oalib

Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99

Submit

Any time

2019 ( 224 )

2018 ( 365 )

2017 ( 374 )

2016 ( 559 )

Custom range...

Search Results: 1 - 10 of 286858 matches for " José R. Parga "
All listed articles are free for downloading (OA Articles)
Page 1 /286858
Display every page Item
Effect of Pretreatment of Sulfide Refractory Concentrate with Sodium Hypochlorite, Followed by Extraction of Gold by Pressure Cyanidation, on Gold Removal  [PDF]
Alejandro Valenzuela, Jesús L. Valenzuela, José R. Parga
Advances in Chemical Engineering and Science (ACES) , 2013, DOI: 10.4236/aces.2013.33021
Abstract:

The majority of the refractory gold and silver occurs in occlusion in sulphides, then precious metal dissolution is possible by first oxidizing auriferous sulfide concentrate using sodium hypochlorite-sodium-hydroxide solution followed of pressure cyanidation of the oxidized concentrate, for the extraction of precious metals. This process was conducted and evaluated under cyanide and oxygen pressure. This versatile approach offers many advantages, including low temperatures, low pressure and less costly materials of construction than conventional pressure oxidation. In this study, the effect of oxygen pressure, concentration of sodium hypochlorite, temperature, and initial pH, in precious metals recovery and As removal were evaluated using a 24 factorial design. Characterization of the ores showed that pyrite and arsenopyrite were the main minerals present on the concentrate. The best results for gold extraction were obtained with oxygen pressure of 80 psi, 10% (w/w) sodium hypochlorite, temperature of 80, at pH = 13, and a constant stirring speed of 600 rpm. These conditions allowed an approximated 60% of gold and 90% of silver extractions in 1 hr.

Copper and Cyanide Recovery in Cyanidation Effluents  [PDF]
José R. Parga, Jesús L. Valenzuela, Héctor Moreno, Jaime E. Pérez
Advances in Chemical Engineering and Science (ACES) , 2011, DOI: 10.4236/aces.2011.14028
Abstract: Cyanidation is the main process for gold and silver recovery from its ores. In this study, a process is proposed to recover copper and cyanide from barren solutions from the Merrill-Crowe cementation process with zinc dust. This technology is based on inducing nucleated precipitation of copper and silver in a serpentine reactor, using sodium sulfide as the precipitator, and sulfuric acid for pH control. Results show that pH value has a significant effect on copper cyanide removal efficiency, and it was determined the optimal pH range to be 2.5 - 3. At this pH value, the copper cyanide removal efficiency achieved was up to 97 and 99%, when copper concentration in the influent was 636 and 900 ppm. respectively. In this process (sulphidization-acidification-thickening-HCN recycling), the cyanide associated with copper cyanide complexes, is released as HCN gas under weakly acidic conditions, allowing it to be recycled back to the cyanidation process as free cyanide. Cyanide recovery was 90%. Finally, this procedure was successfully run at Minera William in México.
Copper Recovery from Barren Cyanide Solution by Using Electrocoagulation Iron Process  [PDF]
José R. Parga, Guillermo Tiburcio Munive, Jesús L. Valenzuela, Víctor V. Vazquez, Gregorio González Zamarripa
Advances in Chemical Engineering and Science (ACES) , 2013, DOI: 10.4236/aces.2013.32018
Abstract:

This paper is a brief overview of the role of inducing the nucleated electro winning of copper by using iron electrodes in electrocoagulation (EC) process. Cyanide compounds are widely used in gold ore processing plants in order to facilitate the extraction and subsequent concentration of the precious metal. Owing to cyanide solution employed in gold processing, effluents generated have high contents of free cyanide as well as copper cyanide complexes, which lend them a high degree of toxicity. In this regard, two options for the treatment of cyanide barren solutions has been used; in two ways; first for cyanide destruction by oxidation with the use of the EC process, in theory, has the advantage of decomposing cyanide at the anode and collecting copper simultaneously by a sludge of copper magnetic iron. In both cases excellent performance can be achieved using the high capacity of the bipolar iron EC technology. We found that it is possible to reduce the copper cyanide complex from 720 mg·l1 to below 10 mg·l1 within 20 minutes.

Kinetic Aspects of Gold and Silver Recovery in Cementation with Zinc Power and Electrocoagulation Iron Process  [PDF]
Gabriela V. Figueroa Martinez, José R. Parga Torres, Jesús L. Valenzuela García, Guillermo C. Tiburcio Munive, Gregorio González Zamarripa
Advances in Chemical Engineering and Science (ACES) , 2012, DOI: 10.4236/aces.2012.23040
Abstract: The Merrill-Crowe or Cementation process is used for concentration and purification of gold and silver from cyanide solutions. Among other available options for recovery of precious metals from cyanide solutions, Electrocoagulation (EC) is a very promising electrochemical technique for the recovery of this precious metals. In this work first, an introduction to the fundamentals of the Merrill Crowe and EC process are given, then Kinetic aspects conditions and results of the both process, for the removal of gold and silver from cyanide solutions are presented, and finally the characterization of the solid products formed during the EC process with X-ray Diffraction and SEM are shown. Results suggests that The cementation of both gold and silver by suspended zinc particles conforms to well-behaved fist order kinetics and for the EC process the results show that is an excellent option to remove Au and Ag from cyanide solution by using iron electrodes. Finally, 99.5% of gold and silver were removed in the experimental EC reactor, and it was achieved in 5 minutes or less.
New Approach for Lead, Zinc and Copper Ions Elimination in Cyanidation Process to Improve the Quality of the Precipitate  [PDF]
José R. Parga, Jesús V. Valdés, Jesús L. Valenzuela, Gregorio Gonzalez, L. María de J. Pérez, T. Francisco Cepeda
Materials Sciences and Applications (MSA) , 2015, DOI: 10.4236/msa.2015.62015
Abstract: The Merrill-Crowe zinc-precipitation process has been applied worldwide on a large number of operations for recovering gold and silver from cyanide solutions. However, in some of the large plants this precipitate is of low quality, because copper and especially lead are precipitated along with gold and silver resulting in a higher consumption of zinc powder, fluxes in the smelting of the precipitate, formation of mate and short life for crucibles. In this research, a method is proposed to recover lead, zinc and copper cyanide ions from barren solutions, from the Merrill-Crowe process with hydroxyapatite before the filter press. This technology is based on inducing nucleated precipitation of zinc, copper and silver ions in a serpentine reactor, using sodium sulfide as the precipitator and sulfuric acid for pH control. This procedure was successfully applied at WILLIAM Mining and BACIS Mining Group in México.
Uso de Resina de Intercambio Aniónico para la Recuperación del Complejo Oro Tiosulfato desde Soluciones Acuosas
Chaparro,Miriam E; Valenzuela,Jesús L; Munive,Guillermo T; Parga,José R;
Información tecnológica , 2012, DOI: 10.4067/S0718-07642012000200007
Abstract: the adsorption and elution of gold in thiosulfate-ammonia media were studied using the resin aurix?100, evaluating some variables that affect the kinetico of the process, such as: temperature, stirring speed, ph, thiosulfate concentration (nh4)2s2o3 and gold concentration. the study was carried out in a batch reactor and an ion exchange column. the operation conditions that presented better results of gold extraction at 25°c were: ph=10.5, stirring opeed=500 rpm, [au]=1 mg/l, [(nh4)2s2o3]=0.04 m, and 5 gramo of resin. the results indicate that by increasing [(nh4)2s2o3] favors the adsorption by 99% during three hours, being noticeably affected by the presence of ammonia. the conditions with results on the column at 25°c were, ph= 10.5, [au]=1 mg/l.
Uso de Resina de Intercambio Aniónico para la Recuperación del Complejo Oro Tiosulfato desde Soluciones Acuosas Use of Anion Exchange Resin for the Recovery of the Complex Gold Thiosulfate from Aqueous Solutions
Miriam E Chaparro,Jesús L Valenzuela,Guillermo T Munive,José R Parga
Información Tecnológica , 2012,
Abstract: Se estudió la adsorción de oro utilizando la resina AuRIX 100 en medio tiosulfato de amonio, evaluando algunas variables que afectan la cinética del proceso tales como: temperatura, velocidad de agitación, pH, concentración de tiosulfato de amonio (NH4)2S2O3 y concentración de oro. El estudio se llevó a cabo en un reactor batch y una columna de intercambio iónico. Las condiciones de operación que presentaron mejores resultados de extracción de oro a 25°C, fueron: pH=10.5, velocidad de agitación=500 rpm, [Au]=1 mg/l, [(NH4)2S2O3]=0.04 M, 5 gramos de resina. Los resultados indican que al aumentar [(NH4)2S2O3] favorece la adsorción en un 99% durante tres horas, siendo afectado notablemente por la presencia de amonio. Las condiciones con mejores resultados en la columna a 25°C fueron, pH= 10.5 y [Au] =1 mg/l. The adsorption and elution of gold in thiosulfate-ammonia media were studied using the resin AuRIX 100, evaluating some variables that affect the kinetico of the process, such as: temperature, stirring speed, pH, thiosulfate concentration (NH4)2S2O3 and gold concentration. The study was carried out in a batch reactor and an ion exchange column. The operation conditions that presented better results of gold extraction at 25°C were: pH=10.5, stirring opeed=500 rpm, [Au]=1 mg/l, [(NH4)2S2O3]=0.04 M, and 5 gramo of resin. The results indicate that by increasing [(NH4)2S2O3] favors the adsorption by 99% during three hours, being noticeably affected by the presence of ammonia. The conditions with results on the column at 25°C were, pH= 10.5, [Au]=1 mg/l.
Democracia caudillista y desmovilizaciones sociales en Ecuador
Sánchez Parga,José;
Polis (Santiago) , 2009, DOI: 10.4067/S0718-65682009000300009
Abstract: the conflicts and vindications of the social movements, with politically representation, during the democratic transition of the 80?s, enter crisis with the model of accumulation and concentration of wealth, inaugurated by the neoliberal domination during the 90?s, giving rise to the cycle to the protest mobilizations, that aggravate the crisis of all the system of political representation (elections, parties, congress), which degenerates in a new phenomenon: the political representativism. the imperative of ?governability? of the protest, the accumulation and concentration of executive power, for a better economic government of politics, reinforced the powers of hiperpresidencialism and the formation of a ?caudillista? democracy, that in ecuador adopted a counter-neoliberal orientation.
Democracia caudillista y desmovilizaciones sociales en Ecuador
José Sánchez Parga
Polis : Revista de la Universidad Bolivariana , 2009,
Abstract: Los conflictos y reivindicaciones de los movimientos sociales, políticamente representables, durante la transición democrática de los 80, entran en crisis con el modelo de acumulación y concentración de riqueza, inaugurado por la dominación neoliberal durante los 90, dando lugar al ciclo de movilizaciones de protesta, que agravan la crisis de todo el sistema de representación política (elecciones, partidos, congreso), el que degenera en un fenómeno nuevo: el representativismo político. El imperativo de "gobernabilidad" de la protesta, la acumulación y concentración de poderes ejecutivos, para un mejor gobierno económico de la política, reforzaron los poderes del hiperpresidencialismo y la formación de una democracia caudillista, que en Ecuador adoptó una orientación contra-neoliberal.
La democracia caudillista en el Ecuador
José Sánchez Parga
Araucaria , 2009,
Abstract: Los gobiernos y políticas neoliberales de los a os 80 y 90 tuvieron como efecto una desconsolidación de la democracia, desarmando las reivindicaciones de los movimientos sociales y reduciéndolos a movilizaciones de protesta o a su politización, devastando el sistema de la representación política (sistema electoral, partidario y parlamentario) y dando lugar a un representativismo político. Tras el derrocamiento de tres sucesivos Presidentes se conf gura una democracia caudillista caracterizada por un fuerte presidencialismo, un gobierno contra-neoliberal y unas políticas sociales redistribucionistas.
Page 1 /286858
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.