Synthesis of Dye and Heat-Treated Halloysite Nanotube Hybrids and their Color Properties and Chemical Resistances.

A series of new organic–inorganic nanohybrids were successfully prepared by using Congo red and heat-treated halloysite clays. The results show that an increase in calcination temperature leads to the reduction of lightness (L *) and color hue (a *, b *). The hybrids prepared, respectively, with 400∘C treated and 500∘C treated halloysites have the same order of HNO 3 > HCl > H 2 SO 4 with respect to the acid resistance. The hybrid with a light red hue can be obtained by alkali treatment when halloysite calcined at higher temperature was used as a host. There exists a strong host–guest interaction between nanotubes and Congo red anions. The leaching of aluminum in the clay has a decisive influence on the acid/alkali resistance of the hybrid. A series of Congo red and heat-treated halloysite nanotube hybrids was prepared using adsorption–desorption method. The calcination temperature of halloysite has a significant effect on the color and chemical resistance of the hybrids, especially for the samples calcined at 400 and 500∘C. The color of the hybrids is mainly controlled by the amount of dye loaded on halloysite nanotubes, and the leaching amount of Al3+ from clay in strong acid or base system is the decisive factor for the chemical resistance. [ABSTRACT FROM AUTHOR]