Bioleaching of hexavalent chromium from soils using acidithiobacillus thiooxidans

The continuous and growing degradation of the environment, due to several anthropogenic activities, is a main concern of the scientific community. Consequently, the development of low cost techniques to clean air, water and soils are under intense investigation. In this study, the focused problem is the soil contamination by hexavalent chromium, which is known for its several industrial applications - production of stainless steel, textile dyes, wood preservation and leather tanning - its high toxicity and mobility. Bioleaching has been presented as a low cost effective technique to decontaminate soils polluted with heavy metals. Sulphur oxidizing bacteria, like Acidithiobacillus thiooxidans, were already applied with this technique as they produce sulphuric acid, lowering the pH and promoting the dissolution of heavy metals [1, 2]. On the other hand, it also known that polythionates, generated during the oxidation process, have high reducing power. Considering this information and since few studies have been made concerning the bioleaching of hexavalent chromium from soils, this work pretended to investigate this matter. Specifically, eighteen Erlenmeyers flasks (250 mL) with a working volume of 150 mL, containing 10% ( V / V ) of inoculum (Acidithiobacillus thiooxidans DSM 504), 90% ( V / V ) of growing medium (DSM 35) and 3% ( W / V ) of contaminated soil were agitated in a rotary shaker, at 150 rpm, for 70 days. Also three controls were undertaken by sterilizing the soil and/or suppressing the inoculum. Two levels of soil contamination were evaluated within this work. This study presented bioleaching as a competitive technique in soil cleaning, as it is efficient and inexpensive

The influence of ion binding and ion specific potentials on the double layer pressure between charged bilayers at low salt concentrations

Measurements of surface forces between double-chained cationic bilayers adsorbed onto molecularly smooth mica surfaces across different millimolar salt solutions have revealed a large degree of ion specificity [Pashley et al., J. Phys. Chem. 90, 1637 (1986)]. This has been interpreted in terms of highly specific anion binding to the adsorbed bilayers. We show here that inclusion in the double layer theory of nonspecific ion binding and ion specific nonelectrostatic potentials acting between ions and the two surfaces can account for the phenomenon. It also gives the right Hofmeister series for the double layer pressure.M.B. thanks the Swedish Research Council and the German Arbeitsgemeinschaft industrieller Forschungvereinigungen Otto von Guericke e.V. AiF for financial support. E.R.A.L. and F.W.T. thank FAPERJ and CNPq the Brazilian Agencies for financial support

Morfologia dos estágios zoea e megalopa de Austinixa bragantina Coelho, 2005 (Crustacea: Brachyura: Pinnotheridae) cultivado em laboratório.

Resumo P-2325

Combined remediation technology for the reduction and bioleaching of hexavalent chromium from soils using Acidithiobacillus thiooxidans

Contamination of soils due to the release of effluents or deposition of wastes containing hexavalent chromium has been arising serious environmental problems. Therefore, the development of cost effectiveness but also ecological cleaning techniques is a matter of great concern among the scientific community. Bioremediation is attracting more and more attention due to its efficiency, low impact in the ecosystems and low cost. In particular, this study approaches a bioleaching technique using an Acidithiobacillus thiooxidans DSM504 pure culture to clean a soil contaminated with hexavalent chromium. Eight batch tests were performed in order to evaluate the effect of combined parameters: operational temperature (26ºC and Troom), hexavalent chromium concentration (50 mg kg-1 and 100 mg kg-1) and pH of the contaminant solution (2 and pHfree). The bioleaching technique herein exposed presented removal values between 33.3% and 83.3%, undergoing higher deviations due to changes on the contamination pH. Generally, it was more efficient when applied to soils contaminated with acid solutions. The lowest and highest values were both observed for operational temperatures of 26ºC and hexavalent chromium concentrations of 50 mg kg-1. Moreover, the highest value was observed for the soil contaminated with a hexavalent chromium solution of pH 2

Biodegradation assessment of a 16th century fresco from Southern Portugal

This work reports the study of the frescoes from the Casa de Fresco dos Sanches Baena in Vila Viçosa (Southeast Portugal) to allow their material characterisation, to identify the different populations of microorganisms and to assess their role in the deterioration of these paintings

Diversity and community ecology of metazoan parasites in Pimelodus ornatus (Siluriformes: Pimelodidae) from the Amazonas River in Brazil.

Este estudo investigou a comunidade de parasitos metazoários em Pimelodus ornatus do Rio Amazonas, no estado do Amapá (Brazil). De 71 peixes examinados, 70,4% estavam parasitados e um total de 147 parasitos foram coletados, entre Demidospermus sp. (Monogenea), Cucullanus pinnai (Nematoda), Procamallanus (Spirocamallanus) inopinatus e Contracaecum sp. (Nematoda) e plerocercoides de Proteocephalidae gen. sp. (Cestoda). A dominância foi de nematoides como Procamallanus (S.) inopinatus e Contracaecum sp. Os parasitos apresentaram dispersão altamente agregada e predomínio de hospedeiros infectados por uma espécie de parasito. A comunidade de parasitos foi caracteriza por baixo índice de diversidade de Shannon, baixa equitabilidade e baixa riqueza de espécies. A riqueza de espécies de parasitos, índice de diversidade de Shannon, abundância de P. (S.) inopinatus e Proteocephalidae gen. sp. apresentaram correlação positiva com o comprimento dos hospedeiros. Portanto, o tamanho dos hospedeiros teve influência sobre a comunidade e infracomunidades de parasitos, bem como sua posição intermediária na cadeia alimentar. Este é o primeiro registro de P. (S.) inopinatus e Contracaecum sp. para P. ornatus

Optimization of filament antennas using the Gauss-Newton method

The project of the Yagi-Uda antenna was optimized using the Gauss-Newton method. The optimization consisted of specifying value interval for directivity, front-to-back ratio and beamwidth and, starting from a pre-defined initial model, the best values for the length and spacing of the elements were determined. For the direct modeling, the method of moments on the integral Pocklington equation was used, which consisted of obtaining the values of directivity, front-to-back ratio and beamwidth from the length and spacing between known elements. The procedure was applied to the synthesis of Yagi-Uda antennas with five and six elements and the results were found to be as good as those obtained in the literature using other optimization methods