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

• Mg–Al-LDH was well crystallized and highly efficient in removing three red dyes.
• The adsorption rate of the red dyes by Mg–Al-LDH was fast and reached equilibrium after 60 min.
• The three red dyes were adsorbed by Mg–Al-LDH via anion exchange, also by electrostatic forces of attraction for congo red.

The Mg–Al-CO3-LDH with Mg2+/Al3+ 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.

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