A method for the direct extraction purification of a solution containing iron

Abstract

The application provides a method for preparing an iron-containing solution through direct extraction and purification, comprising the following steps: mixing an iron solution with hydrochloric acid and a complex stabilizer to obtain a pretreated solution; using a complex organic phase to extract the pretreated solution to obtain a loaded organic phase; the complex organic phase comprises a composite extractant; washing the loaded organic phase to obtain a purified organic phase; sequentially performing first stripping and second stripping on the purified organic phase to obtain an iron-containing solution; the stripping agent used in the second stripping comprises a chloride salt solution, and the concentration gradient of the stripping agent used in the second stripping is reduced. The method for preparing an iron-containing solution through direct extraction and purification provided by the application can enhance the selectivity of subsequent extraction and separation by adding a complex stabilizer before extraction, then uses a composite extractant for extraction, and finally uses a gradient stripping method to realize selective and efficient stripping of iron, and the method can balance high stripping rate, product purity and stability of the organic phase.

Description

Technical Field

[0001] This invention belongs to the field of hydrometallurgical technology and relates to a method for directly extracting and purifying iron-containing solutions. Background Technology

[0002] Among the methods for recovering iron-containing materials, the most widely used process is the hydrochloric acid dissolution method, which involves leaching the iron-containing material with hydrochloric acid to obtain a strongly acidic hydrochloric acid leaching solution for iron. However, the hydrochloric acid leaching solution for iron contains many impurities. Existing technologies typically use extraction methods to remove impurities. For example, CN115161499A discloses a one-step extraction method for separating and recovering rare earth elements and iron. This method first mixes trioctylmethylammonium oxalate, tributyl phosphate, and sulfonated kerosene to obtain an organic phase; mixes the organic phase and the extraction solution at a volume ratio of 1:(1~5), and performs countercurrent extraction for 1~5 stages to obtain a loaded organic phase and raffinate; filters the raffinate to obtain rare earth oxalate; mixes the loaded organic phase and the back-extraction agent at a volume ratio of (1~5):1, and performs countercurrent back-extraction for 1~5 stages to obtain an iron-rich solution and a lean organic phase; filters the iron-rich solution to obtain ferric hydroxide; and mixes the lean organic phase with an oxalic acid solution, separates the phases, and obtains a regenerated organic phase. However, existing technologies have technical problems in the process of removing impurities from iron leaching solutions in hydrochloric acid system, such as low efficiency in separating metal impurities, insufficient recycling rate of organic phase, and difficulty in ensuring the purity of subsequent products. Summary of the Invention

[0003] The purpose of this invention is to provide a method for directly extracting and purifying iron-containing solutions. The method involves adding a complexing stabilizer before extraction to selectively complex with iron ions, thereby enhancing the selectivity of subsequent extraction and separation. Then, a composite extractant is used for extraction, and finally, a gradient back-extraction method is employed. By utilizing chloride ion complexation and concentration gradient, selective and efficient back-extraction of iron is achieved, taking into account high back-extraction rate, product purity, and organic phase stability, which is conducive to safe, low-consumption, and continuous separation and recovery.

[0004] To achieve this objective, the present invention adopts the following technical solution:

[0005] This invention provides a method for preparing an iron-containing solution by direct extraction and purification, the method comprising the following steps:

[0006] (1) Mix the hydrochloric acid leaching iron solution with the complexing stabilizer to obtain the pretreatment solution;

[0007] (2) The pretreated liquid was extracted using a compounded organic phase to obtain a loaded organic phase;

[0008] The organic phase of the compound includes a composite extractant, which includes quaternary ammonium chloride, organic acid, phosphate ester compound and polyol;

[0009] (3) The loaded organic phase described in step (2) is washed to obtain a purified organic phase;

[0010] (4) The purified organic phase described in step (3) is subjected to a first back-extraction and a second back-extraction in sequence to obtain an iron-containing solution;

[0011] The second back-extraction uses a chloride salt solution as the back-extraction agent, and the concentration gradient of the back-extraction agent decreases during the second back-extraction process.

[0012] Before extraction, the method of this invention involves mixing a hydrochloric acid solution for leaching iron with a complexing stabilizer. The complexing stabilizer can selectively react with Fe. 3+ Synergistic complexation further enhances Fe 3+ The stability of the extractant is improved, while the formation of complex anions between aluminum, chromium, and chloride ions is inhibited, enhancing the selectivity of subsequent extraction and separation. Then, a specific composite extractant is used for extraction, utilizing high chloride complexation during extraction to reduce Fe... 3+ The tetrachloroferric complex anion is generated and enters the organic phase, while aluminum ions, chromium ions, and alkali metal impurities remain in the raffinate and are discharged. After the extraction is completed, the loaded organic phase is washed, and then the purified organic phase is back-extracted. In the second back-extraction, a chloride salt solution is used for gradient back-extraction. The selective and efficient back-extraction of iron is achieved by using chloride ion complexation and concentration gradient, which takes into account high back-extraction rate, product purity, and organic phase stability. This facilitates safe and low-consumption continuous separation and recovery, thereby obtaining a high-purity iron-containing solution.

[0013] The composite extractant of this invention comprises quaternary ammonium chloride, organic acid, phosphate ester compound, and polyol. The quaternary ammonium chloride acts as the main extractant, capable of extracting iron ions through anion exchange (or ion association) mechanism. The organic acid acts as a modifier, altering the properties (or stability) of the iron extractant, making it difficult to back-extract with water but allowing for complete back-extraction with dilute acid. The phosphate ester compound acts as a co-extractant, significantly enhancing the Fe ion extraction capacity through coordination enrichment. 3+ The extraction loading capacity and mass transfer rate are improved by the polyol, which acts as a modifier to improve the physical properties of the extraction system (such as preventing the formation of a third phase, promoting phase separation, and improving the compatibility of the extractant).

[0014] Preferably, the molar ratio of iron ions to complexing stabilizer in the hydrochloric acid leaching iron solution in step (1) is 100:(0.1-0.5), for example, it can be 100:0.1, 100:0.2, 100:0.3, 100:0.4 or 100:0.5, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0015] Preferably, the complexing stabilizer in step (1) includes sodium citrate.

[0016] Preferably, in the hydrochloric acid leaching solution for iron in step (1), the iron ion concentration is 100 g / L-140 g / L, for example, 100 g / L, 110 g / L, 120 g / L, 130 g / L, or 140 g / L; the hydrogen ion concentration is 1.2 mol / L-1.8 mol / L, for example, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, 1.6 mol / L, 1.7 mol / L, or 1.8 mol / L; the cobalt ion concentration is 40 mg / L-50 mg / L, for example, 40 mg / L, 45 mg / L, or 50 mg / L; and the manganese ion concentration is 260 mg / L-300 mg / L, for example, 260 mg / L-300 mg / L. 60 mg / L, 270 mg / L, 280 mg / L, 290 mg / L, or 300 mg / L; aluminum ion concentration of 3 g / L-4 g / L, for example, 3 g / L, 3.5 g / L, or 4 g / L; chromium ion concentration of 2 g / L-3 g / L, for example, 2 g / L, 2.5 g / L, or 3 g / L; nickel ion concentration of 60 mg / L-80 mg / L, for example, 60 mg / L, 70 mg / L, or 60 mg / L; total concentration of sodium, calcium, and magnesium ions of 25 mg / L-35 mg / L, for example, 25 mg / L, 30 mg / L, or 35 mg / L, but not limited to the listed values, and other unlisted values ​​within the range also apply.

[0017] Preferably, the hydrochloric acid leaching iron solution in step (1) is first mixed with a reducing agent to reduce hexavalent chromium to trivalent chromium, then mixed with a complexing stabilizer, and then filtered to obtain a pretreated solution.

[0018] Before extraction, this invention adds a reducing agent to the feed solution to reduce trace amounts of hexavalent chromium to trivalent chromium, which facilitates the subsequent separation of iron and chromium.

[0019] Preferably, when the hydrochloric acid leaching iron solution in step (1) is first mixed with the reducing agent, the amount of the reducing agent added to the hydrochloric acid leaching iron solution is 2 g / L-3 g / L, for example, it can be 2 g / L, 2.5 g / L or 3 g / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0020] Preferably, the reducing agent comprises ferrous chloride.

[0021] Preferably, the organic phase in step (2) comprises 0.1 mol / L to 0.5 mol / L of quaternary ammonium chloride, for example, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L or 0.5 mol / L; 3 wt% to 8 wt% of organic acid, for example, 3 wt%, 5 wt%, 7 wt% or 8 wt%; 0.05 mol / L to 0.1 mol / L of phosphate ester compound, for example, 0.05 mol / L, 0.05 mol / L, 0.07 mol / L, 0.09 mol / L or 0.1 mol / L; 10 wt% to 15 wt% of polyol, for example, 10 wt%, 11 wt%, 12 wt%, 13 wt% or 15 wt%; and the balance being a diluent.

[0022] Preferably, the organic phase in step (2) is obtained by mixing quaternary ammonium chloride, organic acid, phosphate ester compound, polyol and diluent at room temperature for 30 min-40 min. For example, it can be 30 min, 35 min or 40 min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0023] Preferably, the quaternary ammonium chloride in step (2) includes any one or a combination of at least two of dodecyltrimethylammonium chloride, dodecyldimethylbenzylammonium chloride, or tetramethylammonium chloride.

[0024] Preferably, the organic acid in step (2) is organic acid HB (acetic acid or citric acid).

[0025] Preferably, the phosphate ester compound in step (2) includes tributyl phosphate.

[0026] Preferably, the polyol in step (2) includes 2-octanol.

[0027] Preferably, the diluent comprises sulfonated kerosene.

[0028] Preferably, the extraction method in step (2) is a 5-10 stage countercurrent extraction, for example, it can be 5, 6, 7, 8, 9 or 10 stages.

[0029] Preferably, the O / A ratio of the extraction in step (2) is 1:(1-3), for example, it can be 1:1, 1:2 or 1:3, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0030] Preferably, the extraction temperature in step (2) is 25℃-35℃, for example, it can be 25℃, 27℃, 29℃, 31℃, 33℃ or 35℃; the equilibrium pH is 0.18-1.0, for example, it can be 0.18, 0.3, 0.5, 0.7, 0.9 or 1.0, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0031] Preferably, the washing liquid used in step (3) includes a hydrochloric acid solution containing ammonium chloride.

[0032] The washing liquid used in the present invention contains ammonium chloride, which can wash away cobalt and manganese impurities entrained in the organic phase by salting out, while stabilizing the iron complex anion structure in the organic phase to obtain a purified loaded organic phase.

[0033] Preferably, the concentration of ammonium chloride in the washing solution is 0.02 mol / L-0.04 mol / L, for example, it can be 0.02 mol / L, 0.025 mol / L, 0.03 mol / L, 0.035 mol / L or 0.04 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0034] Preferably, the pH of the washing solution is 1.5-2.0, for example, it can be 1.5, 1.7, 1.9 or 2.0, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0035] Preferably, the washing method in step (3) includes level 1-2 countercurrent washing.

[0036] Preferably, the stripping agent used in step (4) of the first stripping includes pure water.

[0037] Preferably, in step (4), the first back-extraction yields a cobalt-manganese recovery solution.

[0038] This invention first uses pure water back-extraction to further refine and remove trace amounts of residual cobalt and manganese impurities from the organic phase, resulting in a cobalt- and manganese-enriched recovery solution.

[0039] Preferably, the number of stages of the second back-extraction in step (4) is 5 to 10, for example, it can be 5, 6, 7, 8, 9 or 10 stages, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0040] Preferably, in step (4) the second back-extraction process, the back-extraction agent used in the first to third stages of back-extraction is a chloride salt solution with a concentration of 0.01 mol / L to 0.03 mol / L, for example, 0.01 mol / L, 0.015 mol / L, 0.02 mol / L, 0.025 mol / L or 0.03 mol / L; the concentration of the chloride salt solution used in subsequent stages decreases gradually from 0.01 mol / L to 0.03 mol / L until the solution is pure water.

[0041] Preferably, the chloride salt solution includes a sodium chloride solution.

[0042] The second back-extraction of this invention is an iron-selective gradient back-extraction stage, which sets 5-10 stages of low-salt gradient countercurrent back-extraction. The back-extraction agent used in stages 1-3 is a 0.01-0.03 mol / L sodium chloride solution. In the later stages, the salt concentration is gradually reduced to pure water, and the chloride ion concentration is gradually reduced to achieve gentle desorption of iron, avoiding phase fluctuations, and obtaining a low-sodium salt high-purity ferric chloride solution.

[0043] The organic phase obtained by back-extraction in this invention is regenerated by multi-stage wet washing at room temperature to remove residual trace amounts of salt and flocculent matter, thereby enabling the organic phase to be recycled.

[0044] Preferably, in step (4), the temperatures of the first and second back-extractions are independently 25°C-35°C, for example, 25°C, 30°C or 35°C; the ratio of O / A is 1:(1-3), for example, 1:1, 1:2 or 1:3, but not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0045] Preferably, in step (4), the stirring speed of the first back-extraction and the second back-extraction is independently 200 r / min-300 r / min, for example, it can be 200 r / min, 250 r / min or 300 r / min; the time of single-stage back-extraction is independently 20 min-25 min, for example, it can be 20 min, 22 min, 24 min or 25 min, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0046] Preferably, after obtaining the iron-containing solution in step (4), a sulfate removal step and a purification step are also performed.

[0047] Preferably, the sulfate removal step includes the following steps:

[0048] After heating the iron-containing solution obtained in step (4), add barium salt solution to react, then allow it to stand (to precipitate barium sulfate crystals) and filter.

[0049] Preferably, the temperature rises to 40℃-50℃, for example, 40℃, 45℃ or 50℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0050] Preferably, based on the barium ions in the barium salt solution, the amount of barium salt solution added is 1.05 to 1.1 times the molar equivalent of sulfate, for example, it can be 1.05 times, 1.07 times, 1.09 times or 1.1 times, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0051] Preferably, the stirring rate of the reaction is 200 r / min-300 r / min, for example, 200 r / min, 250 r / min or 300 r / min; the time is 20 min-30 min, for example, 20 min, 25 min or 30 min, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0052] Preferably, the refining step includes precision filtration of the solution obtained in the sulfate removal step to remove trace suspended solids and fine flocculent residues in the solution, ultimately obtaining a high-purity ferric chloride product solution.

[0053] Preferably, the filter cloth used in the precision filtration has a pore size of 0.45μm-1.0μm, such as 0.45μm, 0.5μm, 0.7μm, 0.9μm or 1.0μm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0054] Compared with the prior art, the present invention has the following beneficial effects:

[0055] The present invention provides a method for preparing iron-containing solutions through direct extraction and purification. Before extraction, the hydrochloric acid solution for leaching iron is mixed with a complexing stabilizer. The complexing stabilizer selectively reacts with Fe. 3+ Synergistic complexation further enhances Fe 3+ The stability of the extractant is improved, while the formation of complex anions between aluminum, chromium, and chloride ions is inhibited, thus enhancing the selectivity of subsequent extraction and separation. Then, a specific composite extractant is used for extraction, utilizing high chloride complexation during extraction to reduce Fe... 3+ The tetrachloroferric complex anion is generated and enters the organic phase, while aluminum ions, chromium ions, and alkali metal impurities remain in the raffinate and are discharged. After extraction, the loaded organic phase is washed, and then the purified organic phase is back-extracted. In the second back-extraction, a chloride salt solution is used for gradient back-extraction. The selective and efficient back-extraction of iron is achieved by using chloride ion complexation and concentration gradient, which takes into account high back-extraction rate, product purity, and organic phase stability. This facilitates safe and low-consumption continuous separation and recovery, thereby obtaining a high-purity iron-containing solution. Detailed Implementation

[0056] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0057] Example 1

[0058] This embodiment provides a method for directly extracting and purifying iron-containing solutions, the method comprising the following steps:

[0059] (1) Pretreatment of the feed solution: The feed solution is a hydrochloric acid leaching solution with a free hydrogen ion concentration of 1.5 mol / L, an iron ion content of 120 g / L, a cobalt ion concentration of 46 mg / L, a manganese ion concentration of 272 mg / L, an aluminum ion concentration of 3.22 g / L, a chromium ion concentration of 2.4 g / L, a nickel ion concentration of 70 mg / L, and a total concentration of sodium, calcium and magnesium ions of 35 mg / L. Ferrous chloride (addition amount of 2 g / L) is added to the feed solution to reduce trace hexavalent chromium to trivalent chromium. Then sodium citrate is added as a complexing stabilizer. The suspended solids in the feed solution are removed by precision filtration with a filter cloth with a pore size of 0.45 μm to obtain the pretreated feed solution.

[0060] The molar ratio of iron ions to complexing stabilizer in the hydrochloric acid leaching iron solution is 100:0.3.

[0061] (2) Extraction and separation: Quaternary ammonium chloride (specifically dodecyltrimethylammonium chloride), organic acid HB, tributyl phosphate, 2-octanol and sulfonated kerosene are stirred at room temperature for 35 min to obtain a compound organic phase. The compound organic phase contains 0.3 mol / L quaternary ammonium chloride, 5 wt% organic acid HB, 0.08 mol / L tributyl phosphate, 12 wt% 2-octanol and the balance sulfonated kerosene.

[0062] The pretreated liquid from step (1) was subjected to 8-stage countercurrent extraction using a compounded organic phase, with the phase O / A = 1 / 1, the temperature at 30°C and the equilibrium pH at 0.5, to obtain a loaded organic phase;

[0063] (3) Washing of the loaded organic phase: The loaded organic phase described in step (2) is washed in two stages of countercurrent washing with a dilute hydrochloric acid solution containing 0.03 mol / L ammonium chloride and pH 1.8 to obtain a purified organic phase;

[0064] (4) Stepwise gradient low-salt back-extraction and organic phase regeneration: The purified organic phase described in step (3) is subjected to a first back-extraction using pure water;

[0065] Then, an 8-stage low-salt gradient countercurrent back-extraction was set up for the second back-extraction. In the first three stages of back-extraction, the back-extraction agent used was 0.02 mol / L sodium chloride solution. In subsequent stages, the concentration of the 0.02 mol / L sodium chloride solution was gradually reduced to pure water to obtain a low-sodium salt high-purity ferric chloride solution and an organic phase. The organic phase was then regenerated by a multi-stage wet washing process at room temperature to remove residual trace salts and flocculent matter, resulting in a regenerated organic phase.

[0066] The temperature of the first and second back-extractions was controlled at 30°C, the ratio of O / A was 1 / 1, the stirring speed was 250 r / min, and the single-stage back-extraction time was 25 min.

[0067] (5) Deep removal of sulfate: The low sodium salt high-purity ferric chloride solution obtained in step (4) is heated to 45°C, and a barium salt solution with a sulfate molar equivalent of 1.1 times is added. The stirring speed is controlled at 250 r / min and the reaction time is 25 min. After the reaction is completed, the barium sulfate crystals are allowed to precipitate and filtered with a 0.8 μm filter cloth to remove the residue.

[0068] (6) Deep purification: Use a 0.45μm precision filter cloth to filter out trace suspended matter and fine flocculent residue in the solution obtained in step (5) to obtain ferric chloride finished solution.

[0069] Example 2

[0070] This embodiment provides a method for directly extracting and purifying iron-containing solutions, the method comprising the following steps:

[0071] (1) Pretreatment of the feed solution: The feed solution is a hydrochloric acid leaching iron solution with a free hydrogen ion concentration of 1.2 mol / L, an iron ion content of 140 g / L, a cobalt ion concentration of 50 mg / L, a manganese ion concentration of 260 mg / L, an aluminum ion concentration of 3 g / L, a chromium ion concentration of 2 g / L, a nickel ion concentration of 60 mg / L, and a total sodium ion, calcium ion and magnesium ion concentration of 30 mg / L. Ferrous chloride (3 g / L) is added to the feed solution to reduce trace hexavalent chromium to trivalent chromium. Then sodium citrate is added as a complexing stabilizer. The suspended solids in the feed solution are removed by precision filtration with a filter cloth with a pore size of 1 μm to obtain the pretreated feed solution.

[0072] The molar ratio of iron ions to complexing stabilizer in the hydrochloric acid leaching iron solution is 100:0.1.

[0073] (2) Extraction and separation: Quaternary ammonium chloride (specifically dodecyltrimethylammonium chloride), organic acid HB, tributyl phosphate, 2-octanol and sulfonated kerosene are stirred at room temperature for 40 min to obtain a compound organic phase. The compound organic phase contains 0.1 mol / L quaternary ammonium chloride, 3 wt% organic acid HB, 0.1 mol / L tributyl phosphate, 15 wt% 2-octanol and the balance sulfonated kerosene.

[0074] The pretreated liquid from step (1) was subjected to 10-stage countercurrent extraction using a compounded organic phase, with the phase O / A = 1 / 1, the temperature at 25°C and the equilibrium pH at 1.0, to obtain a loaded organic phase;

[0075] (3) Washing of the loaded organic phase: The loaded organic phase described in step (2) is washed in two stages of countercurrent washing with a dilute hydrochloric acid solution containing 0.04 mol / L ammonium chloride and pH 1.5 to obtain a purified organic phase;

[0076] (4) Stepwise gradient low-salt back-extraction and organic phase regeneration: The purified organic phase described in step (3) is subjected to a first back-extraction using pure water;

[0077] Then, a 5-stage low-salt gradient countercurrent back-extraction was set up for the second back-extraction. In the first three stages of back-extraction, the back-extraction agent used was 0.01 mol / L sodium chloride solution. In subsequent stages, the concentration of the 0.01 mol / L sodium chloride solution was gradually reduced to pure water to obtain a low-sodium salt high-purity ferric chloride solution and an organic phase. The organic phase was then regenerated by a multi-stage wet washing process at room temperature to remove residual trace salts and flocculent matter, resulting in a regenerated organic phase.

[0078] The temperature of the first and second back-extractions was controlled at 35°C, the phase ratio O / A = 1 / 1, the stirring speed was 300 r / min, and the single-stage back-extraction time was 25 min.

[0079] (5) Deep removal of sulfate: The low sodium salt high-purity ferric chloride solution obtained in step (4) is heated to 40°C, and a barium salt solution with a sulfate molar equivalent of 1.05 times is added. The stirring speed is controlled at 200 r / min and the reaction time is 30 min. After the reaction is completed, the barium sulfate crystals are allowed to precipitate and filtered with a 1.0 μm filter cloth to remove the residue.

[0080] (6) Deep purification: Use a 0.8μm precision filter cloth to filter out trace suspended matter and fine flocculent residue in the solution obtained in step (5) to obtain ferric chloride finished solution.

[0081] Example 3

[0082] This embodiment provides a method for directly extracting and purifying iron-containing solutions, the method comprising the following steps:

[0083] (1) Pretreatment of the feed solution: The feed solution is a hydrochloric acid leaching iron solution with a free hydrogen ion concentration of 1.8 mol / L, an iron ion content of 100 g / L, a cobalt ion concentration of 40 mg / L, a manganese ion concentration of 300 mg / L, an aluminum ion concentration of 4 g / L, a chromium ion concentration of 3 g / L, a nickel ion concentration of 78 mg / L, and a total sodium ion, calcium ion and magnesium ion concentration of 34 mg / L. Ferrous chloride (addition amount of 2 g / L) is added to the feed solution to reduce trace hexavalent chromium to trivalent chromium. Then sodium citrate is added as a complexing stabilizer. The suspended solids in the feed solution are removed by precision filtration with a filter cloth with a pore size of 0.45 μm to obtain the pretreated feed solution.

[0084] The molar ratio of iron ions to complexing stabilizer in the hydrochloric acid leaching iron solution is 100:0.5.

[0085] (2) Extraction and separation: Quaternary ammonium chloride (specifically tetramethylammonium chloride), organic acid HB, tributyl phosphate, 2-octanol and sulfonated kerosene are stirred at room temperature for 30 min to obtain a compound organic phase. The compound organic phase contains 0.5 mol / L quaternary ammonium chloride, 8 wt% organic acid HB, 0.05 mol / L tributyl phosphate, 10 wt% 2-octanol and the balance sulfonated kerosene.

[0086] The pretreated liquid from step (1) was subjected to five-stage countercurrent extraction using a compounded organic phase, with the phase O / A = 1 / 1, the temperature at 35°C, and the equilibrium pH at 0.18, to obtain a loaded organic phase.

[0087] (3) Washing of the loaded organic phase: The loaded organic phase described in step (2) is subjected to a first-stage countercurrent wash with a dilute hydrochloric acid solution containing 0.02 mol / L ammonium chloride and pH 2.0 to obtain a purified organic phase;

[0088] (4) Stepwise gradient low-salt back-extraction and organic phase regeneration: The purified organic phase described in step (3) is subjected to a first back-extraction using pure water;

[0089] Then, a 10-stage low-salt gradient countercurrent back-extraction was set up for the second back-extraction. In the first three stages of back-extraction, the back-extraction agent used was a 0.03 mol / L sodium chloride solution. In subsequent stages, the concentration of the 0.03 mol / L sodium chloride solution was gradually reduced to pure water to obtain a low-sodium salt high-purity ferric chloride solution and an organic phase. The organic phase was then regenerated by a multi-stage wet washing process at room temperature to remove residual trace salts and flocculent matter, resulting in a regenerated organic phase.

[0090] The temperature of the first and second back-extractions was controlled at 25°C, the ratio of O / A was 1 / 1, the stirring speed was 200 r / min, and the single-stage back-extraction time was 20 min.

[0091] (5) Deep removal of sulfate: The low sodium salt high-purity ferric chloride solution obtained in step (4) is heated to 50°C, and a barium salt solution with a sulfate molar equivalent of 1.1 times is added. The stirring speed is controlled at 300 r / min and the reaction time is 20 min. After the reaction is completed, the barium sulfate crystals are allowed to precipitate and filtered with a 0.45 μm filter cloth to remove the residue.

[0092] (6) Deep purification: Use a 0.45μm precision filter cloth to filter out trace suspended matter and fine flocculent residue in the solution obtained in step (5) to obtain ferric chloride finished solution.

[0093] Example 4

[0094] This embodiment provides a method for directly extracting and purifying to prepare an iron-containing solution. Except for the fact that the dilute hydrochloric acid solution in step (3) does not contain ammonium chloride, the method is the same as in Example 1.

[0095] Example 5

[0096] This embodiment provides a method for directly extracting and purifying iron-containing solutions. Except for step (4), in the second back-extraction, the back-extraction agent used in the first stage back-extraction is a 0.02 mol / L sodium chloride solution, and the concentration of the 0.02 mol / L sodium chloride solution is gradually reduced to pure water in subsequent stages. The rest of the method is the same as in Example 1.

[0097] Example 6

[0098] This embodiment provides a method for directly extracting and purifying iron-containing solutions. Except for step (4), in the second back-extraction, the back-extraction agent used in the first to fifth stages of back-extraction is a 0.02 mol / L sodium chloride solution, and the concentration of the 0.02 mol / L sodium chloride solution is gradually reduced to pure water in subsequent stages. The rest of the method is the same as in Example 1.

[0099] Comparative Example 1

[0100] This comparative example provides a method for preparing an iron-containing solution by direct extraction and purification. The method is the same as in Example 1 except that sodium citrate is not added as a complexing stabilizer in step (1).

[0101] Comparative Example 2

[0102] This comparative example provides a method for preparing an iron-containing solution by direct extraction and purification. Except for step (4), in which the second back-extraction uses a 0.02 mol / L sodium chloride solution for each back-extraction stage, the method is the same as in Example 1.

[0103] The purity of iron (concentration of iron in solution / concentration of total metal elements) and the iron recovery rate in the ferric chloride solution obtained in the above examples and comparative examples are shown in Table 1:

[0104] Table 1

[0105]

[0106] As can be seen from Table 1 above:

[0107] As shown in Example 1 and Comparative Example 1, the direct extraction and purification method for preparing iron-containing solutions provided by the present invention, by adding a complexing stabilizer before extraction, is beneficial to improving the stability of iron ions and enhancing the selectivity of subsequent extraction and separation, thereby improving the purity of the ferric chloride product solution and the iron recovery rate. As shown in Example 1 and Comparative Example 2, the stepwise gradient low-salt back-extraction method of the present invention can achieve selective iron back-extraction and gentle iron desorption, avoid phase fluctuations, and take into account high back-extraction rate, product purity, and organic phase stability. As shown in Example 1 and Example 4, ammonium chloride is added to the hydrochloric acid washing solution during washing, which can further improve the washing effect. As shown in Example 1 and Examples 5-6, in the second back-extraction of the present invention, it is preferable that the concentration of the back-extraction agent used in the first to third stages of back-extraction remains unchanged, and the concentration of the back-extraction agent is gradually decreased in subsequent stages to improve the selective iron back-extraction effect, thereby further improving the purity of the ferric chloride product solution and the iron recovery rate.

[0108] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for directly extracting and purifying iron-containing solutions, characterized in that, The method for preparing iron-containing solutions by direct extraction and purification includes the following steps: (1) Mix the hydrochloric acid leaching iron solution with the complexing stabilizer to obtain the pretreatment solution; (2) The pretreated liquid was extracted using a compounded organic phase to obtain a loaded organic phase; The organic phase of the compound includes a composite extractant, which includes quaternary ammonium chloride, organic acid, phosphate ester compound and polyol; (3) The loaded organic phase described in step (2) is washed to obtain a purified organic phase; (4) The purified organic phase described in step (3) is subjected to a first back-extraction and a second back-extraction in sequence to obtain an iron-containing solution; The second back-extraction uses a chloride salt solution as the back-extraction agent, and the concentration gradient of the back-extraction agent decreases during the second back-extraction process.

2. The method for preparing an iron-containing solution by direct extraction and purification according to claim 1, characterized in that, In step (1), the molar ratio of iron ions to complexing stabilizer in the hydrochloric acid leaching iron solution is 100:(0.1-0.5); Preferably, the complexing stabilizer in step (1) includes sodium citrate; Preferably, in the hydrochloric acid leaching solution for iron in step (1), the concentration of iron ions is 100g / L-140g / L, the concentration of hydrogen ions is 1.2mol / L-1.8mol / L, the concentration of cobalt ions is 40mg / L-50mg / L, the concentration of manganese ions is 260mg / L-300mg / L, the concentration of aluminum ions is 3g / L-4g / L, the concentration of chromium ions is 2g / L-3g / L, the concentration of nickel ions is 60mg / L-80mg / L, and the total concentration of sodium ions, calcium ions and magnesium ions is 25mg / L-35mg / L.

3. The method for preparing an iron-containing solution by direct extraction and purification according to claim 1 or 2, characterized in that, In step (1), the hydrochloric acid leaching iron solution is first mixed with a reducing agent to reduce hexavalent chromium to trivalent chromium, then mixed with a complexing stabilizer, and then filtered to obtain a pretreated solution. Preferably, when the hydrochloric acid leaching iron solution in step (1) is first mixed with the reducing agent, the amount of the reducing agent added to the hydrochloric acid leaching iron solution is 2g / L-3g / L; Preferably, the reducing agent comprises ferrous chloride.

4. The method for preparing an iron-containing solution by direct extraction and purification according to claim 1 or 2, characterized in that, The organic phase of the compound in step (2) includes 0.1 mol / L-0.5 mol / L of quaternary ammonium chloride, 3 wt%-8 wt% of organic acid, 0.05 mol / L-0.1 mol / L of phosphate ester compound, 10 wt%-15 wt% of polyol and the balance being diluent; Preferably, the quaternary ammonium chloride in step (2) includes any one or a combination of at least two of dodecyltrimethylammonium chloride, dodecyldimethylbenzylammonium chloride, or tetramethylammonium chloride; Preferably, the organic acid in step (2) includes acetic acid or citric acid; Preferably, the phosphate ester compound in step (2) includes tributyl phosphate; Preferably, the polyol in step (2) includes 2-octanol; Preferably, the diluent comprises sulfonated kerosene.

5. The method for preparing an iron-containing solution by direct extraction and purification according to claim 1 or 2, characterized in that, The extraction method described in step (2) is 5-10 stage countercurrent extraction; Preferably, the O / A ratio of the extraction in step (2) is 1:(1-3); Preferably, the extraction temperature in step (2) is 25℃-35℃ and the equilibrium pH is 0.18-1.

0.

6. The method for preparing an iron-containing solution by direct extraction and purification according to claim 1 or 2, characterized in that, The washing solution used in step (3) includes a hydrochloric acid solution containing ammonium chloride; Preferably, the concentration of ammonium chloride in the washing solution is 0.02 mol / L to 0.04 mol / L; Preferably, the pH of the washing solution is 1.5-2.0; Preferably, the washing method in step (3) includes countercurrent washing.

7. The method for preparing an iron-containing solution by direct extraction and purification according to claim 1 or 2, characterized in that, Step (4) The first back-extraction uses pure water as the back-extraction agent; Preferably, in step (4), the first back-extraction yields a cobalt-manganese recovery solution; Preferably, in step (4), the second back-extraction stage has 5 to 10 stages; Preferably, in step (4) the second back-extraction process, the back-extraction agent used in the first to third stages is a chloride salt solution with a concentration of 0.01 mol / L to 0.03 mol / L. In the subsequent stages, the concentration of the chloride salt solution used is gradually reduced from 0.01 mol / L to 0.03 mol / L until the solution is pure water.

8. The method for preparing an iron-containing solution by direct extraction and purification according to claim 1 or 2, characterized in that, In step (4), the temperatures of the first and second back-extractions are independently 25°C-35°C, with an O / A ratio of 1:(1-3). Preferably, in step (4), the stirring speed of the first back-extraction and the second back-extraction are independently 200 r / min-300 r / min, and the time of single-stage back-extraction is independently 20 min-25 min.

9. The method for preparing an iron-containing solution by direct extraction and purification according to claim 1 or 2, characterized in that, After obtaining the iron-containing solution in step (4), a sulfate removal step and a purification step were also performed. Preferably, the sulfate removal step includes the following steps: After heating the iron-containing solution obtained in step (4), add barium salt solution to react, and then allow it to stand and filter. Preferably, the temperature is raised to 40℃-50℃; Preferably, based on the barium ions in the barium salt solution, the amount of barium salt solution added is 1.05 to 1.1 times the molar equivalent of sulfate ions; Preferably, the stirring rate of the reaction is 200 r / min-300 r / min, and the time is 20 min-30 min.

10. The method for preparing an iron-containing solution by direct extraction and purification according to claim 9, characterized in that, The purification step includes precision filtration of the solution obtained from the sulfate removal step; Preferably, the filter cloth used in the precision filtration has a pore size of 0.45μm-1.0μm.

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