RESUMO -Uma das principais vantagens das graxas lubrificantes é o fato de não escorrerem do local em que são colocadas, o que dispensa a implantação de sistemas dispendiosos de vedação. A degradação das graxas sob condições de operação ocorre principalmente através de mecanismos de oxidação. O objetivo deste trabalho foi determinar a influência da atmosfera na degradação térmica oxidativa de graxas lubrificantes à base de cálcio. Para tanto, as amostras foram submetidas a diferentes temperaturas (150, 170, 190 e 210 ºC), durante períodos de tempo distintos (1 e 6 h), sendo caracterizadas por técnicas de análise térmica, em atmosfera inerte (N 2 ) e oxidante (O 2 ), e espectroscopia na região do infravermelho. Os resultados mostraram que, em atmosfera oxidante, houve deslocamento das curvas TG para temperaturas mais baixas, provavelmente devido ao fato das amostras terem sofrido combustão. Em atmosfera inerte, a decomposição ocorreu em número maior de etapas do que em atmosfera oxidante, gerando menor quantidade de resíduos do que as amostras submetidas à atmosfera de O 2 . Além disso, houve pequenas modificações nas temperaturas de início de decomposição das amostras degradadas em comparação com as não degradadas. Com relação ao Infravermelho, os espectros apontaram que a degradação ocorreu através de processo de oxidação, resultando na formação de compostos carbonilados, confirmados pela presença de bandas referentes aos grupos C=O e CC(C=O)O.
INTRODUÇÃOA lubrificação consiste da separação de dois elementos mecânicos em movimento, o que gera atrito e desgaste. Os lubrificantes formam um filme fino de óleo evitando contatos metálicos diretos (RUPRECHT, 2008).O lubrificante é um fluido que, aplicado às máquinas, cria uma camada impermeável entre as peças, reduz o aquecimento e evita que aquelas em movimento provoquem atrito ou se desgastem. É um material mole e facilmente deformável que apresenta ligações secundárias fracas.
In Brazil, the leather industry is an important economic segment moving around U$ 3 billions of dollars a year. However, high amounts of water are requested to transform skin animals into leather, causing high wastewater amounts to be consequently produced. A major problem is attached to the presence of chromium in the wastewater from the tanning process. Chromium is a heavy metal potentially toxic both to the environment and to the human health. In order to control the levels of chrome dumped into the environment, Brazilian agencies require the treatment of effluents by the generating source. Thus, this study aimed to develop an alternative method to the removal of chromium in wastewater from the leather industry using the Opuntia ficus-indica biomass as ecofriendly biosorbent. Crude waste samples were collected in a tannery stabilization pond for chromium quantification and further treatments. The powdered Opuntia ficus-indica was obtained from species collected in Pernambuco, Brazil, and its physical parameters and pH PCZ were characterized. Adsorptions studies and acute toxicity were also carried out. The biomass remaining after the sorption was analyzed through scanning electron microscopy and Fourier-transform infrared spectroscopy. The chromium content was above the limit allowed by the Brazilian regulatory agency. In sorption studies, biomass was able to remove 74.8% and 84.88% of Cr (III) using 2.0 g and 4.0 g of biomass, respectively. The surface of biomass is very favorable to biosorption and the chemical bindings among oxygen atoms present in the chemical components of this biomass and the heavy metal was confirmed through infrared spectrum. This study proved that Opuntia ficus-indica is effectively biosorbent to chromium, promising and with low costs for the leather industry, able to reduce its ecotoxicity as proven by chemical and biological assays.
Alternative methods, as adsorption, with use of readily available and low cost materials have been used to remove contaminants in water bodies. Objective of this work was to study adsorptive power of cactus pear forage (Opuntia tuna Mill) biomass without bark as adsorbent for removal of gasoline in water bodies. Material underwent a natural drying process and then comminution to powder form. In adsorption kinetics study, were evaluated time between 5 and 60 minutes (with a 5-minute interval) and equilibrium concentrations of contaminants ranging from 5 to 50%, with a 5% variation rate. It was observed that process was rapid, with greater adsorption efficiency over time for 30 minutes. Langmuir model fitted well to experimental data, with a maximum adsorption capacity of 5.94 g.g -1. Results confirm that cactus pear forage without peel appears as a promising biomass in gasoline adsorption process.
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