A method for purifying high-concentration iron ions in hydrochloric acid solution

Abstract

The present invention relates to a method for purifying high-concentration iron ions in a hydrochloric acid solution. The method comprises the following steps: subjecting the hydrochloric acid solution containing the high-concentration iron ions to multi-stage extraction using an extractant, wherein the extractant is a mixture containing trioctyl phosphate; removing impurities in an iron-rich organic phase using a pickling agent to obtain a pickled organic phase; subjecting the pickled iron-rich organic phase to multi-stage stripping; and regenerating the solution after the multi-stage stripping. The method adopts a new extraction system (a mixture containing trioctyl phosphate phase) to reduce the acidity or chloride ion concentration required during extraction, thereby meeting the requirements for the hydrochloric acid solution extraction process for high-concentration iron, and making the stripping process of the iron in the loaded organic phase easier to perform. The stripping solution does not introduce new impurities, thereby achieving selective extraction of iron ions and reducing the cost of purifying, extracting, or concentrating the iron in the hydrochloric acid solution.

Description

Technical Field

[0001] The invention belongs to the technical field of iron ion extraction, and in particular relates to a method for purifying high-concentration iron ions in a hydrochloric acid solution. Background Art

[0002] In the prior art, common methods for recovering iron from hydrochloric acid solutions include precipitation and extraction. Precipitation methods include the potassium iron vanadium method, the goethite method, and the hematite method. It is usually required to be carried out under low acidity conditions; in addition, there are many impurities and the purity of the iron precipitate is low. The extraction method for recovering iron has the advantages of high selectivity, low energy consumption, and less pollution. 3+ The commonly used extraction agent for recovery is N235. The operating conditions generally require that the chloride ion concentration in the aqueous phase is greater than 2 mol / L, Fe 3+ Concentration ≤ 30g / L. To improve extraction performance, the N235 organic system usually needs to be acidified before extraction. Dilute hydrochloric acid or pure water is generally used for back extraction, but it is usually difficult to achieve 100% back extraction.

[0003] Organic TBP can be used to recover iron from hydrochloric acid solutions, and stripping is relatively easy. However, TBP extraction and purification of iron from hydrochloric acid solutions requires high hydrochloric acid or chloride ion concentrations, increasing purification costs and generating large amounts of NaCl waste salt. N235 is only suitable for low-concentration iron ion solutions in hydrochloric acid solutions. To address the difficulty in stripping iron from N235, studies have shown that diammonium hydrogen phosphate can achieve better stripping results. In addition to increasing purification costs, diammonium hydrogen phosphate can easily introduce new impurities such as phosphorus into the iron product. Furthermore, it produces phosphorus-containing wastewater, impacting the ecological environment. N5O3 extractants are effective for extracting low-concentration iron from hydrochloric acid solutions. Commercially available N5O3 has a low purity, typically approximately 80% active ingredient. However, at high iron ion concentrations (>30 g / L), emulsification is likely to occur during extraction, and stripping is also difficult.

[0004] The main disadvantages of existing iron recovery technology in hydrochloric acid are: (1) The existing method is only applicable to hydrochloric acid solutions with low iron concentration (iron ion concentration ≤ 30 g / L), and is not applicable to hydrochloric acid solutions with high iron concentration. (2) Organic stripping after iron loading is extremely difficult. Generally, after multiple cross-current stripping (> 3 times), there are still a lot of iron ions in the organic solution that are difficult to strip. (3) Organic iron extraction generally needs to be carried out under high hydrochloric acid or chloride ion conditions (chloride ion concentration ≥ 4 mol / L). (4) In order to improve the stripping effect of iron in N235 or N5O3 organic, oxalic acid, diammonium hydrogen phosphate and other reagents are used during stripping, which will increase the cost of iron ion purification and produce other difficult-to-treat wastewater. (5) The existing extraction system has poor selectivity and severely extracts impurity ions such as Al, Si, Mg, and Ca, affecting the purity of the final product. Summary of the Invention

[0005] In view of the above problems, the present invention provides a method for purifying high-concentration iron ions in hydrochloric acid solution.

[0006] The technical solution adopted in the present invention is as follows:

[0007] A method for purifying high-concentration iron ions in a hydrochloric acid solution, the method comprising the following steps:

[0008] The hydrochloric acid solution containing high concentration of iron ions is subjected to multi-stage extraction using an extractant, wherein the extractant is a mixture containing trioctyl phosphate;

[0009] removing impurities in the iron-rich organic phase with an acid washing agent to obtain an acid washed organic phase;

[0010] The iron-rich organic phase after pickling is subjected to multi-stage stripping;

[0011] The solution after multi-stage stripping is regenerated.

[0012] Furthermore, the mixture of trioctyl phosphate includes one or two of tributyl phosphate, dimethylheptyl methyl phosphate, trialkylphosphine oxide, N,N-dimethylheptyl acetamide, isodecyl alcohol, n-octanol, isooctyl alcohol, n-butanol or 2-butanol.

[0013] Furthermore, the three substances in the extractant are respectively denoted as A, B, and C, where A represents trioctyl phosphate, B represents any one of tributyl phosphate, dimethylheptyl methylphosphate, trialkylphosphine oxide, and N,N-dimethylheptyl acetamide; and C represents any one of isodecyl alcohol, n-octanol, isooctyl alcohol, n-butanol, and 2-butanol; and the volume ratio of A, B, and C is 0~90:0~90:0~20.

[0014] Furthermore, the volume ratio of A, B, and C is 20~60:20~60:0~10.

[0015] Furthermore, the extraction conditions are as follows: single-stage extraction time is 2 to 20 min; extraction temperature is 10 to 80 °C; flow ratio of organic phase to aqueous phase is 3:1 to 1:10;

[0016] The acid washing conditions are as follows: single-stage washing time 2-20 min; washing temperature 10-80 °C; flow ratio of organic phase to aqueous phase 1:1-10:1;

[0017] The stripping conditions are as follows: single-stage stripping time is 2 to 20 min; stripping temperature is 10 to 80 °C; the flow ratio of the organic phase to the aqueous phase is 1:1 to 10:1;

[0018] The regeneration conditions are as follows: regeneration time 2~20 min; regeneration temperature 10~80 ℃; flow ratio of organic phase to aqueous phase 1:1~10:1.

[0019] Furthermore, the extraction temperature is 20~40°C; the stripping temperature is 20~40°C; and the regeneration temperature is 20~40°C.

[0020] Furthermore, the number of extraction stages is 2 to 20; the number of back extraction stages is 1 to 20; and the number of regeneration stages is 1 to 2.

[0021] Furthermore, the number of extraction stages is 3 to 10; and the number of back extraction stages is 2 to 10.

[0022] Furthermore, the iron ion concentration in the hydrochloric acid solution is 0-120 g / L; and the hydrochloric acid or chloride ion concentration is 0.2-12 mol / L.

[0023] Furthermore, during the extraction process, the aqueous phase is a hydrochloric acid solution containing a high concentration of iron ions, and the concentration of the hydrochloric acid solution or chloride ions is 0.5~4 mol / L; during the pickling process, the pickling agent is hydrochloric acid with a concentration of 0.2~4 mol / L; during the stripping process, the stripping agent is pure water or a low-concentration hydrochloric acid solution, and the hydrochloric acid concentration is not greater than 0.01 mol / L; during the regeneration process, the regeneration agent is one or two of hydrochloric acid, sodium chloride, potassium chloride, and calcium chloride, and the regeneration agent concentration is 0.01~10 mol / L.

[0024] This method utilizes a novel extraction system (a mixture containing trioctyl phosphate) to reduce the required acidity or chloride ion concentration during extraction, enabling the extraction of high-concentration iron with hydrochloric acid. This method also facilitates the stripping of iron from organic materials without introducing new impurities into the stripping solution, achieving selective extraction of iron ions and reducing the cost of hydrochloric acid purification, extraction, or concentration. Furthermore, trioctyl phosphate in the extraction system is less expensive than dimethylheptyl methylphosphate and trialkylphosphine oxide, making it easier to scale up and apply in engineering applications.

[0025] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the description and claims. DETAILED DESCRIPTION

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0027] The high-concentration iron ion hydrochloric acid solution (2 mol / L) used in the examples of this invention was selected from an iron ore. The specific composition analysis results are shown in Table 1. It contains impurities such as Al, SiO2, Ca, Mg, Na, K, Cu, and Ni. The iron ion concentration of the solution reached a high of 103.9 g / L. The test solution was first filtered to remove fine solid particles, and then a purification test was performed.

[0028] Table 1 Chemical composition analysis of hydrochloric acid leaching solution of an iron ore

[0029]

[0030] Example 1

[0031] A hydrochloric acid solution containing the high iron ion concentration (103.9 g / L) was subjected to a four-stage extraction using 45% trioctyl phosphate, 45% tributyl phosphate, and 10% n-octanol (all by volume). The extraction time for each stage was 5 minutes, and the extraction temperature was 30°C. The organic phase and aqueous phase had an O / A ratio of 2:1. Four washes were performed using 2 mol / L hydrochloric acid at an O / A ratio of 4:1. After loading the organic phase, four stripping steps were performed using 0.01 mol / L hydrochloric acid at an O / A ratio of 2:1. Each stripping step lasted 5 minutes, and the temperature was 30°C, resulting in a 100% iron stripping efficiency. Organic scrubbing regeneration was performed using 5 g / L NaCl solution at an O / A ratio of 4:1, followed by three countercurrent washes.

[0032] Example 2

[0033] The hydrochloric acid solution containing the high iron ion concentration (same as in Example 1) was subjected to six-stage extraction using 60% trioctyl phosphate and 40% tributyl phosphate (both by volume). The single-stage extraction lasted 5 minutes, the extraction temperature was 30°C, and the O / A ratio of the organic phase to the aqueous phase was 2:1. After six stages of extraction, the iron ion extraction rate in the solution was 100%, while the extraction rates of other metal impurities and silicon ions were 0%. This was followed by four stages of stripping using pure water. The single-stage stripping lasted 5 minutes, the stripping temperature was 70°C, and the O / A ratio of the organic phase to the aqueous phase was 1.5:1, resulting in a 100% iron stripping rate. Both extraction and stripping effects were excellent.

[0034] Example 3

[0035] The hydrochloric acid solution containing the high iron ion concentration (same as in Example 1) was subjected to six-stage extraction using 50% trioctyl phosphate and 50% dimethylheptyl methylphosphate (both by volume). The extraction time for each stage was 5 minutes, the extraction temperature was 30°C, and the extraction conditions were an O / A ratio of 2:1. After six stages of countercurrent extraction, the iron ion extraction rate in the solution was 100%. This was followed by four stages of stripping using pure water at 50°C for a total stripping time of 20 minutes. The O / A ratio of the organic phase to the aqueous phase was 1.8:1. After four stages of countercurrent stripping, the iron stripping rate was 100%. Both extraction and stripping effects were good.

[0036] Example 4

[0037] A four-stage extraction was performed using a 2 mol / L hydrochloric acid solution (same as in Example 1) diluted 1-fold with the iron ore hydrochloric acid leachate. The extractants were 50% trioctyl phosphate, 40% N503, and 10% isooctanol (all by volume). The extraction conditions were an O / A ratio of 2:1, a single-stage extraction time of 5 minutes, and an extraction temperature of 30°C. After four stages of countercurrent extraction, the iron ion extraction rate was 100%. This was followed by five stages of stripping using pure water at a stripping temperature of 40°C for a total stripping time of 30 minutes. During the stripping process, the O / A ratio of the organic phase to the aqueous phase was 2:1. After the five stages of countercurrent stripping, the iron stripping rate was 100%.

[0038] Example 5

[0039] The hydrochloric acid solution containing the high iron ion concentration (same as in Example 1) was subjected to six-stage extraction using 45% trialkylphosphine oxide, 45% dimethylheptyl methylphosphate, and 10% isodecyl alcohol (all by volume). The extraction conditions were an O / A ratio of 2:1, a single-stage extraction time of 4 minutes, and an extraction temperature of 40°C. After six stages of countercurrent extraction, the iron ion extraction rate in the solution was 100%. This was followed by four stages of stripping using 0.005 mol / L hydrochloric acid solution at 50°C for a total stripping time of 24 minutes. The O / A ratio of the organic phase to the aqueous phase during the stripping process was 1.8:1. After four stages of countercurrent stripping, the iron stripping rate was 99.1%. Both extraction and stripping effects were excellent.

[0040] Comparative Example 1

[0041] A four-stage extraction was performed using a 2 mol / L hydrochloric acid solution (same as in Example 1) diluted 1-fold from the iron ore hydrochloric acid leachate. The extractants were 30% N,N-dimethylheptyl acetamide (N5O3) and 70% sulfonated kerosene (both by volume). The extraction conditions were an O / A ratio of 2:1, a single-stage extraction time of 10 minutes, and an extraction temperature of 30°C. The iron ion extraction yield was 95%. This was followed by a three-stage stripping process using pure water at a temperature of 40°C for a total stripping time of 20 minutes. The O / A ratio of the organic phase to the aqueous phase was 1.5:1. After the three-stage cross-current stripping, the N5O3 organic system still had a dark yellow color and contained a high concentration of iron ions. The iron stripping yield was 80%, indicating poor stripping results.

[0042] Comparative Example 2

[0043] The hydrochloric acid solution containing the above-mentioned high concentration of iron ions (same as in Example 1) was subjected to six-stage extraction. The extractants were 40% tributyl phosphate and 60% sulfonated kerosene (both by volume). Hydrochloric acid was used to adjust the chloride ion concentration of the aqueous phase to 5 mol / L. The extraction conditions were an O / A ratio of 3:1, a single-stage extraction time of 10 minutes, and an extraction temperature of 30°C. After six stages of countercurrent extraction, the iron ion extraction rate in the solution was 82%. It then underwent six stages of stripping, using pure water for stripping, a stripping temperature of 45°C, a stripping time of 30 minutes, and an O / A ratio of 2:1 between the organic phase and the aqueous phase during the stripping process. After six stages of countercurrent stripping, the iron stripping rate was 100%. The stripping effect was good, but the extraction required higher acidity or chloride ion concentration.

[0044] Analysis of the results of the above examples shows that, compared with the existing extraction system (Comparative Example 1), iron is more difficult to strip after extraction; the use of trioctyl phosphate in the extraction systems of Examples 1-4 can greatly improve the stripping efficiency of iron in organic matter, especially the extraction of iron from ferric hydrochloric acid solution.

[0045] The addition of trioctyl phosphate to the extraction system in Examples 1-4 significantly improved the iron ion extraction rate compared to the extraction system in Comparative Example 2 (a mixture of tributyl phosphate and sulfonated kerosene), allowing for easier stripping of the iron after extraction. However, when tributyl phosphate is used in the extraction system, its iron extraction capacity is limited. To improve tributyl phosphate's ability to extract iron ions, extraction must be performed at a higher hydrochloric acid concentration. Substituting trioctyl phosphate for part of the tributyl phosphate can reduce the higher hydrochloric acid concentration required when extracting iron using tributyl phosphate alone, while also improving the extraction capacity of the extraction system.

[0046] Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for purifying high-concentration iron ions in a hydrochloric acid solution, the method comprising the steps of: The hydrochloric acid solution containing high concentration of iron ions is subjected to multi-stage extraction using an extractant, wherein the extractant is a mixture containing trioctyl phosphate; removing impurities in the iron-rich organic phase with an acid washing agent to obtain an acid washed organic phase; The acid-washed organic phase is subjected to multi-stage stripping; Regenerating the solution after multi-stage stripping; in, During the extraction process, the aqueous phase is a hydrochloric acid solution containing a high concentration of iron ions, and the iron ion concentration in the hydrochloric acid solution is 103.9g / L-120g / L; the hydrochloric acid or chloride ion concentration is 0.5~4 mol / L; the pickling agent during the pickling process is hydrochloric acid with a concentration of 0.2~4 mol / L; the stripping agent during the stripping process is pure water or a low-concentration hydrochloric acid solution, and the hydrochloric acid concentration is not greater than 0.01 mol / L; the regeneration agent during the regeneration process is one or two of hydrochloric acid, sodium chloride, potassium chloride, and calcium chloride, and the regeneration agent concentration is 0.01~10 mol / L.

2. The method according to claim 1, wherein The mixture containing trioctyl phosphate includes one or two of tributyl phosphate, dimethylheptyl methylphosphate, trialkylphosphine oxide, N,N-dimethylheptyl acetamide, isodecyl alcohol, n-octanol, isooctyl alcohol, n-butanol or 2-butanol.

3. The method according to claim 2, wherein: The three substances in the extractant are denoted as A, B, and C, respectively, where A represents trioctyl phosphate, B represents any one of tributyl phosphate, dimethylheptyl methylphosphate, trialkylphosphine oxide, and N,N-dimethylheptyl acetamide; and C represents any one of isodecyl alcohol, n-octanol, isooctyl alcohol, n-butanol, and 2-butanol; wherein the volume ratio of A, B, and C is 20-60:20-60:0-10.

4. The method according to claim 1, wherein The extraction conditions are as follows: single-stage extraction time of 2 to 20 min; extraction temperature of 10 to 80 °C; flow ratio of organic phase to aqueous phase of 3:1 to 1:10; The acid washing conditions are as follows: single-stage washing time 2-20 min; washing temperature 10-80 °C; flow ratio of organic phase to aqueous phase 1:1-10:1; The stripping conditions are as follows: single-stage stripping time is 2 to 20 min; stripping temperature is 10 to 80 °C; the flow ratio of the organic phase to the aqueous phase is 1:1 to 10:1; The regeneration conditions are as follows: regeneration time 2~20 min; regeneration temperature 10~80 ℃; flow ratio of organic phase to aqueous phase 1:1~10:

1.

5. The method according to claim 4, wherein The extraction temperature is 20~40 ℃; the stripping temperature is 20~40 ℃; and the regeneration temperature is 20~40 ℃.

6. The method according to claim 1, wherein The number of extraction stages is 2 to 20; the number of back extraction stages is 2 to 10; and the number of regeneration stages is 1 to 2.

7. The method according to claim 6, wherein: The extraction stages are 3 to 10.

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