Asupp5 column

The detection of fluoride in the electrolyte was carried out after ion chromatographic separation via conductivity detection after chemical suppression of the total conductivity (881 Compact IC pro, Deutsche Metrohm GmbH). Separation was carried out at 40 °C on a 250 × 4.0 mm ASupp5 column (Deutsche Metrohm GmbH) with an eluent composition of 1 mmol L⁻¹ NaHCO₃ and 3.2 mmol L⁻¹ Na₂CO₃ and an eluent flow of 0.7 mL min⁻¹.

The concentration of ozone in the mixture flow was determined by the IN2000-L2-LC ozone analyzer (INUSA, America).
The concentrations of NO₂⁻ and NO₃⁻ were determined by ion chromatography using the 850 Professional IC Anion MCS system. A Metrosep A Supp 5 column (250 mm L × 4.0 mm ID) with integrated chip and an IC conductivity detector (Metrohm, Switzerland) were used in the determination. The injection volume of the sample was 20 μL and analyses were performed at a flow rate of 0.7 ml/min. The total NO₂⁻ conversion at 90 min (NC-T) was calculated as $$NC-T(\%)=\frac{C_{0-N{O}_2^{-}}-C_{90-N{O}_2^{-}}}{C_{0-N{O}_2^{-}}}\ast 100\%$$ the NO₂⁻ conversion via oxidation reaction (NC-OR) was calculated as: $$NC-OR(\%)=\frac{3\ast M_{N{O}_2^{-}}\ast \left(C_{90-N{O}_3^{-}}-C_{0-N{O}_3^{-}}\right)-M_{N{O}_3^{-}}\ast \left(C_{0-N{O}_2^{-}}-C_{90-N{O}_2^{-}}\right)}{2\ast C_{0-N{O}_2^{-}}\ast M_{N{O}_3^{-}}}\ast 100\%$$ the NO₂⁻ conversion via disproportionation reaction (NC-DR) was calculated as: $$NC-DR(\%)=\frac{3}{2}\ast \frac{M_{N{O}_3^{-}}\ast (C_{0-N{O}_2^{-}}-C_{90-N{O}_2^{-}})-M_{N{O}_2^{-}}\ast (C_{90-N{O}_3^{-}}-C_{0-N{O}_3^{-}})}{C_{0-N{O}_2^{-}}\ast M_{N{O}_3^{-}}}\ast 100\%$$
The proportion of disproportionation reaction (η) was calculated as: $$\mathrm{\eta }(\%)=\frac{3}{2}\ast \left[1-\frac{M_{N{O}_2^{-}}\ast (C_{90-N{O}_3^{-}}-C_{0-N{O}_3^{-}})}{M_{N{O}_3^{-}}\ast (C_{0-N{O}_2^{-}}-C_{90-N{O}_2^{-}})}\right]\ast 100\%$$ where $C_{0-N{O}_2^{-}}$ and $C_{90-N{O}_2^{-}}$ (mg/L) are the initial and the last (at 90 min) concentration of NO₂⁻, respectively; $C_{0-N{O}_3^{-}}$ and $C_{90-N{O}_3^{-}}$ (mg/L) are the initial and the last (at 90 min) concentration of NO₃⁻, respectively; $M_{N{O}_2^{-}}$ and $M_{N{O}_3^{-}}$ (mg/mmol) are the molar mass of NO₂⁻ and NO₃⁻, respectively.