3D Printing of Fe<sub>27</sub>Al<sub>24</sub>Ni<sub>22</sub>Cu<sub>18</sub>Co<sub>9</sub> High-Entropy Alloy Scaffold with Direct Ink Writing for the Degradation of Methyl Red Azo Dye.

Abstract

Dyes are emerging pollutants that can be classified in various ways, with azo dyes being among the most persistent in water. These dyes contain conjugated double bonds and azo groups (R-NN-R'), making their degradation in water a significant challenge. In this study, we demonstrate that a high-entropy alloy (HEA) with the composition Fe₂₇Al₂₄Ni₂₂Cu₁₈Co₉ can be synthesized using mechanical alloying and subsequently 3D printed using material-extrusion direct ink writing. X-ray diffraction, transmission electron microscopy, and field emission scanning electron microscopy confirmed the synthesis of a new HEA with a face-centered cubic crystal structure after 40 h of mechanical alloying. The degradation properties of the 3D-printed HEA were then investigated for the azo dye known as methyl red, revealing its efficiency at 60 °C in the presence of nitric acid (pH = 1.50), with a degradation time of 28 min and an efficiency of 99%. Moreover, according to the results of high-performance liquid chromatography, we propose the degradation mechanism occurring at the surface of the Fe₂₇Al₂₄Ni₂₂Cu₁₈Co₉ HEA that effectively degrades methyl red and leading to the cleavage of the azo bond and generating two different products.