Enhancement of Congo red dye removal efficiency using Mg-Fe-layered double hydroxide

In this study, Mg-Fe(II)-Al-layered double hydroxide with different molar ratios Fe/Al (Mg0.80-Fe0.14-Al0.06-LDHs and Mg0.80-Fe0.20-Al0.00-LDHs) was prepared via a co-precipitation method at pH constant of 9.5 for a potential application as an efficient Congo red dye removal. The products are characterized by X-ray diffraction, Fourier transform infrared spectroscopy, Brunauer–Emmet–Teller, and X-ray photoelectron spectroscopy. The X-ray diffraction patterns showed that both Mg-Fe-Al-LDHs synthesized with two molar ratios Fe/Al were successfully synthesized without significant impurities. The surface area of Fe-LDHs was about 98 m2/g. The prepared Mg0.80-Fe0.14-Al0.06-LDHs was utilized for the removal of Congo red (CR) dye. Different parameters such as composite dosage, solution pH, contact time, and initial dye concentration were used to evaluate the adsorption process of CR dye. The results indicated that the optimal dose and contact time were 0.05 g and 5 min, respectively. The CR dye adsorption capacity increased with the increase of initial pH from 5 to 7. The isotherm and kinetics models of adsorption were studied. The adsorption kinetic fits the pseudo-second-order kinetic model with a high degree of correlation coefficient. The adsorption isotherm describes an appropriate fit to the Langmuir model with a maximum adsorption qm around 11 mg/g. The mechanism interaction study of CR dye molecule on Fe-LDHs was discussed, and it can be attributed to the existence of different forces as hydrogen bonding and electrostatic attraction.