Browsing by Author "Ribeiro, Alexandra"
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- 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.
- Preliminary teatment of MSW fly ash as a way of improving electrodialytic remediationPublication . Ferreira, Célia; Jensen, Pernille; Ottosen, Lisbeth M.; Ribeiro, AlexandraIn the current work electrodialytic remediation (EDR) was applied to remove heavy metals from municipal solid waste (MSW) fly ash, a hazardous waste collected during flue gas treatment. Tests were conducted to evaluate if EDR could be improved by introducing a preliminary treatment in which very soluble salts were removed. Three different preliminary treatments were conducted with different L:S ratios and pH. Treatment in which metal release and L/S ratio were lower was selected for EDR. Electrodialytic remediation was performed at a constant current of 38 mA, for 14 days, using gluconate as a solubilisation enhancement agent. Conductivity and pH were monitored and electrolyte samples were collected every 4 days to evaluate metal release over time. It was found that the preliminary treatment reduces fouling of the ion-exchange membranes used in EDR and drastically increases the removal of metals. Remediation time was also considerably reduced. Additionally, preliminary washing reduces energy consumption during EDR, since electric current is not wasted in the transport of soluble salts. Sequential extraction was performed in the untreated and treated samples to help identify how metals are bond to the fly ash. It was seen that at the end metals are mainly found in the strongly bonded and residual phases. This indicates that the combined treatment (washing + EDR) is successful in reducing the environmental risk posed by fly ash.