In this paper, the performance of UV/PS/TiO2 and UV/PI/TiO2 as hybrid AOPs for degradation of paraquat (PQ) herbicide in aqueous solution has been studied. The effect of several factors such as UV irradiation, initial oxidant concentration, nano-TiO2 (TiO2NPs) dosage, and pH on the degradation efficiency was investigated. Process optimization was performed by Central Composite Design (CCD) and response surface methodology (RSM) for 30 mgL− 1 of herbicide at 25 ˚C and 40 min. Based on the results, for UV/PS/TiO2 process a degradation efficiency of 83% was obtained in the optimum condition of initial PS concentration of 400 mgL− 1, initial TiO2NPs concentration of 150 mgL− 1, and pH = 6.3. Also for UV/PI/TiO2 process, 87% degradation efficiency was achieved in the optimum condition of initial PI concentration of 88 mgL− 1, initial TiO2NPs dosage of 125.5 mgL− 1, and pH of 7.5. Mineralization efficiency of the PQ solution by using PS and PI were about 47.5% and 57%, respectively after 80 min. Kinetic studies showed that both process follow pseudo-first-order kinetic model and their kinetic constants were 0.0299 min− 1 for PS process and 0.0604 min− 1 for PI process. Electrical energy consumption was estimated about 481.60 kWh/m3 for PS process and 238.41 kWh/m3 for PI process.