Chemical factors affecting selenite sorption by allophanic soils |
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| Institution: | 1. Department of Biotechnology and Translational Medicine University of Milan, Via F.lli Cervi, 93 - L.I.T.A., 20054 Segrate, MI, Italy;2. IIT, Via Morego, 30, 16163 Genova, Italy;3. CNR-IMM, Zona Industriale, VIII Strada 5, 95100 Catania, Italy;4. Department of Chemical Sciences University of Catania, Viale Andrea Doria, 6, 95125 Catania, Italy;5. CNR-IPCF, Viale Ferdinando Stagno d′ Alcontres, 98158 Messina, Italy;1. Helmholtz-Zentrum Dresden – Rossendorf, Institute of Resource Ecology, Bautzner Landstraße 400, 01328 Dresden, Germany;2. Paul Scherrer Institut, Waste Management Laboratory, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland;3. Helmholtz-Zentrum Dresden - Rossendorf, Computational Science Group (FWCC), Department of Information Services and Computing (FWC), Bautzner Landstraße 400, 01328 Dresden, Germany;4. Swedish Nuclear Fuel and Waste Management Co (SKB), Box 250, SE-101 24 Stockholm, Sweden |
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| Abstract: | The sorption of selenite by two allophanic soils containing high amounts of variable charge materials was studied. Selenite sorption exhibited a maximum near pH 4 and decreased, although not proportionally, with increasing pH. Only negligible amounts of selenite were sorbed above pH 7.In the two soils, the addition of selenite caused a release of sulphate (SO2?4), silicate (Si) and hydroxyl ion (OH?) and an increase in cation (Na+) adsorption. No measurable amount of phosphate (P) was released. Increase in negative charge as measured by Na+ adsorption accounted for 48 and 18% of selenite sorbed (soils 1 and 2, respectively), the rest being accounted for by release of anions. The results presented here are consistent with the widely held view that selenite and phosphate are sorbed onto variable charge surfaces by a similar mechanism (ligand exchange). |
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