Upcycling Chrysotile Asbestos Waste into High-Performance Wollastonite Chemisorbents for Demetallization and Desulfurization of Heavy Oil Residues

The disposal of chrysotile asbestos waste poses significant environmental hazards, while heavy oil residues demand costly pretreatment to remove toxic metals and sulfur. This study presents a circular economy approach to convert acid-leached chrysotile asbestos waste into a functional chemisorbent for the simultaneous demetallization and desulfurization of heavy petroleum residues. Following hydrochloric acid leaching, the asbestos waste transformed into an amorphous, highly reactive silica-rich material. Through high-temperature synthesis (1100 - 1280 °C) with calcium and sodium carbonates, a wollastonite (CaSiO₃) and calcium silicate-based chemisorbent was produced. Comprehensive characterization using XRD, FTIR, TG-DTA, BET, and EPR confirmed that the synthesized material exhibits a remarkably high specific surface area (280 - 315 m²/g), substantial pore volume (1.213 cm³/g), and abundant active paramagnetic centers - far exceeding those of commercial zeolite. When tested in the thermal adsorption treatment of vacuum tar (380 - 410 °C), the chemisorbent achieved removal efficiencies of 40 - 55% for vanadium (V), nickel (Ni), and iron (Fe), along with significant sulfur reduction. These results demonstrate a viable pathway for transforming hazardous asbestos waste into a value-added adsorbent, enabling cleaner heavy oil processing and reducing both industrial waste and refinery operating costs.