The aim of the authors' work is the utilisation without any chemical modification of eucalyptus bark of Lebanese origin for the fixation of heavy metals. The bark is subjected to a pretreatment in acid with formaldehyde or in extraction of cold water or hot water. The adsorption capacity of the Cu(II), Cr(III), Cd(II) and Ni(II) ions are studied as a function of pretreatment of contact time (between 15 minutes and 48 hours) and of variable pH of the solution (between 3 and 6), the concentration of metallic ions (between 10/sup -2/ and 10/sup -1/ M), and the temperature (between 20 and 73/spl deg/C). The concentrations are determined before and after adsorption, by colorimetric titration and/or by atomic absorption. The results show that the adsorption increases with the time, with the pH, with the initial concentration of the solution and decreases with the temperature. The adsorption capacities are 2.61, 2.24, 0.75 and 0.71 mmol per gramme of adsorbent for Cu(II), Cd(II), Ni(II) and Cr(III) respectively. The desorption of metallic cations is easily realised by treatment of the bark with a solution of ethylene diamine tetracetate. The eucalyptus bark acts then, not only as an agent for metallic decontamination, but also as a pollution concentrator.
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