Anode passivation mitigation by homogenizing current density distribution in electrocoagulation

Area of Science:

• Electrochemistry
• Water Treatment Technologies
• Materials Science

Background:

• Electrode passivation is a major challenge in electrocoagulation (EC) water treatment, hindering process efficiency.
• Limited research exists on understanding and mitigating the evolution of anode passivation.
• Anode passivation affects the long-term performance and cost-effectiveness of EC systems.

Purpose of the Study:

• To investigate the role of current density (CD) distribution homogenization in mitigating anode passivation during EC.
• To quantify the impact of electrode area on CD distribution and passivation.
• To propose a practical electrode design strategy for reducing anode passivation.

Main Methods:

• Experimental manipulation of aluminum anode area in an EC setup.
• Measurement and analysis of current density distribution, including edge and center ratios.
• Depth profiling of passivated anodes to assess passivation layer thickness and inhomogeneity.
• Evaluation of energy consumption and pollutant removal efficiency.

Main Results:

• Homogenization of CD distribution was identified as critical for alleviating anode passivation.
• Decreasing electrode area from 8 cm² to 2 cm² increased CD homogenization by 24.0% and reduced passivation by 24.3%.
• Depth profiles confirmed inhomogeneous passivation, with thicker layers at electrode edges due to high CD from the 'edge effect'.

Conclusions:

• Splitting electrodes into smaller units is a facile strategy to homogenize CD distribution and mitigate passivation.
• This electrode design can reduce energy consumption by 21.8% without compromising removal efficiency.
• The study offers valuable insights into anode passivation mechanisms and practical electrode design for EC water treatment.