Optimized adsorption and effective disposal of Congo red dye from wastewater: Hydrothermal fabrication of MgAl-LDH nanohydrotalcite-like materials

Abstract

• MgAl-LDH was synthesized ideally using the hydrothermal method. • MgAl-LDH exhibited excellent adsorption capacity for CR dye compared with previously prepared LDH compounds and other sorbents. • The experimental adsorption data adequately fit the Langmuir isotherm model. • Pseudo-second-order kinetic model best represents the adsorption data. • The interaction mechanism of CR to the MgAl-LDH surface was strengthened by electrostatic attraction. The effectiveness of Congo red (CR) adsorption from aqueous solutions onto MgAl-layered double hydroxide (MgAl-LDH) nanosorbents was examined in this study. MgAl-LDH was synthesized using the hydrothermal method, and physicochemical characterization was performed via powdered X-ray diffraction, high-resolution transmission electron microscopy, Fourier transform infrared analysis, and zeta potential measurements. For optimum adsorption of CR onto the synthesized MgAl-LDH nanosorbent, the adsorption process was employed in batch experiments. Adsorption parameters, such as the adsorbent dosage, solution pH, contact time, and initial adsorbate concentration, vary with the adsorption kinetics and isotherm mechanism. The results of the batch experiments indicated rapid adsorption of CR dye from aqueous solutions onto MgAl-LDH during the first 30 min until equilibrium was achieved at 180 min with a dye concentration of 50 mg/100 mL and MgAl-LDH adsorbent dosage of 0.05 g. The experimental adsorption data fit adequately with the monolayer coverage under the Langmuir isotherm model ( R 2 = 0.9792), and showed the best fit with the pseudo-second-order kinetic model ( R 2 = 0.996). The change in zeta potential confirmed the effective adsorption interaction between the positively charged MgAl-LDH and the negatively charged CR molecules with electrostatic interactions. This work is distinguished by the successful hydrothermal preparation of MgAl-LDH in the form of homogenous nanoscale particles (∼100 nm). The prepared MgAl-LDH showed a high adsorption capacity toward anionic CR dye with a maximum adsorption capacity of 769.23 mg/g. This capacity is higher than those reported for other adsorbents in previous research.