Some technological solutions contain valuable components and can become an additional source of rare-earth elements to satisfy the current production demands. This research provides the study on using a combination of polyacrylic acid hydrogel (hPAA) and hydrogel of poly-4-vinylpyridine (hP4VP) in different molar ratios for praseodymium ions sorption from its nitrate solution. The mutual activation of the hydrogels in an aqueous medium provides their transformation into a highly ionized state by the conformational and electrochemical changes in properties during their remote interaction. The electrochemical properties of solutions were studied by the methods of electrical conductivity, and pH measurements of the solutions. The research showed that the maximum activation of hydrogels was revealed within the molar ratio of hPAA:hP4VP equal to 1:5. Moreover, the total praseodymium ions sorption degree after 24 hours of sorption by individual hPAA and hP4VP was 54 % and 47 %, respectively, whereas the praseodymium ions sorption degree by the hPAA–hP4VP intergel system in the molar ratio 1:5 became 62 %. A slight increase in the sorption degree of praseodymium ions by the intergel system in comparison with individual hydrogels can be explained by the achievement of a higher ionization degree of hydrogels being activated in the hPAA–hP4VP interpolymer system by the remote interaction effect.
The aim of the work is to provide a comparative study of influence of ionic radii of neodymium and scandium ions on their sorption process from corresponding sulfates by individual ion exchangers Amberlite IR120, AB-17-8 and interpolymer system Amberlite IR120-AB-17-8. Experiments were carried out by using the following physicochemical methods of analysis: conductometry, pH-metry, colorimetry, and atomic-emission spectroscopy. Ion exchangers in the interpolymer system undergo remote interactions with a further transition into highly ionized state. There is the formation of optimal conformation in the structure of the initial ion exchangers. A significant increase of ionization of the ion-exchange resins occurs at molar ratio of Amberlite IR120:AB-17-8 = 5:1. A significant increase of sorption properties is observed at this ratio due to the mutual activation of ion exchangers. The average growth of sorption properties in interpolymer system Amberlite IR120:AB-17-8 = 5:1 is over 90% comparatively to Amberlite IR120 and almost 170% comparatively to AB-17-8 for neodymium ions sorption; for scandium ions sorption the growth is over 65% comparatively to Amberlite IR120 and almost 90% comparatively to AB-17-8. A possible reason for higher sorption of neodymium ions in comparison with scandium ions is maximum conformity of globes of internode links of Amberlite IR120 and AB-17-8 after activation to sizes of neodymium sulfate in an aqueous medium.
The escalating demand for rare earth metals (REM) in situations of limited availability has spurred scientists to seek alternative sources of REM, such as industrial waste solutions. This paper investigates the potential for improving the sorption activity of readily available and inexpensive ion exchangers, specifically the interpolymer systems “Lewatit CNP LF and AV-17-8”, towards europium and scandium ions, in comparison to the unactivated ion exchangers. The sorption properties of the improved sorbents (interpolymer systems) were evaluated using conductometry, gravimetry, and atomic emission analysis. The results demonstrate that the “Lewatit CNP LF:AV-17-8” (5:1) interpolymer system exhibits a 25% increase in europium ion sorption compared to the raw Lewatit CNP LF (6:0), and a 57% increase in europium ion sorption compared to the raw AV-17-8 (0:6) ion exchanger after 48 h of the sorption process. In contrast, the “Lewatit CNP LF:AV-17-8” (2:4) interpolymer system exhibits a 310% increase in scandium ion sorption compared to the raw Lewatit CNP LF (6:0), and a 240% increase in scandium ion sorption compared to the raw AV-17-8 (0:6) after 48 h of interaction. The improvement in europium and scandium ion sorption levels by the interpolymer systems, compared to the raw ion exchangers, may be attributed to the high ionization degree resulting from the remote interaction effect of the polymer sorbents as the interpolymer system in aqueous media.
The electrochemical behavior of macromolecules of commercial CNPLF and AB-17-8 ion exchangers under various initial states was analyzed by the methods of electrical conductivity and pH-meters. When considering ion exchangers in swollen states, with an increase in the ratio from cation exchanger to anion exchanger, significant changes are observed. The highest values of electrical conductivity are observed at 5:1 and 0:6, where at 5:1 the electrical conductivity of interpolymer systems is 2.5 times greater than at the minimum point at 5:1 (lewatit:anion exchanger), and about 2.0 times greater at 0:6 respectively. Due to the weak dissociation of H2O, the equilibrium will shift to the right. According to the Le Chatelier principle, additional H+ ions appear in the aquatic environment, the concentration of which increases to a ratio of 5:1. In the case of Lewatit˂AB-17-8, another equilibrium sets in, in which OH-groups are spent to neutralize H+ ions. To restore the concentration of OH- ions, the anion exchanger AV-17-8 additionally dissociates. The transition region at a ratio of 2:4 indicates that AB-17-8 is a stronger polyelectrolyte than lewatit. The minimum values are reflected in the equimolar state 3:3 (cation exchanger:anion exchanger). The difference between the minimum and maximum values reaches significant values. For example, at 0.08 hours, the χ value increases from 2 to 7, which is a 3.5-fold increase in electrical conductivity. The maximum electrical conductivity for the system CNPLFdry - AV-17-8sw is observed at a ratio of cation exchanger:anion exchanger 5:1. The minimum points are at ratios of 4:2 and 2:4. A distinctive feature of this system is the large difference between the maximum and minimum values, the values of which are higher than in the case of CNPLFsw - АВ-17-8sw. In the CNPLFsw - АВ-17-8dry system, the maximum areas were established at ratios of 3:3 and 2:4. The values of the maximum electrical conductivity are observed during the interaction of 30 hours. Minimal χ is observed at 0.08 hours. Thus, the obtained experimental results on χ and pH measurements for interpolymer systems consisting of dry and swollen ion exchangers indicate that changes in the initial state of one of the components significantly change the electrochemical behavior of ion exchangers and interpolymer systems, which affects the applied properties of industrial ion exchangers.
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