Jesús L. Valenzuela

Thermodynamic studies of the strontium adsorption on iron species generated by electrocoagulation

Abstract In this research we present and discuss the results of the use of the Electrocoagulation (EC) process for strontium removal from wastewater. The phenomena associated with strontium removal is adsorption on iron magnetic species generated from the dissolution of iron electrodes of the electrolytic cell. With the EC process more than 99 percent of strontium was removed from wastewater without addition of chemical reagents. Sludge generated by EC was characterized by Chemical Analyses, X-Ray Diffraction, Scanning Electron Microscopy and Vibrating Sample Magnetometer (VSM) in order to document the adsorption of strontium on iron-species. The electrogenerated crystalline iron oxides magnetite (Fe3O4) and maghemite (γ-Fe2O3) powders have higher values for saturation magnetization, but lower values for remanent magnetization and coercive fi eld than commercial strontium hexaferrite with micrometric particle size. The experimental data were correlated employing a Langmuir adsorption isotherm. Thermodynam...

New Technology for Recovery of Gold and Silver by Pressure Cyanidation Leaching and Electrocoagulation

The present chapter describes a new technology of pressure oxidation/cyanidation leaching for the dissolution of gold and silver and the recovery of the precious metals by using the electrochemical process of Electrocoagulation (EC). The novel method demonstrates that the oxidation and dissolution of gold and silver in alkaline cyanide solution can be conducted simultaneously in the same reactor in less than 90 minutes with a recovery that exceeds 96%. Then, the pregnant cyanide solution with gold and silver is sent for recovery of precious metals by using a very promising electrochemical technique (EC) that does not require high concentrations of silver and gold in cyanide solutions.

Recovery of Silver and Gold from Cyanide Solution by Magnetic Species Formed in the Electrocoagulation Process

Cyanidation is the predominant process by which gold and silver are recovered from their ores in metallurgical operations, and it is recognized that the Carbon in Pulp, the Merrill–Crowe, the Ion Exchange, and Solvent Extraction processes are 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 water and wastewater electrochemical technique that does not require high concentrations of silver and gold in cyanide solutions to yield excellent results. In this work, an introduction to the fundamentals of the EC process is given, followed by the conditions and results of the EC test run for removal of precious metals from cyanide solutions, and finally the characterization of the solid products formed during the EC process with X-ray Diffraction, SEM, and Transmission Mossbauer Spectroscopy. Results suggest that magnetite particles and amorphous iron oxyhydroxides are present (Lepidocrocite and Gohetite). With the EC process, the achieved removal efficiency of silver and gold from cyanide solutions, within 5 min, exceeded 99%.

Uso de Resina de Intercambio Aniónico para la Recuperación del Complejo Oro Tiosulfato desde Soluciones Acuosas

Resumen Se estudio la adsorcion de oro utilizando la resina AuRIX ® 100 en medio tiosulfato de amonio, evaluando algunas variables que afectan la cinetica del proceso tales como: temperatura, velocidad de agitacion, pH, concentracion de tiosulfato de amonio (NH 4 ) 2 S 2 O 3 y concentracion de oro. El estudio se llevo a cabo en un reactor batch y una columna de intercambio ionico. Las condiciones de operacion que presentaron mejores resultados de extraccion de oro a 25oC, fueron: pH=10.5, velocidad de agitacion=500 rpm, [Au]=1 mg/l, [(NH 4 ) 2 S 2 O 3 ]=0.04 M, 5 gramos de resina. Los resultados indican que al aumentar [(NH 4 ) 2 S 2 O 3 ] favorece la adsorcion en un 99% durante tres horas, siendo afectado notablemente por la presencia de amonio. Las condiciones con mejores resultados en la columna a 25oC fueron, pH= 10.5 y [Au] =1 mg/l. Palabras clave: adsorcion oro, tiosulfato, resina AuRIX ® 100, cinetica Use of Anion Exchange Resin for the Recovery of the Complex Gold Thiosulfate from Aqueous Solutions

Cyanide and Copper Recovery from Barren Solution of the Merrill Crowe Process

This paper is a brief overview of the role of inducing the nucleated precipitation of copper and cyanide in a flashtube serpentine reactor, using sodium sulfide as the precipitate and sulfuric acid as pH control. The results showed that pH had a great effect on copper cyanide removal efficiency and the optimum pH was about 3 to 3.5. At this pH value copper cyanide removal efficiency could be achieved above 97 and 99 %, when influent copper concentration ions were 650 and 900 ppm respectively. In this process the cyanide associated with the copper, zinc, iron cyanide complexes are released as HCN gas under strong acidic conditions, allowing it to be recycled back to the cyanidation process as free cyanide.