Remoção de Carbofurano em Água Empregando Resíduos Agroindustriais como Adsorventes

In this study aimed to evaluate the possibility of using industrial boiler ash and rice husk ash in removing the commercial pesticide (carbofuran) in aqueous solution. These solids were collected in the Barreiras/BA, were heat treated and characterized by XRD and FT-IR. The adsorption experiments were performed in batch and the carbofuran removal was quantified using the spectrophotometry in the UV region. XRD data showed high silica content in boiler ash, which was reinforced by FT-IR analyses, showing the band FT-IR associated with presence of silica. In the FT-IR analysis of rice husk ash, this band relative to silica also were observed. The potential of adsorption of the ash industrial boiler and rice husk ash was verified obtaining significant results in the removal of carbofuran at low concentrations (2 mg/L), showing 100% of removal of pesticides from 720 min, used the ash industrial boiler, giving these materials a promising character as adsorbents. In the kinetic study of carbofuran adsorption, the mechanism of pseudo-second-order was better adjusted using the RHA as adsorbent, with a correlation coefficient (R2) of 0.997. The adsorption equilibrium was adjusted better to model of adsorption isotherm of Freundlich with a correlation coefficient of 0.999. DOI: http://dx.doi.org/10.17807/orbital.v1i1.71

ZrTiO4 Nanowire Growth Using Membrane-assisted Pechini Route

The high surface-to-volume ratio of nanowires makes them natural competitors as newer device components. In this regard, a current major challenge is to produce quasi-one-dimensional nanostructures composed of well-established oxide-based materials. This article reports the synthesis of ZrTiO4 nanowires on a silicon (100) wafer in a single-step deposition/thermal treatment. The template-directed membrane synthesis strategy was associated with the Pechini route and spin-coating deposition technique. ZrTiO4 nanowires were obtained at 700 °C with diameters in the range of 80-100 nm. FEGSEM images were obtained to investigate ZrTiO4 nanowire formation on the silicon surface and energy dispersive X-ray detection (EDS) and X-ray diffraction (XRD) analyses were performed to confirm the oxide composition and structure. DOI: http://dx.doi.org/10.17807/orbital.v1i1.711 &nbsp

Rice Husk Ash Modified with Vanadium Pentoxide

Rice husk collected in Barreiras City, Bahia, Brazil was converted to rice husk ash (RHA) by acidic or basic leaching, followed by calcination. The resulting RHA was modified with vanadium pentoxide (2, 5, or 10 mass% of V2O5).  The modified RHA samples were characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). RHA exhibited FTIR bands associated with silica. After modification of acid-leached RHA with vanadium, the XRD data indicated the formation of V2O5 phases. Base-leached RHA modified with vanadium pentoxide showed the presence of the V2O5 phase only in the sample containing 10 mass% V2O5. The FTIR data indicated the formation of cristobalite, where bands associated with Si-O-V interactions were observed only for the sample with 10 mass% V2O5 prepared with acid-leached RHA. DOI: http://dx.doi.org/10.17807/orbital.v9i2.91

ZrTiO4 Nanowire Growth Using Membrane-assisted Pechini Route

The high surface-to-volume ratio of nanowires makes them natural competitors as newer device components. In this regard, a current major challenge is to produce quasi-one-dimensional nanostructures composed of well-established oxide-based materials. This article reports the synthesis of ZrTiO4 nanowires on a silicon (100) wafer in a single-step deposition/thermal treatment. The template-directed membrane synthesis strategy was associated with the Pechini route and spin-coating deposition technique. ZrTiO4 nanowires were obtained at 700 °C with diameters in the range of 80-100 nm. FEGSEM images were obtained to investigate ZrTiO4 nanowire formation on the silicon surface and energy dispersive X-ray detection (EDS) and X-ray diffraction (XRD) analyses were performed to confirm the oxide composition and structure. DOI: http://dx.doi.org/10.17807/orbital.v1i1.711

Remoção de Carbofurano em Água Empregando Resíduos Agroindustriais como Adsorventes

In this study aimed to evaluate the possibility of using industrial boiler ash and rice husk ash in removing the commercial pesticide (carbofuran) in aqueous solution. These solids were collected in the Barreiras/BA, were heat treated and characterized by XRD and FT-IR. The adsorption experiments were performed in batch and the carbofuran removal was quantified using the spectrophotometry in the UV region. XRD data showed high silica content in boiler ash, which was reinforced by FT-IR analyses, showing the band FT-IR associated with presence of silica. In the FT-IR analysis of rice husk ash, this band relative to silica also were observed. The potential of adsorption of the ash industrial boiler and rice husk ash was verified obtaining significant results in the removal of carbofuran at low concentrations (2 mg/L), showing 100% of removal of pesticides from 720 min, used the ash industrial boiler, giving these materials a promising character as adsorbents. In the kinetic study of carbofuran adsorption, the mechanism of pseudo-second-order was better adjusted using the RHA as adsorbent, with a correlation coefficient (R2) of 0.997. The adsorption equilibrium was adjusted better to model of adsorption isotherm of Freundlich with a correlation coefficient of 0.999. DOI: http://dx.doi.org/10.17807/orbital.v1i1.71

Rice Husk Ash Modified with Vanadium Pentoxide

Rice husk collected in Barreiras City, Bahia, Brazil was converted to rice husk ash (RHA) by acidic or basic leaching, followed by calcination. The resulting RHA was modified with vanadium pentoxide (2, 5, or 10 mass% of V2O5).  The modified RHA samples were characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). RHA exhibited FTIR bands associated with silica. After modification of acid-leached RHA with vanadium, the XRD data indicated the formation of V2O5 phases. Base-leached RHA modified with vanadium pentoxide showed the presence of the V2O5 phase only in the sample containing 10 mass% V2O5. The FTIR data indicated the formation of cristobalite, where bands associated with Si-O-V interactions were observed only for the sample with 10 mass% V2O5 prepared with acid-leached RHA. DOI: http://dx.doi.org/10.17807/orbital.v9i2.91

Preparação e caracterização de catalisadores baseados em pentóxido de nióbio e óxido de cobre(II) aplicados em reações de esterificação e transesterificação

Tese (doutorado)—Universidade de Brasília, Instituto de Química, 2007.Os catalisadores contendo Nb O /SiO -Al O , CuO/Nb O /SiO -Al O , 2 5 2 2 3 2 5 2 2 3 Nb O /CCA (CCA=cinza de casca de arroz) cristalina ou amorfa e CuO/CCA 2 5 investigados neste estudo, foram preparados via diferentes rotas (impregnação em meio aquoso (incipiente ou evaporação) ou grafitização em meio orgânico, em variadas proporções (2, 5, 10, 15, 20 e 25 % em massa). Estes materiais foram aplicados em reações de esterificação de ácido acético com álcoois (etanol, n-butanol e iso-pentanol), esterificação de ácido oléico ou transesterificação de óleo de soja com etanol ou metanol, mostrando ótima conversão e seletividade na maioria dos processos. As caracterizações utilizadas foram: DRX, TG/DTA, FTRaman, FTIR, DRIFTS, Calorimetria, BET, RMN e CG/FID e CG/MS. Os catalisadores de Nb O /SiO -Al O foram 2 5 2 2 3 avaliados quanto à transição de fase que ocorre a cerca de 1350 C, confirmando a formação das fases ortorrômbica (T) e monoclínica (M e H), em contraste com o Nb O puro que forma somente a fase H nas mesmas 2 5 condições. O estudo destes catalisadores calcinados mostrou a forte dependência da temperatura na acidez e na estrutura. O material suportado mais ácido é amorfo, contém 10% em massa do Nb O (~ o limite da 2 5 C. Os catalisadores de monocamada) e deve ser calcinado a 300 CuO/Nb O /SiO -Al O mostraram um alto grau de influência do CuO sobre o O , sendo que a estabilidade térmica é dependente do método de Nb 2 5 preparação. Os materiais calcinados a 800 C e com alto teor de Cu e Nb mostraram a formação de óxidos mistos (CuNb O ) e possuem a monocamada 2 6 em torno de 5-10 % em massa dos óxidos de CuO e Nb O . Já os calcinados a 2 5 C, somente é observado o CuO cristalino, quando esse possui teores 300 acima de 10 % em massa. Os sistemas de Nb O /CCA amorfa ou cristalina 2 5 mostraram uma forte interação das espécies superficiais de óxido de nióbio, evidenciado pela formação das fases TT e T-Nb O , nas amostras contendo 2 5 10-25 % em massa e calcinadas a 800 C. Além disso, não mostraram a transição de fase nas curvas de TG/DTA. O catalisador mais ativo no processo de esterificação do ácido oléico contém 10 % em massa e foi calcinado a 300 C. O catalisador contendo 10 % de CuO/CCA amorfa, calcinado a 300 C, mostrou alta dispersão das espécies de cobre na superfície. ________________________________________________________________________________________ ABSTRACTO /SiO -Al O , CuO/Nb O /SiO -Al O , Catalysts comprising of Nb 2 5 2 2 3 2 5 2 2 3 Nb O /CCA (CCA=rice husk ash) crystalline or amorphous and CuO/CCA 2 5 investigated in this study were prepared by different routes (impregnation in aqueous solution (incipient or evaporation) or graftization in organic medium) (2, 5, 10, 15, 20 e 25 mass%). under different proportions These materials were applied in esterification reactions of acetic acid with alcohols (ethanol, n-butanol and isopentanol), esterification of oleic acid or transesterification of soybean oil with ethanol or methanol, showing excellent conversion and selectivities in the majority of the processes. The catalyst characterizations used were: XRD, TG/DTA, FTRAMAN, FTIR, DRIFTS, Calorimetry, BET, NMR, GC/FID and O /SiO -Al O were tested to the transition phase, GC/MS. The catalysts of Nb 2 5 2 2 3 1350 C, confirming formation of the orthorhombic (T) which occurs at about and monoclinic (M and H) phases. This is in contrast to pure Nb O that forms 2 5 only the H phase under the same conditions. The study of the calcined catalysts showed the strong dependence of the temperature on the acidity and structure. The most acidic material is amorphous, have 10 mass% of Nb o (~the limit of 2 5 C. The catalysts of the monolayer), and must be calcined at 300 CuO/Nb O /SiO -Al O showed a high degree influence of CuO over Nb O , 2 5 2 2 3 2 5 and the thermal stability is dependent on the preparation method. The materials and higher Cu and Nb loadings showed the formation of calcined at 800 °C O ), and have the monolayer around 5-10 mass% of CuO mixed-oxides (CuNb 2 6 O . When loadings are over 10 mass% and calcination is at 300 °C, and Nb 2 5 only crystalline CuO is observed. The Nb O /CCA amorphous or crystalline 2 5 showed a strong interaction of the niobium oxide surface species, evidenced by the formation of TT and T-Nb O phases in the samples with 10-25 mass% and 2 5 calcined at 800 °C. Moreover, they have not displayed the transition phase in the TG/DTA curves. The most active catalyst for the esterification of oleic acid process has 10 mass% and was calcined at 300 °C. The catalyst with 10 mass% of CuO/CCA amorphous, calcined at 300 °C showed high dispersion of copper species on the surface

Journal of Thermal Analysis and Calorimetry

p. 851–855Nb2O5 supported on SiO2–Al2O3 were prepared with a wide loading range (2, 5, 10, 15, 20 and 25 mass%) and analyzed by simultaneous thermogravimetric (TG) and differential thermal analysis (DTA). The materials presented a phase transition close to 1364°C. This phase transition was studied by XRD, FTIR and Raman spectroscopy. Amixture of orthorhombic (T) andmonoclinic (H and M) crystalline phases was evidenced in the supported samples, which is coverage dependent, in contrast to the formation of only the monoclinic phase (H and M) when pure Nb2O5 is heated under the same conditions. These results indicate the stabilization of Nb2O5 on silica-alumina surface

Catalysis Today

Acesso restrito: Texto completo. p. 106-112.Supported niobium pentoxide catalysts are active for a variety of acid and redox catalyzed reactions such as dehydration, hydrogenation and esterification. In this work, niobium pentoxide has been supported on silica–alumina using two methods: grafting in CH2Cl2 or ethanol solution with NbCl5 precursor, and impregnating in aqueous solution with ammonium niobium oxalate. XRD, TG/DTG/DTA, FTIR, DRIFTS, FT-Raman,and calorimetric titration with pyridine were used to characterize the materials. Calcination of the materials at 800 8C produced crystalline Nb2O5 (T-phase) for the samples prepared by grafting, while a mixture of T- and H-phases are formed by aqueous impregnation, indicating the higher stability of the former materials. Thermal analysis confirmed a stronger interaction of niobium oxide species on the silica–alumina surface for the grafting procedure. On the other hand, partial neutralization of hydroxyl groups occurred on the support surface by grafting process, and the neutralization reaction is practically complete at 25 wt.% of Nb2O5 by impregnation. The catalysts with about 10 wt.% of Nb2O5 prepared by aqueous impregnation reached the monolayer, while by grafting it predominates bulk Nb2O5, as demonstrated by FT-Raman. These catalysts also showed the highest acidity, when calcined at 300 8C. Based on these results, liquid phase esterification reactions of acetic acid were carried out with different alcohols (ethanol, n-butanol, and iso-pentanol). The yields were about the same, independent of the preparation method for 10 wt.% Nb2O5 catalysts. The conversions using molar ratio 2:1 (acid:alcohol) after 8 h showed good results (83, 87, and 91%, respectively) and 100% selectivity for all esters