Separating Inorganic from the Non-metal Fraction of the Processed Waste PCBS Using Heavy Liquid Separation

Electronic waste is one of the most investigated waste streams around the world due to the presence of valuable metals and hazardous chemicals. Printed circuit boards (PCB) represent a significant amount of this stream which consists of metals such as copper, silver, gold and palladium, and a non-metal fraction (NMF). The NMF represents approximately 70% by mass of the total PCB consisting of fibreglass or cellulose as reinforcing materials and epoxy, phenolic or polyester as resins. This paper presents results of the test work on the separation of inorganic and organics from the non-metal matrix using heavy liquid separation. A liquid medium of varying specific gravity was used to separate different streams from the NMF based on the density variations, and then analysed for metal content, loss on ignition and calorific value. Results showed that most of the inorganic materials reported to the density range of 1.8-2.4 g/cm3 with a low calorific value of <9 GJ/t and a mass yield of 30-40% of total NMF. The fraction with density <1.8 g/cm3 consisting mostly the organic materials had a high calorific value of >20 GJ/t and a mass yield of 60-70% of the total NMF. It also showed that the heavy metals like copper and iron were concentrated in the heaviest density fraction (>2.4 SG). An optical microscope or scanning electron microscope analysis and mechanical strength tests would be required to further test the quality and respective applications of separated products, which will be considered in the follow up research.

Author(s): Amit Kumar, Maria Holuszko and Travis Janke

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