Method for extracting platinum (II) cyanide by microemulsion containing 1-butyl-3-ethyl octanoate imidazolium bromide

Abstract

The present invention discloses a method for extracting platinum (II) cyanide by microemulsion containing 1-ethyl-3-octylimidazolium bromide, belonging to the hydrometallurgy of platinum group metals. The method includes adjusting the pH value of the 2‑ feed liquid in the range of 9.0 - 11.5, preparing a microemulsion organic phase composed of 1-ethyl-3-octylimidazolium bromide, co-surfactant, and diluent, the concentration of 1-ethyl-3-octylimidazolium bromide in the microemulsion organic phase is 0.01 - 0.05 mol / L, transferring [[Pt(CN)₄]] 2‑ from the aqueous phase to the microemulsion organic phase, stripping platinum with 0.05 - 0.3 mol·L ‑1 NaBr solution. The extraction cycle is short, phase separation is rapid, the extraction capacity is large, and the application prospect is wide.

Description

Technical Field

[0001] The present invention belongs to the hydrometallurgy of precious metals, relates to a process for extracting platinum from alkaline cyanide solutions, and particularly relates to a method for extracting platinum(II) cyanide with a microemulsion containing 1-butyl-3-ethyl octanoate imidazolium bromide. Background Art

[0002] Solvent extraction technology is the mainstream process for extracting individual platinum group metals from the leaching solutions of platinum group metal metallurgy. In the reported solvent extraction systems, ionic liquids have been widely used to replace traditional extractants due to their low toxicity, low melting point, insolubility, adjustable structure, and low vapor pressure, etc., for the separation and recovery of platinum in platinum group metals. However, ionic liquids have high viscosity, slow extraction kinetics, and difficult stripping. In recent years, a microemulsion extraction phase composed of an extractant, a co-surfactant, and a diluent has been used for the solvent extraction and separation of platinum group metals due to its advantages of low viscosity, high selectivity, and fast mass transfer rate. The microemulsion extraction system combines the advantages of ionic liquids and microemulsions. It not only has a large extraction capacity and fast phase separation, but also is easy to strip. Most of the reported microemulsion extraction systems are limited to acidic chloride media. With the wide application of pressure cyanidation technology in platinum group metal metallurgy, a large amount of platinum group metals in alkaline cyanide solution media need to be refined. The traditional solvent extraction method has slow phase separation, difficult stripping, and high cost, and can no longer meet the requirements for the separation and extraction of platinum group metals in alkaline cyanide solution media. Studying the extraction behavior of platinum group metals by a new microemulsion extraction system in alkaline cyanide solution media and establishing a new ionic liquid microemulsion extraction system with efficient recycling has great significance for improving the metallurgical refining process of platinum group metals in alkaline cyanide solution media. The method for extracting platinum(II) cyanide with a microemulsion containing 1-butyl-3-ethyl octanoate imidazolium bromide used in the present invention has not been reported in the literature. The ionic liquid microemulsion system established in the present invention not only has high extraction efficiency for platinum in alkaline cyanide solution media, but also is easy to strip, with obvious practical value and broad application prospects in the field of platinum group metal metallurgical separation. Summary of the Invention

[0003] The object of the present invention is to provide an ionic liquid microemulsion system with high extraction efficiency, fast phase separation speed, and easy stripping for the problems of slow phase separation and difficult stripping in the extraction and separation process of platinum ions in alkaline cyanide solution media, which can extract and separate platinum in alkaline cyanide solution media, has a short extraction cycle, high extraction capacity, low cost, and has the prospect of popularization and application.

[0004] The object of the present invention is achieved in the following way:

[0005] A method for extracting platinum(II) cyanide with a microemulsion containing 1-butyl-3-ethyl octanoate imidazolium bromide, comprising the following steps:

[0006] (1) Adjust the pH value of the feed solution with a [Pt(CN)₄] concentration of 50 mg / L to 300 mg / L of Pt(II) within the range of 9.0 to 11.5 to serve as the aqueous phase of the extraction system; 2- The pH value of the feed solution is adjusted within the range of 9.0 to 11.5 and used as the aqueous phase of the extraction system;

[0007] (2) Prepare a microemulsion organic phase composed of an extractant, a co-surfactant, and a diluent. Among them,

[0008] 1-ethyl-3-methylimidazolium octanoate bromide is used as the extractant, and the concentration of this extractant in the microemulsion organic phase is 0.01 mol / L to 0.05 mol / L;

[0009] Select any one of n-pentanol, n-butanol, n-octanol, tributyl phosphate (TBP), or polyethylene glycol octyl phenyl ether (Triton X-100) as the co-surfactant, and the volume of the co-surfactant accounts for 20% to 30% of the volume of the organic phase;

[0010] Select any one of cyclohexane or n-heptane as the diluent, and the volume of the diluent is the remainder of the extractant and the co-surfactant;

[0011] Ultrasonically treat the mixture of the extractant, co-surfactant, and diluent for 3 to 5 minutes, and then gradually add 0.02 M NaCl solution dropwise until a precipitate just appears in the aqueous phase. Let it stand for 1 hour, separate the organic phase from the aqueous phase, and the transparent organic phase is the prepared microemulsion;

[0012] (3) Add the microemulsion organic phase and the aqueous phase to a separating funnel according to the ratio of the microemulsion organic phase to the aqueous phase (O / A) of 1:1, let it stand for layering, and transfer [Pt(CN)₄] 2- from the aqueous phase to the microemulsion organic phase;

[0013] (4) Take the microemulsion organic phase loaded with [Pt(CN)₄] 2- after extraction in the above step (3), put it into another separating funnel, and add a NaBr solution with a concentration of 0.05 to 0.3 mol / L according to the ratio of the aqueous phase to the microemulsion organic phase (A / O) of 1:1 to back-extract [Pt(CN)₄] 2- in the microemulsion organic phase.

[0014] Furthermore, in the step (3), the microemulsion organic phase and the aqueous phase placed in the separating funnel are shaken and mixed for 2 to 5 minutes and then allowed to stand for layering.

[0015] Furthermore, in the step (4), the mixing time for the NaBr solution to back-extract [Pt(CN)₄] 2- in the organic phase is 3 to 5 minutes, and then let it stand for layering.

[0016] Furthermore, in steps (3) and (4) after phase separation, the concentration of Pt(II) in the aqueous phase is measured respectively, and the extraction rate of Pt(II) by the microemulsion with 1-butyl-3-ethyl octanoate imidazole bromide as the extractant and the stripping rate of Pt(II) by NaBr stripping are calculated respectively by the subtraction method.

[0017] Furthermore, the molecular formula of 1-butyl-3-ethyl octanoate imidazole bromide (abbreviated as BOEIB) is C 17 H 31 BrN2O 2， with a relative molecular mass of 375.14 and the structural formula as follows:

[0018] ,

[0019] Its chemical characteristic parameters are:

[0020] 1 H NMR (400 MHz, CDCl3- d 6) δ 10.098 - 10.074 (1H, s), 7.385 - 7.350 (2H, d, J = 1.6Hz), 4.008 - 3.967 (4H, m), 3.717 - 3.651 (2H, m), 1.878 - 1.823 (2H, m), 1.526 - 1.484(4H, m), 1.154 - 1.137 (2H, m), 0.880 - 0.843 (11H, m), 0.835 - 0.764(3H, m).

[0021] 13 C NMR (100 MHz, CDCl3- d 6) δ 173.64, 137.21, 122.31, 77.39, 60.13, 50.00, 49.81, 34.12, 32.15, 30.20, 28.72, 28.54, 25.94, 24.65, 19.42, 14.19, 13.42.

[0022] The present invention has the following advantages and effects:

[0023] The practical pH range is wide and has high applicability. The industrial-grade platinum group metal metallurgical leaching solution obtained by the pressure cyanidation technology usually has a pH value between 9 and 11, while the optimal pH value range of the ionic liquid microemulsion organic phase constructed by the present invention is very close to it (Table 1). In addition, the extraction ability of the microemulsion extraction system can be adjusted by the addition amount of the BOEIB extractant, and this process has extremely high prospects for popularization and application.

[0024] 1. Effect of pH on the extraction of Pt(CN)4 by BOEIB / n - heptane / n - pentanol / NaCl microemulsion 2- Performance

[0025] At 25 °C, the concentration of Pt(CN)4 in the solution to be extracted was fixed at 88.2 mg / L. A BOEIB / n - heptane / n - pentanol / NaCl microemulsion organic phase was selected, with the concentration of BOEIB being 0.01 mol / L. According to the ratio of the microemulsion organic phase to the aqueous phase (O / A) of 1:1, the aqueous phase and the microemulsion organic phase were placed in a separating funnel and mechanically shaken for 2 minutes, then allowed to stand for phase separation. The volume of n - pentanol accounted for 30% of the volume of the microemulsion organic phase, and the total volume of the microemulsion organic phase was 50 ml. The effect of different pH values on the extraction of Pt(CN)4 by BOEIB / n - heptane / n - pentanol / NaCl microemulsion 2- Performance is shown in Table 1 as follows: 2- Performance

[0026] Table 1. Effect of pH on the extraction of Pt(CN)4 by BOEIB / n - heptane / n - pentanol / NaCl microemulsion 2- Performance

[0027] pH value 8.5 9.0 9.5 10.0 10.5 11.0 11.5 12.0 12.5 Extraction rate E(%) 95.2 98.1 98.6 99.2 99.1 98.5 98.2 92.9 87.5

[0028] The experimental results show that the BOEIB / n - heptane / n - pentanol / NaCl microemulsion has the best extraction efficiency for Pt(CN)4 in an alkaline medium with a pH of 9.0 - 11.5 2-

[0029] 2. Effect of BOEIB concentration on the extraction of Pt(CN)4 by BOEIB / n - heptane / n - pentanol / NaCl microemulsion 2- Performance

[0030] At 25 °C, the pH value of the solution was adjusted to 10.5. According to the ratio of the microemulsion organic phase to the aqueous phase (O / A) of 1:1, the aqueous phase and the microemulsion organic phase were placed in a separating funnel and mechanically shaken for 2 minutes, then allowed to stand for phase separation. The initial concentration of Pt(II) in the solution to be extracted was fixed at 106.2 mg / L. A BOEIB / n - heptane / n - pentanol / NaCl microemulsion organic phase was selected, with the volume of n - pentanol accounting for 30% of the volume of the microemulsion organic phase and the total volume of the microemulsion organic phase being 50 ml. The continuous extraction method was used to determine the effect of different concentrations of BOEIB on the extraction of [Pt(CN)4] in the BOEIB / n - heptane / n - pentanol / NaCl microemulsion (Table 2). 2- Performance (Table 2).

[0031] Table 2. Effect of BOEIB concentration on the extraction of [Pt(CN)4] by BOEIB / n - heptane / n - pentanol / NaCl microemulsion 2- Performance

[0032] <![CDATA[C BOEIB (mol / L)]]> 0.01 0.02 0.03 0.04 0.05 Extraction capacity (g / L) 0.41 0.79 1.17 1.56 1.85 ​

[0033] The experimental results show that the concentration of BOEIB in the microemulsion mixed organic phase determines the ability of the microemulsion to extract Pt(II). DETAILED DESCRIPTION

[0034] In order to better understand the present invention, the present invention is further described below through specific implementation methods, but the enumerated embodiments do not limit the scope of protection of the present invention.

[0035] Example 1

[0036] Take Pt(CN)4 with a Pt(II) concentration of 30.0 mg / L 2- 50 mL of the solution was placed in a separatory funnel, and the pH value of the solution was adjusted to 9.0 as the aqueous phase of the extraction system. Preparation of ionic liquid microemulsion organic phase: A certain amount of BOEIB was added to the mixed phase of n-heptane and n-butanol (n-butanol accounted for 20% of the total volume of the mixed phase), the concentration of BOEIB in the mixed phase was 0.01 mol / L, ultrasonic treatment was performed for 3 minutes, 0.02 mol / L NaCl solution was added dropwise to the mixed phase until the aqueous phase just precipitated, and the aqueous phase was removed by centrifugation to obtain BOEIB / n-heptane / n-butanol / NaCl microemulsion organic phase. The organic phase was added to the aqueous phase (O / A=1:1), and the mixture was allowed to stand for 2 minutes after mechanical oscillation to separate the layers. After separation, the concentration of platinum in the aqueous phase was determined, and the concentration of platinum in the organic phase of the microemulsion was calculated by subtraction. The organic phase loaded with platinum was taken and placed in another separatory funnel. According to the ratio of the aqueous phase to the organic phase (A / O=1:1), 0.05M NaBr was added for stripping. After 3 minutes of mixing, the mixture was allowed to stand for stratification. After separation, the concentration of platinum in the stripping phase was determined, and the stripping rate of platinum by NaBr stripping was calculated. The specific data are shown in Table 3.

[0037] Example 2

[0038] Take Pt(CN)4 with a Pt(II) concentration of 105.0 mg / L 2-50 mL of the solution was placed in a separatory funnel, and the pH value of the solution was adjusted to 9.5 to serve as the aqueous phase of the extraction system. An ionic liquid microemulsion organic phase was prepared: A certain amount of BOEIB was added to the mixed phase of cyclohexane and TBP (TBP accounted for 26% of the total volume of the mixed phase), and the concentration of BOEIB in the mixed phase was 0.02 mol / L. After ultrasonic treatment for 4 min, 0.02 mol / L NaCl solution was added dropwise to the mixed organic phase until the aqueous phase just precipitated. The aqueous phase was removed by centrifugation to obtain the BOEIB / cyclohexane / TBP / NaCl microemulsion organic phase. The organic phase was added to the aqueous phase (O / A = 1:1), mechanically shaken for 3 minutes and then allowed to stand for phase separation. After phase separation, the concentration of platinum in the aqueous phase was measured, and the concentration of platinum in the microemulsion organic phase was obtained by subtraction. The organic phase loaded with platinum was taken and placed in another separatory funnel. According to the ratio of the aqueous phase to the organic phase (A / O = 1:1), 0.1 M NaBr was added for back-extraction. After mixing for 3 minutes and then allowing to stand for phase separation, the concentration of platinum in the back-extraction phase was measured, and the back-extraction rate of NaBr for back-extracting platinum was calculated. The specific data are shown in Table 3.

[0039] Example 3

[0040] Take Pt(CN)4 with a Pt(II) concentration of 165.0 mg / L 2- 50 mL of the solution was placed in a separatory funnel, and the pH value of the solution was adjusted to 10.0 to serve as the aqueous phase of the extraction system. An ionic liquid microemulsion organic phase was prepared: A certain amount of BOEIB was added to the mixed phase of n-heptane and n-octanol (n-octanol accounted for 28% of the total volume of the mixed phase), and the concentration of BOEIB in the mixed phase was 0.03 mol / L. After ultrasonic treatment for 4 min, 0.02 mol / L NaCl solution was added dropwise to the mixed organic phase until the aqueous phase just precipitated. The aqueous phase was removed by centrifugation to obtain the BOEIB / n-heptane / n-octanol / NaCl microemulsion organic phase. The organic phase was added to the aqueous phase (O / A = 1:1), mechanically shaken for 5 minutes and then allowed to stand for phase separation. After phase separation, the concentration of platinum in the aqueous phase was measured, and the concentration of platinum in the microemulsion organic phase was obtained by subtraction. The organic phase loaded with platinum was taken and placed in another separatory funnel. According to the ratio of the aqueous phase to the organic phase (A / O = 1:1), 0.1 M NaBr was added for back-extraction. After mixing for 4 minutes and then allowing to stand for phase separation, the concentration of platinum in the back-extraction phase was measured, and the back-extraction rate of NaBr for back-extracting platinum was calculated. The specific data are shown in Table 3.

[0041] Example 4

[0042] Take Pt(CN)4 with a Pt(II) concentration of 224.0 mg / L 2-50 mL of the solution was placed in a separatory funnel, and the pH value of the solution was adjusted to 10.5 to serve as the aqueous phase of the extraction system. An ionic liquid microemulsion organic phase was prepared: A certain amount of BOEIB was added to the mixed phase of n-heptane and n-pentanol (n-pentanol accounted for 20% of the total volume of the mixed phase), and the concentration of BOEIB in the mixed phase was 0.04 mol / L. It was ultrasonically treated for 4 min, and 0.02 mol / L NaCl solution was added dropwise to the mixed organic phase until the aqueous phase just precipitated. The aqueous phase was removed by centrifugation to obtain the BOEIB / n-heptane / n-pentanol / NaCl microemulsion organic phase. The organic phase was added to the aqueous phase (O / A = 1:1), mechanically shaken for 5 minutes and then allowed to stand for phase separation. After phase separation, the concentration of platinum in the aqueous phase was measured, and the concentration of platinum in the microemulsion organic phase was calculated by the subtraction method. The organic phase loaded with platinum was taken and placed in another separatory funnel. According to the ratio of the aqueous phase to the organic phase (A / O = 1:1), 0.15 M NaBr was added for back extraction. After mixing for 4 minutes and then allowing to stand for phase separation, the concentration of platinum in the back extraction phase was measured, and the back extraction rate of NaBr for back extracting platinum was calculated. The specific data are shown in Table 3.

[0043] Example 5

[0044] Take Pt(CN)4 with a Pt(II) concentration of 300.0 mg / L 2- 50 mL of the solution was placed in a separatory funnel, and the pH value of the solution was adjusted to 11.5 to serve as the aqueous phase of the extraction system. An ionic liquid microemulsion organic phase was prepared: A certain amount of BOEIB was added to the mixed phase of cyclohexane and Triton X-100 (n-pentanol accounted for 30% of the total volume of the mixed phase), and the concentration of BOEIB in the mixed phase was 0.05 mol / L. It was ultrasonically treated for 5 min, and 0.02 mol / L NaCl solution was added dropwise to the mixed organic phase until the aqueous phase just precipitated. The aqueous phase was removed by centrifugation to obtain the BOEIB / cyclohexane / Triton X-100 / NaCl microemulsion organic phase. The organic phase was added to the aqueous phase (O / A = 1:1), mechanically shaken for 5 minutes and then allowed to stand for phase separation. After phase separation, the concentration of platinum in the aqueous phase was measured, and the concentration of platinum in the microemulsion organic phase was calculated by the subtraction method. The organic phase loaded with platinum was taken and placed in another separatory funnel. According to the ratio of the aqueous phase to the organic phase (A / O = 1:1), 0.3 M NaBr was added for back extraction. After mixing for 5 minutes and then allowing to stand for phase separation, the concentration of platinum in the back extraction phase was measured, and the back extraction rate of NaBr for back extracting platinum was calculated. The specific data are shown in Table 3.

[0045] Table 3. Microemulsion extraction of platinum(II) cyanide with 1-butyl-3-ethyl octanoate imidazole bromide as the extractant

[0046] Example <![CDATA[C Pt(II) (mg / L)]]> Composition of microemulsion organic phase pH value Extraction rate E(%) Stripping rate S(%) 1 30.0 BOEIB / n-heptane / n-butanol / NaCl 9.0 >99.0 97.5 2 105.0 BOEIB / cyclohexane / TBP / NaCl 9.5 >99.0 97.2 3 165.0 BOEIB / n-heptane / n-octanol / NaCl 10.0 >99.0 97.6 4 224.0 BOEIB / n-heptane / n-pentanol / NaCl 10.5 >99.0 98.1 5 300.0 BOEIB / cyclohexane / Triton X-100 / NaCl 11.5 >99.0 97.1

Claims

1. A method for microemulsion extraction of platinum (II) cyanide with 1-butyl-3-ethyl octanoate imidazolium bromide, characterized in that, It includes the following steps: Step (1): Adjust the pH value of the feed solution containing [Pt(CN)4] with a Pt(II) concentration of 50 mg / L to 300 mg / L within the range of 9.0 to 11.5 to serve as the aqueous phase of the extraction system. 2- ​ Step (2), preparing a microemulsion organic phase composed of an extractant, a co-surfactant, and a diluent, wherein: 1-ethyl-3-octylimidazolium bromide is used as the extractant, and the concentration of the extractant in the microemulsion organic phase is 0.01 mol / L to 0.05 mol / L; Any one of n-pentanol, n-butanol, n-octanol, tributyl phosphate, or polyethylene glycol octyl phenyl ether is used as the co-surfactant, and the volume of the co-surfactant accounts for 20% to 30% of the volume of the organic phase; Any one of cyclohexane or n-heptane is used as the diluent, and the volume of the diluent is the remainder of the extractant and the co-surfactant; The mixture of the extractant, the co-surfactant, and the diluent is ultrasonically treated for 3 to 5 minutes, and then added dropwise to a 0.02 M NaCl solution until the aqueous phase just precipitates. After standing for 1 h, the organic phase and the aqueous phase are separated, and the transparent organic phase is the prepared microemulsion; Step (3): Add the organic phase and aqueous phase of the microemulsion into a separatory funnel in a ratio of O / A of 1:1 for miscibility, let it stand for layering, and transfer [[Pt(CN)4]] 2- from the aqueous phase to the organic phase of the microemulsion; Step (4): Take the microemulsion organic phase loaded with [Pt(CN)4] after extraction in the above step (3). 2- Put it into another separating funnel, add a NaBr solution with a concentration of 0.05 - 0.3 mol / L according to the ratio of aqueous phase to microemulsion organic phase A / O of 1:1, and back-extract [Pt(CN)4] in the microemulsion organic phase. 2- .

2. The method according to claim 1, characterized in that, In the said step (3), the mixing time in the separating funnel is 2 to 5 minutes, and then it stands for layering.

3. The method according to claim 1, wherein In the step (4), the mixing time of [Pt(CN)4] in the organic phase of the stripping microemulsion is 3 to 5 minutes, and then it is allowed to stand for phase separation. 2- ​ 4. The method according to any one of claims 1 to 3, characterized in that, In the said steps (3) and (4), after phase separation, the concentration of Pt(II) in the aqueous phase is measured respectively, and the extraction rate of Pt(II) by the microemulsion with 1-ethyl-3-octylimidazolium bromide as the extractant and the stripping rate of Pt(II) by NaBr are calculated respectively by the subtraction method.