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

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.