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Search Results: 1 - 10 of 15676 matches for " Martins Afonso Henriques "
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Extra??o por solventes aplicada à recupera??o de cianetos
Andrade, Rodrigo Cristeli;Martins, Afonso Henriques;
Rem: Revista Escola de Minas , 2005, DOI: 10.1590/S0370-44672005000200011
Abstract: this technical note presents the preliminary experimental results at laboratory bench scale-up for the study involving the usage of commercial organic extractant cyanex 921? (trioctylfosfine oxide) diluted in xylene for cyanide extraction from pure alkaline aqueous solution with a chemical composition similar to a typical cyanidation liquor of a gold ore. the experimental results for only one contact stage showed that an increase of the cyanex 921? concentration in the organic phase improved the percent of cyanide extraction. besides, the zinc presence in the feed aqueous phase as complexing agent for cyanide also improved the cyanide extraction (38.48%) as compared to the result for the experiment without zinc (35.50%). the highest values for percent of cyanide extraction were obtained at the initial ph of the aqueous phase equals to 9.0.
Reciclagem de sucata de jóias para a recupera??o hidrometalúrgica de ouro e prata
Rojas, Carol Elizabeth Barrientos;Martins, Afonso Henriques;
Rem: Revista Escola de Minas , 2010, DOI: 10.1590/S0370-44672010000200016
Abstract: a great amount of scrap metal waste is lost in the manufacturing of gold jewelry due the lack of available knowledge for precious metal recovery in small jewelery shops. this study presents the experimental results on a bench laboratory scale of a hydrometallurgical route to treat gold jewelry scrap using samples with proportions that are higher and lower than 10% ag. the adopted route consisted of preliminary sampling, leaching with hno3 to extract the silver, followed by aqua regia leaching of a gold solid residue from the previous leaching stage to dissolve the contained gold. some typical parameters of the leaching stage were evaluated with the use of a statistical planning of experiments by "the complete factorial method" with two experimental levels. the optimum experimental conditions for the maximum metallic extraction were determined by "the ascending path method for statistical optimization". the leaching liquors were treated, aiming for the gold and silver recovery. the silver recovery (94%) occurred by the agcl calcination obtained with the nacl added to the hno3 liquor, and the gold recovery (98.7%) was obtained by the precipitation with the feso4 added to the aqua regia liquor.
Precipita??o de carbonato de cálcio para aplica??o industrial
Oliveira, Felipe Ventura;Martins, Afonso Henriques;
Rem: Revista Escola de Minas , 2009, DOI: 10.1590/S0370-44672009000200008
Abstract: this work presents the experimental results for precipitated calcium carbonate (pcc) synthesis over a ground calcium carbonate (gcc) substrate. the parameters [ca]/[co3]t initial ratio, aqueous synthesis solution temperature, ph and coagulant concentration (edta) were investigated. the samples were characterized by scanning electron microscopy (sem), total carbon (toc), specific surface area (bet method), particle size distribution and visible light reflectance (to measure the brightness of the samples). the results were compared with values from standard samples used in the paper industry. according to the experimental results, it was noted that an increase in the edta amount added to the pulp favored pcc homo-coagulation and also increased the size of the coagulum. pcc tends to homo-coagulate between ph 10 and 11, while it tends to precipitate over gcc particles between ph 8 and 9. a decreasing of the material density was also observed. values found for specific surface area can be considered acceptable by paper and plastics industries.
Avalia??o de alguns agentes lixiviantes para a remo??o do cobre contido em um minério complexo de ouro
Cunha, Fabiana Albuquerque;Martins, Afonso Henriques;
Rem: Revista Escola de Minas , 2003, DOI: 10.1590/S0370-44672003000300007
Abstract: some complexed gold ores present high percent of copper content and it inhibits the direct use of classical hydrometallurgical cyanidation process for gold recovery. this paper presents the experimental results of a hydrometallurgical route for gold ore pre-treatment aiming at extracting copper for further cyanidation. some experiments were carried out using h2so4, fe2(so4)3, h2o2, hcl, hclo4 and nh4oh. the highest percent of copper extracted (50%) was obtained for using sulfuric acid at 82 ± 2oc during 15 minutes, and using a combination of sulfuric acid and hydrogen peroxide at 25 ± 2oc during 15 minutes. the experimental results of this work were lower than 95% percent of copper extracted and considered unsuitable for the cyanidation stage and gold recovery.
Avalia o de alguns agentes lixiviantes para a remo o do cobre contido em um minério complexo de ouro
Cunha Fabiana Albuquerque,Martins Afonso Henriques
Rem: Revista Escola de Minas , 2003,
Abstract: Alguns minérios complexos de ouro e cobre apresentam a característica de possuírem elevados teores de cobre, inviabilizando a utiliza o direta do processo de cianeta o para extra o do ouro. Esse trabalho apresenta os resultados experimentais de uma rota hidrometalúrgica para o pré-tratamento do minério de ouro e cobre visando a maximizar a remo o de cobre e a viabilizar a etapa seguinte de cianeta o. Foram realizados experimentos de lixivia o utilizando H2SO4, Fe2(SO4)3, H2O2, HCl, HClO4 e NH4OH. Entre esses ensaios, as melhores extra es de cobre - próximas a 50% - foram obtidas em experimentos com dura o de 15 minutos utilizando ácido sulfúrico a 82 ± 2oC e uma combina o de ácido sulfúrico e peróxido de hidrogênio a 25 ± 2oC. Os resultados obtidos foram inferiores àquele percentual mínimo de extra o de cobre (aproximadamente 95%) necessário para viabilizar economicamente a etapa posterior de cianeta o para a extra o de ouro.
Regenera??o de cianetos pelo processo ARV associado ao emprego de resinas poliméricas de troca i?nica
Silva, Adriana Lara da;Costa, Rodrigo Alves;Martins, Afonso Henriques;
Rem: Revista Escola de Minas , 2002, DOI: 10.1590/S0370-44672002000200008
Abstract: this work presents the bench scale experimental results for the cyanide regeneration from pure alkaline aqueous solutions of gold, cooper and iron cyanocomplexes using the avr process associated to the ion exchange polymeric resins imac hp555sò ((room&haas-usa) and amberlite ira-420ò (room&haas brasil ltda.). the resin imac hp555sò adsorved 64.5% cn, 87.4% au, 64.9% cu and 60.5% fe from the alkaline solution containing metal cyanocomplexes. meanwhile, the elution stage with h2so4 and thiourea reached 31.2% cn, 86.2% au, 86.4% cu e 41.5% fe. the resin ira-420ò adsorbed 53.4% cn, 86.3% au, 83.8% cu and 86.0% fe under the same experimental conditions adopted for the resin imac hp555sò. the resin amberlite ira-420ò eluted 48% cn, 96.8% au, 9.1% cu and 76% fe.
Extra??o por solventes aplicada à remo??o de metais pesados presentes no licor de lixivia??o do minério de manganês da Mina do Azul (PA)
Carvalhido, Carlos Augusto;Pedrosa, Marcelo Ferreira;Martins, Afonso Henriques;
Rem: Revista Escola de Minas , 2001, DOI: 10.1590/S0370-44672001000300011
Abstract: the goal of this experimental work was to treat a manganese sulfate aqueous solution obtained from the sulfuric acid leaching of mina do azul manganese ore (brazil) to remove copper, nickel, cobalt and iron by solvent extraction using cyanex302ò solubilized in exxsol d-100ò. the experimental results for the individualized extraction stage were considered satisfactory and reached 98% zn, 92% ni and 77% fe, while more than 90% of manganese was kept in solution. the experimental conditions for maximum impurities extraction and minimum manganese extraction were 6.0% v/v cyanex302ò in the organic phase, 3 minutes of contact time between phases and an organic/aqueous phase ratio equal to 5.5. under these conditions, the results were 3.7% extraction of manganese, 77.1% iron, 89.7% zinc and 31.3% extraction of nickel.
Regenera o de cianetos pelo processo ARV associado ao emprego de resinas poliméricas de troca i nica
Silva Adriana Lara da,Costa Rodrigo Alves,Martins Afonso Henriques
Rem: Revista Escola de Minas , 2002,
Abstract: Esse trabalho apresenta os resultados da regenera o de cianetos, presentes em solu es aquosas com composi o química similar ao de efluentes típicos da cianeta o do ouro, através do processo AVR (Acidifica o, Volatiliza o, Reneutraliza o) associado ao emprego de resinas poliméricas ani nicas de troca i nica Imac HP555sò (Rohm&Haas Co.-USA) e Amberlite IRA-420ò (Room&Haas Química Ltda.-Brasil). A resina Imac HP555sò adsorveu 64,5% CN, 87,4% Au, 64,9% Cu e 60,5% Fe presentes em uma solu o alcalina mista de cianocomplexos metálicos. Na etapa de elui o com H2SO4 e tiouréia foram alcan ados 31,2% CN, 86,2% Au, 86,4% Cu e 41,5% Fe. A resina IRA-420ò, nas mesmas condi es experimentais do estudo da resina Imac HP555sò, adsorveu 53,4% CN, 86,3% Au, 83,8% Cu e 86,0% Fe. Em termos de elui o, a resina Amberlite IRA-420ò obteve 48% CN, 96,8% Au, 9,1% Cu e 76% Fe.
Extra o por solventes aplicada à remo o de metais pesados presentes no licor de lixivia o do minério de manganês da Mina do Azul (PA)
Carvalhido Carlos Augusto,Pedrosa Marcelo Ferreira,Martins Afonso Henriques
Rem: Revista Escola de Minas , 2001,
Abstract: O objetivo desse trabalho foi promover o tratamento hidrometalúrgico do licor de sulfato de manganês proveniente da lixivia o do minério de manganês da Mina do Azul (PA), através da remo o de cobre, níquel, cobalto e ferro presentes em solu o, via extra o por solventes. Foi empregado o CYANEX302 como extratante organico solubilizado em Exxsol D-100 . Os resultados obtidos para o sistema CYANEX302 em Exxsol D-100 foram satisfatórios, alcan ando percentuais individuais de extra o de 98% de zinco, 92% de níquel e 77% para o ferro, enquanto mais de 90% de manganês permaneceu em solu o. Nas condi es de máxima extra o conjunta de impurezas metálicas e mínima extra o de manganês, isto é, porcentagem de CYANEX302 na fase organica igual a 6,0%, tempo de contato entre as fases igual a 3 minutos e rela o fase organica e fase aquosa igual a 5,5, os resultados experimentais obtidos mostraram que 3,7% de manganês foram extraídos conjuntamente com 77,1% de ferro, 89,7% de zinco e 31,3% de níquel.
Sudden Death as the Outcome of Cardiac Arrest, in a Portuguese Region: Where Do Resuscitation Manoeuvres Stand?  [PDF]
Rosa Henriques de Gouveia, Adriana Martins, Duarte Nuno Vieira
World Journal of Cardiovascular Diseases (WJCD) , 2015, DOI: 10.4236/wjcd.2015.58026
Abstract: Cardiac Arrest (CA) is a major health problem, due to short and long-term sequel? and to associated mortality. Despite the improvement of out-of-hospital and in-hospital resuscitation manoeuvres, unexpected sudden fatal events occur. The authors reported the features of a series of sudden death (SD) cases where cardiopulmonary resuscitation (CPR) was performed. Files of 1053 medico-legal autopsies, from victims aged ≥18 years-old, were reviewed. Cardiac Arrest leading to Sudden Death were found in 477 cases (45.3%), but only 199 (42%) of these had been submitted to resuscitation manoeuvres. There was an elderly male predominance. Both non-cardiac and cardiac CA/SD causes were present, despite the higher coronary artery disease incidence. Both out-of-hospital and in-hospital events took place. Age, severity of the disease, comorbidities and predominance of out-of-hospital CA were obstacles to successful CPR, leading to SD. Knowing the population characteristics may help to improve Emergency Assistance.
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