Hypochlorite Leaching of Gold Ore
The reactions between gold and hypochlorite leach solutions containing hydrochloric acid and sodium chloride are demonstrated below: 4Au + 16NaOCl + 10H2O → 4HAuCl4 + 16NaOH + 5O2……………………………………(1) 4HAuCl4 + 4NaCl → 4NaAuCl4 + 4HCl…………………………………………(2) 16NaOH + 16HCl → 16NaCl + 16H2O…………………………………………(3) Overall reaction of equations (1), (2) and (3) can be summarized as follows: 4Au + 16NaOCl […]
Leach & Recover Gold from Black Sands
Black sand may be generally defined as a constituent of “alluvial” gravel consisting mainly of fine particulate grains of heavy, dark colored minerals and rocks. These alluvial gravels, chiefly concentrated by wave, current or surface action, may also contain “eluvial” material that includes black sand. The eluvium, which results from decomposition or disintegration in place […]
Supercritical Water Treatment of Refractory Gold Ores
Supercritical water alters the structure of common sulfide minerals by partially removing sulfur from the mineral structure. This discovery has been applied to the treatment of pyritic gold ores to improve precious metal recovery without generating or utilizing environmentally sensitive products such as SO2, chlorine, or cyanide. Pretreating pyrite concentrates in supercritical water under mildly […]
Underground Leaching & Hydrology
Underground in situ leaching is a method of in situ leaching which takes advantage of existing underground mine workings to gain preferential access to a deeply buried ore deposit. With this method of leaching, injection and recovery wells are collared in existing underground mine drifts and drilled into an undisturbed portion of the deposit. The […]
Bioleaching Refractory Gold Ore
Bacterial extraction of gold from sulfide bearing ores has been studied by many investigators. If gold occurs finely disseminated within the sulfide ore matrix such as in pyrite, arsenopyrite and pyrrhotite, the leachant can not penetrate into the inside of solid ore in order to leach the enclosed submicron size gold particles. For their liberation, […]
Gallium Solvent Extraction
Recently, details of a study optimizing gallium and germanium extraction from zinc residues using H2SO4 leaches was published. In the process, filtrates containing gallium and germanium along with other impurities such as iron, copper, zinc, and cadmium are produced. The focus of this paper is the recovery of gallium from these solutions. It has been […]
Iodine Gold Leaching
Over the last few years there has been an intense effort to identify lixiviants other than cyanide for gold and silver leaching. Bromide and iodide also exhibit the ability to form polyhalide complexes. This characteristic promotes the dissolution of Br2(s) and I(2)s in aqueous solution. Iodine reacts with iodide ion as follows: I(2)s = I2(aq)………………………………………………………..(1) I2(aq)+ […]
Leaching Fluorine from Copper Concentrate
Hydrometallurgical Removal of Fluorine from Copper Concentrates: CVRD Technology Center (SUTEC) has developed and patented an hydrometallurgical process route to remove fluorine from copper concentrates, as a result of an extensive testwork to investigate the effect of mineral acids on fluorite solubilization. The process developed consists of leaching the high fluorine copper concentrates with H2SO4 or […]
Pressure Leaching of Galena to Recover Lead by Electrowinning
As part of the U.S. Bureau of Mines program to improve base metal leach systems, pressure leaching of galena (PbS) concentrates in fluosilicic acid (H2SiF6) solution was investigated. Lead extraction was 93 pct when PbS was pressure leached in H2SiF6 at 95° C with 200-psig O2 pressure for 40 min, using ferric nitrate [Fe(NO3)3] as […]
Sulfide Ore Treatment Gold – Silver – Copper – Cobalt – Zinc Recovery
A procedure was developed for recovering gold, silver, cobalt, copper, and zinc from a massive sulfide ore by a hydro-metallurgical process. The procedure consists of (1) oxygen pressure leaching; (2) iron, arsenic, and copper removal from the leach solution by precipitation; (3) selective extraction of cobalt and zinc from solution; (4) electro-deposition of the cobalt […]