Abstract. The transformation of agricultural waste into activated carbon represents an attractive approach as new and alternative source, but also as a reduction of pollution associated to the degradation of precursors. The organic residues sugarcane (Saccharum officinarum) bagasse-shell, orange (Citrus sinensis) peel-bagasse, and eucalyptus (Eucalyptus globulus) leaves, obtained from a biodrying process were transformed into activated carbons using phosphoric acid as activating agent. The resulting materials were physicochemically characterized and after that, carbonaceous electrodes were prepared to test the feasibility of using them in a discoloration electro-Fenton wastewater treatment process. Orange peel-bagasse biodried precursor transformed into activated carbon showed the highest efficiency when used as the modifier in a carbon paste electrode due to its highest porosity, electroactive area (24.9x10-2 cm2), and roughness (1.21 a.u.), also to its chemical affinity for anionic molecules. These properties, in addition to the capability of electro-sorb iron ions on the surface during the Fenton reaction, allowed a 44 % methyl orange discoloration efficiency. Sugarcane bagasse-peel and eucalyptus leaves biodried residues were also evaluated with efficiencies under 30 %, mainly attributed to intrinsic composition of the precursor materials.

Resumen. La transformación de los residuos agrícolas en carbón activado representa un enfoque atractivo y novedoso, además de que representa una alternativa a la reducción de la contaminación asociada a la degradación de residuos orgánicos. Los residuos orgánicos de bagazo de caña de azúcar (Saccharum officinarum), bagazo y cáscara de naranja (Citrus sinensis), y hojas de eucalipto (Eucalyptus globulus), que fueron obtenidos de un proceso de biosecado, se transformaron en carbón activado utilizando ácido fosfórico como agente activante. Los materiales resultantes se caracterizaron fisicoquímicamente y después de eso, se prepararon electrodos de pasta de carbón modificados con estos materiales, para estudiar la viabilidad de utilizarlos en un proceso de tratamiento de aguas residualesmediante electro-Fenton. El precursor biosecado de bagazo y cáscara de naranja transformado en carbón activado mostró la mayor eficiencia cuando se usó como modificador en un electrodo de pasta de carbón, debido a su mayor porosidad, área electroactiva (24.9x10-2 cm2) y rugosidad (1.21), también debido a su mayor afinidad química por moléculas aniónicas. Estas propiedades, aunadas a la capacidad de electro-sorber iones de hierro en la superficie durante la reacción de Fenton, permitieron una eficiencia de decoloración del naranja de metilo del 44 %. También se evaluaron residuos biosecados de bagazo de caña de azúcar y hojas de eucalipto, con eficiencias inferiores al 30 %, atribuidas principalmente a la composición intrínseca de los materiales precursores.

ABSTRACT Cowpea is a socioeconomically important legume in the Northeast region of Brazil, and the most grown and consumed type of bean, representing the main source of low-cost vegetable protein for rural and urban populations in this region. The objective of this work was to characterize the proximate composition, minerals, tannins, phytic acid, and cooking quality of whole grains of cowpea from the commercial cultivars BRS Aracê, BRS Inhuma, and BRS Xiquexique. Grain samples of the cultivars were ground in a zirconium ball mill and the flour was used for analysis. The proximate composition was carried out according to the AOAC methodology. The minerals were determined by nitro-perchloric digestion and reading in a flame atomic absorption spectrophotometer. The anti-nutritional factors tannins and phytic acid were determined by extraction and reading in a spectrophotometer. Cooking quality was assessed using an electric pressure cooker and then a Mattson cooker. A completely randomized experimental design was used, with three treatments (cultivars) and three replications. The data were subjected to analysis of variance and the means were compared by the Tukey's test (p<0.05). The cowpea cultivars showed significant differences (p<0.05) for most characteristics evaluated and were similar in terms of ash, lipids, total dietary fiber, and most macrominerals. The results showed that grains of the cultivars BRS Aracê and BRS Xiquexique are excellent sources of dietary fiber, proteins, and minerals and present high cooking quality, while grains of the cultivar BRS Inhuma stood out regarding carbohydrates, soluble dietary fibers, total energetic value, and low levels of factors, anti-nutritional tannins and phytic acid.

RESUMO O feijão-caupi é uma leguminosa de grande importância socioeconômica na região Nordeste do Brasil, sendo o tipo de feijão mais cultivado e consumido, representando a principal fonte de proteína vegetal de baixo custo das populações rural e urbana dessa região. O objetivo deste trabalho foi caracterizar a composição centesimal, minerais, taninos, ácido fítico e a qualidade de cozimento dos grãos integrais das cultivares de feijão-caupi BRS Aracê, BRS Inhuma e BRS Xiquexique. A composição centesimal foi determinada de acordo com a metodologia AOAC. Os minerais foram determinados por digestão nitro-perclórica e leitura em espectrofotômetro de absorção atômica de chama. Os fatores antinutricionais taninos e ácido fítico foram determinados por extração e leitura em espectrofotômetro. A qualidade do cozimento foi avaliada usando uma panela de pressão elétrica e, em seguida, o cozedor de Matsson. Foi utilizado o delineamento inteiramente casualizado (DIC), com três tratamentos (cultivares) e três repetições. Os dados foram submetidos à análise de variância e as médias comparadas pelo teste de Tukey (p<0,05). As cultivares apresentaram diferenças significativas (p<0,05) para a maioria das características avaliadas e similares para os teores de cinzas, lipídeos, fibra alimentar total e a maioria dos macrominerais. As cultivares BRS Aracê e BRS Xiquexique representam excelentes fontes de fibras dietéticas, proteínas e minerais, além de alta qualidade de cozimento, enquanto a cultivar BRS Inhuma destacou-se em carboidratos, fibras alimentares solúveis, valor energético total e baixos teores dos fatores antinutricionais analisados.