A New Mg–Al–Cu–Fe-LDH Composite to Enhance the Adsorption of Acid Red 66 Dye: Characterization, Kinetics and Isotherm Analysis

Abstract

In this paper, a novel quadri-metal layered double hydroxide Mg–Al–Cu–Fe–CO3 (LDH) was synthesized by a co-precipitation method. Part of the synthesized LDH was subjected to calcination (CLDH) using thermal treatment under a temperature of $$550\,^{\circ }\hbox {C}$$ . The application of the synthesized material (LDH) as well as its derived product (CLDH) as adsorbents for the anionic dye Acid Red 66 (AR66) was investigated. The characterization of LDH and CLDH was done using several methods, such as X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analyses, $$\hbox {N}_{2}$$ adsorption desorption isotherms (BET), scanning electron microscopy, X-ray fluorescence spectrometry analysis XRF and zeta potential measurement. In addition to the kinetic and the equilibrium studies, the influences of different factors, the initial pH, the mass of adsorbent, the contact time, the ionic strength and the temperature were explored. The results revealed that the novel layered double hydroxide Mg–Cu–Al–Fe-LDH was an efficient adsorbent for AR66. The thermal treatment of LDH increased significantly the capacity of adsorption of anionic dye, from 125 to 920 mg g $$^{-1}$$ in natural conditions (natural pH, room temperature), due to the increase in pore size and also the memory effect of the CLDH after adsorption. The capacity of adsorption was susceptible to a further increase in acidic conditions or by addition of salts suggesting a positive impact of acid medium and competing anions on the adsorption mechanism. Kinetic data were accurately fitted by a pseudo-second-order model. Adsorption isotherms were well described by the Sips and Toth models. The thermodynamic study revealed that the adsorption of AR66 on both LDH and CLDH was spontaneous and endothermic.