Coating organic pigment particles with hydrous alumina through direct precipitation

A novel coating process of hydrous alumina on organic pigment particles through direct precipitation in aqueous solution was developed in this work. The aqueous suspensions of organic pigment particles were prepared using cetyltrimethylammonium bromide (CTAB) and sodium dodecylbenzene sulfonate (SDBS) as additives before the coating. The organic pigment particles were then coated with hydrous alumina using Al2(SO4)3 as precursor. The morphology and surface states of as-coated organic pigment particles were analyzed by high-resolution transmission electron microscopy (HRTEM) and zeta-potential. TEM images showed that a uniform hydrous alumina film could be formed on the organic pigment particle surface with anion surfactant SDBS. However, with cation surfactant CTAB, no alumina coating film was generated on the organic pigment particle surface.

► Organic pigments coating process was highly depended on the surfactants. ► The content of the organic pigment particles reached 200 g/L ► The solvent is deionized water, temperature = 20 °C, and pH = 6. ► The coating condition is moderate. ► The processes can be scaled up easily and economically.