Comparative adsorption of methyl orange on SO₄^2- and SDS intercalated Mg-Fe layered double hydroxides

ABSTRACT

This work investigates the synthesis of Mg-Fe layered double hydroxides intercalated by sulphate (Mg-Fe-SO₄) or dodecylsulfate (Mg-Fe-SDS) and their capacity to adsorb methyl orange (MO), as a model textile dye, from an aqueous solution. The synthesised materials were characterised by XRD, FTIR, TEM, ICP-OES, elemental chemical analysis (CHNSO), and pH point of zero charge (pH_PZC). XRD patterns showed that Mg-Fe-SDS has an interlayer spacing bigger than that of Mg-Fe-SO₄. FTIR spectra confirmed the presence of intercalated anions in the LDH matrix. Batch experiments for MO adsorption onto synthesised samples were investigated under various conditions such as solution pH, equilibrium time, initial dye concentration, and temperature. Langmuir, Freundlich, and Dubinin–Radushkevich isotherm models were used to determine the equilibrium parameters. The pseudo-second-order kinetics models was appropriate to examine the kinetic data. The Langmuir model fits well with the experimental adsorption data with high adsorption efficiency of Mg-Fe-SDS compared to Mg-Fe-SO₄. The thermodynamic parameters indicate that the adsorption of MO on both Mg-Fe-SDS and Mg-Fe-SO₄ was an endothermic and spontaneous physical process. The adsorption ability of MO onto LDHs was practically influenced by pH solution. The maximum adsorption capacities were 614.23 and 325.65 mg/g for Mg-Fe-SDS and Mg-Fel-SO₄, respectively. The adsorption tests recommend the use of organic LDHs as potential adsorbents for azo dye.

KEYWORDS:

• Textile dyes removal
• layered double hydroxides
• intercalation
• thermodynamics

Disclosure statement

No potential conflict of interest was reported by the author(s).