From high-volume industrial waste to new ceramic material: The case of red gypsum muds in the TiO2 industry

The present study aims to apply the principles of circular economy, using special inorganic waste (in particular, red gypsum muds from a TiO2 plant in Tuscany, Italy) to produce ceramic materials for the construction and building industries. Red gypsum (RG) muds produced during more than 10 years of industrial processing were chemically and mineralogically characterized by X-ray fluorescence spectrometry (XRF), X-ray powder diffraction (XRPD), scanning electron microscopy with energy dispersive X-ray spectrometer (SEM/EDS), and thermal analyses (TA). The analyses testify that RG waste production is chemically and mineralogically constant over time, and therefore suitable to be used as a secondary raw material in industrial ceramic production. Ceramic specimens have been realized using an extremely high amount of the RG waste (up to 70%) and characterized using the same chemical-mineralogical techniques, revealing that anhydrite, pyroxene, and Fe/Ti oxides are the main crystalline phases, embedded in a glassy compact matrix. Overall results indicate that the production of ceramic materials could represent a definitive and sustainable solution for the problematic management of the large volumes of RG waste deriving from TiO2 plants.

Automated summary

The study aims to utilize red gypsum muds from a TiO2 plant in Tuscany, Italy to produce ceramic materials for construction industry based on the principles of circular economy. The characterization of the red gypsum muds reveals its consistent chemical and mineralogical properties over time, which makes it suitable as a secondary raw material for industrial ceramic production. Ceramic specimens fabricated using a high proportion of red gypsum waste (up to 70%) consists of anhydrite, pyroxene, and Fe/Ti oxides as the main crystalline phases embedded in a glassy compact matrix. The production of ceramic materials could provide a sustainable solution for the management of large volumes of red gypsum waste from TiO2 plants.