Cementation of Gold on Copper & Zinc Electrochemistry
The cementation of gold on to copper and zinc in ammoniacal solutions has been investigated using electrochemical techniques and conventional cementation experiments: Studies of cathodic reduction of Au(NH3)2+ have shown that the cathodic reaction can be expressed as: Au(NH3)2+ + e = Au + 2NH3 and the standard reduction potential, E°, has been estimated to […]
Electrowinning Mercury in Gold Pregnant Solution
Many gold-bearing ores in the Western United States also contain small amounts of mercury. The presence of mercury creates potential pollution and health hazards during several steps in gold processing. An investigation was undertaken by the Bureau of Mines to develop techniques for removing mercury from cyanide mill solutions by selective electrowinning to reduce the […]
Electrowinning Tankhouses Air Quality
Electrowinning is an electrochemical operation employing an anode and cathode immersed in an electrolytic solution containing sulfuric acid and aqueous copper sulfate. When direct electrical current passes between the cathode and anode through the electrolyte, very pure metallic copper is deposited on the surface of the cathode. The process is conducted commercially in electrolytic cells […]
Reduce Ball Mill Wear by Cathodic Protection
The present work was undertaken to develop a method to cathodically protect a ball mill to reduce materials loss from mill liners. The essential science of “Cathodic Protection” is to apply a sufficiently negative potential to a metal in a corrosive environment such that the anodic corrosion rate is reduced to a negligibly small or […]
Electrorefining Calcium Metal Electrowinning
The U.S. Bureau of Mines developed an alternative electrochemical process for the production of calcium metal. The current industrial practice is costly, complex, and inefficient. The Bureau method involved electrowinning of a calcium-tin alloy followed by electrorefining to produce calcium metal. In the electrowinning cell, CaCl2 was fed to a KCl2-CaCl2 electrolyte. The calcium was […]
Laboratory Zadra Electrolytic Cell
A ZADRA electrolytic cell adapted to strip gold from sulfide solutions thereof which comprises a cathode assembly having a vertical metallic pipe adapted to deliver gold-bearing solution to the cell and to serve as a negative bus bar for delivering electric current to said cell, said pipe being axially positioned in said cell and being […]
Electrical Separation of Minerals
For characterising the electrical behaviour of chemically conditioned mineral samples and after charging the minerals with the body of the stainless steel mill they are subjected to an electrostatic free fall separator by using a steel feeder. Based on the polarity and the magnitude of the charges acquired by mineral grains they are attracted by […]
How to Recover Chrome Metal from Scrap Alloy
Fluidized-Bed Roasting of Chromium Sulfide The chromium concentrate produced either directly as flotation tails or indirectly as a leach residue is composed primarily of chromium sulfide with chromium comprising about 80 percent of the metal content. Nickel and molybdenum sulfides would be present in the flotation tails along with heavy metal oxides. The leach residue […]
Process for Recovering Chromium Scrap
Described here is a process for recovering chromium and other metals from superalloy scrap. Laboratory-scale experiments were conducted to test a complex flowsheet utilizing a wide range of extractive metallurgical operations. The novel basis for the process is the formation of a sulfide matte in which chromium is concentrated in a discrete chromium sulfide phase. […]
Insoluble Anodes for Electrowinning Zinc & Metals
This Bureau of Mines investigation was prompted by the need for a stable anode for electrowinning metals, particularly zinc and copper, from acid solutions. The polarization behavior of Pb-Ag (1 pct Ag) anodes in H2SO4 and fluoride solutions was determined as the first step in the development of such an anode. A Luggin capillary, DC power […]