Slow-release persulfate candle-assisted electrochemical oxidation of 2-methylnaphthalene: Effects of chloride, sulfate, and bicarbonate

[Display omitted] •Slow-release PSC-assisted ECO of 2-MNA was investigated.•Pseudo-first-order rate constant increased with Cl− but decreased with and HCO3−.•PSC/ECO + Cl− exhibited radical oxidation and PSC/ECO + SO42− followed non-radical oxidation.•Chlorinated byproducts in the presence of Cl− were identified by LC–MS. 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.