industrial crops and products 29 ( 2 0 0 9 ) 336–340 available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/indcrop Metal adsorption of tannin based rigid foams G. Tondi a,* , C.W. Oo b , A. Pizzi a , A. Trosa c , M.F. Thevenon d a ENSTIB, University of Nancy, 27 rue du Merle Blanc, BP 1041, F-88051 Epinal, France b Universiti Sains Malaysia, School of Chemical Sciences, 11800 Minden, Penang, Malaysia c SINERGOS, via Livorno 60, 10144 Turin, Italy d Wood Preservation Laboratory, UR 40 Bois tropicaux, CIRAD PERSYST, Montpellier, France article info Article history: Received 14 May 2008 Received in revised form 27 June 2008 Accepted 29 June 2008 Keywords: Rigid foams Tannin Furanic Adsorption Heavy metals Pollution Wastewater abstract Tannin based rigid foams are structures in which flavonoids are randomly cross-linked with furanic units throughout covalent bonds. The use of these aromatic substrates from nat- ural materials to trap some heavy metal ions dissolved in water solutions is described. Interesting results have been achieved using different mimosa bark tannin (Acacia mearnsii formerly mollissima, De Wildt) and pine bark tannin (Pinus radiata) mixed foams. Capabil- ity to catch Pb 2+ and Cu 2+ ions at different concentrations has been verified throughout ICP-OES analysis of the foams. A reliable proportionality has been found between initial concentration and percentage of metal ions adsorbed. These foams were able to adsorb up to 12.5% of Cu(II) and 20.1% of Pb(II) with respect to the concentration of these ions in solution. © 2008 Elsevier B.V. All rights reserved. 1. Introduction Polyflavonoid or condensed tannins are natural compounds present in many plants. These compounds are used by plants as preservatives against biological attack by insects, fungi and bacteria (Hagerman et al., 1998; De Bruyne et al., 1999). The hydroxy-aromatic chemical composition and the high reactiv- ity with hardeners (formaldehyde, hexamine, etc.) have been the key for their development in wood adhesives (Pizzi et al., 1995; Pichelin et al., 1997). ∗ Corresponding author. Tel.: +33 329296117; fax: +33 329296138. E-mail address: gianluca.tondi@enstib.uhp-nancy.fr (G. Tondi). Flavonoid units present phloroglucinol/resorcinol-type A- rings and catechol/pyrogallol B-rings. These units are linked 0926-6690/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.indcrop.2008.06.006