Lead contamination in drinking water is a major public health concern in many areas, as just a tiny concentration of lead can be highly toxic when consumed. Methods such as reverse osmosis and distillation are available to remove this heavy metal from water, but these methods also remove a lot of other things, including minerals like sodium and magnesium that can actually make drinking water healthier. Engineers at MIT have designed a new selective method for removing lead from drinking water that conserves energy and leaves other non-toxic elements alone.
The researchers applied the technique of shock electrodialysis in their new approach. This method uses an electric field to produce a shockwave inside an electrically charged, porous material that carries the contaminated water. This shock wave moves from one side of the container to the other as the voltage increases, leaving behind a zone where metal ions are depleted. The wave separates the feed stream into a brine and fresh stream, and the researchers showed that this process resulted in a 95% reduction of lead from the outgoing fresh stream. This research was published in Environmental Science and Technology – Water.
“This makes the process much cheaper because the electrical energy that you’re putting in to do the separation is really going after that high-value target, which is the lead. You’re not wasting a lot of energy removing the sodium,” said corresponding author Martin Bazant. “There’s not a lot of current involved in removing those ions, so this can be a very cost-effective way.”
While the system will need to be developed much further before it can made into a scalable, commercial product, the researchers say a system using their design could be used as an interim measure for places where lead-contaminated water is a concern, such as Flint, Michigan, or used at an industrial scale to clean water produced in mining or drilling operations so it can be safely disposed of or reused.