DBC extraction post multi-stage synergistic washing purification method for crude gold purification

Abstract

The application relates to the field of precious metal hydrometallurgy, and particularly discloses a DBC extraction post multistage cooperative washing and purifying method for crude gold purification. Gold-loaded organic phase obtained by extracting gold-containing chloride acid solution through dibutyl carbitol is sequentially subjected to three-step functionalized cooperative washing of high-acid impurity removal, medium-acid conditioning and low-acid / water fine washing. In the high-acid impurity removal step, 1.5-4.0 mol / L hydrochloric acid is used for back-extraction to remove co-extraction metal impurities such as iron, antimony and bismuth; in the medium-acid conditioning step, 0.2-1.0 mol / L hydrochloric acid or nitric acid is used for further purification and adjustment of acidity; and in the low-acid / water fine washing step, deionized water or extremely dilute acid solution with a concentration lower than 0.05 mol / L is used to deeply remove chlorine ions and water-soluble impurities entrained in the organic phase, so that the chlorine ion concentration of the water phase entrained in the organic phase after washing is lower than 0.1 mol / L. The method can realize deep purification of the gold-loaded organic phase and optimization of the reaction environment, create favorable conditions for subsequent oxalic acid back-extraction, and finally obtain high-purity gold powder with a purity not lower than 99.996%, and the gold back-extraction recovery rate is high.

Description

Technical Field

[0001] This invention belongs to the field of precious metal hydrometallurgical refining technology, and particularly relates to a multi-stage synergistic washing and purification method for crude gold purification using a gold-loaded organic phase after DBC extraction. Background Technology

[0002] In the field of hydrometallurgical refining of precious metals, purifying crude gold (such as that derived from anode mud, alloys, etc.) to high-purity gold (≥99.99%) is an important technical route, which usually involves steps such as crude gold electrolytic solution preparation, solvent extraction, and chemical reduction. Among these steps, the selective extraction of gold (III) from hydrochloric acid medium using dibutylcarbitol (DBC) is the core step, and the purification effect of the organic phase loaded after extraction directly determines the purity of the final product.

[0003] Existing technologies have explored washing and purification methods after DBC extraction. For example, Chinese patent CN101985691B discloses a method for preparing high-purity gold, with the process flow being: crude gold electrolysis to form a solution → DBC extraction → hydrochloric acid washing → oxalic acid back-extraction. A single concentration (0.5 mol / L) of hydrochloric acid is used for multi-stage countercurrent washing of the gold-loaded organic phase to remove impurities. Similarly, US patent US5942024A also describes multi-stage washing using 0.25-0.75 mol / L hydrochloric acid. While these technologies recognize the necessity of washing, their washing strategies are simplistic, using only hydrochloric acid with a fixed acidity. This makes it difficult to achieve targeted and deep removal of the complex impurity profile (such as Fe, Sb, Bi, Cu, etc.) in crude gold raw materials.

[0004] To further improve impurity removal, subsequent studies explored different acidities. For example, US Patent 9068245B2 discloses a process for recovering gold from anode mud, which involves multi-stage countercurrent washing with 1.5-3.0 mol / L hydrochloric acid after DBC extraction and optimizes the equipment layout. US Patent 8911533B2, targeting extremely low concentration gold solutions, proposes a strategy of independent circulation and concentration of extractants at each stage of multi-stage extraction, and mentions the use of hydrochloric acid washing to remove impurities such as iron.

[0005] In summary, while existing technologies have improved washing after DBC extraction, they still have significant shortcomings: First, the washing solution has a single concentration or function, making it difficult to synergistically and deeply remove various co-extraction and entrained impurities with different properties; second, the high concentration of chloride ions physically entrained in the supported organic phase generally ignores the severe inhibition of the subsequent oxalic acid back-extraction step, and there is a lack of consideration for actively regulating the organic phase environment to optimize the next process. Therefore, within the process framework of gold purification through DBC extraction, there is an urgent need to develop a dedicated purification method that can deeply and synergistically purify the gold-loaded organic phase and actively create the optimal reaction environment for its subsequent oxalic acid back-extraction. Summary of the Invention

[0006] To address the aforementioned problems in the existing technology, this invention provides a multi-stage synergistic washing purification method after DBC extraction for crude gold purification. The method is characterized by sequentially performing at least three washing steps on the gold-loaded organic phase obtained by extraction from a gold-containing chloride acidic solution using dibutylcarbidol:

[0007] (1) High acid impurity removal washing: The gold-loaded organic phase is contacted countercurrently or crosscurrently with a hydrochloric acid washing solution with a concentration of 1.5-4.0 mol / L to remove iron, antimony, and bismuth metal impurity ions that have been co-extracted into the organic phase;

[0008] (2) Medium acid conditioning washing: Acid washing solution with a concentration of 0.2-1.0 mol / L is used to contact the organic phase treated in step (1) in a countercurrent or cross-current manner to further remove residual metal impurities and reduce the acidity entrained in the organic phase;

[0009] (3) Low acid / water washing: Deionized water or extremely dilute acid solution with an acid concentration of less than 0.05 mol / L is used as washing liquid and is used to make countercurrent or cross-current contact with the organic phase after step (2) to remove chloride ions and water-soluble impurities entrained in the organic phase, so that the chloride ion concentration of the water phase entrained in the organic phase after washing is less than 0.1 mol / L.

[0010] Furthermore, before the high-acid impurity removal stage, a pre-washing stage step is also included, specifically, using a hydrochloric acid washing solution with a concentration of 2-6 mol / L to perform preliminary impurity removal on the gold-loaded organic phase.

[0011] Furthermore, the acid washing solution used in the intermediate acid conditioning stage is hydrochloric acid or nitric acid.

[0012] Furthermore, the washing solution used in the low-acid / water rinsing stage is deionized water.

[0013] Furthermore, the temperature of each washing stage is controlled between 15-40℃.

[0014] Furthermore, the washing at each stage is carried out in a mixing and clarification device, and the ratio of the washing liquid to the organic phase (A:O) is 1:5 to 1:1.

[0015] Furthermore, the method reduces the concentration of chloride ions entrained in the gold-loaded organic phase from above 0.5 mol / L before washing to below 0.1 mol / L after washing.

[0016] The present invention also provides a method for purifying crude gold, characterized by comprising the following steps:

[0017] (a) Electrolyze crude gold raw material to obtain an acidic solution containing gold chloride;

[0018] (b) The solution obtained in step (a) was extracted with dibutylcarbidol to obtain a gold-loaded organic phase;

[0019] (c) The gold-loaded organic phase obtained in step (b) is purified using the multi-stage synergistic washing and purification method described above;

[0020] (d) The gold-loaded organic phase purified in step (c) is back-extracted and reduced with oxalic acid or oxalate to obtain high-purity gold powder or gold ingots.

[0021] The method of the present invention has the following advantages:

[0022] (1) Achieving deep and synergistic purification of the gold-loaded organic phase, significantly improving the purity of the final product. Through a functional synergistic washing process of "high acid impurity removal - medium acid conditioning - low acid / water rinsing", co-extracted metal impurities and entrained impurities are systematically removed. The high acid impurity removal stage targets and back-extracts key impurities such as iron, antimony, and bismuth; the medium acid conditioning stage deeply purifies and adjusts the acidity; and the low acid / water rinsing stage thoroughly removes chloride ions. After purification by this process, the purity of the subsequently obtained gold powder can stably reach over 99.996%, far exceeding that of a single acid washing process.

[0023] (2) Actively optimizing the subsequent back-extraction reaction environment significantly improves gold recovery efficiency. A creative low-acid / water washing stage reduces the chloride ion concentration in the organic phase entrained with aqueous phase to below 0.1 mol / L, fundamentally solving the problem of high chloride ion concentration inhibiting oxalic acid back-extraction. This creates a low-chlorine, clean, ideal environment for back-extraction, accelerating the gold back-extraction rate and significantly increasing the back-extraction recovery rate to over 99.8%, thereby improving the overall metal recovery rate.

[0024] (3) The overall process exhibits strong adaptability and stability, possessing outstanding industrial application value. This synergistic washing method can be flexibly adjusted according to the impurity content of the raw materials, demonstrating strong adaptability. The deep-purified organic phase is returned to the extraction system, which is beneficial for maintaining the long-term, efficient, and stable operation of the extractant. The method has a clear process flow and is easy to implement by modifying existing extraction-back-extraction devices. While ensuring a stable output of high-purity gold, it reduces overall costs, resulting in significant economic benefits. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the multi-stage synergistic washing and purification process after DBC extraction according to the present invention. Detailed Implementation

[0026] Example 1

[0027] This embodiment demonstrates the standard three-stage synergistic washing process of the present invention.

[0028] Raw material preparation: Simulating actual production, an acidic solution containing gold chloride (gold concentration approximately 50 g / L, HCl concentration approximately 2.5 mol / L) was prepared. This solution was then subjected to a two-stage countercurrent extraction with a 50% (v / v) dibutylcarbitol (DBC, purity ≥99%) kerosene (sulfonation value <0.01%) solution to obtain a gold-loaded organic phase. This organic phase contained approximately 35 g / L of gold and also contained impurity ions such as Fe, Sb, Cu, and Bi, which were simulated for co-extraction.

[0029] Implementation steps:

[0030] Take 500 mL of the above-mentioned gold-loaded organic phase and perform the following three-stage countercurrent washing. Each stage of washing is carried out in a mixing and clarification tank. After mixing, the phases are allowed to stand for clarification for 5 minutes. After the two phases are completely separated, the lower aqueous phase is separated and the upper organic phase is transferred to the next stage.

[0031] (1) High acid impurity removal washing: Add 250 mL of 2.5 mol / L hydrochloric acid solution (A:O = 1:2) to the organic phase. Control the mixing temperature at 25℃ and stir for 5 minutes.

[0032] (2) Medium-acid conditioning washing: Add 250 mL of 0.5 mol / L hydrochloric acid solution (A:O = 1:2) to the organic phase after high-acid washing. Control the temperature at 25℃ and stir for 5 minutes.

[0033] (3) Low acid / water washing: Add 500 mL of deionized water (A:O = 1:1) to the organic phase after medium acid washing. Control the temperature at 25℃ and stir for 3 minutes.

[0034] Detection and Effect Analysis: The purified gold-loaded organic phase sample after final washing was taken, and the entrained aqueous phase was separated by centrifugation. The Cl content was determined by ion chromatography. - The concentration was 0.08 mol / L, lower than 0.1 mol / L. This pure organic phase was heated to 80℃ and mixed with a 1.0 mol / L oxalic acid solution (pH adjusted to 1.5 with a trace amount of hydrochloric acid) at a volume ratio of organic phase:aqueous phase (O:A) = 2:1. The mixture was back-extracted and reduced at 80℃ with stirring for 2 hours. After the reaction, the mixture was filtered, washed, and dried to obtain sponge gold powder. Inductively coupled plasma mass spectrometry (ICP-MS) analysis showed that the gold powder purity was 99.996%, with the main impurities being: Ag < 5 ppm, Cu < 2 ppm, Fe < 1 ppm, and Sb < 1 ppm. The calculated gold back-extraction recovery rate was higher than 99.8%.

[0035] Example 2

[0036] This embodiment demonstrates a four-stage synergistic washing process, including a "pre-washing stage," for gold-loaded organic phases with higher impurity content.

[0037] Raw material preparation: The gold-loaded organic phase was prepared using the same method as in Example 1, but by adding Fe, Sb, and Bi salts to the gold chloride acidic solution, the total concentration of co-extracted impurities was approximately 3-5 times that of Example 1, and the gold concentration in the gold-loaded organic phase was approximately 32 g / L.

[0038] Implementation steps:

[0039] (0) Pre-washing: Add a 4.0 mol / L hydrochloric acid solution to the gold-loaded organic phase for washing (A:O = 1:3, 25℃, mix for 5 minutes).

[0040] (1) High acid impurity removal washing: The pre-washed organic phase is washed with 2.0 mol / L hydrochloric acid solution (A:O = 1:2, 25℃, mix for 5 minutes).

[0041] (2) Medium acid conditioning washing: The organic phase after high acid washing is washed with 0.3 mol / L hydrochloric acid solution (A:O = 1:2, 25℃, mix for 5 minutes).

[0042] (3) Low acid / water washing: Wash the organic phase after medium acid washing with deionized water (A:O = 1:1, 25℃, mix for 3 minutes).

[0043] Detection and Effect Analysis: Determination of Cl in the final organic phase entrained with aqueous phase - The concentration is 0.04 mol / L.

[0044] Under the same conditions, oxalic acid back-extraction yielded a gold recovery rate of over 99.9%. The resulting gold powder, analyzed by ICP-MS, showed a purity of up to 99.997%, with a further reduction in total impurities.

[0045] Example 3

[0046] This embodiment demonstrates an implementation at the lower end of the process parameter range, using nitric acid as a medium-acid conditioning agent. The raw materials and equipment are the same as in Embodiment 1.

[0047] Implementation steps:

[0048] (1) High acid impurity removal washing: Wash with a 1.5 mol / L hydrochloric acid solution (A:O = 1:4, temperature 40℃, mix for 5 minutes).

[0049] (2) Medium acid conditioning washing: The organic phase after high acid washing is washed with 0.2 mol / L nitric acid (HNO3) solution (A:O = 1:4, temperature 40℃, mix for 5 minutes).

[0050] (3) Low acid / water washing: The organic phase after medium acid washing is washed with a very dilute hydrochloric acid solution with a concentration of 0.01 mol / L (A:O = 1:2, temperature 40℃, mix for 3 minutes).

[0051] Detection and Effect Analysis: Determination of Cl in the final organic phase entrained with aqueous phase - The concentration was 0.09 mol / L. After oxalic acid back-extraction, the purity of the obtained gold powder reached 99.995%, and the gold back-extraction recovery rate was >99.7%. The results show that even with lower acidity parameters and different types of acid washing, the method of the present invention can still achieve the goals of deep purification and effective dechlorination.

[0052] Comparative Example 1

[0053] The same gold-loaded organic phase and experimental equipment as in Example 1 were used, and a three-stage synergistic washing process was performed according to the steps and parameters of Example 1 (2.5 mol / L HCl → 0.5 mol / L HCl → deionized water). The results were the same as in Example 1; after washing, Cl... - Concentration <0.1 mol / L, gold powder purity 99.996%.

[0054] Comparative Example 2

[0055] The gold-loaded organic phase was exactly the same as that used in Comparative Example 1. The washing steps were simulated only by existing techniques, using a single concentration (0.5 mol / L) hydrochloric acid solution for three-stage countercurrent washing (A:O = 1:2 per stage, 25°C, mixing for 5 minutes). This approach omits the high-acid impurity removal stage and the low-acid / water rinsing stage of this invention, only repeating operations similar to the medium-acid conditioning stage.

[0056] Experimental results: After washing, the residual amounts of metallic impurities such as Fe and Sb in the organic phase were significantly higher than those in Comparative Example 1. The Cl content in the entrained aqueous phase was determined. - The concentration was as high as approximately 0.8 mol / L. When this organic phase was subjected to oxalic acid back-extraction under the exact same conditions as Comparative Example 1, the purity of the obtained gold powder was only 99.98%, and ICP-MS analysis showed significantly higher contents of Ag and Fe (both >20 ppm). The back-extraction rate was also observed to be slower than that of Comparative Example 1.

[0057] The above description is a preferred embodiment of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A multi-stage synergistic washing and purification method after DBC extraction for crude gold purification, characterized in that, The method includes sequentially performing the following at least three washing steps on the gold-loaded organic phase obtained by extraction from a gold-containing chloride acidic solution using dibutylcarbitol: (1) High acid impurity removal washing: The gold-loaded organic phase is contacted countercurrently or crosscurrently with a hydrochloric acid washing solution with a concentration of 1.5-4.0 mol / L to remove iron, antimony, and bismuth metal impurity ions that have been co-extracted into the organic phase; (2) Medium acid conditioning washing: Acid washing solution with a concentration of 0.2-1.0 mol / L is used to contact the organic phase treated in step (1) in a countercurrent or cross-current manner to further remove residual metal impurities and reduce the acidity entrained in the organic phase; (3) Low acid / water washing: Deionized water or extremely dilute acid solution with an acid concentration of less than 0.05 mol / L is used as washing liquid and is used to make countercurrent or cross-current contact with the organic phase after step (2) to remove chloride ions and water-soluble impurities entrained in the organic phase, so that the chloride ion concentration of the water phase entrained in the organic phase after washing is less than 0.1 mol / L.

2. The method according to claim 1, characterized in that, Before the high-acid impurity removal stage, a pre-washing stage is also included, which specifically involves using a hydrochloric acid washing solution with a concentration of 2-6 mol / L to perform preliminary impurity removal on the gold-loaded organic phase.

3. The method according to claim 1, characterized in that, The acid washing solution used in the medium-acid conditioning stage is hydrochloric acid or nitric acid.

4. The method according to claim 1, characterized in that, The washing solution used in the low-acid / water rinsing grade is deionized water.

5. The method according to claim 1, characterized in that, The temperature of each washing stage is controlled between 15-40℃.

6. The method according to claim 1, characterized in that, The washing at each stage is carried out in a mixing and clarification device, with the ratio of the washing liquid to the organic phase being 1:5 to 1:

1.

7. The method according to claim 1, characterized in that, The method reduces the concentration of chloride ions entrained in the gold-loaded organic phase from above 0.5 mol / L before washing to below 0.1 mol / L after washing.

8. A method for purifying crude gold, characterized in that, Includes the following steps: (a) Electrolyze crude gold raw material to obtain an acidic solution containing gold chloride; (b) The solution obtained in step (a) was extracted with dibutylcarbidol to obtain a gold-loaded organic phase; (c) The gold-loaded organic phase obtained in step (b) is purified using the multi-stage synergistic washing and purification method according to any one of claims 1-7; (d) The gold-loaded organic phase purified in step (c) is back-extracted and reduced with oxalic acid or oxalate to obtain high-purity gold powder or gold ingots.

Images