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Removal and recovery of metals from waste using innovative liquid-liquid extraction processes

Metals in municipal and industrial wastes are removed using a combination of advanced models based on the theoretical fundamentals of fluid dynamics and molecular physics with innovative process integration and intensification techniques.

Waste incineration, with its 90% volume reduction, is the second waste management practice adopted across the world, especially in those countries where the lack of space for landfill is particularly serious. Nevertheless it may not be considered the final waste treatment stage: the resulting incineration product is estimated to be up to 35% of the original solid waste and contains a large amount of metals. In the resulting fly ash, the amount of some metals such as Cd, As, Hg, Pb, Zn appears very interesting for a possible recovery, especially Zn, Pb and Ti the content of which can reach 41,000, 19,000 and 12,000 ppm respectively. Less abundant but equally worthy to be taken into account for a possible extraction process is Cd (Cluster of Diffusion) because of its high value. The treatment of bottom ash, due to its high metal content and heavy metal problems (Cu, Sb, Mo), could be treated (after a pre-treatment) in a similar way as boiler ash and fly ash by hydrometallurgical processing. The residues coming from the utilisation of Thermal Tar for energy production usually contain about 6% of Zn and 17% of V. For the previously mentioned residues, the application of the hydrometallurgy technique is also becoming more important for both economic and environmental aspects. This is a three-stage treatment process which combines a leaching step followed by solvent extraction or an ion exchange process in order to separate out specific metals for reuse and declassification of waste residues. The success of the whole operation depends on the optimal selection of the extractant or exchanger to be used for selective separation of metal and the liquid-solid ratio, the operating temperature, etc. for the leaching of residues. The use of centrifugal contactors is attracting interest, as these relatively compact devices lend themselves to process intensification. In fact the short residence times of centrifugal contactors reduce the amount of solvent loss and therefore improve mass transfer, compared to conventional contacting devices. The main objectives of the project are: 1) To establish a set of guidelines for the optimal planning of experiments to identify thermodynamics and physical and chemical kinetic models for metal removal through liquid-liquid extraction processes. 2) To develop a protocol for the safety conditions under which all the laboratory experiments are to be carried out. 3) To combine advanced physical and chemical modelling with process optimisation, to reduce waste production rates and/or raw material costs. 4) To generalise the results obtained for wastes (typically ashes resulting from incineration and subjected to leaching treatments) as well as for important special cases from the chemical, electronics and steel industries by developing and validating a General Methodology from the technical and economical point of view. The project will be carried out in parallel by teams working on the different processes. The project will include the following steps: waste characterisation, model development, experiment planning, analysis of experimental data, selection of solvent for leaching and extraction and optimal flow sheet synthesis, development of a general methodology. Keywords: waste treatment, metal removal, separation processes.
Acronym: 
LILIEX
Project ID: 
3 895
Start date: 
19-06-2007
Project Duration: 
100months
Project costs: 
4 970 000.00€
Technological Area: 
Recycling, Recovery
Market Area: 
Other pollution and recycling related

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