The ammonia leaching of alloy produced from waste printed circuit boards smelting process

Abstract

The ammonia leaching tests were carried out to recover valuable metals from alloy obtained from smelting reduction process of mobile phone printed circuit boards. Leaching factors such as kinds of salt, ammonia concentration, and the interaction of metals, which are components of PCB, were investigated to improve the leaching efficiency. In the leaching tests using metal powders such as Zn, Sn, Ni, and Pb to investigate the interaction of metals, zinc was easily dissolved in ammonia solution, whereas Sn and Ni were not detected or the Pb concentration decreased rapidly. The metal concentrations increased with an increase in NH 3 concentration from 1 to 5 kmol m 23 . The content of Cu could increase to 98% under the leaching conditions: 2 kmol m 23 NH 4 Cl and 5 kmol m 23 NH 3 solution with 0.1 kmol m 23 CuCl 2 at 200 rpm and 308C with 1% pulp density.

Ammoniacal leaching and recovery of copper from alloyed low-grade e-waste

“…In fact, up to 5 mg/dm 3 Pb(II) was detected in the solutions, but a large scatter of the results with the time was found. Lim et al [10] reported leaching of lead powder in ammonium-ammonium sulfate bath and after initial lead dissolution a decrease of Pb(II) ions concentration was observed in relatively short time period. Oishi et al [16] stated that metallic lead can be easily oxidized by copper(II) ions to Pb(II) species in ammoniacal solutions.…”

“…This process is useful only for copper-rich alloys, since various phase composition can inhibit spontaneous copper dissolution from the metallic phase [11]. Usually, more concentrated solutions are applied for ammoniacal leaching of the scraps [e.g., 5 M NH 3 and 0.5 M Cu(II)] [8][9][10], however, in this study, fundamental behavior of the metals during spontaneous dissolution of the alloy was expected to investigate, hence less aggressive baths with natural oxygen content in the solutions were used. Figure 3 shows changes of the sample potential during the process.…”

“…Based on the previous experience [11], ammoniacal leaching of the multicomponent alloy and further electrolysis were selected for recovery of copper. Recently, Lim et al [10] presented comparative research on the behavior of some metals (Cu, Zn, Ni, Pb, Sn, Au, Ag) dissolved from pure powders and an alloy obtained from smelting reduction process of mobile phone and printed circuit boards, using sulfate and chloride ammoniacal solutions. In the current paper, the influence of ammonium salts was studied to determine the most suitable bath for the recovery of copper from alloyed electronic scraps.…”

“…Alkaline ammonia-ammonium salt solutions show some advantages in the leaching of polymetallic materials [8][9][10][11], since dissolution of copper is specific (autocatalytic):…”

“…Hydrometallurgical recovery of copper from metallic scraps is realized by leaching in acids under oxidative conditions [5,7] or in ammoniacal solutions [8][9][10].…”