Clever chemistry could take the salt out of water softening.
Aluminum ions can strip minerals from water without the need for sodium, researchers report online October 4 in Environmental Science & Technology. The new technique could sidestep health and environmental concerns raised about the salt released by existing sodium-based water softening systems, says study coauthor Arup SenGupta.
“This is a global need that hasn’t been met,” says SenGupta, an environmental engineer at Lehigh University in Bethlehem, Pa. “We’re just changing the chemistry by adding aluminum ions, which is not something outlandish, but with that we can reduce the environmental impact.”
Hard water contains dissolved minerals such as calcium and magnesium that make it harder for soap to lather and that can leave scaly deposits inside faucets and showerheads. Many water softening systems combat these problems by passing water through a special tank containing beads covered in sodium ions, charged particles that can swap places with the calcium and magnesium, resulting in softer water.
This technique adds extra sodium to the outgoing water, though, which can raise blood pressure when used as drinking water (SN Online: 3/12/14). The system also has to be recharged periodically using a sodium-rich brine. That extra salt can end up in local groundwater and streams, prompting bans on salt-based water softeners in many areas, including many counties in California.