Treatment of oilfield wastewater and synthesis of Na2FeO3 in a chloride ion anode oxidation system†

This study investigates the degradation of oil recovery wastewater and the generation of Na₂FeO₃ in an anodic oxidation system. The electrochemical oxidation technique with a Ti/Ru–Ir oxide-coated anode and NaCl as electrolyte was used to treat oilfield wastewater, which reduced the TOC value in the wastewater from 210 mg L⁻¹ to 115.9 mg L⁻¹. Meanwhile, active chlorine was generated in the wastewater; subsequently, ferric sulfate and sodium hydroxide were added to the electrolyzed wastewater, and the formation of Fe(III) precipitates due to the coagulation effect further reduced the TOC value in the wastewater to 25.7 mg L⁻¹ and generated blue-green substances. Analytical tests by infrared spectroscopy, ultraviolet-visible spectroscopy, X-ray diffraction (XRD), and Mössbauer spectroscopy proved that the blue-green substance was Na₂FeO₃. Na₂FeO₃ may be a more effective water treatment agent. The method used in this not only achieves waste resource recycling, but also offers the potential for large-scale production of Na₂FeO₃.