Hydrometallurgical Recycling Process Research Articles

Recovery of ultrafine copper particles from metal components of waste printed circuit boards

Waste printed circuit boards (WPCBs) contain plenty of valuable resources and hazardous materials, considered both an attractive secondary resource and an environmental contaminant. In the current research, a hydrometallurgical process combined ammonia leaching and solvent extraction to recover copper from the metal components of WPCBs, and the production of ultrafine copper particles stripped from a solution was investigated. The results of copper oxidation leaching indicated that 96.7% of copper can be recovered at a temperature of 35°C for a leaching duration of 2h with ammonium sulfate and ammonia concentration of 2mol/L at a solid:liquid ratio of 1:10g/cm3. The treatment of leach liquor for solvent extraction of copper with LIX 84 showed that 50% LIX 84 in kerosene, a 3min period of equilibration, and a pH of 10 were sufficient for the extraction of Cu(II) and 99.6% copper can be recovered from the leached solution. The results of the preparation of copper particles from stripped solution showed that mono-dispersed ultrafine copper particles with a diameter of approximately 1.5μm were obtained from the stripped solution containing 39.25g/L Cu2+ ion, oleic acid used as surfactant, and sodium hypophosphite as reductant. As the purity of the copper extracted from the leaching system was high and the as-synthesized ultrafine copper particles possess excellent anti-oxidation property, this WPCB metal-component hydrometallurgical recycling process has the potential of recovering high-purity ultrafine copper particles.

Pressure leaching of metals from waste printed circuit boards using sulfuric acid

Printed circuit boards (PCBs) are essential components of electronic equipments which contain various metallic values. This paper reports a hydrometallurgical recycling process for waste PCBs, which consists of the novel pretreatment consisting of organic swelling of PCBs followed by sulfuric acid leaching of metals from waste PCBs. To recycle the waste PCBs, experiments were carried out for the recovery of copper from the crushed and organic swelled materials of waste PCBs using sulfuric acid leaching in presence of hydrogen peroxide under atmospheric and pressure condition. The leaching of PCBs at 90°C, pulp density 100 g/L under atmospheric condition, using 6M sulfuric acid resulted in the dissolution of a minor amount of copper due to the presence of plastic coating on the surface of metallic layers. On the other hand, when the liberated metal sheets from organic swelled PCBs were treated with dilute sulfuric acid of concentration 2M along with hydrogen peroxide in an autoclave under oxygen atmosphere, the percentage recovery of copper was found to increase from 59.63% to 97.01% with an increase in hydrogen peroxide concentration from 5 to 15% (v/v) keeping constant pulp density 30 g/L.

Electrolytic Copper Deposition from Ammoniacal Alkaline Solution Containing Cu(I)

In order to verify the feasibility of copper electrodeposition from ammoniacal alkaline solutions containing Cu(I), the cathodic polarization characteristics of Cu(I) and the galvanostatic electrodeposition from a Cu(I) solution were investigated. The cathodic polarization curve for the 0.5 kmol m -3 Cu(I)-5 kmol m -3 NH 3 -1 kmol m -3 (NH 4 ) 2 SO 4 solution showed an increase in the electric current corresponding to the deposition of copper at around -0.22V vs. SHE which is much higher than the potential for hydrogen evolution. The current efficiencies for the copper electrodeposition from the Cu(I) solution nominally without Cu(II) were greater than 95% in the current density range of 200 to 1000 A m -2 . A further increase in the current density resulted in a decreased current efficiency due to the hydrogen evolution. The current efficiency decreased with the increasing Cu(II) concentration and temperature. These results indicate that the present copper electrodeposition method is applicable for the new energy-saving hydrometallurgical recycling process.