Resourceful treatment technology for alkali liquor generated in tungsten hexafluoride tail gas treatment

Abstract

The invention belongs to the technical field of resource circulation and water treatment, and particularly relates to a resourceful treatment technology for alkali liquor generated in tungsten hexafluoride tail gas treatment. The method specifically comprises the steps that S1, sulfuric acid is added into the alkaline waste liquid generated in tungsten hexafluoride tail gas treatment, stirring is conducted, then solid-liquid separation is conducted, solid is tungstic acid, and supernate is mixed liquid of potassium sulfate and potassium fluoride; s2, washing the tungstic acid with deionized water, carrying out solid-liquid separation, collecting the liquid for washing the tungstic acid, and drying the washed tungstic acid; and S3, mixing a mixed solution of potassium sulfate and potassium fluoride in the step S1 with the liquid for cleaning tungstic acid in the step S2, adding slaked lime into the mixed liquid, fully stirring until no precipitate is generated, and carrying out solid-liquid separation to remove solid residues so as to obtain a supernatant which is a potassium hydroxide solution. The method is mild in reaction condition, short in process, easy to operate and high in metal element recovery rate.

Description

Technical Field

[0001] This application belongs to the technical field of resource recycling and water treatment, and specifically relates to a resource treatment technology for the alkali solution generated in the treatment of tungsten hexafluoride tail gas. Background Art

[0002] Tungsten hexafluoride (WF6) is an inorganic compound widely used in the electronics industry, mainly used for the preparation of high-purity metallic tungsten, and is commonly used in chemical vapor deposition (CVD) and physical vapor deposition (PVD) processes in a vacuum. It has excellent electron transport properties and is also widely used in fields such as semiconductor manufacturing, coatings, and optical thin films. In recent years, with the continuous development and progress of the electronics industry, the demand for tungsten hexafluoride has been increasing day by day.

[0003] However, during the production process of tungsten hexafluoride, some tail gas is discharged, and the tail gas contains toxic WF6 gas, which needs to meet national standards before it can be discharged. Therefore, many researchers have tried to recycle the tail gas generated during the production process of tungsten hexafluoride in order to recover the metal utilization rate and reduce environmental pollution. Chinese Patent No. CN220214475U discloses a tungsten hexafluoride tail gas treatment system. First, the tail gas is passed through primary water washing to convert tungsten hexafluoride gas into WO4 2- , F - ions, and then WO4 2- , F - ions are converted into precipitates through a reaction kettle, the precipitates are separated by filtration, and then through an evaporation device, the water is recycled. This treatment realizes the resource treatment of hexafluoride tail gas. WO4 2- ions exist in the form of tungstic acid and calcium tungstate. This treatment method directly treats the tail gas. The entire process flow includes water washing, precipitation, evaporation, etc. The complex recovery process directly leads to an increase in costs. At the same time, due to the need for the treatment system to be closely integrated with the preparation process of tungsten hexafluoride, it further increases the complexity of operation and the dependence of the system.

[0004] Currently, for the treatment of tail gas, it is more common to first absorb the tail gas with an alkali solution to obtain an alkali solution containing tungsten and potassium, and then further treat the alkali solution containing tungsten and potassium. There is mainly one common treatment method, which is to directly add lime or calcium chloride. Tungsten is converted into a mixture of calcium tungstate and calcium fluoride for treatment. However, this process has the following problems: the materials in the process cannot be recycled. The recovery rate of precious metal tungsten is low, no additional by-products are generated, and the resource utilization of solid waste is not realized, resulting in great waste.

[0005] In summary, there are still problems such as complex process flow and precious metal recovery rate in the treatment of tungsten hexafluoride tail gas. Therefore, it is urgent to propose a resource treatment technology for the alkali liquor generated in the treatment of tungsten hexafluoride tail gas to solve the current problems. Summary of the Invention

[0006] Aiming at the problems of complex process flow and precious metal recovery rate in the treatment of tungsten hexafluoride tail gas in the prior art, this application proposes a resource treatment technology for the alkali liquor generated in the treatment of tungsten hexafluoride tail gas, with a short process flow and a high recovery rate of precious metal tungsten, having high economic and environmental benefits.

[0007] The specific solution of this application is as follows:

[0008] A resource treatment technology for the alkali liquor generated in the treatment of tungsten hexafluoride tail gas, comprising the following steps:

[0009] Step S1. Add sulfuric acid to the alkaline waste liquor generated from the treatment of tungsten hexafluoride tail gas and stir to react until the pH value of the mixed liquor is 7-8, and then perform solid-liquid separation, where the solid is tungstic acid and the supernatant is a mixed solution of potassium sulfate and potassium fluoride;

[0010] Step S2. After washing tungstic acid with deionized water and performing solid-liquid separation, collect the liquid for washing tungstic acid, and dry the washed tungstic acid;

[0011] Step S3. Mix the mixed solution of potassium sulfate and potassium fluoride in Step S1 with the liquid for washing tungstic acid in Step S2, and then add slaked lime to the mixed liquid and stir well to obtain a supernatant of potassium hydroxide solution.

[0012] Preferably, the concentration of sulfuric acid in Step S1 is 2 mol / L.

[0013] Preferably, the stirring reaction time in Step S1 is 0.5-1 h.

[0014] Preferably, the drying temperature in Step S2 is 100 °C.

[0015] Preferably, the purity of slaked lime in Step S3 is 95%.

[0016] Preferably, the mass ratio of the alkaline waste liquor to slaked lime is 1:(0.2-0.24); the addition method of slaked lime is: add it once every 1 h and finish adding it in 3 times, where the addition amount for the first time is 1 / 2 of the total mass of slaked lime, and the addition amounts for the second and third times are both 1 / 4 of the total amount of slaked lime, and continuously stir for 4-6 h during the reaction process.

[0017] The beneficial effects of this application are as follows:

[0018] (1) Mild conditions and short process: This process is carried out at normal temperature and pressure, without the need for high temperature and high pressure. The process is short, the equipment is simple, and it is easy to operate. This not only reduces the equipment cost, but also reduces energy consumption, and improves the convenience and safety of operation.

[0019] (2) Improve the utilization rate of slaked lime: The way of adding slaked lime in stages during the precipitation process minimizes the adsorption and encapsulation of CaF2 crystals on the undissolved lime, thus improving the utilization rate of slaked lime. By adding slaked lime in stages, the reaction process can be more evenly controlled, reducing the encapsulation of unreacted lime by CaF2 crystals, thereby improving the utilization rate of slaked lime and reducing waste.

[0020] (3) Resource utilization: This process recovers tungsten and potassium elements in stages. The quality of the tungstic acid product obtained meets the national standards, and the generated KOH solution can be used to repeatedly absorb the waste gas generated during the production of tungsten hexafluoride, avoiding secondary pollution. Through this way of staged recovery, not only the efficient recovery of tungsten and potassium is achieved, but also the emission of waste is reduced, with obvious economic and environmental benefits. Description of the Drawings

[0021] Appendix Figure 1 It is a process flow chart for the resource treatment of the alkali solution generated in the treatment of tungsten hexafluoride tail gas. Detailed Embodiments

[0022] To further elaborate on the technical means and effects adopted by this application to achieve the intended invention purpose, the following, in combination with preferred embodiments, details the specific embodiments, structures, features and their effects according to this application as follows.

[0023] It should be noted that the contents of potassium and tungsten elements in the alkali solution used in Examples 1 to 3 are shown in Table 1. For the specific process, refer to Appendix Figure 1 .

[0024] Table 1

[0025] element potassium element tungsten element Content (wt.%) 10 6.1

[0026] Example 1

[0027] Step S1: Take 2 kg of alkali solution. Under the conditions of normal temperature (25 °C) and normal pressure (101 KPa), while stirring, slowly add 0.375 kg of sulfuric acid with a molar concentration of 2 mol / l to the alkali solution for acidolysis reaction for 0.5 h. Use a pH detection instrument to detect that the pH value of the mixed solution is 7, and then perform solid-liquid centrifugal separation. The solid is tungstic acid, and the supernatant is a mixed solution of potassium sulfate and potassium fluoride;

[0028] Step S2. Wash the tungstic acid obtained in Step S1 with deionized water, perform solid-liquid separation, collect the liquid used for washing the tungstic acid for standby, then dry the washed tungstic acid at 100 °C for 12 hours to obtain 0.165 kg of tungstic acid with a purity of 97% and a tungsten recovery rate of 95.6%.

[0029] Step S3. Under the conditions of normal temperature (25 °C) and normal pressure (101 KPa), mix the mixed solution of potassium sulfate and potassium fluoride in Step S1 with the liquid used for washing the tungstic acid in Step S2, then add slaked lime with a purity of 95% to the mixed liquid. The slaked lime is added once every 1 h and added in 3 portions. The reaction process is continuously stirred for 6 h until no more precipitation occurs. A total of 0.41 kg of slaked lime is added. Perform solid-liquid separation to remove calcium sulfate, calcium fluoride and other fluorine-containing solid residues to obtain 1.9 kg of clear potassium hydroxide aqueous solution; the concentration of potassium hydroxide is 14.7% and the recovery rate of potassium element is 93.1%.

[0030] Example 2

[0031] Step S1. Take 2 kg of alkali solution. Under the conditions of normal temperature (25 °C) and normal pressure (101 KPa), slowly add 0.382 kg of sulfuric acid with a molar concentration of 2 mol / l to the alkali solution dropwise while stirring for an acidolysis reaction for 1 h. Use a pH detection instrument to detect that the pH value of the mixed solution is 7, and then perform solid-liquid centrifugal separation. The solid is tungstic acid and the supernatant is a mixed solution of potassium sulfate and potassium fluoride.

[0032] Step S2. Wash the tungstic acid obtained in Step S1 with deionized water, perform solid-liquid separation, collect the liquid used for washing the tungstic acid for standby, then dry the washed tungstic acid at 100 °C for 12 hours to obtain 0.172 kg of tungstic acid with a purity of 96.9% and a tungsten recovery rate of 95.7%.

[0033] Step S3. Under the conditions of normal temperature (25 °C) and normal pressure (101 KPa), mix the mixed solution of potassium sulfate and potassium fluoride in Step S1 with the liquid used for washing the tungstic acid in Step S2, then add slaked lime with a purity of 95% to the mixed liquid. The slaked lime is added once every 1 h and added in 3 portions. The reaction process is continuously stirred for 5 h until no more precipitation occurs. A total of 0.40 kg of slaked lime is added. Perform solid-liquid separation to remove calcium sulfate, calcium fluoride and other fluorine-containing solid residues to obtain 1.95 kg of clear potassium hydroxide aqueous solution; the concentration of potassium hydroxide is 14.5% and the recovery rate of potassium element is 92.7%.

[0034] Example 3

[0035] Step S1: Take 4 kg of lye. Under the conditions of normal temperature (25 °C) and normal pressure (101 KPa), while stirring, slowly add 0.790 kg of sulfuric acid with a molar concentration of 2 mol / l to the lye for acidolysis reaction for 0.8 h. Use a pH detection instrument to detect that the pH value of the mixed solution is 9. Then, perform solid-liquid centrifugal separation. The solid is tungstic acid, and the supernatant is a mixed solution of potassium sulfate and potassium fluoride;

[0036] Step S2: Wash the tungstic acid in Step S1 with deionized water and perform solid-liquid separation. Collect the liquid for washing the tungstic acid for later use. Then, dry the washed tungstic acid at 100 °C for 12 hours to obtain 0.35 kg of tungstic acid. The purity of the tungstic acid is 98%, and the recovery rate of tungsten is 94.4%;

[0037] Step S3: Under the conditions of normal temperature (25 °C) and normal pressure (101 KPa), mix the mixed solution of potassium sulfate and potassium fluoride in Step S1 with the liquid for washing the tungstic acid in Step S2. Then, add slaked lime with a purity of 95% to the mixed liquid. The slaked lime is added once every 1 h and is added in 3 times. The reaction process is continuously stirred for 6 h until no more precipitation occurs. A total of 0.96 kg of slaked lime is added. Perform solid-liquid separation to remove calcium sulfate, calcium fluoride, and other fluorine-containing solid residues to obtain 3.9 kg of clear potassium hydroxide aqueous solution. The concentration of potassium hydroxide is 15.1%, and the recovery rate of potassium element is 94.3%.

[0038] Result Analysis

[0039] Through the recovery method of this application, tungsten elements and potassium elements can be effectively recycled. The process of this application is carried out at normal temperature and normal pressure, without the need for high temperature and high pressure. The process is short, the equipment is simple, and it is easy to operate. The way of adding slaked lime in stages during the precipitation process minimizes the adsorption and encapsulation of CaF2 crystals on the undissolved lime, improving the utilization rate of slaked lime. This process recovers tungsten and potassium elements separately. The quality of the obtained tungstic acid product meets the national standards, and the generated KOH solution can be used to repeatedly absorb the waste gas generated during the production process of tungsten hexafluoride, avoiding the occurrence of secondary pollution.

[0040] The above is only a preferred embodiment of this application, and it does not impose any form of limitation on this application. Although this application has been disclosed above with a preferred embodiment, it is not intended to limit this application. Any person skilled in the art can make some changes or modifications to be equivalent embodiments with equivalent changes within the scope of the technical solution of this application. However, as long as it does not depart from the content of the technical solution of this application, any modification, equivalent change, and modification made to the above embodiment based on the technical essence of this application still fall within the scope of the technical solution of this application.

Claims

1. A resource treatment technology for generating alkaline solution in the treatment of tungsten hexafluoride tail gas, characterized in that, It includes the following steps: Step S1. Add sulfuric acid to the alkaline waste liquid generated from the tail gas treatment of tungsten hexafluoride, stir and react until the pH value of the mixed liquid is 7-8, and then perform solid-liquid separation. The solid is tungstic acid, and the supernatant is a mixed liquid of potassium sulfate and potassium fluoride; Step S2. After washing the tungstic acid with deionized water and performing solid-liquid separation, collect the liquid for washing the tungstic acid, and dry the washed tungstic acid; Step S3. Mix the mixed liquid of potassium sulfate and potassium fluoride in Step S1 with the liquid for washing the tungstic acid in Step S2, and then add slaked lime to the mixed liquid and stir well to obtain a supernatant of potassium hydroxide solution.

2. The resource treatment technology for generating lye in the treatment of tungsten hexafluoride tail gas according to claim 1, characterized in that, The concentration of sulfuric acid in Step S1 is 2 mol / L.

3. The resource treatment technology for generating alkaline solution in the treatment of tungsten hexafluoride tail gas according to claim 1, characterized in that, The stirring reaction time in Step S1 is 0.5-1 h.

4. A resource treatment technology for generating alkaline solution in the treatment of tungsten hexafluoride tail gas according to claim 1, characterized in that, The drying temperature in Step S2 is 100 °C.

5. A resource treatment technology for generating alkaline solution in the treatment of tungsten hexafluoride tail gas according to claim 1, characterized in that, The purity of slaked lime in Step S3 is 95%.

6. The resource treatment technology for generating lye in the treatment of tungsten hexafluoride tail gas according to claim 1, characterized in that, The mass ratio of the alkaline waste liquid to slaked lime is 1:(0.2-0.24); the addition method of slaked lime is: add it once every 1 h and finish adding it in 3 times. The addition amount for the first time is 1 / 2 of the total mass of slaked lime, and the addition amounts for the second and third times are both 1 / 4 of the total amount of slaked lime. The reaction process is continuously stirred for 4-6 h.

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