## 1 Introduction  
The textile industry produces a significant amount of dye effluent, which contains highly toxic metal complex dyes [1]. As materials can absorb only 20-80% of the dye from dye mixtures, depending on their limited absorption capacity, approximately 10-15% of the dyes are released into effluents [2, 3]. With the increasing use of synthetic chemical dyes over the past few years, a considerable amount of dye-containing industrial wastewater effluent is discharged into aquatic and soil environments [4, 5]. Azo dyes, containing one or more azo groups (-N=N-) in their chemical structure, account for 50-70% of the synthetic dyes that are used in textiles, papers, food, cosmetics, and pharmaceuticals [6, 7]. Given their abundant structural diversity, high molar extinction coefficient, sensitivity to light, and wetness, azo dyes are toxic and mutagenic; moreover, they lead to the discoloration of natural water. Several approaches have been used for the removal of azo dyes from industrial wastewater. A combination of aerobic and anaerobic processes is carried out on dye effluent because it is cheap and easy to process; however, it is insufficient to remove hazardous particles from dye wastewater [8] Biological processes, including adsorption by microbial biomass and microbial degradation [9] are not effective for all dyes because of the stability, high water solubility, and high molecular weight of azo compounds [10]; furthermore, they tend to generate toxic byproducts [11, 12]. In particular, azo dyes cannot be effectively treated by conventional biological processes because they are chemically stable [13]. Adsorption exhibits excellent removal efficiency, but the cost of adsorbents is significant. Coagulation-flocculation is widely used, but it leads to the generation of sulfur and vat dye effluents. In addition, it produces a considerable amount of sludge. Ion exchange shows good dye removal efficiency, but is limited to certain dyes. Membrane filtration is applied for water recovery; however, the membrane is easily fouled and the initial investment is high [14]. Chemical oxidation, including ozonation, is also applied for chemical dye removal, but it produces toxic byproducts and has a short half-life [15; 16; 17]. Wastewater containing azo dyes reduces the amount of light that can penetrate aquatic environments. Moreover, it produces different amines under anaerobic conditions, resulting in serious environmental problems. A recent study reported that H\({}_{2}\)O\({}_{2}\) assisted photoelectrocatalysis for the decolorization and biodegradation of pharmaceutical wastewater [18]. Potassium ferrite (K\({}_{2}\)FeO\({}_{4}\)), which is an iron (VI) derivative, is a powerful oxidant over a wide pH range; its standard reduction potential varies from +2.2 V to +0.7 V in acidic and basic conditions, respectively [19; 20; 21]. As compared to chlorine, chlorine dioxide, hydrogen peroxide, and ozone, K\({}_{2}\)FeO\({}_{4}\) works as a strong oxidant for water and wastewater treatment in acidic solutions. The ferrite ion (FeO\({}_{4}\)\({}^{2-}\)) reduces rapidly and exothermally to Fe (III) and oxygen under strongly acidic conditions. Meanwhile, in strong alkali solutions, it tends to be stable and has a low reduction rate at pH 9.4-9.7. Its decomposition rate dramatically decreases as the pH increases from 7.1 to 11.9 [22]. In aqueous solution, the ferrite ion (FeO\({}_{4}\)\({}^{2-}\)) is a monomer with a tetrahedral structure consisting of a high degree of four covalent character equivalent Fe-O bonds [23]. It is widely used in water treatment because it is stable for up to one year and is easy to prepare. Furthermore, it is stable in organic solvents, but highly soluble in water. Compared to other oxidants, K\({}_{2}\)FeO\({}_{4}\) generates non-toxic products with relatively low amounts of disinfection byproducts (DBPs) [21].