Efficient Removal of Methyl Orange and Heavy Metal Ion from Aqueous Solution by NiFe-Cl-Layered Double Hydroxide

NiFe-layered double hydroxides (LDHs) with four different interlayer anions (NiFe-X-LDH, X=Cl-, NO3-, SO42-, and CO32-) were synthesized by a coprecipitation method. Their adsorption performance for methyl orange (MO) was first studied. It is found that the interlayer anions strongly affect the adsorption capacity, and adsorption amount of NiFe-X-LDH follows the order CO32-<SO42-<NO3-<Cl-, indicating that NiFe-Cl-LDH possesses the best MO adsorption property. Thus, effects of pH, solution temperature, contact time, and initial MO concentration on MO adsorption behavior of NiFe-Cl-LDH were further investigated systematically. It shows that the adsorbent presents good performance within the pH range of 5 to 6 and the adsorption capacity increases with the solution temperature. Thermodynamic data indicate that adsorption is spontaneous and endothermic. Weber's intraparticle diffusion model reveals that the adsorption includes two processes: external surface adsorption and intraparticle diffusion. Adsorption isotherm data are well fitted with the Langmuir model and the pseudo-second-order model, and the maximum MO adsorption capacity of NiFe-Cl-LDH is 769.23mg/g, which is larger than some classical LDHs. In addition, the NiFe-Cl-LDH also exhibits high adsorption performance for Cr (VI) (60.24mg/g) and As (III) (68.49mg/g). Results show that NiFe-Cl-LDH is a promising material for separation of pollutants from aqueous solutions.