Electrowinning economics

The development of selective extractants for copper has made extraction from dilute solutions (1—5 kg/m ) economically feasible. Transfer of the copper by stripping to a more concentrated sulfuric acid solution, ie, 30—40 kg/m for Cu " and 150—170 kg/m for H2SO4, from which the copper is recovered by electrowinning. The simplified reaction,... 

Copper. Copper is economically extracted by smelting of a chalcopyrite concentrate. A copper electrowinning process was developed commercially in 1912 for the treatment of lean ores. It is also suitable for treatment of copper oxide or sulfate obtained by roasting of the concentrate. 

Fused-salt electrolysis of K2NbFy is not an economically feasible process because of the low current efficiency (31). However, electrowinning has been used to obtain niobium from molten alkaU haUde electrolytes (32). The oxide is dissolved in molten alkaU haUde and is deposited in a molten metal cathode, either cadmium or zinc. The reaction is carried out in a ceramic or glass container using a carbon anode the niobium alloys with the cathode metal, from which it is freed by vacuum distillation, and the niobium powder is left behind. 

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. 

Increasingly more copper is being produced by electrowinning because of economics and technical advances, such as in solvent extraction processes. Certain brands obtained by SX—EW are treated as cathode quahty and are used directly by wire-rod manufacturers. Whereas in 1984 100,180 t of copper was electrowon in SX—EW plants, in 1992, 439,043 t produced by SX—EQ was electrowon (7). 

To establish the economic feasibility of producing wire bar-grade copper by a combined SX-EW (EW = electrowinning) process... 

The process flow sheet was first tested for direct leaching of steel mill flue dust and production of zinc metal by electrowinning. The tests were performed in a continuously operating pilot plant, producing 10-20 kg/day zinc metal. The same pilot plant was then used for treating copper/zinc-rich brass mill flue dust in a closed loop operation, recycling all the zinc solvent extraction raffinate to the copper circuit leach section. In the zinc circuit leach section, only the amount of zinc rich dust necessary for neutralization of the copper solvent extraction raffinate was used. The results obtained from the pilot plant tests indicated contamination problems within the solvent extraction loops. The estimation of economic data showed a weak return on the assets compared with the alkali route, and sensitivity toward the raw material price. 

Figure 25 shows the general process steps for the melting route. All components of the alloys must he in metallic form, either as elements, or as master alloys which may he available more economically. Examples of the latter are RE-TM eutectic alloys (except with Sm) prepared by electrowinning, and Fe-Zr or Fe-Ti which are standard products for the steel industry. The RE metals used are made either metallothermically by reducing RE-oxides with calcium (and in the case of Sm with La or mischmetal) as the reductant, or by molten-chloride electrolysis. Electrolytic methods do not work with samarium because of its stable divalent state. Samarium is usually further refined by vacuum distillation, which is easy because of the low boiling point. 

For the zinc concentrates tested by Dynalcc an expansion of an existing roast-leach-electrowin plant using pressure leaching offers economics that arc favourable in comparison to those of an atmospheric leach. 

The British company Reunion Mining Pic (RM) performed a techno-economical feasibility study for the Skorpion mine (Namibia) during 1S 7 and 1998. At that time, RM entered in contact with the R D Division of Tunicas Reunidas S.A. (TR). The objective was to apply the modified ZINCEX process (MZP) to the treatment of Skorpion ore to produce SHG zinc. One of the most important stages of the feasibility study was the piloting of key sections of the process namely, leaching, solvent extraction and electrowinning. 

A good share of the research on electrowinning of the rare earth metals in the past 15 years has been devoted to the reduction of the rare earth oxide. Although good quality metals have been produced on a laboratory scale by this method and economically it appears to be cheaper than the chloride process, to date no company has successfully demonstrated that large quantities can be produced over an extended period of time (6 months to one year) by this technique. 

Wallis, T. L. and Chlumsky, G. F. 1999. Economic considerations for SX/EW operations. In Copper leaching, solvent extraction, and electrowinning technology, ed. G. V. Jer-gensen II, 89-91. Littleton, CO Society for Mining, Metallurgy and Exploration. 

In order to analyze an electrowinning cells from economical point of view, the power and the energy consumption needed to operate the cell are, respectively... 

With regard to traditional water treatment technologies and their markets, new solutions should be found in order to settle current and future problems, as well as to improve the economical and ecological situations of several leading-edge processes. Electrochemical processes, such as electrodialysis, electrowinning, electrodeionization, electroflotation, electroflocculation and others, appear to provide solutions in certain ways to several problems. 

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