Adsorption of Selenite and Selenate on Ferrihydrite in the Presence and Absence of Dissolved Organic Carbon
| Autor: | Paul R. Grossl, Matthew J. Eick, Jessica E. Favorito |
|---|---|
| Rok vydání: | 2018 |
| Předmět: |
Environmental Engineering
chemistry.chemical_element Selenic Acid 010501 environmental sciences Management Monitoring Policy and Law Selenious Acid Ferric Compounds complex mixtures 01 natural sciences Selenate chemistry.chemical_compound Ferrihydrite Adsorption Waste Management and Disposal 0105 earth and related environmental sciences Water Science and Technology Chemistry Sorption 04 agricultural and veterinary sciences Hydrogen-Ion Concentration Pollution Carbon Isoelectric point 040103 agronomy & agriculture 0401 agriculture forestry and fisheries Citric acid Salicylic acid Selenium Nuclear chemistry |
| Zdroj: | Journal of Environmental Quality. 47:147-155 |
| ISSN: | 0047-2425 |
| DOI: | 10.2134/jeq2017.09.0352 |
| Popis: | This study examines selenite [Se(IV)] and selenate [Se(VI)] adsorption on two-line ferrihydrite in the presence and absence of two low-molecular-weight dissolved organic carbon (DOC) species, citric and salicylic acid. Ferrihydrite surface potential measurements were also examined to identify shifts in isoelectric points, which suggest possible adsorption mechanisms. Sorption was completed in batch reactor systems at environmentally relevant pH. Our results indicate citric acid suppressed both Se(IV) and Se(VI) sorption on ferrihydrite, which may be caused by competition. This was especially evident at pH 5 to 7 for Se(IV) and pH 5 to 6 for Se(VI). Little sorption suppression was observed for both Se species in the presence of salicylic acid. In the presence of Se(IV) and Se(VI), citric acid adsorption was reduced (pH 5-8). Salicylic acid sorption was almost completely suppressed in the presence of Se(IV) throughout the entire pH range examined, with minimal sorption occurring at pH 5. In the presence of Se(VI), the largest reduction in salicylic acid sorption occurred at pH 5 to 6. Small shifts in the surface potential of ferrihydrite at higher pH suggest that Se(VI) and salicylic acid form weak, outer-sphere complexes. However, at pH 5 and 6, there is a shift in the surface potential measurements to more negative values, indicating possible formation of stronger, inner-sphere complexes. Larger surface potential shifts for Se(IV) and citric acid suggest the formation of strong, inner-sphere complexes. This work demonstrates the ability of low-molecular-weight DOC species (particularly for citric acid) to increase Se(IV) and Se(VI) solubility through sorption suppression. |
| Databáze: | OpenAIRE |
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