A novel phosphoric acid purifier and preparation method thereof

Abstract

The invention discloses a novel phosphoric acid purifier and a preparation method thereof. The novel phosphoric acid purifier comprises the following mass percentages of hydrosulfate 34-40.0%, sodium carbonate 21-24%, sulfate 3%, sulfur dioxide about 1%, and the balance water. A method for preparing a novel phosphoric acid purifier comprises the following steps: step 1: adding a measured amount of sodium thiosulfate to a reactor, heating and dissolving it; step 2: adding a measured amount of catalyst and an organic flocculant to prepare it under a temperature of 60°C-80°C. Sodium thiosulfate is used to replace sodium sulfide, sodium thiosulfate is used as a basic raw material, sodium thiosulfate is modified, and a suitable catalyst is added to increase the decomposition rate of S2-, so as to reduce the arsenic ions in a high arsenic-containing phosphoric acid solution from 60ppm to below 0.5ppm, thereby achieving the purpose of phosphoric acid dearsenicization.

Description

Technical Field

[0001] The invention belongs to the technical field of phosphoric acid purification, and in particular relates to a novel phosphoric acid purifier and a preparation method thereof. Background Art

[0002] At present, the most common arsenic removal method in the research on arsenic removal from wet phosphoric acid is mainly chemical precipitation, that is, sodium sulfide is decomposed into hydrogen sulfide when it meets acid, and hydrogen sulfide then reacts with trivalent arsenic to generate As2S3 precipitation. The process is simple and the cost is low, but in the actual reaction process, sodium sulfide decomposes rapidly when it meets acid, and the generated hydrogen sulfide cannot react quickly and completely with the arsenic compounds in phosphoric acid, which easily leads to material overflow and environmental pollution. Arsenic generally exists in phosphoric acid in the form of arsenic acid or arsenous acid. Sulfide is used as a arsenic removal agent, and S2- reacts with As to generate insoluble compounds, thereby removing the arsenic contained in phosphoric acid. This method is effective for the removal of low-mass fraction arsenic, but it does not have a good response for the removal of high-mass fraction arsenic. It can be seen that the current common wet phosphoric acid arsenic removal technology can no longer meet the requirements of enterprise wastewater treatment, and research in the field of wet phosphoric acid arsenic removal technology is urgent.

[0003] Sulfide is the compound that reacts most directly and quickly with arsenic. However, the decomposition of Na2S into H2S under acidic conditions is an instantaneous reaction, but the reaction time of hydrogen sulfide with arsenic is much slower than the decomposition time of Na2S. The H2S produced in this way cannot react with As3+ in time, and the excess H2S will overflow. H2S is a highly toxic compound. Once it is excessive in the air, it will cause human poisoning.

[0004] In summary, in order to solve the above technical problems existing in the prior art, the present invention provides a product for removing arsenic from a high-arsenic-containing, acidic solution, namely, a phosphoric acid purifier. Summary of the invention

[0005] In order to solve the above problems, the present invention aims to provide a novel phosphoric acid purifier and a preparation method thereof.

[0006] In order to achieve the above object, the present invention adopts the following technical scheme: a new type of phosphoric acid purifier, including 34-40.0% hydrosulfate, 21-24% sodium carbonate, 3% sulfate, about 1% sulfur dioxide, and the rest is water.

[0007] A method for preparing a novel phosphoric acid scavenger comprises the following steps:

[0008] Step 1: Add measured sodium thiosulfate into a reactor, heat and dissolve it;

[0009] Step 2: At a temperature of 60°C-80°C, add a measured amount of catalyst and an organic flocculant to prepare the product.

[0010] Furthermore, the prepared phosphoric acid purifier is a yellow-green transparent liquid.

[0011] Further, the following weight percentages are measured: 50%-60% sodium thiosulfate, 5%-8% catalyst, 2%-3% organic flocculant and 35%-43% water.

[0012] Furthermore, the obtained phosphoric acid purifier has an effective matter content of ≥13% calculated as H2S.

[0013] Furthermore, the fluoride content of the obtained phosphoric acid purifier calculated as F- is ≤0.001%.

[0014] Furthermore, the obtained phosphoric acid purifier contains heavy metals calculated as Pb≤0.0005%.

[0015] Furthermore, the obtained phosphoric acid purifier has an oxidizable substance of 0.012% or less based on PO3.

[0016] Furthermore, the pH of the obtained phosphoric acid purifier is 10.0-12.0.

[0017] Furthermore, the obtained phosphoric acid purifier has a density of 1.2-1.3 g / cm2 at 20°C.

[0018] Compared with the prior art, the present invention has the following advantages: sodium thiosulfate is used to replace sodium sulfide, sodium thiosulfate is used as the basic raw material, sodium thiosulfate is modified, and a suitable catalyst is added to increase the decomposition rate of S2-, so as to reduce the arsenic ions in the high-arsenic-containing phosphoric acid solution from 60 ppm to below 0.5 ppm, thereby achieving the purpose of dearsenicating phosphoric acid. DETAILED DESCRIPTION

[0019] The present invention is further described below in conjunction with specific embodiments, but it should not be understood that the scope of the subject matter described in the present invention is limited to the following embodiments. Without departing from the above-mentioned technical ideas of the present invention, various modifications, substitutions and changes made according to common technical knowledge and customary means in the field are included in the scope of the present invention.

[0020] The novel phosphoric acid purifier of the present invention is added with a sulfide stabilizer, thereby retaining the advantages of hydrogen sulfide dearsenication and solving the disadvantage of rapid decomposition of sodium sulfide. The product slows down the decomposition speed of H2S by the dearsenication agent in phosphoric acid dearsenication, and can quantitatively control the decomposition amount of H2S according to the arsenic ion content in phosphoric acid, thereby controlling or reducing H2S overflow and environmental pollution.

[0021] The arsenic removal agent adds a small amount of organic flocculant, which accelerates the sedimentation rate and completeness of the formed As2S3. When a slightly excessive amount of arsenic removal agent is added, the phosphoric acid containing 50ppm arsenic can be reduced to less than 0.5ppm arsenic.

[0022] Among them, the decomposed S2- can not only react with arsenic ions: 2As3++3S2-=2As2S3↓, but also react with H+: S2-+2H+=H2S↑. Therefore, the amount of catalyst used can control the overflow of a large amount of hydrogen sulfide gas to ensure product quality and production safety, more effectively treat the arsenic index in clear phosphoric acid, enhance the application effect of arsenic removal process, reduce arsenic removal cost, and verify the laboratory effect of process adjustment.

[0023] Replace sodium sulfide with sodium thiosulfate. Thiosulfuric acid (H2S2O3 or H2SO3S) is an inorganic substance, which is the product of replacing one oxygen atom in sulfuric acid (H2SO4) with a sulfur atom. The average oxidation number of the two sulfur atoms is +2. One of the sulfur atoms has an oxidation number of +6, and the other has an oxidation number of -2. Therefore, thiosulfuric acid and its salts have certain reducing and oxidizing properties.

[0024] Arsenic removal principle: The ion equation for the reaction between sodium thiosulfate and phosphoric acid is:

[0025] Na2S2O3+H3PO4=Na2HPO4+S203 2-+H2↑.

[0026] S2O32-+H2O=(cat)S2-+2H++SO42-,

[0027] 2As3++3S2-=2As2S3↓

[0028] 2As2O3+3S2O32-+6H+=(cat)As2S3↓+3SO42-+3H2O

[0029] However, thiosulfate (S203 2-) has low activity and needs to be added with a catalyst to improve its activity. Through many experiments, we found a suitable catalyst (modifier), including but not limited to ferrous sulfide, and synthesized a new arsenic removal agent.

[0030] Example 1: The preparation steps of the novel phosphoric acid purifier are as follows: 500 kg of sodium thiosulfate pentahydrate is added to a reactor, 430 kg of water is added, and the mixture is heated to dissolve. At a temperature of 60°C-80°C, 50 kg of a catalyst (homemade) is added to decompose the thiosulfate ion, and the S in the material is sampled and tested at any time. 2-When the content reaches the requirement, 20kg flocculant is added, and the purifier obtained is a yellow-green transparent liquid with no sediment. The main components of the product are: 34.5% hydrosulfate, 21% sodium carbonate, 3% sulfate, about 1% sulfur dioxide, 2% flocculant, and the rest is water.

[0031] Example 2: 520 kg of sodium thiosulfate pentahydrate was added to a reactor, 400 kg of water was added, and the mixture was heated to dissolve. At a temperature of 60°C-80°C, 60 kg of a catalyst (homemade) was added to decompose the thiosulfate ion. Samples were taken at any time to detect the S content in the material. 2- When the content reaches the requirement, add 20kg flocculant, cool down, and the purifier is yellow-green transparent liquid with no sediment. The main components of the product are: 34.8% hydrosulfate, 22% sodium carbonate, 3% sulfate, 1% sulfur dioxide, 2% flocculant, and the rest is water.

[0032] Example 3: 600 kg of sodium thiosulfate pentahydrate was added to a reactor, 350 kg of water was added, and the mixture was heated to dissolve. At a temperature of 60°C-80°C, 80 kg of a catalyst (homemade) was added to decompose the thiosulfate ion. Samples were taken at any time to detect the S content in the material. 2- When the content reaches the requirement, add 20kg flocculant. Cool down, the purifier obtained is a yellow-green transparent liquid with no sediment. The main components of the product are: 40.0% hydrosulfate, 24.4% sodium carbonate, 3% sulfate, 1% sulfur dioxide, 2% flocculant, and the rest is water.

[0033] Phosphoric acid purifiers should meet the following requirements:

[0034]

[0035] Take 424.38g of concentrated phosphoric acid and put it into a beaker. When heated to 85℃, gradually add 10ml of new phosphoric acid purifier from the bottom of the beaker, stir for 15 minutes, and use a detector to detect the content of H2S produced.

[0036] Experimental phenomena and results

[0037] Slowly add arsenic remover from the bottom of the beaker. When 6 mL of arsenic remover is added, the H2S detector shows a value of 25 ppm. As the arsenic remover is slowly added, the amount of hydrogen sulfide gas produced gradually decreases.

[0038] Through the above test, the records are as follows:

[0039] (1) During the stirring process, the H2S detector shows a value less than 10ppm.

[0040] (2) During filtration, no hydrogen sulfide gas was detected in the Buchner funnel.

[0041] (3) After filtration, the concentration of hydrogen sulfide in the sample bottle is less than 8 ppm.

[0042] The arsenic content in the original concentrated phosphoric acid was 48 mg / kg. After testing, the arsenic content in the treated concentrated phosphoric acid was 0.2 mg / kg.

[0043] It can be seen that the novel phosphoric acid purifier of the present invention can effectively remove arsenic in phosphoric acid, reducing the arsenic content to below 0.5 ppm.

[0044] The above is a detailed introduction to a novel phosphoric acid purifier and a preparation method thereof provided by the present invention. The structure and working principle of the present invention are described in detail using specific examples herein. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. It should be pointed out that for ordinary technicians in this technical field, without departing from the principle of the present invention, the present invention can also be improved and modified in a number of ways, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A novel phosphoric acid purifier, characterized in that: It comprises the following percentages by mass: 34-40.0% of hydrosulfate, 21-24% of sodium carbonate, 3% of sulfate, about 1% of sulfur dioxide, and the balance of water.

2. A method for preparing the novel phosphoric acid scavenger according to claim 1, characterized in that: The following steps are included: Step 1: Add measured sodium thiosulfate into a reactor, heat and dissolve it; Step 2: At a temperature of 60°C-80°C, add a measured amount of catalyst and an organic flocculant to prepare the product.

3. The method for preparing the novel phosphoric acid purifier according to claim 1, characterized in that: The prepared phosphoric acid purifier is a yellow-green transparent liquid.

4. The method for preparing the novel phosphoric acid purifier according to claim 1, characterized in that: The specific dosage is as follows: 50%-60% sodium thiosulfate, 5%-8% catalyst, 2%-3% organic flocculant and 35%-43% water in percentage by mass.

5. The method for preparing the novel phosphoric acid purifier according to claim 1, characterized in that: The obtained phosphoric acid purifier has an effective matter content of ≥13% calculated on the basis of H2S.

6. The method for preparing the novel phosphoric acid purifier according to claim 1, characterized in that: The fluoride content of the obtained phosphoric acid purifier in terms of F- is ≤0.001%.

7. The method for preparing the novel phosphoric acid purifier according to claim 1, characterized in that: The obtained phosphoric acid purifier has a heavy metal content of ≤0.0005% in terms of Pb.

8. The method for preparing the novel phosphoric acid purifier according to claim 1, characterized in that: The obtained phosphoric acid purifier has an oxidizable substance of 0.012% or less based on PO3.

9. The method for preparing the novel phosphoric acid purifier according to claim 1, characterized in that: The pH of the obtained phosphoric acid purifier is 10.0-12.

0.

10. The method for preparing the novel phosphoric acid purifier according to claim 1, characterized in that: The obtained phosphoric acid purifier has a density of 1.2-1.3 g / cm2 at 20°C.

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