Ordinary Steel–Copper Galvanic Cell for Peracetic Acid Activation: A Low-Cost Catalytic Oxidation Process for Sunset Yellow FCF

A commercial steel–copper galvanic cell is introduced, to the best of our knowledge for the first time, as a simple, self-driven, and low-cost platform for peracetic acid (PAA) activation and oxidative degradation of Sunset Yellow FCF (SSY) in water. This azo dye was used as a model contaminant to elucidate the respective roles of the metallic elements and to establish the effects of PAA dosage, SSY loading, initial pH, and mixing intensity. Control experiments showed negligible SSY removal by PAA without electrodes, the connected steel–copper couple without PAA, copper/PAA, steel/PAA, and disconnected steel–copper/PAA; rapid removal occurred only when both plates were electrically connected after PAA addition. The marked enhancement is consistent with galvanically promoted iron release and iron-mediated activation of oxidants in the PAA solution. At a nominal PAA dose of 0.13 mM, approximately 95-96% of 5 mg/L SSY was removed within 5 min, followed by essentially complete degradation within 7-9 min. Doubling the SSY concentration to 10 mg/L and proportionally increasing PAA to 0.26 mM preserved comparable performance, corresponding to an empirical PAA/SSY molar ratio of approximately 11.8. Acidic conditions favored activation, although the unadjusted natural pH remained approximately 4.5 during treatment and was selected as the practical operating condition because it maintained high efficiency without pH adjustment. At 400 rpm, approximately 95% of SSY was removed within 5 min; 600 rpm offered a limited additional benefit by that time. An accompanying study using the same cell found scavenger responses inconsistent with freely diffusing HO• as the dominant oxidant; earlier Galvano–Fenton work supports iron release, but Fe(II) and individual oxidants were not tracked here. For SSY, this work demonstrates a treatment configuration that requires neither soluble iron addition, external electrical power, nor synthesized nano-catalysts.