Solvent extraction is the main method used to separate and purify rare earth elements.In the process of rare earths extraction,emulsification often generated due to the instability of the aqueous and organic phases or...Solvent extraction is the main method used to separate and purify rare earth elements.In the process of rare earths extraction,emulsification often generated due to the instability of the aqueous and organic phases or improper operating conditions.Once emulsification occurs,it would not only lead to low rare earths recovery efficiency,small product quantities,high production costs and the losing of extractant and rare earth resources,but also result in serious environmental pollution.Therefore,it is very important to study the micro-mechanisms of emulsification and establish new methods to prevent emulsification at the source.In this paper,possible factors resulting in emulsification,such as the compositions and properties of the organic and aqueous phases,the operating conditions of the rare earths extraction are reviewed.The micro-mechanisms of emulsification are summarized basing on the microscopic structures in the bulk phase,aggregations of the extractants at the organic-aqueous interface,spectral characterizations and computational simulations.On this basis,new formation mechanisms are proposed for emulsification.Preliminary explorations are employed to verify the correctness of these new viewpoints.Finally,future directions for studies of the emulsification micro-mechanism are proposed.This study provides a theoretical basis for further understanding the micro-mechanisms of interfacial instability resulting in emulsification in the process of rare earths extraction.展开更多
Enlarging the steric hindrance to the molecular structures of extractants is a common way to improve their selectivity.To improve the separation factor of thorium(Ⅳ)and cerium(Ⅳ),cyclic groups having large steric hi...Enlarging the steric hindrance to the molecular structures of extractants is a common way to improve their selectivity.To improve the separation factor of thorium(Ⅳ)and cerium(Ⅳ),cyclic groups having large steric hindrance such as phenyl,cyclohexyl,and benzyl were introduced into theα-aminophosphonate extractant molecules.Bis(2-ethylhexyl)((phenylamino)methyl)phosphonate(PAMP),bis(2-ethylhexyl)((cyclohexylamino)methyl)phosphonate(CAMP),and bis(2-ethylhexyl)((benzylamine)methyl)phosphate(BAMP)were synthesized and applied in the separation and recovery of thorium(Ⅳ)and cerium(Ⅳ)from sulfuric acid solution.The separation ability between cerium(Ⅳ)and thorium(Ⅳ)descends in the order of CAMP>BAMP≈Cextrant230>DEHAMP>>PAMP,which is consistent with the decreasing order of steric hindrance.Nearly non-extraction of both cerium(Ⅳ)and thorium(Ⅳ)and the lowest separation ability for PAMP will be due to the conjugation of the lone pair of the amino N atom and benzene ring in PAMP.Furthermore,the extraction of REs(Ⅲ)by CAMP is lower than that of thorium(Ⅳ).Thermodynamic parameters(ΔG^(0),ΔH^(0),ΔS^(0))and extraction equilibrium constants were determined.An extraction process was developed to separate and retrieve thorium(Ⅳ)and cerium(Ⅳ)from a bastnaesite leaching solution.The final product purity of CeO2and ThO2is 99%and 98.4%,respectively,and the yields are 90.2%and 97.6%,respectively.展开更多
Rational design of extractant structure to improve the extraction and separation capacity of rare earth elements(REEs)is a long-standing challenge.Herein,a new strategy was proposed to improve the stability of the che...Rational design of extractant structure to improve the extraction and separation capacity of rare earth elements(REEs)is a long-standing challenge.Herein,a new strategy was proposed to improve the stability of the chelating structure formed by malonamide and REEs.The stability of the chelating structure is greatly improved by using a double-ring framework structure which makes the two carbonyl groups of malonamide unable to rotate freely and both of them point to the metal ion position.Three benzyl groups were used to construct the hydrophobicity of the extractant and the organic shell of the extracted species.Tribenzylhexahydro-pyrrolo-pyridine-dione(THPPD)was designed and synthesized.The structure reduces the energy consumed by rotating carbonyl group in the coordination with metal ions and then improves the extraction ability of extractant.The crystal structure was preorganized as expected,with the two carbonyls pointing in a favorable coordination direction to the structural complement of the metal ion.The extraction behaviors of REEs with THPPD in a nitric acid medium were studied.Compared with N,N’-dibenzyl-N,N’-dimethylmalonamide(DBDM-MA)with a chain structure,the extraction capacity of THPPD is 360 times higher than that of DBDM-MA at 5.0 mol/L sodium nitrate.Furthermore,the binding energy and Gibbs free energy were investigated by density functional theory(DFT)in conjunction with the B3LYP.The theoretical results show that THPPD has more effective interaction with Pr(NO_(3))3 than DBDM-MA.The construction of chelating groups conformation is a worthy direction to improve the coordination ability and even selectivity of extractant.展开更多
In the petrochemical industry process, the relative volatility between the components to be separated is close to one or the azeotrope that systems are difficult to separate. Liquid-liquid extraction is a common and e...In the petrochemical industry process, the relative volatility between the components to be separated is close to one or the azeotrope that systems are difficult to separate. Liquid-liquid extraction is a common and effective separation method, and selecting an extraction agent is the key to extraction technology research. In this paper, a design method of extractants based on elements and chemical bonds was proposed. A knowledge-based molecular design method was adopted to pre-select elements and chemical bond groups. The molecules were automatically synthesized according to specific combination rules to avoid the problem of “combination explosion” of molecules. The target properties of the extractant were set, and the extractant meeting the requirements was selected by predicting the correlation physical properties of the generated molecules. Based on the separation performance of the extractant in liquid-liquid extraction and the relative importance of each index, the fuzzy comprehensive evaluation membership function was established, the analytic hierarchy process determined the mass ratio of each index, and the consistency test results were passed. The results of case study based on quantum chemical analysis demonstrated that effective determination of extractants for the analysis of benzene-cyclohexane systems. The results unanimously prove that the method has important theoretical significance and application value.展开更多
基金Project supported by the National Natural Science Foundation of China(52074031)the Key Research and Development Program of Shandong Province(ZR2021MB051,ZR2020ME256)the Open Project of Key Laboratory of Green Chemical Engineering Process of Ministry of Education(GCP202117)。
文摘Solvent extraction is the main method used to separate and purify rare earth elements.In the process of rare earths extraction,emulsification often generated due to the instability of the aqueous and organic phases or improper operating conditions.Once emulsification occurs,it would not only lead to low rare earths recovery efficiency,small product quantities,high production costs and the losing of extractant and rare earth resources,but also result in serious environmental pollution.Therefore,it is very important to study the micro-mechanisms of emulsification and establish new methods to prevent emulsification at the source.In this paper,possible factors resulting in emulsification,such as the compositions and properties of the organic and aqueous phases,the operating conditions of the rare earths extraction are reviewed.The micro-mechanisms of emulsification are summarized basing on the microscopic structures in the bulk phase,aggregations of the extractants at the organic-aqueous interface,spectral characterizations and computational simulations.On this basis,new formation mechanisms are proposed for emulsification.Preliminary explorations are employed to verify the correctness of these new viewpoints.Finally,future directions for studies of the emulsification micro-mechanism are proposed.This study provides a theoretical basis for further understanding the micro-mechanisms of interfacial instability resulting in emulsification in the process of rare earths extraction.
基金Project supported by the National Natural Science Foundation of China(92262301)。
文摘Enlarging the steric hindrance to the molecular structures of extractants is a common way to improve their selectivity.To improve the separation factor of thorium(Ⅳ)and cerium(Ⅳ),cyclic groups having large steric hindrance such as phenyl,cyclohexyl,and benzyl were introduced into theα-aminophosphonate extractant molecules.Bis(2-ethylhexyl)((phenylamino)methyl)phosphonate(PAMP),bis(2-ethylhexyl)((cyclohexylamino)methyl)phosphonate(CAMP),and bis(2-ethylhexyl)((benzylamine)methyl)phosphate(BAMP)were synthesized and applied in the separation and recovery of thorium(Ⅳ)and cerium(Ⅳ)from sulfuric acid solution.The separation ability between cerium(Ⅳ)and thorium(Ⅳ)descends in the order of CAMP>BAMP≈Cextrant230>DEHAMP>>PAMP,which is consistent with the decreasing order of steric hindrance.Nearly non-extraction of both cerium(Ⅳ)and thorium(Ⅳ)and the lowest separation ability for PAMP will be due to the conjugation of the lone pair of the amino N atom and benzene ring in PAMP.Furthermore,the extraction of REs(Ⅲ)by CAMP is lower than that of thorium(Ⅳ).Thermodynamic parameters(ΔG^(0),ΔH^(0),ΔS^(0))and extraction equilibrium constants were determined.An extraction process was developed to separate and retrieve thorium(Ⅳ)and cerium(Ⅳ)from a bastnaesite leaching solution.The final product purity of CeO2and ThO2is 99%and 98.4%,respectively,and the yields are 90.2%and 97.6%,respectively.
基金Project supported by the National Natural Science Foundation of China(21876062)Shandong Provincial Natural Science Foundation(ZR2022QB067)。
文摘Rational design of extractant structure to improve the extraction and separation capacity of rare earth elements(REEs)is a long-standing challenge.Herein,a new strategy was proposed to improve the stability of the chelating structure formed by malonamide and REEs.The stability of the chelating structure is greatly improved by using a double-ring framework structure which makes the two carbonyl groups of malonamide unable to rotate freely and both of them point to the metal ion position.Three benzyl groups were used to construct the hydrophobicity of the extractant and the organic shell of the extracted species.Tribenzylhexahydro-pyrrolo-pyridine-dione(THPPD)was designed and synthesized.The structure reduces the energy consumed by rotating carbonyl group in the coordination with metal ions and then improves the extraction ability of extractant.The crystal structure was preorganized as expected,with the two carbonyls pointing in a favorable coordination direction to the structural complement of the metal ion.The extraction behaviors of REEs with THPPD in a nitric acid medium were studied.Compared with N,N’-dibenzyl-N,N’-dimethylmalonamide(DBDM-MA)with a chain structure,the extraction capacity of THPPD is 360 times higher than that of DBDM-MA at 5.0 mol/L sodium nitrate.Furthermore,the binding energy and Gibbs free energy were investigated by density functional theory(DFT)in conjunction with the B3LYP.The theoretical results show that THPPD has more effective interaction with Pr(NO_(3))3 than DBDM-MA.The construction of chelating groups conformation is a worthy direction to improve the coordination ability and even selectivity of extractant.
基金supported by the National Natural Science Foundation of China(22178190).
文摘In the petrochemical industry process, the relative volatility between the components to be separated is close to one or the azeotrope that systems are difficult to separate. Liquid-liquid extraction is a common and effective separation method, and selecting an extraction agent is the key to extraction technology research. In this paper, a design method of extractants based on elements and chemical bonds was proposed. A knowledge-based molecular design method was adopted to pre-select elements and chemical bond groups. The molecules were automatically synthesized according to specific combination rules to avoid the problem of “combination explosion” of molecules. The target properties of the extractant were set, and the extractant meeting the requirements was selected by predicting the correlation physical properties of the generated molecules. Based on the separation performance of the extractant in liquid-liquid extraction and the relative importance of each index, the fuzzy comprehensive evaluation membership function was established, the analytic hierarchy process determined the mass ratio of each index, and the consistency test results were passed. The results of case study based on quantum chemical analysis demonstrated that effective determination of extractants for the analysis of benzene-cyclohexane systems. The results unanimously prove that the method has important theoretical significance and application value.
