Application of Doehlert design to the electro-Fenton treatment of Bismarck Brown Y

The removal of the synthetic dye Bismarck Brown Y (BBY) has been investigated by electro-Fenton process, using a RVC cathode to electrogenerate in situ hydrogen peroxide and regenerate ferrous ions as catalyst. The optimization of the process has been performed using Doehlert designs and the BBY removal, after 30 min, has been used as analytical response. Three variables (i.e. iron concentration, applied current and initial dye content) have been studied as factors in the optimization of BBY degradation. The experimental results showed that BBY was almost completely removed by the reaction with OH radicals generated from electrochemically assisted Fenton's reaction, and the decay kinetic always follows a pseudo-first-order reaction. The Doehlert matrix has proved to be a good design for response surface methodology because it permits to estimate the influence of the parameters of the quadratic model and to find the optimum conditions for BBY removal. In particular, the analysis of the Doehlert design indicated that ion Fe2+ concentration and applied current have a positive response on the process, and the maximum advantage is reached with the combined effect of these two parameters. Optimum BBY degradation was achieved by applying a current of 157 mA, with 0.25 mM Fe2+ and initial BBY concentration of 118.4 mg/L, and in these conditions BBY removal was 97% in 30 min and it was almost completely mineralized in 90 min.