Adilson Cândido da Silva

Nanostructured δ-FeOOH: a novel photocatalyst for water splitting

We report on the first use of nanostructured δ-FeOOH as a promising photocatalyst for hydrogen production. The high surface area, interparticle mesoporosity, small particle size and band gap energy in the visible region make nanostructured δ-FeOOH a suitable candidate for use as a photocatalyst.

Enhanced photocatalytic hydrogen generation from water by Ni(OH)2 loaded on Ni-doped δ-FeOOH nanoparticles obtained by one-step synthesis

Ni(OH)2 loaded on Ni-doped δ-FeOOH photocatalysts were prepared by a simple and low-cost one-step precipitation method. The effect of Ni(OH)2 nanoparticles and Ni2+ doping on the photocatalytic hydrogen production rates by δ-FeOOH in aqueous suspension was investigated. The results showed that the photocatalytic H2-production activity of δ-FeOOH was significantly enhanced by doping with Ni2+ ions and by loading Ni(OH)2 on its surface. The maximum H2-production was obtained for the sample with 20 wt% Ni, which provided 5746 μmol h−1 g−1. This high photocatalytic H2-production is due to the combined effects of Ni2+ doping and Ni(OH)2 loaded on the δ-FeOOH surface. The Ni2+ doping increased the conductivity and charge transfer in δ-FeOOH, whereas the Ni(OH)2 improved the charge separation in the δ-FeOOH and, consequently, the photocatalytic H2-production activity.

A novel floating photocatalyst device based on cloth canvas impregnated with iron oxide

In this paper an innovative and versatile design for a catalytic photoreactor is presented. The photoreactor is based on a floating Polypropylene non-woven fabric canvas (NWF) impregnated with particles of a mixture of iron oxides and oxyhydroxides adhered to the surface of microfibers. The canvas was characterized with different techniques including Mossbauer spectroscopy, Raman scattering, FTIR, and SEM. UV-Vis spectroscopy showed that the impregnated particles presented an average gap of 2.2 eV. The activity and efficiency of the photocatalyst was tested by photodegradation of rhodamine-B (Rh-B) and the results showed that the floating photocatalyst has a high catalytic activity and maintains its efficiency even after five reuse tests at intervals of 90 min with a small average residual concentration of 6.2% Rhodamine-B in each reuse cycle.

Catalytic growth of carbon nanofibers on Cr nanoparticles on a carbon substrate: adsorbents for organic dyes in water

We have produced carbon nanofibers (CNFs) using leather waste that had been tanned with a chromium bath, and when dried contained Cr2O3. Suitable reduction processing produced a carbon substrate with supported nanoparticles of chromium metal. Powder X-ray diffraction showed that the Cr2O3 is reduced on the carbon surface to produce CrC and metal Cr, which is the effective catalyst for the CNFs growth. The CNF arrays were confirmed by TEM images. Raman data revealed that the synthesized CNFs have a poor-quality graphite structure which favors their use in adsorption processes. These CNFs presented higher affinity to adsorb anionic dyes, whereas the cationic dyes are better adsorbed on the carbon substrate. The low-cost and availability of the carbon precursor makes their potential use to produce CNFs of interest.

Processo de transferência de tecnologia da universidade para a indústria: estudo de caso envolvendo a conversão de glicerol

Currently, public policy has encouraged innovation in universities and also transference of technology to the industry. Another important stage to be considered would be the registration or filing of a patent and the economical viability study. Government programs, such as the innovation incentive program, among others, should facilitate popularization and promote interest by industry. In this work we described the steps, from the conception of the idea to the scale up going through its interest by the industry. The case study is about the glycerol conversion utilizing modified niobia as catalysts.

Adsorption of Caffeine on Activated Carbon Obtained from Green Coconut Waste

In this study activated carbon was produced using green coconut shell as the carbon source. Furthermore, caffeine adsorption behavior in the produced material was studied, as a function of temperature, through the adsorption isotherms and their thermodynamic parameters. For this, the green coconut shell powder was subjected to the activation process, involving impregnation with phosphoric acid solution followed by pyrolysis in a muffle furnace. The adsorption experiments at four temperatures, 25, 35, 45 and 55°C, were studied with five aqueous solutions of different caffeine concentrations maintaining the same agitation rate (150 rpm). Langmuir and Freundlich equations were employed for thermodynamic equilibrium, the data adjusting better to the Langmuir model. The thermodynamic parameters such as entropy change, enthalpy change and Gibbs free energy variation were calculated from the linear equation of the Van’t Hoff. The results showed that caffeine adsorption in the activated carbon is a spontaneous and exothermic process, and the amount of caffeine adsorbed increases according to the concentration at a constant temperature, reaching values close to 170 mg g-1. The results demonstrated the potential of green coconut waste material as feedstock to obtain activated carbon, as well as for the treatment of wastewater containing emerging contaminants.

An unusually thermally stable magnetite from a niobium mine in Brazil

Abstract Magnetite-rich waste from a niobium mine near Araxá, State of Minas Gerais, Brazil, was heated to 500ºC and 1000ºC under an O2 atmosphere. The original waste and its oxidized products were characterized by energy-dispersive X-ray spectroscopy (EDS), X-ray powder diffraction (XRD), room-temperature 57Fe Mössbauer spectroscopy, thermogravimetric analysis (TG) and temperature-programmed reduction (TPR). Semiquantitative analyses by EDS and quantitative chemical analyses showed the waste to be constituted primarily of Fe with minor amounts of Ti, Ba, Al, Si, Nb, Mn, S and P. Mössbauer and XRD showed the waste to consist predominantly of magnetite and hematite. The magnetite content decreases when the temperature increases due to its direct conversion to hematite. However, at 500ºC only 10 wt.% of original magnetite was converted to hematite, confirming the high stability of this magnetite, which could still be detected at 1000ºC. The TG profile shows no significant weight gain on heating, indicating a high stability of the magnetite. The TPR profiles show that the hematite in the waste is sintered after treatment at 1000ºC and the reduction peaks are consequently shifted to higher temperatures. This high thermal stability is attributed to a moderate isomorphous replacement of Fe by other cations present in the Nb mining waste.