Investigation of batch electrodialysis process for removal of lead ions from aqueous solutions

• Separation of Pb(II) ions by batch electrodialysis.
• Effect of operating parameters on Pb(II) separation by electrodialysis.
• Very good separation and energy performances under optimal conditions selected.
• Effective removal of lead ions and obtaining of non-toxic diluate.
• High concentration of metal in concentrate suitable for further recovery.

Lead is a highly polluting and toxic heavy metal, whose removal from wastewater is an important problem in specific industries. The present paper reports the feasibility of removal and concentration of Pb(II) ions from model aqueous solutions in a batch electrodialysis system, in order to comply with toxicity limit and with the regulations limit for discharging the wastewaters. For process optimization, the effects of applied potential, flow rate, temperature and initial metal concentration in feed on the separation performance, and also on the current efficiency (CE) and energy consumption (EC) were investigated. It was observed that the increasing of applied voltage, flow rate and process temperature decrease the duration of the ED process, but also decrease the cell performance in terms of CE and EC. Increasing feed concentration increases the CE to a maximum value for feed containing 500 mg Pb/L, and further decreases it. The optimum operating conditions selected are: applied potential of 10 V, flow rate and temperature of 70 L/h and 25 °C, respectively, and feed solutions containing 500–1000 mg Pb/L. Under these selected conditions very low final concentrations of diluate (1–2 mg Pb/L) are obtained, the metal is concentrated 5-fold in the concentrate compartment, and at the same time the CE is very high. The batch ED process investigated proved to be able to perform an effective removal of lead ions under advantageous energy-efficiency conditions, also leading to non-toxic wastewaters having metal concentrations very close to the limit suitable for discharges into the environment. The concentrate solution resulted after ED is adequate for further metal recovery.