Competitive Anodic Oxidation of Methyl Paraben and Propylene Glycol: Keys to Understand the Process

Abstract

This work focuses on the competitive oxidation of two very different molecules, when they underwent electrochemical oxidation with diamond electrodes. To shed light on the mechanisms of this competitive oxidation, solutions containing methyl paraben and propylene glycol at different ratios are electrolyzed (using sulfate or chloride supporting electrolytes). Results obtained pointed out that removal of both species can be easily attained by the electrochemical process, being promoted the mineralization by the action of the sulfate derivative products and the formation of chlorinated hydro-carbons by the action of chlorine oxidants, although the mechanisms of the oxidation do not depend on the primary anion contained in the waste. The higher the concentration of species to be oxidized, the higher is the amount of intermediates and the slower is the mineralization the ratio influences. An important outcome is that there is a limit concentration in each one organic compound interferes on the degradation of a pollutant. Thus, the interference effect of PG on MeP oxidation was only observed for low MeP/PG ratios.

Coupling Ultrasound to the Electro‐Oxidation of Methyl Paraben Synthetic Wastewater: Effect of Frequency and Supporting Electrolyte

“…However, under the applied conditions, it was not possible to observe an improvement on the efficiency for the coupled process. Different characteristics for the MeP degradation in sulfate and chloride media were expected, as observed for diamond electrolysis in a previous work . The main species generated in each system are SO 4 −.…”

“…Two kinetic regions of pseudo‐first order can be observed in the case of electrolytic processes, with k 1 and k 2 as the kinetic constants for each region. This transition is explained by the nature of the generated intermediates, which seem to be easily oxidized by the present oxidant agents than the initial pollutant . No removal of TOC was achieved with SCh during the 8 hours of treatment (the negative value of kinetic constant is attributed to the dispersion of the points), but complete mineralization was attained for ECh and SECh in less than 5 hours.…”

“…Most recently, researchers have been exploring the coupling of technologies, in order to improve the efficiency of electrochemical treatments. Electro‐Fenton process,, electrolysis irradiated by UV light and electrochemistry combined to sonochemistry can be highlighted, where in most cases better results are observed for the coupled processes due to a synergistic effect. Because the coupling, more oxidant agents can be produced and, most important, it can be promoted the activation of such species, which means that highly reactive species can be formed from poorly reactive oxidants.…”

“…In previous works, the degradation of parabens by single electrochemical techniques, and by combined electroirradiated processes,, has been evaluated. According to these works, parabens can be easily removed from wastewater by electrochemical treatment, but the pollutant removal depends on the composition of the supporting media.…”

Improvement of the Electrochemical Behavior of (Sb, Sn, Cu)O Ceramic Electrodes as Electrochemical Advanced Oxidation Anodes

“…[4] The efficiency of these processes for removing recalcitrant pollutants from wastewaters has been widely reported in literature for a vast variety of recalcitrant pollutants: [5] pharmaceuticals, such as Propranolol and Diatrizoate; [6][7][8] dies, like Disperse Blue 3; [9,10] pesticides and herbicides, such as tebuthiuron and glyphosate; [11,12] and industrial compounds, like phenol, bisphenol A and EDTA. A wide range of alternative processes have been studied in this context.…”