Ferrate(VI) green oxidant: electrochemical generation, self-decomposition, and application for reactive red 195 azo dye treatment

BACKGROUND

Ferrate(VI), an environmentally friendly oxidant, has recently emerged as one of the most promising chemicals for water and wastewater treatment due to its versatile application as an oxidant, coagulant, and disinfectant. In this paper, the factors affecting the electrosynthesis process of ferrate using ductile iron anode were studied. Besides, the obtained ferrate was used to remove reactive red 195 (RR195).

RESULTS

The optimal ferrate electrochemical synthesis conditions were determined, including 14 mol L⁻¹ NaOH electrolyte solution, a current density of 40 mA cm⁻², and electrolysis time of approximately 5–6 h. Furthermore, the kinetics of the ferrate's self-decomposition reaction was also studied at different temperatures. The decomposition process of ferrate in a 14 mol L⁻¹ NaOH environment followed second-order kinetics, with reaction rate constants of 4.70 × 10⁻⁹, 7.31 × 10⁻⁸, 1.95 × 10⁻⁷, and 4.70 × 10⁻⁷ (L mol⁻¹ s⁻¹) at temperatures of 4, 10, 20, and 30 °C, respectively. RR195 treatment efficiency by ferrate reached 96.3% in a short time of 3 min at pH 3 with a ferrate/RR195 molar ratio of 30/1.

CONCLUSION

This study identified the optimal conditions for the electrochemical synthesis of ferrate using a ductile iron anode. Ferrate was stable at a low temperature of 4 °C, so unused ferrate needs to be stored at low temperatures to avoid decomposition of ferrate. The ferrate green oxidant demonstrated high efficiency in the treatment of RR195 in a short time. © 2024 Society of Chemical Industry (SCI).