Transforming automotive waste into value-added materials

Abstract

End-of-life automotive waste contributes significantly to current environmental problems. Hence, developing new recycling solutions that can transform waste into new raw materials able to be used by the manufacturing industry should be investigated. This research details the novel technique of using high temperature processing of a mixture of automotive waste components and the ability to reform them into value-added materials including ferrosilicon alloy, silicon carbide (SiC) and silicon carbide (SiC)/silicon nitride (Si3N4) composites. Therefore, this research has created a new resource from automotive waste; which currently disposed of in landfill. The synthesized products from automotive waste, ferrosilicon alloy, SiC and SiC/Si3N4 composites can then be used across industrial applications. The synthesis are based on the reduction at temperatures of 1550 °C, with polymer (rubber tyre/Bakelite) as a carbon source and a reducing agent, iron oxide as a precursor, and automotive glass as a silicon source. Experimental lab-scale runs were carried out using a horizontal tube furnace under inert atmospheric conditions. Synthesized ferrosilicon alloy and SiC and SiC/Si3N4 composite were confirmed by XRD, EDS, Raman, XPS and ICP results, and the morphology was analysed by SEM. Associated reaction kinetics and the mechanism of reduction were investigated by an Infrared gas analyser. Rubber tyres and Bakelite demonstrated the potential to be used as a reduction material for silica reduction. Initial volatiles generated from the plastic accelerated the rate of silica reduction, particularly with the formation of SiC through gas phase reduction reactions of silica. Waste glass was also proven to be an alternative silica resource in synthesising value-added materials and showed process of metal separation from residual materials similar to silica. This process innovation has three significant advantages: 1. It is a major step toward transforming non-metallic automotive waste into value-added materials like ferrosilicon alloy, SiC and SiC/Si3N4 composites. 2. It will reduce the cost to landfill and associated contamination issues. 3. It reduces the industry’s reliance on conventional raw materials including quartz and coke which are typically used as silicon and carbon bearing resources.