Application of mechanically alloyed MnAl particles to de-colorization of azo dyes

Abstract

The use of metallic particles has been shown to be an effective, low-cost method for degradation of many contaminating compounds. In this work, we analyze the efficiency of MnAl metallic powders for degrading azo dyes, which are the class of colorant compounds most utilized by the textile industry. We used different routes to produce the metallic particles obtaining different internal structures as characterized by X-ray diffraction and electronic microscopy. The ability to act as discoloration materials was assessed by decolorization experiments of Reactive Black 5 and Orange II azo dyes aqueous solutions. The degradation reaction of the dye molecules was monitored by ultraviolet–visible (UV) spectrophotometry showing fast kinetics, with reaction times among the shortest found in literature. The effect of the different production methods on their performance as decolorizing materials was studied as function as various parameters such as initial pH, dye concentration and temperature. The electrochemical and corrosion properties of the MnAl compounds seem to be the key factors explaining the high decolorization efficiency of these materials.