Adsorption of ink-jet inks and anionic dyes onto Mg-Al-NO3 layered double hydroxides of variable Mg:Al molar ratio

Layered double hydroxides are materials that show promise as adsorbing media for ink-jet printing. In this work, layered double hydroxides with nitrate as interlayer anions and with variable Mg:Al molar ratios ranging from 2.2 to 8.1 have been synthesized at constant pH by the coprecipitation method and characterized by powder X-ray diffraction, N2 adsorptiona?? desorption, scanning electron microscopy, and helium pycnometry techniques. The ability of these materials to adsorb ink-jet inks (BCI-Cyan, BCI-Yellow, and BCI-Magenta) and anionic dyes (CI Acid Blue 9 (AB9), CI Acid Yellow 23 (AY23), and CI Acid Red 37 (AR37)) were investigated. BCI-Yellow was found to have high affinity for material with an Mg:Al molar ratio between 2.2 and 4.0, whereas BCI-Cyan and BCI-Magenta showed a high affinity when the Mg:Al molar ratio was between 4.8 and 5.5. The adsorption isotherms for AB9, AY23, and AR37 on the material with Mg:Al molar ratios 2.2a??5.5 exhibited H-type curves, indicating a very strong interaction between the adsorbate and adsorbent. Although there was no clear systematic correlation between the Mg:Al molar ratio and the Cm (dye capacity) and Ka (dye affinity), the optimum Mg:Al molar ratio was 4.0, and this material has the potential to be used in Ink-Receptive Layer formulation.