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Nutshells discarded by the food industry could help soak up metal-based
pollutants from water. Traditionally, coal has been the source of “activated”
carbon—a substance so minutely holed that its high effective surface area
lets it absorb other chemicals. Now, researchers with the US Agricultural
Research Service have developed a process that activates the carbon in cheap
waste nutshells, and renders it more efficient than expensive coal-derived
carbon. Phosphoric acid eats into the shells and increases their surface
area.