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

Abstract

The paper concerns a hydrometallurgical method for selective recovery of copper from low-grade electric and electronic wastes. The following consecutive stages were proposed: smelting of the scraps to produce Cu-Zn-Ag alloy, leaching of the alloy in ammoniacal solution, and selective copper electrowinning. Cu-Zn-Ag alloy was a polymetallic and five-phase system. It was leached in chloride, carbonate, sulfate and thiosulfate solutions. This resulted in the separation of the metals, wherein metallic tin and silver as well as lead salts remained in the slimes, while copper and zinc were transferred to the electrolyte. Copper was selectively recovered from the ammoniacal solutions by the electrolysis, leaving zinc ions in the electrolyte. The best conditions of the alloy treatment were obtained in the ammoniacarbonate system, where the final product was copper of high purity (99.9 %) at the current efficiency of 60 %. Thiosulfate solution was not applicable for the leaching of the copper alloy due to secondary reactions of the formation of copper(I) thiosulfate complexes and precipitation of copper(I) sulfide, both inhibiting dissolution of the metallic material.

Application of Ammoniacal Solutions for Leaching and Electrochemical Dissolution of Metals from Alloys Produced from Low-Grade E-Scrap

“…17%) in the alloy I and in tin (11% and 27%, respectively) in the alloy II. White areas distributed randomly in the bulk of the alloys were lead-rich phase (phase C) [19,20,22] confirms formation of copper-based matrix with tin and lead-rich phases separated out from the high copper phase. Steel fraction remains as randomly distributed inclusions [19,22].…”

“…Both alloys contained also traces of P and Cr (below 0.1%), while Ca (3.3 %) and Mo (0.1%) were detected additionally in the alloy II. Comparison of the data with the composition of other alloys produced from WEEE [19][20][21][22] shows that dependently on the origin of the scrap high copper metallic material can be produced (50-72% Cu). Tin contents in the smelted e-scrap can change from 2-3% [18,22] via 9-13% [19,24] up to 29% [20], whereas lead percentages are below 1% [21,23] or reach 9% [19,20].…”

“…Tin contents in the smelted e-scrap can change from 2-3% [18,22] via 9-13% [19,24] up to 29% [20], whereas lead percentages are below 1% [21,23] or reach 9% [19,20]. Total silver concentration in the alloys obtained from lowgrade e-waste is usually in the range 3-6% [18,[22][23][24], but this element can be distributed among copper and tin/lead rich phases, depending on the heat treatment temperature [21]. Percentages of remaining metals like Zn, Ni, Fe, Al, Au or Pt are variable.…”

“…A combined method was used: mechanical separation of the metallic parts from the main stream of plastics, melting of the rich metallic phase and dissolution of the obtained alloys in ammoniacal systems. Depending on the type of the WEEE origin a range of alloys can be obtained [18][19][20][21][22][23][24]. In the previous papers [22][23][24], smelted scraps were leached in ammoniacal solutions to dissolve copper via autocatalytic reaction [18,22,23] or anodically dissolved in acidic electrolytes [23][24][25].…”

Metal valorization from the waste produced in the manufacturing of Co/Mo catalysts: leaching and selective precipitation

“…The development of processes for the recovery of valuable metals from WEEE (waste electric and electronic equipment), spent catalysts, fly ash, and low-grade ores became a strategic research field for the last decade due to the high demand for critical metals and the rarefaction of metal resources. Pyrometallurgy and hydrometallurgy are the main processes for valorization of these mineral resources; gravimetric and magnetic separations of grinded materials are the first steps for the enrichment and separation of inorganic solids, prior to calcining, roasting or smelting (for pyrometallurgy) [1,2] or to leaching (for hydrometallurgy) [3][4][5]. Hydrometallurgy can be applied after pyrometallurgy has produced enriched solid concentrates for further separation.…”