Comprehensive review of floc growth and structure using electrocoagulation: Characterization, measurement, and influencing factors

Abstract Electrocoagulation (EC) has received significant attention for wastewater treatment owing to its environmental sustainability. The high removal efficiency of EC depends on flocs with large, strong structures. Flocs that aggregate with coagulants, pollutant particles, and fine electrolytic bubbles (10–50 μm) are complex and fragile during EC. However, floc growth during EC has not been thoroughly studied, and their structures have not been described in detail compared to the flocs formed by chemical coagulation (CC). Herein, the current research on floc growth during EC is comprehensively reviewed. First, the characteristics of flocs grown using EC are introduced. Second, the floc size, strength, and fractal geometry are described in detail, revealing the floc structure. Third, these structural parameter measurement methods, such as equivalent diameter, three-dimensional (3D) reconstruction, scattering, strength factor, and velocity gradient, are presented. Next, since particle aggregation is affected by the chemical conditions and hydrodynamics within the reactor, several factors, such as initial pH, current intensity, stirring pattern, electrode design, power supply, and temperature, impacting floc growth are summarized. Finally, future research directions are proposed for exploring the floc structures grown during EC and optimizing electrode materials, such as air cathodes and porous metallic anodes. This review may help reveal the removal mechanisms for diverse pollutants using EC and provide a future standard for EC cell design.