A method for recovering arsenic from high concentration arsenic-containing wastewater

Abstract

This invention provides a method for recovering arsenic from high-concentration arsenic-containing wastewater, comprising the following steps: a) mixing the high-concentration arsenic-containing wastewater with concentrated sulfuric acid for the first time, followed by a first distillation to obtain a first acid solution and a first arsenic-rich solution; b) mixing the first arsenic-rich solution obtained in step a) with concentrated sulfuric acid for the second time, followed by a second distillation to obtain a second acid solution and arsenic trichloride. Compared with the prior art, this invention first mixes concentrated sulfuric acid with high-concentration arsenic-containing wastewater and then distills to obtain a first arsenic-rich solution, and then mixes the first arsenic-rich solution with concentrated sulfuric acid and distills to obtain arsenic trichloride. This method is simple and easy to operate, the sulfuric acid used can be recycled after dehydration treatment, no waste residue is generated during the process, no post-treatment is required, and the obtained arsenic trichloride has high purity and can be used as a raw material for the production of high-purity arsenic.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and more specifically, to a method for recovering arsenic from high-concentration arsenic-containing wastewater. Background Technology

[0002] High-purity arsenic, as an important chemical raw material, is widely used in the manufacture of compound semiconductors, infrared transmission glass, hard alloys, and pharmaceuticals. The production process of high-purity arsenic generates a large amount of arsenic-containing wastewater. Arsenic-containing substances can cause serious harm to organisms and the environment; therefore, arsenic-containing wastewater must be treated to meet harmless treatment standards before it can be discharged.

[0003] Currently, the main methods for treating arsenic-containing wastewater include chemical precipitation, adsorption, and microbial methods, with chemical precipitation being the most widely used. Chemical precipitation uses acid-base neutralization, flocculant precipitation, and sulfide precipitation to remove arsenic from the water. This method is simple to operate, but it generates a large amount of sludge, and the arsenic-containing waste sludge still requires secondary treatment, which can easily lead to secondary pollution. Adsorption uses chemically synthesized or processed natural materials to prepare adsorbents to adsorb arsenic from wastewater, achieving good adsorption effects. However, the treatment of the arsenic-containing materials after adsorption still requires further research and exploration. Microbial methods use bacteria to treat arsenic-containing wastewater, causing arsenic to precipitate in the form of arsenic trioxide (or arsenic-containing litharge) to achieve arsenic removal. However, the bacterial cultivation period is long, and it has high requirements for the water environment, making industrial implementation difficult. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a method for recovering arsenic from high-concentration arsenic-containing wastewater. This method is simple and easy to operate, the sulfuric acid used can be recycled, and no waste residue is generated. No post-treatment is required, and the obtained arsenic trichloride has high purity and can be used as a raw material for the production of high-purity arsenic.

[0005] This invention provides a method for recovering arsenic from high-concentration arsenic-containing wastewater, comprising the following steps:

[0006] a) After mixing high-concentration arsenic-containing wastewater with concentrated sulfuric acid for the first time, a first distillation is performed to obtain the first acid solution and the first arsenic-rich solution, respectively.

[0007] b) After mixing the first arsenic-rich solution obtained in step a) with concentrated sulfuric acid for the second time, a second distillation is performed to obtain the second acid solution and arsenic trichloride, respectively.

[0008] Preferably, in step a), the high-concentration arsenic-containing wastewater has an arsenic content of 20 g / L to 80 g / L and an HCl content of 4 mol / L to 11 mol / L.

[0009] Preferably, the concentrated sulfuric acid in step a) is sulfuric acid with a mass fraction greater than 90%.

[0010] Preferably, the volume ratio of the high-concentration arsenic-containing wastewater to concentrated sulfuric acid in step a) is 1:(1.5-3).

[0011] Preferably, the first mixing process in step a) specifically includes:

[0012] Add concentrated sulfuric acid to high-concentration arsenic-containing wastewater and stir for 1 to 4 hours to complete the first mixing process.

[0013] Preferably, the first distillation process in step a) specifically includes:

[0014] The mixture is heated in a distillation apparatus, and the fraction at 115℃~120℃ is collected to obtain the first acid solution; the fraction at 130℃~140℃ is then collected to obtain the first arsenic-rich solution.

[0015] Preferably, in step b), the volume ratio of the first arsenic-rich solution to concentrated sulfuric acid is 1:(0.5-1.5).

[0016] Preferably, the second mixing process in step b) specifically involves:

[0017] Concentrated sulfuric acid was added to the first arsenic-rich solution and mixed to complete the second mixing process.

[0018] Preferably, the second distillation process in step b) specifically comprises:

[0019] The mixture is heated in a distillation apparatus, and the fraction at 115℃~120℃ is collected to obtain the second acid solution; the fraction at 130℃~140℃ is then collected to obtain the second arsenic-rich solution, which is arsenic trichloride.

[0020] Preferably, both the first acid solution and the second acid solution are hydrochloric acid.

[0021] This invention provides a method for recovering arsenic from high-concentration arsenic-containing wastewater, comprising the following steps: a) mixing the high-concentration arsenic-containing wastewater with concentrated sulfuric acid for the first time, followed by a first distillation to obtain a first acid solution and a first arsenic-rich solution; b) mixing the first arsenic-rich solution obtained in step a) with concentrated sulfuric acid for the second time, followed by a second distillation to obtain a second acid solution and arsenic trichloride. Compared with the prior art, this invention first mixes concentrated sulfuric acid with high-concentration arsenic-containing wastewater and then distills to obtain a first arsenic-rich solution, and then mixes the first arsenic-rich solution with concentrated sulfuric acid and distills to obtain arsenic trichloride. This method is simple and easy to operate, the sulfuric acid used can be recycled after dehydration treatment, no waste residue is generated during the process, no post-treatment is required, and the obtained arsenic trichloride has high purity and can be used as a raw material for the production of high-purity arsenic. Attached Figure Description

[0022] Figure 1 The process flow diagram of the method for recovering arsenic from high-concentration arsenic-containing wastewater provided by the present invention. Detailed Implementation

[0023] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] This invention provides a method for recovering arsenic from high-concentration arsenic-containing wastewater, comprising the following steps:

[0025] a) After mixing high-concentration arsenic-containing wastewater with concentrated sulfuric acid for the first time, a first distillation is performed to obtain the first acid solution and the first arsenic-rich solution, respectively.

[0026] b) After mixing the first arsenic-rich solution obtained in step a) with concentrated sulfuric acid for the second time, a second distillation is performed to obtain the second acid solution and arsenic trichloride, respectively.

[0027] This invention first mixes high-concentration arsenic-containing wastewater with concentrated sulfuric acid, followed by a first distillation to obtain a first acid solution and a first arsenic-rich solution. In this invention, the arsenic content in the high-concentration arsenic-containing wastewater is preferably 20 g / L to 80 g / L, more preferably 20 g / L to 50 g / L; the HCl content is preferably 4 mol / L to 11 mol / L, more preferably 4 mol / L to 5 mol / L; and preferably also includes: ≤100 mg / L Fe; ≤100 mg / L Se; ≤100 mg / L Bi; ≤100 mg / L Cu; ≤100 mg / L Sb. Furthermore, the high-concentration arsenic-containing wastewater can also be considered as wastewater containing arsenic trichloride.

[0028] In this invention, the concentrated sulfuric acid is preferably sulfuric acid with a mass fraction greater than 90%, more preferably sulfuric acid with a mass fraction of 98%. This invention does not impose any special restrictions on the source of the concentrated sulfuric acid; commercially available products or homemade products well-known to those skilled in the art can be used.

[0029] In this invention, the volume ratio of the high-concentration arsenic-containing wastewater to concentrated sulfuric acid is preferably 1:(1.5-3), more preferably 1:(1.5-2).

[0030] In this invention, the first mixing process is preferably specifically as follows:

[0031] Add concentrated sulfuric acid to high-concentration arsenic-containing wastewater and stir for 1 to 4 hours to complete the first mixing process.

[0032] More preferably:

[0033] Concentrated sulfuric acid is added to high-concentration arsenic-containing wastewater, and the mixture is stirred for 2 hours to complete the first mixing process. This invention does not impose any particular limitation on the stirring method; any manual or mechanical stirring technique well-known to those skilled in the art can be used. The aim is to ensure that all components are mixed uniformly.

[0034] In this invention, the first distillation process is preferably specifically as follows:

[0035] The mixture is heated in a distillation apparatus, and the fraction at 115℃~120℃ is collected to obtain the first acid solution; the fraction at 130℃~140℃ is then collected to obtain the first arsenic-rich solution.

[0036] The present invention employs step a) above, namely the first addition of concentrated sulfuric acid during distillation, which has two functions: First, by utilizing the water solubility of concentrated sulfuric acid, the system becomes a sulfuric acid solution system with a mass fraction greater than 70%, thus disrupting the azeotropic system of the hydrochloric acid aqueous solution, making it easier for the hydrochloric acid to distill off and separate into high-concentration hydrochloric acid. The fraction collected at 115℃~120℃ is obtained as the first acid solution, i.e., hydrochloric acid. The fraction collected at 130℃~140℃ is then obtained as the first arsenic-rich solution, which mainly contains a small amount of hydrochloric acid and arsenic trichloride. Second, some impurities enter the sulfuric acid solution, achieving the effect of impurity removal.

[0037] After obtaining the first arsenic-rich solution, the present invention mixes the first arsenic-rich solution with concentrated sulfuric acid for a second time, and then performs a second distillation to obtain a second acid solution and arsenic trichloride, respectively. In the present invention, the concentrated sulfuric acid is the same as that in the above technical solution, and will not be described again here.

[0038] In this invention, the volume ratio of the first arsenic-rich solution to concentrated sulfuric acid is preferably 1:(0.5-1.5), more preferably 1:1.

[0039] In this invention, the second mixing process is preferably specifically as follows:

[0040] Concentrated sulfuric acid is added to the first arsenic-rich solution and mixed to complete the second mixing process. This invention does not impose any particular limitation on the mixing method; any technique known to those skilled in the art, such as manual stirring or mechanical stirring, can be used. The aim is to ensure that all components are mixed uniformly.

[0041] In this invention, the second distillation process is preferably specifically as follows:

[0042] The mixture is heated in a distillation apparatus, and the fraction at 115℃~120℃ is collected to obtain the second acid solution; the fraction at 130℃~140℃ is then collected to obtain the second arsenic-rich solution, which is arsenic trichloride.

[0043] The present invention employs step b) above, namely the second addition of concentrated sulfuric acid (adding concentrated sulfuric acid to the first arsenic-rich solution) distillation process, which has two functions. One function is to further absorb the water in the first arsenic-rich solution. Through distillation, the temperature is controlled to separate hydrochloric acid at 115℃~120℃ and arsenic trichloride at 130℃~140℃. The other function is that sulfuric acid can absorb some impurities, thereby increasing the purity of arsenic trichloride.

[0044] In this invention, both the first acid solution and the second acid solution are hydrochloric acid.

[0045] This invention provides a new technology for recovering arsenic from high-concentration arsenic-containing wastewater. The process is simple and easy to operate. While recovering arsenic, it reduces the arsenic content in the wastewater, which is environmentally friendly. The arsenic recovery rate reaches more than 93%.

[0046] This invention provides a method for recovering arsenic from high-concentration arsenic-containing wastewater, comprising the following steps: a) mixing the high-concentration arsenic-containing wastewater with concentrated sulfuric acid for the first time, followed by a first distillation to obtain a first acid solution and a first arsenic-rich solution; b) mixing the first arsenic-rich solution obtained in step a) with concentrated sulfuric acid for the second time, followed by a second distillation to obtain a second acid solution and arsenic trichloride. Compared with the prior art, this invention first mixes concentrated sulfuric acid with high-concentration arsenic-containing wastewater and then distills to obtain a first arsenic-rich solution, and then mixes the first arsenic-rich solution with concentrated sulfuric acid and distills to obtain arsenic trichloride. This method is simple and easy to operate, the sulfuric acid used can be recycled after dehydration treatment, no waste residue is generated during the process, no post-treatment is required, and the obtained arsenic trichloride has high purity and can be used as a raw material for the production of high-purity arsenic.

[0047] To further illustrate the present invention, the following detailed description is provided through the examples below. The high-concentration arsenic-containing wastewater used in the following examples of the present invention contains the following components: As: 25780 mg / L, Fe: 19 mg / L, Se: 4 mg / L, Bi: 64 mg / L, and HCl: 168.6 g / L.

[0048] Example 1

[0049] (1) Slowly add 1.5L of 98% sulfuric acid to 1L of high-concentration arsenic-containing wastewater, stir for 2 hours, and then heat and distill. Collect the distillate at 115℃~120℃ to obtain 370mL of hydrochloric acid-rich solution; then collect the fraction at 130℃~140℃ to obtain 38mL of the first arsenic-rich solution.

[0050] (2) Slowly add 98% sulfuric acid at a volume ratio of 1:1 to the first arsenic-rich solution obtained in step (1), mix and then distill. Collect the distillate at 115℃~120℃ to obtain 20mL of hydrochloric acid-rich solution; collect the fraction at 130℃~140℃ to obtain 58.5g of the second arsenic-rich solution, which is arsenic trichloride; detection and analysis showed that the purity was above 99.9% and the recovery rate was 93.7%.

[0051] Example 2

[0052] (1) Slowly add 2.0L of 98% sulfuric acid to 1L of high-concentration arsenic-containing wastewater, stir for 2h, then heat and distill, collect the distillate at 115℃~120℃ to obtain 391mL of hydrochloric acid-rich solution; then collect the fraction at 130℃~140℃ to obtain 36mL of the first arsenic-rich solution.

[0053] (2) Slowly add 98% sulfuric acid at a volume ratio of 1:1 to the first arsenic-rich solution obtained in step (1), mix and then distill. Collect the distillate at 115℃~120℃ to obtain 11mL of hydrochloric acid-rich solution; collect the fraction at 130℃~140℃ to obtain 60.5g of the second arsenic-rich solution, which is arsenic trichloride; detection and analysis show that the purity is above 99.9% and the recovery rate is 97.0%.

[0054] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for recovering arsenic from high-concentration arsenic-containing wastewater, comprising the following steps: a) After mixing high-concentration arsenic-containing wastewater with concentrated sulfuric acid for the first time, a first distillation is performed to obtain a first acid solution and a first arsenic-rich solution in sequence; the volume ratio of the high-concentration arsenic-containing wastewater to concentrated sulfuric acid is 1:(1.5~3); the first distillation process is as follows: the mixture is heated in a distillation apparatus, and the fraction at 115℃~120℃ is collected to obtain the first acid solution; then the fraction at 130℃~140℃ is collected to obtain the first arsenic-rich solution; The first acid solution is hydrochloric acid; b) After mixing the first arsenic-rich solution obtained in step a) with concentrated sulfuric acid for the second time, a second distillation is performed to obtain the second acid solution and arsenic trichloride in sequence; the volume ratio of the first arsenic-rich solution to concentrated sulfuric acid is 1:(0.5~1.5); the second distillation process is as follows: the mixture is heated in a distillation apparatus, and the fraction at 115℃~120℃ is collected to obtain the second acid solution; then the fraction at 130℃~140℃ is collected to obtain the second arsenic-rich solution, which is arsenic trichloride; the second acid solution is hydrochloric acid.

2. The method for recovering arsenic from high-concentration arsenic-containing wastewater according to claim 1, characterized in that, In step a), the high-concentration arsenic-containing wastewater has an arsenic content of 20 g / L to 80 g / L and an HCl content of 4 mol / L to 11 mol / L.

3. The method for recovering arsenic from high-concentration arsenic-containing wastewater according to claim 1, characterized in that, The concentrated sulfuric acid mentioned in step a) is sulfuric acid with a mass fraction greater than 90%.

4. The method for recovering arsenic from high-concentration arsenic-containing wastewater according to claim 1, characterized in that, The first mixing process described in step a) is specifically as follows: Add concentrated sulfuric acid to high-concentration arsenic-containing wastewater and stir for 1 to 4 hours to complete the first mixing process.

5. The method for recovering arsenic from high-concentration arsenic-containing wastewater according to claim 1, characterized in that, The second mixing process described in step b) is specifically as follows: Concentrated sulfuric acid was added to the first arsenic-rich solution and mixed to complete the second mixing process.

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