Electrochemical oxidation of ionic liquids at highly boron doped diamond electrodes

Abstract

An electrochemical oxidation using a highly boron‐doped diamond (BDD) electrode has been tested for the treatment of solutions containing ionic liquids (ILs). The double‐sided Si/highly BDD electrodes were synthesized by microwave plasma enhanced chemical vapour deposition (MW PE CVD). Investigation of the electrode surface with scanning electron microscopy (SEM) confirmed that the synthesized layers were continuous and formed densely packed grain structure. The structure of BDD was confirmed by Raman spectra analysis. The effect of IL structure as the kind of electrolyte (Na2SO4 and NaCl) has been investigated. Electrolyses were conducted in an undivided electrolytic cell under galvanostatic conditions. The efficiency of the process has been evaluated in terms of variations of IL concentrations and chemical oxygen demand (COD) removal. Results show that pyridinium ILs were easier removed than imidazolium salts. The intermediates of electrochemical degradation of 1‐butyl‐3‐methylimidazolium salt were detected, and IL degradation pathway was proposed based on the analytical results. It was suggested that •OH radicals produced by water electrolysis attacked IL to form its derivatives with keto groups substituted to imidazolium ring. These compounds underwent ring breakage, which led to the formation of aliphatic acids that were eventually mineralized by electrolysis to CO2. Other by‐products were obtained by cutting one of the side chains substituted to N atoms in imidazolium ring. Additionally in NaCl electrolyte chloroorganic by‐products were identified.

Environmental Impact of Ionic Liquids: Recent Advances in (Eco)toxicology and (Bio)degradability

“…Therefore, it is necessary that additional research be undertaken to find other economical, stable, and efficient materials that can be used in electrolysis as electrodes or the BDD electrode may be modified to generate an electrochemical BDD system that integrates the three abovementioned important characteristics . The results of the electrochemical oxidation of ILs in the presence of the BDD electrode demonstrate that the anionic group influences the electrochemical process; for example, the chloride anion enhances the degradation of the cation of ILs. The anionic 4‐toluenesulfonate group, in contrast, competes with the imidazolium cation for the anodically produced HO .…”

Laser Reflectance Interferometry System with a 405 Nm Laser Diode for in Situ Measurements of CVD Diamond Thickness

“…Rough surface introduces the loss of coherence of the reflected light wave and increases the diffuse part of the reflectance [19]. This effect manifests itself as a drop in oscillation amplitude and the mean value in the interference signal, as presented in Fig.…”

“…The trends in roughness and refractive index were taken from our previous studies based on Raman spectroscopy and AFM/SEM measurements [19,20]. Deconvolution of Raman spectra gives the sp 3 …”

“…Moreover, they enable in situ film monitoring which is critical in diagnostics or studying of CVD process kinetics [6,14]. In optical systems, the angle of incidence of light onto the film may be fixed [10][11][12] or scanned within a specified range [15][16][17].…”

Electrochemical oxidation of sulphamerazine at boron‐doped diamond electrodes: Influence of boron concentration

“…Recently, several papers demonstrated that other biorefractory compounds such as pesticides, pharmaceuticals and dyes can be completely mineralized with the high current efficiency [16][17][18][19].…”