Página 1 dos resultados de 2082 itens digitais encontrados em 0.011 segundos

Filtração lenta em areia, manta não tecida e carvão ativado como pós-tratamento de efluentes domesticos e reuso; Slow sand filtration with non woven syxthetic fabric and activated carbon as after treatment of domestic sewer effluent and reuse

Danilo Aparecido Faveri
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 24/02/2006 PT
Relevância na Pesquisa
684.3986%
A filtração lenta é uma alternativa viável para regiões rurais afastadas dos grandes centros urbanos que necessitam de um sistema de tratamento de água de baixo custo de implantação, assim, presente trabalho avaliou a eficiência e o desempenho da filtração lenta em uma instalação piloto de filtração em areia e manta não tecida, e carvão ativado, precedida de um pré-filtro em pedregulho para tratamento de efluente de um sistema composto um de reator anaeróbio compartimentado e de leitos cultivados (wetlands) para tratamento de esgoto doméstico. Ênfases específicas foram dadas na avaliação da Filtração Lenta com meio filtrante de areia e manta não tecida e meio filtrante de areia com camada de carvão ativado granular e manta não tecida. Para uma taxa de filtração média de 3 m3/m2.dia, obteve-se uma eficiência média na remoção de sólidos em suspensão de 36,2% para o filtro lento de carvão e areia e manta não tecida e 28,2% para o filtro lento de areia e manta não tecida. A eficiência na remoção de turbidez foi de 43,2% no filtro de carvão e areia e manta não tecida e 33,2% no filtro de areia e manta não tecida. Para a cor obteve-se uma eficiência média de 39,3% para o filtro lento com camada de carvão e areia e manta não tecida e 26...

Produção e caracterização de carvão ativado para remoção de microcistinas; Production and characterization of activated carbon for removing microcystins

Eden Cavalcanti Albuquerque Junior
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 10/11/2006 PT
Relevância na Pesquisa
679.0872%
As microcistinas, hepatotoxinas, são os principais agentes tóxicos produzidos pelas cianobactérias. Essas toxinas vêm despertando atenções em razão do aumento do número de registros de florações tóxicas de cianobactérias em reservatórios destinados ao abastecimento público; da descoberta de novas toxinas e dos riscos associados a elas e do aumento de intoxicação aguda e crônica, tanto em animais como em seres humanos. A eficiência na remoção destas toxinas de água por carvão ativado depende de algumas características físico-químicas deste adsorvente, além da matéria-prima utilizada na sua obtenção. Neste trabalho, materiais como casca de macadâmia, endocarpo do coco seco e mesocarpo do coco verde da baía, bagaço de cana-de-açúcar e resíduo de madeira de pinus foram selecionados para obtenção de carvões ativados com potencial aplicação na remoção de microcistina de água potável. Os carvões ativados obtidos da madeira de pinus e bagaço de cana-de-açúcar apresentaram melhores estruturas porosas com ASEBET e Vmesoporos de 1586 e 1222 m2/g e 0,39 e 1,05 cm3/g, respectivamente. A partir de uma investigação da cinética e equilíbrio de adsorção da [D-Leucinal]MCYST-LR por estes dois carvões ativados pulverizados foi possível estimar uma remoção desta toxina acima de 98% em 10 minutos de contato...

Adsorption of fluoxetine onto waste-based activated carbon; Adsorção de fluoxetina a carvões de bio-resíduos ativados

Jaria, Guilaine Marques
Fonte: Universidade de Aveiro Publicador: Universidade de Aveiro
Tipo: Dissertação de Mestrado
ENG
Relevância na Pesquisa
677.3654%
Activated carbons are one of the most promising techniques for the removal of organic and inorganic compounds from waters. In this work three activated carbons were produced using as precursor primary paper mill sludge. Chemical activation was performed using three different activation agents, KOH, NaOH and ZnCl2, and the same pyrolysis conditions were applied. The characterization of the obtained materials was made by means of total organic carbon analysis (TOC), Fourier infrared spectroscopy with attenuated total reflectance (FTIR-ATR), proximate and ultimate analysis, scanning electron microscopy (SEM), Hg porosimetry, BET isotherms and point of zero charge (PZC) determination. Adsorption studies were made, beginning with adsorption kinetic and then adsorption equilibrium (isotherms of adsorption), all performed in batch experiments. Generally, the carbons presented an equilibrium time of around six hours. Equilibrium studies allowed test the adsorption capacity of the produced carbons for fluoxetine-HCl. These two studies were also performed to the primary sludge pyrolysed under the same conditions without activation and also to a commercial activated carbon as reference. Among the produced materials, the carbon activated with ZnCl2 has the higher BET surface area and percentage of carbon. The maximum adsorption capacity (mg g-1) was of 96.2 ± 1.0 for PBFG4; 120.4 ± 2.5 for PS800-10; 191.6 ± 4.8 for PS800-10KOH; 136.6 ± 9.6 for PS800-10NaOH; and 28.4 ± 0.3 for PS800-10ZnCl2. The isotherms obtained point for different mechanism of adsorption between the carbons...

In vitro adsorption study of fluoxetine in activated carbons and activated carbon fibres

Nabais, Joao; Carrott, Peter; Ribeiro Carrott, Manuela; Mouquinho, Ana; Galacho, Cristina
Fonte: Universidade de Évora Publicador: Universidade de Évora
Tipo: Artigo de Revista Científica Formato: 43637 bytes; application/pdf
ENG
Relevância na Pesquisa
677.6661%
We study the in vitro adsorption of fluoxetine hydrochloride by different adsorbents in simulated gastric and intestinal fluid, pH 1.2 and 7.5, respectively. The tested materials were two commercial activated carbons, carbomix and maxsorb MSC30, one activated carbon fibre produced in our laboratory and also three MCM-41 samples, also produced by us. Selected samples were modified by liquid phase oxidation and thermal treatment in order to change the surface chemistry without significant modifications to the porous characteristics. The fluoxetine adsorption follows the Langmuir model. The calculated Q0 values range from 54 to 1112 mg/g. A different adsorption mechanism was found for the adsorption of fluoxetine in activated carbon fibres and activated carbons. In the first case the most relevant factors are the molecular sieving effect and the dispersive interactions whereas in the activated carbons the mechanism seams to be based on the electrostatic interactions between the fluoxetine molecules and the charged carbon surface. Despite the different behaviours most of the materials tested have potential for treating potential fluoxetine intoxications.

Electrochemical storage of energy in acrylic activated carbon fibres and activated carbons made from industrial residues

Nabais, Joao; Carrott, Peter; Carrott, Manuela Ribeiro; Almeida, Ines; Teixeira, Jorge
Fonte: Universidade de Évora Publicador: Universidade de Évora
Tipo: Aula Formato: 49014 bytes; application/pdf
ENG
Relevância na Pesquisa
677.93266%
In this work the application as electrochemical capacitors of novel materials, never tested before for this propose, were investigated using classic cyclic voltammetry, chrono potentiometry, chrono amperometry and electrochemical impedance spectroscopy. The tested materials were prepared in our laboratory: a) acrylic activated carbon fibres (ACF) (samples F920, F932, F993) produced from a commercial acrylic fiber by carbon dioxide activation at 900ºC according the procedure described in ref. 1; b) activated carbons (AC) produced from a coffee industry residue, the coffee endocarp, by carbon dioxide activation (samples C823, C840, C863) and KOH activation (samples AQ62, AQ605) (please see ref. 2 for experimental details). All the materials were easily produced in monolithic shape that can be considered an advantage over other materials because the electrode pos-production step and the use of binders are not needed. The carbon materials textural, structural and chemical characteristics were very different between samples with apparent BET surface area, ABET, range from 89 to 1050m2/g, micropore volume given by S method, VS, between 0.04 and 0.50cm3/g, oxygen and nitrogen content in the range 7-16 and 1-8wt%, respectively, and microcrystalline dimensions La and Lc within the limits 2-4 and 1-4nm...

Acetylation of glycerol over heteropolyacids supported on activated carbon

Ferreira, P; Fonseca, I; Ramos, A; Vital, J; Castanheiro, J
Fonte: ELSEVIER Publicador: ELSEVIER
Tipo: Artigo de Revista Científica
POR
Relevância na Pesquisa
677.3654%
The acetylation of glycerol was carried out over dodecatungstophosphoric acid (PW) supported on activated carbon, being the monoacetin, diacetin and triacetin the reaction products. A series of catalysts, with different heteropolyacid loading (from 3.5 to 6.5 wt.%), were prepared. It was observed that the catalytic activity increases with the amount of PW immobilized on the activated carbon, being the PW2_AC (with 4.9 wt.%) the most active sample. However, at high loading of heteropolyacid on the activated carbon, a decrease on the catalytic activity was observed, which can be probably explained due to some hindrance in the activated carbon porous system. All catalysts exhibited good values of selectivity to the diacetin. Catalytic stability of the PW2_AC was also studied by performing consecutives batch runs with the same catalyst sample. After the third batch, it was observed that the catalytic activity stabilized.

Pollutants removal onto novel activated carbons made from lignocellulosic precursors

Valente Nabais, Joao; Laginhas, Carlos; Carrott, Manuela; Carrott, Peter; Gomes, Jose; Suhas, Suhas; Ramires, Ana; Roman, Silvia
Fonte: Carbon 2009 Publicador: Carbon 2009
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
677.6661%
The adsorption of phenol and mercury from dilute aqueous solutions onto new activated carbons was studied. These included activated carbons produced from novel precursors, namely rapeseed, vine shoots and kenaf, and samples oxidised with nitric acid in liquid phase. The results have shown the significant potential of rapeseed, vine shoots and kenaf for the activated carbon production. The activated carbons produced by carbon dioxide activation were mainly microporous with BET apparent surface area up to 1224m2g-1 and pore volume 0.5cm3g-1. The effects of concentration and pH were studied. The phenol adsorption isotherms at 25ºC followed the Freundlich model with maximum adsorption capacities of approximately 80mgg-1 and 60mgg-1 for the pristine and oxidised activated carbons, respectively. The influence of pH on the phenol adsorption has two trends for pH smaller and bigger than 10. The maximum adsorption capacity of mercury adsorption onto activated carbon made from vine shoots reaches 1103mgg-1. The adsorption depends on the mercury species and the on the adsorbent properties, namely porosity and net surface charge.

Activated carbon fibres prepared from kenaf: Influence of the experimental consditions on the morphology and textural properties

Valente Nabais, Joao; Carrott, Peter; Carrott, Manuela; Correa, Eduardo
Fonte: The British Carbon Group, Publicador: The British Carbon Group,
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
776.1743%
Porous materials are usually heterogeneous both structurally and energetically. Activated carbon fibres (ACFs) are relatively novel fibrous adsorbents produced for example from pith, cellulose, lignocellulose, phenol resin and polyacrylonityile (Peebles, 1995; Ryu, 1999). ACFs show important advantages with respect to conventional activated carbons. Among these advantages it is worth noting their high adsorption capacity and easiness to handle. Their main inconvenience lays on the difficulty of choosing adequate activating agents and activation conditions that are required in order to maintain the fibrous morphology. The adsorption capacity of ACFs depends on many factors, such as raw materials, activation process, pore structure and surface functionalities (Suffet, 1981; Park, 1999). Surface roughness is an important factor that influences the adsorption properties of an activated carbon. Fractal dimension is a measure of roughness of a surface. The use of the fractal concept is becoming very popular as a tool to characterize the texture of complex materials, such as porous solids. The fractal properties of these porous systems were determined by means of several techniques such as gas adsorption, mercury porosimetry and Small-Angle X-Ray Scattering (SAXS and SANS). Kenaf is an herbaceous annual plant that belongs to the family of Malvaceae. Kenaf possesses both...

Production and characterization of granular activated carbon from activated sludge

Al-Qodah,Z.; Shawabkah,R.
Fonte: Brazilian Society of Chemical Engineering Publicador: Brazilian Society of Chemical Engineering
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2009 EN
Relevância na Pesquisa
683.8944%
In this study, activated sludge was used as a precursor to prepare activated carbon using sulfuric acid as a chemical activation agent. The effect of preparation conditions on the produced activated carbon characteristics as an adsorbent was investigated. The results indicate that the produced activated carbon has a highly porous structure and a specific surface area of 580 m²/g. The FT-IR analysis depicts the presence of a variety of functional groups which explain its improved adsorption behavior against pesticides. The XRD analysis reveals that the produced activated carbon has low content of inorganic constituents compared with the precursor. The adsorption isotherm data were fitted to three adsorption isotherm models and found to closely fit the BET model with R² equal 0.948 at pH 3, indicating a multilayer of pesticide adsorption. The maximum loading capacity of the produced activated carbon was 110 mg pesticides/g adsorbent and was obtained at this pH value. This maximum loading was found experimentally to steeply decrease as the solution pH increases. The obtained results show that activated sludge is a promising low cost precursor for the production of activated carbon.

Adsorption of chromium ion (VI) by acid activated carbon

Attia,A. A.; Khedr,S. A.; Elkholy,S. A.
Fonte: Brazilian Society of Chemical Engineering Publicador: Brazilian Society of Chemical Engineering
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2010 EN
Relevância na Pesquisa
679.25234%
The activated carbon produced from olive stones was chemically activated using sulfuric acid, (OS-S), and utilized as an adsorbent for the removal of Cr(VI) from aqueous solution in the concentration range 4-50 mg/L. Adsorption experiments were carried out in a batch process and various experimental parameters such as effect of contact time, initial chromium ion concentration, carbon dosage, and pH on percentage removal have been studied. Adsorption results obtained for activated carbon (OS-S) were compared with the acid-treated commercial activated carbon (CAC-S). The optimum efficiency shows that the Cr(VI) uptake being attained at pH 1.5. The equilibrium adsorption data was better fitted to the Langmuir adsorption model. The results of kinetic models showed that the pseudo-first-order kinetic model was found to correlate the experimental data well. It was concluded that activated carbon produced from olive stones (OS-S) has an efficient adsorption capacity compared to (CAC-S) sample.

Preparação, caracterização e avaliação de óxidos de ferro e cobalto suportados em carvão ativado polimérico como catalisador na reação de desidrogenação do etilbenzeno; Preparation, characterization and evaluation of iron oxides and cobalt supported on activated carbon and polymeric catalysts for the dehydrogenation of ethylbenzene

OTTO, Carlos Rangel Neves
Fonte: Universidade Federal de Goiás; BR; UFG; Mestrado em Química; Educação em Química Publicador: Universidade Federal de Goiás; BR; UFG; Mestrado em Química; Educação em Química
Tipo: Dissertação Formato: application/pdf
POR
Relevância na Pesquisa
678.2659%
In this work were synthesized catalysts supported on activated carbons, which were obtained by carbonization of a polymer matrix. The precursor of activated carbon was the sulfonated styrene-divinylbenzene copolymer, which was synthesized by suspension polymerization in the presence of inert diluents to produce a macroporous network structure. The chemical modification was performed by sulfonation with concentrated sulfuric acid in the presence of dichloroethane. The supported catalysts were obtained by two routes. In the first one oxides were co-precipitated on the modified copolymer, and then the polymer was subjected to heat treatment and carbonization followed by activation. In the second route, the copolymer was first carbonized and subjected to activation, and then oxides were produced by co-precipitation of metalic ions. In both cases the coprecipitation involved two steps: incorporation of iron and cobalt ions through an ion exchange process and then coprecipitation in alkaline and oxidizer medium. The heat treatment consists of a heating step at 250 ° C in air atmosphere, carbonization at 900 ° C under nitrogen atmosphere and activation at 900 º C with a flow of nitrogen saturated with water vapor. The influence of the percentage of cobalt relative to iron in the material properties as well as catalytic activity in the reaction of dehydrogenation of ethylbenzene was investigated. The materials were characterized by their magnetism...

Study of activated carbon/methanol adsorption refrigeration tube and system integration.

Zhao, Yongling
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2011
Relevância na Pesquisa
680.7291%
Solid adsorption refrigeration systems are attracting much research interest because they have numerous advantages, such as using low grade thermal energy and being environment friendly. In recent decades many efforts have been put into developing various prototypes. The adsorption refrigeration tube (ART) is one such development. Through better system integration, a module consisting of a number of individually working ARTs can achieve significant refrigeration capacity, which may solve the vacuum leaking problem that besets large adsorption systems. In order to propose a feasible ART, this thesis undertakes a study of adsorptive properties of three types of activated carbon/methanol working pairs and modelling of the adsorption refrigeration cycle. In this examination of adsorptive properties, three activated carbon samples, Calgon 207C, 207EA and WS-480, were used to test and determine their pressure-temperature-concentration (P−T−x) relationship with methanol as the adsorbate. Based on the experimental data, three adsorption state equations, Langmuir equation, Freundlich equation and Dubinin-Astakov (D-A) equation, were compared in terms of their agreement with experimental data and their format impact on calculating coefficient of performance (COP) and refrigeration output (Qr)...

Unburnt carbon from coal fly ashes as a precursos of activated carbon for nitric oxide removal

Rubio Villa, Begoña; Izquierdo Pantoja, María Teresa
Fonte: Elsevier Publicador: Elsevier
Tipo: Artículo Formato: 1543247 bytes; application/pdf
ENG
Relevância na Pesquisa
680.2541%
The aim of this work is to evaluate the characteristics of an activated carbon obtained from unburnt carbon in coal fly ashes to be used in the removal of NO. Carbon-rich fraction was obtained by mechanical sieving of fly ashes. The mineral matter was removed by conventional HCl and HF desmineralization procedure. Activation was carried out with steam at 900ºC in order to develop porosity onto the sample. Characterization of samples was performed by several techniques with a main objective: to follow the mineral matter content, composition and distribution on the samples in order to better understand how to remove it from unburnt carbon in fly ashes. To study the use of this unburnt carbon as a precursor for the preparation of activated carbons for gas cleaning, the NO removal by ammonia using activated carbon as a catalyst at low temperature was performed. Results show a good performance of activated carbon in this reaction that is in relationship with BET surface area.; Spanish Ministry of Education and Science (REN2003-00770); Peer reviewed

Use of an activated carbon from antibiotic waste for the removal of Hg(II) from aqueous solution

Budinova, Temenuzhka; Petrov, Nartzislav; Parra Soto, José Bernardo; Baloutzov, Venelin
Fonte: Elsevier Publicador: Elsevier
Tipo: Artículo Formato: 22195 bytes; application/pdf
ENG
Relevância na Pesquisa
676.2835%
8 pages, 6 figures, 4 tables.-- PMID: 17428604 [PubMed].-- Available online Apr 10, 2007.; Porous carbon has been prepared from waste antibiotic material by a chemical activation method using K2CO3 as an activating reagent. Carbon was studied systematically by the adsorption of nitrogen and iodine. It was found that the process parameters such as activation temperature and activation time are crucial for preparing high-quality activated carbon. The proper choice of the preparation conditions allows to produce microporous activated carbon with a micropore volume up to 0.492 cm3/g and a BET surface area of 1260 m2/g. Adsorption of mercury(II) from an aqueous solution on antibiotic carbon was investigated under the varying conditions of agitation time, metal ion concentration and pH. The adsorption capacity of the carbon is 129 mg/g.; Financial support from The Ministry of Education and Science (project CC-1401) is gratefully acknowledged.; Peer reviewed

Removal of water pollutants by adsorption on activated carbon prepared from olive-waste cakes and by biological treatment using ligninolytic fungi

Baccar Ep Yangui, Rim
Fonte: [Barcelona] : Universitat Autònoma de Barcelona, Publicador: [Barcelona] : Universitat Autònoma de Barcelona,
Tipo: Tesis i dissertacions electròniques; info:eu-repo/semantics/doctoralThesis; info:eu-repo/semantics/publishedVersion Formato: application/pdf
Publicado em //2014 ENG
Relevância na Pesquisa
685.7333%
Se utilizan diferentes procesos para el tratamiento de las aguas residuales. Sin embargo, estas tecnologías son ineficaces, generan productos secundarios o son demasiado caras. El objetivo principal de esta tesis es la eliminación de diversos contaminantes del agua, incluyendo metales, tintes y productos farmacéuticos mediante dos tecnologías. La primera consiste en un tratamiento físico-químico de adsorción sobre carbón activo preparado a partir de un resido de la industria agroalimentaria. El segundo se trata de un tratamiento biológico con hongos. En cuanto a la adsorción sobre carbón activo, en una primera etapa se consideran aspectos tales como la preparación del adsorbente, su caracterización y el estudio del impacto ambiental asociado a su producción. Para la preparación de carbón activo se realiza la activación química a partir de orujo de oliva, utilizando ácido fosfórico como agente deshidratante. Se varían los parámetros principales del proceso para optimizar las condiciones de la activación. El carbón activo preparado, se caracteriza teniendo en cuenta sus propiedades de adsorción, su estructura química y su morfología. Los resultados muestran que el adsorbente más eficaz es el que se obtiene bajo las siguientes condiciones: una concentración igual a 60% de H3PO4...

Production, Characterization and Application of Activated Carbon from Nutshell for Adsorption of Methylene Blue; Produção, Caracterização e Aplicação de Carvão Ativado de Casca de Nozes para Adsorção de Azul de Metileno

Patrícia D. de Costa; Universidade do Extremo Sul Catarinense; Luana M. Furmanski; Universidade do Extremo Sul Catarinense; Lucas Dominguini; Instituto Federal de Santa Catarina
Fonte: Revista Virtual de Química Publicador: Revista Virtual de Química
Tipo: ; Formato: binary/octet-stream
Publicado em 08/07/2015 PT
Relevância na Pesquisa
679.7443%
In this paper is reported the preparation of an activated carbon from an agricultural waste, rich in carbon, the nutshell. Physical activation by pyrolysis and physic-chemical activation with pyrolysis and chemical treatment were used for the preparation of the activated carbon. The material was characterized in relation to amount of carbon and ash, thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and surface area (BET). The results showed that the coal produced had carbon content above 78 %, with a surface area around 400 m2.g-1 and high thermal stability and morphology honeycomb type. Tests for the adsorption capacity of methylene blue showed a capacity of 68 mg.g-1 for the activated carbon produced without chemical treatment and a capacity of 104 mg.g-1 for activated carbon treated with a chemical activation with ZnCl2. Thus, the material showed promise in the removal of methylene blue in aqueous solution.; Neste trabalho, foi preparado um carvão ativado a partir de um resíduo agrícola, rico em carbono, a casca de noz. Ativação física por pirólise e ativação físico-química foram usadas para a preparação dos carvões ativados. O material foi caracterizado em relação ao teor de carbono e cinzas...

Effect of ozonation on the activated carbon surface chemical properties and on 2-mercaptobenzothiazole adsorption

Valdes,H.; Sanchez-Polo,M.; Zaror,C.A.
Fonte: Latin American applied research Publicador: Latin American applied research
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/07/2003 EN
Relevância na Pesquisa
678.3517%
Benzothiazoles are organic compounds that may produce negative environmental impact when released into watercourses. In particular, 2-mercaptobenzothiazole (MBT) are known to be toxic and hard to biodegrade. Activated carbon adsorption and ozonation have been identified as suitable treatment for those contaminants. However, there is some controversy about the effect of carbon surface chemical composition on the MBT adsorption. This paper focuses on this issue and presents experimental adsorption isotherms for MBT on Filtrasorb-400 activated carbon treated with different ozone doses. The activated carbon surface chemical properties were assessed by acid/basic neutralization, temperature programmed desorption (TPD), X-ray photoelectron spectroscopy (XPS), and the point of zero charge (pH PZC). Results show that ozone treatment modified the oxygenated groups on the activated carbon surface, increasing the concentration of acid groups, and reducing the pH PZC. Finally, ozone treatment led to a significant reduction of the carbon's MBT adsorption capacity, due to the increase in polar hydrophilic groups.

Refuse Derived Energy-Tea Derived Boric Acid Activated Carbon as an Electrode Material for Electrochemical Capacitors

Kalyani,P.; Anitha,A.
Fonte: Sociedade Portuguesa de Electroquímica Publicador: Sociedade Portuguesa de Electroquímica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/05/2013 EN
Relevância na Pesquisa
678.2659%
Based on the energy form waste concepts we present here our results of the study of utilizing waste tea dust for preparing carbon, called the biocarbon. Tea dust after decocting has been selected as a low cost source of producing the carbon. Un-activated and activated carbons are produced by heating the tea waste around 250 °C for 2 h. For the first time, boric acid (H3BO3) has been reported through this work as a chemical agent for activating the selected biowaste. After physical characterization, the biocarbons have been tested in 3M KOH electrolyte solution for the possible application as electrodes in electrochemical double layer capacitors (EDLCs). Cyclic voltammetric studies with boric acid activated carbon of tea show slight improvement in the capacitance values over un-activated tea derived carbon. The study suggests that boric acid may be used as an activating agent for producing activated carbons.

The preparation of activated carbon from South African coal

Campbell,Q.P.; Bunt,J. R.; Kasaini,H.; Kruger,D.J.
Fonte: Journal of the Southern African Institute of Mining and Metallurgy Publicador: Journal of the Southern African Institute of Mining and Metallurgy
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2012 EN
Relevância na Pesquisa
684.35664%
Activated carbons used in the precious metals extraction industry are characterized by large internal surface areas and a great affinity for metal ions. The purpose of this research is to prepare activated carbon from a South African bituminous coal by physical activation that is suitable and cost-effective for use in the extraction of metals. The quality of the coal-based activated carbon may not prove to be as good as activated carbon produced from other traditional sources, but the production costs involved may make South African coal a feasible alternative feedstock. The activated carbons produced were characterized by Brunauer, Emmett, and Teller (BET) surface area, activated carbon pH, and phenol adsorption studies and the results compared to the results from a commercially available activated carbon, Norit RO 0.8 (control sample). Bituminous coals from various sources including Witbank Seam 4 and Free State coal were used in this study. The preparation method chosen was physical activation using superheated steam. The effects of process variables such as activation time (1-3 h) and temperature (600-800ºC) were studied in order to optimize those parameters. The activated carbon surface area was characterized by means of nitrogen adsorption isotherms at 77K. BET surface area analysis showed that Witbank Seam 4 coal activated at a temperature of 800ºC and activation time of 3 hours resulted in a surface area of 340 m²/g. Quality control of each sample was performed by measuring the pH of a known amount of the prepared activated carbon in distilled water over time. Results showed that the pH of some of the prepared activated carbons reached a value of 11. Phenol adsorption results for the different activated carbons prepared corresponded well to the results obtained for the Norit RO 0.8 activated carbon sample.

The application of activated carbon for the adsorption and elution of platinum group metals from dilute cyanide leach solutions

Snyders,C.A.; Mpinga,C.N.; Bradshaw,S.M.; Akdogan,G.; Eksteen,J.J.
Fonte: Journal of the Southern African Institute of Mining and Metallurgy Publicador: Journal of the Southern African Institute of Mining and Metallurgy
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/05/2013 EN
Relevância na Pesquisa
679.25234%
The research presented in this paper investigated the practical aspects of the recovery of platinum group metals (PGMs) from a dilute cyanide leach solution containing base metals, in a manner similar to that used for gold extraction in a typical CIP process, and focuses on both the adsorption and elution stages. The carrier-phase extraction of precious metals using activated carbon offers significant advantages over other processes in terms of simplicity, the high pre-concentration factor, rapid phase separation, and relatively low capital and operating costs. As a sorbent, activated carbon is still by far the most important material because of its large surface area, high adsorption capacity, porous structure, negligible environmental toxicity, low cost, and high purity standards. Adsorption tests were conducted on a pregnant alkaline leach solution (0.15 ppm Pt, 0.38 ppm Pd, 0.1 ppm Au) resulting from cyanide extraction performed in column leach tests. The initial adsorption rates of Pt, Pd, and Au were very fast and recoveries of these three metals were approximately 90 per cent after 2 hours, and 100 per cent for Pt, 97.4 per cent for Pd, and 99.9 per cent for Au after 72 hours. The parameters that influence the extraction of PGMs and Au were examined to assess their relative importance during the adsorption process in order to provide the basis for process optimization. The concentration of thiocyanate was not identified as significant factor for PGMs adsorption...