TG-FTIR study of pyrolysis products evolving from dyestuff production waste

Solid waste from dyestuff production is classified as ‘hazardous waste’. The thermal degradation of a dyestuff residue was studied in an inert atmosphere using Thermogravimetric Analysis coupled with Fourier Transform Infrared Analysis (TG-FTIR). A heating rate of 30 °C/min was applied, with final temperature of 950 °C. A total weight loss of 35.1 wt% was observed, and the temperature trend of evolving gaseous products, such as CO2, CO, H2O, HCN and SO2, was investigated. When heated in an inert atmosphere, the dyestuff residue starts decomposing below 200 °C, while reaching a peak rate in volatiles’ evolution around 257 °C. Sulphur and nitrogen evolve as SO2 and HCN, respectively. Also other gases and vapours, such as CO2, CH3OH and H2O are detected. At higher temperatures several compounds can still be monitored (temperature of maximum FTIR signal): methane (500 °C), carbon dioxide (650–950 °C) and carbon monoxide (900 °C). Hydrogen chloride was not detected in this experiment.