Concentration and purification method of hydrofluoric acid waste liquid

Abstract

The invention relates to a concentration and purification method of hydrofluoric acid waste liquid, which mainly comprises the following four steps of: adding an oxidizing agent to oxidize the hydrofluoric acid waste liquid, adding fluorine-containing salts, injecting gas for gas stripping and heating for distillation, so as to recover expensive hydrofluoric acid. And specific contributions are made.

Description

Technical Field

[0001] The present invention relates to a method for concentrating and purifying hydrofluoric acid waste liquid, which comprises four steps: oxidizing the hydrofluoric acid waste liquid by adding an oxidant, adding fluorine-containing salts, injecting gas for gas stripping, and heating and distilling, so as to recover expensive hydrofluoric acid.

Background Art

[0002] Hydrofluoric acid is an aqueous solution of hydrogen fluoride (HF), with strong corrosiveness, commonly known as hydrofluoric acid or bone dissolving water. Hydrofluoric acid has the ability to dissolve substances and is currently an important raw material used in high-tech industries such as semiconductor manufacturing processes, circuit board design and manufacturing, wafer packaging and testing, and solar photovoltaic panel assembly. Hydrofluoric acid is a high-unit-price material, and the market average price per metric ton often exceeds NT$45,000.

[0003] After various industrial process applications using hydrofluoric acid, many materials such as glass, metals, and organic compounds will be dissolved and immediately become highly toxic hydrofluoric acid waste liquid, which is a kind of hazardous waste. Among the current treatment methods for hydrofluoric acid waste liquid, the most common ones are adding calcium hydroxide or calcium oxide to form calcium fluoride as artificial fluorite, or adding aluminum-containing compounds to convert it into sodium hexafluoroaluminate (Na 3 AlF 6 ) as cryolite. However, the treatment methods of adding calcium compounds or aluminum-containing compounds are quite expensive. Moreover, the subsequent application channels of the artificial fluorite and cryolite produced after treatment are not good, resulting in the artificial fluorite and cryolite often having to end up as mountains of waste in the factory or being buried as waste, substantially wasting a large amount of treatment costs or raising concerns about secondary pollution. In addition, there are also methods of adding silicon and sodium to form sodium hexafluorosilicate (Na 2 SiF 6 )(water glass), or adding iron to form iron(III) fluoride trihydrate (FeF 3 ﹒3H 2 O), but their treatment costs are still high and the usability of the converted products is not high, so they are not the most ideal methods.

[0004] Since hydrofluoric acid is expensive, it is clearly a waste to convert the used hydrofluoric acid waste liquid into other items with low value. Instead, it would be the correct approach to purify hydrofluoric acid from the used hydrofluoric acid waste liquid as a high-unit-price material for recycling and reuse.

Summary of the Invention

[0005] The inventor of the present invention is specifically engaged in research work on environmental protection topics. In the actual experience of long-term R & D, it is realized that the expensive hydrofluoric acid cannot be recycled, which completely violates the principle of material cycle.

[0006] The main object of the present invention is to provide a method for concentrating and purifying hydrofluoric acid waste liquid that can recycle hydrofluoric acid.

[0007] To achieve the above object, the present invention provides a method for concentrating and purifying hydrofluoric acid waste liquid, which comprises four steps: performing oxidation treatment by adding an oxidizing agent to the hydrofluoric acid waste liquid, treating with a fluorine-containing salt in the hydrofluoric acid waste liquid, adding a stripping tube to the distillation barrel of the hydrofluoric acid waste liquid, and heating the distillation barrel of the hydrofluoric acid waste liquid. Among them:

[0008] When performing oxidation treatment by adding an oxidizing agent to the hydrofluoric acid waste liquid, the oxidizing agent can be: potassium permanganate, potassium dichromate, hydrogen peroxide (H 2 O 2 ) or ozone (O 3 ). In operation, when adding an oxidizing agent to the hydrofluoric acid waste liquid, the trivalent arsenic (As) compound contained in the hydrofluoric acid waste liquid is oxidized by the above oxidizing agent to form a pentavalent arsenic (As) compound. This pentavalent arsenic (As) compound exists in the gas phase and is not easily condensed in the purified hydrofluoric acid aqueous solution product. Therefore, it can be removed by an air pollution control device at the back end;

[0009] When treating with a fluorine-containing salt in the hydrofluoric acid waste liquid, the fluorine-containing salt can be: potassium fluoride, sodium fluoride, magnesium fluoride and other fluorinated salts. In operation, when adding a fluorine-containing salt to the hydrofluoric acid waste liquid, the hydrogen ions contained in the hydrofluoric acid waste liquid will form hydrogen fluoride with fluoride ions, which can increase the output of hydrofluoric acid in the purified hydrofluoric acid aqueous solution product;

[0010] When adding a stripping tube to a distillation barrel for hydrofluoric acid waste liquid, the stripping tube first extends vertically downward to form a vertical stripping tube section, and then bends at the bottom by an angle to form a non-vertical stripping tube section. The non-vertical stripping tube section can also partially protrude above the liquid surface. The bending angle can be horizontal (i.e., 0°) or within 30° above or below the horizontal (i.e., ±30°). The inner diameter of the vertical stripping tube section is between 1.0 cm and 2.5 cm. The gas used for stripping can be purified air, nitrogen, or argon. The temperature of the gas used for stripping is between 20°C and 120°C. The outlet of the non-vertical stripping tube section is placed at the bottom of the distillation barrel for hydrofluoric acid waste liquid. The inner diameter of the non-vertical stripping tube section is between 0.5 and 1.5 cm. The external spacing of the non-vertical stripping tube section is between 2.0 and 4.0 cm. The opening of the non-vertical stripping tube section is located at the upper or side position. The opening of the non-vertical stripping tube section is circular. The spacing between the opening of the non-vertical stripping tube section and the opening edge is between 2.0 and 4.0 cm. The flow rate of the added gas at the outlet of the opening of the non-vertical stripping tube section is between 0.3 and 1.5 m / s to increase the amount of recovered hydrofluoric acid. At the same temperature, adding the stripping tube for stripping and then heating (the gas temperature is between 20°C and 120°C), compared with simply heating, the efficiency improvement in the amount of recovered hydrofluoric acid is between 50% and 200%.

[0011] Perform a heating operation on the distillation barrel for hydrofluoric acid waste liquid so that the temperature is between 20°C and 120°C, which can increase the purification and recovery efficiency of hydrofluoric acid.

[0012] In the above method for concentrating and purifying hydrofluoric acid waste liquid, when adding an oxidant for oxidation treatment to the hydrofluoric acid waste liquid, the addition amount of the oxidant is calculated based on the chemical equivalent value of the oxidant required for the concentration of the trivalent arsenic (As) compound, and then an additional 50% - 250% is added as the actual addition amount for practical operation.

[0013] In the above method for concentrating and purifying hydrofluoric acid waste liquid, when adding a fluorine-containing salt for treatment to the hydrofluoric acid waste liquid, the addition amount of the fluorine-containing salt is calculated based on the total hydrogen ion concentration value of nitric acid, hydrochloric acid, and sulfuric acid containing water in the hydrofluoric acid waste liquid to obtain the reaction equivalent value of fluoride ions, and then 30% - 80% is added as the actual addition amount.

[0014] The above method for concentrating and purifying hydrofluoric acid waste liquid, wherein solid or semi-solid waste of sodium hexafluoroaluminate, sodium hexafluorosilicate or iron(III) fluoride trihydrate is subjected to an acid addition step to adjust the pH value of the solution to below 2.0, and then left standing for 1.0 to 5.0 minutes to dissolve the fluorine in the waste, forming hydrofluoric acid dissolved in the aqueous solution. Then, the aqueous solution in which hydrofluoric acid is dissolved is pumped into a distillation barrel for hydrofluoric acid, and then the four steps of oxidizing by adding an oxidant, treating with a fluorine-containing salt, injecting a gas for stripping, and heating and distilling are carried out in the above-mentioned hydrofluoric acid waste liquid to recover hydrofluoric acid.

[0015] The above method for concentrating and purifying hydrofluoric acid waste liquid, wherein the hydrofluoric acid distillate after heating and distilling treatment can be condensed through a condenser with a temperature between 0°C and 65°C, and several recovery bottles are connected in series subsequently. An absorbent is added to each recovery bottle, and the recovery bottles are in an ice bath at 0°C to 65°C to improve the recovery rate of hydrofluoric acid.

[0016] The above method for concentrating and purifying hydrofluoric acid waste liquid, wherein several distillation bottles can be connected in series for continuous fractional distillation, and then the subsequent recovery bottles are used for collection to recover hydrofluoric acid with higher purity and lower impurity concentration.

[0017] The above method for concentrating and purifying hydrofluoric acid waste liquid, wherein the absorbent is an aqueous solution of hydrofluoric acid, and 35% to 48% hydrofluoric acid is added as the absorbent to the first recovery bottle, and 10% to 30% hydrofluoric acid is added as the absorbent to the second recovery bottle.

[0018] The above method for concentrating and purifying hydrofluoric acid waste liquid, wherein the materials or linings of all pipelines and containers in contact with hydrofluoric acid during the treatment process need to use polytetrafluoroethylene (PTFE) or perfluoroalkoxy alkane (PFA) materials.

[0019] The advantages and beneficial effects of the present invention are as follows: The method for concentrating and purifying hydrofluoric acid waste liquid of the present invention mainly includes four steps of oxidizing by adding an oxidant, adding a fluorine-containing salt, injecting a gas for stripping, and heating and distilling in the hydrofluoric acid waste liquid to recover expensive hydrofluoric acid. The technology of the present invention is a completely new innovative technology, which will make a specific contribution to the recycling and reuse of hydrofluoric acid and resource circulation in the industry.

Description of the Drawings

[0020] Figure 1 It is a schematic diagram of the treatment process of the present invention.

Detailed Embodiments

[0021] First, the characteristics of hydrofluoric acid waste liquid will be described. The components in hydrofluoric acid waste liquid can often be divided into three major categories: aqueous phase, acid phase, and salts (including solid impurities). Hydrofluoric acid exists in the acid phase. The acid phase of hydrofluoric acid waste liquid is a combination of various acids. The five most common acid compound groups are hydrofluoric acid, nitric acid, hydrochloric acid, sulfuric acid, and organic acids. The boiling points of the above five acids are as follows: the boiling point of hydrofluoric acid is 19.5°C, the boiling point of nitric acid is 83°C, the boiling point of hydrochloric acid is 57°C, the boiling point of 10%-30% aqueous sulfuric acid is 50-108°C, and the boiling points of organic acids are: the boiling point of formic acid is 100.7°C, the boiling point of acetic acid is 118°C, the boiling point of propionic acid is 141.2°C, and the boiling point of butyric acid is 163.5°C. It can be seen that the boiling point of hydrofluoric acid (19.5°C) is relatively low.

[0022] The present invention has developed four steps for treating hydrofluoric acid waste liquid, namely adding an oxidizing agent for oxidation treatment, adding a fluorine-containing salt for treatment, injecting a gas for stripping treatment, and heating and distilling treatment, in order to recover hydrofluoric acid. The four steps of adding an oxidizing agent for oxidation treatment, adding a fluorine-containing salt for treatment, injecting a gas for stripping treatment, and heating and distilling treatment are listed in detail below. Please refer to Figure 1 as shown.

[0023] I. Adding an oxidizing agent to the hydrofluoric acid waste liquid for oxidation treatment:

[0024] As mentioned above, hydrofluoric acid is an important raw material used in the high-tech industry. In actual applications, the hydrofluoric acid waste liquid generated often contains trivalent arsenic (As) compounds (for example: arsenic trioxide (As 2 O 3 ))). After arsenic trioxide (As 2 O 3 ) reacts with hydrofluoric acid, arsenic trifluoride (AsF 3 ) will be formed, and its boiling point is 57.1°C. When the hydrofluoric acid waste liquid is concentrated and purified conventionally, arsenic trifluoride (AsF 3 ) will condense together with the hydrofluoric acid waste liquid and water vapor and exist in the purified hydrofluoric acid waste liquid product and cannot be separated, so the treatment effect is obviously not good. To solve this problem, the present invention has developed through experimental verification that for trivalent arsenic (As) compounds in hydrofluoric acid waste liquid (for example: arsenic trioxide (As 2 O 3 ))), oxidation treatment must be carried out first to make it separated. Therefore, when adding an oxidizing agent to the hydrofluoric acid waste liquid for oxidation treatment in the present invention, the oxidizing agent that can be used is: potassium permanganate, potassium dichromate, hydrogen peroxide (H 2 O 2 ) or ozone (O 3 ); as for the addition amount of the oxidizing agent, if it is for trivalent arsenic (As) compounds, for example: arsenic trifluoride (AsF 3), there is a stoichiometric value of the oxidant required for concentration calculation, and an additional 50% - 250% is added as the actual operation addition amount. In operation, when trivalent arsenic (As) compounds, such as arsenic trifluoride (AsF 3 ), are oxidized by the above-mentioned oxidant, pentavalent arsenic (As) compounds, such as arsenic pentafluoride (AsF 5 ), will be formed, and its boiling point is -52.8 °C. Because the boiling point of arsenic pentafluoride (AsF 5 ) is very low, it generally exists in a gaseous state. Therefore, during the concentration, purification, and condensation of hydrofluoric acid, the temperature can be controlled between 4.0 - 15 °C. In this temperature range, arsenic pentafluoride (AsF 5 ) will not condense and exist in the purified hydrofluoric acid aqueous solution product due to the existence of the gas phase. Therefore, arsenic pentafluoride (AsF 5 ) in the gaseous state can be removed together with other gaseous substances at the backend of the treatment system by an air pollution control device. From the description of this step, it can be seen that adding an oxidant to the hydrofluoric acid waste liquid for oxidation treatment mainly serves to oxidize trivalent arsenic (As) compounds, such as arsenic trifluoride (AsF 3 ), to form pentavalent arsenic (As) compounds, such as arsenic pentafluoride (AsF 5 ). Because arsenic pentafluoride (AsF 5 ) exists in the gas phase, it will not condense and exist in the purified hydrofluoric acid (HF) aqueous solution product, and can be easily removed by an air pollution control device. Since the equipment and treatment method of the air pollution control device are not within the scope of the present invention, the step of using the air pollution control device to treat arsenic pentafluoride (AsF 5 ) will not be described in detail.

[0025] When the present invention conducts experiments on adding an oxidant to the hydrofluoric acid waste liquid for oxidation treatment, actual detections are also carried out, and the verification results are as follows: When detecting a general hydrofluoric acid waste liquid, it is known that the concentration of trivalent arsenic (As) in the general hydrofluoric acid waste liquid is between 10 - 120 ppm. After oxidation treatment with an oxidant (ozone 15 - 180

[0026] ppm) for 3.0 - 10 minutes, in the recovered hydrofluoric acid product, the hydrofluoric acid content is between 45% - 60% (between 40% - 55% when calculated including moisture), and at the same time, the contents of both trivalent arsenic (As) and pentavalent arsenic (As) in the hydrofluoric acid product are lower than the detection limit of the instrument (i.e., not detectable), and at the same time, in the recovered hydrofluoric acid product, the total sum of impurities is lower than 12 - 23 ppb. It is obvious that the effect of adding an oxidant to the hydrofluoric acid waste liquid for oxidation treatment is excellent.

[0027] II. Adding fluorine-containing salts to the hydrofluoric acid waste liquid for treatment:

[0028] When evaporating, concentrating and purifying hydrofluoric acid waste liquid, there is a problem that nitric acid (boiling point 83 °C), hydrochloric acid (boiling point 57 °C) or aqueous sulfuric acid (boiling point 50 - 108 °C) often exists in the hydrofluoric acid waste liquid. Generally, when distilling the hydrofluoric acid waste liquid, the operating temperature is between 20 °C and 120 °C. Therefore, nitric acid (boiling point 83 °C), hydrochloric acid (boiling point 57 °C) and aqueous sulfuric acid (boiling point 50 - 108 °C) will azeotrope and condense together with the hydrofluoric acid waste liquid, and exist in the aqueous solution product after purification of the hydrofluoric acid waste liquid. In other words, during the process of evaporating, concentrating and purifying the hydrofluoric acid waste liquid, nitric acid, hydrochloric acid and sulfuric acid cannot be separated obviously. For this, the present invention has been developed through experimental verification. Fluoride salts can be added to the hydrofluoric acid waste liquid, such as potassium fluoride, sodium fluoride, magnesium fluoride and other fluoride salts. When fluoride salts are added to the hydrofluoric acid waste liquid, the hydrogen ions contained in nitric acid, hydrochloric acid and aqueous sulfuric acid in the hydrofluoric acid waste liquid will form hydrogen fluoride (HF) with fluoride ions. Therefore, the output of hydrofluoric acid in the purified hydrofluoric acid aqueous solution product is increased. In the process, the hydrogen ions in cheaper nitric acid, hydrochloric acid and / or sulfuric acid are converted into expensive hydrofluoric acid, which has greatly improved the economic benefits. When adding potassium fluoride, sodium fluoride, magnesium fluoride and other fluoride salts to the hydrofluoric acid waste liquid, the addition amount is calculated based on the total hydrogen ion concentration value in nitric acid, hydrochloric acid and aqueous sulfuric acid in the hydrofluoric acid waste liquid. After calculating the reaction equivalent value of fluoride ions, 30% - 80% is added, and this is used as the actual addition amount for treating the hydrofluoric acid waste liquid by adding fluoride salts.

[0029] When conducting experiments on treating the hydrofluoric acid waste liquid by adding fluoride salts in the present invention, actual detections were also carried out simultaneously, and the verification results are as follows: Before treatment, the concentration of hydrofluoric acid in the waste liquid was between 15% - 38%, the concentration of nitric acid (HNO 3 ) was between 1.5% - 10%, the concentration of hydrochloric acid (HCl) was between 2.0% - 11%, and the concentration of sulfuric acid (H 2 SO 4 ) was between 3.0% - 13%; 1.0 mole (i.e., 58 grams) of potassium fluoride (KF) was added during treatment; then in the recovered hydrofluoric acid product after treatment, the content of hydrofluoric acid was between 45% - 60% (with the moisture content between nearly 40% - 55%), and the total sum of impurities in the recovered hydrofluoric acid product was less than 12 - 23 ppb. Obviously, the effect of treating the hydrofluoric acid waste liquid by adding fluoride salts is excellent.

[0030] III. Add a gas lift pipe to inject gas into the distillation barrel of the hydrofluoric acid waste liquid for gas lift treatment:

[0031] As mentioned above, when the hydrofluoric acid waste liquid is evaporated, concentrated and purified by simple distillation operation, the operating temperature is between 20°C and 120°C, and the purification efficiency needs to be improved. In response to this, the present invention has been developed through experimental verification. During the distillation of the hydrofluoric acid waste liquid, a stripping tube is added to the hydrofluoric acid waste liquid distillation barrel. The stripping tube first extends vertically downward to form a vertical stripping tube part, and then bends at the bottom at an angle to form a non-vertical stripping tube part. The non-vertical stripping tube part can also partially protrude above the liquid surface. The bent angle can be horizontal (i.e., 0°) or within 30° above and below the horizontal (i.e., ±30°). The inner diameter of the vertical stripping tube part is between 1.0 cm and 2.5 cm. The gas used for stripping can be purified air, nitrogen or argon. The temperature of the gas used for stripping is between 20°C and 120°C. The outlet of the non-vertical stripping tube part is placed at the bottom of the hydrofluoric acid waste liquid distillation barrel and can also partially protrude above the liquid surface. The inner diameter of the non-vertical stripping tube part is between 0.5 and 1.5 cm. The outer interval of the non-vertical stripping tube part is between 2.0 and 4.0 cm. The opening of the non-vertical stripping tube part is located on the upper side or the side. The opening of the non-vertical stripping tube part is circular. The interval between the opening of the non-vertical stripping tube part and the opening edge is between 2.0 and 4.0 cm. The outlet flow rate of the added gas at the opening of the non-vertical stripping tube part is between 0.3 and 1.5 m / s to increase the amount of recovered hydrofluoric acid. Through experiments, the present invention has found that at the same temperature, adding the stripping tube for stripping and then heating can increase the efficiency of recovering hydrofluoric acid by 50% to 200% compared with simple heating.

[0032] IV. Heating the distillation barrel of the hydrofluoric acid waste liquid:

[0033] After the hydrofluoric acid waste liquid has undergone the above steps of oxidation treatment by adding an oxidant, treatment by adding a fluorine-containing salt, and stripping treatment by adding a stripping tube and injecting gas into the distillation barrel of the hydrofluoric acid waste liquid, the distillation barrel of the hydrofluoric acid waste liquid is further heated so that the temperature is between 20°C and 120°C, which can significantly increase the purification and recovery efficiency of hydrofluoric acid.

[0034] The innovative technology developed by the present invention lies in the process of recovering and treating the hydrofluoric acid waste liquid, allowing the hydrofluoric acid waste liquid to undergo four steps: oxidation treatment by adding an oxidant, treatment by adding a fluorine-containing salt, stripping treatment by adding a stripping tube and injecting gas, and heating and distillation treatment, so as to improve the purification and recovery efficiency of hydrofluoric acid. The present invention can concentrate and purify the concentration of hydrofluoric acid to more than 50%, and reduce the impurities in the hydrofluoric acid solution to less than 30 ppb. The recovered hydrofluoric acid can be used in high-tech industrial processes.

[0035] In addition to directly treating hydrofluoric acid waste liquid, the present invention can also treat the hydrofluoric acid waste liquid mentioned in the background technology by adding an aluminum-containing compound to convert it into sodium hexafluoroaluminate (Na 3 AlF 6 ) as cryolite, or adding silicon and sodium to the hydrofluoric acid waste liquid to form sodium hexafluorosilicate (Na 2 SiF 6 ) (sodium silicate), or adding iron to the hydrofluoric acid waste liquid to form iron(III) fluoride trihydrate (FeF 3 ﹒3H 2 O). The present invention can also treat these products generated. The present invention can treat solid or semi-solid waste containing sodium hexafluoroaluminate (Na 3 AlF 6 ) (cryolite), sodium hexafluorosilicate (Na 2 SiF 6 ) (sodium silicate) and iron(III) fluoride trihydrate (FeF 3 ﹒3H 2 O). After adding an acid (sulfuric acid, hydrochloric acid, phosphoric acid and nitric acid), the pH value of the solution is adjusted to below 2.0, and then left standing for 3.0 - 5.0 minutes to dissolve the fluorine in the waste, forming hydrofluoric acid dissolved in the aqueous solution. Then, the aqueous solution in which hydrofluoric acid is dissolved is pumped into a hydrofluoric acid distillation barrel, and then, according to the above steps developed by the present invention, four steps of oxidation treatment by adding an oxidant, treatment by adding a fluorine-containing salt, stripping treatment by injecting a gas into a stripping tube and heating and distillation treatment are carried out in the hydrofluoric acid waste liquid to recover the expensive hydrofluoric acid product.

[0036] The present invention mainly performs four steps on the hydrofluoric acid waste liquid, namely oxidation treatment by adding an oxidant, treatment by adding a fluorine-containing salt, stripping treatment by injecting a gas into a stripping tube and heating and distillation treatment. Among them, for the hydrofluoric acid distillate after heating and distillation treatment, hydrofluoric acid can be recovered through a condenser, and its condensation temperature is between 0°C and 65°C. Subsequently, several recovery bottles are connected in series, and an absorbent needs to be added to each recovery bottle. Moreover, the recovery bottles are all in an ice-water bath and the temperature is set between 0°C and 65°C to improve the recovery rate of hydrofluoric acid. The aforementioned absorbent is hydrofluoric acid of any concentration, and 35% - 48% hydrofluoric acid is added as the absorbent to the first recovery bottle, and 10% - 30% hydrofluoric acid is added as the absorbent to the second recovery bottle.

[0037] The method for concentrating and purifying the hydrofluoric acid waste liquid of the present invention can connect several distillation bottles in series for continuous fractional distillation, and then carry out subsequent collection with recovery bottles. In this way, hydrofluoric acid with higher purity and lower impurity concentration can be recovered. Of course, several recovery bottles can still be connected in series after several distillation bottles. The above-mentioned recovery bottles can also be heated, and the temperature is set between 20°C and 120°C. In this way, fractional distillation is carried out using the recovery bottles to recover hydrofluoric acid with higher purity and lower impurity concentration.

[0038] In the process of treating the concentrated purification method of hydrofluoric acid waste liquid of the present invention, the materials or linings of all pipelines and containers in contact with hydrofluoric acid need to use polytetrafluoroethylene (PTFE) or perfluoroalkoxy alkane (PFA) materials.

Claims

1. A method for concentrating and purifying hydrofluoric acid waste liquid, which comprises four steps: adding an oxidant to the hydrofluoric acid waste liquid for oxidation treatment, adding a fluorine-containing salt to the hydrofluoric acid waste liquid for treatment, adding a stripping tube to the distillation barrel of the hydrofluoric acid waste liquid, and heating the distillation barrel of the hydrofluoric acid waste liquid. Among them: When adding an oxidant to the hydrofluoric acid waste liquid for oxidation treatment, the oxidant used is: potassium permanganate, potassium dichromate, hydrogen peroxide or ozone. In operation, when adding an oxidant to the hydrofluoric acid waste liquid, the trivalent arsenic compound contained in the hydrofluoric acid waste liquid is oxidized by the above oxidant to form a pentavalent arsenic compound. This pentavalent arsenic compound exists in the gas phase and will not condense in the purified hydrofluoric acid aqueous solution product. Therefore, it is removed by an air pollution control device at the back end. When adding a fluorine-containing salt to the hydrofluoric acid waste liquid for treatment, the fluorine-containing salt used is: fluorinated salts such as potassium fluoride, sodium fluoride, magnesium fluoride, etc. In operation, when adding a fluorine-containing salt to the hydrofluoric acid waste liquid, the hydrogen ions contained in nitric acid, hydrochloric acid and aqueous sulfuric acid in the hydrofluoric acid waste liquid will form hydrogen fluoride with fluoride ions, increasing the yield of hydrofluoric acid in the purified hydrofluoric acid aqueous solution product. When adding a stripping tube to the distillation barrel of the hydrofluoric acid waste liquid, the stripping tube first goes vertically downward to form a vertical stripping tube part, and then bends at an angle at the bottom to form a non-vertical stripping tube part. The non-vertical stripping tube part can also be partially exposed above the liquid surface. The bent angle can be horizontal (i.e., 0°) or within 30° (i.e., ±30°) up and down from the horizontal. The inner diameter of the vertical stripping tube part is between 1.0 cm and 2.5 cm. The gas used for stripping is purified air, nitrogen or argon. The temperature of the gas used for stripping is between 20°C and 120°C. The outlet of the non-vertical stripping tube part is placed at the bottom of the distillation barrel of the hydrofluoric acid waste liquid. The inner diameter of the non-vertical stripping tube part is between 0.5 and 1.5 cm. The external interval of the non-vertical stripping tube part is between 2.0 and 4.0 cm. The opening of the non-vertical stripping tube part is at the upper or side position. The opening of the non-vertical stripping tube part is circular. The interval between the opening of the non-vertical stripping tube part and the opening edge is between 2.0 and 4.0 cm. The outlet flow rate of the added gas at the opening of the non-vertical stripping tube part is between 0.3 and 1.5 m / s, so as to increase the amount of recovered hydrofluoric acid; at the same temperature, adding the stripping tube for stripping and then heating, compared with simply heating, the efficiency improvement degree in the amount of recovered hydrofluoric acid is between 50% and 200%. Performing a heating operation on the distillation barrel of the hydrofluoric acid waste liquid so that the temperature is between 20°C and 120°C, increasing the purification and recovery efficiency of hydrofluoric acid.

2. The method for concentrating and purifying hydrofluoric acid waste liquid according to claim 1, characterized in that: When adding an oxidant to the hydrofluoric acid waste liquid for oxidation treatment, the addition amount of the oxidant is calculated as the chemical equivalent value of the required oxidant addition based on the concentration of the trivalent arsenic (As) compound, and then an additional 50% - 250% is added as the actual operation addition amount.

3. The method for concentrating and purifying hydrofluoric acid waste liquid according to claim 1, characterized in that: When treating by adding fluorine-containing salts to hydrofluoric acid waste liquid, the addition amount of the fluorine-containing salts is calculated based on the total hydrogen ion concentration value of nitric acid, hydrochloric acid and aqueous sulfuric acid in the hydrofluoric acid waste liquid to obtain the reaction equivalent value of fluoride ions, and then 30% - 80% is added as the actual addition amount.

4. The method for concentrating and purifying hydrofluoric acid waste liquid according to claim 1, characterized in that: Solid or semi-solid waste of sodium hexafluoroaluminate, sodium hexafluorosilicate or iron(III) fluoride trihydrate is subjected to an acid addition step to adjust the pH value of the solution to below 2.0, and then left standing for 1.0 - 5.0 minutes to dissolve the fluorine in the waste, forming hydrofluoric acid dissolved in the aqueous solution. Then, the aqueous solution in which hydrofluoric acid is dissolved is pumped into a distillation barrel for hydrofluoric acid, and then oxidized by adding an oxidant, treated by adding fluorine-containing salts, subjected to gas stripping by injecting gas, and heated and distilled in four steps to recover hydrofluoric acid products.

5. The method for concentrating and purifying hydrofluoric acid waste liquid according to claim 1, characterized in that: The hydrofluoric acid distillate after heated distillation treatment is condensed through a condenser with a temperature between 0°C and 65°C, and several recovery bottles are connected in series subsequently. An absorbent is added to each recovery bottle, and the recovery bottles are in an ice bath at 0°C - 65°C to improve the recovery rate of hydrofluoric acid.

6. The method for concentrating and purifying hydrofluoric acid waste liquid according to claim 5, characterized in that: Several distillation bottles are connected in series for continuous fractional distillation, and then the subsequent recovery bottles are used for collection to recover hydrofluoric acid with higher purity and lower impurity concentration.

7. The method for concentrating and purifying hydrofluoric acid waste liquid according to claim 5, characterized in that: The absorbent is an aqueous solution of hydrofluoric acid, and 35% - 48% hydrofluoric acid is added as the absorbent to the first recovery bottle, and 10% - 30% hydrofluoric acid is added as the absorbent to the second recovery bottle.

8. The method for concentrating and purifying hydrofluoric acid waste liquid according to any one of claims 1 - 7, characterized in that: During the treatment process, the materials or linings of all pipelines and containers in contact with hydrofluoric acid need to use polytetrafluoroethylene (PTFE) or perfluoroalkoxy alkane (PFA) materials.

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