Cost-efficient, vivid and stable red hybrid pigments derived from naturally available sepiolite and halloysite

Abstract A series of clay/Fe2O3 red hybrid pigments with vivid color, good stability and low cost was synthesized via a facile one-step reaction of Fe(III) solution with sepiolite (Sep) or halloysite (HNTs). Sep or HNTs plays key roles to promote the in-situ transformation of Fe(III) into red hybrid pigments, because only black product was formed from Fe(III) in the absence of them. The addition of Sep and HNTs avoids the usage of any chemical precipitants, which is greatly superior to the traditional process. The a* coordinate values of the sepiolite/Fe2O3 (Sep/Fe2O3) and halloysite/Fe2O3 (HNTs/Fe2O3) hybrid pigments are 25.1 and 34.4, respectively, which indicate they have well red color performance. The positive influence of Sep or HNTs on the crystallization process and dispersion of Fe2O3 particles is responsible for the good red color. In addition, the hybrid pigments exhibit excellent stability to resist external attacks such as light, acid, alkaline, organic solvents and high temperature, and can be facilely spray-coated onto various substrates, e.g., glass, wood plate, ceramic plate, stone plate, and polyester plate, etc. Therefore, they are potential to be used as promising low-cost environment-friendly colorants in many fields such as ceramic, painting, coating, and printing.