Aplicabilidade das cinzas da casca de arroz

Currently, the accumulation of rice husk is a serious environmental problem. The burning of rice husk generates a considerable volume of ash, that falls to the ground and gets into the air and the rivers, causing a disequilibrium in the ecosystem. This motived research into solutions that aim to exploit the husks for energy generation and the ashes for developing diverse technological products. This work presents the possibilities of using rice husks and their ashes after burning.

Dispositivos poliméricos eletroluminescentes

Here we present an overview of electroluminescent devices that use conjugated polymers as the active media. The principal components of the devices are described and we show some examples of conjugated polymers and copolymers usually employed in polymeric light emitting devices (PLED). Some aspects of the photo and electroluminescence properties as well as of the energy transfer processes are discussed. As an example, we present some of the photophysical properties of poly(fluorene)s, a class of conjugated polymers with blue emission.

Adsorção de íons dicromato nos compósitos celulose/ZrO2.nH2O preparados pelos métodos da precipitação convencional e em solução homogênea

This article describes the preparation and characterization of the cellulose/ hydrated zirconium oxide composites prepared by conventional precipitation (PC) and homogeneous solution precipitation (PSH) methods. The composite obtained by the PC method was prepared by using an ammonia solution as the precipitating agent, while the composite obtained by the PSH method was prepared by using urea as the precipitating agent. The adsorption of dichromate ions on the composites was studied using factorial design 2³. The variables were: initial concentration, agitation time and mass of the composite. The data obtained agree better for the composite obtained by the PC method.

Estudo comparativo entre sílica obtida por lixívia ácida da casca de arroz e sílica obtida por tratamento térmico da cinza de casca de arroz

A comparison between silica by acid leaching of rice husk (RH) and silica obtained from thermal treatment of rice husk ash (RHA) is presented. The best leaching results were obtained using 10% hydrochloric acid followed by washing with water. The alternative method, calcination of RHA at 700 ºC for 6 h followed by grinding for 80 min, was more effective. Silica obtained from RH was about 97% amorphous, had a 17.37 µm mean particle size, and a specific surface area of 296 m²/g. On the other hand, for silica obtained from RHA the values were about 95% amorphous material 0.68 µm, and 81 m²/g.

Constituintes químicos da casca do caule de Amburana cearensis A.C. Smith

The phytochemical analysis of the ethanol extract trunk bark of Amburana cearensis allowed the isolation and identification of twelve constituents: coumarin, sucrose, two phenol acids (vanillic acid and protocatechuic acid), five flavonoids (afrormosin, isokaempferide, kaempferol, quercetin and 4'-methoxy-fisetin), a phenol glucoside (amburoside A) and a mixture of glucosilated b-sitosterol and stigmasterol. Their structures were elucidated by spectroscopic methods such as IR, MS, ¹H and 13C NMR, including uni and bidimensional techniques, in addition to comparison with literature data.

Planejamento estatístico de experimentos como uma ferramenta para otimização das condições de biossorção de Cu(II) em batelada utilizando-se casca de nozes pecã como biossorvente

In order to reduce the total number of experiments for achieving the highest amount of adsorbed Cu2+ (qmax) using pecan nutshells (Carya illinoensis) as biosorbent, a full 2(4) factorial design with two central points was carried out (mass of biosorbent- m, pH, initial metallic ion concentration- C0, time of contact- t). In order to continue the optimization of the system, a central composite surface analysis design with two factors and five central points was carried out. The maximum amount of Cu2+ taken up by the pecan nutshells was 20 mg g-1. These results were confirmed by determining a Cu2+ isotherm using the best conditions attained by the statistical design of experiments.

Transformação de triglicerídeos em combustíveis, materiais poliméricos e insumos químicos: algumas aplicações da catálise na oleoquímica

The use of biomass as raw-material for obtaining chemicals, polymers and fuels is emerging as a clever alternative solution for the increasing energy demand, environmental awareness and petroleum shortage. In this work, some attempts in order to develop catalytic systems suitable for triglyceride transformation into fuels, polymers and intermediates are reviewed.

Compósitos magnéticos baseados em hidrotalcitas para a remoção de contaminantes aniônicos em água

In this work the adsorption features of hydrotalcites (Al, Mg- CO3) and the magnetic properties of iron oxides have been combined in a composite to produce a magnetic adsorbent. These magnetic composites can be used as adsorbents for anionic contaminants in water and subsequently removed from the medium by a simple magnetic process. The magnetic hydrotalcites were characterized by XRD, magnetization measurements, N2 adsorption isotherms and Mössbauer spectroscopy. These magnetic adsorbents show remarkable adsorption capacity for anionic contaminants in water.

Uso da casca de coco verde como adsorbente na remoção de metais tóxicos

Green coconut shells were treated with acid, base and hydrogen peroxide solutions for 3, 6, 12 and 24 h for removing toxic metals from synthetic wastewater. The removal of ions by the adsorbent treated with 0.1 mol L-1 NaOH/ 3h was 99.5% for Pb2+ and 97.9% for Cu2+. The removal of Cd2+, Ni2+, Zn2+, using adsorbent treated with 1.0 mol L-1 NaOH/3 h, was 98.5, 90.3 and 95.4%, respectively. Particle size, adsorbent concentration and adsorption kinetics were also studied. An adsorbent size of 60-99 mesh and a concentration of 30-40 g/L for 5 min exposure were satisfactory for maximum uptake of Pb2+, Ni2+, Cd2+, Zn2+ and Cu2+ and can be considered as promising parameters for treatment the aqueous effluents contaminated with toxic metals.

Preparação e caracterização de carvão ativado quimicamente a partir da casca de arroz

This work consists in a study about the chemical activation of charred rice hulls using NaOH as the activation agent. The influence of the naturally-occurring silica was particularly evidenced. X-ray diffraction patterns showed the formation of sodium carbonate and silicates in the activated samples, whereas thermogravimetric curves revealed a strong reduction in the ash content of these samples after washing with water. Nitrogen adsorption data indicated a microporosity development only in the washed samples, with BET surface area values of 450 and 1380 m²/g achieved for the samples activated at 800 °C starting from the precursor with or without silica, respectively.

Reutilização de efluente de tingimentos de fibras acrílicas pós-tratamento fotoeletroquímico

On a laboratory scale effluents were produced from bichromic dyeing of acrylic fabrics with the basic dyes Blue Astrazon FGGL 300% and Yellow Gold Astrazon GL 200%. The residual dyeing baths were subjected to a photoelectrochemical treatment and reused in a second dyeing process. In the reutilization study, dyeings with treated effluent were compared with standard dyeings with distilled water. The results of dyeings using 100% of treated effluent were unsatisfactory, but the substitution of 10 to 30% of the treated effluent by distilled water resulted in reduced and more acceptable values for difference in colour intensity (ΔE) between 1.86 and 0.3.

Obtenção de filmes finos de TiO2 nanoestruturado pelo método dos precursores poliméricos

This work focuses in optimizing setup for obtaining TiO2 thin films by polymeric precursor route due to its advantages on stoichiometric and morphological control. Precursor stoichiometry, synthesis pH, solids concentration and rotation speed at deposition were optimized evaluating thin films morphology and thickness. Thermogravimetry and RMN were applied for precursor's characterization and AFM, XRD and ellipsometry for thin films evaluation. Results showed successful attainment of homogeneous nanocrystalline anatase TiO2 thin films with outstanding control over morphological characteristics, mean grain size of 17 nm, packing densities between 57 and 75%, estimated surface areas of 90 m²/g and monolayers thickness within 20 and 128 nm.

Caracterização de cinza obtida por combustão de casca de arroz em reator de leito fluidizado

The rice husk combustion in a bubbling and atmospheric fluidized bed reactor was investigated. This paper presents the rice husk ash characterization employing the techniques of X-ray diffraction (XRD), X-ray fluorescence (XRF), and scanning electron microscopy (SEM) among others. After combustion, a rice husk ash containing 93% amorphous silica and <3% unburned char was produced. Methods usually applied to fixed bed considering external sources of energy and high reaction times were employed. Thus, the potential of this type of reactors with respect to speed, continuity and self-sufficiency energy of the process was shown.

Hidrogenação eletrocatalítica de substratos orgânicos utilizando eletrodos modificados poliméricos contendo partículas de Ni/Pd e Ni/Pt

Novel modified electrodes bearing dispersed Pd and Pt particles have been prepared from poly (allyl ether of the p-benzenesulfonic acid) films with incorporated nickel particles making use of galvanic displacement reactions. The SEM analysis of the new modified electrodes revealed efficient deposition of Pd but weak up-take of Pt. Electrocatalytic hydrogenation of several classes of organic substrates were carried out using the MEs Ni, Ni/Pd and Ni/Pt. The Ni/Pd ME showed to be the best of them for the hydrogenation of double, triple and carbonyl bonds. The complete hydrogenation of the aromatic rings for the well-adsorbed substrates acetophenone and benzophenone is noteworthy.

Uso da cinza da casca do arroz (CCA) obtida da geração de energia térmica como adsorvente de Zn(II) em soluções aquosas

The removal study was conducted using 1.00 g of the rice husk ash (RHA) and 20.0 mL solution with concentrations in the range of 10-1000 mg/L of Zn(II). The influence of contact time, initial metal concentration, agitation and pH of the removal process was investigated. Superior removals to 95% were obtained at the end of 24 h of contact. The agitation increased in 20% the removal of Zn(II), being needed only 5 min to reach the equilibrium. The adsorption process was studied by the models of isotherms of Langmuir, Freundlich and BET, obtaining results of R L and 1/n for a process favorable of adsorption. BET isotherm best represents the equilibrium adsorption. The results showed that the RHA has the largest capacity and affinity for the removal of Zn(II).