Green Synthesis of ZnO-TiO2 Nano-Photocatalyst Doped with Fe(III) Ions Using Bitter Olive Extract to Treat Textile Wastewater Containing Reactive Dyes

Textile wastewater treatment is a critical issue due to its high volume and pollution potential. This study investigates the photocatalytic degradation of red and green active dyes using a newly synthesized ZnO − TiO2 nano-photocatalyst doped with iron ions. The nano-photocatalyst is prepared through a green method using bitter olive seeds and a sol-gel method for doping iron ions. The XRD, FE-SEM, TEM, BET, and EDX characterizations show that the nano-photocatalyst is successful with a particle size of 50 nm and a specific surface area of 157.9 m2 g−1. Response surface methodology and central composite design are used to optimize the photocatalytic degradation of reactive dyes in synthetic and industrial wastewater. The optimal conditions were found to be initial dye concentration of 10 mg L−1, nano-photocatalyst dose of 0.5 mg L−1, contact time of 85 min, and pH of 6. Semi-industrial scale experiments show that the system is effective under both UV and visible radiation with removal efficiencies of more than 75% and 20%, respectively. The novel synthesis method and the high performance of the ZnO − TiO2 nano-photocatalyst doped with iron ions demonstrate the potential for practical application in the treatment of textile wastewater.