Synthesis and Characterization of the Carbonate Hydrotalcites (NiAl-HT, CoAl-HT, and NiCoAl-HT), and Its Application for Removal of the Anionic Azo Dye Titan Yellow from Aqueous Solution

This work focuses on studying the removal of Titan Yellow (TY) dye, which is a water pollutant using three matrices of layered double hydroxide (LDHs; M +2 Al-HT), with M +2 = Ni, Co, or NiCo were synthesized using the co-precipitation technique in a solution with a constant pH. The X-ray diffraction (XRD) pattern of the formed solids shows that the synthesized phase is the LDH type with the average interlamellar distance ( d spacing ≈ 7.595 Å). The Fourier-transform infrared spectroscopy (FT-IR) spectra were compared, before and after adsorption, confirming the displacement of the carbonated interlayers and confirmed the presence of the S=O bond in the dye under study. Thermogravimetric-differential thermal analysis (TG/DTG) shows temperatures of decarbonation of the LDHs. The BET specific surface areas of NiAl-HT, NiCoAl-HT, and CoAl-HT were found equal to 156.819 m 2 ∙g −1 , 142.72 m 2 ∙g −1 , and 56.98 m 2 ∙g −1 , respectively, and the SEM-EDX micrographs results confirmed the creation of the hydrotalcite type material. The UV–visible study of the adsorption of TY is performed by varying different parameters such as pH of the solution, mass, contact time, and temperature. The obtained isotherms from this kinetic study show that the adsorption of TY dye is more efficient in NiAl-HT. It can, therefore, be stated that the adsorption process of TY is endothermic and spontaneous. The results of this study could be extended to other anionic azo dyes having similar chemical structures.