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Comparison of Nitrilotriacetic Acid and [S,S]‑Ethylenediamine‑N,N′‑disuccinic Acid in UV–Fenton for the Treatment of Oil Sands Process-Affected Water at Natural pH

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journal contribution
posted on 02.09.2016, 00:00 by Ying Zhang, Nikolaus Klamerth, Pamela Chelme-Ayala, Mohamed Gamal El-Din
The application of UV–Fenton processes with two chelating agents, nitrilotriacetic acid (NTA) and [S,S]-ethylenediamine-N,N′-disuccinic acid ([S,S]-EDDS), for the treatment of oil sands process-affected water (OSPW) at natural pH was investigated. The half-wave potentials of Fe­(III/II)­NTA and Fe­(III/II)­EDDS and the UV photolysis of the complexes in Milli-Q water and OSPW were compared. Under optimum conditions, UV–NTA–Fenton exhibited higher efficiency than UV–EDDS–Fenton in the removal of acid extractable organic fraction (66.8% for the former and 50.0% for the latter) and aromatics (93.5% for the former and 74.2% for the latter). Naphthenic acids (NAs) removals in the UV–NTA–Fenton process (98.4%, 86.0%, and 81.0% for classical NAs, NAs + O (oxidized NAs with one additional oxygen atom), and NAs + 2O (oxidized NAs with two additional oxygen atoms), respectively) under the experimental conditions were much higher than those in the UV–H2O2 (88.9%, 48.7%, and 54.6%, correspondingly) and NTA–Fenton (69.6%, 35.3%, and 44.2%, correspondingly) processes. Both UV–NTA–Fenton and UV–EDDS–Fenton processes presented promoting effect on the acute toxicity of OSPW toward Vibrio fischeri. No significant change of the NTA toxicity occurred during the photolysis of Fe­(III)­NTA; however, the acute toxicity of EDDS increased as the photolysis of Fe­(III)­EDDS proceeded. NTA is a much better agent than EDDS for the application of UV–Fenton process in the treatment of OSPW.