The photocatalytic reduction of hexavalent chromium (Cr(VI)) using ZnO nanorods immobilized on kaolin clay was studied. Scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) analysis demonstrated favorable immobilization of ZnO nanorods onto the kaolin. The efficiency of the UV/ZnO/kaolin process for reduction of Cr(VI) was about 88.0%, which was more effective than the UV/ZnO process (43.7%). The photocatalytic reduction of Cr(VI) was increased from 35.7 to 97.1%, with increasing photocatalyst dosage from 0.25 to 3 g/L, respectively. The reaction rate constant (k(obs)) was decreased from 0.0769 to 0.0072 l/min, and the value of electrical energy per order (EEo) was increased from 62.4 to 666.7 (kW.h/m(3)) with increasing initial Cr(VI) concentration from 10 to 50 mg/L, respectively. The photocatalytic reduction of Cr(VI) was increased from 88.3 to 98.5% in the presence of citric acid, while the presence of phenol, ethylenediaminetetraacetic acid and oxalic acid resulted in decreasing the photocatalytic reduction of Cr(VI) to 70.2, 53.2, and 36.4%, respectively.