Flower‑Like Layered Double Hydroxides for the Adsorption of Azocarmine G: Kinetic, Isotherm, and Thermodynamic Studies

Abstract

The current research includes the adsorp- tion behavior of two flower-like layered double hydroxides (MgAl-LDH and MgFe-LDH) synthe- sized via co-precipitation method for the environ- mental remediation. The synthesized materials were characterized by several techniques like X-ray diffrac- tion (XRD), Fourier Transform Infrared spectrom- etry (FTIR), scanning electron microscopy (SEM), Thermogravimetric analysis (TGA), differential ther- mogravimetry (DTG), and differential scanning calo- rimetry (DSC). The materials were also characterized by Brunauer-Emmett-Teller (BET) technique, and the obtained surface areas were 65.50 m2 ·g−1 and 51.43 m2 ·g−1 for MgAl-LDH and MgFe-LDH, respectively. The materials were tested for the adsorption removal of azocarmine G dye from aqueous medium; the experimental parameters, including the pH, the initial concentration, the adsorbent dose, and the time, were optimized to attain a maximum adsorption capacity of 105.9 mg·g−1 and 101.6 mg·g−1 for MgAl-LDH and MgFe-LDH, respectively, which confirms that the materials can be used for the effective dye removal. The kinetic study revealed that the pseudo-second order fitted well the adsorption process, and the iso- therms conformed well to the Langmuir model. The effect of temperature allowed to calculate the follow- ing thermodynamic parameters: ΔHMgAl°=12.083 KJ·mol−1 ; ΔHMgFe°=25.053 KJ·mol−1 ; ΔSMgAl°=43.81 JK−1 ·mol−1 ; and ΔSMgFe°=87.75 JK−1 ·mol−1 .