Recovery of Pb (II) and removal of NO3- from aqueous solutions using integrated electrodialysis, electrolysis, and adsorption process

Electrodialysis as one of separation technology has proven high efficiency in wastewater treatment, but most of the intended studies did not take into consideration the allowable level of outlet dilute discharge. In addition, the concentrated discharge should to be treated. The disposal of Pb2+ containing solutions must comply with the established legal maximum level of 1 mg L-1. In order to achieve this target, solutions of Pb(NO3((2) were treated using a combination of electrodialysis (ED), electrolysis (EL), and adsorption on a cation exchange membrane (CEM). The Taguchi approach was utilized to identify the optimal levels of influential parameters in the ED and EL processes. The ED process reduced the Pb2+ concentration from 600 mg L-1 to 15-17 mg L-1 in the ED dilute solution, while Pb2+ was increased in the concentrated solution to 2600-3000 mg L-1. The concentrated solution was electrolyzed to yield a 90-91% recovery of Pb2+ deposits. The concentration of the dilute solution was further reduced to 1.0-1.3 mg L-1 and 1.4-1.9 mg L-1 for the outlet streams by circulation inside a second ED unit to provide membrane adsorption. The associated NO3--N concentration was reduced during ED and EL treatments through separation in the anion exchange membrane (AEM) and losses in the form of gas evolution. The outlet NO3--N concentration was below the permissible level of 50 mg L-1, and there was no need for further treatment. (C) 2011 Elsevier B.V. All rights reserved.