Competitive sorption of copper(II), chromium(III) and lead(II) on ferrihydrite and two organomineral complexes

The competitive sorption of Cu, Cr and Pb on a ferrihydrite and two synthetic organomineral complexes, obtained by coprecipitating iron with different quantities of oxalate and tartrate were studied. Greater amounts (μmol/m2) of heavy metals were sorbed onto the organomineral complexes than ferrihydrite, the higher the carbon content in the samples the greater the sorption of heavy metals. Lead was sorbed much more and more tightly than Cr and Cu on the sorbents. In binary systems, the sorption and the inhibitive efficiency of one metal (M1) to the other (M2) were affected by the nature of the metal, initial M2/M1 molar ratio, addition sequence of M1 and M2, and residence time. Lead showed a much greater capacity to inhibit the sorption of the other two metals, whereas the opposite was true for Cu. In ternary systems, when equimolar amounts of each metal were added, the sorbents were covered with more than 50% by Pb alone. However, even in the presence of large excess of Pb and Cr, considerable extent of Cu sorption still occurred regardless of sorbent types, indicating that some sorption sites on each sorbent had a high affinity for Cu. The results of this study would contribute to further our current understanding on the mobility of multi heavy metals in soils and related environments.