Jesus Leobardo Valenzuela - Academia.edu (original) (raw)

Papers by Jesus Leobardo Valenzuela

Proceedings of the 3rd …, 2007

Mining, metallurgy & exploration, Jan 23, 2022

Minerals

Most gold deposits occur associated with sulphides like pyrite and arsenopyrite; thus, precious m... more Most gold deposits occur associated with sulphides like pyrite and arsenopyrite; thus, precious metal dissolution is possible by oxidizing auriferous sulfide concentrate using simultaneous pressure oxidation and cyanidation. The effectiveness of this process of extraction can be influenced by the temperature, cyanide (NaCN) concentration, and oxygen pressure. In this study, we conducted experiments to characterize the effects on gold extraction of ores using a range of sodium cyanide concentrations (1–8 g/L), temperatures (40–75 °C), and oxygen pressures (0.5–1.1 MPa). Characterization of the ores showed that pyrite and quartz were the main minerals present in the concentrate. The best results in terms of the highest extraction of Au were obtained with an oxygen pressure of 0.5 MPa, 6 g/L sodium cyanide, and a temperature of 75 °C, along with a constant stirring speed of 600 rpm. These conditions allowed for approximately 95% gold extraction in 90 min.

Gold adsorption was studied with (NH4)2S2O3, using NH4OH as pH regulator, in an ion exchange resi... more Gold adsorption was studied with (NH4)2S2O3, using NH4OH as pH regulator, in an ion exchange resin AuRIX ® 100, evaluating the adsorption stage, the experiments were carried out in a batch tests and ion exchange column. It was found NH4OH, maximizes the adsorption of gold at pH 10.5 and the presence of thiosulfate, it is favorable for the adsorption of the gold to 99%. In column tests the adsorption is achieved to a 75% of gold. In the model of adsorption the experimental data were adjusted to the Freundlich isotherm. The AuRIX ® 100 resin is efficient; it has a higher capacity and fast kinetic and the results of experiments at room temperature favor the kinetic adsorption process. Keywords— Adsorption, Anion Exchange Resin, Gold, Thiosulfate

Metals, 2019

This article presents a copper leaching process from chalcopyrite concentrates using a low-pressu... more This article presents a copper leaching process from chalcopyrite concentrates using a low-pressure reactor. The experiments were carried out in a 30 L batch reactor at an oxygen pressure of 1 kg/cm2 and solid concentration of 100 g/L. The temperature, particle size and initial acid concentration were varied based on a Taguchi L9 experimental design. The initial and final samples of the study were characterized by chemical analysis, X-ray diffraction and particle size distribution. The mass balance showed that 98% of copper was extracted from the chalcopyrite concentrate in 3 h under the following experimental conditions: 130 g/L of initial sulfuric acid concentration, temperature of 100 °C, oxygen pressure of 1 kg/cm2, solid concentration of 100 g/L and particle size of −105 + 75 μm. The ANOVA demonstrated that temperature had the greatest influence on copper extraction. The activation energy was 61.93 kJ/mol. The best fit to a linear correlation was the chemical reaction equation ...

Materials Sciences and Applications, 2015

The Merrill-Crowe zinc-precipitation process has been applied worldwide on a large number of oper... more 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.

Advances in Chemical Engineering and Science, 2013

This paper is a brief overview of the role of inducing the nucleated electro winning of copper by... more 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•l −1 to below 10 mg•l −1 within 20 minutes.

Advances in Chemical Engineering and Science, 2013

The majority of the refractory gold and silver occurs in occlusion in sulphides, then precious me... more 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 2 4 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˚C, 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.

Recycling, 2021

Reclamation of printed circuit boards (PCBs) to recover metals is gaining growing attention due t... more Reclamation of printed circuit boards (PCBs) to recover metals is gaining growing attention due to minerals being non-renewable resources. Currently, metals extraction from PCBs through an efficient and green method is still under investigation. The present investigation concerns the recycling of printed circuit boards using hydrometallurgical processes. First, the basic metals (Cu, Ni, Zn and Fe) were separated using a sulfuric acid solution at moderate temperatures. The remaining solids were characterized by SEM-EDS, whereby a high content of precious metals (Au, Ag and Pt) was observed. In the second stage, solids were leached with a solution of HCl and NaClO in a 1-L titanium reactor with varied oxygen pressure (0.2, 0.34 and 0.55 MPa), temperature (40, 50 and 80 °C) and concentration of HCl (2 and 4 M), obtaining extractions above 95% at [HCl] = 4 M, P = 0.34 MPa and T = 40 °C. The extraction increased depending on the concentration of HCl. Eh–pH diagrams for Ag–Cl–H2O, Au–Cl–H...

Materials Sciences and Applications, 2014

The conventional processes for recovery of silver from cyanide leach solutions are the carbon ads... more The conventional processes for recovery of silver from cyanide leach solutions are the carbon adsorption, the Merrill-Crowe zinc dust cementation, the Ion Exchange, and Solvent Extraction processes; among other available options for recovery of precious metals from cyanide solutions, Electrocoagulation (EC) is a very promising electrochemical process that does not require high concentrations of silver in cyanide solutions to yield excellent results and neither pretreatment of cyanide solutions like Merrill-Crowe process (deoxygenating and clarification). The present study has been done for the recovery of silver contained in pregnant solution from the cyanidation process using the electrocoagulation technology with iron electrodes, and therefore develops an alternative technology for Merril-Crowe process. The average silver content in pregnant solution was of 52 ppm, recovery was obtained of 99% of silver, with this optimum operating parameters, pH = 8, residence time = 20 minutes and conductivity by addition of sodium chloride = 4 grs/L. Finally the characterization of the solid products formed during the EC process with X-ray Diffraction and Scanning Electronic Microscope was performed, results suggest that magnetite particles and amorphous iron oxyhydroxides are present (Lepidocrocite).

Materials Sciences and Applications, 2015

Over the past decade the concern about toxic metals in freshwater has increased. Environmental la... more Over the past decade the concern about toxic metals in freshwater has increased. Environmental laws such as the Clean Water Act have forced industries that produce metal containing wastewater to treat their wastewater prior to discharge. The purpose of this study was to investigate the use of a novel method for the minimization of heavy metals in the wastewater from the mining industry. A very promising electrochemical treatment technique that does not require chemical additions is electrocoagulation (EC) and sulphide precipitation. The present study has been done for the recovery of gold and silver contained in pregnant solution from the cyanidation process using the electrocoagulation technology with iron electrodes; that is a developed alternative technology for the Merril-Crowe process. The average gold and silver content in pregnant solution was 4.27 and 283 ppm respectively and the recoveries were 92% for gold and 95% for silver, with optimum operating parameters of pH 10, residence time of 20 minutes and addition of sodium chloride of 4 gr/L. The results of precipitation process show that the elimination of lead, zinc, cooper and iron ions from the barren solution was successful, with optimum operating parameters of pH 3 and residence time of 15 minutes, and the recoveries were 99% of these ions. Finally the characterization of the solid products of gold and silver formed during the EC process with Scanning Electronic Microscope was performed. Results suggest that magnetite particles and amorphous iron oxyhydroxides (lepidocrocite) were present.

Cyanide consumption can be a major factor which contributes to operating cost for cyanidation. Al... more Cyanide consumption can be a major factor which contributes to operating cost for cyanidation. Also after extraction and recovery of precious metals substancial amounts of cyanide are delivered to tailings ponds which creates environmental problems due to the toxicity of cyanides. In this regard, the air-sparged hydrocyclone (ASH) has been used as a reactor for the treatment of cyanide solutions in two ways; first for cyanide recovery by acidulation using the Mexican modification of the Merrill-Crowe process and second for cyanide destruction by oxidation with the use of chlorine dioxide (C10 2). In both cases excellent performance can be archieved using the high capacity ASH technology.

Advances in Chemical Engineering and Science, 2011

Cyanidation is the main process for gold and silver recovery from its ores. In this study, a proc... more 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.

Chemical Speciation and Bioavailability, 2012

The extraction of gold and silver from minerals and concentrates with cyanide is an important hyd... more The extraction of gold and silver from minerals and concentrates with cyanide is an important hydrometallurgy process that has been studied for more than 120 years. This technology, which consists of the dissolutions of the precious metals in cyanide solutions, followed by the recovery of the values by cementation, activated carbon or ion exchange resin. Most of the wastes in the industrial effluents' milling are known to contain high contents of free cyanide as well as metallic cyanide complexes, which give them a high degree of toxicity. Appropriate methods for the treatment of cyanide solutions include cyanide destruction by oxidation using a photoelectrocatalytic detoxification technique with titanium dioxide microelectrodes. This is one of the most innovative ways for the treatment of wastewater containing cyanide. Another is the use of chlorine dioxide (ClO 2) with a gas-sparged hydrocyclone as the reactor. The results show that photodegradation of cyanide was 93% in 30 minutes using a 450 W halogen lamp, and in the case of ClO 2, the destruction of cyanides was 99% in 1 minute. In both cases, excellent performances can be achieved with the high capacity of these technologies.

Revista de Metalurgia, 2012

En el procesamiento de minerales de metales preciosos con altos contenidos de pirita, se obtienen... more En el procesamiento de minerales de metales preciosos con altos contenidos de pirita, se obtienen concentrados refractarios difíciles de procesar. En este estudio se lixivió un concentrado refractario de oro y plata con cianuro de sodio, obteniéndose extracciones de 34 % para oro y 40 % para plata. Se utilizó el método de tostación para oxidar el concentrado, haciéndolo más susceptible a la cianuración, y extraer más eficientemente el oro y la plata. Las variables analizadas fueron: temperatura de tostación y tiempos de tostación y cianuración. Además, la calcina caliente se agregó a la solución lixiviante a temperatura ambiente para analizar el efecto en el tamaño de partícula y recuperación. Los mejores resultados, aunque no del todo satisfactorios (50 % oro y 61 % plata), se obtuvieron mediante tostación del concentrado durante 4 h a temperaturas de 600 °C, seguido de una cianuración de 20 h. El consumo de cal para elevar el pH a 11,3, se incrementó notablemente hasta 25 kg/m³.

Advances in Chemical Engineering and Science, 2014

Insert Industrial treatment of mineral-processing and non-ferrous metal-smelting acid wastewater ... more Insert Industrial treatment of mineral-processing and non-ferrous metal-smelting acid wastewater effluents is becoming an enormous worldwide problem. In Mexico, heavy metalscontaminated natural waters, including freshwater, surface water and ground water, are a significant problem as some of these compounds are known as toxic, mutagenic, and carcinogenic. A very promising electrochemical treatment technique that does not require chemical additions to remove arsenic is electrocoagulation (EC) with air injection. The proposed electrochemical process is efficient because used low cost iron electrodes and promising in industrial application. Theoretical the purpose of this research was to investigate the thermodynamic of arsenic adsorption on iron species using the Langmuir's Isotherm. Also, thermodynamic parameters such as ∆H  , ∆S  and ∆G  were calculated and the adsorption process was found to be exothermic and spontaneous. X-ray Diffraction and Scanning Electron Microscopy, were used to characterize the solid products formed during EC. The results of this study suggest that magnetite particles and amorphous iron oxyhydroxides are present in the examined EC products and this study indicate that arsenic can be successfully adsorbed on iron species by electrocoagulation process. Field pilot-scale study demonstrated the removal of As(III)/As(V) with an efficiency of more than 99% from both wastewater and wells.

International Journal of Nonferrous Metallurgy, 2013

Conventional methods for precious metals gravimetric concentration involve equipment such as shak... more Conventional methods for precious metals gravimetric concentration involve equipment such as shaking tables, centrifuging concentrators, jigs, trommels, or a combination of those. A less commonly used technique is elutriation, which represents an efficient, safe and low-cost method of separation. The goal of the present investigation was to make a comparative study of gold concentration by elutriation from different precious metal bearing ores: an oxide ore, a mineral consisting of a sulfide matrix, a mineral in which the precious metals are free and disseminated and a slimy and clayey black sand material. The best recoveries of precious metals by elutriation were attained for the free disseminated ore and for the black sands, obtaining gold recoveries of 70% and 96% respectively, with appreciable ratios of concentration as well.

Chemical Speciation and Bioavailability, 2009

The main objective of this work was to study the capacity of bioaccumulation of copper in an upfl... more The main objective of this work was to study the capacity of bioaccumulation of copper in an upflow anaerobic sludge blanket (UASB) reactor, for the treatment of acid mine drainages (AMD). UASB reactor of 0.8 L was fed with sodium acetate, the organic loading rate (OLR) was set at 2.0 gCODyL d, and experiments were performed in the reactor during 115 days. After 30 days, the COD removal efficiency was 90%. In the stationary stage, the higher production methane was 0.253 LyL d. The reactor was added with 20 mgCu(II)yL during 30 days. The copper bioaccumulation was 98% and it was accumulated gradually in sludge until reaching a 61.6 mgCu(II)ygTS. The toxicity study demonstrated that the copper concentration at which the level of specific methanogenic activity (SMA) of the biogranules was reduced to 50% of the control (IC 50), was 280 mgCu(II)yL.

Chemical Speciation and Bioavailability, 2008

... c*, Jesuī s L. Valenzuela-Garcıaa, Evelia Acedo-Feī lixb, Marıa Teresa Certucha-Barragaī na, ... more ... c*, Jesuī s L. Valenzuela-Garcıaa, Evelia Acedo-Feī lixb, Marıa Teresa Certucha-Barragaī na, Michael Schoor-Wienerc and ... The San Pedro River basin is located to the north of the state of Sonora, Mexico ... 2003) carried out biosorption experiments on heavy metals (Pb, Cd and Cr ...

Proceedings of the 3rd …, 2007

Mining, metallurgy & exploration, Jan 23, 2022

Minerals

Most gold deposits occur associated with sulphides like pyrite and arsenopyrite; thus, precious m... more Most gold deposits occur associated with sulphides like pyrite and arsenopyrite; thus, precious metal dissolution is possible by oxidizing auriferous sulfide concentrate using simultaneous pressure oxidation and cyanidation. The effectiveness of this process of extraction can be influenced by the temperature, cyanide (NaCN) concentration, and oxygen pressure. In this study, we conducted experiments to characterize the effects on gold extraction of ores using a range of sodium cyanide concentrations (1–8 g/L), temperatures (40–75 °C), and oxygen pressures (0.5–1.1 MPa). Characterization of the ores showed that pyrite and quartz were the main minerals present in the concentrate. The best results in terms of the highest extraction of Au were obtained with an oxygen pressure of 0.5 MPa, 6 g/L sodium cyanide, and a temperature of 75 °C, along with a constant stirring speed of 600 rpm. These conditions allowed for approximately 95% gold extraction in 90 min.

Gold adsorption was studied with (NH4)2S2O3, using NH4OH as pH regulator, in an ion exchange resi... more Gold adsorption was studied with (NH4)2S2O3, using NH4OH as pH regulator, in an ion exchange resin AuRIX ® 100, evaluating the adsorption stage, the experiments were carried out in a batch tests and ion exchange column. It was found NH4OH, maximizes the adsorption of gold at pH 10.5 and the presence of thiosulfate, it is favorable for the adsorption of the gold to 99%. In column tests the adsorption is achieved to a 75% of gold. In the model of adsorption the experimental data were adjusted to the Freundlich isotherm. The AuRIX ® 100 resin is efficient; it has a higher capacity and fast kinetic and the results of experiments at room temperature favor the kinetic adsorption process. Keywords— Adsorption, Anion Exchange Resin, Gold, Thiosulfate

Metals, 2019

This article presents a copper leaching process from chalcopyrite concentrates using a low-pressu... more This article presents a copper leaching process from chalcopyrite concentrates using a low-pressure reactor. The experiments were carried out in a 30 L batch reactor at an oxygen pressure of 1 kg/cm2 and solid concentration of 100 g/L. The temperature, particle size and initial acid concentration were varied based on a Taguchi L9 experimental design. The initial and final samples of the study were characterized by chemical analysis, X-ray diffraction and particle size distribution. The mass balance showed that 98% of copper was extracted from the chalcopyrite concentrate in 3 h under the following experimental conditions: 130 g/L of initial sulfuric acid concentration, temperature of 100 °C, oxygen pressure of 1 kg/cm2, solid concentration of 100 g/L and particle size of −105 + 75 μm. The ANOVA demonstrated that temperature had the greatest influence on copper extraction. The activation energy was 61.93 kJ/mol. The best fit to a linear correlation was the chemical reaction equation ...

Materials Sciences and Applications, 2015

The Merrill-Crowe zinc-precipitation process has been applied worldwide on a large number of oper... more 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.

Advances in Chemical Engineering and Science, 2013

This paper is a brief overview of the role of inducing the nucleated electro winning of copper by... more 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•l −1 to below 10 mg•l −1 within 20 minutes.

Advances in Chemical Engineering and Science, 2013

The majority of the refractory gold and silver occurs in occlusion in sulphides, then precious me... more 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 2 4 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˚C, 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.

Recycling, 2021

Reclamation of printed circuit boards (PCBs) to recover metals is gaining growing attention due t... more Reclamation of printed circuit boards (PCBs) to recover metals is gaining growing attention due to minerals being non-renewable resources. Currently, metals extraction from PCBs through an efficient and green method is still under investigation. The present investigation concerns the recycling of printed circuit boards using hydrometallurgical processes. First, the basic metals (Cu, Ni, Zn and Fe) were separated using a sulfuric acid solution at moderate temperatures. The remaining solids were characterized by SEM-EDS, whereby a high content of precious metals (Au, Ag and Pt) was observed. In the second stage, solids were leached with a solution of HCl and NaClO in a 1-L titanium reactor with varied oxygen pressure (0.2, 0.34 and 0.55 MPa), temperature (40, 50 and 80 °C) and concentration of HCl (2 and 4 M), obtaining extractions above 95% at [HCl] = 4 M, P = 0.34 MPa and T = 40 °C. The extraction increased depending on the concentration of HCl. Eh–pH diagrams for Ag–Cl–H2O, Au–Cl–H...

Materials Sciences and Applications, 2014

The conventional processes for recovery of silver from cyanide leach solutions are the carbon ads... more The conventional processes for recovery of silver from cyanide leach solutions are the carbon adsorption, the Merrill-Crowe zinc dust cementation, the Ion Exchange, and Solvent Extraction processes; among other available options for recovery of precious metals from cyanide solutions, Electrocoagulation (EC) is a very promising electrochemical process that does not require high concentrations of silver in cyanide solutions to yield excellent results and neither pretreatment of cyanide solutions like Merrill-Crowe process (deoxygenating and clarification). The present study has been done for the recovery of silver contained in pregnant solution from the cyanidation process using the electrocoagulation technology with iron electrodes, and therefore develops an alternative technology for Merril-Crowe process. The average silver content in pregnant solution was of 52 ppm, recovery was obtained of 99% of silver, with this optimum operating parameters, pH = 8, residence time = 20 minutes and conductivity by addition of sodium chloride = 4 grs/L. Finally the characterization of the solid products formed during the EC process with X-ray Diffraction and Scanning Electronic Microscope was performed, results suggest that magnetite particles and amorphous iron oxyhydroxides are present (Lepidocrocite).

Materials Sciences and Applications, 2015

Over the past decade the concern about toxic metals in freshwater has increased. Environmental la... more Over the past decade the concern about toxic metals in freshwater has increased. Environmental laws such as the Clean Water Act have forced industries that produce metal containing wastewater to treat their wastewater prior to discharge. The purpose of this study was to investigate the use of a novel method for the minimization of heavy metals in the wastewater from the mining industry. A very promising electrochemical treatment technique that does not require chemical additions is electrocoagulation (EC) and sulphide precipitation. The present study has been done for the recovery of gold and silver contained in pregnant solution from the cyanidation process using the electrocoagulation technology with iron electrodes; that is a developed alternative technology for the Merril-Crowe process. The average gold and silver content in pregnant solution was 4.27 and 283 ppm respectively and the recoveries were 92% for gold and 95% for silver, with optimum operating parameters of pH 10, residence time of 20 minutes and addition of sodium chloride of 4 gr/L. The results of precipitation process show that the elimination of lead, zinc, cooper and iron ions from the barren solution was successful, with optimum operating parameters of pH 3 and residence time of 15 minutes, and the recoveries were 99% of these ions. Finally the characterization of the solid products of gold and silver formed during the EC process with Scanning Electronic Microscope was performed. Results suggest that magnetite particles and amorphous iron oxyhydroxides (lepidocrocite) were present.

Cyanide consumption can be a major factor which contributes to operating cost for cyanidation. Al... more Cyanide consumption can be a major factor which contributes to operating cost for cyanidation. Also after extraction and recovery of precious metals substancial amounts of cyanide are delivered to tailings ponds which creates environmental problems due to the toxicity of cyanides. In this regard, the air-sparged hydrocyclone (ASH) has been used as a reactor for the treatment of cyanide solutions in two ways; first for cyanide recovery by acidulation using the Mexican modification of the Merrill-Crowe process and second for cyanide destruction by oxidation with the use of chlorine dioxide (C10 2). In both cases excellent performance can be archieved using the high capacity ASH technology.

Advances in Chemical Engineering and Science, 2011

Cyanidation is the main process for gold and silver recovery from its ores. In this study, a proc... more 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.

Chemical Speciation and Bioavailability, 2012

The extraction of gold and silver from minerals and concentrates with cyanide is an important hyd... more The extraction of gold and silver from minerals and concentrates with cyanide is an important hydrometallurgy process that has been studied for more than 120 years. This technology, which consists of the dissolutions of the precious metals in cyanide solutions, followed by the recovery of the values by cementation, activated carbon or ion exchange resin. Most of the wastes in the industrial effluents' milling are known to contain high contents of free cyanide as well as metallic cyanide complexes, which give them a high degree of toxicity. Appropriate methods for the treatment of cyanide solutions include cyanide destruction by oxidation using a photoelectrocatalytic detoxification technique with titanium dioxide microelectrodes. This is one of the most innovative ways for the treatment of wastewater containing cyanide. Another is the use of chlorine dioxide (ClO 2) with a gas-sparged hydrocyclone as the reactor. The results show that photodegradation of cyanide was 93% in 30 minutes using a 450 W halogen lamp, and in the case of ClO 2, the destruction of cyanides was 99% in 1 minute. In both cases, excellent performances can be achieved with the high capacity of these technologies.

Revista de Metalurgia, 2012

En el procesamiento de minerales de metales preciosos con altos contenidos de pirita, se obtienen... more En el procesamiento de minerales de metales preciosos con altos contenidos de pirita, se obtienen concentrados refractarios difíciles de procesar. En este estudio se lixivió un concentrado refractario de oro y plata con cianuro de sodio, obteniéndose extracciones de 34 % para oro y 40 % para plata. Se utilizó el método de tostación para oxidar el concentrado, haciéndolo más susceptible a la cianuración, y extraer más eficientemente el oro y la plata. Las variables analizadas fueron: temperatura de tostación y tiempos de tostación y cianuración. Además, la calcina caliente se agregó a la solución lixiviante a temperatura ambiente para analizar el efecto en el tamaño de partícula y recuperación. Los mejores resultados, aunque no del todo satisfactorios (50 % oro y 61 % plata), se obtuvieron mediante tostación del concentrado durante 4 h a temperaturas de 600 °C, seguido de una cianuración de 20 h. El consumo de cal para elevar el pH a 11,3, se incrementó notablemente hasta 25 kg/m³.

Advances in Chemical Engineering and Science, 2014

Insert Industrial treatment of mineral-processing and non-ferrous metal-smelting acid wastewater ... more Insert Industrial treatment of mineral-processing and non-ferrous metal-smelting acid wastewater effluents is becoming an enormous worldwide problem. In Mexico, heavy metalscontaminated natural waters, including freshwater, surface water and ground water, are a significant problem as some of these compounds are known as toxic, mutagenic, and carcinogenic. A very promising electrochemical treatment technique that does not require chemical additions to remove arsenic is electrocoagulation (EC) with air injection. The proposed electrochemical process is efficient because used low cost iron electrodes and promising in industrial application. Theoretical the purpose of this research was to investigate the thermodynamic of arsenic adsorption on iron species using the Langmuir's Isotherm. Also, thermodynamic parameters such as ∆H  , ∆S  and ∆G  were calculated and the adsorption process was found to be exothermic and spontaneous. X-ray Diffraction and Scanning Electron Microscopy, were used to characterize the solid products formed during EC. The results of this study suggest that magnetite particles and amorphous iron oxyhydroxides are present in the examined EC products and this study indicate that arsenic can be successfully adsorbed on iron species by electrocoagulation process. Field pilot-scale study demonstrated the removal of As(III)/As(V) with an efficiency of more than 99% from both wastewater and wells.

International Journal of Nonferrous Metallurgy, 2013

Conventional methods for precious metals gravimetric concentration involve equipment such as shak... more Conventional methods for precious metals gravimetric concentration involve equipment such as shaking tables, centrifuging concentrators, jigs, trommels, or a combination of those. A less commonly used technique is elutriation, which represents an efficient, safe and low-cost method of separation. The goal of the present investigation was to make a comparative study of gold concentration by elutriation from different precious metal bearing ores: an oxide ore, a mineral consisting of a sulfide matrix, a mineral in which the precious metals are free and disseminated and a slimy and clayey black sand material. The best recoveries of precious metals by elutriation were attained for the free disseminated ore and for the black sands, obtaining gold recoveries of 70% and 96% respectively, with appreciable ratios of concentration as well.

Chemical Speciation and Bioavailability, 2009

The main objective of this work was to study the capacity of bioaccumulation of copper in an upfl... more The main objective of this work was to study the capacity of bioaccumulation of copper in an upflow anaerobic sludge blanket (UASB) reactor, for the treatment of acid mine drainages (AMD). UASB reactor of 0.8 L was fed with sodium acetate, the organic loading rate (OLR) was set at 2.0 gCODyL d, and experiments were performed in the reactor during 115 days. After 30 days, the COD removal efficiency was 90%. In the stationary stage, the higher production methane was 0.253 LyL d. The reactor was added with 20 mgCu(II)yL during 30 days. The copper bioaccumulation was 98% and it was accumulated gradually in sludge until reaching a 61.6 mgCu(II)ygTS. The toxicity study demonstrated that the copper concentration at which the level of specific methanogenic activity (SMA) of the biogranules was reduced to 50% of the control (IC 50), was 280 mgCu(II)yL.

Chemical Speciation and Bioavailability, 2008

... c*, Jesuī s L. Valenzuela-Garcıaa, Evelia Acedo-Feī lixb, Marıa Teresa Certucha-Barragaī na, ... more ... c*, Jesuī s L. Valenzuela-Garcıaa, Evelia Acedo-Feī lixb, Marıa Teresa Certucha-Barragaī na, Michael Schoor-Wienerc and ... The San Pedro River basin is located to the north of the state of Sonora, Mexico ... 2003) carried out biosorption experiments on heavy metals (Pb, Cd and Cr ...