Pulse electrocoagulation combined with a coagulant to remove antimony in wastewater

Pulse electrocoagulation (PEC) was used to evaluate the treatment of synthetic solutions containing antimony (Sb). The effects of electrode materials, distance between electrodes, duty ratio, current frequency, and initial pH on the removal efficiency were investigated. The removal of Sb reached 93.5% when the distance between the FeAl electrodes was 20 mm, the duty ratio was 40%, the frequency was 400 Hz, the initial pH was 4, and the operation time was 30 min. The analysis of the floc structure using scanning electron microscopy during the floc formation process revealed that the three periods can be divided into formation, fluctuation, and reaggregation. The removal rate of Sb showed a transient downward trend during formation and fluctuation. Then, polymeric aluminum chloride (PAC) was applied as a coagulant to improve the floc structure. The best strategy for PAC addition was 0.6 mg/L in 5 min and 0.3 mg/L in 18 min, and the removal effect increased to 99.9%. Importantly, this method effectively treats actual dyeing wastewater containing Sb and chemical oxygen demand (COD). These findings demonstrate that a coagulant can effectively elevate floc structure and intensity in the process of pulse electrocoagulation and also provide an innovative method for practical applications of Sb removal from wastewater.