Advanced electrochemical oxidation for the simultaneous removal of manganese and generation of permanganate oxidant

Abstract

<p>Emerging electrochemical systems, such as advanced electro-oxidation, provide a potentially powerful alternative to conventional oxidation processes which can often be unsuitable for small, remote and decentralised system applications. One electro-oxidation...</p>

Degradation of perfluorooctane sulfonatevia in situelectro-generated ferrate and permanganate oxidants in NOM-rich source waters

“…It was previously observed that no significant differences in ferrate synthesis were observed during electrolysis at the three current density conditions, despite increased generation of˙OH as the current density increased, as described elsewhere. 38,40 A mathematical model was developed to describe ferrate and permanganate synthesis under mass transport limitations, which agreed well with the experimentally derived data, yielding mass transfer coefficients between 0.24-2.8 × 10 −8 m s −1 , depending on current density and initial iron/manganese concentration. 38,40 These results demonstrated that the ratelimiting step under these low iron concentration conditions was the diffusion of Fe 2+ to the BDD electrode surface from the bulk water solution, through the Nernst diffusion layer.…”

“…38,40 A mathematical model was developed to describe ferrate and permanganate synthesis under mass transport limitations, which agreed well with the experimentally derived data, yielding mass transfer coefficients between 0.24-2.8 × 10 −8 m s −1 , depending on current density and initial iron/manganese concentration. 38,40 These results demonstrated that the ratelimiting step under these low iron concentration conditions was the diffusion of Fe 2+ to the BDD electrode surface from the bulk water solution, through the Nernst diffusion layer. After 120 minutes of electrolysis, 3.15 (±0.10), 0.90 (±0.09) and 0.40 (±0.06) μM of ferrate was synthesised under 54, 18 and 9 μM initial Fe 2+ conditions, respectively.…”

“…Previous studies have demonstrated the circumneutral electrochemical generation of ferrate 38 and permanganate 40 from low initial concentrations of Fe 2+ and Mn 2+ , respectively. Through the use of radical scavengers and cyclic voltammetry, these previous studies demonstrated that ferrate and permanganate generation was attributed to botḣ OH mediated and direct oxidation at the electrode surface.…”

“…49,50 Moreover, strategies to improve the faradaic efficiency of both ferrate and permanganate synthesis have been previously reported and determined via the aforementioned mathematical model, which include increasing reactor residence time, decreasing the interelectrode gap or increasing the anode area. 38,40 For example, if the electrochemical cell was redesigned to accommodate a 100 × 300 mm and a 5 mm inter-electrode gap, ferrate synthesis would double, in half of the time. 38…”

A Facile Method to Realize Oxygen Reduction at the Hydrogen Evolution Cathode of an Electrolytic Cell for Energy-Efficient Electrooxidation

“…Electrochemical oxidation is an important part of electrolysis and electrosynthesis, both of which use electrons as reagents and control the rate and direction of reactions by adjusting the electrode potential, thus constituting an effective means of green chemistry [ 1 , 2 , 3 , 4 , 5 , 6 ]. Electrochemical oxidation, realized through direct electron transfer and/or by reducing the oxidants generated in situ, can be used to produce a variety of inorganic and organic chemicals, including chlorine gas [ 7 ], potassium permanganate [ 8 ], ammonium persulfate [ 9 ], ozone [ 10 ], benzaldehyde [ 11 ], trifluoroacetic acid [ 12 ], p-anisaldehyde [ 11 ], etc. It is also widely used in wastewater treatment, especially in the degradation of refractory organic pollutants in water [ 13 , 14 , 15 , 16 ].…”