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Modified Graphite with Tin Oxide as a Promising Electrode for Reduction of Organic Pollutants from Wastewater by Sonoelectrochemical Oxidation

Nsaif Hind Jabbar, Majeed Najwa Saber

Ecological Engineering & Environmental Technology

2024

Vol. 25, iss. 1

307--320

Most of the studies on tin oxide coatings as electrode materials were conducted on titanium; in this study, the aim was to create pure tin oxide (SnO2) films on graphite substrate, which is more prevalent than titanium. There is a lack in investigation the effect of SnCl2 and HNO3 concentrations on the prepared SnO2 electrode; therefore, the aim of this work was to study these effects precisely. Also, no previous study investigated the removal of phenol sonoelectrochemically by a SnO2 electrode, which would be accomplished in the present work. The tin dioxide electrode was produced by cathodic electrodeposition using a SnCl2·2H2O solution in the presence of HNO3 and NaNO3 on a graphite plate substrate. The impact of various operating parameters (current density – CD, HNO3 concentration, and SnCl2·2H2O concentration) on the morphology and structure of the SnO2 deposit layer was thoroughly investigated. The physical structures of the SnO2 film were determined by X‐ray diffraction (XRD), surface morphology was characterized using field-emission scanning electron microscopy (SEM), and chemical composition was analyzed using energy-dispersive X-ray spectroscopy (EDX). In a batch reactor, the sonoelectrochemical oxidation of phenol was tested to determine the performance of the best SnO2 electrodes for phenol degradation and any organic byproducts. It was discovered that 10 mA/cm2 , 50 mM of SnCL2·2H2O, and 250 mM of HNO3 were the optimum conditions to prepare SnO2 electrodes, which produced the smallest crystal size, with no appeared cracks, and gave the best phenol removal. The best prepared electrode was tested in the sonoelectrochemical oxidation of phenol with two different electrolytes and different CD, and the results showed that the phenol removal was 76.87% and 64.68% when using NaCl and Na2SO4, respectively, as well as was 63.39, 76.87, and 100% for CD at 10, 25, and 40 mA/cm2, respectively.

Sonoelektrochemia : wpływ ultradźwięków na przebieg procesów elektrodowych oraz ich praktyczne wykorzystanie w elektrochemii

Winkler K., Wysocka M.

Wiadomości Chemiczne

2002

[Z] 56, 11-12

895-930

Sonoelectrochemistry is the field of the research dealing with the influence of power ultrasound on electrochemical processes. The dominant effect of the ultrasound in electrochemical systems is the enhancement of mass transport by macrostreaming due to the propagation of an acoustic wave and microstreaming related to the acoustic cavitation phenomena and microjetts formation on the electrode surface. These effects are responsible for large enhancement of the current and significant modification of voltammograms recorded at stationary electrodes. In the presence of power ultrasounds voltammograms show steady-state sigmoidal shape with an oscillatory behavior. A simple planar diffusion layer model may be employed to analyze the current data. Ultrasound can also influence physical and chemical properties of electrode surface. Cavitation induced by ultrasound as well as shear forces can cause cleaning of the electrode surface and prevent adsorption and precipitation processes. Sonication can activate the electrode surface, too. High power ultrasound can also change the morphology of the electrode surface. Ultrasounds are succesfuly applied to a wide range of electrochemical technologies. There are frequently used in electrometalurgy for metal coating, electropolishing, electromachining, and electrochemical etching. The use of ultrasound allow eleiminate highly toxic compounds from the electroplating procedures. Ultrasound can significantly improve electrochemical synthesis processes. These improvements include enhancment diffusion and trerefore increase of yields and current efficiency, suppresed electrode fouling and alteration of reaction mechanism, and product selectivity control. Polymer films formed at the electrode surface in sonicated solution show better morrphology and mechanic properties. High rate of mass transfer under sonoelectrochemical conditions allows kinetic study of fast heterogeneous charge transfer processes and chemical steps coupled with rlectron transfer reaction. The application of ultrasound to analytical procedure can provide numerous benefits of which enhanced mass transport and in situ cleaning of the electrode are the most important. Sonoelectrochemistry analytical methods exhibit high sensitivity and good reproducibility. There are also less time consuming procedures comparison to conventional electroanalytical methods prformed under silent conditions. Ultrasound allows the formation of emmulsions in heterogeneous systems of immiscible organic and aqueous solvents without stabilizing agents simply by mechanical forces atributed to cavitation processes which arise at the liquid/liquid phase boundaries. Sonoelectrochemical is also used in nanotechnology for formation of nano-size metalic and non-metalic particles. The electrochemical study of electrode reactions of organic reagents in polar water solution can be carried out in these systems. Emulsions stabilized by ultrasound can be also used in quantitative analysis of water insoluble samples.