonitrile (40:60, v/v), at a flow rate of 1 mL/min. The chromatograms were monitored at 334 nm. Retention time was 7.3 minutes. Main validation parameters were: coefficient of determination: 0.9994, accuracy: 96 to 107%; intra-assay precision (RSD): 3.08 to 6.72%; inter-assay precision (RSD): 2.54 to 8.17% and limit of quantitation of 0.19 µg/mL.

OBTAINING NIOBIUM OXIDES IN ACETIC ACID WITH ADDITION OF HF

During anodizing, the chemical attack of hydrofluoric acid (HF) electrolytes on niobium can promote the formation of oxides with porous structures. However, this chemical attack can also cause an intense dissolution of the oxide during its formation. This effect can be minimized by varying the HF concentration of the anodizing electrolyte, thereby controlling the growth of the porous oxide. Studies have alternative electrolytes that do not use HF to obtain porous oxides. Thus, organic electrolytes, such as acetic acid, may be a viable alternative. In this context, the objective of this study is to obtain and evaluate the anodization of niobium in acetic acid at different current densities (10, 20 and 50 mA/cm2) and to study the influence of the addition of HF to the electrolyte. The results showed that the anodized anodic in acetic acid, under conditions of 100 V and 10 mA/cm2, presented porous oxide with less defects. Therefore, this result indicates that it is possible to produce porous niobium oxides by anodizing in HF-free electrolyte.

Determinação de bussulfano em plasma através de cromatografia líquida de alta eficiência com detector de arranjo de diodos e derivatização com dietilditiocarbamato de sódio

A high performance liquid chromatographic-diode array detection method for the determination of busulfan in plasma was developed and validated. Sample preparation consisted of protein precipitation followed by derivatization with sodium diethyldithiocarbamate and liquid-liquid extraction with methyl-tert-butyl ether. Chromatograms were monitored at 277 nm. Separation was carried out on a Lichrospher RP 18 column (5 µm, 250 x 4 mm). The mobile phase consisted of water and acetonitrile (20:80, v/v). The method presented adequate specificity, linearity, precision and accuracy and allowed reliable determination of busulfan in clinical plasma samples, being applied to three patients submitted to bone marrow transplantation.