In this study, waste-derived hematite pigments were modified with nano-oxides (TiO₂, SiO₂, and Al₂O₃) using a mechanical coating process to enhance their functional properties. Hematite base pigments were synthesized via a microwave-assisted method at varying pH levels, resulting in distinct morphological characteristics. To prevent secondary agglomeration and tailor surface reactivity, the hematite particles were modified with nano-oxides (TiO₂, SiO₂, and Al₂O₃) using a mechanical coating process. The resulting modified systems were characterized by Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), Dynamic Light Scattering (DLS), oil absorption measurements, and zeta potential analysis. The results confirm the successful deposition of nano-additives on the hematite surface, leading to a significant reduction in average particle size and improved dispersion stability. Specifically, the mechanical coating allowed for precise control over the specific surface area, with BET values ranging from 4 to 49 m²/g and total pore volumes between 0.014 and 0.255 cm³/g. The dispersion stability was remarkably improved, as demonstrated by the shifting of the isoelectric point and zeta potential measurements, where modified systems showed enhanced surface charge density. These quantitative improvements in particle characteristics resulted in a reduction in oil absorption and enhanced color stability, confirming the effectiveness of the nano-oxide coating in tailoring the functional properties of hematite-based pigments.
Splinter et al. (Fri,) studied this question.