Abstract
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 μg/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 μg/L of hydrogen peroxide, while methylorange was better mineralized using 999 μg/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.
Highlights
The continuous growth of industry-related activities has led to the discharge of persistent and potentially toxic organic compounds into the environment
This work aims to study the feasibility of the use of a commonly encountered austenitic stainless steel (X5CrNi18-10, AISI 304) as a zero-valent iron source in the photo-Fenton degradation of methylene blue and methylorange dyes in the presence of peroxide and persulfate ions
The decolorization of both methylene blue and methylorange dyes was successfully achieved through the use of the stainless steel photocatalyst in the presence of both types of oxidant species—namely, peroxide and persulfate ions
Summary
The continuous growth of industry-related activities has led to the discharge of persistent and potentially toxic organic compounds into the environment. Organic compounds with aromatic structures, such as most dyes used in the textile and food industry, phenolic compounds, and pesticides, are relatively challenging to remove through conventional adsorption, precipitation, and chemical/biochemical oxidation processes. Most of these “conventional” processes have several drawbacks, such as poor cost efficiencies or mineralization efficiencies [1,2]. Advanced oxidation processes (AOPs) such as the Fenton process have been known to have a much more economically efficient upscaling potential and a relatively low environmental impact compared with heterogeneous semiconductor photocatalysis-based AOPs [3,4]. The electron transfer process works better in relatively acidic conditions
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