THE ROLE OF MINERALOGY IN CIRCULAR ECONOMY: FROM INORGANIC SPECIAL WASTES TO SECONDARY RAW MATERIALS

In this PhD project, I have applied the traditional methodologies of mineralogical investigation (e.g., optical and electron microscopy, X-ray spectrometry, and diffraction) to the study of three different inorganic special wastes, i.e.: a) asbestos-containing wastes (in particular, cement-asbestos materials, like the well-known Eternit); b) red gypsum and c) flotation muds, deriving from TiO2 and metallurgic industrial processing, respectively. Based on pre-existing patents, the above wastes have been suitably processed transforming them into secondary raw materials (SRM), for potential applications in the ceramic, building, and construction industries. Different products obtained using variable amounts of the above inorganic wastes, were carefully investigated to determine their mineralogy, chemical composition, and micro/nanostructural characteristics (such as grain size and porosity). This investigation has been fundamental to understand the actual commercial potentials of the different products. The last step of my research has been done through strict collaboration with researchers from other disciplines, with two main objectives: i) obtainment of CBA cost-benefit analysis, and LCA life cycle assessment for the different waste types; and ii) obtainment of technical data on the new commercial products, through the executions of mechanical strength and chemical leaching tests, as required by current regulations. This last step has been completed only for cement asbestos wastes, whereas it is still under progress in the other cases. Overall results aim to demonstrate the role of Mineralogy in circular economy projects, also remarking how the irreversible depletion of natural mineral resources, associated with a human waste increase, makes the circular economy target mandatory. The concrete realization of circular economy projects, such as the ones suggested in this work, often based on solid scientific evidence, requires however convincing (social, political, and economic) support by the Institutions and by involved stakeholders, in order to obtain an effective transition from the laboratory to the industrial scale.