In this research, a new effective photocatalyst was prepared by supporting ZnO on a Todorokite (TD). This catalyst was characterized by employing scanning electron microscopy (SEM-EDX) and X-Ray Diffraction (XRD) patterns. The optical properties of the samples were measured by diffuse reflectance spectroscopy (DRS). The purpose of using the ZnO/TD as a photocatalyst was to reduction Cr(VI), which is a pollutant in water. Experiments were carried out under different operating conditions including an initial concentration of Cr(VI), photocatalyst amounts and pH values. To optimize processes and obtain a mathematical model, the researcher used a full factorial design (with three factors at three levels). The optimal conditions were determined where the amount of photocatalyst= 200 mg L-1, pH= 2 and concentration of Cr(VI)= 15 ppm. The reduction efficiency in an optimal condition was 97.73%. The experimental results showed that kinetic was the first order and k= 0.1489 min–1. تفاصيل المقالة