Anodic oxidation to produce persulfate for treatment of oilfield wastewater and synthesis of Fe(vi)

Abstract

To improve the effect of oilfield wastewater treatment and achieve the purpose of resource utilization of waste, in this study, an electrochemical method including an anodic oxidation-derived persulfate system for the treatment of oilfield wastewater and preparation of ferrate(VI) is reported. In an anodic oxidation system in which Na₂SO₄ is used as the electrolyte, the formation reaction of persulfate and the degradation reaction of organic pollutants co-occurred. After the electrolysis, NaOH and Fe₂(SO₄)₃ were added to the system, and the newly generated Fe(OH)₃ can further remove TOC from organic wastewater. Ferrate(VI) was prepared by oxidizing Fe(OH)₃, using the oxidative properties of the reactive radicals produced by the activation of persulfate. This method used persulfate instead of hypochlorite, which was traditionally used to prepare ferrate(VI) and to prevent the pollution of air and the environment. Moreover, ferrate(VI) is synthesized while degrading oilfield wastewater, which achieves the recycling of resources. The results showed that the TOC removal of wastewater treated by this process reached 88.9%, which could meet the discharge requirements. In addition, the ferrate(VI) concentration was 0.98 mmol L⁻¹ after 3 h of reaction under suitable dosing conditions. This study showed promising results in the treatment of organic pollutants in oilfield wastewater and can provide some references for research in this area.