Browsing by Author "Trindade, Tito"
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- Biological synthesis of nanosized sulfide semiconductors: current status and future prospectsPublication . Costa, João Pinto da; Girão, Ana Violeta; Trindade, Tito; Costa, Maria Clara; Duarte, Armando; Rocha-Santos, TeresaThere 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 systemsPublication . Costa, J. P. da; Girão, Ana Violeta; Lourenço, J. P.; Monteiro, O. C.; Trindade, Tito; Costa, Maria ClaraThis 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.
- Integrated synthesis of nanosized semiconductors in a bioremediation system for the treatment of AMD using biologically produced sulfidePublication . Costa, J. P. da; Girão, Ana Violeta; Lourenço, J. P.; Monteiro, O. C.; Trindade, Tito; Costa, Maria ClaraThe use of sulfate-reducing bacteria in bioremediation process for the treatment of afluents with high-content of sulfate and metal generates an excess of sulfide.
- Synthesis of nanocrystalline ZnS using biologically generated sulfidePublication . Costa, J. P. da; Girão, Ana Violeta; Lourenço, J. P.; Monteiro, O. C.; Trindade, Tito; Costa, Maria ClaraThis work describes the synthesis of ZnS powders in high yield and via a straightforward process, under ambient conditions (temperature and pressure), by adding to aqueous zinc (II) a nutrient solution containing biologically generated sulfide from sulfate-reducing bacteria (SRB). The powders obtained as above were composed mainly of ZnS (sphalerite) nanoparticles (NP's) exhibiting a spheroidal morphology (20–30 nm). The NP's morphological properties and crystalline phase were not markedly altered by the SRB growth media composition neither by the presence of bacterial cells. The relevance of this method to obtain ZnS supported solid substrates has been demonstrated by performing the synthesis in the presence of TiO2 and SiO2 submicron particles.
- Use of biogenic sulfide for the synthesis of CuS nanocrystals and nanocompositesPublication . Pinto da Costa, João; Girão, Ana Violeta; Lourenço, J. P.; Monteiro, O. C.; Trindade, Tito; Costa, Maria ClaraDuring the metabolism of organic matter (CH2O), sulfate-reducing bacteria (SRB) use sulfate as the terminal electron acceptor, resulting in the production of H2S. This biologically generated sulfide, in the presence of metal ions, can be used for metal precipitation (Bhagat et al., 2004). The use of SRB in bioremediation processes, namely, in the reduction of highcontent sulfate and metal effluents, is well documented (Costa and Duarte, 2005; Garcia et al., 2001). Nevertheless, the process generates an excess of sulfide and the elimination of the sulfide in excess and disposal of the metal sulfides produced are also problems that need to be carefully addressed. Copper monosulfide (CuS) has gained considerable attention in material science due to its excellent potential in catalysis (Mallick et al., 2007), optical functionality (Liz-Marzan, 2006) and electronic functionalities (Kamat, 2002).