Facile synthesis of magnetic ZnAl layered double hydroxides and efficient adsorption of malachite green and Congo red

Abstract

Excessive dye effluent has contaminated the ecosystem, and it is challenging to effectively remove dye from the aqueous system. In the present work, magnetic Zn-Al layered double hydroxides (MZA) was synthesized via co-precipitationmethod for the adsorption of malachite green (MG) and Congo red (CR) in the aqueous solution. The successful synthesis of MZA was characterized by SEM-EDS, XRD, FT-IR BET and VSM. The batch experiments were conducted to investigate the effect of various adsorption parameters on the adsorption capacity of MG and CR by MZA, such as MZA dosage, solution pH, etc. Further adsorption studies, kinetics, isotherm, and thermodynamic were performed to explore the adsorption behavior of MG and CR on MZA. The maximum adsorption capacity at 298 K for MG and CR on MZA were 850.93 and 279.09 mg/g, respectively. Adsorption kinetics followed the pseudo-second-order model. Adsorption thermodynamics showed spontaneous, endothermic for MG and CR adsorption on MZA. The electrostatic attraction, hydrogen bonding, and molecular intercalation mainly occurred during adsorption process. In addition, MZA exhibited higher adsorption capacityafter 4 cycles of continuous adsorption–desorption. In conclusion, MZA might be a potential adsorbent for purifying wastewater containing MG and CR.