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MIT develops “shock electrodialysis” lead removal process

Wednesday, 29 September 2021

A new energy-efficient method of removing lead from contaminated water has been developed by MIT engineers.

Six years in the making

Engineers from the Massachusetts Institute of Technology (MIT) have developed a new solution that can remove lead and other heavy-metal contaminants from water.

This new iteration of removing lead is the first method that could be applicable for treating both household and industrial water supplies. At first, it was developed for desalination but has been adapted for removing radioactive compounds from the cooling water of nuclear power plants.

Claimed to be more energy-efficient than previous systems, the development is based on initial findings made six years ago by members of the same research team.

This new approach, once ready for in-home use could provide a solution to future lead contamination events, similar to the Newark lead contamination in 2019 and the Flint crisis in 2015.

The new method was published on 22 September in Environmental Science and Technology – Water, in a paper by MIT students Huanhuan Tian, Mohammad Alkhadra, and Kameron Conforti, and professor of chemical engineering Martin Bazant.

How it works

One of the biggest challenges in lead removal is that it is normally present in very small concentrations. And as a result, hidden by other larger compounds and elements.

Mohammad Alkhadra, a student on the project at MIT said, "It’s notoriously difficult to remove toxic heavy metal that’s persistent and present in a lot of different water sources."

MIT's new approach uses shock electrodialysis, where an electric field is used to produce a shockwave inside an electrically charged porous material carrying the contaminated water.

"It’s notoriously difficult to remove toxic heavy metal that’s persistent and present in a lot of different water sources."

The shock wave propagates from one side to the other as the voltage increases, leaving behind a zone where the metal ions are depleted, and separating the feed stream into brine and a fresh stream.

According to MIT, it said the process results in a 95 per cent reduction of lead from the outgoing fresh stream.

“This makes the process much cheaper because the electrical energy that you’re putting in to do the separation is going after the high-value target, which is the lead and you’re not wasting a lot of energy removing the sodium,” added Martin Bazant, professor of chemical engineering at MIT.

Not yet ready for in-home use

In the US, Denver Water announced it will be spending $500 million over 15 years to replace lead lines that service between 64,000 to 84,000 residences.

The utility will use the 120Water platform to manage its water sampling program, including a pre-lead service line water testing at about 30,000 taps.

While the MIT process shows positive signs of being a viable lead removal system for drinking water, the new approach has only been tested at a laboratory scale.

To make it practical for in-home use will require further research and upscaling, according to Bazant, and larger-scale industrial uses will take even longer.

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