100 - <5 kDa) and characterized by several techniques. Molar ratios H/C suggested higher aromaticity for fractions F1 and F6 whereas molar ratios C/N didn´t show any differences regarding the humification degree between the fractions. The UV-Vis absorbance a254/a436 ratio showed higher results for F4 and F5, probably by less condensed features. FTIR studies showed high similarity in the functional groups in the fractions. The highest percentage of traces of Co, Al, Fe, Mn, Cu, Zn and Ni (determined by ICP-AES) was preferably complexed by fractions F3 and F4 with a greater amount of dissolved organic carbon (DOC). In addition, the exchange constants, determined by ultrafiltration method, showed complexes AHS-Fe and AHS-Al with higher stability than complexes AHS-Co in all fractions.]]>

The interaction of triclosan on (8,0) and (5,5) single wall carbon nanotube (SWCNT) was investigated using density functional calculations. The results show that the adsorption of triclosan modifies the electronic properties of pristine (8,0) and (5,5) SWCNT and induced changes in the electronic properties are dependent on the triclosan adsorption site. It was observed through binding energy that triclosan molecule interacts mainly via chemical process in parallel configuration to (8,0) SWCNT, while interaction via physical process was observed with both (8,0) and (5,5) SWCNT. It is proposed that these SWCNTs are a potential filter device due to reasonable physical interaction with triclosan molecule. Furthermore, this type of filter could be reusable, therefore after the filtering, the SWCNTs could be separated from triclosan molecule.

This paper discusses a rapid and sensitive method developed to determine trace levels of mercury in natural water samples by cold vapor atomic absorption spectrometry using a preconcentration system composed by mini-column packed with 100 mg of 2-aminothiazol modified silica gel (SiAT) coupled on-line with the spectrometer's cold vapor generator system. The optimum preconcentration conditions are also described here. The preconcentrated Hg(II) ions were eluted directly from the column to the spectrometer's cold vapor generator system using 100 µL of 2 mol L-1 hydrochloric acid and the retention efficiency achieved exceeded 95%. The enrichment factors determined were 29, 38 and 46 using 3, 4 and 5 mL of preconcentrated aqueous solutions containing 400 ng L-1 of Hg. The detection limit calculated was 5 ng L-1. The preconcentration procedure was applied to determine trace level mercury in spiked river water samples.

Este trabalho descreve a síntese e caracterização da titânia modificada pelo ligante 2-aminotiazol e sua aplicação na foto-redução de íons Hg (II) em meio aquoso. Espectros obtidos na região do infravermelho confirmaram a modificação química da matriz de titânia. A quantidade de grupos 2-aminotiazol ligados à superfície da titânia foi determinada por meio da análise de nitrogênio, utilizando-se o método de Kjeldahl. Todos os experimentos de fotoredução foram feitos em um foto-reator cilíndrico termostatizado a 298 K. O catalisador modificado, 2-aminotiazol titânia (TiAT), apresentou maior capacidade de foto-redução dos íons Hg(II) nos valores de pH estudados (3, 7 e 9). Além disso, os estudos de sorção mostraram que o TiAT apresentou um menor tempo de equilíbrio e uma maior capacidade de sorção dos íons Hg(II), demonstrando que o processo de sorção desempenha um papel fundamental no mecanismo de foto-redução.This work describes the synthesis and characterization of 2-aminothiazole-modified titania and its application on Hg (II) photoreduction in aqueous medium. Infrared spectroscopy confirmed the chemical modification of the titania matrix. The number of 2-aminothiazole groups attached to the titania was determined by Kjeldahl's method. The photocatalytic experiments were carried out in a cylindrical photoreactor thermostatted at 298 K. The resulting modified photocatalyst 2-aminothiazole titania (TiAT) revealed an enhance in the Hg (II) photoreduction capacity at studied pH values (3, 7 and 9). In addition, sorption studies showed that the photocatalyst TiAT presented a lower equilibrium time and a higher sorption capacity of Hg(II) ion, demonstrating that sorption plays a fundamental role in the photoreduction mechanism.Keywords: TiO 2 , 2-aminothiazole, photocatalysis, 3-chloropropyltrimethoxysilane IntroductionFor the past few decades, growing interest has been demonstrated in mercury treatment in aqueous medium due to its toxic, bioaccumulative properties and because of its resistance to biological or chemical degradation in the environment, as is the case of many organic pollutants (e.g. phenol and its derivatives). 1,2 Mercury and its compounds are often converted by bacteria to more toxic species, such as methylmercury, representing a potential risk to human health and to fish-consuming animals. 3 The major source of mercury pollution in aquatic environments is industrial and consists of products such as chloralkali, paint, catalysts used in the metallurgical, pharmaceutical, chemical and petrochemical industries, in electronics, cosmetics, thermometers, gauges, and batteries, as well as agricultural products such as pesticides, fungicides, herbicides, insecticides and bactericides. 4 Various physical and chemical methods have been used in the removal of mercury from water and wastewater streams. However, these processes are inefficient, generating secondary wastes in the form of by-products that must often be disposed of as hazardous. The most promising methods of treatment include sorption, ion exchang...

Este artigo descreve os resultados da fotodegradação de três tipos de fluidos de corte solúveis e emulsionavéis em meio aquoso, usando TiO 2 como catalisador em suspensão e radiação UV. O TiO 2 mostrou ser um catalisador efetivo na degradação dos fluidos de corte investigados. A velocidade de degradação depende do pH e da natureza dos fluidos. O melhor desempenho do catalisador foi observado em pH = 8,0 para todos os fluidos, quando mais de 70% da carga orgânica foi decomposta. This paper describes results of the photo-degradation of three types of soluble and emulsive cutting fluids in an aqueous medium, using TiO 2 as catalyst in suspension and UV radiation. The TiO 2 proved to be an effective catalyst for the degradation of the cutting fluids investigated. The degradation rate depends on pH and nature of the fluids. The best performance of catalyst was observed at pH 8.0 for all the fluids when most of 70% of the organic load was decomposed.