The adsorption of Ga(III) and V(V) onto an amidoxime resin (LSC700) has been investigated. The parameters studied include the effects of contact time, initial metal ions concentration, and temperature by batch method. The adsorption capacity of the resin for Ga(III) and V(V) was found to be 29.24 and 22.60 mg/g, respectively. The adsorption kinetics of Ga(III) and V(V) onto LSC700 could be well elucidated with Lagergren-second-order equation. The Langmuir isotherm fitted the experimental data well, indicating a homogeneous adsorption. Thermodynamic parameters, involving ΔG, ΔH, and ΔS were also calculated from graphical interpretation of the experimental data. Negative values of ΔG indicated that adsorption processes for both metal ions onto LSC700 were spontaneous. The standard heats of adsorption ΔH were found to be endothermic, and the entropy change values ΔS were calculated to be positive for the adsorption. The adsorption mechanism of LSC700 toward Ga(III) was exploited using FT-IR spectroscopy indicating the formation of a complex between the amidoxime group of LSC700 and [Ga(OH)4]− through oxygen binding mode. Finally, a novel process for separation and recovery of gallium and vanadium from Bayer liquor was proposed.
Amidoxime is of broad interest as a functional group for extraction and separation of different metals from aqueous solution due to its high affinity for a wide range of metal ions. Resins which contain an amidoxime group have exhibited good extractive properties for gallium and are adopted as the most efficient adsorbent for the recovery of gallium from Bayer liquor. However, the coordination mechanism between the amidoxime functional group of the resin and Ga(III) in Bayer liquor is unclear so far. Here, to identify the preferred action and the binding motif when amidoxime binds with Ga(III), we performed density functional theory (DFT) calculations and subsequent FT-IR spectra analysis for the amidoxime resin before and after adsorption of Ga(III) in Bayer liquor. Single-crystal X-ray diffraction was also used to validate the prediction. The fully relaxed structure and binding energy calculations of a series of complexes containing acetamidoximate (AO − ) and gallium species, [Ga(OH) 4-x (AO − ) x ] − , showed that, of the three general binding motifs of the amidoxime group toward metal ions, complexes with oxygen binding motif I are more stable than complexes with chelate binding motif II or η 2 binding motif III; and Ga(III) in Bayer liquor prefers to coordinate with only one amidoximate rather than two or more amidoximates. The FT-IR spectrum of the resin after adsorption confirmed the coordination between Ga and oximido by the shifting of N−O and O−H stretching vibrations to higher wavenumber and the appearance of Ga−O stretching vibrations. No characteristic stretching band of Ga−N was found in the FT-IR spectra, indicating binding motifs II and III unlikely happened. Structural analysis of the single-crystal Xray diffraction date revaled that the amidoxime ligand is deprotonated at a single oxime oxygen atom and coordinates to one gallium atom only through this oxygen, confirming the oxygen binding motif. Accordingly oxygen binding mode I might be the main binding motifs of amidoxime toward Ga(III) in Bayer liquor, which validated the prediction of DFT calculations.
Electromagnetic fields have been widely applied in the field of materials processing, preparation, and analysis. The effectiveness during such processing is, however, highly dependent on the physics of the applied electromagnetic field as well as the electromagnetic responses from the materials. In order to improve the efficiency of electromagnetic field processing, understanding the fundamentals as well as the engineering of the corresponding electromagnetic effects is crucial. Focusing on metallic materials, this research gives a critical overview and discussion on different electromagnetic effects. Subsequently, the electromagnetic responses in different electromagnetic technologies are further discussed. Specifically, the industrial application potential for inclusion removal from liquid metals is evaluated and the energy coefficient is noticed to be substantially improved by increasing the magnetic flux density.
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