| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 608126 | Journal of Colloid and Interface Science | 2012 | 6 Pages |
The presence of iron oxides may play an important role in controlling the mobility and availability of contaminants in soils and waters affected by acid mine drainage. The present study describes the uptake of arsenate, chromate and molybdate from solution by synthetic schwertmannite. Batch experiments were performed at different pH values in order to obtain the adsorption isotherms for the three oxyanions. In addition to the formation of surface complexes between the oxyanions and the iron surface reactive groups, it is also expected that anion exchange will occur between sulphate anions from the schwertmannite structure and the oxyanions present in the solid/solution interface. Comparison of the experimental adsorption results for the different oxyanions showed large differences, not only the amount adsorbed, which was much higher for arsenate, but also in the sulphate exchange with the anions in solution. In case of chromate, the main mechanism of adsorption process is the exchange reaction with the sulphate groups present in the schwertmannite. The observed results suggest a different adsorption mechanisms for each of the three oxyanions, with important implications for the mobility of these anions in acid mine drainage systems.
Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (305 K)Download as PowerPoint slideHighlights► Adsorption onto schwertmannite contributes to control oxyanions mobility in AMD. ► Different schwertmannite preparations exhibit different reactivity against oxyanions. ► Surface complexation and anion exchange control schwertmannite reactivity in solution. ► The affinity sequence AsO43->MoO42->CrO42- has been found for schwertmannite. ► Chromate adsorption on schwertmannite takes place through anion exchange only.
