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Characterisation of Weathered Bottom Ash for the critical metals recovery

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Treballs Finals de Grau de Química, Facultat de Química, Universitat de Barcelona, Any: 2018, Tutor: Josep Mª Chimenos Ribera

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Currently, modern high-technology industries have increased the use of precious metals and rare earth elements in Electric and Electronic Devices (EED). However, their natural resources are limited and have been exploited over the 60%, for most of them. Moreover, the economic or social situation of some metals providing countries supposes a high risk for their supply. The metals in this situation are called critical metals, and they are the main interest in the present project.
As the demand of critical metals is increasing due to the development of electronic industry, it is hugely important the search of sustainable and new sources. Incinerated municipal waste is a potential source of critical metals since a lot of EED are not recycled properly and incineration is a wide extended waste treatment in Europe. Weathered Bottom Ash (WBA) is the major by-product of incinerated municipal waste; therefore, it is the material used in this project to evaluate the valorisation of some selected critical metals contained.
A previous characterisation of WBA is carried out using different methods, such us particle size distribution, IR spectroscopy, X-ray fluorescence, and X-ray diffraction. The determination of the total amount of critical metals in WBA is performed by a total acid digestion. Besides, a sequential extraction is conducted to define their chemical form. Moreover, a comparison between WBA from two different seasons, winter and summer, is performed.
Results show that summer WBA sample contains more metals than winter WBA sample. The main metals in both samples are Al, Mg, and Cu, whereas the minor metals founded are Au, Ge, In, Ir and Ta. Furthermore, most of the critical metals evaluated are founded in the last step of the sequential extraction (residual), which means that they are in their crystalline structure and well stabilised in the matrix of the material, thus they cannot be extracted easily

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Characterisation of Weathered Bottom Ash for the critical metals recovery

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Caracterització d’Escograva per a la recuperació de metalls crítics