Selective Copper Recovery by Acid Leaching from Printed Circuit Board Waste Sludge

Abstract

The most challenging issue associated with recycling the sludge generated from printed circuit boards (PCBs) is the separation of copper (Cu) from iron (Fe), using multi-stage leaching, or adding oxidizing and precipitating agents. Herein we investigated simple acid leaching to effectively extract copper and limit iron dissolution. Selective copper leaching was achieved with all the acids studied, including HCl, HNO3, and H2SO4. The lower concentration of acid solutions resulted in a larger difference in leachabilities between Cu and Fe. Among three leachates, the H2SO4 solution performed effectively on the selective leaching of Cu and Fe. Adjusting the pulp density to 4% and the H2SO4 concentration at ~0.2 M, accomplished ~95% Cu leaching and reduced the Fe extraction to less than 5%. Kinetic studies revealed that Cu leaching followed the ash diffusion-controlled mechanism. Aactivation energy (Ea) of 9.8 kJ/mol was determined for the first 10 min of leaching. Further, leaching up to 60 min corresponded to a mixed control model, increasing the Ea to 20.9 kJ/mol. The change in the control model with regard to the two leaching stages can be attributed to the Cu hydroxide and metal phases present in the original sample. A simple, economically attractive H2SO4 acid leaching process was demonstrated, recovering Cu efficiently and selectively from PCBs waste sludge under moderate conditions.

Selective Recovery of Copper from Industrial Sludge by Integrated Sulfuric Leaching and Electrodeposition

“…The phases of Cu and Fe were further characterized using thermogravimetric and differential thermal analyses (TGA-DTA, DTG 60H, Shimadzu, Japan), as well as X-ray diffraction (XRD, D2 Phaser, Bruker, Germany). The results show that the copper in the waste sludge is in the form of Cu(OH) 2 and Cu metal, while Fe mainly presents as Fe(OH) 3 and a minor amount of Fe(OH) 2 [27]. The chemical composition of the Cu-bearing sludge was analyzed by the wet method and is listed in Table 1.…”

“…The single acid leaching indicates that Cu and Fe from the Cu-bearing sludge were effectively dissolved in the H 2 SO 4 solution even without a supplement of electrical current or oxidants due to the major phases of Cu and Fe as hydroxides (Equations ( 3)-( 5)) [27]. The dissolution of Cu metal occurred on account of the presence of Fe 3+ as an oxidizing agent (Equation ( 6)) [27].…”

“…The single acid leaching indicates that Cu and Fe from the Cu-bearing sludge were effectively dissolved in the H 2 SO 4 solution even without a supplement of electrical current or oxidants due to the major phases of Cu and Fe as hydroxides (Equations ( 3)-( 5)) [27]. The dissolution of Cu metal occurred on account of the presence of Fe 3+ as an oxidizing agent (Equation ( 6)) [27]. Especially, the dissolution efficiency of Cu and Fe were significantly high (Cu (~90%) and Fe (~72%)) at the beginning of the leaching process (5 min), and the dissolution of Cu and Fe were almost completed and became constant after 60 min (Figure 2a,b).…”

Copper Recovery from Printed Circuit Boards Waste Sludge: Multi-step Current Electrolysis and Modeling

“…Currently, to recover metals from the sludge, some methods, for example, a pyrometallurgical method [5,6], a hydrometallurgical method [4,[7][8][9], or a combined hydro-pyrometallurgical method, [10] have been used. Among them, the hydrometallurgical method is regarded as an efficient method.…”

“…Among them, the hydrometallurgical method is regarded as an efficient method. Typically, this involves leaching processes, which use acidic solutions [6,[11][12][13], basic solutions [13], or bioleaching agents [9,14]. After leaching, metal ions can be recovered by various techniques such as cementation, solvent extraction and precipitation, or electrolysis [3,10,[14][15][16][17][18].…”