Method for purifying sulfuric acid
The use of acidic organic phosphorus compounds in a multi-step process addresses the high cost issue of sulfuric acid purification, achieving efficient and cost-effective purification of sulfuric acid.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- ASAKA RIKEN
- Filing Date
- 2025-10-21
- Publication Date
- 2026-05-12
AI Technical Summary
Existing methods for purifying sulfuric acid using a monodisperse chelating exchanger are costly due to the high expense of the exchanger, leading to high purification costs.
A method involving an extraction step with an acidic organic phosphorus compound, such as 2-ethylhexyl 2-ethylhexylphosphonate or bis(2,4,4-trimethylpentyl)dithiophosphinic acid, followed by a back-extraction, oxidation, and dilution steps, to purify sulfuric acid at a lower cost.
The method effectively reduces the cost of sulfuric acid purification by achieving high iron extraction rates and efficient purification, making it practical for industrial use.
Smart Images
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Abstract
Description
Technical Field
[0001] The present invention relates to a method for purifying sulfuric acid.
Background Art
[0002] Impurities such as iron are contained in industrial sulfuric acid. Therefore, methods for purifying industrial sulfuric acid have been studied. Patent Document 1 discloses a method for purifying sulfuric acid in which sulfuric acid containing metals such as iron is purified by using a monodisperse chelating exchanger.
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0004] The monodisperse chelating exchanger is very expensive, and the cost of the purification method was high.
[0005] The problem to be solved by the present invention is to provide a method for purifying sulfuric acid at a low cost.
Means for Solving the Problems
[0006] In view of the above problems, the present inventors have conducted extensive studies and found that the cost of a method for purifying sulfuric acid including an extraction step of extracting iron from sulfuric acid using a specific acidic organic phosphorus compound is low. The present invention has been completed based on these findings.
[0007] The present invention relates to a method for purifying sulfuric acid, comprising an extraction step of extracting iron from sulfuric acid using an acidic organophosphorus compound, wherein the acidic organic extractant comprises at least one selected from the group consisting of 2-ethylhexyl 2-ethylhexylphosphonate and bis(2,4,4-trimethylpentyl)dithiophosphinic acid. The method for purifying sulfuric acid preferably further includes a back-extraction step in which the extract obtained through the extraction step is back-extracted to obtain a back-extract containing iron. The method for purifying sulfuric acid preferably further includes a dilution step in which concentrated sulfuric acid is diluted with water. The method for purifying sulfuric acid preferably further includes an oxidation step in which sulfuric acid is oxidized with an oxidizing agent. [Effects of the Invention]
[0008] The present invention provides a method for purifying sulfuric acid at a low cost. [Brief explanation of the drawing]
[0009] [Figure 1] An explanatory diagram showing the configuration of one embodiment of the sulfuric acid purification method of the present invention. [Modes for carrying out the invention]
[0010] The present invention will be described in more detail.
[0011] The present invention provides a method for purifying sulfuric acid, comprising an extraction step (STEP 2 in Figure 1) in which iron is extracted from sulfuric acid 1 using an acidic organophosphorus compound 4. The acidic organophosphorus compound 4 comprises at least one selected from the group consisting of 2-ethylhexyl 2-ethylhexylphosphonate and bis(2,4,4-trimethylpentyl)dithiophosphinic acid. Purified sulfuric acid 5 is obtained through the extraction step.
[0012] The acidic organophosphorus compound 4 may be diluted with a diluent, and the concentration of the acidic organophosphorus compound 4 may be adjusted as appropriate. Examples of the diluent include hydrocarbons such as kerosene and decane, and Class III petroleum products. A typical example of Class III petroleum products is MC531 manufactured by Tobu Chemical Co., Ltd. The concentration of the acidic organophosphorus compound 4 in the organic solvent consisting of the acidic organophosphorus compound and the diluent is preferably in the range of 10 to 40% by mass.
[0013] The sulfuric acid 1 may be concentrated sulfuric acid. The method for purifying sulfuric acid of the present invention may include an oxidation step (STEP 1 in Figure 1) in which the iron contained in the sulfuric acid 1 is oxidized by the oxidizing agent 2. The oxidizing agent 2 preferably contains at least one selected from the group consisting of hydrogen peroxide, potassium permanganate, and sodium hypochlorite, and more preferably at least one selected from the group consisting of hydrogen peroxide, potassium permanganate, and sodium hypochlorite.
[0014] The present invention's method for purifying sulfuric acid may include a dilution step (STEP 1 in Figure 1) in which the sulfuric acid 1 is diluted with water 3. The order of the oxidation step and the dilution step may be set as appropriate. The dilution step may be performed after the oxidation step, or the oxidation step may be performed after the dilution step, or the oxidation step and the dilution step may be performed simultaneously. Furthermore, the oxidation step and the dilution step may be performed multiple times in any order.
[0015] The present invention's method for purifying sulfuric acid may include a back-extraction step (STEP 3 in Figure 1) in which the extract obtained through the extraction step is back-extracted to obtain a back-extract 6 containing iron. The extract and an acid are mixed in the back-extraction step. The acid preferably comprises at least one selected from the group consisting of mineral acids, organic acids, and chelating acids, and more preferably at least one selected from the group consisting of mineral acids, organic acids, and chelating acids. The mineral acid preferably comprises at least one selected from the group consisting of hydrochloric acid, sulfuric acid, and nitric acid, more preferably hydrochloric acid, and even more preferably hydrochloric acid. The organic acid is preferably oxalic acid, and more preferably oxalic acid. When oxalic acid is used, iron is back-extracted at a lower concentration than with mineral acid, so the amount of acid used can be reduced, which reduces costs and simplifies equipment design, making it highly practical for industrial use.
[0016] The present invention's method for purifying sulfuric acid may include a reduction step in which a reducing agent is mixed with the purified sulfuric acid 5 and the purified sulfuric acid 5 is reduced. In the oxidation step, the oxidation-reduction potential of the sulfuric acid 1 increases, but in the reduction step, the oxidation-reduction potential of the purified sulfuric acid 5 decreases. The reducing agent preferably comprises at least one selected from the group consisting of oxalic acid, formic acid, and sulfites, and more preferably at least one selected from the group consisting of oxalic acid, formic acid, and sulfites. [Examples]
[0017] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.
[0018] In the examples and comparative examples, the iron concentration was measured using an inductively coupled plasma atomic emission spectrometer (ICP-OES).
[0019] Example 1 50 L of 3M sulfuric acid and 50 L of 1M 2-ethylhexyl 2-ethylhexylphosphonate (PC-88A manufactured by Daihachi Chemical Industry Co., Ltd.) as an acidic organic extractant were mixed, and iron in the sulfuric acid was extracted (extraction step). The obtained extract was back-extracted with 5 L of 0.5M oxalic acid (back-extraction step). Table 1 shows the iron concentrations in the aqueous phase before extraction and the aqueous phase after extraction in the extraction step, and the iron concentrations in the oil phase after back-extraction and the aqueous phase after back-extraction in the back-extraction step.
[0020] Example 2 The same operations as in Example 1 were carried out except that 1M bis(2,4,4-trimethylpentyl) dithiophosphinic acid (Cyanex 301 manufactured by Syensqo) was used as the acidic organic extractant. The results are shown in Table 1.
[0021] Example 3 The same operations as in Example 1 were carried out except that 5 L of 3M hydrochloric acid was used in the back-extraction step. The results are shown in Table 1.
[0022] Comparative Example 1 The same operations as in Example 1 were carried out except that 1M (2,4,4-trimethylpentyl) phosphinic acid (Cyanex 272 manufactured by Syensqo) was used as the acidic organic extractant. The results are shown in Table 1.
[0023] [Table 1]
[0024] The iron extraction rate in the extraction step of Comparative Example 1 where no predetermined compound was used as the acidic organic extractant was low. On the other hand, the iron extraction rates in the extraction steps of Examples 1 to 3 where a predetermined compound was used as the acidic organic extractant were high. [Explanation of Reference Signs]
[0025] 1... sulfuric acid, 2... oxidizing agent, 3... water, 4... acidic organic phosphorus compound, 5... purified sulfuric acid, 6... back-extractant containing iron.
Claims
1. A method for purifying sulfuric acid, The extraction step involves extracting iron from sulfuric acid using an acidic organophosphorus compound. A method for purifying sulfuric acid, wherein the acidic organic extractant comprises at least one selected from the group consisting of 2-ethylhexyl 2-ethylhexyl phosphonate and bis(2,4,4-trimethylpentyl)dithiophosphinic acid.
2. A method for purifying sulfuric acid according to claim 1, further comprising a back-extraction step of back-extracting the extract obtained through the extraction step to obtain a back-extract containing iron.
3. A method for purifying sulfuric acid according to claim 1, further comprising a dilution step in which concentrated sulfuric acid is diluted with water.
4. A method for purifying sulfuric acid according to any one of claims 1 to 3, further comprising an oxidation step in which sulfuric acid is oxidized with an oxidizing agent.