Abstract
The goal of the present work is a comparative study of the effectiveness of the application of intergel systems and molecularly imprinted polymers for the selective sorption and separation of neodymium and scandium ions. The following physico-chemical methods of analysis were used in this study: colorimetry and atomic-emission spectroscopy. The functional polymers of polyacrylic acid (hPAA) and poly-4-vinylpyridine (hP4VP) in the intergel system undergo significant changes in the initial sorption properties. The remote interaction of the polymers in the intergel system hPAA–hP4VP provides mutual activation of these macromolecules, with subsequent transfer into a highly ionized state. The maximum sorption of neodymium and scandium ions is observed at molar ratios of 83%hPAA:17%hP4VP and 50%hPAA:50%hP4VP. Molecularly imprinted polymers MIP(Nd) and MIP(Sc) show good results in the sorption of Nd and Sc ions. Based on both these types of these macromolecular structures, principally new sorption methods have been developed. The method based on the application of the intergel system is cheaper and easier in application, but there is some accompanying sorption (about 10%) of another metal from the model solution during selective sorption and separation. Another method, based on the application of molecularly imprinted polymers, is more expensive and the sorption properties are higher, with the simultaneous sorption of the accompanying metal from the model solution.
Highlights
Nowadays, one of the elements highly in demand for industrial use is rare earth metals (REMs)
Monomers: acrylic acid (AA), methacrylic acid (MAA), and 4-vinylpyridine (4VP) were purchased from “LaborPharma” Ltd. (Almaty, Kazakhstan); linear polymer: poly4-vinylpyridine (P4VP); cross-linking agents: N,N -methylenebis(acrylamide) (MBAA), epichlorohydrin (ECH), and ethyleneglycol dimethacrylate (EGDMA); initiator: azobisisobutyronitrile (AIBN); redox system: K2S2O8–Na2S2O3; solvent: dimethylformamide (DMFA); porogen: toluene; stabilizer: hydroxyethylcellulose (HEC). the rest of mentioned chemicals were purchased from Sigma-Aldrich company (Saint-Louis, MO, USA)
Stages of mutual activation of PAA and P4VP hydrogels are presented on Figure 5
Summary
One of the elements highly in demand for industrial use is rare earth metals (REMs). The increased importance of REMs over the last 100 years is due to their unique properties, which have no existing analogues. This fact can be seen from the rate of annual growth of 13.7% (expected growth between 2017 and 2021) for the global REM market [1,2,3,4,5]. Most of the REMs are lanthanoids and their chemical properties are similar. These metals occur together within minerals in varying quantities [7]. The main factors that can impact the market are the increase of REM production from existing mines, development of mine prospects advanced during price spikes, research and development efforts focused on improving REM recoveries, recycling, substitution, alternate sources of REMs, and governmental policies [12,13,14]
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