Synthesis of CoZnAl‐layered double hydroxide/graphene oxide nanocomposite for the removal of methylene blue: Kinetic, thermodynamic, and isotherm studies

Abstract

The objective of this study was the synthesis of a novel nanocomposite (CoZnAl‐layered double hydroxide [LDH]/graphene oxide [GO]) to solve the adsorption problem of positively charged pollutants by LDHs. To prepare this nanocomposite, CoZnAl‐LDH and GO were synthesized by coprecipitation and modified Hummers methods, respectively. After ultrasonic pretreatment, they were combined to produce CoZnAl‐LDH/GO nanocomposite with a smooth and uniform texture which used to remove methylene blue as a cationic model pollutant. The synthesized nanocomposite showed a good adsorption capacity with the maximum adsorption capacity of 169.49 mg/g according to the Langmuir model. The effect of temperature on the adsorption process was surveyed by thermodynamic studies confirming the desirability and the spontaneity of the adsorption process. According to kinetic results, the pseudo‐second‐order model fitted the adsorption process, well. Meanwhile, it was determined that the adsorption process, especially in the beginning, had a high rate and 70% of the pollutant was removed within the first 5 min. Also, the effect of pH on the pollutant removal efficiency was investigated. Finally, the reusability of the nanocomposite was tested. High adsorption capacity and rate, the wide range of operational pH (4–10), and good reusability all suggest that CoZnAl‐LDH/GO is a promising adsorbent for industrial and practical uses.