Green synthesis of diopside from hazardous waste: crystal structure and applications

A green and efficient route to synthesize pure diopside using recycled hazardous mineral wool waste is presented, marking the first successful transformation of this waste into a valuable ceramic material. Hazardous mineral wool undergoes industrial thermal inertization to form an inert glass (Re.Wo) to be used at up to 40 wt.% in the diopside formulation. Chemical-grade reagents generally used for the diopside synthesis are replaced by waste and natural raw materials. Unlike other waste-based approaches, this method requires no energy-intensive pre-treatments and avoids CO₂-emitting inputs. The resulting diopside exhibits broad application potential, including biomedical devices, low-expansion dielectric ceramics, photo-catalysis, and environmental remediation—leveraging transition metals within the crystal structure to enhance catalytic performance. Importantly, the process also immobilizes hazardous elements (e.g., Cr) without generating carcinogenic crystalline silica phases, offering both environmental and functional advantages.