Synthesis of LDH-MgAl and LDH-MgFe composites for the efficient removal of the antibiotic from water.

In this study, novel lamellar double hydroxide composites (LDH-MgAl and LDH-MgFe) were synthesized at different metal salt ratios (1:1 to 3:1) and fully characterized using various techniques such as XRD, FTIR, SEM, EDS, and TGA. The resulting LDHs demonstrated a high affinity for efficiently removing tetracycline (TC) antibiotic from water, particularly at a moderate molar ratio of 3:1. This ratio exhibited improved structural characteristics, resulting in better TC uptake from water. The improved performance was supported by the increased abundance of surface functional groups (OH, NO 3 , CO 3 2- , C-O-C, Fe-O, and Al-O-Al). The TGA analysis established the high stability of the LDHs when subjected to high temperatures. The kinetics of TC adsorption onto LDH fitted with the PSO (R 2  = 0.935-0.994) and Avrami (R 2  = 0.9528-0.9824) models, while the equilibrium data fitted the Liu and Langmuir isotherm models, with maximum monolayer adsorption capacities of 101.1 mg g -1 and 70.83 mg g -1 , respectively-significantly higher than many reported values in the literature. The positive values of ΔH 0 and ΔS 0 indicate an endothermic process, with TC removal mechanisms influenced by physical interactions, such as hydrogen bonding, electrostatic interaction, and π-cation with the surface functional groups of the LDH adsorbents. These results suggest that LDH-MgAl and LDH-MgFe are promising adsorbents for the removal of TC from water.