Synthesis, characterization, and azo dye degradation performance of mechanically alloyed Mg65Cu20Y13La2 nanocrystalline powders

Abstract

This research describes the synthesis of the multicomponent Mg65Cu20Y13La2 alloy by mechanical alloying (MA) to investigate the influence of milling times on the microstructure of alloy and degradation performance of methyl orange. The structural evolution of this alloy was investigated by using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive spectrometry (EDX) techniques. The thermal behavior of the alloys was investigated by differential scanning calorimetry (DSC). The crystallite size of the Mg65Cu20Y13La2 alloys was calculated using the Debye Scherrer equation with broadening of the XRD peaks. The methyl orange degradation efficiencies of the Mg65Cu20Y13La2 alloys were evaluated by using ultraviolet–visible (UV–Vis) spectroscopy, Fourier-transform infrared spectroscopy (FT-IR), and gas chromatography–mass spectrometry (GC–MS) techniques. The XRD and SEM results showed that the microstructure of the powders changed during MA. After 10 h milling time, three intermetallic phases were obtained as Mg2Cu2La, Mg24Y5, and Mg2Cu. The results also showed that a solid solution phase, α-Mg(Cu, Y, La), with an average crystallite size 21 nm was formed after 100 h milling time. DSC trace of the Mg65Cu20Y13La2 powders showed two exothermic peaks for the 10 h milling time, while it did not show any peaks for the 100 h milling time. Photocatalytic decomposition of the methyl orange solution by the Mg65Cu20Y13La2 alloy was evaluated by UV–Vis spectra with a decrease in absorbance at a wavelength of 465 nm. After a 20 min exposure, UV–Vis, FT-IR, and GC–MS analysis showed that the methyl orange samples were almost completely degradation by using the Mg65Cu20Y13La2 powders. The Mg65Cu20Y13La2 alloy exhibits a good reusability of 92% by the four cycle and a high efficiency was achieved in all the pH values in the range of 5–9. The results prove that the Mg65Cu20Y13La2 alloy is an efficient and promising material for dyeing wastewater treatment.