The study was focused on the investigation of the feasibility of UV/ferrioxalate system for the degradation of para-chlophenol (p-CP) as a model wastewater pollutant The influence of key process parameters was evaluated and the interactions between them were assessed using combined empirical/statistical approach applying Box-Behnken experimental design (BBD) combined with response surface methodology (RSM). BBD included three numerical and one categorical variables representing the key process parameters (initial pH, [Fe3+], [C2O42-] and type of UV irradiation). The quadratic RSM models predicting the rate of (p-CP) degradation by UV/ferrioxalate systems were developed. ANOVA was applied to evaluate the significance of models and models' components. On the bases of obtained statistical parameters (R-2, F, p), developed RSM models are characterized as highly accurate and predictive. Additionally, it was determined that all four studied process parameters strongly influenced the UV/ferrioxalate system performance. The optimal conditions for maximal degradation of p-CP in water matrix by UV-C/ferrioxalate and UV-A/ferrioxalate are determined: pH(0) = 4.4, [Fe3+] = 0.1 mM and [C2O42-] =3.4 mM; and pH(0) = 5.58. [Fe3+] = 1.38 mM and [C2O42-] = 8.16 mM. The optimal conditions strongly depended on the type of UV irradiation indicating the competitive degradation mechanisms of p-CP in water matrix including involvement of direct photolysis and radical species as well. (C) 2011 Elsevier B.V. All rights reserved.