Adsorption study of Congo red dye from aqueous solution to Mg–Al–layered double hydroxide

• Congo red (CR) in water was adsorbed by Mg–Al–LDH.
• LDH with metal cations and interlayer anions were synthesized.
• Electrostatic attraction was suggested to control CR adsorption on Mg–Al–LDH.

The removal of Congo red (CR), an anionic dye, by adsorption method was investigated using Mg–Al–layered double hydroxide. The Mg–Al–LDH was prepared using method involving coprecipitation with Mg2+/Al3+ molar ratio of 2 at constant pH of 9. The solid characterized by X-ray diffraction, IR spectroscopy and was well crystallized. The effects of different parameters on adsorption such as pH, contact time, concentration of dye on the efficiency of CR adsorption onto Mg–Al–LDH were investigated. The adsorption kinetics fit the pseudo-second order kinetic models well and isotherms correspond to Langmuir model strictly. The thermodynamic parameters have been calculated, and the adsorption process was found to be spontaneous, endothermic in nature and the electrostatic attraction was suggested to control CR adsorption on Mg–Al–LDH.

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