Study on the effects of cationic dyes species on the structure and performance of sepiolite hybrid pigments

In this work, sepiolite hybrid pigments were prepared with four kinds of cationic dyes with different structures and functional groups, Basic orange 2 (BO2), Mytheme blue (MB), Basic red 18 (BR18) and Basic red 2 (BR2), by the vacuum method. The obtained samples were respectively named as BO2/Sep, MB/Sep, BR18/Sep and BR2/Sep. The sepiolite hybrid pigments were characterized and tested by XRD, FT-IR, Microporous physical/chemical adsorption analyzer, thermal analyzer, et al. The effects of cationic dyes structure and functional groups types on the positions and loading capacity of cationic dyes in sepiolite hybrid pigments were investigated. The results indicated that positions and loading capacity of cationic dyes in sepiolite hybrid pigments are not only related to the size of the cationic dyes but also related to the functional groups and electrical properties of the cationic dyes. The smaller the size of the cationic dyes, the greater the positive charge, and the stronger the functional groups interact with the sepiolite, the greater the amount that enters the sepiolite channel and is adsorbed. The loading capacity of cationic dyes in hybrid pigments dropped as the order MB/Sep, BO2/Sep, BR18/Sep, BR2/Sep. In addition, the position and interaction of cationic dye in sepiolite determine the stability of hybrid pigments. The resistance of hybrid pigments to the acid decreased as the order MB/Sep, BR18/Sep, BO2/Sep, BR2/Sep. In the base medium, the order is MB/Sep, BO2/Sep, BR18/Sep, BR2/Sep. The weatherability of the hybrid pigments was also better than pure cationic dyes.