Continuous and Selective Removal of Lead from Drinking Water by Shock Electrodialysis

Abstract

The affordable and effective removal of traces of toxic heavy metal ions, especially lead, from contaminated drinking water in the presence of excess sodium or other competing ions has been a long-standing goal in environmental science and engineering. Here, we demonstrate the possibility of continuous, selective, and economical removal of lead from dilute feedwater using shock electrodialysis. For models of lead-contaminated tap water, this process can remove approximately 95% of dissolved lead (to safe levels below 1 ppb), compared to 40% of sodium ions, at 60% water recovery and at an electrical energy cost of only 0.01 kW h m −3 . We are able to fit and interpret the separation data with a pore-depth-averaged electrokinetic model that reveals the mechanisms for selective separation of lead ions. This selectivity is enabled by the faster transport of lead ions from the charged porous medium to the cathode stream, as well as their larger barrier to escape to the fresh stream compared to sodium ions. The experimental and theoretical results could be used to guide the development of low-cost, point-of-use systems for continuous removal of lead from municipal water.

Selective and Chemical-Free Removal of Toxic Heavy Metal Cations from Water Using Shock Ion Extraction

“…The two devices used here (one for shock ED and the other for shock IX), shown schematically in Figure a, are based on a design previously published by our group. , The only difference between the two devices is the type of porous material used (Figure b). Both devices consist of three inlets (two to transport the electrode streams and the third to deliver contaminated feed) and four outlets (two to transport the electrode streams and two to generate depleted and enriched product streams at the splitter).…”

“…In previous work by our group, we demonstrated the ability of shock ED with a borosilicate frit to selectively separate multivalent ions in the presence of excess competing sodium, , and we proposed several possible mechanisms for this selectivity in a theoretical study . To simplify the processing and analysis of samples in this study and to isolate the role of the porous material on selectivity, we use an artificial wastewater solution in which all dissolved cations are present in approximately equal proportions, as shown in Table .…”

Interfacial resistive switching by multiphase polarization in ion-intercalation nanofilms

“…[38][39][40][41][42][43][44] For example, CP in weakly charged porous media can generate deionization shocks and be used for water treatment, in a method called shock electrodialysis. [45][46][47][48][49] In mul- To conclude, MP is an interfacial RS mechanism, limited by bulk ion diffusion, which shows multiple, non-volatile resistance states tunable by applied voltages in LTO memristors and other similar systems.…”

Interfacial Resistive Switching by Multiphase Polarization in Ion-Intercalation Nanofilms

“…Therefore, cations accumulate downstream the electric field and get depleted on the other side. This phenomenon is called concentration polarization (CP) and is important in many electrochemical systems. − In multiphase materials, CP should first occur in each phase and strong enough CP can change the phase distribution, which we refer to as multiphase polarization (MP). As shown in Figure a, a downward electric field may drive phase change at the bottom electrode first (I → II) and then at the bottom electrode later (II → III).…”