This work focused on estimating the rate constants for three ozone-based processes applied in the degradation of diclofenac. The ozonation (Oz) and its intensification with catalysis (COz) and photocatalysis (PCOz) were studied. Three mathematical models were evaluated with a genetic algorithm (GA) to find the optimal values for the kinetics constants. The Theil inequality coefficient (TIC) worked as a criterion to assess the models’ deviation. The diclofenac consumption followed a slow kinetic regime according to the Hatta number ($Ha<0.3$). However, it strongly contrasted with earlier studies. The obtained values for the volumetric rate of photon absorption (VRPA) corresponding to the PCOz process ($1.75\times {10}^{-6}$ & $6.54\times {10}^{-7} \mathrm{E}\mathrm{i}\mathrm{n}\mathrm{s}\mathrm{t}\mathrm{e}\mathrm{i}\mathrm{n} {\mathrm{L}}^{-1} \mathrm{m}\mathrm{i}{\mathrm{n}}^{-1}$) were significantly distant from the maximum ($2.59\times {10}^{-5} \mathrm{E}\mathrm{i}\mathrm{n}\mathrm{s}\mathrm{t}\mathrm{e}\mathrm{i}\mathrm{n} {\mathrm{L}}^{-1} \mathrm{m}\mathrm{i}{\mathrm{n}}^{-1}$). The computed profiles of chemical species proved that no significant amount of hydroxyl radicals was produced in the Oz, whereas the PCOz achieved the highest production rate. According to this, titanium dioxide significantly contributed to ozone decomposition, especially at low ozone doses. Although the models’ prediction described a good agreement with the experimental data ($\mathrm{T}\mathrm{I}\mathrm{C}<0.3$), the optimization algorithm was likely to have masked the rate constants as they had highly deviated from already reported values.