Synthesis, characterization, and application of low-cost Mg-Al/CO and Ni-Al/CO layered double hydroxides (LDHs) as adsorbents for the removal of aniline blue dye from aqueous solutions: adsorption isotherms, kinetics, and thermodynamic studies.

Low cost Mg-Al/CO and Ni-Al/CO layered double hydroxides (LDHs) were prepared using a co-precipitation technique to improve their dye adsorption efficiency. Characterization techniques were employed to assess their structure and surface properties, including FT-IR, XRD, SEM, BET surface analysis, and UV-vis spectroscopy. The BET analysis revealed surface areas of 82.63 m g for Mg-Al/CO and 5.95 m g for Ni-Al/CO, highlighting their porous nature. The materials' capability to adsorb aniline blue from water was tested under various conditions, such as time, pH, dye concentration, and temperature. The adsorption data were analyzed using both Langmuir and Freundlich isotherm models. The Mg-Al/CO LDH exhibited a notably higher maximum adsorption capacity of 704 mg g, compared to 181 mg g for Ni-Al/CO LDH, according to the Langmuir model. The correlation coefficients ( ) indicate that the Freundlich model better fits the Mg-Al/CO LDH data ( = 0.9829), while the Langmuir model offers a better fit for Ni-Al/CO LDH ( = 0.9576). While kinetic studies showed that the pseudo-second-order model provided the best fit. The process was spontaneous and endothermic based on thermodynamic analysis, with positive entropy changes suggesting increased randomness at the interface. These results underscore the promise of using Mg-Al/CO and Ni-Al/CO LDHs as economical adsorbents in water purification.