Copper recovery

Asahi Chemical Industries (ACl, Japan) are now the leading producers of cuprammonium rayon. In 1990 they made 28,000 t/yr of filament and spunbond nonwoven from cotton ceUulose (65). Their continuing success with a process which has suffered intense competition from the cheaper viscose and synthetic fibers owes much to their developments of high speed spinning technology and of efficient copper recovery systems. Bemberg SpA in Italy, the only other producer of cuprammonium textile fibers, was making about 2000 t of filament yam in 1990. 

Many waste-rock or overburden disposal systems result ia compacted dumps having uncontrolled distribution of fines. In such dumps, solution distribution is poor and there is Htde oxygen for reaction with the sulfides. Methods for managing these dumps to maximize copper recovery have been actively pursued. 

The recovery of copper powder from wastewater of electronic industries was investigated in three-phase inverse fluidized-bed electrode reactors(0.102m ID x 1.0m). Effects of gas and liquid velocities, current density, distance between the two electrodes and amount of fluidized particles on the recovery of copper powder were examined. The addition of a small amount of gas or fluidized particles into the reactor resulted in the decrease in the powder size of copper recovered as well as increase in the copper recovery. The value of copper recovery exhibited a maximum with increasing gas or liquid velocity, amount of fluidized particles or distance between the two electrodes but increased with increasing current density. 

Effects of current density(I) on the recovery of copper in the reactor can be seen in Fig. 5. As can be seen, the value of R increased gradually with increasing ciurent density, since the mass transfer rate of copper ion is proportional to the current density. Effects of amount of fluidized particles on the recovery of copper can be seen in Fig. 6. Note that the addition of a small amount of fluidized particles (W=1.0wt.%) to the reactor could increase the copper recovery up to 10 25%. It has been mderstood that the contacting of fluidized solid particles with the cathode plate could clean the siuface as well as decrease the diffusion layer of copper ion, which results in the increases of reaction rate and current efficiency, thus, the recovery of copper could be increased. 

However, when the amount of added particles increased(W=2.0 or 3.0wt.%), the effective surface area of cathode plate decreased due to the considerable increase of solid holdup between the two electrodes, thus, the amount of copper recovery decreased. In this experimental conditions, the distance between the two electrodes(LAc) also influenced the recovery of copper, as can be seen in Fig. 7. In this figure, the value of R was maximum when the distance(LAc) was 1.5cm, in all the cases studied. 

The conversion process for the copper matte removes iron, sulfur and other impurities from matte, thereby yielding liquid metallic copper of about 99% purity (blister copper). The slags which come out of converters contain from 2 to 15% copper and must go through treatment for copper recovery, usually by froth flotation of the copper from solidified and slowly cooled slag. 

The regeneration and copper recovery system for the primary pickle bath... 

Block B shows the electrolytic copper recovery cell, which recovers metallic copper and regenerates sulfuric acid from the metal salts in the hot sulfuric acid pickle solution. It was originally felt that trace metals (zinc, tin, lead) would interfere with the recovery of pure copper. By controlling current density at 50 to 100 A/m 1 2 3, however, pure copper can be recovered while maintaining the copper concentration in the pickle bath at 15 g/L. 

The secondary pickle reservoir is also shown in Block B. Copper sulfate accumulates in this bath and eventually crystallizes out. These crystals can be recovered and sold as a copper-rich sludge or added to the electrolytic copper recovery loop. 

The dross is removed and fed into a dross furnace for recovery of the nonlead mineral values. To enhance copper recovery, dressed lead bullion is treated by adding sulfur-bearing materials, zinc, and/or aluminum, lowering the copper content to approximately 0.01%. 

The application of solvent extraction to copper recovery has been a major growth area since the last review of this series.11,13 Almost 30% of world production in 2000 involved the use of sulfuric acid heap leaching, solvent extraction, and electrowinning, far exceeding earlier predictions.136... 

Using TY3 collector improved the copper recovery by 10%, while the cobalt recovery remained unchanged. The consumption of sulphidizer in the presence of TY3 was significantly reduced. 

One of the main problems associated with beneficiation of the Kolwezi siliceous ore is the production of malachite and pseudomalachte slimes that have a relatively low flotation rate. Most of the copper losses occurring in the plant are in the -15 pm fraction. Experimental testwork conducted with a different palm oil emulsifier indicated that copper recovery from the fine fraction can be significantly improved with the use of petroleum sulphonate (Petrosol 845) as the emulsifier [21] for palm oil. Significant improvement in copper recovery was realized in the fine fractions with the use of palm oil emulsified with Petrosol 845. 

In the 1980s, a new collector (i.e. fatty acid-modified xanthate) was introduced into the Kolwezi concentrator with significant improvement in copper recovery. In 1995, collectors from the PM series were tested in the Nchanga concentrate improving results. The plant results obtained in the Kolwezi concentrate using xanthate and TY3 are compared in Table 19.10. Collector TY3 also had a positive effect on cobalt recovery. 

Copper plating, 9 764, 766, 804-807 Copper pollutants, 9 443-444 Copper pyrophosphate deposition, 9 809 Copper recovery... 

Fig. 14.17 Copper recovery units (MECER) integrated in the production of printed circuit boards. This photograph shows the solvent extraction unit.

The greater affinity of humic acids for copper or lead ions is clearly reflected in the extraction values reported in Fig. 2.1. In particular, far less of the adsorbed material was displaced by the salt solutions. The amount of lead retrieved by these extractants, and also with the mineral acids and buffer solutions, exceeded the copper recoveries, so copper appears to be more firmly bound than lead on the humic acid samples studied. 

Because of cost factors, solvent extraction applied to large scale hydrometallurgical processes, such as the recovery of copper from acidic ore leach solutions, is carried out with the most selective reagent for e.g., copper versus iron, which is not itself a liquid solvent, in a petroleum diluent that confers on the mixture the desired physical properties. For the particular case of copper recovery, commercial hydroxyoxime reagents have been used on a very large scale, but their discussion is outside the scope of this book. 

Figure 11.16 Schematic of copper recovery by coupled transport from dump leach streams. The concentrated copper solution produced by coupled transport separation of the dump leach liquid is sent to an electrolysis cell where copper sulfate is electrolyzed to copper metal and sulfuric acid...

The systems described above all result in the transport of metal cations across a metal-recovery circuit. In many cases this leads to very good materials balances in metal-recovery, especially when the circuit uses acid-leaching of the ore followed by solvent extraction using an organic acid (LH). The extraction then releases protons back into the aqueous phase, regenerating the acid needed for leaching. This underpins the very successful copper recovery operations outlined in Figure 7 in which copper oxide in the crude ore is essentially split into its component elements with the consumption of only electrical power. 

Kordosky, G. A. (2002) Copper recovery using leach/solvent extraction/electrowinning technology forty years of innovation, 2.2 million tonnes of copper annually, in International Solvent Extraction Conference, Cape Town, South Africa, Mar. 17-21, 2002. 

Urtiaga, A., Abelian, M.J., Irabien, J.A. and Ortiz, I. (2005) Membrane contactors for the recovery of metallic compounds Modelling of copper recovery from WPO processes. Journal of Membrane Science, 257, 161. 

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