19 research outputs found

    DIURON, METHOMYL AND MCPA ADSORPTION BY ACTIVATED CARBONS FROM ANGOLAN LIGNOCELLULOSIC PRECURSORS

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    This work reports the production of activated carbons from novel precursors, namely wood produced in Angola (Benguela region), and its application to remove pollutants from aqueous solutions, namely Diuron, Methomyl and MCPA. At present, Angola has a considerable amount of waste of wood, either from the cutting of trees for residential areas, factory, mining, oil and gas, which are abandoned, suffering a slow degradation

    Removal of poluttants by activated carbons made from wood produced in Angola

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    This work reports the production of activated carbons from novel precursors, namely wood produced in Angola (Benguela region), and its application to remove pollutants from aqueous solutions, namely an herbicide with a broad use in agriculture: Diuron (3- (3 4-dichlorophenyl)-1 1-dimethylurea)

    Valorization of natural fibres from African Baobab wastes by the production of activated carbons for adsorption of Diuron.

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    In this work the potential of natural fibrous materials from African Baobab wastes for the production of activated carbons (ACs) has been evaluated. The wastes tested as precursors for the production of ACs were the bark, wood and seed from the Baobab tree. The activated samples present good structural and chemical characteristics. These features allowed us to test some of the most representative samples in the adsorption of Diuron pesticide from liquidphase

    Desperdícios das Njiliti e Embondeiro na obtenção de carvões ativados.

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    Este trabalho apresenta os resultados da produção de adsorventes de carbono a partir de precursores de origem lenhocelulósica, provenientes de madeiras angolanas. Os resultados mostram que com diferentes precursores surgem algumas diferenças, sugerindo que reagem de forma distinta à ativação com CO2. Na figura 1 apresentam-se, como exemplo, uma isotérmica de adsorção de nitrogénio a 77 K determinada num adsorvente obtido revelando que o material é essencialmente microporoso. Os resultados de difração de raios X, composição elementar e ponto de carga zero, entre outros, revelam diferenças estruturais e químicas, mas também alguns aspetos semelhantes. Como exemplo, todos os materiais até agora obtidos apresentam carácter básico o que os torna promissores adsorventes de poluentes relevantes

    Activated carbons from Angolan woods for the adsorption of MCPA and Diuron

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    Carbon materials, and in particular activated carbon (ACs), are currently one of the most relevant and fundamental adsorbent materials in many areas of human activity, such as medical applications, gas separation and storage, removal of pollutants and odours and catalysis [1,2]. Angola is experiencing a considerable amount of wood wastes, which is the consequence of cutting down the trees for the implantation of residential areas and industrial facilities, like mining, oil and gas, and also for their use in the production of domestic coal. This huge amount of biomass wastes is abandoned and suffers a slow degradation process. In this work we report the preparation of ACs by activation with CO2 from wood wastes collected in Angola and its use for the adsorption from liquid-phase of pesticides of interest by their availability and toxicity, MCPA and Diuron [3]. The ACs samples were characterised by nitrogen adsorption at 77K, FTIR, CHNS-O elemental analysis and determination of pH of point of zero charge (pzc). The liquid phase adsorption studies were done at 25ºC using a batch method and a shaking thermostatic bath. The ACs produced are primordially microporous with BET apparent surface area and pore volume up to 2130m2g-1 and 0.99cm3g-1, respectively. Regarding the surface chemistry, ACs are of basic nature as indicated by the pzc, FTIR and elemental analysis. The MCPA and Diuron adsorption studies shown that the ACs tested show interesting results for the removal of pesticides. This can be particularly interesting and an asset in countries like Angola where the pesticides has been vastly and carelessly used with soil and water contamination as a consequence. The maximum adsorption capacities were 295 and 400mg/g for MCPA and Diuron, respectively

    Desenvolvimento de carvões ativados com base em novos percursos naturais oriundos de Angola

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    Neste trabalho foi efectuada a produção de carvões activados a partir de desperdícios de madeiras naturais de Angola, designadamente madeira, casca e semente de Embondeiro e madeira de Njiliti, de Tchitiotioli, de Nuati, de Hama e de Candeia. Os materiais produzidos por activação com dióxido de carbono, ácido fosfórico e hidróxido de potássio foram devidamente caracterizados e efectuados estudos para aplicações em fase líquida. Por FTIR foi possível identificar nos CAs obtidos os grupos funcionais álcool, alcano, alceno, amida, ligações (C = O), nomeadamente quinonas , lactonas e pironas. Nas amostras activadas com H3PO4 e KOH surgem novas bandas de absorção relativas ao ácido carboxílico com o desaparecimento do grupo pirona. No que diz respeito à estrutura porosa as amostras de carvões activados por dióxido de carbono atingiram área superficial aparente e volume poroso até 2298 m 2 /g e 0,99 cm 3 /g, e uma gama de largura media de poros (L0) entre 0,65 a 3,52 nm respetivamente. As amostras ativadas quimicamente mostram uma área superficial aparente entre 323 e 1682 m 2 /g e volume poroso de 0.17 a 0.65 cm 3 /g. Os carvões activados produzidos por activação com dióxido de carbono são de natureza básica, com valores de pzc entre 6.68 e 11.90, enquanto que nos materiais produzidos com activação com KOH e H3PO4 são de natureza ácida com pcz entre 2.2 e 4.7. Amostras selecionadas foram testadas para a adsorção de alguns pesticidas problemáticos, designadamente MCPA, Diuron e metomil a partir de soluções aquosas. A capacidade de adsorção máxima foi de 325,300 e 180 mg/g para MCPA e Metomil, na amostra S EMB29, e para Diuron na amostra M EMB63, respectivamente. Podemos destacar neste trabalho a potencial importância para aproveitamento de resíduos agrícolas da província de Benguela com a criação de produtos de valor acrescentado, os carvões activados; Astract: Production of activated carbons based in new natural precursors from Angola In this work the production of activated carbons from natural wood wastes from Angola, namely wood, bark and seed of Embondeiro and wood from Njiliti, from Tchitiotioli, from Nuati, from Hama and from Candeia were produced. Materials produced by activation with carbon dioxide, phosphoric acid and potassium hydroxide were properly characterized and studies were carried out for liquid phase applications. By FTIR it was possible to identify the functional groups alcohol, alkane and alkene, amide, bonds (C = O), namely quinones and lactones and pyrones. In the samples activated with H3PO4 and KOH new absorption bands relative to the carboxylic acid appear with the disappearance of the pyrone group. As far as the porous structure was concerned the carbon dioxide activated carbon samples reached apparent surface area and pore volume up to 2298 m2 /g and 0.99 cm3 /g, and an average pore width range (L0) between 0.65 to 3.52 nm respectively. The chemically activated samples show an apparent surface area between 323 and 1682 m2 /g and pore volume of 0.17 to 0.65 cm3 /g and average pore width around 1.5 to 6.16 nm. Activated carbons produced by activation with carbon dioxide are basic in nature, with pzc values between 6.68 and 11.90, where as in materials produced with activation with KOH and H3PO4 they are acidic with pcz between 2.2 and 4.7. Selected samples were tested for the adsorption of some problematic pesticides, namely MCPA, Diuron and methomyl from aqueous solutions. The maximum adsorption capacity was 325, 300 and 180 mg/g for MCPA and Metomil, in sample S EMB29, and for Diuron in sample M EMB63, respectively. We can highlight in this work the potential importance for the use of agricultural waste from the province of Benguela with the creation of value added products, activated carbons

    Aplicação de carvões activados de precursors lenhocelulósicos de origem Angolana na remoção de diuron.

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    As questões ambientais e de saúde pública estão cada vez mais presentes na agenda internacional. Em particular as consequências indesejadas da utilização de pesticidas na agricultura, em países em desenvolvimento, são um dos tópicos de maior atenção tanto ao nível político, social como científico [1]. Entre as técnicas mais utilizadas para a redução ou remoção destes poluentes a partir de águas contaminadas (naturais, consumo ou residuais) está a adsorção recorrendo a carvões ativados [2]. Esta estratégia ganha importância quando é possível valorizar os desperdícios de recursos endógenos de cada região. Este trabalho segue esta linha, pela via do aproveitamento de desperdícios lenhocelulósicos de origem angolana na produção de carvões ativados para utilização na remoção de um pesticida de largo espectro de aplicação na agricultura

    Activated carbons from Angolan wood wastes for the adsorption of MCPA pesticide

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    The work now reported presents the activated carbons production from Angolan woods wastes, namely Candeia, Hama, Njiliti, Nuati and Tchitiotioli. The physical activation with carbon dioxide produced materials with apparent surface area between 603 and 801 m2/g, pore volume from 0.26 to 0.36 cm3/g, mean pore width from 0.68 to 0.98 nm, and low external surface areas, less than 47 m2/g for all samples. All samples present a basic nature with point of zero charge in the range 8.58 to 11.90. Selected samples were tested for the adsorption of a problematic pesticide, MCPA (4-chloro-2-methylphenoxyacetic acid) from aqueous solutions. The maximum adsorption was between 85 and 295 mg/g after 24h of equilibrium. With this work a time window of potential applications for these precursors is open, with a not negligible economic impact for the country

    Desperdícios de madeiras angolanas como precursores na produção de carvões activados

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    Os desperdícios de algumas madeiras, entre elas, Njilitie e Embondeiro, foram submetidos a carbonização e ativação física com dióxido de carbono. A caracterização do precursor e dos adsorventes obtidos, envolveu analise termogravimétrica, porosimetria de mercúrio, adsorção de nitrogénio a 77K, difracção de raios X, análise elementar, FTIR e determinação do ponto de carga zero

    Removal of methomyl by adsorption on activated carbon from aqueous solution

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    Removal of methomyl by adsorption on activated carbon from aqueous solutio
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