Production of Mg-based alloys: highly efficient and green removal of azo dyes

Since dyeing wastewaters cause serious environmental problems effecting human health, it must be treated before being discharge into the environment. In this work, Mg–Ni–Y–La alloy with the nominal compositions of Mg₆₅Ni₁₈Y₁₅La₂ was successfully synthesized by mechanical alloying (MA) method. The microstructural properties, morphological evaluation and thermal behavior of the powders at the different stages of milling time, were examined by the combination of X-ray diffraction (XRD), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC) and the crystallite sizes of the powders were estimated by the broadening of XRD peaks according to the Debye Scherrer formula. The XRD results showed that Ni₃Y, La₂Mg₁₇, and Mg₂Ni phases were formed with the average crystallite size of 9.3 nm after 100 h milling time. The exothermic peak at about 487 °C in the DSC curve of 5 h milled powders was observed. The obtained Mg₆₅Ni₁₈Y₁₅La₂ alloy was used as a photocatalyst in the color and chemical oxygen demand (COD) removal from the simulated wastewater containing 50 mg l⁻¹ Methyl Orange. In order to improve the applicability in wastewater treatment system, the decolorization efficiencies of the dyeing solution consisting of Methyl Orange, Rhodamine B, and Methylene Blue dyes were also examined using by the same experimental methods and materials. The Mg₆₅Ni₁₈Y₁₅La₂ alloy powders showed the highest catalytic activity with its ability by 92% color and 98% COD removal efficiencies within 3 min in wastewater containing 50 mg l⁻¹ Methyl Orange. In addition, 92, 79, and 77% removal efficiencies were achieved for Methyl Orange, Rhodamine B, and Methylene Blue, respectively. The Mg₆₅Ni₁₈Y₁₅La₂ alloy is remarkable for demonstrating the capability of simultaneously degradation of anionic and cationic dyes. Thus, the ability of Mg₆₅Ni₁₈Y₁₅La₂ alloy to treat simulated textile wastewater samples and simultaneously remove of dyes was successfully investigated and it provided insight into overcoming the limitations of existing photocatalysts in simultaneous dye degradation and real wastewater treatment. So it is valuable and promising for the treatment of wastewaters generated by textile dyeing manufacturing in future.