Degradation of Crystal Violet by Catalytic Wet Peroxide Oxidation (CWPO) with Mixed Mn/Cu Oxides

Abstract

The environment protection has been the starting point for the development of new technologies, which allow the control of highly toxic substances present in the effluents of various industries, whose removal is not feasible by conventional methods. In this research, mixed oxide catalysts Mn and Cu in different molar ratios were prepared from the autocombustion method and characterized by XRD, XRF, TPR-H2, and N2 adsorption–desorption isotherms. The solids were evaluated in the catalytic wet peroxide oxidation of crystal violet (CV) with mild conditions of reaction: 25 °C, normal pressure, airflow of 2 mL/min, and H2O2 0.1 M (2 mL/h). The experimental results indicated degradations of 100% of CV, conversion of the total organic carbon (TOC) of 74%, and elimination of chemical oxygen demand (COD) of 71% in 90 min of reaction. Additionally, the selectivity was monitored by CG-MS, finding that there was almost complete mineralization in a short reaction time, generating intermediate products such as carboxylic acids, alcohols, and amines that do not cause a serious risk to the environment. The Mn–Cu catalyst with molar ratios of 1:2 was the most promising catalyst, displaying a cooperative effect between the two metals, and demonstrating the importance of the redox properties for the elimination of CV dye in wastewater.

Influence of the Active Phase (Fe, Ni, and Ni–Fe) of Mixed Oxides in CWAO of Crystal Violet

“…21-11052). These results are conclusive regarding the successful synthesis of mixed oxides by the self-combustion method, generating active phases that are responsible for the oxidation processes [1,35]. The catalysts containing both Ni and Fe metals had a combination of the two phases without shifting the characteristic planes.…”

“…Here, it is necessary to use the Scherrer equation, where K is the form factor with a value of 1, λ is the wavelength that is influenced in the analysis corresponding to the λ of Cu (nm), θ is the Bragg angle, β is the mean height width (FMWH), and τ is the average grain size. For mixed oxides with Fe, the FMWH of the plane in 2θ = 35.5 • was characteristic of Fe 3 O 4 and for those with Ni, the 2θ = 43.1 • corresponded to NiO [35,36].…”

“…Regarding the metal used for these catalysts, nickel and iron have been shown to be the most efficient in carrying out oxidation reactions [1,35,36]. For this reason, they were selected in this work as constitutive elements of the active phase for CV removal.…”

Adsorption removal of methyl violet from aqueous solution by chromium phosphovanadate

“…Thus, in order to reduce the harm to human and nature, it is highly desirable to treat MV in the wastewater of printing and dyeing industry. Recently, various technologies, such as photocatalytic degradation, 10,11 decolorization, 12 bioremediation, 13 peroxide oxidation, 14 and adsorption, 15–17 have been principally applied to remove organic dyes, especially MV from wastewaters. Among these methods, adsorption has been proved to be an environment‐friendly, simple, cost‐effective, and convenient technique to treat the wastewater pollutants 18 …”

Editorial Catalysts: Special Issue on Trends in Catalytic Wet Peroxide Oxidation Processes

“…On the other hand, different innovative solutions show the current trends in the CWPO technology, mainly aimed at the development of an efficient process operated at ambient conditions, by assisting CWPO with UV light irradiation [6], solar light [7], air flow [8], or additional radical activators [9,10]; and also by operated under neutral pH with efficient production of hydroxyl radicals [11]. All these achievements, with significant impact on the operating cost of the CWPO units, were conditioned by the presence of a proper catalyst designed and tailored to provide the best performance.…”