Preparation of layered double hydroxides with different divalent metals for the adsorption of methyl orange dye from aqueous solutions

Abstract

In this study, layered double hydroxides (LDHs) with different divalent metal cations were prepared and then utilized as adsorbent for the removal of dye from aqueous solutions. LDHs are positively charged lamellar solids consisting of divalent and trivalent metallic cations and exchangeable interlayer anions. The potential combinatorial series of M/aluminum (M = Ca, Mn and Zn) LDHs for the removal of methyl orange (MO) dye from aqueous solutions were investigated. LDHs were synthesized via a co-precipitation method and characterized using powder X-Ray diffraction (PXRD) and Fourier-transform infrared spectrophotometer (FTIR). The LDHs were then used as adsorbent for the removal of MO dye at different LDH dosages. As the LDH dosage increased, the removal percentage of MO dye also increased. CaAl, MnAl and ZnAl LDHs were able to adsorb up to 96.6%, 97.9% and 99.8% of MO dye, respectively, after being put in contact with the LDHs for 24h. Their adsorption ability was further analyzed by using Langmuir and Freundlich isotherm models in which the adsorption mechanism was determined. Adsorption of MO by CaAl, and ZnAl LDHs was governed by the Langmuir isotherm model while the adsorption data for MnAl LDH was found to fit well with the Freundlich isotherm model.