Removal of methyl orange from aqueous solution by uncalcined and calcined MgNiAl layered double hydroxides (LDHs)

In this study, both uncalcined (MgNiAl–CO3) and calcined (MgNiAl–C) hydrotalcites were used in the adsorption of methyl orange (MO) from aqueous solution as an anionic dye in a batch system. Various conditions such as initial dye concentration, adsorbent dosage, contact time, solution pH, and temperature were investigated. The adsorption kinetics was studied using classic equations of pseudo-first-order, -second-order and intraparticle diffusion models. The dynamical data fit well with the pseudo-second-order kinetic model. The positive value of the changes in enthalpy (ΔH°), the negative value of Gibbs free energy (ΔG°), showed that the adsorption is endothermic and spontaneous for all the studied temperatures. The equilibrium adsorption data were analyzed using three non linear adsorption models: Langmuir, Freundlich and Redlich–Peterson. The results showed that Langmuir and Redlich–Peterson isotherms fit the experimental results very well with high correlation coefficients. The Langmuir isotherm model exhibited a maximum adsorption capacity qmax of 375 mg/g for the calcined MgNiAl–C. This result is of practical interest, with respect to the selection of sorbents, to optimize aquatic environment remediation technologies.

► Removal of dye from water and wastewaters using low cost adsorbents.
► Development of kinetic models.
► Testing of isotherms.
► Evaluation of thermodynamic parameters.