Valuable Resource Recovery from Waste Tuning Fork Crystal Resonators via an Integrated and Environmentally Friendly Technique: Pyrolysis of Organics and Chlorination Leaching–Extraction–Reduction of Gold

Abstract

Waste tuning fork crystal resonators (WTFCRs), as essential components of electronic products, are resource-rich but hazardous, demanding to be safely recycled and disposed to promote sustainable utilization of the resources and environmental protection. However, the recycling technology for WTFCTs has not attracted enough attention and has been poorly developed up to now. According to the structure characteristics of metal and nonmetal distribution in WTFCRs, this study presents an efficient and promising technology, including mechanical separation, vacuum pyrolysis, selective chlorination leaching, extraction, and reduction for recovering Au and disposing organics from WTFCRs. First, mechanical separation is done to expose organics and gold, recycling metals of 91.16% Fe and 98.75% Al simultaneously. Next, vacuum pyrolysis is proposed to destroy the organics structure so as to enrich the gold, and 84.63% organics are converted into oil as potential resource. Next, selective chlorination leaching, extraction, and reduction are employed to recover gold. The results show that sponge gold is obtained with a recovery rate of 88.61% and a purity of 98.54% via the optimal condition. This study has proposed an efficient and sustainable approach for recycling WTFCRs. It has not only alleviated the pressure of environmental pollution, but also promoted the reuse of effective energy. What is more, it lays a foundation for the sustainable utilization of electronic components and provides a reference for further research and potential applications.

Study of Gold Leaching Behavior in the Chlorination Process from Waste Printed Circuit Boards

“…Our previous study had pointed out that the ORP of ClO 3 /Cl – was higher than the standard reduction potential of Au 3+ /Au and Au + /Au, indicating that the ClO 3 /Cl – solution had the ability to oxidize gold to form the stable gold complexes AuClOH – , which was also in agreement with the gold leaching behavior analysis (Figure , , and ) and the Pourbaix diagram analysis (Figure ).…”

Environmentally Friendly Technology for Separating Gold from Waste Printed Circuit Boards: A Combination of Suspension Electrolysis and a Chlorination Process

“…The chlorination process has been proved to be efficient, cost-effective, and less polluted for extracting gold from WPCBs. − The conventional chlorination process, which was first proposed for gold extraction in 1848 and has since been widely used in gold ore dressing in the United States and Australia, usually employs chlorine as the oxidant. − The leakage risk of chlorine and the inconvenient operations greatly hindered the widespread application of the chlorination process. Our previous study developed a chlorination process for recovering gold from waste memory modules .…”

Combination of Pyrolysis and Physical Separation to Recover Copper and Tin from Waste Printed Circuit Boards

“…18 However, it has been reported that the glass fibers in WPCBs can affect the mechanical properties of the composite material, 5,19 and, moreover, during the use of the composite materials, the remaining BFRs can be released into the environment, causing serious pollution. [20][21][22] Supercritical-and subcritical-water technologies have been used to decompose the organic polymers of WPCBs into small molecules or monomers, but the application of this technology has been limited because it is costly, having high equipment requirements. 23,24 Similarly, it has been reported that the decomposition or separation of non-metallic organics in WPCBs by chemical reagents generates large amounts of wastewater.…”