Abstract
The fabrication of Mg-Zn-Al Hydrotalcite (HT) was carried out by the co-precipitation method at various molar ratios. The Mg-Zn-Al HT compound at the optimum molar ratio was then calcined to determine the effect of calcination on the Pb2+ adsorption. The kinetics of the adsorption type was determined by applying pseudo first order and pseudo second order kinetics models. Meanwhile, to investigate the adsorption process, the Freundlich and Langmuir equations were applied to determine the adsorption isotherm. The results showed that the optimum Mg-Zn-Al HT was at a molar ratio of 3 : 1 : 1 with an adsorption efficiency of 73.16 %, while Mg-Zn-Al HT oxide increased the adsorption efficiency to 98.12 %. The optimum condition of Pb2+ removal using Mg-Zn-Al HT oxide was reached at pH 5 and a contact time of 30 minutes. The adsorption kinetics follows the pseudo second order kinetics model with a rate constant of 0.544 g/mg·min. The isotherm adsorption follows the Langmuir isotherm model with a maximum capacity of 3.916 mg/g and adsorption energy of 28.756 kJ/mol.
Highlights
Hydrotalcite compounds (HT), which are known as Layered Double Hydroxides (LDH) or anionic clays, is are layered materials that have an anion exchange capacity and a large surface area [1,2,3,4]
Some researchers applied the HT for a metal cation adsorption including an adsorption of In3+ by Zn-Al LDH [9], adsorption of Cr6+ using Mg-Al LDH, Ni-Al LDH and Zn-Al LDH [10]
The previous study shows that the HT is a potential adsorbent for Pb2+, even though the HTs bear a positive charge on the hydroxide layer
Summary
Hydrotalcite compounds (HT), which are known as Layered Double Hydroxides (LDH) or anionic clays, is are layered materials that have an anion exchange capacity and a large surface area [1,2,3,4]. The replacement of several M(II) by M(III) cations in the HT structure causes the hydroxide layer to be of an excess positive charge. If the metal oxide is dispersed into water, it will re-construct the HT layered structure. This is named as the memory effects. This unique character causes the HT to be widely used as adsorbent, such as namely for heavy metal pollutants [3, 5]. Several methods have been applied to reduce the lead metal content from in a liquid waste, such as precipitation method, ion exchange, electrolysis, membrane filtration, and adsorption [17, 18].
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