Effect of Intermittent Electrolysis on Electrolytic Removal of an Organic Pollutant

Abstract

In an electrolytic water treatment, electrode reactions for pollutant removal can be easily controlled by changing an electrode potential. Thereby, it has a potential to realize an efficient water treatment process. However, its coulombic efficiency, η, strongly depends on reactant concentrations near electrodes. In a continuous electrolysis, the reactant concentrations near an electrode is lower than that in the bulk due to electrolytic consumption of reactant, which gives a negative impact on the η. Therefore, an introduction of intermittent electrolysis instead of the conventional continuous one was discussed in this research, where the reactant concentration near the electrode is recovered during the electrolysis-off stage. The intermittent electrolysis of 1 mM formic acid solution revealed that the η of formic acid removal under electrolysis-on/off time cycle of 1/10 s was 3.3 times higher than that under the continuous electrolysis. A popular technique to keep the reactant concentration near the electrode is an increase in the linear velocity of solution on the electrode. However, the η at a linear velocity of 20 cm/s was only ≤ 25% higher than that at 10 cm/s. Thus, the intermittent electrolysis was very effective in enhancing the energy-efficiency of electrolytic water treatment.

Keywords

• intermittent electrolysis
• continuous electrolysis
• coulombic efficiency
• electrochemical oxidation
• formic acid