In this research, degradation of P-Nitrophenol (PNP) as a model nitro-aromatic compound was carried out by photocatalytic process using magnetic Titania nano particles (MTNPs). The recyclable MTNPs were synthesized with average diameter of 22 nm and a narrow size distribution. The process was modeled and optimized by a second order reduced polynomial model. Based on the model prediction, the process can be degraded PNP up to 90% under the optimum conditions of the initial pH =4, [PNP]= 15 mg L-1, [MTNPs] = 85 mg L-1, and T = 25 degrees C. PNP mineralization was obtained 69%, at the optimum condition after 120 min of the process. The process kinetic was well fitted by pseudo first order kinetic model and electrical energy consumption of the process was obtained about 177.8 kWh/m(3). Furthermore, the effect of sodium sulfite, sodium sulfate and sodium nitrite on the photocatalytic degradation process was assessed. The results showed that sulfite or sulfate ions decrease and nitrite ions increase the process efficiency. Also, a sample of redwater as a nitro-aromatic effluent was treated. (C) 2016 Elsevier B.V. All rights reserved.