A Relatively Low-Cost, Energy-Efficient Approach to Treating Water Contaminated with Heavy Metals
upstart writes:
The new system is the latest in a series of applications based on initial findings six years ago by members of the same research team, initially developed for desalination of seawater or brackish water, and later adapted for removing radioactive compounds from the cooling water of nuclear power plants. The new version is the first such method that might be applicable for treating household water supplies, as well as industrial uses.
[...] The biggest challenge in trying to remove lead is that it is generally present in such tiny concentrations, vastly exceeded by other elements or compounds. For example, sodium is typically present in drinking water at a concentration of tens of parts per million, whereas lead can be highly toxic at just a few parts per billion. Most existing processes, such as reverse osmosis or distillation, remove everything at once, Alkhadra explains. This not only takes much more energy than would be needed for a selective removal, but it's counterproductive since small amounts of elements such as sodium and magnesium are actually essential for healthy drinking water.
The new approach uses a process called shock electrodialysis, in which an electric field is used to produce a shockwave inside an electrically charged porous material carrying the contaminated water. 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 a brine and a fresh stream. The process results in a 95 percent reduction of lead from the outgoing fresh stream.
[...] The process still has its limitations, as it has only been demonstrated at small laboratory scale and at quite slow flow rates. Scaling up the process to make it practical for in-home use will require further research, and larger-scale industrial uses will take even longer.
Journal Reference:
Huanhuan Tian, Mohammad A. Alkhadra, Kameron M. Conforti, et al. Continuous and Selective Removal of Lead from Drinking Water by Shock Electrodialysis, ACS ES&T Water (DOI: 10.1021/acsestwater.1c00234)
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