Water decontamination via the removal of Pb (II) using a new generation of highly energetic surface nano-material: Co+2Mo+6 LDH

CoMo(CO32-) layered double hydroxide of a highly energetic surface, as a new LDH consisting of divalent and hexavalent cations (M+2/M+6-LDH), was prepared by a homogeneous co-precipitation method. The structure and morphology of the prepared material was confirmed by several analytical techniques namely; X-ray diffraction analysis (XRD), X-ray fluorescence (XRF), Fourier transform infra-red (FT-IR) spectroscopy, differential scanning calorimetry and thermal gravimetric analysis (DSC-TGA), N-2 adsorption-desorption isotherm and scanning electron microscope (SEM). The highly energetic surface of the prepared LDH was demonstrated via the X-ray photoelectron spectroscopy (XPS). The surface energy is due to the formation of +4 surface charges in the brucite layer between Co+2 and Mo+6. The prepared LDH was applied as a novel adsorbent for the removal of Pb (II) from its aqueous solution at different experimental conditions of time, temperature and initial Pb (II) concentrations. The change of the Pb (II) concentrations; due to adsorption, was monitored by atomic absorption spectrophotometer (AAS). The maximum uptake of Pb (II) by the Co Mo LDH was (73.4 mg/g) at 298 K. The Pb (II) adsorption was found to follow Langmuir isotherm and pseudo second order model. The adsorption process was spontaneous and endothermic. The interference of other cations on the removal of the Pb (II) was studied. Na+ and K+ were found to increase the adsorption capacity of the Co Mo LDH toward Pb (II) while it was slightly decreased by the presence of Mn+2 and Cu+2. The synthesized LDH showed a great degree of recoverability (7 times) while completely conserving its parental morphology and adsorption capacity. The mechanism of the lead ions removal had exhibited more reliability through a surface adsorption by the coordination between the Mo+6 of the brucite layers and the oxygen atoms of the nitrates counter ions. (C) 2015 Elsevier Inc. All rights reserved.