The adsorption behavior of C.I. Acid Blue 9 onto calcined Mg–Al layered double hydroxides

Mesoporous calcined Mg–Al layered double hydroxides with different Mg/Al molar ratios were investigated for their ability to adsorb the commercial dye, C.I. Acid Blue 9, with a view to exploring their suitability as inorganic pigments in Ink Receptive Layer formulation. Uptake capacity was characterized using the Langmuir model and the resulting L-2/H-2 type plots indicated that the acid dye anions were adsorbed onto the surface by strong interactions. Optimum dye adsorption was achieved for a Mg/Al molar ratio ≈5.6. A surface adsorption mechanism is proposed to account for the adsorption of the dye onto the calcined Mg–Al layered double hydroxides. X-ray powder diffraction analysis indicated that given sufficient time it is possible to intercalate the dye within the layered double hydroxides' interlayer via a reconstruction mechanism. Scanning electron microscopy, N2 adsorption–desorption analysis and helium pycnometry were employed to examine the textural properties of the materials, which were correlated with their adsorption properties.