Study on the treatment of oily wastewater by evaluating the growth process of aggregates in an electrocoagulation reactor

Electrocoagulation has been widely studied in oily wastewater treatment because of its high demulsification efficiency and no secondary reagent is required. Oil removal largely depends on the properties of the aggregates. This study aimed to explore the growth process of aggregates and oil removal near the anode by electrocoagulation. Four factors, current density, solution temperature, initial pH value, and electrode structure, were investigated. According to the findings, the current density and temperature have the most significant influence on the growth process of aggregates. The oil removal rate depends more on the average particle size than the fractal dimension. The results showed that the current density and solution temperature have the most significant influence on the parameters of the electrocoagulation process. With increasing current density, the aggregate growth rate and average particle size entering the stable period were accelerated, and the oil removal efficiency was promoted. The growth of aggregates was retarded at high temperatures. The change in the scope of the fractal dimension was minor, ranging from 1.65 to 1.84, during the growth process of the aggregates. Foamed aluminium electrodes were beneficial for accelerating aggregate growth instead of aluminium plates, but the energy consumption was obviously increased. The relationship between the mean particle size and mean fractal dimension of aggregates is consistent with the power function. From the point of view of aggregate growth, this study forms the basis for an in-depth understanding of the demulsification mechanism.