Nádia Regina Camargo Fernandes-Machado

Evaluation of photocatalytic activities of supported catalysts on NaX zeolite or activated charcoal

This study aimed to evaluate the photocatalytic activity of ZnO and Nb2O5 catalysts, both supported on NaX zeolite and activated charcoal (AC). The synergistic effect between oxide and support and the influence of solution pH (3, 7 and 9) on photocatalytic degradation of reactive blue 5G (C.I. 222) were analyzed. The catalysts Nb2O5/NaX, Nb2O5/AC and ZnO/NaX, ZnO/AC with 5 and 10% (wt%) were prepared by wet impregnation. The results showed that the catalysts exhibit quite different structural and textural properties. The synergic effect between ZnO and NaX support was higher than that with the activated charcoal, showing that these catalysts were more efficient. The most photoactive catalyst was 10% ZnO/NaX which showed 100% discoloration of the dye solution at pH 3, 7 and 9 after 0.5, 5 and 2h of irradiation, respectively. The hydrolytic nature of zeolite favored the formation of surface hydroxyl radicals, which increased the activity of the photocatalyst. Thus, catalysts supported on NaX zeolite are promising for use in photocatalysis.

Utilização de zeólitas sintetizadas a partir de xisto retortado na remoção de arsênio em águas contaminadas

The solid by-product of the oil shale processing (PETROBRAS - Brazil) was used as raw material to synthesize zeolites A and faujasite. Alkaline fusion followed by hydrothermal treatment was the synthesis procedure used, and five different starting material compositions were obtained. The more crystalline zeolite-type materials synthesized, the pretreated oil shale ash and commercial zeolites were used as adsorbents in the purification of pollutant solutions with arsenic. The zeolite-type material composed of a mixture of zeolite A (42.6%) and faujasite (52.9%) presented an ion exchange capacity comparable to the pure zeolites A and faujasite, much better than the pretreated ash.

TRATAMENTO DA VINHAÇA POR ADSORÇÃO EM CARVÃO DE BAGAÇO DE CANA-DE-AÇÚCAR

The aim of this study was to develop an effective and economically viable technology for the treatment of vinasse, prior to its disposal in the soil for fertirrigation, aiming this way at reducing the environmental impacts generated by inadequately discarding this effluent. The primary treatment of vinasse by adsorption was evaluated. Adsorbents were prepared from sugar cane bagasse and their efficiency evaluated in relation to the treatment of vinasse. The process of preparation of activated carbon consisted of carbonizing bagasse at different temperatures followed by chemical activation with NaOH. The carbon samples obtained by solely carbonizing sugar cane bagasse were more efficient for removing turbidity of vinasse than samples activated with NaOH. The sample carbonized at 800 °C was the most efficient for removing turbidity of wastewater (83%). During a process of adsorption of vinasse in two stages, it was possible to obtain color removal, turbidity and COD of approximately 76, 85 and 69%, respectively. After the adsorption step of vinasse, the solid waste generated in the second stage of adsorption can be burned in the boilers of the power plant itself, affording an energy of 4606 cal g-1.

Temperature Effect on Hydrogen Production from Reactions between Ethanol and Steam in the Presence of Pd-Ru/Nb2O5-TiO2 Catalyst

Temperature effect on the performance of Pd-Ru/Nb2O5-TiO2 (PRNT) catalyst on hydrogen production from reactions between ethanol and steam was evaluated. Parallel reactions occurred in all conditions studied according to what was observed by the presence of H2, CO2, CH4, CO, C2H4, C2H6, C2H4O and (C2H5)2O. While at 300 °C the process seems to be dominated by ethanol dehydrogenation and decomposition, at 375 °C dehydration it seems to compete for active sites with ethanol dehydrogenation and decomposition reactions. At 450 °C there is a dehydration reaction to ethane, basically competing at the same level with ethanol dehydrogenation decomposition reactions. Hydrogen production on PRNT catalyst is maximized at 300 °C.

TREATMENT OF VINASSE BY ADSORPTION ON CARBON FROM SUGAR CANE BAGASSE

The aim of this study was to develop an effective and economically viable technology for the treatment of vinasse, prior to its disposal in the soil for fertirrigation, aiming this way at reducing the environmental impacts generated by inadequately discarding this effluent. The primary treatment of vinasse by adsorption was evaluated. Adsorbents were prepared from sugar cane bagasse and their efficiency evaluated in relation to the treatment of vinasse. The process of preparation of activated carbon consisted of carbonizing bagasse at different temperatures followed by chemical activation with NaOH. The carbon samples obtained by solely carbonizing sugar cane bagasse were more efficient for removing turbidity of vinasse than samples activated with NaOH. The sample carbonized at 800 °C was the most efficient for removing turbidity of wastewater (83%). During a process of adsorption of vinasse in two stages, it was possible to obtain color removal, turbidity and COD of approximately 76, 85 and 69%, respectively. After the adsorption step of vinasse, the solid waste generated in the second stage of adsorption can be burned in the boilers of the power plant itself, affording an energy of 4606 cal g-1.

ESTUDO DA FOTODEGRADAÇÃO DE EFLUENTE DE INDÚSTRIA DE CELULOSE E PAPEL EMPREGANDO OS FOTOCATALISADORES DE TiO2, ZnO E Nb2O5

RESUMO: O setor de celulose e papel apresenta um efluente com uma elevada carga orgânica e alta coloracao. Os tratamentos convencionais sao eficientes para reducao de DQO e DBO do efluente, mas mesmo apos tratamento biologico, o efluente apresenta uma elevada coloracao. Muitas industrias ja estao utilizando tecnicas de tratamento terciario de efluentes para o polimento do mesmo, como a ultrafiltracao. Uma alternativa para o polimento e a fotocatalise heterogenea. O presente trabalho teve como objetivo o estudo da degradacao fotocatalitica de efluente de uma industria integrada de producao de celulose e papel. Foram realizadas as caracterizacoes dos catalisadores atraves de difracao de raio-x e analise textural. Os testes fotocataliticos foram realizados em reator batelada sob irradiacao UV (250W). Os catalisadores reduziram parcialmente a carga orgânica do efluente. Os melhores resultados foram obtidos com ZnO, sendo alcancada uma reducao de 35% da DQO quando foi utilizado ZnO massico calcinado a 500 o C. Palavras chaves: Fotocatalise heterogenea. Efluente Kraft. Pentoxido de niobio.