Degradation of methyl red at the surface of FeAlNiCuCo high-entropy alloys

High-entropy alloys (HEAs) are emerging materials with promising properties, yet their application in environmental remediation remains limited. In this study, nanostructured HEA powders with two chemical compositions (Fe₅₁Al₂₃Ni₁₁Cu₁₀Co₅ and Fe₃₄Al₂₄Ni₁₁Cu₂₀Co₁₁) were synthesized via mechanical alloying and evaluated for the degradation of methyl red, a persistent azo dye. After 40 h of high-energy milling, both HEAs formed solid solutions with a body-centered cubic (BCC) structure and a lattice parameter of 2.890 Å, confirmed by X-ray diffraction. FESEM and EDS chemical mapping verified the homogeneity of the alloys. Magnetic characterization revealed paramagnetic behavior, with saturation magnetization values of 115 emu/g for HEA1 and 68.70 emu/g for HEA2, due to their different compositions. Brunauer–Emmett–Teller analysis indicated minimal or no porosity, suggesting that degradation occurs on the alloy surface, where the HEAs act as heterogeneous catalysts. Under acidic conditions (pH 1.00) at 60 °C, HEA1 and HEA2 achieved 99 % degradation of methyl red in 4 and 5 min, respectively. HPLC-MS and HR-XPS analyses identified anthranilic acid as a degradation product and revealed the presence of functional groups on the HEA surfaces involved in the reaction. These findings highlight the potential of HEAs as efficient, fast-acting catalysts for azo dye degradation and support their broader application in environmental technologies targeting persistent pollutants.