This study aims to develop a process based on the UV irradiation of TiO2 and carboxyl anion (UTC) to create reducer agents for photo-precipitation of the chromate. To perform the RSM-based optimization, a central composite design (CCD) function was employed for modeling and optimization. Based on this model, the stationary points for catalyst dosage, formate dosage, initial Cr-VI concentration and time were 5.34 mg L-1, 3.34 mg L-1, 123.15 mg L-1, and 6.99 min, respectively. Moreover, the maximum reduction performance was reached as 98.44 and 97.22% at the modeling and experimental conditions. Therefore, the weight ratio of 5:2:120 (TiO2: FM: Cr), with 82.4% reduction of Cr and without formate remaining was chosen as the optimal and practical point. Nature of the Cr and the type of sludge created at different weight ratio in UTC process recognizable with different colors and FTIR spectra. The red and green color in sludge are due to the presence of CrO3 and Cr(OH)(3) respectively, and the brown or black sludge are due to the presence of both Substances. Finally, the computational results shown with concentration increased from 33.75 to 120 mg L-1 rate constant (k(obs)) decreases from 0.4257 to 0.1313 min(-1) while photoreaction rate (r(obs)) increases from 14.36 to 15.75 mg L-1 min(-1). Also, during Cr concentration increased from 33.75 to 120, electrical energy per order increase from 2.29 to 7.16 to 7.47-9.84 kwh. m(-3). (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.