Slow-release persulfate candle (PSC)-assisted electrochemical oxidation (ECO) of 2-methylnaphthalene (2-MNA) in an undivided cell using graphite-sheet electrodes was investigated using Fe(II) as an activator. The effects of anions (Cl-, SO42-, and HCO3-) were investigated. In the PSC/ECO/Fe(II), the highest pseudo-first-order rate constant (kobs) and % removal was achieved by adding Cl- (2.723 h-1, 75.2%) followed by SO42- (1.753 h-1, 63.9 %) and HCO3- (0.047 h-1, 3.3%). Addition of Cl- played a critical role in improving the removal efficiency by inducing OH and SO4- oxidations, while SO42- reduced the efficiency due to non-radical oxidation, as elucidated by electron spin resonance (ESR). Furthermore, in the PSC/ECO/Fe(II) + Cl-, dominant radical was changed from SO4- to OH. Scavenger experiments also confirmed that Cl- and SO42- ions are controlling the oxidation reaction. Two chlorinated byproducts analyzed by LC-MS were identified in PSC/ECO/Fe(II) + Cl- system.
Keywords: 2-methylnaphthalene; Electrochemical oxidation; PS candle; Radical; Slow release.
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