Effect of ionic liquid [MIm]HSO4 on WPCB metal-enriched scraps refined by slurry electrolysis

Effect of Microwave Pretreatment on the Leaching and Enrichment Effect of Copper in Waste Printed Circuit Boards

The use of efficient and clean methods for the recycling of waste circuit boards is an ongoing challenge. In this research, the effect of microwave pretreatment on the leaching and enrichment of copper from waste print circuit board (WPCB) was studied. The morphology and chemical structure of WPCB particles before and after microwave pretreatment were analyzed by SEM/EDS and Fourier infrared spectroscopy. Leaching experiments and copper enrichment tests were designed to investigate the effect of different microwave irradiation powers and microwave irradiation times on the copper leaching rate and copper enrichment rate in WPCB. The leaching experiment results showed that microwave pretreatment can effectively improve the leaching rate of WPCB. When the microwave irradiation power was 700 W, the irradiation time was 120 s, and the leaching time was 15 min, the copper leaching rate in WPCB was 57.01%, which was 24.34% higher than that in the untreated condition. The results of copper enrichment experiment show that microwave pretreatment can effectively improve the copper enrichment of WPCB. After microwave pretreatment, copper was effectively enriched in the 4-2 and 2-1 mm particle sizes. When the microwave irradiation time was 120 s, the copper enrichment rates in the 4-2 and 2-1 mm particle sizes were 1.74 and 1.66, which increased by 0.63 and 0.32, respectively, compared to the untreated condition. Microwave pretreatment enables the effective separation of metallic copper from non-metallic components in WPCB, increasing the exposure area of copper and promoting the monomer separation of copper, thus improving the leaching and enrichment of copper.

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.

Bioleaching of Typical Electronic Waste-Printed Circuit Boards (WPCBs): A Short Review

The rapid pace of innovations and the frequency of replacement of electrical and electronic equipment has made waste printed circuit boards (WPCB) one of the fastest growing waste streams. The frequency of replacement of equipment can be caused by a limited time of proper functioning and increasing malfunctions. Resource utilization of WPCBs have become some of the most profitable companies in the recycling industry. To facilitate WPCB recycling, several advanced technologies such as pyrometallurgy, hydrometallurgy and biometallurgy have been developed. Bioleaching uses naturally occurring microorganisms and their metabolic products to recover valuable metals, which is a promising technology due to its cost-effectiveness, environmental friendliness, and sustainability. However, there is sparse comprehensive research on WPCB bioleaching. Therefore, in this work, a short review was conducted from the perspective of potential microorganisms, bioleaching mechanisms and parameter optimization. Perspectives on future research directions are also discussed.

An Old Technique with A Promising Future: Recent Advances in the Use of Electrodeposition for Metal Recovery

Although the first published works on electrodeposition dates from more than one century ago (1905), the uses of this technique in the recovery of metals are attracting an increasing interest from the scientific community in the recent years. Moreover, the intense use of metals in electronics and the necessity to assure a second life of these devices in a context of circular economy, have increased the interest of the scientific community on electrodeposition, with almost 3000 works published per year nowadays. In this review, we aim to revise the most relevant and recent publications in the application of electrodeposition for metal recovery. These contributions have been classified into four main groups of approaches: (1) treatment and reuse of wastewater; (2) use of ionic liquids; (3) use of bio-electrochemical processes (microbial fuel cells and microbial electrolysis cells) and (4) integration of electrodeposition with other processes (bioleaching, adsorption, membrane processes, etc.). This would increase the awareness about the importance of the technology and would serve as a starting point for anyone that aims to start working in the field.