Search

CN-122016690-A - Organic acid and RE determined by molar ratio method3+Coordination number method

CN122016690ACN 122016690 ACN122016690 ACN 122016690ACN-122016690-A

Abstract

The invention relates to the technical field of analytical chemistry and hydrometallurgy, in particular to a method for determining coordination numbers of organic acid and RE 3+ by using a molar ratio method. The method comprises the steps of S1, preparing a plurality of organic acid solutions with different concentrations of C Y , preparing RE 3+ solutions of C M , mixing the two solutions in equal volume, adjusting the pH value, carrying out complexation reaction, S2, determining the maximum absorption wavelength, determining the absorbance A of the solution after each complexation reaction under the maximum absorption wavelength, S3, plotting by taking the molar ratio n= [ C Y ]/[C M ] as an abscissa and the absorbance A as an ordinate, finding out a section where the absorbance increases linearly along with the increase of n and a section where the absorbance reaches a platform or the slope changes obviously, and carrying out linear fitting on data points of the two sections to obtain two straight lines, wherein the value of the abscissa n corresponding to the intersection point of the two straight lines is the coordination ratio of the complex. The invention has reliable result, low cost, easy popularization and convenient and quick operation.

Inventors

  • HONG XIANG
  • ZHANG ZHENYUE
  • DENG XIANGYI
  • WANG ANFU
  • MA XIANG

Assignees

  • 武汉工程大学

Dates

Publication Date
20260512
Application Date
20260130

Claims (10)

  1. 1. A method for determining coordination numbers of an organic acid and RE 3+ by using a molar ratio method, comprising the following steps: S1, preparing a plurality of organic acid solutions with different concentrations of C Y , preparing RE 3+ rare earth ion solution with the concentration of C M , mixing the organic acid solution with the rare earth ion solution in equal volume, adjusting the pH value, and carrying out complexation reaction; S2, carrying out ultraviolet spectrophotometry after the complexation reaction is completed, determining the maximum absorption wavelength of the complex, and determining the absorbance A of the solution after each complexation reaction under the maximum absorption wavelength; S3, plotting with the molar ratio n= [ C Y ]/[C M ] as an abscissa and the measured absorbance A as an ordinate, finding out a section in which the absorbance rises linearly along with the increase of n and a section in which the absorbance reaches a platform or the slope changes obviously, respectively performing linear fitting on data points of the two sections to obtain two straight lines, and obtaining an abscissa n value corresponding to the intersection point of the two straight lines, namely the coordination ratio of the complex.
  2. 2. A method for determining coordination numbers of an organic acid and RE 3+ by a molar ratio method according to claim 1, wherein C M =0.01mol/L, C Y is 0.005mol/L, 0.01mol/L, 0.02mol/L, 0.03mol/L, 0.04mol/L, 0.05mol/L, respectively.
  3. 3. The method for determining coordination number of organic acid and RE 3+ by molar ratio method according to claim 1, wherein in step S2, a full wavelength scan of 400-800nm is performed, if 200-400nm is selected for organic acid having ultraviolet absorption.
  4. 4. A method for determining the coordination number of an organic acid and RE 3+ by molar ratio method according to claim 1, wherein RE 3+ is one or more of La, ce, Y, nd.
  5. 5. A method for determining the coordination number of an organic acid and RE 3+ using a molar ratio method according to claim 1, wherein the organic acid has an organic soluble compound having a carboxyl group, a phenolic hydroxyl group and an organophosphine functional group.
  6. 6. The method for determining coordination numbers of organic acid and RE 3+ by using a molar ratio method according to claim 1, wherein the organic acid is one or more of citric acid, malic acid, acetic acid and phthalic acid.
  7. 7. A method for determining the coordination number of an organic acid and RE 3+ by means of a molar ratio method according to claim 1, wherein n=1-2, n=1, forms a 1:1 coordination compound, if the intersection n=2, forms a 1:2 coordination compound complex, and n is greater than 1 and less than 2, forms a 1:1 coordination compound and a 1:2 coordination compound complex.
  8. 8. A method for determining the coordination number of an organic acid and RE 3+ by means of molar ratio as claimed in claim 1, characterized in that the pH is 4-5.
  9. 9. A method for determining the coordination number of an organic acid and RE 3+ by means of a molar ratio method according to claim 1, wherein the pH is adjusted with 0.01M sodium hydroxide.
  10. 10. A method for determining the coordination number of an organic acid and RE 3+ by means of molar ratio as claimed in claim 1, characterized in that the absorption maximum is 210-297nm.

Description

Method for determining coordination number of organic acid and RE 3+ by using molar ratio method Technical Field The invention relates to the technical field of analytical chemistry and hydrometallurgy, in particular to a method for determining coordination numbers of organic acid and RE 3+ by using a molar ratio method. Background Weathered crust leaching rare earth ore is an important novel mineral resource, and is often known as the heart of the modern industry due to the excellent performance of the weathered crust leaching rare earth ore in the high-end fields of military, aerospace, electronics, new materials and the like. However, the rare earth oxide sites in the ore deposit are usually only 0.05% -0.2%, and the rare earth elements are mainly adsorbed on the surfaces of clay minerals such as kaolinite, halloysite, illite and the like in an ionic form, and can be regarded as natural ion exchangers, and the rare earth elements are extracted by replacing electrolyte cations (such as Na +、K+、NH4+、H+ and the like). The rare earth element electron orbit is special in filling condition, the ground state 5d orbit is empty, and electrons can transit from the 4f or 6s orbit to the 5d orbit under the condition of some ligands (such as CO and CN) or high-energy excitation, so that an excited state d electron configuration is formed, and covalent bonding is participated. And the d orbit energy is high, the space expansion is large, and the coordination capacity is strong. Organic oxygen-containing groups contained in the organic acid, such as C-O, P-O, S-O, and the like, can coordinate with RE 3+ to produce a complex. In the green leaching process of ion adsorption type rare earth ore, organic acid is often used as an additive to be compositely used with leaching agents such as magnesium salt and the like so as to strengthen leaching or improve selectivity. The core of the action mechanism is that organic acid anions and RE 3+ form coordination compounds with different coordination ratios, which directly influence leaching efficiency and impurity inhibition effect. At present, the main method for determining the coordination ratio is a potentiometric titration method, but the method has complicated operation and limited applicability to a specific system, and relates to solvent selection, electrode treatment, humidity control and the like, and has complicated operation and poor reproducibility. Disclosure of Invention The invention aims at providing a method for measuring coordination numbers of organic acid and RE < 3+ > by using a molar ratio method, which is simple and convenient to operate, accurate in result and wide in applicability. The invention relates to a method for determining coordination numbers of organic acid and RE 3+ by using a molar ratio method, which comprises the following steps: S1, preparing a plurality of organic acid solutions with different concentrations of C Y, preparing RE 3+ rare earth ion solution with the concentration of C M, mixing the organic acid solution with the rare earth ion solution in equal volume, adjusting the pH value, and carrying out complexation reaction; S2, carrying out ultraviolet spectrophotometry after the complexation reaction is completed, determining the maximum absorption wavelength of the complex, and determining the absorbance A of the solution after each complexation reaction under the maximum absorption wavelength; S3, plotting with the molar ratio n= [ C Y]/[CM ] as an abscissa and the measured absorbance A as an ordinate, finding out a section in which the absorbance rises linearly along with the increase of n and a section in which the absorbance reaches a platform or the slope changes obviously, respectively performing linear fitting on data points of the two sections to obtain two straight lines, and obtaining an abscissa n value corresponding to the intersection point of the two straight lines, namely the coordination ratio of the complex. Further, C M=0.01mol/L, CY was 0.005mol/L, 0.01mol/L, 0.02mol/L, 0.03mol/L, 0.04mol/L, 0.05mol/L, respectively. Further, in step S2, a full wavelength scan of 400-800nm is performed, if 200-400nm is selected for organic acids having UV absorption. Further, RE 3+ is one or more of La, ce, Y and Nd. Further, the organic acid has an organic soluble compound of carboxyl, phenolic hydroxyl and organophosphine functionality. Further, the organic acid is one or more of citric acid, malic acid, acetic acid and phthalic acid. Further, n=1-2, n=1, a 1:1 coordination compound is formed, if the intersection point n=2, a 1:2 coordination compound complex is formed, and if n is greater than 1 and less than 2, a 1:1 coordination compound and a 1:2 coordination compound complex are formed. Further, the pH value is 4-5. Further, the pH was adjusted with 0.01M sodium hydroxide. Further, the maximum absorption wavelength is 210-297nm. The invention adopts a molar ratio method to measure the coordination strength formed by the or