Modified Barks as Scavengers for Heavy Metal Ions

Several barks have been found to be effective scavengers of toxic heavy metal ions, but some bleed enough color from aqueous solutions as to render them unusable. Contacting these barks with dilute formaldehyde in acid medium prevented bleeding of color into the liquid, perhaps by polymerization and precipitation of the colored compounds. Formaldehyde treatment did not diminish the capacity of the barks to remove heavy metal ions from solution. Formaldehyde treated western hemlock bark had a binding capacity of about 0.068 g Pb ? bark from a solution of 18 ppm Pb, with essentially zero bleed of color into solution.

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