resumo
This research was undertaken to determine the potential of biologically obtained ZnS-TiO2 nanocomposites to be used as catalysts in the photodegradation of organic pollutants, namely, Safranin-T. The photocatalysts were prepared by modifying the surface of commercial TiO2 particles with naturally produced ZnS, using sulfide species produced by sulfate-reducing bacteria and metal contaminated wastewaters. Comparative studies using powder X-ray diffraction (XRD) and scanning electron microscopy (SEM), prior and after photodegradation, were carried out in order to monitor possible structural and morphological changes on the particles. Adsorption properties and specific areas were determined by the Brunauer-Emmet-Teller (BET) method. The final solutions were characterized by UV-Vis and chemical oxygen demand (COD) content in order to determine Safranin-T concentration and toxicity. The influence of the catalyst amount, initial pH and dye concentration was also evaluated. Finally, the efficiency of the precipitates as catalysts in sunlight-mediated photodegradation was investigated, performing two scale experiments by using different volumes of dye-contaminated water (150mL and 10 L). All tested composites showed potential to be used as photocatalysts for the degradation of Safranin-T, although the ZnS-TiO2_0.06 composite (0.06g of TiO2 per 50mL of the zinc solution) was the most effective. This substantiates the applicability of these biologically obtained materials as efficient photocatalysts for the degradation of organic pollutants, in laboratorial conditions and under direct sunlight.
palavras-chave
HETEROGENEOUS PHOTOCATALYTIC DEGRADATION; AZO DYES; NANOCRYSTALLINE TIO2; CONTINUOUS-MODE; METHYLENE-BLUE; DEGUSSA P25; RHODAMINE-B; WASTE-WATER; CONGO-RED; REMOVAL
categoria
Engineering; Environmental Sciences & Ecology
autores
da Costa, JP; Girao, AV; Monteiro, OC; Trindade, T; Costa, MC
nossos autores
Ana Violeta Girão
Investigador Júnior
João Miguel Martins Novaes Pinto da Costa
Bolseiro de investigação
Tito Trindade
Professor CatedráticoGrupos
G1 - Materiais Porosos e Nanossistemas
G3 - Materiais Eletroquímicos, Interfaces e Revestimentos
agradecimentos
Funding for this research from Fundacao para a Ciencia e a Tecnologia (FCT) through a PhD grant (SFRH/BD/43784/2008) and through project PTDC/AAG-TEC/2721/2012 is acknowledged. Ana V. Girao also thanks FCT for the Post-Doc grant (SFRH/BPD/66407/2009).