Zinc removal from model wastewater by electrocoagulation: Processing, kinetics and mechanism

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2018-10, Vol.349 (C), p.358-367
• Main Authors: Chen, Xiujuan, Ren, Panpan, Li, Tao, Trembly, Jason P., Liu, Xingbo
• Format: Article
• Language: English
• Subjects: Cathodic reduction; Electrocoagulation; Kinetics; Wastewater treatment; Zinc removal
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2018.05.099

•EC process was successfully used for Zn2+ removal at various concentrations.•The influence mechanisms of main parameters on Zn2+ removal were discussed.•Zn2+ removal kinetic model highly depends on initial ion concentrations.•Electrochemical reduction facilitated Zn2+ removal at high initial concentrations. In this work, the research focused on the Zn2+ removal from the synthetic wastewater by electrocoagulation (EC) with aluminum electrodes. The effects of current density (2.1–12.5 mA/cm2), initial concentration (50–2000 mg/L), solution pH (2.9–7.4) and conductivity (0.15–14.11 mS/cm) on the removal efficiency and energy consumption were systematically investigated. It indicated that Zn2+ removal efficiency increased with the increasing of current density and residence time. With a relatively low energy consumption of 0.35 kWh/m3, all of Zn2+ (50 mg/L) was removed in 20 min EC treatment, 8.3 mA/cm2 for current density, and 5.3 for pH. With an energy consumption of 0.88 kWh/m3, all of Zn2+ (250 mg/L) were removed in 50 min. In addition, kinetic study was applied to analyze Zn2+ removal rate at different current densities and initial concentrations. Different mechanisms of Zn2+ removal were implied by comparing the results of low initial concentration (≤250 mg/L) and high one (≥500 mg/L). It was reasonable to conclude that, besides the precipitation effect of aluminum hydroxide flocculation, electrochemical reduction of Zn2+ at the cathode also contributed to Zn2+ removal, especially at a high initial concentration.