Effect of Remineralization on Heavy-Metal Leaching from Cement-Stabilized/Solidified Waste
| Autor: | Ernest K. Yanful, Mohammad Z Islam, Lionel J J Catalan |
|---|---|
| Rok vydání: | 2004 |
| Předmět: |
Ettringite
Mineralogy engineering.material Portlandite law.invention chemistry.chemical_compound law Metals Heavy Soil Pollutants Environmental Chemistry Water Pollutants Leachate Particle Size Calcium silicate hydrate Sulfate Dissolution Construction Materials Chemistry General Chemistry Hydrogen-Ion Concentration Refuse Disposal Portland cement Microscopy Electron Scanning engineering Leaching (metallurgy) Environmental Monitoring Nuclear chemistry |
| Zdroj: | Environmental Science & Technology. 38:1561-1568 |
| ISSN: | 1520-5851 0013-936X |
| DOI: | 10.1021/es034659r |
| Popis: | Crushed samples of stabilized/solidified (s/s) waste were leached at constant leachate pH in the pH range 4-7 with nitric acid solutions to evaluate the influence of remineralization on metal release. The s/s waste consisted of synthetic heavy-metal sludge containing 0.1 mol L(-1) copper nitrate, 0.1 mol L(-1) zinc nitrate, and 0.1 mol L(-1) lead nitrate mixed with ordinary Portland cement. Unleached and leached particles were characterized by scanning electron microscopy and energy-dispersive X-ray spectrometry. Two consecutive leaching fronts advancing from the surface of the particles toward the center were identified: the first front was associated with the dissolution of portlandite and partial reaction of the calcium silicate hydrate gel, while the second front was associated with the dissolution of calcium-aluminum hydroxy sulfates such as ettringite and monosulfate. At pH 4 and 5, a remineralization zone rich in heavy metals formed immediately behind the second leaching front. The shell extending from the remineralization zone to the surface of the particles was depleted in calcium, sulfate, and heavy metals. As a result of remineralization, heavy-metal releases to the leachate were reduced by factors ranging between 3.2 and 6.2 at pH 4 and between 74 and 193 at pH 5. At pH 6 and 7, remineralization of Pb and Zn occurred further behind the second leaching front and closer to the surface of the particles. The amount of heavy-metal release depended on both the leachate pH and the remineralization factor. |
| Databáze: | OpenAIRE |
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