Electrowinning and electrorefining

Electrolytic Processes. The electrolytic procedures for both electrowinning and electrorefining beryUium have primarily involved electrolysis of the beryUium chloride [7787-47-5], BeCl2, in a variety of fused-salt baths. The chloride readUy hydrolyzes making the use of dry methods mandatory for its preparation (see Beryllium compounds). For both ecological and economic reasons there is no electrolyticaUy derived beryUium avaUable in the market-place. 

In the field of electrowinning and electrorefining of metals, titanium has an advantage as a cathode, upon which copper particularly can be deposited with finely balanced adhesion that allows the electrodeposited metal to strip easily when required. Titanium anodes are also being employed as a replacement for lead or graphite in the production of electrolytic manganese dioxide. 

Electrochemical Reduction of C02 in Non-Aqueous Solvents 321 Use of Acetonitrile in Electrowinning and Electrorefining of Copper 323... 

In electrorefining, the anodic reaction is oxidation and dissolution of metal by the generic reaction (6). The cathodic reaction in both electrowinning and electrorefining is the reduction and deposition of metal ion by the generic reaction (7)... 

Fig. 10 Parallel-plate cell used in traditional electrowinning and electrorefining.

M. Olper, M. Maccagni, Electrowinning and electrorefining of base metals using unconventional electrolytes. Electrometallurgy, Toronto, Canada, 2001, pp. 17-32. 

Table 5.4 Parameters of electrowinning and electrorefining in ionic liquids and in industrial...

Cook, G. M. Twenty-five years progress in electrowinning and electrorefining of metals. J. Electrochem. Soc., 125 49C, 1978. 

The electrolytic production of materials is one of the oldest branches of electrochemical technology. Electrowinning and electrorefining of metals, electroplating, and electrolytic gas production are but a few examples. While still at an evolutionary stage, electroprocessing of materials presents enormous potential opportunities and could well have a significant commercial impact. A few examples are described below and are not intended to be all inclusive. 

The current distribution on a macroprofile is very important in technical metal electrodeposition. In electroplating, the current distribution determines the local variations in the thickness of the coating. In electrowinning and electrorefining of metals, a non-homogeneous current distribution can cause a short circuit with the counter electrode and the comer weakness effect in electroforming. This is very important in the three-dimensional electrodes, as well as in some storage batteries. In all the cited cases, a uniform current density distribution over the macroprofile is required. 

Hatch has completed a study to compare a number of intercell contact bar designs currently available in the market for their use in electrowinning and electrorefining plants. The different designs have been compared on a number of bases to determine their ability to produce consistent product and minimize operating costs. 

At the time of writing this paper, three plant trials are currently underway with promising early signs. The sites selected for the trial are spread between Australia and the United States of America in the production of copper in electrowinning and electrorefining plants. Following the completion of these trials in early 2013, it is expected that commercial units will be available for sale by the end of Ql, 2013. All trials to date have been for copper with the next step to include commercial trials in nickel, cobalt and zinc operations. 

Chart 6 depicts the change in the structure of the electrowinning and electrorefining of nonferrous metals between 1958 and 1963. The most important changes in the structure of this component were a decline in the relative importance of tinplating, a moderate increase in the share of aluminum, and a large increase in the importance of copper. 

Consider the electrolyte hydrodynamic flow condition shown in Figure 7.17. This is amass transfer found in electrowinning and electrorefining cells, in which the electrolyte motion is upwards on the anode surface due to the generation of oxygen bubbles, which enhances the mass transfer. The reader can observe in this model that the electrolyte motion is more intense at the top than at the bottom of the electrode as indicated by the arrows. If the current flows, then the electrolyte motion increases and descends to the bottom of the cathode. This is the case in which a significant convective molar flux is superimposed on the Pick s diffusion molar flux. The concentration gradient in the fluid adjacent to the vertical electrode (plate) surface causes a variation in the fluid density and the boundary layer (tf ) develops upwards from laminar to turbulent conditions [2,7]. 

---