Highly efficient removal of three red dyes by adsorption onto Mg–Al-layered double hydroxide

The Mg–Al-CO 3 -LDH with Mg 2+ /Al 3+ molar ratio of 2 was prepared via coprecipitation method at constant pH of 9–10 and used to remove three red dyes by batch adsorption method. The results showed the Mg–Al-LDH were well crystallized and can adsorb the red dyes effectively. The optimal adsorbent dosage and contact time were 1.0   g and 60   min, respectively. Adsorbed amount hardly changed when pH   <   10. The adsorption kinetics fit the pseudo-second order kinetic models well and isotherms correspond to Langmuir model strictly. All the relevant mechanisms were studied and manifested as anion exchange and also electrostatic attraction for CR.