Sphere-to-rod transitions of cetyltrimethylammonium (CTA+) micelles with dichlorobenzoate counterions are remarkably substituent dependent. Simultaneous estimates of the interfacial molarities of H2O, MeOH, and Cl- and 2,6- and 3,5-dichlorobenzoate (2,6OBz and 3,5OBz) counterions were obtained by the chemical trapping method in mixed micelles of CTACl/CTA3,5OBz and CTACl/CTA2,6OBz without added salt. Increasing the CTA3,5OBz mole fraction produces a marked concurrent increase in interfacial 3,5OBz- and a decrease in interfacial H2O concentrations through the sphere-to-rod transition. No abrupt concentration changes are observed with increasing CTA2,6OBz mole fraction. Counterion-specific changes in the interfacial water concentration may be a major contributor to the delicate balance of forces governing micellar morphology.

No abstract

No abstract

The number of chemical compounds in sewage and consequently their release into the environment is increasing. Some of them are toxic and many of them are considered endocrine disrupters. Here, the capacity of three wastewater treatment plants (WWTPs) to remove caffeine, hormones and bisphenol-A was investigated. Bisphenol-A and caffeine are highly water-soluble compounds, as opposed to hormones (estradiol, estriol, and ethynilestradiol) which are hydrophobic compounds. In the Sewage Treatment Plant (SWT)1 the sewage is treated by activated sludge process, in the second plant, SWT2, sewage is treated by upflow anaerobic sludge blanket reactors followed by dissolved air flotation, and in the third, SWT3 sewage is treated by stabilization lagoons. The first lagoon is 3.5 m deep, thus facultative and polishment processes occur. It was speculated that there was a difference in efficiency between the three plants in removing micropollutants. Small differences were found in the amounts removed, probably accounted for by retention time. The caffeine and bisphenol-A were almost completely removed, higher than 90% for both compounds (bisphenol-A and caffeine) in all WWTPs. The hormones, however, had a smaller rate of removal, between 70% and 87%. It is suspected that retention time is essential for removal efficiency, together with type of treatment. In fact, the hormones, caffeine, and bisphenol-A found in the environment definitely come from untreated sewage.

The Barigüi River watershed is located in the metropolitan region of Curitiba, Southern Brazil, passing through several neighboring counties. In recent years, due to growth and disorderly occupation along the river, in addition to lack of sanitation, the Barigüi River suffered a very large inflow of untreated domestic wastewater. Current programs to monitor the watershed use traditional physical-chemical parameters. Here, the presence of some molecular tracers found in domestic effluents was investigated, such as caffeine and coprostanol at some selected sites in Barigüi River. Caffeine is highly soluble in water and its presence in water bodies is due to the disposal of untreated sewage. Caffeine is eliminated in the urine (approximately 0.5% to 10% of the consumption). The samples were collected in three campaigns, two in dry weather and another during a week in the rainy season. The results showed that caffeine concentration ranged between zero and 753.5 μg g −1 . Higher values were found on rainy days. Caffeine showed a positive correlation between BOD and nitrate; it also showed a positive correlation with coprostanol, a fecal biomarker. Finally, caffeine has been shown to be a good parameter to determine the contamination by domestic wastewater.

No abstract

The Barigui River watershed is located in the metropolitan region of Curitiba, southern Brazil, passing through several neighboring counties. In recent years, due to growth and disorderly occupation along the river, in addition to lack of sanitation, the Basin suffered a very large inflow of untreated domestic sewage. Current programs to monitor the watershed use traditional physical-chemical parameters and generally the analysis is performed only with water samples. This study analyzes the presence of fecal sterols in sediment samples. Sediment samples were collected from six points along the river and the stanols were extracted, purified and analyzed by GC-MS. Eight compounds were analyzed, among sterols and ketones. The presence of coprostanol was also identified. Coprostanol is a stanol containing a large amount in human feces. It is found near sources of pollution and can be associated with contamination by domestic sewage. The results showed high concentrations of coprostanol, ranging from 0.25 to 196 mug g( - 1). The ratio of coprostanol and epicoprostanol, was below 0.20 at most stations, indicating that the sewage discharged into the river does not undergo prior treatment. Contamination by untreated sewage was also confirmed by ratios of isomeric forms of sterols and ketones 5beta/(5beta + 5alpha).

Recebido em 20/9/06; aceito em 10/4/07; publicado na web em 25/10/07 TRANSESTERIFICATION OF VEGETABLE OILS: CHARACTERIZATION BY THIN-LAYER CROMATOGRAPHY AND DENSITY. We studied the transesterification of two vegetable oils: soybean and waste frying oil. The main problem of transesterification is related to the measurement of the ethyl ester content. In this work we used a quick analytical method for assessing the ethyl ester fraction of the purified fuel-grade transesterification products by applying a simple correlation with density. If the ester content is higher than 85% by weight the correlation allows the determination by a single density measurement. This method is suitable for control and determines the ethyl ester quickly and simply.Keywords: ethyl esters; vegetable oils, biodiesel. INTRODUÇÃOCom exceção da energia hidroelétrica e nuclear, a maioria das fontes para produção de energia são provenientes de fontes não renováveis como petróleo, gás natural e carvão 1 . Essas fontes são limitadas e seu esgotamento é certo e num futuro não muito distante 1,2 . Este fato, além do aumento no consumo e apelos ambientais, gerou uma busca incessante por alternativas para substituição dos combustíveis fósseis por fontes renováveis e menos poluidoras.Atualmente, o uso de óleos vegetais transformados (transesterificados) tem sido uma alternativa na substituição de combustíveis derivados de petróleo, além de ser uma fonte de grande impacto econômico e social. Rudolph Diesel, inventor do motor a diesel, já havia testado seu uso, todavia sem muito sucesso, possivelmente devido à alta viscosidade 1 . A transesterificação mostra-se como uma opção para melhorar o desempenho dos óleos vegetais como combustíveis, sendo um processo simples, cujo produto denominado de biodiesel, terá características similares ao óleo diesel obtido do petróleo 3 . Assim, podemos definir o biodiesel como um mono-alquil éster de ácidos graxos, derivado de fontes renováveis, tais como óleos vegetais e gorduras animais 4 , obtido através de um processo de transesterificação, no qual ocorre a transformação de triglicerídeos em moléculas menores de ésteres de ácidos graxos, segundo a reação mostrada na Figura 1. Os catalisadores mais comuns são hidróxido de sódio ou potássio, embora carbonato de potássio já tenha sido usado na tentativa de evitar uma reação paralela indesejada, a saponificação. A preparação do biodiesel também pode ser feita através de enzimas, em que as lípases são usadas como catalisadores, porém o rendimento da reação é, algumas vezes, menor 3,5 . Vários tipos de óleos vegetais já foram testados na preparação do biodiesel (canola, soja, milho, girassol, mamona, algodão etc.). O tipo de óleo a ser utilizado na produção do biodiesel depende de fatores geográficos, pois cada região produz um determinado tipo de óleo, segundo sua aptidão. Em alguns países da Europa, por exemplo, é utilizado o óleo de colza, já no Brasil, dependendo da região, pode-se produzir a partir do óleo de soja, babaçu ou mamona 2 . Destaca-se ainda o uso de óleo...