Abstract
The recoveries of Sr2+ and La3+ as rare earth metals (REMs) were studied using Mg-aminoclay-humic acid [MgAC-HA] complexes prepared by self-assembled precipitation due to electrostatic attraction between water-solubilized [MgAC] and water-soluble [HA], and were compared with the recoveries using [MgAC] and [HA]. The influences of pH and Sr2+ and La3+ concentrations in single and binary systems were evaluated. The adsorbents before/after adsorption of Sr2+ and La3+ were characterized by (1) scanning electron microscopy (SEM) micrographs, (2) Fourier transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS), and extended X-ray absorption fine structure (EXAFS) spectra, and by (3) powder X-ray diffraction (XRD) pattern analysis. After fitting Langmuir and Freundlich isotherms, the Langmuir model was found to present better matches than the Freundlich one: the maximum adsorption capacities of Sr2+ and La3+ were 0.12 mg g-1 and 4.76 mg g-1 in the binary system at room temperature, and the optimal recovery pH was ∼8.0. In practical seawater meanwhile, the recoveries of Sr2+ and La3+ by [MgAC-HA] complexes were the highest in the binary system. However, with further recycling runs, the recoveries of Sr2+ and La3+ were critically diminished due to disassembly in [MgAC-HA] complexes under acidic conditions. Thus, for the purposes of industrial application, we are currently pursuing the enhancement of recyclability for [MgAC-HA] complexes by their encapsulation or direct hydrogel formation.
Original language | English |
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Pages (from-to) | 1324-1332 |
Number of pages | 9 |
Journal | RSC Advances |
Volume | 6 |
Issue number | 2 |
DOIs | |
State | Published - 2016 |
Bibliographical note
Publisher Copyright:© The Royal Society of Chemistry 2016.