Abstract
Ni-Al Layered double hydroxide (Ni-Al LDHs) with M<sup>2+</sup>: M<sup>3+</sup> (4:1) ratio was synthesized by co-precipitation method from nitrate salt solutions. The layered double hydroxide was characterized by Fourier transform infrared spectroscopy, X-Ray Diffraction, Energy Dispersive Spectroscopy/Scanning Electronic Microscopy. The influences of phase contact time, temperature and initial concentrations were investigated to optimize the conditions for maximum adsorption. The experimental data were analyzed by Langmuir and Freundlich isotherm models and fitted well with correlation coefficient values of 0.9996 and 0.9995 respectively. The thermodynamic parameters of Isosteric heat of adsorption (DH<sub>x</sub>), Activation energy (E<sub>a</sub>), Enthalpy change (DH<sup>o</sup>) and Entropy change (DS<sup>o</sup>) were calculated to be 18.1KJ/mol, 1.447KJ/mol, -7.135J/mol and 24J/molK respectively. The results shows that the adsorption process was spontaneous and exothermic.
Highlights
Layered double hydroxide (LDH) is a class of anionic clays with high anion exchange capacities which can be used as an effective adsorbent for the removal of variety of anionic pollutants
Scanning electron microscope (SEM) and Energy dispersive spectroscope (EDS) images of as-synthesized layered double hydroxides are presented in figure 1 & 2
The energy dispersive spectrograph before adsorption studies, figure 2(a), show the presence of metal ions used in the synthesis of the layered double hydroxides such as aluminium, sodium, and nickel and their percentage compositions
Summary
Layered double hydroxide (LDH) is a class of anionic clays with high anion exchange capacities which can be used as an effective adsorbent for the removal of variety of anionic pollutants. The most common method for the synthesis of LDHs is co-precipitation. The flexibility of layered double hydroxides has place premium on their applications in various fields including catalysis, photochemistry, pharmacy, adsorption etc. R. Perez, et al, 2006, Zaini, et al, 2011) In all these studies, calcination has been further done to the original LDH either to enhance the quality of crystals or increase the adsorption capacity which makes the process more expensive
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