Austenitic Stainless Steel as a Catalyst Material for Photo-Fenton Degradation of Organic Dyes

Featured Application The advanced degradation of organic pollutants aided by visible light could be carried out through the use of austenitic stainless steel (X5CrNi18-10, AISI 304) as a source for iron ions at pH values close to neutral. In this paper, a typical austenitic stainless steel was used as a catalyst in the visible photo-Fenton degradation process of two model dyes, methylene blue and methylorange, in the presence of hydrogen peroxide and potassium persulfate as free radical-generating species. The concentration intervals for both peroxide and persulfate were in the range of 333-1667 mu g/L. Very high photodecoloration efficiencies have been achieved using peroxide (>93%), while moderate ones have been achieved using persulfate (>75%) at a pH value of 6.5. For methylene blue, the maximum mineralization yield of 74.5% was achieved using 1665 mu g/L of hydrogen peroxide, while methylorange was better mineralized using 999 mu g/L of persulfate. The photodegradation of the dye occurred in two distinct steps, which were successfully modeled by the Langmuir-Hinshelwood pseudo-first-order kinetic model. Reaction rate constants k between 0.1 and 4.05 h(-1) were observed, comparable to those presented in the reference literature at lower pH values and higher concentrations of total iron from the aqueous media.