Oxalate Enhanced Organic Pollutant Removal with a UV/Fe0 System: Performance, Mechanisms, and Role of Oxalate

This study presented the efficient removal of tartrazine, a typical biorefractory dye, in a heterogeneous photochemical Fenton-like system adopting Fe 0 and oxalate (Ox) (UV/Fe 0 /Ox). Only 47.4% tartrazine could be removed within 60 min with a UV/Fe 0 system. The addition of Ox could significantly enhance the removal of tartrazine to 72.4% within only 20 min with the UV/Fe 0 /Ox system. The effects of various factors, such as the Fe 0 dose (0–0.8 g/L), Ox dose (0–2 mM), initial pH (2–6), and initial tartrazine concentration (2–30 mg/L), on the removal of tartrazine were examined. Scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and Mossbauer spectroscopy were conducted to explore the mechanism by which oxalate enhances the performance of the UV/Fe 0 system. Ox could inhibit the formation of iron (hydro)xides on the Fe 0 surface, thus guaranteeing the reactivity of Fe 0 during the reaction. Compared with Fe 2 O 3 , FeS, and Fe 3 O 4 , Fe 0 was a good heterogeneous iron catalyst for the photolysis of tartrazine with the Ox system. Compared with H 3 PO 4 , nitrilotriacetic acid, and ethylenediaminetetraacetic acid, Ox was also a good photolysis chelating agent. The UV/Fe 0 /Ox system could also maintain fast tartrazine removal after five consecutive runs without the addition of Fe 0 , indicating the good stability of Fe 0 .