A green slurry electrolysis to recover valuable metals from waste printed circuit board (WPCB) in recyclable pH-neutral ethylene glycol

The continuous growth of e-waste necessitates an efficient method to recover their metal contents to improve their recycling rate. The successful recovery of the metallic component from Waste Electrical and Electronic Equipment (WEEE) can generate great economic benefits to incentivize the industrial recycling effort. In this study, we report the use of slurry electrolysis (SE) in pH-neutral ethylene glycol (EG) electrolyte to extract and recover the metallic component from waste printed circuit broad (WPCB) powder. The system operates at room temperature and atmospheric pressure, and the electrolyte can be recycled multiple times with no signs of chemical degradation. The EG electrolyte system can oxidize the metallic component without triggering anodic gas evolution, which allowed us to incorporate a reticulated vitreous carbon (RVC) foam anode to maximize the capture and oxidation of the metal content. The system demonstrated up to 99.1% Faraday efficiency for the cathodic metal deposition and could recover Cu from the WPCB powder in a selective manner of 59.7% in the presence of 12 other metals. The SE reaction system was also scalable and displayed no compromises on the Cu recovery selectivity. With the ability to leach and recover metallic content from WPCB in a mild and chemically benign condition, the SE system displayed much promise to be adapted for industrial-scale metal recovery from WPCB. Reference Liu, K., Lam, JCH. et al. "A green slurry electrolysis to recover valuable metals from waste printed circuit board (WPCB) in recyclable pH-neutral ethylene glycol." J. Hazard. Mater. 2022433: 128702.Liu, K., Lam, JCH. et al. "Teaching Electrometallurgical Recycling of Metals from Waste Printed Circuit Boards via Slurry Electrolysis Using Benign Chemicals." J. Chem. Educ. 2023 100(2): 782-790. Figure 1

Superfine copper powders recycled from concentrated metal scraps of waste printed circuit boards by slurry electrolysis

Precious metals recovery from waste printed circuit boards: A review for current status and perspective

Recovery of high purity copper from waste printed circuit boards of mobile phones by slurry electrolysis with ammonia-ammonium system

The interface delamination of waste plastic chip will seriously affect the value of their recycling reuse; therefore, it has been a hot issue in recycling researches of Waste Electrical and Electronic Equipment (WEEE).Based on the exponential cohesion theory, this paper has researched chip delamination and established the Cohesive Zone Model (CZM) of delamination crack for chip interface, as well as proposed a method which combined the experiment of crack surface observation and the simulation of fracture mechanics.By employing this method, the CZM parameters of waste plastic chip interface have been obtained.Based on the CZM, the simulation of waste plastic chip interface delamination has been made, and its results showed that: temperature and humidity factors have a significant impact on the chip delamination.At last, the disassembly experiments of Waste Printed Circuit Boards (WPCB) have been made under different disassembly technology, and the delamination rate of resulting chips has been calculated.Then this paper has analyzed the influence rule of different disassembly conditions on the chip delamination and verified the correctness of chip delamination simulation results, as well as proposed an optimized disassembly technology of WPCB for reducing plastic chip's delamination.

Copper and gold recovery from CPU sockets by one-step slurry electrolysis

Constant growth in waste electrical and electronic equipment (WEEE) levels necessitates the development of new, commercially viable recycling processes. Waste printed circuit boards (WPCBs) are a sub-group of WEEE that are of increasing interest due to their relatively high level of valuable metal content including Au, Ag, and platinum group metals (PGMs). Currently, precious metals like gold are mainly recycled from WEEE streams through copper smelting/refining; however, the possibility to peel gold from WPCBs prior to smelting, could offer advantages for recycling. In this study, the suitability of aqua regia for selective or partially selective gold leaching from un-crushed WPCBs was investigated. The redox potential of aqua regia solutions and the dissolution efficiencies of Au, Cu, and Fe from WPCBs were investigated at different temperatures (40–80 °C) and concentrations (2–32%) in batch leaching tests. The redox potential of aqua regia solution was found to depend on concentration and temperature. It is suggested that Au dissolution in aqua regia requires dissolved Cu2+ ions originating from the WPCB material to work. Au extraction (>50%) was shown to require a redox potential >700 mV with [Cu2+] > 2500 ppm, as a potential >850 mV alone was insufficient without cupric ions. Significant amounts of Au and Cu could be dissolved with only minor Fe dissolution at ≥8% aqua regia at 80 °C. Results suggest that leaching of uncrushed WPCBs in 8% aqua regia (T = 80 °C) can provide the opportunity for partial Au recovery prior to further processing.

A combined process of reverse flotation and slurry electrolysis for step-by-step recovery of copper and gold from waste printed circuit boards.

EFFECT OF 5 WT.% WPCB POWDER AS REDUCTANT ON INDONESIAN LIMONITICNICKEL ORE PROCESSING. Waste printed circuit boards (WPCB) are among the most valuable parts of electronic waste with one of the fastest-growing waste streams in the world. The purpose of this study is to investigate the possibility of WPCB powder as an alternative reducing agent for the carbothermic process in nickel lateritic ore processing. WPCB waste was mixed with nickel ore at 1100ÚC in inert atmosphere. In addition, a conventional reductant of coal is also utilized for comparison. Both reductant are varied in concentration of 5 wt% and 15 wt%. Based on thermogravimetric analysis (TGA) and differential thermogravimetric analysis (DTA) investigation, it is observed that there exists a difference between WPCB powder, nickeliferous ore powder, and the mixture in their decomposed levels. The decomposed gasses of WPCB produced by thermal degradation in the TGA instrument are mainly composed of reduction gas, which plays a critical role in reducing the nickeliferous ore. This study shows that WPCB powder performs comparably to sub-bituminous coal in the pyrometallurgical processing of nickel ore, which is proved by X-Ray Diffraction (XRD) test results that the carbothermic products consists of FeNi, magnetite, wustite and fayalite. It can be concluded than WPCB powder has potential to be utilize as an alternative reductant.

Electrode-electrolyte interactions in choline chloride ethylene glycol based solvents and their effect on the electrodeposition of iron

Recycling of non-metallic fractions from waste electrical and electronic equipment (WEEE): A review

A profitability assessment of European recycling processes treating printed circuit boards from waste electrical and electronic equipments

Metal recovery from waste printed circuit boards: A review for current status and perspectives

Recycling metals from -0.5 mm waste printed circuit boards by flotation technology assisted by ionic renewable collector

Effect of metals and brominated flame retardants on thermal degradation kinetics of waste printed circuit board