PreparaÃÃo de carvÃo ativado e impregnaÃÃo com ferro ou cromo para aplicaÃÃes em processos de descontaminaÃÃo ambiental. / Preparation and impregnation of activated carbons with iron or chromium for aplication on environmental descontamination processes.

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

This work has five chapters, with objective of the preparation of activated carbons (AC) from agroindustrial residues (coffee hulls and wet blue leather) and preparation of catalysts using these AC for degradation of organic compounds. In the first chapter is showed a review from the literature about AC, the surface characterisitics and properties, the uses of AC, the environmental pollution concernings and Fenton oxidation processes. In the second chapter was presented a chemical activation with ZnCl2 using different waste/activating agent ratios and the influence of time activation. The best activated carbon, based on the higher surface area, was utilized for iron oxide impregnation. In this work the iron oxide was thermally reduced, under N2 atmosphere, using the H2 released from thermal decomposition of the AC. The goethite was converted into maghemite and magnetite. These materials showed high methylene blue (MB) oxidation and adsorption capacity. In the third chapter is showed the utilization of the chemical activation with ZnCl2 and a combined activation with ZnCl2/CO2. The prepared carbons were used as catalyst support for goethite, The materials were prepared by impregnation of gothite on the carbons. All materials were tested as a catalyst for organic compounds oxidation. The AC showed good properties for catalyst support and the impregnated materials with iron oxide showed catalytic activity on the MB oxidative decomposition by H2O2. The composites have shown high reutilization capability, up to five reaction cycles. The use of coffee hulls for AC production with high surface area showed to be a good possibility of using this waste. In the fourth chapter, mesoporous activated carbon was prepared using coffee hulls waste, with different NaH2PO4 to waste ratios. The materials showed high adsorption capacity for organic compounds: phenol, reactive red and methylene blue. The fifth chapter was utilized chromium containing leather waste as starting material for preparation of AC/Cr. The AC characterization showed a material with the high surface area, micro and meso porosity. The chromium species present at material surface were analyzed by X-ray fotoelectron and it is found Cr+3 and Cr+6 species. High catalytic activity for methylene blue oxidation with H2O2 was observed and the catalyst can be reused for at least ten reaction cycles.

ASSUNTO(S)

goethita outros compositos carvÃo ativado oxidaÃÃo. 1.waste 2. activated carbon. 3. goethite. 4. composites. 5. oxidation resÃduos

ACESSO AO ARTIGO

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