Selective extraction and separation of Fe, Mn oxides and organic materials in river surficial sediments

In order to investigate the adsorption mechanism of trace metals to surficial sediments (SSs), a selective extraction procedure was improved in the present work. The selective extraction procedure has been proved to selectively remove and separate Fe, Mn oxides and organic materials (OMs) in the non-residual fraction from the SSs collected in Songhua River, China. After screening different kinds of conventional extractants of Fe and Mn oxides and OMs used for separation of heavy metals in the soils and sediments, NH2OH · HCl (0.1 mol/L) + HNO3 (0.1 mol/L), (NH4)2C2O4 (0.2 mol/L) + H2C2O4 (pH 3.0), and 30% of H2O2 were respectively applied to selectively extract Mn oxides, Fe/Mn oxides and OMs. After the extraction treatments, the target components were removed with extraction efficiencies between 86.09%–93.36% for the hydroxylamine hydrochloride treatment, 80.63%–101.09% for the oxalate solution extraction, and 94.76%–102.83% for the hydrogen peroxide digestion, respectively. The results indicate that this selective extraction technology was effective for the extraction and separation of Fe, Mn oxides and OMs in the SSs, and important for further mechanism study of trace metal adsorption onto SSs.