Characterisation of gas evolution and char structural change during pyrolysis of waste CDs

The purpose of this study is to determine the characteristics of gas evolution and char structural change during pyrolysis of waste compact disc (CD). A combination of Thermogravimtetry-Fourier Transform Infrared spectroscopy (TG-FTIR) and Thermogravimtetry-Gas Chromatography/Mass Spectrometry (TG-GCMS) techniques are employed for this study. The thermal characteristics, temperature trend of evolving gas species and gas characteristics are investigated by TG-FTIR and TG-GCMS techniques. From the results, the waste CD degradation is divided into three stages (a) main gaseous compounds in first stage (<500 °C) are CO2, CO, CH4 and H2O (b) organic species including aromatic hydrocarbons, phenols and its derivatives are evolved between 500 and 600 °C. (c) Temperature above 600 °C, carbonisation and char formation occurred. The char chemical structure and physical characteristics are investigated by Scanning Electron Microscopy, FTIR spectroscopy, Raman spectroscopy and X-ray diffraction techniques. This fundamental study provides basic insight of waste CD pyrolysis and also indicates that very high valuable carbon product (90% carbon in residue) with good crystallinity is achievable.