The extraction behaviors of the functionalized ionic liquid [A][BDGA] on light rare earths were investigated to make a preliminary inference of the extraction mechanism.kinglapassgraphen.gq/minor-keys.php
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The studies involved optimization of the chromatography parameters, including the acidity of the eluent, the amount of stationary phase and the diameter of the column. All of the chemicals and reagents used in this study were of analytical grade. Nitric acid, dichloromethane, Aliquat , sodium nitrate, diglycolic anhydride, n-dioctylamine, n-dibutylamine and sodium hydroxide were purchased from Sinopharm Chemical Reagent Co. The triethylamine was freshly distilled from calcium hydride before use. Highly pure oxides of lanthanum, cerium, praseodymium, neodymium and other rare earths were kindly provided by the Baotou Research Institute of Rare Earths.
The rare earth nitrates were prepared by dissolving the pure oxides into nitric acid and then diluting to a certain volume by deionized water. Aliquat is considered here as trioctylmethylammonium chloride or tricaprylmethylammonium chloride. Chromosorb-W dimethyl dichlorosilane- treated acid washed celite diatomaceous silica, mesh size — was procured from Sinopharm Chemical Reagent Co. The residue was recrystallized from toluene to give the diglycolic anhydride as a white solid. An amounts of Then, the reaction mixture was stirred for 3 h.
The 1,4-dioxane was distilled and the crystal appeared when hydrochloric acid was dropped into the residual solution. A nearly quantitative yield was obtained. The characterization of the products is shown as follows. The extraction studies were carried out in centrifuge tubes of 10 mL at K. A volume of 2. The mixture was then centrifuged for 3 min at rpm to enhance phase separation. The results were reported as mean values. A certain amount of [A][BDGA] was diluted in ethanol and was mixed with Chromosorb-W and then equilibrated for 24 h in a mechanical shaker. The solvent of the suspension was removed by rotary evaporation.
The resultant material was vacuum dried to constant weight. The extraction column was prepared by slurry packing a certain mass of chromatographic resin material in a glass chromatographic column of 15 mm diameter. After that, the HNO 3 solution eluted the column with a constant flow rate of 1. The breakthrough curves were obtained and analyzed. As shown in Table 1 , the diglycolamide extractants exhibited high distribution ratios under high acidity, while the ionic liquids showed almost no extraction ability.
On the contrary, the results indicated that the distribution ratios of the ionic liquids were much higher than those of the diglycolamide extractants under low acidity in Table 2. In addition, by combining the results in both Tables 1 and 2 , it was found that when the acidity varied from high acidity to low acidity, the distribution ratios of the diglycolamide extractants decreased. However, those of the ionic liquids increased conversely.
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It also cannot be ignored that the butyl groups showed a positive effect on the extraction ability in both diglycolamide and ionic liquids extractants. Therefore, significant research has been focused on the excellent extraction ability of TODGA, and not only investigating its extraction behaviors, but also developing its applications, such as supplied liquid membranes and extraction chromatography. In general, the decreased incomplexing ability of diglycolamides with long alkyl chains to rare earths could be explained by steric hindrance caused by bulky substituents [ 5 , 26 , 27 ].
In order to explain the mechanism clearly, the effect of the concentration of [A][BDGA] was investigated. Through the linear regression analyses of the extraction data, four straight lines with slopes of 2. Fig 3 shows that the acidity has a negative effect on rare earth extraction.
This result was in agreement with the results from Tables 1 and 2. As showed in Fig 3 , linear regression analyses of the extraction data resulted in four straight lines with slopes of The date of the acidity can be seen in S1 File. The relationship between the distribution ratios of the trivalent lanthanides with the ionic liquid extractant [A][BDGA] in a nitric acid medium and their atomic numbers were also investigated, with the results provided in Fig 4.
The hydration energy of the Ln III ions and the degree of the basicity of the extractant to dehydrate Ln III ion may play an important role in extraction [ 21 ]. The date of the distribution ratio can be seen in S1 File. On the contrary, as reported by Guo et al. Alternatively, the extraction sequence of Ln III was also attributed to its ionic radius. This result can be related to the hydration energy of the Ln III ion during extraction [ 21 , 28 ].
As shown in Fig 5 , with increasing HNO 3 concentration from 0. It was found that when the HNO 3 concentration was lower than 0. However, when the HNO 3 concentration increased to 0. Based on the above analysis, an extractant chromatographic strategy to realize the mixed RE III separation was made, considering the acidity as the most important factor.
In practical application, the stability and recycling of the extractants are the most important required factors.
The extractant was recycled three times. The results are showed in Table 3 , which indicated that the loss of the extraction efficiency was almost negligible and the extractants could be reused. According to the investigation above, an extraction chromate graphic strategy can be explored through using the functionalized ionic liquid [A][BDGA] as the stationary phase. The acidity of the eluent, the amount of the stationary phase and the diameter of the column were taken into consideration as the experimental conditions to be optimized. The results showed that the acidity could obviously affect the separation of rare earths.
The retention time became shorter with increasing acidity of the eluent, which corresponds with the above study of the extraction behavior. However, the best separation condition was obtained with 0. Additionally, the diameter of the column and the amount of the stationary phase in the column could affect the efficient separation of light rare earths.
Therefore, this extraction chromatographic strategy can not only achieve satisfied separation but can also be friendly to the environment because of the low consumption of acid. The date of the elution volume can be seen in S1 File. As a result, the ionic liquid extractants showed better extraction ability than the diglycolamide extractants in low acidity and the butyl group performed better in extracting in both diglycolamide and ionic liquid extractants, which suggested that [A][BDGA] is a good extractant in low acidity.
The extraction mechanism was preliminarily inferred by studying its extraction behaviors on the REs III. With 0. In addition, the stripping and recycling studies indicated that the ionic liquid extractant [A][BDGA] could be reused. In conclusion, [A][BDGA] has the merits of high selectivity and low acid consumption in light rare-earths extraction and separation. This would be a positive factor in industry applications. Browse Subject Areas?
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Click through the PLOS taxonomy to find articles in your field. Introduction The rare earths REs , which comprise scandium, yttrium and the lanthanide metallic elements, are widely used in not only traditional industries but also modern material industries, since they show excellent luminescence, electronic, magnetic and thermological properties.
Download: PPT. Fig 1. Materials and methods Materials and reagents All of the chemicals and reagents used in this study were of analytical grade. Extraction procedure The extraction studies were carried out in centrifuge tubes of 10 mL at K. Column studies The extraction column was prepared by slurry packing a certain mass of chromatographic resin material in a glass chromatographic column of 15 mm diameter. Table 1. Table 2.
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Effect of acidity Fig 3 shows that the acidity has a negative effect on rare earth extraction. Extraction of other Ln III from nitric acid medium The relationship between the distribution ratios of the trivalent lanthanides with the ionic liquid extractant [A][BDGA] in a nitric acid medium and their atomic numbers were also investigated, with the results provided in Fig 4. Fig 4. Fig 5. Cheng, W. Fan, et al. Today, , Log In for instructions on accessing this content. Skip to main content. Home : Conference Presentations.
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