Research On Copper Recovery From Waste Printed Circuit Boards By Hydrometallurgical Methods

Waste printed circuit boards (PCBs) have been attracting the public attention by its environmentally harmful materials and abundant valuable non-ferrous metals. If the waste PCBs are improperly disposed, hazardous materials could cause serious environmental problems and numerous valuable metals would be lost. In this regard, a green process for leaching copper from shredded particles of waste PCBs at room temperature was investigated in the present research.Waste PCBs contain mainly metal copper and other heavy metals were pretty low. Therefore, sulfuric acid-hydrogen peroxide leaching system was used to obtain pure cupric sulfate solution directly for copper refining. Leaching copper from shredded particles of waste printed circuit boards (PCBs) was carried out in sulfuric acid solution using hydrogen peroxide as an oxidant at room temperature. The results shown that the optimum addition amount was 100ml 15% (wt) sulfuric acid solution and 10 ml of 30% hydrogen peroxide for leaching 10 g waste PCBs powder with a solid/liquid ratio of 1/10 for 3 h at room temperature (~23℃). Moreover leaching temperature and initial copper ion concentration had insignificant effect on the leaching recovery of copper.Waste PCBs shredding is a high energy-consumption process. Thus specimen with a larger shredding particle would lower the energy consumption. The effect of different particle size of shredded waste PCBs on leaching of copper was investigated under the optimum leaching condition. The results revealed that shredding pieces of waste PCBs smaller than 1 mm was efficient and suitable for copper leaching. Then a reasonable shredding process was proposed and 84.67% (wt) of PCBs pieces were shredded smaller than 1 mm finally.The leaching solution was concentrated to crystallize pure CuSO4·5H2O product. Since the crystal liquor was mainly consisted of cupric sulfate and sulfuric acid, the reuse of the crystal liquor could avoid the emission of acid waste water with copper content. The recovery of copper reached 96% for the 5 cycles of reusing the raffinate produced from the crystallization to the leaching step, which showed that reusing the crystal liquor at leaching step was feasible.