Biossorção de metais presentes na DAM utilizando Rhodococcus opacus

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Abstract

O presente trabalho tem como objetivo avaliar a biossorção de metais presentes em uma amostra sintética de drenagem ácida de mina, determinando o tempo de equilíbrio, a quantidade de metal captado e removido e, também, as mudanças ocorridas na biomassa. Para tanto, os ensaios foram realizados mantendo-se constantes a temperatura (25ºC), o pH (2,6), a concentração de biomassa (1g.L-1) e sob agitação de 175rpm. Como biossorvente foi utilizada uma massa fixa de bactérias gram-positivas Rhodococcus opacus no estágio de morte que foi crescida em meio YMA (yeast mannitol agar), durante 24h, a 28ºC e sob agitação de 150rpm. Após o processo biossortivo as amostras foram centrifugadas: o sobrenadante foi analisado através de análise de absorção atômica e a biomassa foi caracterizada através análises de microscopia eletrônica de varredura (MEV). Os resultados mostraram que a captação máxima ocorre em torno de 1 minuto e representa 48,2mg.g-1, o que corresponde a aproximadamente 11,7% de remoção. As mudanças verificadas nas análises de MEV indicam que houve interação entre os íons metálicos e a biomassa.

Translated abstract

This study aims to evaluate metal biosorption in an acid mine drainage (AMD) synthetic sample by determining the equilibrium time, the amount of metal captured and removed, and also the biomass changes. For this, tests were performed with parameter constants: 25ºC temperature, 2.6 pH, 1g.L-1 biomass concentration, and at 175rpm shake. The gram-positive bacterium Rhodococcus opacus was used as biosorbent, after having been grown in YMA (yeast mannitol agar) for 24h at 28ºC and shaken at 150rpm. After the biosorptive process, samples were centrifuged: the supernatant was analyzed by atomic absorption and the biomass was characterized by analysis of scanning electron microscopy (SEM). The results showed that maximum uptake time occurs in about 1 minute, when the maximum uptake was 48.2mg.g-1, which corresponds to approximately to 11.7% of the total removal. The changes observed in the SEM indicate that there are interactions between metal ions and biomass.

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B Volesky, Z R Holan (1995)

Only within the past decade has the potential of metal biosorption by biomass materials been well established. For economic reasons, of particular interest are abundant biomass types generated as a waste byproduct of large-scale industrial fermentations or certain metal-binding algae found in large quantities in the sea. These biomass types serve as a basis for newly developed metal biosorption processes foreseen particularly as a very competitive means for the detoxification of metal-bearing industrial effluents. The assessment of the metal-binding capacity of some new biosorbents is discussed. Lead and cadmium, for instance, have been effectively removed from very dilute solutions by the dried biomass of some ubiquitous species of brown marine algae such as Ascophyllum and Sargassum, which accumulate more than 30% of biomass dry weight in the metal. Mycelia of the industrial steroid-transforming fungi Rhizopus and Absidia are excellent biosorbents for lead, cadmium, copper, zinc, and uranium and also bind other heavy metals up to 25% of the biomass dry weight. Biosorption isotherm curves, derived from equilibrium batch sorption experiments, are used in the evaluation of metal uptake by different biosorbents. Further studies are focusing on the assessment of biosorbent performance in dynamic continuous-flow sorption systems. In the course of this work, new methodologies are being developed that are aimed at mathematical modeling of biosorption systems and their effective optimization. Elucidation of mechanisms active in metal biosorption is essential for successful exploitation of the phenomenon and for regeneration of biosorbent materials in multiple reuse cycles. The complex nature of biosorbent materials makes this task particularly challenging. Discussion focuses on the composition of marine algae polysaccharide structures, which seem instrumental in metal uptake and binding. The state of the art in the field of biosorption is reviewed in this article, with many references to recent reviews and key individual contributions.

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Equilibrium and kinetic studies in adsorption of heavy metals using biosorbent: a summary of recent studies.

Yi Ju, Jaka Sunarso, Ayleen A Kosasih … (2009)

Distinctive adsorption equilibria and kinetic models are of extensive use in explaining the biosorption of heavy metals, denoting the need to highlight and summarize their essential issues, which is the main purpose of this paper. As a general trend, up until now, most studies on the biosorption of heavy metal ions by miscellaneous biosorbent types have been directed toward the uptake of single metal in preference to multicomponent systems. In particular, Langmuir and Freundlich models are the most common isotherms for correlating biosorption experimental data though other isotherms, which were initially established for gas phase applications, can also be extended onto biosorption system. In kinetic modeling, the pseudo-first and -second order equations are considered as the most celebrated models.