Search

Antioxidants are an alternative to prevent or retard biodiesel degradation. Soursop (Annona muricata L.) is a native tropical fruit with important antioxidant activity, besides high concentration of phenolic compounds. Peels form about 20 % of the soursop fruit composition and are usually discarded as a waste product. In this study the antioxidant potential of different peel extracts was evaluated by oxidative stability when used as an additive into soybean biodiesel. All samples were analyzed by the Rancimat® 873, using 32 experimental design. The tests were performed with biodiesel B100 with solutions extracted in different conditions, such as pH and residue concentrations. Results demonstrated that all experiments were able to increase significantly the induction period (IP), when compared to a pure biodiesel control sample, and showed similar efficiency with synthetic antioxidants (BHT). Among all experiments, each neutral and alkaline extractions presented induction periods over 8 h, achieving and surpassing the minimum allowed by European standard. However, the highest IP was found to be 10.30 h, with 3 g L-1 in neutral extraction. Results corroborate that soursop peel has a high antioxidant capacity and efficiency to improve the oxidation stability, and could be used as an inexpensive natural antioxidant to biodiesel.

A incorporação do biodiesel na matriz energética brasileira é de extrema importância para reduzir a importação de óleo diesel e diminuir os impactos ambientais gerados pelos gases de efeito estufa. Atualmente no Brasil a adição de biodiesel no óleo diesel é de 10%. Devido à biodegradabilidade do biodiesel, antioxidantes sintéticos são adicionados para aumentar sua vida útil, porém, esses compostos são derivados do petróleo e possuem potencial toxicidade e caráter carcinogênico. O objetivo deste trabalho foi utilizar extratos do Pleurotus ostreatus (P.O) como antioxidantes para biodiesel. Foram utilizadas técnicas rigorosas como: teste de oxidação acelerada (Rancimat® 873) e delineamento experimental simplex centróide. Para uso do P.O foram executadas a extração aquosa ácida, orgânica neutra e orgânica básica para extrair os compostos com potencial antioxidante e transferir-los para o biodiesel. A metodologia de extração aquosa ácida do P.O apresentou rendimento de 31,9%. Quando o biodiesel foi purificado com a solução ácida do Pleurotus ostreatus 5 g/L, o período de indução do biodiesel foi de 9,28 h (aumento de 183%), apresentando conformidade com a norma EN 14214.

Introduction: Acquired Immunodeficiency Syndrome (AIDS) is a disease of the human immune system resulting from infection by the Human Immunodeficiency Virus (HIV) virus. Methods: The study was carried out between 2015 and 2016 with patients who attended a Specialized Center for Parasitic Infectious Diseases in Paraná. The research was divided into two stages, where the effects of supplementation on TC4 + cells, viral load (LV) and number of opportunistic diseases were verified. 20mg / day of zinc was added to the cookies for 3 months. Results: Data analysis does not show statistical differences in VL and Zinc supplementation; however, supplementation shows that it is able to promote an increase in the TCD4 + count. Patients reported an improvement in their well-being and a decrease in the incidence of opportunistic diseases. Conclusion: Thus, it was observed that zinc supplementation was highly effective in increasing TCD4 + positively improving the immune response and quality of life. In addition, the supplementation in the form of biscuits proved to be innovative and very effective.

Carbon steel is one of the most widely used alloys in industrial applications. However, the use of this metal may be limited because of corrosion tendency. Thus, it is necessary to develop methods that inhibit its degradation. One way to inhibit corrosion is to use organic inhibitors. Some organic compounds with heteroatoms inhibit corrosion by forming a protective film. In this study, the corrosion inhibition of carbon steel 1020 in 0.1 mol L-1 hydrochloric acid medium was evaluated. The natural inhibitor used was an aqueous extract of the bark of Persea pyrifolia (PP) plant at concentrations of 2.5, 5 and 10% V / V. The electrochemical response was determined by open circuit potential measurements, electrochemical impedance spectroscopy, and anodic potentiodynamic polarization. Therefore, mass loss was measured, and inhibitory efficiency was evaluated. The best results were observed for the concentration of 2.5% V / V of Persea pyrifolia extract, presenting and inhibition efficiency of 82.5% on the 1020 carbon steel. The electrochemical results indicates that PP extract can be used as green corrosion inhibitor in acidic medium. DOI: http://dx.doi.org/10.17807/orbital.v13i2.1469

Renewable energy methodologies are the key to a sustainable future. PV technology has been raised as one of the most promisor alternatives for energy conversion, due to the use of an inexhaustible source. The third generation of solar devices, present in composition a semiconductor oxide, that work as electron transport material (ETL), receiving and transporting the electron from a photosensitive molecule. TiO2 performs with efficiency the role of ETL in solar devices, nevertheless, since of the higher cost, other oxides have been studied, as Nb2O5. This work aims to synthetized Nb2O5 by Pechini methodology and applied it as ETL in a solar device. The techniques performed in particle characterization were Scanning Electronic Microscopy (SEM) and X-ray diffraction (XRD). To verify the capability of transport electrons, the electrochemical measurements were applied to Voc/Jsc decay, j-V curves, Electrochemical Impedance Spectroscopy (EIS), and Intensity Modulate Photovoltage Spectroscopy (IMVS). The results showed Nb2O5 synthesized in orthorhombic phase able to produce a photosensitive dye-solar device with j = 4.18 mA cm−2, V = 825 mV, FF = 0.4, PCE = 1.38% with slow recombination rate when compare to TiO2 dye-solar cell. The IMVS and EIS technique present the same accuracy to electron lifetime determination which is confirmed by the t-test performed.

Resumo Células solares sensibilizadas por corante são eficientemente desenvolvidas com TiO2 na composição. O isopropóxido de titânio, por possuir uma extensa cadeia alcoxi, evita a aglomeração de núcleos metálicos, gerando partículas com tamanho reduzido, tornando-se um precursor ideal para produção do TiO2. Este trabalho teve como objetivo avaliar a proporção de isopropóxido de titânio na síntese de TiO2 via metodologia Pechini. As partículas foram caracterizadas via difração de raios X, microscopia eletrônica de varredura e espalhamento dinâmico de luz. A célula foi caracterizada por curvas j-V e espectroscopia de impedância eletroquímica. Os resultados demonstraram que nas proporções testadas não houve mudança significativa de cristalinidade e forma das partículas. Verificou-se que a proporção molar cátion metálico:ácido cítrico de 2:1 apresentou partículas de menores diâmetros, facilitando a adsorção do corante e potencializando os parâmetros fotoeletroquímicos. A caracterização da célula solar nesta condição forneceu eficiência em conversão de energia η = 4 , 16 % ± 0 , 07 %, densidade de corrente j = 9 , 10 ± 0 , 09 m A . c m - 2 e tempo de vida eletrônico τ e = 56 , 98 m s. Abstract Dye-sensitized solar cells are efficiently developed with TiO2 in the composition. Titanium isopropoxide, due to its high organic load, prevents agglomeration of the metal nucleus, generating particles of small size, becoming ideal for TiO2 synthesis. This paper aimed to evaluate the proportion of titanium isopropoxide in TiO2 synthesis by Pechini methodology. The particles were characterized by X-ray diffraction, scanning electron microscopy, and dynamic light scattering. The cells were characterized by j-V curves and electrochemical impedance spectroscopy. It was demonstrated that the studied proportions had no significant effects on particle crystallinity and shape. It was also observed that metallic cation:citric acid molar proportion of 2:1 presented particles with a smaller size, facilitating the adsorption of the dye by enhancing the photoelectrochemical parameters. The characterization of the solar cell in this condition provided efficiency of energy conversion η = 6 . 94 % ± 0 . 07 %, current density j = 9 , 10 ± 0 , 09 m A . c m - 2, and electron lifetime τ e = 56 , 98 m s.

O desenvolvimento humano esta relacionado com a descoberta de novas fontes de energia. Por outro lado, esta busca conduziu a severas mudancas climaticas e danos ao meio ambiente, que acabou sendo o foco de pesquisa do seculo. Aquecimento global, chuva acida, deplecao da camada de ozonio dentre outros problemas ambientais, conduziram ao desenvolvimento de metodologias alternativas de energia. A celula solar e um dos dispositivos mais promissores para a reducao da queima de combustiveis fosseis, por utilizar um recurso energetico inesgotavel. Celulas solares sensibilizadas por corante (CSSC), desde descobertas por Gratzel e colaboradores, tem apresentado grande foco de estudo, devido ao baixo custo de producao, boa eficiencia e facil producao. Estas, sao fabricados pelo uso de um material semiconductor, um corante com alto coeficiente de extincao molar, um intermediador de cargas e um material com atividade catalitica. As mais variadas metodologias eletroquimicas de caracterizacao vem sendo utilizadas para entender o principio operacional destes dispositivos. Neste trabalho e apresentado uma revisao no campo das CSSC, os materiais utilizados, o principio operacional, os avancos tecnologicos e as mais diversas tecnicas de caracterizacao utilizadas

Celulas solares sensibilizadas por corante (CSSCs) sao uma nova geracao de dispositivo fotovoltaicos capazes de absorverem luz solar e converter em eletricidade. As CSSC utilizam em sua composicao oxidos semicondutores nanocristalinos, principalmente o dioxido de titânio (TiO 2 ), sensibilizados por corantes rutenados. Atualmente, busca-se o a modificacao do TiO 2 com particulas que sejam capazes de aumentar a eficiencia desta celula. O objetivo deste trabalho e estudar a influencia das variaveis do processo de sintese de particulas de oxido de cerio (CeO 2 ), visando a aplicabilidade em celulas solares sensibilizadas por corante N719. O CeO 2 foi obtido pelo metodo por precipitacao. Foi aplicado delineamento fatorial incompleto Box-Behnken (3 3 ), para as variaveis: concentracao de Ce(NO 3 ­) 3 .6H 2 O (mol.L -1 ), temperatura do meio reacional (°C) e tempo de reacao (h). As particulas foram caracterizadas por medidas de espalhamento de luz (DLS), analise por difracao de raios X (DRX), microscopia eletronica de varredura (MEV). O CeO 2 foi aplicado na celula solar juntamente com dioxido de titânio (TiO 2 )e os parâmetro fotovoltaicos foram extraidos. A otimizacao resultou em uma concentracao de Ce(NO 3 ) 3 .6H 2 O igual a 0,1 mol.L -1 , tempo de reacao de 18 h e temperatura de 80 °C, onde o menor valor medio para a particula foi de 99,30 nm. Os ensaios eletroquimicos evidenciaram que a amostra contendo diâmetro de particulas menores TiO 2 +CeO 2 100nm , apresentou uma eficiencia de conversao de energia solar, cerca de 30% maior, que as particulas de diâmetros maiores ( TiO 2 +CeO 2 1000nm ).

Biodiesel is a renewable fuel, thus is a sustainable option to minimize the environmental impacts of burning fossil fuels. However, biodiesel may suffer oxidative processes and is necessary to add antioxidants in it. In this study, macerated barley waste and Moringa oleifera leaves were used as antioxidants sources for biodiesel (soybean oil methyl ester). Accelerated oxidations studies, using 32 experimental design and employing the equipment Rancimat®, were made and the best induction time found was 8.18 ± 0.18 h, to concentrations of 13 and 9 g L−1 of waste and leaves, respectively. It was also established that oxidation kinetics follows a zero-order reaction (k = 7.28 × 10-7 cm μS−1 s−1), with an activation energy of 242.1 kJ mol−1. Besides, at 25 °C the biodiesel produced under these conditions can be stored for about 6.5 months without quality losses due to oxidative processes. Thus, it is possible to use barley waste and moringa leaves as antioxidant sources for biodiesel.

Renewable energy sources have received much attention in recent years due to concerns about global climate and environmental changes. Solar energy appears to be a promising alternative, especially dye-sensitized solar cells (DSSC), which, according to the literature, can achieve a power conversion efficiency in excess of 11%, depending on the semiconductor oxide used in their fabrication. The aim of this paper is to investigate the performance of DSSCs using cerium oxide (CeO2), titanium oxide (TiO2), and commercial dye N719. CeO2 was obtained using the Pechini and precipitation methods. The characterization techniques employed were x-ray diffraction, Raman spectroscopy, scanning electron microscopy, ultraviolet–visible spectroscopy, dynamic light scattering, and photoelectrochemical measurements. The results indicate that the efficiency of the DSSC CeO2/TiO2 obtained using the precipitation method was about 20% higher than that of the DSSC TiO2.

In this study, it was investigated the photovoltaic parameters of Dye Sensitized Solar Cells (DSSC) and the thin coating morphology of TiO2 by Doctor Blading and Spin Coating methods, sintered at 450 ºC and 450 ºC with a heating rate of 0.4 ºC s-1, using a natural dye extract from Hibiscus. These properties were studied by scanning electron microscopy (SEM), photochronoamperometry and curves j-V. It was demonstrated that all solar cells produced are photosensitive with an excellent charge injection. The cell with a better energy conversion (jsc = 0.53 mA cm-2; Voc= 0.471 V and FF= 0.518), uniform and flawless morphology was obtained to cell coated by Doctor Blading method, with a heat treatment of 450 ºC/0.4 ºC s-1. DOI: http://dx.doi.org/10.17807/orbital.v10i3.1101

Mix of oxides is an alternative method to enhance the photoelectrochemical parameters of solar devices. Nb inserted in TiO2 was prepared successfully by Pechini methodology and the oxide was used as electron transport material in P3HT organic solar device. TiO2 anatase/rutile was confirmed by XRD measurement and band gap determination combined with cyclic voltammetry measurement indicated the Nb sub states creation above TiO2 conduction band. IMVS and OCP decay diagram showed an increasing in electron lifetime of 0.4758 s–0.6645 s to the cell containing Niobium. The energy conversion efficiency to the cell based in 5% of Nb presented an improving about 25% when compared to bared TiO2, proving that this methodology is a promisor route to produce enhanced electron transport materials.

Celulas solares sensibilizadas por corante (CSSC) sao dispositivos que aproveitam a luz do sol para gerar energia e possuem na composicao um oxido semicondutor e um fotossensibilizador adequado. Devido ao custo elevado, a pesquisa por novos materiais aplicados nas celulas solares desperta grande interesse. Este trabalho tem como objetivo estudar celulas solares hibridas de interface FTO/TiO2/corante produzidas com diferentes fotossensibilizadores naturais de baixo custo, extraidos em solucao etanoica acidificada, de diferentes produtos naturais: ameixa, uva, urucum e berinjela. As tecnicas de caracterizacao utilizadas foram: Espectroscopia na regiao do ultravioleta-visivel (UV-VIS), Espectroscopia na regiao do Infravermelho por Transformada de Fourier (IV-TF), medidas do Potencial de Circuito Aberto em funcao do tempo (Eca), curvas Fotocronoamperometricas (FCA) e Curvas de Densidade de Fotocorrente em funcao do Potencial (j-E). Os corantes testados nas CSSC apresentaram caracter de fotossensibilidade, com adsorcao nos filmes de TiO2 e absorcao maxima na regiao do visivel. A CSSC com melhores parâmetros fotovoltaicos foi empregando-se o corante extraido da ameixa, gerando uma celula solar com ƞ = 0,12±0,03, Eca = 572±12 mV, FF = 0,57±0,01 e jcc = 0,40±0,09 mA cm-2.

Biodiesel is subject to radical reactions that promote degradation. To decrease the speed of these degradation reactions and increase oxidative stability, either natural or synthetic antioxidants are added to biodiesel. Thus, the objective of this study is to evaluate the effect of extracts of pecan nutshell (Carya illinoensis) as natural antioxidants derived from biomass using water, ethanol, and methanol/water (50/50) as a solvent for extraction. The addition of these antioxidants is performed during the soybean biodiesel washing process in an unconventional manner. The results obtained are statistically analyzed and compared to the control. The induction time (IT) for the biodiesel samples washed with ethanolic extract of pecan nutshell (5 g L−1), aqueous extract of pecan nutshell (12 g L−1) and methanol/water extract of pecan nutshell (12 g L−1), are, respectively, 9.46, 7.60, 7.43 h. The activation energy and the storage time of the biodiesel samples washed with the extracts are also studied. The order of reaction of the oxidation kinetics of biodiesel is first order.

The corrosion inhibition of mild steel in 1 mol L−1HCl by barley grains and malting process residue extracts was investigated by weight loss measurements, polarization curves, electrochemical impedance measurements and scanning electron microscopy. The inhibition efficiency exceeded 92% in the presence of 100 mg L−1 extracts after 24 h immersion time for both extracts. The Ea decreased with the addition of the extracts, characterizing the chemical adsorption by the molecules present in the extracts on the surface.The high molecular weight fraction isolated from the barley grain extract also showed high inhibition efficiency, suggesting that macromolecules are probably responsible for the inhibitory action.

A producao de etanol esta crescendo anualmente. No entanto, como aspecto negativo deste crescimento ocorre uma competicao entre a producao de alcool e de alimentos. Dentre as alternativas para a producao de etanol a erva daninha Cyperus esculentus apresenta aproximadamente 32% de amido. O amido deve passar pelo processo de hidrolise, em que ocorre a quebra das cadeias polimericas do amido e assim a formacao de acucares redutores. Neste trabalho foi utilizada a rota acida via acido fosforico. Para avaliar a melhor condicao de hidrolise do acido fosforico, utilizou o delineamento experimental 2 2 . As variaveis utilizadas foram a temperatura e o tempo de reacao. A melhor resposta obtida foi a temperatura de 110 °C com um tempo de 120 minutos, dando como resposta 0,195 mg L -1 de acucar redutor e 76,80 % de teor de etanol. Em relacao ao estudo cinetico, foi efetuado um novo ensaio usando as temperaturas de 70, 90 e 110 °C com um tempo de 120 minutos, para descobrir a ordem de reacao e a constante de ionizacao. Os valores de k encontrados para hidrolise via H 3 PO 4 com cinetica de primeira ordem foram: k 70 = 0,0271; k 90 = 0,0225 e k 110 = 0,0220 min -1 , sendo assim k 70 >k 90 >k 110 indicando que a reacao foi mais lenta na temperatura de 110 °C.

RESUMO Os incentivos às políticas energéticas e as atuais exigências ambientais motivam a busca por fontes de energia alternativa, como o gás hidrogênio. Este trabalho tem como objetivo a produção do gás hidrogênio via eletrólise do ácido fórmico, utilizando eletrodos de aço carbono 1008 e ferro Armco. Os ensaios foram feitos mediante planejamento experimental, e empregaram-se as técnicas de microscopia óptica, polarização potenciodinâmica catódica, potencial de circuito aberto e cronoamperometria. Os resultados mostraram que o tratamento da superfície dos eletrodos com lixa de carbeto silício (SiC) #320 é eficiente quando comparada aos outros tratamentos testados, para o desprendimento de H2. O ferro Armco, apresentou maior produção de hidrogênio, em média 70% a mais quando comparado com a platina em ambos os meios estudados, entretanto sua vida útil é menor. ABSTRACT Incentives for energy policies and current environmental requirements motivate the search for alternative energy sources such as hydrogen gas. This paper aims at the production of hydrogen gas via electrolysis of formic acid using electrodes of 1008 carbon steel and Armco iron. Samples were done by experimental design, and employed the techniques of optical microscopy, cathodic potentiodynamic polarization, open circuit potential and chronoamperometry. The results showed that the surface treatment of the electrodes with #320 grit SiC abrasive paper is effective when compared to the other treatments tested for the evolution of H2. The Armco iron, showed higher hydrogen production, on average 70% increased when compared with platinum in both studied media, however its lifetime is shorter.

Some metals prior to receiving a layer of paint should be submitted to a treatment of metal surface, since they are subjected to corrosion. This work aims the obtaining and characterization of a coating based on ceramics of cerium and / or zirconium for metal surfaces treatment. The ceramics were obtained by immersing the aluminum alloy 3003 and the carbon steel (SAE 1010) in the polymeric resin of citric acid and ethylene glycol according to the Pechini method. The characterization of the samples was performed using the following techniques: scanning electron microscopy (SEM), open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and Potentiodynamic Anodic Polarization (PAP). It was confirmed that the coatings of cerium and / or zirconium presented themselves as promise in the treatment of metal surfaces, because both showed good resistance, protecting the metal from corrosion.

This work proposes the development of a niobium phosphate coating (PNb) to replace the zinc phosphating, which is very aggressive to the environment and human health. The metallic material utilized was carbon steel (SAE 1010), which was coated with sunbathing - gel containing phosphate and niobium. A traditional zinc phosphate coating was used for comparison of results. The samples were characterized by scanning electron microscopy (SEM), dispersive energy spectroscopy (DES), open circuit potential, electrochemical impedance spectroscopy and anodic polarization. The results demonstrated that the samples coated with niobium phosphate have more surface nobility and greater corrosion resistance.