Anti-passivation and performance optimization of tubular electrocoagulation reactor with synchronous flotation

Electrocoagulation (EC) technology has the nature of high removal efficiency, simple operation and small sludge volume for wastewater pollutant removal. However, the electrode passivation occurs inevitably during EC process, leading to the inefficient and unstable treatment. This study examines passivation and corrosion behavior of tubular electrode using dynamic potential polarization tests. The results indicate that mitigation of electrode passivation can be achieved by adjusting pH, electrolyte and electrode shape. Then effects of current intensity, pH, flow rate and electrolyte concentration on silicon removal efficiency using with the tubular electrocoagulation are investigated. The silicon removal rate at 0.6 A, pH 9, 50 mL/min and 2.0 g/L (NaCl) achieves >97 % and treatment effect keeps stable as tubular electrode is consumed until penetrated. This indicates that alkalinity, chloride medium and tubular shape can simultaneously inhibit electrode passivation and remove pollutants efficiently by tubular EC reactor with synchronous flotation. Furthermore, removal mechanism of tubular EC is explored by SEM, FTIR, XRD, and XPS analysis. Results suggests the nanoscale boehmite flocs with high activity and easy adsorption are flocculated with simultaneously generated microbubbles, which is conductive to adsorbing, coprecipitating and floating the silicon pollutant. This work provides a facile and effective strategy for prominent anti-passivation and silicon removal performance of EC.