Pharmaceuticals are mainly introduced into aquatic environment through wastewater treatment plant effluents due to ineffective removal. Diclofenac (DCF) is one of the most commonly detected pharmaceuticals in the environment. DCF is characterized by low biodegradability and toxicity to V. fischeri. DCF isn’t susceptible to direct photolysis or hydrolysis in the environment. Development and implementation of advanced oxidation processes activated by Solar irradiation may represent a potentially attractive technology for the removal of residual organic pollutants like pharmaceuticals. In this thesis DCF removal from water was investigated employing novel composite photocatalyst based on titanium dioxide and synthetic ZSM5 zeolite with cation-exchanged iron (FeZ) under Solar irradiation. TiO2 is characterized by excellent photocatalytic activity under UV-A irradiation, which is further augmented by introducing hydrogen peroxide as an oxidant and electron scavenger. FeZ showed significant adsorption capacity towards DCF at acidic pH via complexation of DCF deprotonated ethanoic functional group with surface Fe(III). Furthermore, surface Fe(III) ions under UV-A irradiation in presence of H2O2 act as heterogeneous photo-Fenton like catalyst. The novel composite (TiO2-FeZ) photocatalyst combines the photoactivities of TiO2 and FeZ, together with heterogeneous Fenton like catalyst activity and superb adsorption capacity of FeZ. DRS analysis showed a linear correlation of band gap decrease with an increase of FeZ wt%, indicating the formation of Ti-O-Fe bond that affects band gap with alteration of composite photoactivity toward visible spectrum. Efficiency of the investigated water treatment processes was evaluated through DCF removal by HPLC analysis and mineralization by TOC and the change of sum water parameters (biodegradability (BOD5/COD) and toxicity to V. fischeri). The TiO2-FeZ composite photocatalyst immobilized on glass support showed superior photocatalytic activity under simulated Solar irradiation in comparison TiO2 in acidic pH. Increasing the TiO2-FeZ photocatalyst loading showed a positive influence on process efficiency, i.e. removal and conversion of DCF, up to 4 layers of immobilized photocatalyst. Above 4 layers the loss of mechanical stability followed by photocatalyst thin film erosion was determined. DCF conversion is initiated by adsorption on the TiO2-FeZ surface, followed by hydroxylation and CN bond cleavage under illumination which was determined by MS/MS analysis for the identification and quantitation of DCF degradation by-products. Inorganic anions (Cl- and SO4 2-) negatively affect DCF adsorption due to competitive kinetics, which affects degradation pathway and efficiency. In the presence of Cl- high rate of mineralization, biodegradability and low toxicity were achieved. Potential reuse of the immobilized TiO2-FeZ photocatalyst was tested performing consecutive runs with testing efficiency of thermal and chemical reactivation of the photocatalyst. Chemical reactivation with ozonation yielded high photocatalyst activity in five consecutive runs. TiO2-FeZ photocatalyst retained superior photocatalytic activity in comparison to TiO2 or FeZ alone under simulated Solar irradiation, which implies the potential of the novel TiO2-FeZ composite photocatalyst in environmentally friendly water treatment technologies for micropollutant removal.