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Recovery of gold(0) nanoparticles from aqueous solutions using effluents from a bioremediation process
Publication . Assunção, Ana; Vieira, Bernardete; Lourenço, J. P.; Costa, Maria Clara
The use of biological processes with the aim of the recovery of gold from low-concentration solutions derived from leaching of secondary sources is gaining increasing importance owing to the scarcity of the primary resources and the economic and environmental advantages usually presented by these methods. Thus, the addition in batch and continuous processes of different solutions containing biogenic sulphide, which was generated by the activity of sulphate-reducing bacteria (SRB), to gold(III) solutions was investigated for that purpose. In the batch experiments, AuS nanoparticles with sizes of between 6 and 14 nm were obtained (corresponding to 100% removal of Au(III) from solution) if the biogenic sulphide was generated in a typical nutrient medium for SRB, whereas Au(0) nanoparticles with sizes of below 8 nm were obtained (corresponding to 62% removal of Au(III)) if effluent from a SRB bioremediation process for treating acid mine drainage (AMD) was used instead. These results stimulated the development of a continuous process of addition, in which two sulphide-rich effluents, which resulted from a SRB bioremediation process for treating two types of AMD (from a uranium mine and a polysulphide mine), were tested. In both cases, Au(0) nanoparticles with sizes of between 6 and 15 nm were mainly obtained, and the percentage removal of Au(III) from solution ranged from 76% to 100%. The processes described allow the simultaneous treatment of AMD and recovery of metallic gold nanoparticles, which are a product with a wide range of applications (e.g., in medicine, optical devices and catalysis) and high economic value. The synthesis process described in this work can be considered as novel, because it is the first time, to our knowledge, that the use of effluent from a SRB bioremediation process has been reported for the recovery of gold(III) as gold(0) nanoparticles.
A bridge between liquid-liquid extraction and the use of bacterial communities for palladium and platinum recovery as nanosized metal sulphides
Publication . Assunção, Ana; Matos, Ana; Costa, Ana M. Rosa da; Candeias, Antonio; Costa, Maria Clara
The Platinum Group Metals (PGM) are rare in the Earth's crust and in the past years their use had a considerable expansion limiting their availability, which justifies PGM's high commercial value and demand. Therefore, PGM recovery from secondary sources is very important from both economic and environmental points of view. In recent years, several methods for PGM removal have been investigated. Our research group has been studying the removal/recovery of PGM using both chemical (liquid liquid extraction) and biological methods (using anaerobic bacterial communities).The aim of this study was to combine these two chemical and biological approach technologies, for PGM recovery. For that purpose, Pd(II) and Pt(IV) present in aqueous phases, were extracted to organic phases composed by N,N'-dimethyl-N,N'-dicyclohexylsuccinamide (DMDCHSA) and N,N'-dimethyl-N,N'-dicyclohexyltetradecylmalonamide (DMDCHTDMA) in 1,2-dichloroethane, respectively, with an extraction efficiency of 79% for Pd(II) and 99% for Pt(IV). The metals in the loaded organic phases were then stripped with seawater, a low-cost solution largely available in nature, with efficiencies of 100% for Pd and 86% for Pt. Finally, the metals were precipitated and recovered using metabolic products produced by a community enriched for sulphate-reducing bacteria. The palladium precipitated completely, while 86% of platinum was precipitated. During the precipitation process sulphide concentration in the solution decreased and the analysis of the precipitates was consistent with the formation of nanosized PdS and PtS2.To our knowledge, this research shows, for the first time, the potential of combining liquid liquid extraction with the use of bacteria aiming platinum and palladium recovery, as metal sulphides, from aqueous media. (C) 2016 Elsevier B.V. All rights reserved.
Biological synthesis of nanosized sulfide semiconductors: current status and future prospects
Publication . Costa, João Pinto da; Girão, Ana Violeta; Trindade, Tito; Costa, Maria Clara; Duarte, Armando; Rocha-Santos, Teresa
There have been extensive and comprehensive reviews in the field of metal sulfide precipitation in the context of environmental remediation. However, these works have focused mainly on the removal of metals from aqueous solutions-usually, metal-contaminated effluents-with less emphasis on the precipitation process and on the end-products, frequently centering on metal removal efficiencies. Recently, there has been an increasing interest not only in the possible beneficial effects of these bioremediation strategies for metal-rich effluents but also on the formed precipitates. These metal sulfide materials are of special relevance in industry, due to their optical, electronic, and mechanical properties. Hence, identifying new routes for synthesizing these materials, as well as developing methodologies allowing for the control of the shape and size of particulates, is of environmental, economic, and practical importance. Multiple studies have shown proof-of-concept for the biological synthesis of inorganic metallic sulfide nanoparticles (NPs), resorting to varied organisms or cell components, though this information has scarcely been structured and compiled in a systematic manner. In this review, we overview the biological synthesis methodologies of nanosized metal sulfides and the advantages of these strategies when compared to more conventional chemical routes. Furthermore, we highlight the possibility of the use of numerous organisms for the synthesis of different metal sulfide NPs, with emphasis on sulfate-reducing bacteria (SRB). Finally, we put in perspective the potential of these methodologies in the emerging research areas of biohydrometallurgy and nanobiotechnology for the uptake of metals in the form of metal sulfide nanoparticles. A more complete understanding of the principles underlying the (bio)chemistry of formation of solids in these conditions may lead to the large-scale production of such metal sulfides, while simultaneously allowing an enhanced control over the size and shape of these biogenic nanomaterials.
Green synthesis of covellite nanocrystals using biologically generated sulfide: potential for bioremediation systems
Publication . Costa, J. P. da; Girão, Ana Violeta; Lourenço, J. P.; Monteiro, O. C.; Trindade, Tito; Costa, Maria Clara
This work describes the synthesis of CuS powders in high yield and via an environmentally friendly and straightforward process, under ambient conditions (temperature and pressure), by adding to aqueous copper (II) a nutrient solution containing biologically generated sulfide from sulfate-reducing bacteria (SRB). The powders obtained were composed of CuS (covellite) nanoparticles (NPs) exhibiting a spheroid morphology (<5 nm). The relevance of this method to obtain CuS supported solid substrates has been demonstrated by performing the synthesis in the presence of TiO2 and SiO2 submicron particles. We further extended the work carried out, which substantiates the potential of using biogenic sulfide for the production of covellite nanocrystals and composites, using the effluent of a bioremediation column. Hence, such process results in the synthesis of added value products obtained from metal rich effluents, such as metallurgical and industrial ones, or Acid Mine Drainage (AMD), when associated with bioremediation processes.

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Funding agency

Fundação para a Ciência e a Tecnologia

Funding programme

3599-PPCDT

Funding Award Number

PTDC/AAG-TEC/2721/2012

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