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Influência dos íons cloreto na cinética de redução eletroquímica dos íons de Bi+3 e CU2+ no eletrodo de mercúrio; Influence of chloride ions on the electrochemical reduction of Bi3+ and Cu2+ ions on mercury electrode

Agostinho, Silvia Maria Leite
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 03/11/1975 PT
Relevância na Pesquisa
411.99105%
A influência de pequenas concentrações de íons cloreto na cinética de redução eletroquímica dos íons Bi3+ e Cu2+ foi estudada através de medidas independentes de adsorção específica e de cinética eletroquímica. A adsorção específica foi determinada por meio das curvas eletrocapilares obtidas com o método do tempo de gota, para soluções aquosas de misturas de ácido clorídrico xM e de ácido perclórico (1 - x)M. Obeservou-se que, em concentrações de cloreto muito baixas, iguais ou inferiores a 10-2 M, a adsorção específica desses íons segue a isoterma de adsorção de Henry. A cinética da redução eletroquímica dos íons de Bi3+ e Cu2+, na presença de pequenas concentrações de íons cloreto, em meio de ácido perclórico 1 M, foi estudada por polarografia com o eletrodo de mercúrio. Os valores das constantes de velocidade foram calculados, a partir da relação existente entre a corrente, medida em cada potencial, e a corrente de difusão, usando as equações relativas a processos de eletrodos irreversíveis. Estes valores mostraram que, para as concentrações mais baixas de cloreto estudadas, esses íons aceleram as reações Bi3+ + 3e → Bi(Hg) e Cu2+ + 2e → Cu(Hg). O mecanismo de redução...

Estudos de adsorção e equilíbrio nos sistemas Cd(II) / SCN-/ C6H12N4 e Cd(II)/I-/SCN-. aperfeiçoamento de métodos e eletrodo; Adsorption and equilibrium studies of the systems Cd(II)/SCN-/C6N12H14 and Cd(II)/I-/SCN-. Improvement of methods and of the electrode

Angnes, Lucio
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 07/12/1987 PT
Relevância na Pesquisa
414.5303%
Na presente tese investigou-se a adsorção induzida de um cátion metálico (cádmio(II)) na presença simultânea de dois ligantes (um pseudo-haleto e uma amina ou haleto) na interface eletrodo de mercúrio/solução aquosa, com vistas a uma melhor compreensão desse processo. Os estudos de adsorção foram precedidos por estudos de equilíbrio dos compostos de coordenação formados em solução aquosa. Medidas experimentais foram feitas por potenciometria com eletrodo de amálgama, em força iônica 1,00 M, ajustada com NaCl04. Análise dos dados por programas computacionais adequados levou à quantificação das constantes de estabilidade de 7 espécies binárias e 9 espécies mistas para o sistema Cd(II)/ SCN-/C6H12N4 e de 8 espécies binárias e 6 mistas para o sistema Cd(II)/I-/SCN-, sendo todas estas espécies mononucleares. Para possibilitar um maior grau de automação das medidas cronocoulométricas de adsorção, o eletrodo de gota pendente de mercúrio, anteriormente desenvolvido no IQ-USP, teve seu sistema mecânico aperfeiçoado e passou a ser controlado por computador. O "software" se incumbe de calcular e comandar o tempo de abertura da micro-válvula do eletrodo para gerar gotas com a área solicitada. Aproveitando a possibilidade de realizar aquisição (de dados de carga durante e após a formação das gotas de mercúrio...

Hexagonal mesoporous silica modified with 2-mercaptothiazoline for removing mercury from water solution

Evangelista, Sheila M.; DeOliveira, Ediniar; Castro, Gustavo R.; Zara, Luiz F.; Prado, Alexandre G. S.
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 2194-2202
ENG
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A method for the attachment of 2-mercaptothiazoline (MTZ) to modified silica gel has been developed. In the first step, a new silylant agent was synthesized, named SiMTZ, by the reaction between MTZ molecule and chloropropyltrimethoxysilane (SiCl). SiMTZ and tetraethylortosilicate were co-condensed in the presence of n-dodecylamine, a neutral surfactant template, to produce a modified ordered hexagonal mesoporous silica named HMTZ. The modified material contained 0.89 +/- 0.03 mmol of 2-mercaptothiazoline per gram of silica. FT-IR, FT-Raman, Si-29- and C-13-NMR spectra were in agreement with the proposed structure of the modified mesoporous silica in the solid state. HMTZ material has been used for divalent mercury adsorption from aqueous solution at 298 I K. The series of adsorption isotherms were adjusted to a modified Langmuir equation. The maximum number of moles of mercury adsorbed gave 2.34 +/- 0.09 mmol/g of material. The same interaction was followed by calorimetric titration on an isoperibol calorimeter. The HMTZ presented a high capacity for the removal of the contaminant mercury from water. The Delta H and Delta G values for the interaction were determined to be -56.34 +/- 1.07 and -2.14 +/- 0.11 kJ mol(-1). This interaction process was accompanied by a decrease of entropy value (- 182 J mol(-1) K-1). Thus...

Factors affecting Hg (II) adsorption in soils from the Rio Negro basin (Amazon)

Miretzky, Patricia; Bisinoti, Márcia Cristina; Jardim, Wilson F.; Rocha, Júlio César
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: 438-443
ENG
Relevância na Pesquisa
405.6543%
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Mercury (II) adsorption studies in top soils (top 10 cm) from the Rio Negro basin show this process depends strongly on some selected parameters of the aqueous phase in contact with the soils. Maximum adsorption occurred in the pH range 3.0-5.0 (>90%). Dissolved organic matter shows an inhibitory effect on the availability of Hg (II) to be adsorbed by the soils, whereas a higher chloride content of the solution resulted in a lower adsorption of Hg (II) at pH 5.0. Soils with higher organic matter content were less affected by changes in the salinity. An increase in the initial Hg (II) concentration increased the amount of Hg (II) adsorbed by the soil and decreased the time needed to reach equilibrium. A Freundlich isotherm provided a good model for Hg (II) adsorption in the two types of soil studied. The kinetics of Hg (II) adsorption on Amazonian soils showed to be very fast and followed pseudo-second order kinetics. An environmental implication of these results is discussed under the real scenario present in the Negro River basin, where acidic waters are in contact with a soil naturally rich in mercury.

Preparation of a clay-modified carbon paste electrode based on 2-thiazoline-2-thiol-hexadecylammonium sorption for the sensitive determination of mercury

Dias Filho, Newton L.; Do Carmo, Devaney R.; Gessner, Fergus; Rosa, André H.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 1309-1316
ENG
Relevância na Pesquisa
408.26113%
A montmorillonite from Wyoming-USA was used to prepare an organo-clay complex, named 2-thiazoline-2-thiol-hexadecyltrimethylammonium-clay (TZT-HDTA-clay), for the purpose of the selective adsorption of the heavy metals ions and possible use as a chemically modified carbon paste electrode (CMCPE). Adsorption isotherms of Hg 2+, Pb 2+, Cd 2+, Cu 2+, and Zn 2+ from aqueous solutions as a function of the pH were studied at 298 K. Conditions for quantitative retention and elution were established for each metal by batch and column methods. The organo-clay complex was very selective to Hg(II) in aqueous solution in which other metals and ions were also present. The accumulation voltammetry of Hg(II) was studied at a carbon paste electrode chemically modified with this material. The mercury response was evaluated with respect to the pH, electrode composition, preconcentration time, mercury concentration, cleaning solution, possible interferences and other variables. A carbon paste electrode modified by TZT-HDTA-clay showed two peaks: one cathodic peak at about 0.0 V and an anodic peak at 0.25 V, scanning the potential from -0.2 to 0.8 V (0.05 M KNO 3 vs. Ag/AgCl). The anodic peak at 0.25 V presents excellent selectivity for Hg(II) ions in the presence of foreign ions. The detection limit was estimated as 0.1 μg L -1. The precision of determination was satisfactory for the respective concentration level. 2005 © The Japan Society for Analytical Chemistry.

Towards the abatement of environmental mercury pollution: An electrochemical characterization

Giannetti, B. F.; Moreira, W. A.; Bonilla, S. H.; Almeida, CMVB; Raboczkay, T.
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 213-220
ENG
Relevância na Pesquisa
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Electrochemical experiments in acetic acid-acetate buffer (pH 4.5) are conducted in order to understand metallic and ionic mercury adsorption processes on the pyrite surface. The nature as well as the extent of the spontaneous interaction between pyrite and mercuric ions was evaluated. The spontaneous reduction of mercury species onto pyrite surface was confirmed. These results represent a first step for the use of mining wastes rich in pyrite for mercury pollution abatement. (c) 2005 Elsevier B.V. All rights reserved.

Adsorção competitiva dos ions cobre e mercurio em membranas de quitosana natural e reticulada; Competitive adsorption of copper and mercury ions on natural and crosslinked chitosan membranes

Rodrigo Silveira Vieira
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 28/02/2008 PT
Relevância na Pesquisa
521.85133%
Nos últimos anos, a quitosana, um polissacarídeo linear obtido através da desacetilação da quitina, tem sido descrito como um biopolímero para remoção de metais pesados a partir de efluentes industrias, devido a presença de grupos amino e hidroxilas em suas estruturas, os quais podem atuar como sitios ativos. Vários métodos têm sido utilizados para modificar a quitosana natural, como reticulação com glutaraldeído (GLA) ou eplicloridrina (ECH). As propriedades de adsorção de diferentes espécies metálicas individuais vêm sendo largamente estudadas, embora, a maioria dos efluentes industriais não contenha somente uma espécie metálica, mas várias. Este trabalho foi proposto objetivando-se investigar o fenômeno de adsorção em um sistema binário sintético, constituído dos íons Hg(II) e Cu(II), utilizando-se quitosana natural ou reticulada como bioadsorvente. Membranas de quitosana foram obtidas e seguiu-se com o levantamento das propriedades cinéticas e de equilíbrio, em sistemas monocomponentes e de mistura. O estudo de equilíbrio monocomponente mostrou que a quitosana possui maior afinidade pelos íons Hg(II) quando comparado aos íons Cu(II). Observou-se que a reticulação aumentou a capacidade de adsorção. Para os sistemas de misturas pôde-se observar que o Hg é menos afetado pela presença de Cu. Usando somente dados monocomponentes de equilíbrio os efeitos de adsorção competitiva dos diferentes íons na mistura foram avaliados utilizando o modelo de Langmuir Estendido e a Teoria da Solução Adsorvida Ideal (IAST). A modelagem da cinética de adsorção mostrou que a difusão externa (efeito de filme) é menos significativa que a difusão intrapartícula para íons Cu(II)...

Adsorption of Aqueous Mercury(II)Species by Commercial Activated Carbon Fibres with and without Surface Modification

Nabais, Joao; Carrott, Peter; Ribeiro Carrott, Manuela; Silvestre, Sara; Duran-Valle, Carlos
Fonte: Universidade de Évora Publicador: Universidade de Évora
Tipo: Artigo de Revista Científica Formato: 66254 bytes; application/pdf
ENG
Relevância na Pesquisa
508.80348%
The adsorption of HgCl2, [HgCl4]2– and Hg2+ onto a series of activated carbon fibres was studied. These included the as-received commercial activated carbon fibre (K), that obtained after modification via by sulphuric acid oxidation (KAC) and that obtained after modification by reaction with pentaethylenehexamine (KBAS). The effects of concentration (10–1500 mg/l), solution pH (1–10) and temperature (25°C, 35°C and 45°C) were studied. The mercury(II) adsorption isotherms followed the Langmuir model with maximum adsorption capacities of 361.0, 142.2 and 300.3 mg/g for HgCl2, [HgCl4]2– and Hg2+, respectively. Fibre K proved to have the highest adsorption capacity towards HgCl2 but the best results for the adsorption of [HgCl4]2– and Hg2+ were obtained with the fibre KAC. The performance of fibre KBAS was always worse than those of the other two fibres tested. The negative values obtained for ΔH0 and ΔG0 indicate that the adsorption was an exothermic and spontaneous process and also demonstrated that the adsorption of Hg(II) is a feasible process.

Mercury Removal from Aqueous Solution and Flue Gas by Adsorption on Activated Carbon Fibres

Nabais, Joao; Carrott, Peter; Ribeiro Carrott, Manuela
Fonte: Universidade de Évora Publicador: Universidade de Évora
Tipo: Artigo de Revista Científica Formato: 28711 bytes; application/pdf
ENG
Relevância na Pesquisa
500.9568%
The use of two activated carbon fibres, one laboratorial sample prepared from a commercial acrylic textile fibre and one commercial sample of Kynol1, as prepared/received and modified by reaction with powdered sulfur and H2S gas in order to increase the sulfur content were studied for the removal of mercury from aqueous solution and from flue gases from a fluidized bed combustor. The sulfur introduced ranged from 1 to 6 wt.% depending on the method used. The most important parameter for the mercury uptake is the type of sulfur introduced rather than the total amount and it was found that the H2S treatment of ACF leads to samples with the highest mercury uptake, despite the lower sulfur amount introduced. The modified samples by both methods can remove HgCl2 from aqueous solutions at pH 6 within the range 290–710 mg/g (ACF) which can be favourably compared with other studies already published. The use of a filter made with an activated carbon fibre modified by powdered sulfur totally removed the mercury species present in the flue gases produced by combustion of fossil fuel.

Influence of surface ionization on the adsorption of aqueous mercury chlorocomplexes by activated carbons

Nabais, Joao; Carrott, Peter; Ribeiro Carrott, Manuela
Fonte: Universidade de Évora Publicador: Universidade de Évora
Tipo: Artigo de Revista Científica Formato: 62228 bytes; application/pdf
ENG
Relevância na Pesquisa
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The adsorption of aqueous mercury species from chloride solutions on a number of activated carbons has been studied. It was found that whereas the adsorption of neutral HgCl, or positive Hg’+ was very low, significant quantities of the tetrachloromercury(I1) complex, HgCI$-, were adsorbed. Adsorption isotherms of this complex were measured at different pH values, and the results analysed by the Langmuir equation and by a simple surface ionization and specific adsorption model in order to obtain estimates of the adsorption stoichiometry and the mean free energy of adsorption.

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
407.98195%
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.

Mercury adsorption on natural and organofunctionalized smectites - thermodynamics of cation removal

Guerra,Denis L.; Santos,Maria R. M. C.; Airoldi,Claudio
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2009 EN
Relevância na Pesquisa
502.01547%
A natural smectite clay sample from Piauí State, Brazil, was organofunctionalized with 3-mercaptopropyltrimethoxysilane and 3-aminopropyltriethoxysilane silyating agents. The basal spacing of 0.99 nm and surface area of 48 m² g-1 for natural clay increased to 1.84 and 2.01 nm, and 781 and 795 m² g-1 for modified clays, respectively. The natural and chemically immobilized clay samples adsorb mercury cations from aqueous solutions at pH 3.0 at 298 ± 1 K. The Langmuir, Redlich-Peterson and Toth adsorption isotherm models were applied to fit the experimental data with a nonlinear approach. From the cation/basic center interactions for each smectite at the solid-liquid interface, by using calorimetry methodology, the equilibrium constant and exothermic thermal effects were obtained. By considering the net interactive number of moles for each cation and the equilibrium constant, the enthalpy, "intHº (-11.98 to -13.93 kJ mol-1) and negative free Gibbs energy, "intGº (-22.4 ± 0.1 to -23.9 ± 0.1 kJ mol-1) were calculated. These values enabled the determination of positive entropy, "intSº (51 ± 01 to 55 ± 2 J K-1 mol-1). The cation-basic center interactions are spontaneous in nature as demonstrated from favorable enthalpic and entropic results. Natural and anchored smectites have the ability to complex mercury...

Adsorption of mercury (II) from liquid solutions using modified activated carbons

Silva,Hugo Soé; Ruiz,Silvia Virginia; Granados,Dolly Lucía; Santángelo,Juan Manuel
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2010 EN
Relevância na Pesquisa
415.6465%
Mercury is one of the most toxic metals present in the environment. Adsorption has been proposed among the technologies for mercury abatement. Activated carbons are universal adsorbents which have been found to be a very effective alternative for mercury removal from water. The effectiveness with which a contaminant is adsorbed by the solid surface depends, among other factors, on the charge of the chemical species in which the contaminant is in solution and on the net charge of the adsorbent surface which depend on the pH of the adsorption system. In this work, activated carbon from carbonized eucalyptus wood was used as adsorbent. Two sulphurization treatments by impregnation with sulphuric acid and with carbon disulphide, have been carried out to improve the adsorption capacity for mercury entrapment. Batch adsorption tests at different temperatures and pH of the solution were carried out. The influence of the textural properties, surface chemistry and operation conditions on the adsorption capacity, is discussed.

Functionalized diatom silica microparticles for removal of mercury ions

Yu, Y.; Addai-Mensah, J.; Losic, D.
Fonte: Institute of Physics Publishing Ltd Publicador: Institute of Physics Publishing Ltd
Tipo: Artigo de Revista Científica
Publicado em //2012 EN
Relevância na Pesquisa
513.68504%
Diatom silica microparticles were chemically modified with self-assembled monolayers of 3-mercaptopropyl-trimethoxysilane (MPTMS), 3-aminopropyl-trimethoxysilane (APTES) and n-(2-aminoethyl)-3-aminopropyl-trimethoxysilane (AEAPTMS), and their application for the adsorption of mercury ions (Hg(II)) is demonstrated. Fourier transform infrared spectroscopy and x-ray photoelectron spectroscopy analyses revealed that the functional groups (–SH or –NH2) were successfully grafted onto the diatom silica surface. The kinetics and efficiency of Hg(II) adsorption were markedly improved by the chemical functionalization of diatom microparticles. The relationship among the type of functional groups, pH and adsorption efficiency of mercury ions was established. The Hg(II) adsorption reached equilibrium within 60 min with maximum adsorption capacities of 185.2, 131.7 and 169.5 mg g-1 for particles functionalized with MPTMS, APTES and AEAPTMS, respectively. The adsorption behavior followed a pseudo-second-order reaction model and Langmuirian isotherm. These results show that mercapto- or amino-functionalized diatom microparticles are promising natural, cost-effective and environmentally benign adsorbents suitable for the removal of mercury ions from aqueous solutions.; Yang Yu...

Graphene-diatom silica aerogels for efficient removal of mercury ions from water

Kabiri, S.; Tran, D.N.H.; Azari, S.; Losic, D.
Fonte: American Chemical Society Publicador: American Chemical Society
Tipo: Artigo de Revista Científica
Publicado em //2015 EN
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414.0968%
A simple synthetic approach for the preparation of graphene-diatom silica composites in the form of self-assembled aerogels with three-dimensional networks from natural graphite and diatomite rocks is demonstrated for the first time. Their adsorption performance for the removal of mercury from water was studied as a function of contact time, solution pH, and mercury concentration to optimize the reaction conditions. The adsorption isotherm of mercury fitted well with the Langmuir model, representing a very high adsorption capacity of >500 mg of mercury/g of adsorbent. The prepared aerogels exhibited outstanding adsorption performance for the removal of mercury from water, which is significant for environmental applications.; Shervin Kabiri, Diana N.H. Tran, Sara Azari, and Dusan Losic

Synthesis of nanoporous materials for preconcentration and determination of trace elements by ICP-AES ; Investigation and elimination of the memory effects of mercury, gold, silver and boron in ICP-AES

Chen, Wencan.
Fonte: Brock University Publicador: Brock University
Tipo: Electronic Thesis or Dissertation
ENG
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Nanoporous materials with large surface area and well-ordered pore structure have been synthesized. Thiol groups were grafted on the materials' surface to make heavy metal ion pre-concentration media. The adsorption properties ofthe materials were explored. Mercury, gold and silver can be strongly adsorbed by these materials, even in the presence of alkaline earth metal ion. Though the materials can adsorb other heavy metal ions such as lead and copper, they show differential adsorption ability when several ions are present in solution. The adsorption sequence is: mercury> == silver> copper » lead and cadmium. In the second part of this work, the memory effects of mercury, gold, silver and boron were investigated. The addition of 2% L-cysteine and 1% thiourea eliminates the problems of the three metal ions completely. The wash-out time for mercury dropped from more than 20 minutes to 18 seconds, and the wash-out time for gold decreased from more than 30 minutes to 49 seconds. The memory effect of boron can be reduced by the use of mannitol.

Caracterização e avaliação de argilas como adsorventes na remoção e eluição de íons cobre e mercúrio em diferentes sistemas; Characterization and evaluation of clays as adsorbents in removal and elution of copper and mercury ions in different systems

Ambrósio Florêncio de Almeida Neto
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 21/02/2011 PT
Relevância na Pesquisa
411.70562%
A remoção de metais pesados por argilas, baseada na tecnologia de purificação da água, tem sido investigada como uma alternativa aos métodos tradicionais. Argilas do tipo esmectítico são as de maior utilização industrial, sendo considerada a mais interessante das argilas industriais. Todavia em diversos casos faz-se necessário submetê-las a tratamentos físicos e químicos para aprimorar suas potencialidades. Assim, estudou-se, no presente trabalho a remoção dos íons cobre e mercúrio, em laboratório a partir de soluções sintéticas, a adsorção sobre as argilas calcinadas dos tipos Bofe e Verde-lodo. Tais íons são recorrentemente produzidos e acumulados no meio ambiente e sua recuperação, para posterior reuso, tem cada vez mais importância a medida que não apenas o tratamento da água residuária e necessário, mas o aproveitamento dos subprodutos e incentivado, por acarretar benefícios econômicos e ambientais. Dessa forma, estudos a respeito de técnicas de remoção dos íons metálicos, assim como do equilíbrio e da cinética do processo, são necessários para a viabilização do procedimento de recuperação. As técnicas de remoção abordadas nesse trabalho foram a de banho finito e de leito fixo e seus objetivos foram avaliar os mecanismos e taxas de remoção dos íons de cobre e mercúrio...

Preparation of a clay-modified carbon paste electrode based on 2-thiazoline-2-thiol-hexadecylammonium sorption for the sensitive determination of mercury

Dias Filho, Newton L.; Carmo, Devaney R. do; Gessner, Fergus; Rosa, André H.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 1309-1316
ENG
Relevância na Pesquisa
408.26113%
A montmorillonite from Wyoming-USA was used to prepare an organo-clay complex, named 2-thiazoline-2-thiol-hexadecyltrimethylammonium-clay (TZT-HDTA-clay), for the purpose of the selective adsorption of the heavy metals ions and possible use as a chemically modified carbon paste electrode (CMCPE). Adsorption isotherms of Hg 2+, Pb 2+, Cd 2+, Cu 2+, and Zn 2+ from aqueous solutions as a function of the pH were studied at 298 K. Conditions for quantitative retention and elution were established for each metal by batch and column methods. The organo-clay complex was very selective to Hg(II) in aqueous solution in which other metals and ions were also present. The accumulation voltammetry of Hg(II) was studied at a carbon paste electrode chemically modified with this material. The mercury response was evaluated with respect to the pH, electrode composition, preconcentration time, mercury concentration, cleaning solution, possible interferences and other variables. A carbon paste electrode modified by TZT-HDTA-clay showed two peaks: one cathodic peak at about 0.0 V and an anodic peak at 0.25 V, scanning the potential from -0.2 to 0.8 V (0.05 M KNO 3 vs. Ag/AgCl). The anodic peak at 0.25 V presents excellent selectivity for Hg(II) ions in the presence of foreign ions. The detection limit was estimated as 0.1 μg L -1. The precision of determination was satisfactory for the respective concentration level. 2005 © The Japan Society for Analytical Chemistry.

Fixed-bed column of surface modified activated carbons for adsorption of mercury (II) in aqueous solution

Silva,H.S.; Granados,D.L.; Ruiz,S.V.
Fonte: Latin American applied research Publicador: Latin American applied research
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/07/2012 EN
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507.93645%
Activated carbons are universal adsorbents that can be obtained from a wide variety of raw materials, and have been found to be very effective for mercury removal from water. This contribution presents a comparative adsorption in column study of activated carbons obtained by physical activation of carbonized eucalyptus wood with water vapour, as adsorbents of mercury in liquid phase. Two samples were treated with sulphuric acid and with carbon disulphide, in order to introduce sulphur as a heteroatom onto the adsorbent surface. Adsorption in column assays was performed and the breakthrough curves were used to compare their performance. The sulphurization treatments produce important variations on the textural properties of the solid, on the zero charge point, and on the number of acid and basic surface groups. From the analysis of these factors, the dependency of the adsorption capacity of a solid with the pH of the solution can be explained.

Adsorption of Mercury(II) onto activated carbons derived from Theobroma cacao pod husk

Kede,Charles M.; Ndibewu,Peter P.; Kalumba,Makonga M.; Panichev,Nikolay A.; Ngomo,Horace M.; Ketcha,Joseph M.
Fonte: South African Journal of Chemistry Publicador: South African Journal of Chemistry
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2015 EN
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416.66836%
Activated carbon prepared from Theobroma cacao pod husk was used as a low-costbiosorbent for the removal of mercury(II) from aqueous solutions. The influence of pH and contact time on the adsorption was investigated by conducting a series of batch adsorption experiments. The equilibrium data were fitted to the Langmuir and Freundlich isotherm models. The Langmuir isotherm was found to best describe the experimental data. The amount adsorbed increased with increasing temperature. The maximum adsorption capacity of mercury was found to be 10(5) ng g-1 for an initial mercury concentration of 100 ppb. The kinetics of adsorption were modelled by means of the Lagergren-first-order and pseudo-second-order models. The pseudo-second-order model was found to explain the adsorption kinetics most effectively. It was also found that pore diffusion played an important role in the adsorption, and intra-particle diffusion was the rate-limiting step during the first 30 min. A FTIR study revealed that the carbonyl and sulfur functional groups present on the surface of the adsorbing material were involved in chemical interaction with mercury(II).