This study presents the results of a mature landfill leachate treated by a homogeneous catalytic ozonation process with ions Fe2+ and Fe3+ at acidic pH. Quality assessments were performed using Taguchi's method (L8 design). Strong synergism was observed statistically between molecular ozone and ferric ions, pointing to their catalytic effect on •OH generation. The achievement of better organic matter depollution rates requires an ozone flow of 5 L h-1 (590 mg h-1 O3) and a ferric ion concentration of 5 mg L-1.

É mostrada a preparação de diferentes materiais inorgânicos a partir de nióbio metálico e seu comportamento no processo de adsorção de brometo de cetiltrimetil amônio (CTABr). Os materiais inorgânicos estudados são o óxido de nióbio e o fosfato de nióbio hidratado. Os óxidos de nióbio foram obtidos pelo método da precipitação em solução homogênea com a decomposição térmica de (NH4)2CO3 realizada a 45 ºC e a 90 ºC. O fosfato de nióbio hidratado foi obtido pela dissolução do nióbio metálico a uma mistura de ácido fluorídrico e nítrico e adição de ácido fosfórico. Pelo método de adsorção gasosa (BET) e por microscopia eletrônica de varredura verificou-se que os materiais não apresentam mudança significativa nas características físicas. As isotermas de Langmuir e de Freundlich revelaram que o melhor resultado de adsorção do surfactante CTABr foi alcançado para o óxido de nióbio hidratado preparado a 90 ºC, com capacidade de adsorção máxima, segundo modelo de Langmuir, com 14,13 mg.g-1.

The preparation in inorganic material different from metallic niobium and its effect onto adsorption process of the cetyl trimethylammonium bromide CTABr is reported. The inorganic materials are studied niobium oxide hydrous and niobium phosphate hydrous. The niobium oxide hydrous were obtained by homogeneous solution precipitation method with thermal decomposition of (NH4)2CO3 at 45 ºC and 90 ºC .The niobium phosphate hydrous were prepared using of metallic niobium dilution in a mixture of fluoridric/nitric (10:1) and after phosphoric acid addition. Through the BET method and the SEM technique it was verified that the material suffer no significant change in the physical characteristics. The Langmuir and Freundlich isotherms showed better result to surfactant CTABr adsorption using the material prepared at 90 ºC, according to Langmuir model with maximum adsorption capacity of 14.13 mg.g-1.

Catalytic ozonation has been recognized in the scientific community as an efficient technique, reaching elevated rates of recalcitrant organic material mineralization, even at the presence of scavenger species of hydroxyl free radicals. This study presents the most significant factors involving the leachate treatment stabilized by the municipal landfill of the city of Guaratinguetá, State of São Paulo, Brazil, by using a catalytic ozonation activated by metallic ions Fe3+, Zn2+, Mn2+, Ni2+ and Cr3+. The Taguchi L16 orthogonal array and its associated statistical methods were also used in this study. Among the researched ions, the most notable catalysis was obtained with ferric ion, statistically significant in the reduction of COD with a confidence level of 99.5%.

Este trabalho mostra o efeito da temperatura de digestão do agente precipitante nas características físicas e químicas do Nb2O5.nH2O e do ZrO2.nH2O. Os compostos foram obtidos pelo método da precipitação em solução homogênea com a decomposição térmica do (NH4)2CO3 realizada a 45 ºC e a 90 ºC. A difração de raios X mostrou que o Nb2O5.nH2O preparado em qualquer uma das duas temperaturas é material cristalino apresentando espaçamento interlamelar, enquanto que o ZrO2.nH2O é amorfo. Pela análise térmica observou-se grau de hidratação semelhante para todos os materiais. As isotermas de Langmuir revelaram que os melhores resultados de adsorção foram alcançados para ambos os materiais preparados a 90 ºC.

This work reports the digestion temperature effect of precipitating agent on the physical and chemical characteristics of Nb2O5.nH2O and ZrO2.nH2O. The compounds were obtained by homogeneous solution precipitation method with thermal decomposition of (NH4)2CO3 at 45 ºC and 90 ºC. The X-ray diffraction analysis showed crystalline materials with interlamelar space for both Nb2O5.nH2O, whereas ZrO2.nH2O is amorphous. By thermal analysis a similar hydration grade was observed for all materials. The Langmuir adsorption isotherms show that the materials prepared at 90 ºC, in both cases, have the best results.