Removal of heavy metal ions from aqueous solution by modified barks

Abstract

Bark, a common waste product in forestry, can be used to selectively remove cations, especially toxic heavy metals from mono or multi saline solutions. Picea, Pinus, Pseudotsuga, Larix, Tectona and Afzelia barks have been used in glass columns, after grinding and treatment with formaldehyde in acid media, to study their ability in binding toxic heavy metal ions such as Pb²⁺, Zn²⁺, Cr²⁺, Fe²⁺ and Cu²⁺. The metals are exchanged against protons on the bark substrates that presumably contain carboxyl groups in both pectin and tannin compounds.

Removal of these ions depends upon the nature of the bark used, the grain size and the predominant heavy metal ions present in the solutions. The metal ions could be stripped by addition of 0.1 ? HCl, making the substrate regeneration and its reutilization possible.

Key words:

• Water treatment
• modified barks
• heavy metals
• cation sorption

Notes

To whom correspondence should be addressed.