Particle removal performance and its kinetic behavior during oxide-CMP wastewater treatment by electrocoagulation

• We investigate CMP wastewater treatment using electrocoagulation.
• pH, aeration, and current density greatly affect the particle removal efficiency.
• Particle removal efficiency of 99% is achieved at 5.9 mA/cm2 in 10 mins.
• We propose a kinetic reaction model to describe the particle removal behavior.
• The reaction orders for particle and ferrous ion concentrations are determined.

The treatment of chemical mechanical polishing (CMP) wastewater was investigated using the electrocoagulation (EC) method with a focus on its particle removal efficiency and kinetic behavior. The sacrificial electrode for use in the EC treatment was made of Fe, in which the supporting electrolytes of Fe2+ can be electrolytically generated. Several significant factors including pH, aeration and current density of the treatment system were evaluated. The experimental results showed that the pH controlled at 5 ∼ 7 after the EC treatment is preferable and applying aeration during the EC is effective for enhancing the particle removal efficiency. In this system, the particle removal efficiency was found to achieve 99% by treating the wastewater at a current density 5.9 mA/cm2 in 10 mins. Furthermore, a kinetic reaction model considering the charge neutralization and particle coagulation was proposed to describe the particle removal mechanism. The calculated result based on the model showed good agreement with the experimental data. It was also found that the reaction orders for the particle and Fe2+ concentration terms in the proposed particle removal rate equation are 2 and 4, respectively.

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