Chemical factors affecting selenite sorption by allophanic soils
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).
| Main Authors: | , |
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| Format: | artículo biblioteca |
| Published: |
Elsevier BV
1994
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| Online Access: | http://hdl.handle.net/10261/244511 |
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| Summary: | 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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