High performance of Zn–Al–CO3 layered double hydroxide for anionic reactive blue 21 dye adsorption: kinetic, equilibrium, and thermodynamic studies

Abstract

The main objective of this study was to examine the adsorption of an anionic dye on LDH adsorbent. Layered double hydroxides (LDH) Zn–Al with a molar ratio Zn/Al = 2 (Zn–Al–CO3 LDH) was prepared by a simple co-precipitation method. The adsorption performance of Zn–Al–CO3 LDH was evaluated for the removal of anionic reactive blue 21 dye (RB21). To determine optimal conditions, batch adsorption experiments were conducted to study the effects of pH, contact time, Zn–Al–CO3 LDH quantity, and initial RB21 concentration on the removal process. It has been found that Zn–Al–CO3 LDH can achieve the elimination of 100% of RB21 (10 mg/L) after 30 min. The maximum adsorption capacity reached by Zn–Al–CO3 LDH was 212.97 mg/g. The results also showed that the kinetics and equilibrium of the RB21 dye adsorption onto Zn–Al–CO3 LDH is well-described by the pseudo-first-order kinetic and Langmuir models, respectively. The thermodynamic parameters indicate that the RB21 adsorption onto Zn–Al–CO3 LDH is governed by physisorption.