Study on Efficiency and Mechanism of Advanced Fluoride Removal by Electrocoagulation Process

Abstract

In this study, the effects of current density, electrolysis time, pH value, and sodium chloride (NaCl) electrolyte dosage on fluoride removal efficiency were systematically investigated. The results showed that the optimal operating parameters were determined as follows: current density of 10 mA/cm², electrolysis time of 30 min, pH value of 6, and NaCl dosage of 1 g/L. Under these optimal conditions, the fluoride removal efficiency could stably exceed 85%. Calcium, magnesium, and sulfate ions at an appropriate concentration of 50 mg/L significantly enhanced the fluoride removal efficiency, whereas nitrate ions exhibited a pronounced inhibitory effect. In the current density range of 5–15 mA/cm2, the advanced fluoride removal process via electrocoagulation was better fitted to the pseudo-first-order adsorption kinetics model, indicating that the adsorption process was dominated by physical adsorption. The Zeta potential showed a trend of initial increase followed by a gradual decrease. The generated flocs had an average particle size of 146.4 μm and underwent significant directional aggregation, forming a large number of irregular dendritic and star-shaped flocculent aggregates.