Anodic oxidation produces active chlorine to treat oilfield wastewater and prepare ferrate(VI)

Abstract

This report describes an electrochemical method that encompasses the formation of active chlorine species and the synthesis of ferrate(Ⅵ). This process applies anodic oxidation to degrade oilfield wastewater pollutants, while simultaneously generating active chlorine from NaCl in the electrolyte. Ferrate(Ⅵ) is produced by utilizing the oxidizing properties of the active chlorine species in the presence of ferric ions, which are added after the electrolysis. The advantages of this method include (i) the relatively short electrolysis time required, (ii) the use of low current density conditions to produce active chlorine substances, and (iii) the formation of ferric hydroxide colloids, which can enhance the degradation of petroleum wastewater. The residual active chlorine in the system is used to synthesize ferrate(Ⅵ), which can help recycle waste. Specifically, the system achieves 89.4 % TOC reduction after 50 min of electrolysis with a current intensity of 1 A. Under the optimal dosage conditions (NaOH = 10 g·L−1, Fe(NO3)3 = 10 g·L−1), the concentration of ferrate(Ⅵ) produced after three hours of reaction is 1.08 mmol·L−1. The strategy described in this article demonstrates high efficiency towards removing organic pollutants in oilfield wastewater, and provides a waste resource recycling strategy.