Mechanochemical effect assisted oxidative whitening of black talc

Abstract

Black talc, a carbon-intercalated phyllosilicate mineral, is significantly limited in industrial applications due to its intrinsic low whiteness. Conventional whitening methods relying on high-temperature calcination inevitably compromise its layered crystalline structure through thermal decomposition. This study presents a mechanochemically assisted oxidative strategy that achieves effective whitening while preserving structural integrity. By combining mechanical exfoliation with oxidative activation, the interlayer graphite carbon domains in black talc were selectively oxidized, thus significantly increasing the whiteness. Compared with mechanical treatment alone (whiteness 25.7) or chemical treatment alone (whiteness 52.4), the synergistic coupling of mechanical activation and oxidant (whiteness 75.7) increased the whitening efficiency by 626 % and 299 %, respectively. Systematic characterization via X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA) revealed a synergistic mechanism: (i) mechanical delamination exposing encapsulated carbon layers and (ii) surface activation promoting oxidative radical generation for carbon removal. Notably, the layered framework remained intact post-treatment, as evidenced by maintained interlayer spacing and absence of phase transformation, contrasting sharply with the structural collapse observed in calcination-based approaches. Although current exploration focuses on carbonaceous minerals, this mechanochemical paradigm establishes a versatile platform for high-value utilization of heat-sensitive mineral resources, particularly in applications demanding structural preservation, such as functional composites and precision ceramics manufacturing.