Removal of methyl orange dye from water to zinc-aluminium-chloride layered double hydroxides

Layered double hydroxides (LDHs) or hydrotalcite-like compounds with Zn and Al in the layers and chloride in the interlayer, was prepared following the coprecipitation method at constant pH. The affinity of this material with a hazardous dye Methyl Orange (MO) was studied as a function of contact time, initial pH of the solutions and initial dye concentration. It was found that 8h is enough time for the equilibrium state to be reached in OM adsorption. OM removal was independent of the initial pH. The adsorption isotherm, described by the Langmuir model, are of L-type. The results, demonstrate that the MO adsorption on LDHs occurs by both adsorption on external surface and interlayer ion exchange. A mechanism for removal of MO anion has been confirmed by X-ray diffraction and IR spectroscopy.