Evaluation of a combined chemical, electrochemical,and mechanochemical approach for metal extractionfrom contaminated dredged sediments: preliminary studies
Purpose This study investigates the efcacy of a combination of chemical, electrical, and mechanical methods for extracting specifc metal contaminants from marine dredged sediment. Materials and methods Samples of muddy contaminated sediment from a Spanish harbor were characterized, including the mod...
| Autores: | , , , |
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| Tipo de recurso: | artículo |
| Estado: | Versión publicada |
| Fecha de publicación: | 2024 |
| País: | España |
| Institución: | Consejo Superior de Investigaciones Científicas (CSIC) |
| Repositorio: | DIGITAL.CSIC. Repositorio Institucional del CSIC |
| OAI Identifier: | oai:digital.csic.es:10261/375611 |
| Acceso en línea: | http://hdl.handle.net/10261/375611 |
| Access Level: | acceso abierto |
| Palabra clave: | Contaminated marine dredged sediment Heavy metals Desorption Electrical current Ultrasounds Recirculation Enhancing solutions Treatment technology |
| Sumario: | Purpose This study investigates the efcacy of a combination of chemical, electrical, and mechanical methods for extracting specifc metal contaminants from marine dredged sediment. Materials and methods Samples of muddy contaminated sediment from a Spanish harbor were characterized, including the mode of occurrence of heavy metals, using sequential chemical extraction. Desorption tests were conducted using the sediment in its fresh state, in a custom-built cell/reactor flled with an electrolyte—either a solution of 0.25 M citric or acetic acid, or deionized water. Electrical current, ultrasonic energy, and circulating fow were applied in various combinations, and the efcacy of such combinations on the metal desorption was evaluated. After the experiments, the solutions were analyzed using inductively coupled plasma-optical emission spectrometry (ICP-OES). X-ray difraction (XRD) and thermogravimetric analysis/diferential thermal analysis (TG/DTA) were performed on the sediment. Results The sequencial extraction revealed that most metals (excluding Hg, Pb and Zn) were primarily bound to the residual fraction (fraction V), with As and Cu exhibiting the highest concentrations. Cadmium and mercury were preferentially extracted in fraction IV, associated with organic matter. Pb and Zn exhibited their highest percentages in fraction III, bound to Fe–Mn oxides. Regarding desorption, the results indicated that increasing treatment time enhanced metal desorption, with the most signifcant efect observed during the initial stages. The electrolyte used emerged as the most infuential factor. Citric acid proved more efective for As, Cr, and Ni, while acetic acid favored Cu, Pb, and Zn extraction. As, Pb, and Zn exhibited preferential desorption in the presence of ultrasounds, while Cr, Ni, Pb, and Zn desorbed more readily under electrical current. Application of electrolyte circulation had a positive efect on the extraction of all metals. Conclusions Changes in the electrolyte's chemical composition are the most signifcant factor infuencing metal desorption. In addition to the electrolyte used, the application of some form of energy had a slight positive efect on metal desorption. However, at this stage it seemed that the synergistic efect of both electric feld and ultrasounds appears to be only relevant for Cu. Electrolyte circulation had a positive impact on metal desorption for all metals tested. The concentration of recalcitrant and refractory organic matter decreased after all the tests, indicating its degradation into more labile matter. |
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