In this work the production of synthesis gas from a mixture of methane (CH4) and carbon dioxide (CO2) by thermal plasma was studied. The best relation found for the gas mixture [CO2]/[CH4] was 1.3. Under the excess of CH4 in the gas mixture soot was formed and also benzene, indene and naphthalene were identified. The disulfides compounds in the gas mixture were degraded causing no interference in the synthesis gas production, suggesting no needs of pretreatment step for sulfurorganic compounds removal in the process
Samples of shells of oysters and mussels from sea farm around the Santa Catarina Island in south Brazil were collected and analyzed by DRX, FRX, SEM, CHN-S, FTIR, TG, AAS/Flame and AAS /GF. The results showed that the crystalline structure of mussel's shells is mainly formed by aragonite and the oyster's shells by calcite. The calcium percentage in both shells species was in the range of 33 to 35% and also 850 and 1200 mg/kg of strontium was detected in the shells of oysters and mussels, respectively. The content of organic matter was larger in the mussel's shells and the thermal degradation of both shells species occurred by three events at different temperatures from 250 to 830 ºC.
Decomposition of carbon tetrachloride in a DC thermal plasma reactor was investigated in argon atmosphere. The operational parameters such as plasma torch power and argon flow rate versus CCl4 conversion were examined. The CCl4 net degradation was determined by GC-FID, the chlorine produced was quantified by iodometric titration, the solid carbon was characterised by Raman spectroscopy and by BET analysis. The solid carbon collected inside de plasma reactor was submitted to solid/liquid extraction and the desorbed species were identified by GC-MS.
Films of pure poly(styrene) (PS), pure poly(methyl methacrylate) (PMMA), a 1:1 PS/PMMA blend and a PS-b-PMMA copolymer, were prepared and tested for cell adhesion using L929 mouse fibroblasts. All polymer films were found to be good substrates for cell adhesion and proliferation, and both processes were slightly favored on films of the 1:1 PS/PMMA blend. The same results were obtained in terms of cell number and morphology for cells cultured on films, glass coverslips or plastic plates. The chemical characteristics of polymer films make them suitable supports for cell attachment and proliferation, indicating that these films are good candidates for biomedical uses.
Filmes de poli(estireno) (PS), poli(metacrilato de metila) (PMMA), blenda de PS/PMMA (1:1) e copolímero PS-b-PMMA foram preparados e avaliados quanto à adesão celular usando fibroblastos de camundongos L929. Embora todos os filmes poliméricos tenham se mostrado bons substratos para o crescimento e proliferação celular, estes processos foram levemente favorecidos na blenda PS:PMMA. O número e a morfologia foram idênticos para cultura de células nos filmes e na lamínula de vidro ou na placa de plástico. A característica química dos filmes poliméricos é adequada para suportar o ataque e proliferação das células, sugerindo que esses filmes são bons candidatos para usos biomédicos.
The contamination level of silicon oil used as insulation liquid in high-voltage transformers by ascarel (PCBs) is above those permitted by the Brazilian law. Thus new techniques able to detect ascarel, with low operational costs, are very attractive. The present work proposes an analysis of the contamination levels of silicon oil using the following techniques: naphthalene anion radical reaction for ascarel dechlorination; and potentiometry with an ion-selective electrode for chloride ion determination. The data obtained with the proposed methodology agree well with those from the official methodology, (method IEC 61619).
The surface activity of humic acids (HA) is a parameter which might be considered in the evaluation of all types of aggregation of these substances. In this work the surface tension of aquatic and terrestrial-HA aqueous solutions was observed under varied conditions of pH, concentration and ionic strength. Results showed that HA present surface activity for a extent range of concentration. The surface tension decreases with HA concentration increasing and, for all samples exist a concentration value above which a reduction in the rate of the solute migration to the solution surface is observed. This value is sensibly reduced and sharpened with the increasing of the ionic strength. Surface tension is also reduced with the acidity increasing, being a minimum reached between pH 3 and 5. Observed effects are explained in view of conformational arrangements of HA which tend to agglomerate in micelle-like domains in aqueous solutions.
This paper presents a study of adsorption of xanthate with alkyl chain of two (C2XK), four (C4XK) and eight (C8XK) atoms of carbon, on pyrite from Santa Catarina, Brazil. The results showed that pyrite surface changes from hydrophilic to hydrophobic when xanthate is adsorbed increasing the contact angle to 35º for C2XK, and to 90º for C4XK and C8XK. The rate of flotation of pyrite particles after adsorption increases with the increase of the number of carbon atoms in the alkyl chain in agreement with the results of contact angle measurements.