Energy can be obtained from the pyrolysis and combustion of purified terephthalic acid (PTA) sludge which is produced during the treatment of PTA wastewater. In this study, the combustion and pyrolysis behaviors and kinetics of the sludge produced from the thermochemical treatment of PTA wastewater were analyzed under non-isothermal heating. It was found that reaction orders were in the range of 1–3 for oxidation/combustion. The reactions were exothermic, as indicated by the negative change in enthalpy. The phenomenon of auto gasification was observed during pyrolysis for three sludges. The analysis of the change of activation energy with the degree of conversion showed that several parallel reactions occurred at the beginning of the sludge decomposition during air combustion. The value of activation energy for CuSO4, FeCl3 and FeCl3 + CPAA sludge was 99.5 kJ/mol, 109 kJ/mol and 118.7 kJ/mol, respectively, for pyrolysis and 116.3 kJ/mol, 68.8 kJ/mol, and 127.9 kJ/mol, respectively, for combustion. These sludges are promising for energy recovery because they have a high net calorific value (NCV) and a high gross calorific value (GCV). The GCV was 22.4 MJ/kg, 19.8 MJ/kg, and 28.4 MJ/kg for CuSO4, FeCl3, and FeCl3 with CPAA, respectively and the NCV was 22.3 MJ/kg, 18.6 MJ/kg, and 27.3 MJ/kg for CuSO4, FeCl3, and FeCl3 with CPAA, respectively. The artificial neural network was used to validate the experimental results. The correlation coefficient between the expected and experimental results were 0.9945, 0.9980 and 0.9980 for CuSO4, FeCl3 and FeCl3 +CPAA sludge for pyrolysis, respectively and 0.9989, 0.9963 and 0.9968 for CuSO4, FeCl3 and FeCl3 +CPAA sludge for combustion, respectively. The developed ANN model successfully predicts the combustion and pyrolytic process for petrochemical sludge under specified conditions. Display omitted •Auto-gasification was found to play an important role in the pyrolysis of sludge.•Kinetics was analyzed through both the global kinetic approach and the isoconversion approach.•Pyrolysis and oxidation of the sludges indicate the exothermic nature of the reactions.•PTA Wastewater sludge exhibited high gross calorific value and net calorific value.•Developed ANN model showed significant positive relationship between the model predictions and the experimental data.