Population growth, development of industry, and overall technological progress have a strong influence on the environment. The number of pollutants, including pharmaceuticals, being released into the environment every day keeps growing, and for that reason, it is necessary to find appropriate methods for the removal of these pollutants from the environment. Advanced oxidation processes have been proven to be an excellent method for removal of pharmaceuticals from the environment. They are characterized with the fast reactions with the present organics, and they produce none or very small amounts of residual waste. They are characterized by the formation of very reactive and non-selective hydroxyl radicals. Diclofenac is one of the most widely available non-steroidal anti-inflammatory drugs. It's influence on the environment, and economically efficient ways of decomposing it need to be further investigated. In this work, the influence of chemical regeneration of TiO2-FeZ photocatalyst on the decomposition of diclofenac under simulated solar irradiation was examined. Diclofenac was removed in 2 cycles. In the second cycle, chemically regenerated photocatalyst by ozone was used. Based on the results, it was concluded that after the regeneration, the photocatalyst had shown lesser activity than before the regeneration. It was also important to establish the optimal values of regeneration parameters. In order to determine those parameters, different photocatalyst plates were treated with different concentrations of ozone, and they were exposed to ozone for different treatment periods. It was established that the concentration of ozone had a significant effect on the activity of the photocatalyst. However, the duration of the exposure didn't have a large effect on the results. It was also established that during the second cycle, the greatest amount of diclofenac was removed by applying the highest concentration of ozone, and highest duration of the exposure.