Browsing by Author "Monteiro, O. C."
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- 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.
- Novel titanate nanotubes-cyanocobalamin materials: Synthesis and enhanced photocatalytic properties for pollutants removalPublication . Silva, T. A.; Diniz, J.; Paixio, L.; Vieira, Bernardete; Barrocas, B.; Nunes, C. D.; Monteiro, O. C.New hybrid nanomaterials, with improved photocatalytic performance in pollutants removal, were obtained through the modification of titanate nanotubes (TNT) with a cobalt porphyrin, the cyanocobalamin, also knowing as vitamin B12 (812). The nanocrystalline TNT were produced by hydrothermal treatment and after treated with cobalamin to produce B12-TNT materials. The characterization of the new hybrid material was performed by XRD, FTIR, TEM-EDS, DRS, XPS and ICP. The results show that the immobilization of the cobalt containing specie is dependent on the point of zero charge of the TNT and no modifications on the structure and morphology were observed. No significant changes in the optical band gap were observed after B12 incorporation, but an increasing in the visible light absorption, which arises from charge transfer and d-d transitions of the cobalt, was visualized. The samples photocatalytic performance was studied for the hydroxyl radical production and the highest catalytic ability was achieved by the B12-HTNT sample. The catalytic ability of these new hybrid nanomaterials for two model pollutants photodegradation, phenol and rhodamine B (RhB) was investigated. For both pollutants, the best results were achieved using B12-HTNT with a removal of 94% of a 10 ppm RhB and 87% of a 20 ppm phenol solution in 90 min of irradiation (150 mL, 0.2 g catalyst/L). (C) 2016 Elsevier Masson SAS. All rights reserved.
- Photodegradation of chloramphenicol and paracetamol using PbS/TiO2 nanocomposites produced by green synthesisPublication . Palma, Tânia Cristina da Luz; Vieira, Bernardete; Nunes, J.; Lourenço, J. P.; Monteiro, O. C.; Costa, Maria ClaraThe present study describes the photocatalytic potential of the successfully synthesized nanocrystalline PbS/TiO2 nanocomposites in the photodegradation of chloramphenicol and paracetamol. PbS and PbS/TiO2 nanoparticles were synthesized using biological sulphide produced by sulphate-reducing bacteria in batch and in a coupled bioremediation system (upflow anaerobic packed-bed reactor) for acid mine drainage treatment, yielding near-complete metal precipitation (~ 100–99%, respectively). The PbS and PbS/TiO2 composites obtained using sulphide generated in batch have an average particle size ranging from 17 to 25 nm and 15 to 20 nm, respectively, while in bioreactor, both PbS and PbS/TiO2 particles have a similar size range from 20 to 50 nm. All the produced particles presented crystalline cubic structure. The specific surface area of TiO2 and PbS/TiO2 was estimated to be 46.559 m2/g and 38.005 m2/g, respectively. Chloramphenicol removal by photolysis was about 61% after 60 min of Hg irradiation and 36% under sunlight exposition. Chloramphenicol photodegradation using PbS/TiO2 as catalyst was successfully performed in a photoreactor (Hg medium pressure, 450 W) and under solar exposition with a high drug removal efficiency of 96% and 93% after 60 min and 240 min irradiation, respectively. Using TiO2 as a catalyst for photodegradation achieved 98% removal for both Hg and sunlight irradiation (UV index ranging 7–8) after 60 min and 240 min, respectively. Paracetamol removal by photolysis was about 18%. Drug’s photocatalytic degradation using PbS/TiO2 was successfully performed under sunlight exposition with a high removal efficiency of 93%, while in the presence of TiO2, the removal was complete, after 235 min irradiation.
- 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).