Tungsten & Gold Recovery Scheelite Ores
Investigations were conducted by the U.S. Bureau of Mines to develop flowsheets for the recovery of tungsten and gold from four Alaskan scheelite-bearing ores. Basic gravity concentration and cyanide leach tests were performed on all samples. About 46 pct of the tungsten and 30 pct of the gold from one sample were recovered in a […]
Recycle Superalloy Scrap Metals
We treated mixed and contaminated superalloy scrap by pyrometallurgical and hydrometallurgical methods to separate and recover metal values. Best results were obtained by leaching Zn-treated or atomized scrap with HCl-O2 at 95° C and 50 psig O2. This resulted in dissolving approximately 98% of the Al, Co, Cr, Cu, Fe, Mn, Ni, and Zn while […]
Effect of Impurities on Gold Adsorption on Activated Carbon
We performed batch equilibrium contact experiments to examine the ability of activated coconut-shell carbon to adsorb various metal cyanide complexes. Tests were also conducted to determine the effect these cyanide complex impurities might have on the adsorption of gold by the activated carbon. Metal cyanide species included in the investigation were antimony, arsenic, cadmium, calcium, […]
In-Situ Leach Mining Design for Copper
Objective Provide the U.S. mining industry with technology for designing environmentally sound, low- cost in situ leach mining operations to produce copper from small, deep, and/or low-grade copper oxide deposits. Approach Investigate the feasibility of a new mining method-in situ leach mining-as an alternative to conventional mining for copper. Study fundamental leaching technology that will […]
How to Make Lead from Galena Concentrates
Objective Provide an environmentally compatible means of producing lead from galena concentrates that replaces the current high-temperature pyrometallurgical primary lead smelting process and supplies pure lead metal within present and proposed Environmental Protection Agency (EPA) and Occupational Safety and Health Administration (OSHA) lead emission standards. Approach The U.S. Bureau of Mines developed an energy efficient […]
Heap Bio-oxidation of Sulfide Concentrates
Low-cost oxidation pretreatment technologies are needed in order to economically extract precious metals from refractory sulfidic deposits as the world’s free-milling reserves are consumed. Already, more than one-third of the gold ore reserves in the United States are considered to be refractory. Many of the deeper gold deposits that are currently being discovered, including deeper […]
Silver Chloride Precipitation & Separation
The unique insolubility of silver chloride makes it possible to readily achieve a distinctive separation of silver from a mixed metal ion acidic solution. Using chloride precipitation with NaCl solution, the plant operation selectively removes all the silver from the pressure leach solution. The chemistry is quite straightforward and effective. As with most processes, it […]
Palladium Leaching in Ammonia
Recently, a number of techniques of recovering Palladium have been developed. For example, leaching of platinum group metals from spent automobile catalytic converters using halogen salt with oxygen was developed. Ammonia is an inexpensive lixiviant used in leaching precious metals such as silver and gold. Since palladium has some similar chemical properties to silver, it […]
Chalcopyrite Leaching by Iodine
Chalcopyrite is the most abundant mineral of copper sulfide minerals and the major source of copper. Numerous leaching processes, such as ammoniacal systems, acid sulfate systems, chloride systems, and nitrate systems, have been introduced and investigated. In oxygenated ammoniacal solutions, chalcopyrite dissolves according to the following reaction: CuFeS2 + 4NH3 + 17/4 O2 + 2OH- […]
Types of Pressure Oxidation Autoclave Lining
As shown in Figure 1, there are other accessory vessels (splash and flash towers) in the autoclave circuits, that are also brickwork lined. The linings used to date, other than small test sections, have all been acid-resistant fireclay bricks, bonded with alkali silicate mortar, PbO-based mortar, and/or vinyl ester mortar, but mainly alkali silicate mortar. […]