Copper Leaching Behavior from Waste Printed Circuit Board in Ammoniacal Alkaline Solution

Abstract

A novel energy-saving hydrometallurgical recovery process for copper from electronic scrap employing the Cu(I)-ammine complex has been presented on the basis of a thermodynamic consideration. In order to experimentally explore the feasibility of the leaching stage in this process, the copper leaching behavior from a printed circuit board (PCB) in ammoniacal alkaline solutions has been investigated under a nitrogen atmosphere. Copper in PCB was oxidized by Cu(II) to form Cu(I)-ammine complex ions. The leaching reaction can be expressed as:The Cu(II)-ammine complex significantly enhanced the leaching rate, while the Cu(I)-ammine complex slightly depressed it. Crushing of the PCB effectively enhanced the leaching rate, because the exposed metallic copper area is increased by the crushing. The effect of temperature on the leaching rate was insignificant. Consequently, the feasibility of the leaching stage in the proposed copper recovery process has been experimentally confirmed.

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

“…In a previous study, we carried out the leaching experiments and reported that the copper in a printed circuit board (PCB) dissolved as Cu(I) in the Cu(I)-Cu(II)-NH 3 -(NH 4 ) 2 SO 4 solutions under a nitrogen atmosphere. 1) The electrowinning of copper is also important in order to develop the copper recovery process. There are some complexing agents with copper(I) such as NH 3 , CN À , Cl À and acetonitrile, where Cu(I) is stable in these solutions.…”

“…1) This process consists of three stages; leaching, purification, and electrowinning, and is characterized by employing an ammoniacal alkaline solution and electrowinning from Cu(I). In a previous study, we carried out the leaching experiments and reported that the copper in a printed circuit board (PCB) dissolved as Cu(I) in the Cu(I)-Cu(II)-NH 3 -(NH 4 ) 2 SO 4 solutions under a nitrogen atmosphere.…”

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

“…Among them ammonia solutions were used, mainly for selective dissolution of copper and other metal ions (e.g. nickel, zinc) in carbonate, sulfate, chloride baths [9][10][11] or gold and silver in thiosulfate baths [12][13][14]. High purity copper was then recovered by electrowinning from Cu(I) or Cu(II) ammoniacal baths [15][16][17].…”

Influence of Electrolyte on an Energy-Saving Copper Recycling Process Using Ammoniacal Alkaline Solutions

“…This process employs an ammonia (NH 3 )-ammonium salt solution containing cuprous ammine complexes (Cu(I)) and cupric ammine complexes (Cu(II)), and consists of three stages of leaching, purification and electrowinning, as described in our previous paper. 5) In this process, copper metal in the waste is dissolved as Cu(I) into the solution using Cu(II) as the oxidizing reagent in the leaching stage. After purification, the pure Cu(I) solution is introduced into the cathode compartment of the electrolytic cell, and half of the fed Cu(I) is reduced to metallic copper on the cathode.…”

“…Thus, it is necessary to reduce the power consumption during the electrowinning to make the process economical and comparable to the low market price for copper. Based on this background, our research group has been making efforts to develop an energy-saving copper recycling process from electronic waste [5][6][7][8] that is one of the most complex materials for recycling. This process employs an ammonia (NH 3 )-ammonium salt solution containing cuprous ammine complexes (Cu(I)) and cupric ammine complexes (Cu(II)), and consists of three stages of leaching, purification and electrowinning, as described in our previous paper.…”