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Applying the isoconversional method to data obtained from thermogravimetric analysis (TGA) can provide vital kinetic information. In this work, the thermal decomposition and oxidation of the antidiabetic drug glimepiride is analyzed in the presence of N2 and O2. The study was done with and without metal oxide catalysts to explore their potential application in solid wastewater upgrading. The analysis was conducted using thermogravimetric analysis. The isoconversional methods of Kissinger–Akahira–Sunose and Friedman were used to estimate the effective activation energies as a function of the extent of conversion (α). Density functional calculations were used to estimate the bond dissociation energies in glimepiride. The Ea values obtained from the Friedman method and the DFT calculations indicate an initial S–N bond breaking in glimepiride. The pre-exponential factor (A) and the kinetic triplet (ΔH‡, ΔS‡, and ΔG‡) are also discussed. When glimepiride oxidation was studied in the presence of the metal oxides, the catalyst activity was found to follow the order $${\text{VO}}_{{2}} > {\text{ CuO }} > {\text{ MnO}}_{{2}} > {\text{ Al}}_{{2}} {\text{O}}_{{3}} > {\text{ TiO}}_{{2}}$$ VO 2 > CuO > MnO 2 > Al 2 O 3 > TiO 2 .

This work is a first attempt to understand the mechanism of metformin thermal decomposition under inert conditions. Thermal gravimetric analysis coupled with mass spectrometry was used to probe the thermal degradation reactions. Density functional theory and second-order perturbation (MP2) theoretical calculations were used to construct a reaction mechanism for metformin decomposition. It was evident that the reactions are initiated via formation of methyl radicals, and ammonia via 1.3-H shift, followed by a series of different secondary reaction pathways. The formation of cyanamide, dimethylamine and HCN were among the main secondary products. The proposed mechanism is important for future treatment of wastewater containing metformin and similar drugs formulations, and their possible conversion to useful commodities.