Characteristics and mechanisms of methyl orange sorption onto Zn/Al layered double hydroxide intercalated by dodecyl sulfate anion

Zn/Al layered double hydroxides (LDHs) intercalated by dodecylsulfate and carbonate were synthesized using a hydrothermal method without calcination. The prepared material was used as adsorbents for the removal of the anionic azo dye, methyl orange (MO), from aqueous solution. The Zn/Al LDHs containing carbonate (Zn-AlCO3) and an anionic surfactant, sodium dodecylsulfate (SDS) (Zn-AlDs) were characterized by XRD, TEM, FT-IR, elemental analysis and TGA-TDA techniques. XRD patterns of Zn-AlDs and Zn-AlCO3 had a possibility to intercalate into the interlayer structure with a basal spacing of 1.262 and 0.758 nm, respectively. TEM observation showed that the LDHs displayed nanoscale particles. The presence of the desired anion in gallery space was confirmed by FTIR analysis. Adsorption tests for MO were performed as a function of solution pH, initial dye concentration, and contact time. The adsorption comportment onto Zn-AlCO3 was practically influenced by solution pH. However, the adsorption capacity of MO by Zn-AlDs was stable at the different varieties of pH solution. As the MO concentration increased, the form of a curve of removal capacity became L-type onto carbonate-containing LDHs and the S-type for organic LDH. XRD and FTIR analyses after MO retention indicates that the adsorption behavior for the organic compound was suggested by the dissolution of MO in a hydrophobic structure (adsolubilization). The adsorption results proposed that organic LDHs could be used as potential adsorbents for azo dye treatment in a wide range of pH. (c) 2019 Published by Elsevier B.V. on behalf of African Institute of Mathematical Sciences / Next Einstein Initiative. This is an open access article under the CC BY-NC-ND license. (http://creativecommons.org/licenses/by-nc-nd/4.0/)