Synthesis of TiO2/Zn-Al layered double hydroxide-based hybrid photocatalyst and determination of its photocatalytic activity on dye degradation

In this study, a hybrid photocatalyst containing TiO₂/Zn–Al Layered Double Hydroxide (LDH) was synthesized using the sol–gel method and subsequently calcined at 430 °C. The obtained material was characterized by XRD, SEM, SEM–EDX, DRS, FTIR, BET surface area and zeta potential analyses. The photocatalytic activity of the composite catalyst was evaluated for the degradation of Reactive Black 5 (RB5), a reactive dye commonly used in the textile industry. For this purpose, model RB5 solutions were treated in a solar box unit under visible light irradiation, and the effects of various parameters such as irradiation time, catalyst dosage, dye concentration, pH, and matrix composition were investigated to optimize the photocatalytic degradation conditions. In a dye solution containing 10 mg/L of RB5, 0.75 wt% of the dispersed photocatalyst degraded approximately 98% of the dye after 120 minutes of irradiation under visible light (670 W/m²) at pH 5. However, when RB5 solutions of different concentrations were prepared using the effluent water collected from a textile dyeing plant, the photocatalytic degradation efficiency decreased significantly. This reduction indicates that other ions and molecules present in the industrial effluent negatively affect the photocatalytic degradation process. Under optimal conditions, the photocatalytic degradation of RB5 was found to follow a pseudo-first-order kinetic model according to the Langmuir–Hinshelwood (L–H) mechanism.