Comparative electrochemical oxidation of the secondary effluent of petrochemical wastewater with electro-Fenton and anodic oxidation with supporting electrolytes

ABSTRACT

Electro-Fenton (EF) oxidation has high oxidation abilities and is widely used in the treatment of biorefractory and chemically refractory organic wastewater. However, it generates a large amount of iron sludge, which limits large-scale application. In this work, the comparative study of EF oxidation and anodic oxidation (AO) of the secondary effluent of petrochemical wastewater using boron doped diamond anode is carried out. In EF oxidation, the effects of Fe²⁺ concentration, pH value, and current density are investigated. The optimal conditions consist of the following: Fe²⁺ concentration of 1.5 mmol·L⁻¹, pH of 4, and current density of 10 mA·cm⁻². In AO process, the effect of adding $\mathrm{S}{\mathrm{O}}_4^{2-}$, Cl⁻, $\mathrm{N}{\mathrm{O}}_3^{-}$, $\mathrm{P}{\mathrm{O}}_4^{3-}$, and $\mathrm{C}{\mathrm{O}}_3^{2-}$ is investigated; the optimal conditions can be obtained by adding a Na₂SO₄ solution (0.075 mol·L⁻¹). When compared with AO, although EF oxidation has a higher treatment efficiency, its energy consumption is higher, and the generated effluent (with 155 g of iron sludge·m⁻³) dramatically increases the post-treatment cost, thereby limiting its large-scale application. For AO with Na₂SO₄ solution (0.075 mol·L⁻¹) and a COD removal efficiency of 70%, the corresponding treatment time is 1.34 h and the energy consumption is 2.44 kWh·m⁻³.

GRAPHICAL ABSTRACT

KEYWORDS:

• Electro-Fenton
• anodic oxidation
• boron doped diamond electrode
• petrochemical wastewater
• energy consumption

Acknowledgements

This work was supported by the Ningbo Natural Science Foundation under grant number 2018A610280; and Zhejiang Provincial Natural Science Foundation of China under grant number LQ20B070004.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Ningbo Natural Science Foundation under grant number 2018A610280; and Zhejiang Provincial Natural Science Foundation of China under grant number LQ20B070004; Natural Science Foundation of Ningbo; Natural Science Foundation of Zhejiang Province.