Browsing by Author "Ottosen, Lisbeth M."
Now showing 1 - 10 of 27
Results Per Page
Sort Options
- Ammonium citrate as enhancement for electrodialytic soil remediation and investigation of soil solution during the processPublication . Ottosen, Lisbeth M.; Ferreira, Célia; Kirkelund, Alexandra B.Seven electrodialytic experiments were conducted using ammonium citrate as enhancing agent to remediate copper and chromium-contaminated soil from a wood-preservation site. The purpose was to investigate the effect of current density (0.2, 1.0 and 1.5 mA cm2 ), concentration of enhancing agent (0.25, 0.5 and 1.0 M) and remediation times (21, 42 and 117 d) for the removal of Cu and Cr from a calcareous soil. To gain insight on metal behavior, soil solution was periodically collected using suction cups. It was seen that current densities higher than 1.0 mA cm2 did not increase removal and thus using too high current densities can be a waste of energy. Desorption rate is important and both remediation time and ammonium citrate concentration are relevant parameters. It was possible to collect soil solution samples following an adaptation of the experimental set-up to ensure continuous supply of ammonium citrate to the soil in order to keep it saturated during the remediation. Monitoring soil solution gives valuable information on the evolution of remediation and helps deciding when the soil is remediated. Final concentrations in the soil ranged from 220 to 360 mg Cu kg1 (removals: 78–86%) and 440– 590 mg Cr kg1 (removals: 35–51%), being within the 500 mg kg1 limit for a clean soil only for Cu. While further optimization is still required for Cr, the removal percentages are the highest achieved so far, for a real Cu and Cr-contaminated, calcareous soil. The results highlight EDR potential to remediate metal polluted soils at neutral to alkaline pH by choosing a good enhancement solution.
- Effect of major constituents of MSW fly ash during electrodialytic remediation of heavy metalsPublication . Ferreira, Célia; Ribeiro, Alexandra; Ottosen, Lisbeth M.Electrodialytic remediation (EDR) is a technique in which contaminants are removed from waste material by applying an electric field which forces their movement into concentration chambers through ion-exchange membranes. In the current work EDR is used for the treatment of heavy metal–contaminated fly ash. The objective is to study the impact of major constituents of fly ash on remediation times, on efficiency, and on the performance of membranes. The results show that major constituents foul the ion-exchange membranes, decreasing their ability to transport metal ions out of the waste compartment.
- Electro-desalination of glazed tile panels: discussion of possibilitiesPublication . Ferreira, Célia; Ottosen, Lisbeth M.; Ribeiro, Alexandra B.
- Electrochemical desalination of historic Portuguese tiles, azulejos, in laboratory scalePublication . Ottosen, Lisbeth M.; Ferreira, Célia; Christensen, I. V.
- Electrochemical desalination of historic Portuguese tiles-Removal of chlorides, nitrates and sulfatesPublication . Ottosen, Lisbeth M.; Ferreira, Célia; Ribeiro, Alexandra B.Soluble salts cause severe decay of historic Portuguese tiles. Treatment options for removal of the salts to stop the decay are few. The present paper deals with development of a method for electrochemical desalination, where an electric DC field is applied to the tiles. Laboratory experiments were conducted with single 18th century tiles from Palácio Centeno, Lisbon, Portugal. Large parts of the glaze and parts of the biscuit were lost from salt decay. The major aim of the investigation was to see if the method could offer sufficient salt removal in the biscuit and in the interface between biscuit and glaze, where salt crystals were clearly identified by SEM-EDX before desalination. The concentrations of chloride and especially nitrate were very high in the tiles (around 280 mmol Cl−/kg and 450 mmol NO3 −/kg respectively). Both anions were successfully removed to below 6 mmol/kg during the electrochemical treatment. The removal rate was similar for the two anions so the chloride concentration reached the lowest concentration level first. At this point the electric resistance increased, but the removal of nitrate continued unaffected till similar low concentration. The sulfate concentration was initially very low, but nevertheless, sulfate removal started at the point where chloride and nitrate concentrations were very low in the tiles. Investigating the interface between biscuit and glaze after the treatment showed no signs of crystallized salts, so also in this important point, the desalination was successful. Based on the obtained results an important step is taken towards development of an electrochemical technique for desalination of tile panels.
- Electrodialytic remediation of heavy metal polluted soil: treatment of water saturated or suspended soilPublication . Ottosen, Lisbeth M.; Jensen, Pernille E.; Kirkelund, Gunvor M.; Ferreira, Célia; Hansen, Henrik K.Electrodialytic soil remediation is a method for removal of heavy metals. Good results have previously been obtained with both treatment of a stationary, water saturated soil matrix and with remediation of a stirred suspension of soil in water. The two different setups have different uses. The first as in-situ or on-site treatment when there is no requirement for fast remediation, as the removal rate of the heavy metals are dependent on the distance between the electrodes (everything else equal) and in such application the electrode spacing must have a certain distance (often meters). In the stirred setup it is possible to shorten the transport route to few mm and to have a faster and continuous process. The present paper for the first time reports a direct comparison of the two options. The remediation of the stirred suspension showed faster than remediation of the water saturated soil even without a short distance between the membranes. The acidification of the suspended soil was fastest and following the mobilization of heavy metals. This may indicate that water splitting at the anion exchange membrane is used more efficiently in the stirred setup.
- Electrodialytic remediation of of polychlorinated biphenyls contaminated soil with iron nanoparticles and two different surfactantsPublication . Gomes, Helena I.; Ferreira, Célia; Ottosen, Lisbeth M.; Ribeiro, Alexandra B.Polychlorinated biphenyls (PCB) are persistent organic pollutants (POP) that strongly adsorb in soils and sediments. There is a need to develop new and cost-effective solutions for the remediation of PCB contaminated soils. The suspended electrodialytic remediation combined with zero valent iron nanoparticles (nZVI) could be a competitive alternative to the commonly adapted solutions of incineration or landfilling. Surfactants can enhance the PCB desorption, dechlorination, and the contaminated soil cleanup. In this work, two different surfactants (saponin and Tween 80) were tested to enhance PCB desorption and removal from a soil sampled at a polluted site, in a two-compartment cell where the soil was stirred in a slurry with 1% surfactant, 10 mL of nZVI commercial suspension, and a voltage gradient of 1 V cm1 . The highest PCB removal was obtained with saponin. Higher chlorinated PCB congeners (penta, hexa, hepta and octachlorobiphenyl) showed removal percentages between 9% and 96%, and the congeners with highest removal were PCB138, PCB153 and PCB180. The use of low level direct current enhanced PCB removal, especially with saponin. Electrodechlorination of PCB with surfactants and nZVI showed encouraging tendencies and a base is thus formed for further optimization towards a new method for remediation of PCB polluted soils.
- Electrodialytic remediation of soil fines (<63 μm) in suspension-Influence of current strength and L/SPublication . Jensen, P. E.; Ottosen, Lisbeth M.Current treatment of the remaining soil fines from soil wash is onerous and expensive, and therefore, in this work, we investigated the feasibility of electrodialytic remediation (EDR) as an alternative treatment. The study focuses on EDR efficiency as a function of current strength, liquid-tosolid-ratio (L/S), pH and time. We found out that during the experiments, Pb was easily dissolved by the acidification resulting from water splitting at the anion-exchange membrane. When higher currents and/or higher L/S ratios were applied, it was found that water splitting occurring at the cation-exchange membrane increased the pH, and this resulted in decreased remediation efficiency. It was shown that complete remediation of the soil-fines is possible, with the majority of the Pb being transported into the catholyte and precipitated at the cathode. Based on the results it is recommended that EDR is implemented using a number of reactors in series, where the initial reactor works at the highest possible removal rate, and the final reactor works at the target Pb-concentration.
- Electrodialytic upgrading of MSWI APC residue from hazardous waste to secondary resourcePublication . Jensen, Pernille E.; Kirkelund, Gunvor M.; Viader, Raimon Parés; Magro, Catia; Pedersen, Kristine B.; Ferreira, Célia; Ottosen, Lisbeth M.
- Electrodialytic upgrading of three different municipal solid waste incineration residue types with focus on Cr, Pb, Zn, Mn, Mo, Sb, Se, V, Cl and SO4Publication . Jensen, Pernille E.; Kirkelund, Gunvor M.; Pedersen, Kristine B.; Ottosen, Lisbeth M.; Ferreira, CéliaHandling of air pollution control (APC) residues from municipal solid waste incineration (MSWI) is a challenge due to its toxicity and high leaching of toxic elements and salts. Electrodialysis (ED) of the material has shown potential for reduction of leaching of toxic elements and salts to produce a material feasible for substitution of cement in mortar. In this work results of 23 pilot-scale experiments (5–8 kg APC residue each) in electrodialysis stack designed to investigate the leaching properties as a function of time and current density for APC residue from semi-dry and wet flue-gas cleaning systems, as well as MSWI fly ash without flue-gas cleaning products are reported. Significant leaching reduction of the critical elements Pb, Zn and Cl was obtained. The final leaching, however, depended mostly on the initial leaching, thus as leaching from fly ash and residue of wet flue-gas cleaning was lower before treatment compared to residues from semidry flue-gas cleaning, both Pb and Zn leaching could be reduced to lower levels in those materials, and they therefore appear more suitable for use in construction materials. The leaching reduction of Zn and to some degree Pb decreased with longer retention times and higher current densities. Cr and SO4 leaching increased during ED treatment, with lower increase at higher current. Washing or carbonation in combination with ED significantly reduced leaching of Pb and Zn from semidry residue. An indication of a similar effect to carbonation by simultaneous aeration with ED was observed and should be investigated further. While Mn and Mo leaching did not, Se, V and Sb leaching exceeded threshold values in semidry residue. The leaching of V seemed to increase while Se and Sb remained more or less constant during ED treatment.
- «
- 1 (current)
- 2
- 3
- »