Sea Shells Used To Clean Up Heavy Metals

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Technique could save millions of lives in coastal cities in developing world

By Michael Reilly

On the banks of the Saigon River in Vietnam, researchers have just completed tests on a new way to combat water pollution that could save millions of lives in coastal cities throughout the developing world.

In factories on the outskirts of Ho Chi Minh City, Stephan Kohler of the Graz University of Technology in Austria and a team of researchers have cleansed water tainted with toxic metals like cadmium, zinc, lead and iron. And they’ve done it using nothing but one of the cheapest, most abundant material around: seashells.

Kohler’s team has found that pouring metal and acid-laden water over a bed of crushed clam or mussel shells provides an easy fix. The shells are made of aragonite, a form of calcium carbonate (CACO3) that readily swaps out its calcium atoms in favor of heavy metals, locking them into a solid form. The shells are naturally basic, too — when dissolved they have a pH of 8.3.