Resumo Este trabalho apresenta as propriedades de filmes finos de ZnO:Al crescidos por pulverização catódica com rádio frequência sobre substratos de poliimida para serem utilizados como eletrodos flexíveis de dispositivos optoeletrônicos. Para efeitos de comparação, os filmes também foram crescidos sobre lâminas de vidro soda-lime. Os filmes foram depositados com diversas potências de trabalho, sobre substratos mantidos à temperatura ambiente. Os efeitos da potência e da espessura nas propriedades ópticas, elétricas e estruturais do ZnO:Al foram investigados. Imagens de microscopia de força atômica revelaram que os filmes foram nanocristalinos e de baixa rugosidade. Valores de resistência de folha de 8 Ω/sq, correspondente a uma resistividade de 6x10-4 W.cm, e de transmitância de 75% na faixa do visível foram obtidos, os quais podem ser considerados satisfatórios, principalmente quando se considera que a deposição foi realizada à temperatura ambiente.

Abstract This work investigated the properties of ZnO:Al thin films produced by radio frequency magnetron sputtering onto polyimide substrates for use as flexible electrodes in optoelectronic devices. For comparison purposes, films were also grown on soda lime glass. The films were deposited with different working powers, onto substrates kept at room temperature. The effects of the power and thickness on the optical, electrical and structural properties of the films were investigated. Atomic force microscopy images revealed that the films were nanocrystalline, with low surface roughness. Values of sheet resistance and transmittance in the visible range were 8 Ω/sq (corresponding to 6x10-4 W.cm) and 75%, respectively, which can be considered satisfactory, particularly taking into consideration that deposition was carried out at room temperature.

Atualmente há uma crescente demanda no cenário mundial com relação ao tratamento de resíduos industriais, dentre estes o fenol e pilhas inutilizadas. Óxidos e cerâmicas a base de ferro, tais como ferritas são utilizadas como catalisadores no processo Fenton heterogêneo. Os processos de Fenton e foto-Fenton apresentam alta eficiência no tratamento de resíduos tóxicos utilizando catalisadores a base de ferro. Neste contexto foram desenvolvidas ferritas a partir de resíduos de pilhas inutilizadas. O uso destas ferritas como catalisadores é bastante interessante, uma vez que, são materiais ferromagnéticos podendo ser recuperados no final do processo utilizando campo magnético, evitando a liberação de Fe2+ e Fe3+ no efluente. Os resultados mostraram que a ferrita proveniente de pilhas inutilizadas e calcinada à temperatura de 500 °C apresentou estrutura correspondente a fase espinélio e magnéticas (M S= 37,04 emu.g-1) e como catalisador de fotodegradação atingiu-se 90% de remoção de fenol em pH 2,5 durante 2 h de irradiação.

Currently there is a growing global demand with respect to industrial waste treatment, among them phenol and spent batteries. Iron oxides and ceramics containing iron, such as ferrites, have been used with success as catalysts for heterogeneous Fenton process. The Fenton and photo-Fenton processes have high efficiency in treatment of toxic residue using iron as catalysts. In this respect, ferrites were developed from spent batteries. The use of these ferrites as catalysts is very interesting because these oxides are ferromagnetic and can be recovered at the end of the process using a magnetic field, avoiding the discharge of Fe2+ and Fe3+ in the environment. The results showed that the ferrite from spent batteries calcined at 500 °C presents structural of spinel phase and magnetic properties (Ms= 37.04 emu.g-1) and applied in photo-Fenton process, it was reached 90% of phenol removal at pH 2.5 with 2 h of irradiation.

Due to its low cost compared with hydroxamate and sulphonate, sodium oleate is employed in direct flotation of low-grade or waste iron ore. However, depressants are being studied. This work shows the influence of the depressant sodium silicate on hematite and quartz flotation with sodium oleate as a collector. Microflotation tests were per-formed in Hallimond tube at pH values 7 and 9, and the zeta potentials of both minerals were determined in the absence and presence of sodium silicate. The sodium silicate was a more efficient depressant for quartz than for hematite, and a selective separation between the two minerals is possible for low reagent concentrations. The zeta potentials of both minerals were shifted to lower values due the specific adsorption of anionic species of sodium silicate onto their surfaces

In this paper, we present the results and a discussion of microflotation tests performed with manganese minerals (rhodonite and rhodochrosite) and quartz mineral, using sodium oleate as the collector. We also explore the influence of water glass (sodium silicate) as a depressant in the recovery of these minerals with sodium oleate. Potential zeta determinations were carried out with the three minerals conditioned with deionised water and with the previously mentioned reagents. It was found that, at a pH of 9, the recoveries of rhodonite and quartz were maximised, and for the rodhocrhosite mineral, the maximum recovery was achieved at pH 11. The water glass at pH 9 was more efficient in depressing quartz than rhodonite, especially for smaller concentrations, whereas the flotation response of rhodochrosite was only slightly affected at both pH 9 and pH 11. The potential zeta curves indicate that the IEP of rhodonite (pH=2.8) is similar to values reported in the literature, whereas the IEP values of quartz (pH=2.2) and rhodochrosite (pH=10.8) differ slightly from those in the literature. The zeta potentials of rhodonite, quartz and rhodochrosite in the presence of sodium oleate and water glass become more negative in a basic medium. Finally, based on the experimental results with a collector of sodium oleate and a depressant of water glass, some inferences on the adsorption mechanisms of these reagents on rhodonite, quartz and rhodochrosite surfaces are made.