CN113737030A - Method for separating rare earth by using water-soluble polymer complexing agent - Google Patents

Method for separating rare earth by using water-soluble polymer complexing agent Download PDF

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CN113737030A
CN113737030A CN202111000622.0A CN202111000622A CN113737030A CN 113737030 A CN113737030 A CN 113737030A CN 202111000622 A CN202111000622 A CN 202111000622A CN 113737030 A CN113737030 A CN 113737030A
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rare earth
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邱运仁
陈雨欣
卢丹丹
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Central South University
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Abstract

The invention discloses a method for separating rare earth by using a water-soluble polymer complexing agent. The method is characterized in that Phosphorylated Chitosan (PCS) is used as a complexing agent, and the mixed rare earth ion solution is separated by shear decomplexation coupling ultrafiltration by utilizing the difference of the shear stability of PCS-Re complexes generated by complexing PCS and different rare earth ions. The complex agent phosphorylated chitosan used in the invention has the advantages of large molecular weight, good hydration property, strong rare earth complexing ability and the like. The method for separating the rare earth ion solution has the outstanding advantages of high single-stage selective separation efficiency, green and environment-friendly process, no secondary pollution and the like, and can realize the regeneration of the water-soluble polymer complexing agent while separating the rare earth.

Description

Method for separating rare earth by using water-soluble polymer complexing agent
Technical Field
The invention belongs to the field of rare earth ion separation, and particularly relates to a method for separating rare earth by using a water-soluble polymer complexing agent.
Background
Rare earth elements are called industrial vitamins and play an important role in the fields of military industry, electronics, petrochemical industry and the like. The solvent extraction method is a rare earth separation method which is widely applied in the rare earth hydrometallurgy industry at present, has the advantages of large processing capacity and high reaction speed, but has some defects, such as low selective separation efficiency of rare earth; the extraction system has more stages, and the extraction system can reach dozens of stages or even hundreds of stages; part of the extractant needs to be subjected to rare earth extraction and back extraction under a strong acid condition, so that the consumption of acid and alkali is high, and secondary pollution is easily caused; the demand for organic solvent is large, so that the Chemical Oxygen Demand (COD) and the Biological Oxygen Demand (BOD) in the extraction phase are high, the post-treatment is difficult, and meanwhile, in order to improve the extraction capacity, ammonia water is usually adopted to saponify the organic phase, so that the ammonia nitrogen problem also troubles the rare earth industry for a long time.
Aiming at the defects of the solvent extraction method, the invention provides a method for separating rare earth ions by combining complexation-ultrafiltration with shearing and decomplexing coupling ultrafiltration so as to solve a series of existing problems. The complexing-ultrafiltration is to utilize water-soluble macromolecular polymer containing functional groups such as nitrogen, phosphorus, carbonyl and the like to complex with metal ions in a solution, select a proper ultrafiltration membrane and intercept and separate the metal ions by intercepting the polymer-metal complex. Shear-decomplexed ultrafiltration tends to produce large shear rates by creating a shear field in the membrane compartment, especially near the membrane face. When the membrane surface shear rate exceeds the critical shear rate of the polymer-rare earth complex, the polymer-rare earth complex is decomplexed to generate a polymer complexing agent and free rare earth ions, the decomplexed free rare earth ions penetrate through the ultrafiltration membrane, and the polymer complexing agent is intercepted by the ultrafiltration membrane. Because different polymer-rare earth complexes have different stability in a shear field, different metal ions can be accurately separated by adopting a shear decomplexed coupling ultrafiltration method through controlling the membrane surface shear rate. When all the complexes are decomplexed, the regeneration of the polymer complexing agent can be realized, and the regenerated complexing agent can be reused in the complexation-shearing decomplexation-ultrafiltration process. Compared with the traditional solvent extraction, the process is carried out in a water phase, an organic solvent is not needed, the cost is saved, and the problem of serious ammonia nitrogen pollution is solved; the high-selectivity separation of rare earth can be realized; the reaction process can be carried out under a near-neutral condition, so that the consumption of acid and alkali is greatly reduced, secondary pollution is avoided, and the green chemical concept is met.
Disclosure of Invention
The invention aims to provide a method for separating rare earth by using a water-soluble polymer complexing agent, which adopts neutral phosphorylated chitosan nPCS and acidic phosphorylated chitosan aPCS as the water-soluble polymer complexing agent;
wherein the chemical structural formula of nPCS is as follows:
Figure BDA0003235417220000021
aPCS has a chemical structural formula as follows:
Figure BDA0003235417220000022
in the structure, n is 1200-3000;
the phosphorylated chitosan has strong hydration capability and large molecular weight, and simultaneously contains P ═ O group and imino group in the structure, and the phosphorylation chitosan and other commonly used complexing agents such as sodium Polyacrylate (PAAS), acrylic acid-maleic acid copolymer (PMA) and the like have better rare earth complexing capability and rare earth selectivity under the synergistic action of the P ═ O group and the imino group, so that the phosphorylated chitosan is a rare earth complexing agent with excellent performance;
the method specifically comprises the following steps:
firstly, under the condition that the pH value is 3-7, adding a certain amount of neutral phosphorylated chitosan nPCS or acidic phosphorylated chitosan aPCS into a solution containing rare earth ions, and stirring for 0.5-2.5 h to ensure that the rare earth ions and the nPCS or the aPCS are fully complexed to form a PCS-Re complex; then, according to the difference of the shearing stability of different PCS-Re complexes under certain conditions, the separation of mixed rare earth ions and the regeneration of the complex agent phosphorylated chitosan are realized by adopting shearing decomplexation coupling ultrafiltration;
the dosage of the neutral phosphorylated chitosan nPCS or the acidic phosphorylated chitosan aPCS is determined by measuring the relationship between the mass ratio P/Re of the complexing agent to the rare earth ions and the rare earth ion retention rate R by adopting a complexing-ultrafiltration method: when complexation-ultrafiltration is carried out under a certain pH condition, the rare earth ion retention rate increases with the increase of P/Re, and when the maximum value of R is reached and does not increase with the increase of P/Re, the value is the critical P/Re value, and the addition amount of the complexing agent is determined according to the critical P/Re value;
the PCS-Re complex has the shear stability under certain pH condition, and the critical shear rate gamma of the PCS-Re complex is adoptedc(maximum shear rate that can be sustained by the PCS-Re complex being stable) according to the relationship between the membrane surface shear rate and the rare earth ion rejection rateDetermining: when the membrane surface shear rate is less than the critical shear rate of the PCS-Re complex, the PCS-Re complex is kept stable, and the retention rate of rare earth ions is kept unchanged; when the membrane surface shear rate is greater than the critical shear rate of the PCS-Re complex, the PCS-Re complex is decomplexed into the polymer complexing agent and the free rare earth ions, the free rare earth ions can permeate the ultrafiltration membrane, and the rejection rate of the rare earth ions is sharply reduced.
The method for separating rare earth by using the water-soluble polymer complexing agent is characterized by comprising the following steps of: using neutral phosphorylated chitosan nPCS as a complexing agent, and realizing the ordered separation of rare earth ions by adjusting membrane surface shear rate coupling ultrafiltration according to the difference of critical shear rates of different nPCS-Re complexes under certain pH and temperature conditions;
under the conditions of normal temperature and pH 5, when nPCS is used as a complexing agent, the critical shear rates of complexes nPCS-La, nPCS-Ce and nPCS-Nd formed by nPCS and La, Ce and Nd are respectively 8.86 multiplied by 104s-1、9.91×104s-1、1.09×105s-1. Firstly controlling the membrane surface shear rate to be 8.86 multiplied by 104s-1<γ<9.91×104s-1nPCS-La decomplexes, and La is separated by ultrafiltration; then controlling the membrane surface shear rate to be 9.91 multiplied by 104s-1<γ<1.09×105s-1nPCS-Ce decomplexes and is ultrafiltered to separate Ce; finally controlling the membrane surface shear rate gamma>1.09×105s-1The nPCS-Nd is subjected to decomplexing, Nd is separated by ultrafiltration, and regenerated nPCS is obtained at the same time, and can be used for continuously complexing rare earth ions;
under the conditions of normal temperature and pH 6, when nPCS is used as a complexing agent, the critical shear rates of complexes nPCS-La, nPCS-Ce and nPCS-Nd formed by nPCS and La, Ce and Nd are respectively 1.02 multiplied by 105s-1、1.21×105s-1、1.33×105s-1. Firstly controlling the membrane surface shear rate to be 1.02 multiplied by 105s-1<γ<1.21×105s-1nPCS-La decomplexes, and La is separated by ultrafiltration; then controlling the membrane surface shear rate to be 1.21 multiplied by 105s-1<γ<1.33×105s-1nPCS-Ce to break down the collaterals and exceedFiltering and separating Ce; finally controlling the membrane surface shear rate gamma>1.33×105s-1The nPCS-Nd is subjected to decomplexing, Nd is separated by ultrafiltration, and regenerated nPCS is obtained at the same time, and can be used for continuously complexing rare earth ions;
under the conditions of normal temperature and pH value of 7, when nPCS is used as a complexing agent, the critical shear rates of complexes nPCS-La, nPCS-Ce and nPCS-Nd formed by nPCS and La, Ce and Nd are respectively 1.31 multiplied by 105s-1、1.63×105s-1、1.79×105s-1. The membrane surface shear rate is firstly controlled to be 1.31 multiplied by 105s-1<γ<1.63×105s-1nPCS-La decomplexes, and La is separated by ultrafiltration; then controlling the membrane surface shear rate to be 1.63 multiplied by 105s-1<γ<1.79×105s-1nPCS-Ce decomplexes and is ultrafiltered to separate Ce; finally controlling the membrane surface shear rate gamma>1.79×105s-1And (3) decomplexing nPCS-Nd, performing ultrafiltration to separate Nd, and simultaneously obtaining regenerated nPCS which can continue to perform complexation of rare earth ions.
The method for separating rare earth by using the water-soluble polymer complexing agent is characterized by comprising the following steps of: using acid phosphorylated chitosan aPCS as a complexing agent, and realizing the ordered separation of rare earth ions by adjusting membrane surface shear rate coupling ultrafiltration according to the difference of different aPCS-Re complex critical shear rates under certain pH and temperature conditions;
under the conditions of normal temperature and pH value of 3, when aPCS is used as a complexing agent, the critical shear rates of complexes aPCS-La, aPCS-Ce and aPCS-Nd formed by the aPCS and La, Ce and Nd are respectively 4.74 multiplied by 104、5.20×104、6.45×104s-1. The membrane surface shear rate is firstly controlled to be 4.74 multiplied by 104s-1<γ<5.20×104s-1Decomplexation of aPCS-La, and ultrafiltration separation of La; then controlling the membrane surface shear rate to be 5.20 multiplied by 104s-1<γ<6.45×104s-1aPCS-Ce is decomplexed and subjected to ultrafiltration separation to obtain Ce; finally controlling the membrane surface shear rate gamma>6.45×104s-1The aPCS-Nd is decomplexed, and Nd is separated by ultrafiltration, and simultaneously regenerated aPCS is obtained, and the regenerated aPCS can be used for continuously carrying out rare earthComplexing ions;
under the conditions of normal temperature and pH value of 4, when aPCS is used as a complexing agent, the critical shear rates of complexes aPCS-La, aPCS-Ce and aPCS-Nd formed by the aPCS and La, Ce and Nd are respectively 6.71 multiplied by 104、7.39×104、8.98×104s-1. The membrane surface shear rate is firstly controlled to be 6.71 multiplied by 104s-1<γ<7.39×104s-1Decomplexation of aPCS-La, and ultrafiltration separation of La; then controlling the membrane surface shear rate to be 7.39 multiplied by 104s-1<γ<8.98×104s-1aPCS-Ce is decomplexed and subjected to ultrafiltration separation to obtain Ce; finally controlling the membrane surface shear rate gamma>8.98×104s-1Decomplexing aPCS-Nd, performing ultrafiltration to separate Nd, and simultaneously obtaining regenerated aPCS which can continue to perform complexation of rare earth ions;
under the conditions of normal temperature and pH value of 5, when aPCS is used as a complexing agent, the critical shear rates of complexes aPCS-La, aPCS-Ce and aPCS-Nd formed by the aPCS and La, Ce and Nd are respectively 9.29 multiplied by 104、1.04×105、1.13×105s-1. The membrane surface shear rate is firstly controlled to be 9.29 multiplied by 104s-1<γ<1.04×105s-1Decomplexation of aPCS-La, and ultrafiltration separation of La; then controlling the membrane surface shear rate to be 1.04 multiplied by 105s-1<γ<1.13×105s-1aPCS-Ce is decomplexed and subjected to ultrafiltration separation to obtain Ce; finally controlling the membrane surface shear rate gamma>1.13×105s-1And (3) decomplexing aPCS-Nd, performing ultrafiltration to separate Nd, and simultaneously obtaining regenerated aPCS which can continue to perform complexation of rare earth ions.
The invention has the following advantages:
(1) compared with the common water-soluble polymer complexing agent, the phosphorylated chitosan has superior rare earth complexing ability and rare earth selectivity, and is applied to the rare earth separation process as the complexing agent, so that the rare earth ion retention rate can reach more than 99 percent, and the separation efficiency is improved;
(2) the method has the advantages of good selective separation effect, small acid and alkali consumption, no secondary pollution, no need of organic solvent, cost saving and ammonia nitrogen pollution reduction;
(3) the shearing decomplexing coupling ultrafiltration process can realize the selective separation of the mixed rare earth and the regeneration of the complex agent phosphorylated chitosan at one time, and is economic and environment-friendly.
Detailed Description
The invention is further described below with reference to examples.
Example 1
Preparing a mixed ion solution with La and Ce mass concentrations of 10mg/L at normal temperature, and adding nPCS into the solution, wherein the mass ratio of the nPCS to the mixed rare earth ions is 10: and 1, adjusting the pH value of the solution to be 5, and stirring for 0.5h to obtain a solution containing the nPCS-La and nPCS-Ce complexes, wherein the pH value of the solution is 5, and the P/Re of the solution is 10. According to the difference of the shear stability of the two complexes under the condition, the membrane surface shear rate is firstly controlled to be 8.86 multiplied by 104s-1<γ<9.91×104s-1Destabilizing nPCS-La for decomplexing nPCS-Ce, and ultrafiltering to separate La; then adjusting the membrane surface shear rate to be more than 9.91 multiplied by 104s-1The complex of nPCS-Ce is decomplexed, Ce is separated out by ultrafiltration, and regenerated nPCS is obtained at the same time, and can continue to carry out complexation of rare earth ions.
Example 2
Preparing mixed ion solution with the mass concentration of both Ce and Nd being 20mg/L at normal temperature, and adding nPCS into the solution, wherein the mass ratio of the nPCS to the mixed rare earth ions is 10: and 1, adjusting the pH value of the solution to 6, and stirring for 1h to obtain a mixed complex solution of nPCS-Ce and nPCS-Nd, wherein the pH value of the mixed complex solution is 6, and the P/Re of the mixed complex solution is 10. According to the difference of the shear stability of the two complexes under the condition, the membrane surface shear rate is firstly controlled to be 1.21 multiplied by 105s-1<γ<1.33×105s-1nPCS-Ce is destabilized and decomplexed, nPCS-Nd is not decomplexed, and Ce is separated out by ultrafiltration; then adjusting the membrane surface shear rate to 1.33X 105s-1And (3) decomplexing the nPCS-Nd complex, performing ultrafiltration to separate Nd, and simultaneously obtaining regenerated nPCS which can continue to perform complexation of rare earth ions.
Example 3
Preparing a solution with La, Ce and Nd mass concentrations of 15mg/L at normal temperature, and adding nPCS into the solution, wherein the mass ratio of the nPCS to the mixed rare earth ions is 10: and 1, adjusting the pH value of the solution to 7, and stirring for 2.5h to obtain a mixed complex solution of nPCS-La, nPCS-Ce and nPCS-Nd, wherein the pH value of the mixed complex solution is 7, and the P/Re of the mixed complex solution is 10. According to the difference of the shear stability of the three complexes under the condition, the membrane surface shear rate is firstly controlled to be 1.31 multiplied by 105s-1<γ<1.63×105s-1nPCS-La is unstable and complex-released, nPCS-Ce and nPCS-Nd are not complex-released, and La is separated by ultrafiltration; then adjusting the membrane surface shear rate to be 1.63 multiplied by 105s-1<γ<1.79×105s-1nPCS-Ce is destabilized and decomplexed, nPCS-Nd is not decomplexed, and Ce is separated out by ultrafiltration; finally, adjusting the membrane surface shear rate to 1.79X 105s-1And (3) decomplexing the nPCS-Nd complex, performing ultrafiltration to separate Nd, and simultaneously obtaining regenerated nPCS which can continue to perform complexation of rare earth ions.
Example 4
Preparing mixed ion solution with La and Ce mass concentration of 10mg/L at normal temperature, and adding aPCS into the solution, wherein the mass ratio of the aPCS to the mixed rare earth ions is 8: 1, adjusting the pH value of the solution to 3, and stirring for 1.5h to obtain a mixed complex solution of aPCS-La and aPCS-Ce, wherein the pH value of the mixed complex solution is 3, and the P/Re of the mixed complex solution is 8. According to the difference of the shear stability of the two complexes under the condition, the membrane surface shear rate is firstly controlled to be 4.74 multiplied by 104s-1<γ<5.20×104s-1Destabilizing aPCS-La for decomplexation, and ultrafiltering aPCS-Ce without decomplexation to separate La; then adjusting the membrane surface shear rate to 5.20X 104s-1In the above step, the aPCS-Ce complex is decomplexed, the Ce is separated by ultrafiltration, and meanwhile, the regenerated aPCS is obtained, and the regenerated aPCS can continue to carry out complexation of rare earth ions.
Example 5
Preparing mixed ion solution with the mass concentration of both Ce and Nd being 15mg/L at normal temperature, and adding aPCS into the solution, wherein the mass ratio of the aPCS to the mixed rare earth ions is 8: and 1, adjusting the pH value of the solution to be 4, and stirring for 2h to obtain a mixed complex solution of aPCS-Ce and aPCS-Nd, wherein the pH value of the mixed complex solution is 4, and the P/Re of the mixed complex solution is 8. According to the conditions, the shear stability of the two complexesThe difference of (2) is that the membrane surface shear rate is controlled to be 7.39X 104s-1<γ<8.98×104s-1Destabilizing aPCS-Ce for decomplexing, not decomplexing aPCS-Nd, and ultrafiltering to separate Ce; then adjusting the membrane surface shear rate to 8.98 x 104s-1In the above step, complexing of the aPCS-Nd complex is performed, Nd is separated by ultrafiltration, and meanwhile, regenerated aPCS is obtained, and the regenerated aPCS can be used for continuously complexing rare earth ions.
Example 6
Preparing a mixed ion solution with La, Ce and Nd mass concentrations of 20mg/L at normal temperature, and adding aPCS into the solution, wherein the mass ratio of the aPCS to the mixed rare earth ions is 8: and 1, adjusting the pH value of the solution to be 5, and stirring for 2.5h to obtain a mixed complex solution of aPCS-La, aPCS-Ce and aPCS-Nd, wherein the pH value of the mixed complex solution is 5, and the P/Re of the mixed complex solution is 8. According to the difference of the shear stability of the three complexes under the condition, the membrane surface shear rate is firstly controlled to be 9.29 multiplied by 104s-1<γ<1.04×105s-1Destabilizing aPCS-La for decomplexing, wherein aPCS-Ce and aPCS-Nd are not decomplexed, and ultrafiltering to separate La; then adjusting the membrane surface shear rate to be 1.04X 105s-1<γ<1.13×105s-1Destabilizing aPCS-Ce for decomplexing, not decomplexing aPCS-Nd, and ultrafiltering to separate Ce; finally, adjusting the membrane surface shear rate to 1.13X 105s-1In the above step, complexing of the aPCS-Nd complex is performed, Nd is separated by ultrafiltration, and meanwhile, regenerated aPCS is obtained, and the regenerated aPCS can be used for continuously complexing rare earth ions.

Claims (3)

1. A method for separating rare earth by using a water-soluble polymer complexing agent is characterized by comprising the following steps: the adopted water-soluble polymer complexing agents are neutral phosphorylated chitosan nPCS and acidic phosphorylated chitosan aPCS;
wherein the chemical structural formula of nPCS is as follows:
Figure FDA0003235417210000011
aPCS has a chemical structural formula as follows:
Figure FDA0003235417210000012
in the structure, n is 1200-3000;
the method comprises the following steps:
firstly, under the condition that the pH value is 3-7, adding a certain amount of neutral phosphorylated chitosan nPCS or acidic phosphorylated chitosan aPCS into a solution containing rare earth ions, and stirring for 0.5-2.5 h to ensure that the rare earth ions and the nPCS or the aPCS are fully complexed to form a PCS-Re complex; then, according to the difference of the shearing stability of different PCS-Re complexes under certain conditions, the separation of mixed rare earth ions and the regeneration of the complex agent phosphorylated chitosan are realized by adopting shearing decomplexation coupling ultrafiltration;
the dosage of the neutral phosphorylated chitosan nPCS or the acidic phosphorylated chitosan aPCS is determined by measuring the relationship between the mass ratio P/Re of the complexing agent to the rare earth ions and the rare earth ion retention rate R by adopting a complexing-ultrafiltration method: when complexation-ultrafiltration is carried out under a certain pH condition, the rare earth ion retention rate increases with the increase of P/Re, and when the maximum value of R is reached and does not increase with the increase of P/Re, the value is the critical P/Re value, and the addition amount of the complexing agent is determined according to the critical P/Re value;
the PCS-Re complex has the shear stability under certain pH condition, and the critical shear rate gamma of the PCS-Re complex is adoptedcThe maximum shear rate that the PCS-Re complex can bear when the PCS-Re complex is kept stable is determined according to the relationship between the membrane surface shear rate and the rare earth ion rejection rate: when the membrane surface shear rate is less than the critical shear rate of the PCS-Re complex, the PCS-Re complex is kept stable, and the retention rate of rare earth ions is kept unchanged; when the membrane surface shear rate is greater than the critical shear rate of the PCS-Re complex, the PCS-Re complex is decomplexed into the polymer complexing agent and the free rare earth ions, the free rare earth ions can permeate the ultrafiltration membrane, and the rejection rate of the rare earth ions is sharply reduced.
2. The method according to claim 1, wherein the rare earth is separated by a water-soluble polymeric complexing agent, wherein: using neutral phosphorylated chitosan nPCS as a complexing agent, and realizing the ordered separation of rare earth ions by adjusting membrane surface shear rate coupling ultrafiltration according to the difference of critical shear rates of different nPCS-Re complexes under certain pH and temperature conditions;
under the conditions of normal temperature and pH 5, when nPCS is used as a complexing agent, the critical shear rates of complexes nPCS-La, nPCS-Ce and nPCS-Nd formed by nPCS and La, Ce and Nd are respectively 8.86 multiplied by 104s-1、9.91×104s-1、1.09×105s-1(ii) a Firstly controlling the membrane surface shear rate to be 8.86 multiplied by 104s-1<γ<9.91×104s-1nPCS-La decomplexes, and La is separated by ultrafiltration; then controlling the membrane surface shear rate to be 9.91 multiplied by 104s-1<γ<1.09×105s-1nPCS-Ce decomplexes and is ultrafiltered to separate Ce; finally controlling the membrane surface shear rate gamma>1.09×105s-1The nPCS-Nd is subjected to decomplexing, Nd is separated by ultrafiltration, and regenerated nPCS is obtained at the same time, and can be used for continuously complexing rare earth ions;
under the conditions of normal temperature and pH 6, when nPCS is used as a complexing agent, the critical shear rates of complexes nPCS-La, nPCS-Ce and nPCS-Nd formed by nPCS and La, Ce and Nd are respectively 1.02 multiplied by 105、1.21×105、1.33×105s-1(ii) a Firstly controlling the membrane surface shear rate to be 1.02 multiplied by 105s-1<γ<1.21×105s-1nPCS-La decomplexes, and La is separated by ultrafiltration; then controlling the membrane surface shear rate to be 1.21 multiplied by 105s-1<γ<1.33×105s-1nPCS-Ce decomplexes and is ultrafiltered to separate Ce; finally controlling the membrane surface shear rate gamma>1.33×105s-1The nPCS-Nd is subjected to decomplexing, Nd is separated by ultrafiltration, and regenerated nPCS is obtained at the same time, and can be used for continuously complexing rare earth ions;
under the conditions of normal temperature and pH value of 7, when nPCS is used as a complexing agent, the critical shear rates of complexes nPCS-La, nPCS-Ce and nPCS-Nd formed by nPCS and La, Ce and Nd are respectively 1.31 multiplied by 105、1.63×105、1.79×105s-1(ii) a The membrane surface shear rate is firstly controlled to be 1.31 multiplied by 105s-1<γ<1.63×105s-1nPCS-La decomplexes, and La is separated by ultrafiltration; then controlling the membrane surface shear rate to be 1.63 multiplied by 105s-1<γ<1.79×105s-1nPCS-Ce decomplexes and is ultrafiltered to separate Ce; finally controlling the membrane surface shear rate gamma>1.79×105s-1And (3) decomplexing nPCS-Nd, performing ultrafiltration to separate Nd, and simultaneously obtaining regenerated nPCS which can continue to perform complexation of rare earth ions.
3. The method according to claim 1, wherein the rare earth is separated by a water-soluble polymeric complexing agent, wherein: using acid phosphorylated chitosan aPCS as a complexing agent, and realizing the ordered separation of rare earth ions by adjusting membrane surface shear rate coupling ultrafiltration according to the difference of different aPCS-Re complex critical shear rates under certain pH and temperature conditions;
under the conditions of normal temperature and pH value of 3, when aPCS is used as a complexing agent, the critical shear rates of complexes aPCS-La, aPCS-Ce and aPCS-Nd formed by the aPCS and La, Ce and Nd are respectively 4.74 multiplied by 104s-1、5.20×104s-1、6.45×104s-1. The membrane surface shear rate is firstly controlled to be 4.74 multiplied by 104s-1<γ<5.20×104s-1Decomplexation of aPCS-La, and ultrafiltration separation of La; then controlling the membrane surface shear rate to be 5.20 multiplied by 104s-1<γ<6.45×104s-1aPCS-Ce is decomplexed and subjected to ultrafiltration separation to obtain Ce; finally controlling the membrane surface shear rate gamma>6.45×104s-1Decomplexing aPCS-Nd, performing ultrafiltration to separate Nd, and simultaneously obtaining regenerated aPCS which can continue to perform complexation of rare earth ions;
under the conditions of normal temperature and pH value of 4, when aPCS is used as a complexing agent, the critical shear rates of complexes aPCS-La, aPCS-Ce and aPCS-Nd formed by the aPCS and La, Ce and Nd are respectively 6.71 multiplied by 104s-1、7.39×104s-1、8.98×104s-1(ii) a The membrane surface shear rate is firstly controlled to be 6.71 multiplied by 104s-1<γ<7.39×104s-1Decomplexation of aPCS-La, and ultrafiltration separation of La; then controlling the membrane surface shear rate to be 7.39 multiplied by 104s-1<γ<8.98×104s-1aPCS-Ce is decomplexed and subjected to ultrafiltration separation to obtain Ce; final controlFilm surface shear rate gamma>8.98×104s-1Decomplexing aPCS-Nd, performing ultrafiltration to separate Nd, and simultaneously obtaining regenerated aPCS which can continue to perform complexation of rare earth ions;
under the conditions of normal temperature and pH value of 5, when aPCS is used as a complexing agent, the critical shear rates of complexes aPCS-La, aPCS-Ce and aPCS-Nd formed by the aPCS and La, Ce and Nd are respectively 9.29 multiplied by 104、1.04×105、1.13×105s-1(ii) a The membrane surface shear rate is firstly controlled to be 9.29 multiplied by 104s-1<γ<1.04×105s-1Decomplexation of aPCS-La, and ultrafiltration separation of La; then controlling the membrane surface shear rate to be 1.04 multiplied by 105s-1<γ<1.13×105s-1aPCS-Ce is decomplexed and subjected to ultrafiltration separation to obtain Ce; finally controlling the membrane surface shear rate gamma>1.13×105s-1And (3) decomplexing aPCS-Nd, performing ultrafiltration to separate Nd, and simultaneously obtaining regenerated aPCS which can continue to perform complexation of rare earth ions.
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