The Effects of Ultrasound on the Electro‐Oxidation of Sulfate Solutions at Low pH

Abstract

The electro‐oxidation of sulfate solutions is a well‐established route for the generation of powerful oxidants such as persulfate. Despite this, the effects of simultaneous ultrasound irradiation during this process has attracted little attention. Herein, we investigate the effects of a low‐intensity ultrasonic field on the generation of solution‐phase oxidants during the electro‐oxidation of sulfate solutions. Our results show that at high current densities and high sulfate concentrations, ultrasound has little effect on the Faradaic and absolute yields of solution‐phase oxidants. However, at lower current densities and sulfate concentrations, the amount of these oxidants in solution appears to decrease under ultrasonic irradiation. A mechanism explaining these results is proposed (and validated), whereby anodically‐generated sulfate and hydroxyl radicals are more effectively transported into bulk solution (where they are quenched) during sonication, whereas in the absence of an ultrasonic field these radicals combine with one another to form more persistent species (such as persulfate) that can be detected by iodometry.

Sonochemical Hydrogen Production as a Potential Interference in Light-Driven Hydrogen Evolution Catalysis

“…This is based on literature analysis of the factors that affect cavitation formation; these include ultrasonic frequency, dissolved gas, acoustic power, and temperature as well as solution volume, vessel shape and vessel material, and position of the vessel in the sonication bath. , As shown in Figure , a simple change of the Schlenk flask position from the center to the corner of the sonication bath results in significant H 2 evolution changes. We have used Margulis and Mal’tsev’s calorimetric method , as described in the literature to estimate the acoustic power that gets dissipated during sonication in both positions, observing a sharper increase in temperature during the first minutes of sonication in the flask positioned in the center compared to that in the corner. This is reflected in the estimated acoustic power values of ca .…”

“… 16 , 17 As shown in Figure 2 , a simple change of the Schlenk flask position from the center to the corner of the sonication bath results in significant H 2 evolution changes. We have used Margulis and Mal’tsev’s calorimetric method 18 , 19 as described in the literature to estimate the acoustic power that gets dissipated during sonication in both positions, observing a sharper increase in temperature during the first minutes of sonication in the flask positioned in the center compared to that in the corner. This is reflected in the estimated acoustic power values of ca .…”

Enhanced ultrasonic degradation of methylene blue using a catalyst-free dual-frequency treatment

“…To further illustrate the effect of generated ● OH and H 2 O 2 on the sonochemical degradation of methylene blue during sonication, the concentration of both were quantified at specific ultrasonic treatment intervals. In this study, the production of ● OH was quantified using dosimetry methods described in references [32] and [33] . Terephthalic acid generates terephthalate anions in an alkaline aqueous solution.…”

Thermal and Radiation Based Catalytic Activation of Persulfate Systems in the Removal of Micropollutants: A Review

“…The sonoelectro-activated persulfate oxidation process degraded aniline pollutants by sulfate radicals as a principal oxidant . Using ultrasound and electrochemical reactions improved mass transport in electrochemical reactions and acceleration and activation of electrode reactions . The synergistic effect of sonochemical and electrochemical methods in manganese sulfate as a supporting electrolyte removed 90% of TOC from real textile wastewater …”

“…107 Using ultrasound and electrochemical reactions improved mass transport in electrochemical reactions and acceleration and activation of electrode reactions. 121 The synergistic effect of sonochemical and electrochemical methods in manganese sulfate as a supporting electrolyte removed 90% of TOC from real textile wastewater. 122 From the studies conducted by J. M. Monteagudo, persulfate stimulated by US, UV-C light, and Fe 2+ ions could oxidize carbamazepine, an emerging contaminant in water.…”