CN103373708A - Treatment method for recovery and reuse of hydrofluoric acid waste liquid - Google Patents

Abstract

A hydrofluoric acid waste liquid recovery and reuse processing method, said method comprises analyzing the silicon content in the hydrofluoric acid waste liquid at first, add greater than the compound of sodium, potassium or barium of more than one times of the numerical value of silicon content into hydrofluoric acid waste liquid in the treatment tank, make fluorine and silicon in the hydrofluoric acid waste liquid combine with sodium, potassium or barium to react and produce the fluosilicate solid of sodium fluosilicate, potassium fluosilicate or barium fluosilicate, after waiting for the fluosilicate solid to subside, withdraw the upper strata liquid and add high-concentration hydrofluoric acid to make it accord with the hydrofluoric acid concentration value that the original process used, can be transported back to the original process and used; the hydrofluoric acid waste liquid can be used for preparing reusable hydrofluoric acid only by adding a small amount of sodium, potassium or barium ions, a large amount of chemical agents are not needed, the discharge amount of waste water is greatly reduced, the consumption amount of hydrofluoric acid in the original manufacturing process and the expenditure of additional purchase cost can be saved, and further the treatment steps are simplified, the treatment cost is reduced, and the environment-friendly benefit is achieved.

Description

Treatment method for recovery and reuse of hydrofluoric acid waste liquid

technical field

The invention relates to a treatment method for recycling and reusing hydrofluoric acid waste liquid, in particular to a method that can recycle hydrofluoric acid in hydrofluoric acid waste liquid and reuse it in the etching process, which has the advantages of saving the original etching process The purchase cost of hydrofluoric acid usage is low, and the processing volume is large, fast and easy, and it has multiple functions such as avoiding high heat to cause fire and producing thick smoke of hydrofluoric acid to harm the human body. the

Background technique

With the vigorous development of industries such as semiconductors, liquid crystal panels, and solar cells, the use of hydrofluoric acid (Hydrofluoric Acid; HF (aq)) in the production process to etch silicon and silicon compounds will also increase. After hydrofluoric acid etches silicon or silicon compounds, the amount of silicon-containing hydrofluoric acid waste liquid also increases; due to the high silicon content in hydrofluoric acid waste liquid, not only the etching ability of hydrofluoric acid is reduced, but also It will cause protrusions on the surface of the etched object, which will affect the accuracy of etching, and lead to a decrease in product quality and an increase in the time spent on etching. Therefore, the silicon-containing hydrofluoric acid waste liquid cannot be reused again, and when the hydrofluoric acid contains When the silicon content in the silicon reaches a predetermined value (generally about 10000ppm or more), it can no longer be used, and a hydrofluoric acid waste liquid is formed. the

Moreover, some industries use hydrofluoric acid in the form of mixed acids, such as hydrofluoric acid plus nitric acid to etch the silicon of solar panels, or hydrofluoric acid plus nitric acid and hydrochloric acid to etch glass plates, or hydrofluoric acid plus hydrochloric acid to form Etching solution, so just can cause in general hydrofluoric acid waste liquid not only containing the silicon of about 2～10% hydrogen fluoride and concentration slightly less than 1% (10000ppm), and simultaneously contain the nitric acid of 1～3% or contain about 5% As a result of hydrochloric acid, however, whether it is mixed acid hydrofluoric acid or pure hydrofluoric acid, when it is used as hydrofluoric acid waste liquid, the hydrofluoric acid contained in it is highly corrosive and highly fat-soluble. Not only will it cause serious burns to the skin of the human body, but it can also easily pass through the human body and combine with calcium and magnesium ions in the body to erode bones and muscles. It will be fatal. In addition, the discharge of hydrofluoric acid waste liquid into the nature will also destroy the balance of the ecosystem. Therefore, hydrofluoric acid waste liquid must be treated before it can be discharged to avoid harming the human body and polluting the environment. the

In the prior art, the treatment methods for hydrofluoric acid waste liquid are to extract the fluorine in the hydrofluoric acid waste liquid to make various fluorine chemicals. There are three main treatment methods as follows: 

1. The first method, as disclosed in China Taiwan Invention No. I233158, is to add calcium chloride to hydrofluoric acid waste liquid, so that calcium ions convert fluorine ions into calcium fluoride, and let fluoride ions interact with calcium ions Calcium fluoride sludge is generated to achieve the removal of fluorine in hydrofluoric acid waste liquid. The reaction formula is:

2HF(aq)+CaCl ₂ (aq)→CaF ₂ (s)+2HCl(aq)

Then, add liquid caustic soda (sodium hydroxide aqueous solution) to adjust the pH value of the waste liquid to neutrality (PH value is between 6 and 9), and its reaction formula is:

NaOH+HCl→NaCl+ _H2O

In addition, calcium hydroxide or calcium carbonate is added into the hydrofluoric acid waste liquid to neutralize the acid in the hydrofluoric acid waste liquid and remove fluorine ions. the

However, whether it is adding calcium chloride to the hydrofluoric acid waste liquid, and then using liquid caustic soda to adjust the pH value of the waste liquid to neutral, or adding calcium hydroxide or calcium carbonate to the hydrofluoric acid waste liquid, All can produce a large amount of sludge, take the hydrofluoric acid waste liquid of 1 kilogram concentration 49% as example, if use calcium chloride to process, will produce the calcium fluoride sludge of about 5 kilograms; If use calcium hydroxide process, will produce About 10 kg of calcium fluoride sludge, and the accompanying waste water is huge and must be treated before it can be discharged. At the same time, the amount of calcium fluoride sludge deposited is also very large, making the overall treatment cost extremely high, and calcium chloride , Calcium Hydroxide or Calcium Carbonate and other purchase expenses are also many, so it is not a good processing method, and it is also very unfavorable for the industry to adopt. the

2. The second method is to add sodium aluminate to hydrofluoric acid waste liquid to convert fluoride ions into sodium fluoroaluminate, by adding aluminum-containing compounds and sodium-containing compounds (usually adding sodium aluminate) to hydrofluoric acid In acid waste liquid, to generate non-dissolved sodium fluoroaluminate crystals (Na ₃ AlF ₆ ), the reaction formula is:

3Na ⁺ +Al ³⁺ +6F ^- →Na ₃ AlF ₆

However, the amount of waste water produced is quite large, and it must be treated before it can be discharged. The trade name of sodium fluoroaluminate is cryolite, which is mainly used as a high-temperature flux for electrolytic extraction of metal aluminum. Aluminum has good ductility, but excessive aluminum doping When the silicon compound is used, the ductility will be greatly reduced, so although this method can produce cryolite from hydrofluoric acid waste liquid, its use is limited and its value is low. In addition, the waste liquid produced after extracting cryolite has Acidic, still need to add liquid caustic soda for acid-base neutralization, because acid-base neutralization is an exothermic reaction, it is dangerous to the operator, and also need to use a heat exchanger to improve the processing speed, moreover, fluoroaluminum Sodium acid (cryolite) is a crystal, and its crystallization rate is slow, which will also lead to the inability to quickly process the waste liquid, so it is not a good treatment method. the

3. The third method is as disclosed in the Republic of China Invention Publication No. 200930663. It is to add hydrofluoric acid to the hydrofluoric acid waste liquid to adjust the hydrofluoric acid waste liquid to a certain concentration, and then add silicon and sodium. In the hydrofluoric acid waste liquid after adjusting the concentration, the fluorine ion is converted into sodium fluorosilicate, by adding excessive silicon-containing compound and sodium-containing compound (generally adding sodium silicate; trade name is water Glass) in hydrofluoric acid waste liquid to generate insoluble sodium fluorosilicate crystals (Na ₂ SiF ₆ ), and finally dry the sodium fluorosilicate crystals to achieve recovery of fluorine; therefore, its chemical agent The cost is high, and the amount of waste water produced is also extremely high, resulting in high waste water treatment costs. At the same time, the disadvantage of gelatinous substances will be produced during the treatment process, which will delay the formation of sodium fluorosilicate, and the influence of the gelatinous substances will also lead to Subsequent dehydration treatment is extremely difficult. Because water glass is an alkaline substance but hydrofluoric acid is an acidic substance, an exothermic acid-base neutralization reaction will be formed. Instead, a heat exchanger is needed to increase the processing speed, but because Hydrofluoric acid is corrosive to metals and can only be used with plastic heat exchangers with poor thermal conductivity, making it slow and not a good treatment.

The above three existing hydrofluoric acid waste liquid treatment methods also have a common shortcoming, which is limited to taking out the fluorine in the waste liquid to make cheap fluorine chemicals, which wastes the recovery and reuse of hydrofluoric acid. People aim at above-mentioned weak point, through a large amount of theoretical analysis and experiment, finally design the method of the present invention. the

Contents of the invention

The main purpose of the present invention is to provide a treatment method for reclaiming and reusing hydrofluoric acid waste liquid. The method first analyzes the content of silicon (Si) in the hydrofluoric acid (HF) waste liquid, and then more than double the value of the silicon content. The compound of sodium, potassium or barium is added into the hydrofluoric acid waste liquid in the treatment tank, and the fluorine and silicon in the hydrofluoric acid waste liquid are combined with sodium, potassium or barium to form sodium fluorosilicate (Na ₂ SiF ₆ (s)), potassium fluorosilicate (K ₂ SiF ₆ (s)) or barium fluorosilicate (BaSiF ₆ (s)) fluorosilicate solids, after the fluorosilicate solids settle, Then extract the supernatant and detect whether the hydrofluoric acid content of the supernatant is higher than the hydrofluoric acid concentration value used in the original process, if it is higher than the hydrofluoric acid concentration value used in the original process, it will be directly transported back to the original process for use; otherwise , then add high-concentration hydrofluoric acid to make it reach the concentration value of hydrofluoric acid used in the original process, and then transport it back to the original process for use.

At the same time, the fluorosilicate slurry settled at the bottom of the treatment tank is dehydrated and washed to obtain a fluorosilicate solid. the

The sodium compound added in the above step c is sodium fluoride or sodium chloride. the

The numerical value of the sodium ion in the sodium compound added in the above-mentioned steps c is 1.64 mass times of silicon content value. the

The potassium compound added in the above step c is potassium fluoride or potassium chloride. the

The value of the potassium ion in the potassium compound added in the above step c is 2.787 mass times of the silicon content value. the

The barium compound added in the above step c is barium fluoride or barium chloride. the

The value of barium ions in the barium compound added in the above step c is 4.889 times by mass of the silicon content. the

Since only a small amount of sodium, potassium or barium ions need to be added to the hydrofluoric acid waste liquid, reusable hydrofluoric acid can be produced without consuming a large amount of chemicals, greatly reducing the amount of waste water discharge, and saving raw materials. The amount of hydrofluoric acid used in the manufacturing process and the expenditure of additional purchase costs can simplify the processing steps, reduce processing costs, and have environmental protection benefits. the

A treatment method for recovering and reusing hydrofluoric acid waste liquid provided by the present invention, in the process of treating hydrofluoric acid waste liquid, no heat will be released due to no acid-base neutralization exothermic reaction, so only plastic The treatment tank made of high-quality materials is enough, and at the same time, it can avoid the high heat causing fire and the generation of hydrofluoric acid smoke that is harmful to the human body. It can not only achieve the purpose of reducing equipment costs, but also achieve the function of improving the safety of the working environment. the

The present invention provides a treatment method for recovering and reusing hydrofluoric acid waste liquid. Since the fluorosilicate produced in the process of hydrofluoric acid waste liquid treatment will not be disturbed by colloidal substances during the settlement process, the sedimentation The speed is fast and it is beneficial to achieve the effect of treating a large amount of hydrofluoric acid waste liquid. the

The present invention really has many advantages as follows after a large number of actual operation tests:

1. The present invention only needs to add a small amount of sodium, potassium or barium ions to produce reusable hydrofluoric acid, without consuming a large amount of chemicals, and without the problem of waste water discharge. In addition to reducing the cost of chemicals , and save the amount of hydrofluoric acid used in the original process. the

2. During the treatment process of the present invention, because no heat is released, only a treatment tank made of plastic material can be used for treatment, and it can avoid high heat to cause fire and produce thick smoke of hydrofluoric acid to harm the human body. the

3. In the process of the present invention, the fluorine of sodium fluorosilicate (Na ₂ SiF ₆ (s)), potassium fluorosilicate (K ₂ SiF ₆ (s)) or barium fluorosilicate (BaSiF ₆ (s)) After the silicate solids are generated, it is only necessary to wait for the fluorosilicate solids to settle, because the fluorosilicate particles settle at a rate of about 150-180 cm/hour, and the fluorosilicates will not be disturbed by colloids when they settle , Generally, it takes about 3 hours for the processing tank with a high liquid level of about 4 meters to complete the settlement, and the processing speed is fast.

Description of drawings

The accompanying drawings about the described embodiment are:

Fig. 1 is the flow block diagram of the processing method of hydrofluoric acid waste liquid recovery reuse of the present invention. the

Fig. 2 is a schematic diagram of the operation of the treatment method for recovering and reusing hydrofluoric acid waste liquid of the present invention. the

Reference logo:

1- hydrofluoric acid waste liquid; 2- sodium, potassium or barium compound; 3- fluorosilicate solid; 4- supernatant; 10- treatment tank; 20- recovery tank. the

Detailed ways

Describe the present invention in detail below in conjunction with accompanying drawing and embodiment, will further understand technical content of the present invention and purpose effect thereof;

Example 1

Please refer to Fig. 1 and shown in Fig. 2, the processing method of hydrofluoric acid waste liquid recovery reuse of the present invention, its step comprises:

A, hydrofluoric acid (HF) waste liquid 1 is diverted into treatment tank 10;

B, analyze the content of silicon (Si) in the hydrofluoric acid waste liquid 1 in the treatment tank 10, and draw described silicon content numerical value;

c. Add sodium compound 2 which is more than twice the value of silicon content into the hydrofluoric acid waste liquid 1 in the treatment tank 10, so that the fluorine and silicon in the hydrofluoric acid waste liquid 1 are combined with sodium to generate fluorosilicon Sodium acid solid (Na ₂ SiF ₆ (s))3;

d, waiting for the sodium fluorosilicate solid 3 to settle at the bottom of the treatment tank 10;

e, extract the supernatant 4 in the treatment tank 10 to the recovery tank 20;

f. Check whether the hydrofluoric acid content of the supernatant 4 in the recovery tank 20 is higher than the hydrofluoric acid concentration value used in the original process, if it is higher than the hydrofluoric acid concentration value used in the original process, the supernatant 4 is directly transported Go back to the original process and use; if it is lower than the hydrofluoric acid concentration value used in the original process, then add high-concentration hydrofluoric acid to make the upper layer liquid 4 reach the hydrofluoric acid concentration value used in the original process, and then add it Transport back to the original process for use;

g. The sodium fluorosilicate slurry settled at the bottom of the treatment tank 10 is dehydrated and washed to obtain the sodium fluorosilicate solid 3 . the

Wherein, in step b, because the silicon content of hydrofluoric acid waste liquid 1 is not fixed, so need to analyze the silicon content of hydrofluoric acid waste liquid 1 first, the silicon content in the hydrofluoric acid waste liquid 1 after the current industry etching process uses Between 1 and 2%. the

The sodium compound 2 added in step c is sodium fluoride or sodium chloride, and the optimal value of its sodium ion is 1.64 mass times of the silicon content value; if adding sodium fluoride (NaF), it will react to produce fluorine Sodium silicate precipitate and hydrofluoric acid, its reaction formula is:

2NaF+H ₂ SiF ₆ →Na ₂ SiF ₆ +2HF

The hydrofluoric acid of above-mentioned reaction output is identical with the hydrofluoric acid that originally existed in the hydrofluoric acid waste liquid 1, so can not change its composition and can be sent back to the original process for use. the

If sodium chloride (NaCl) is added, the reaction will produce sodium fluorosilicate precipitate and hydrochloric acid, the reaction formula is:

2NaCl(aq)+H ₂ SiF ₆ (aq)→Na ₂ SiF ₆ (s)+2HCl(aq)

The hydrochloric acid produced by the above reaction will mix with the hydrofluoric acid originally present in the hydrofluoric acid waste liquid 1 to form a mixed acid. Because the types of hydrofluoric acid used in different industrial etching processes include pure hydrofluoric acid or hydrofluoric acid mixed acid , so the mixed acid containing hydrochloric acid can still be completely applied to different industrial etching processes, and can be transported back to the original process for use. the

At present, in the etching process of the industry, hydrofluoric acid or hydrofluoric acid mixed acid with a concentration of 49% is used. The sodium compound 2 added in step c of the present invention; Fluorosilicic acid form) combined to generate sodium fluosilicate solid 3 which is slightly soluble in acid, the solubility of sodium fluosilicate in water is about 0.652% (at 17°C), at this time, the silicon in the solution is saturated The solubility is 0.0097%. According to LeChatelier's Principle, when a system in equilibrium is disturbed by external force, the system will adjust towards the direction of reducing the disturbance of external force and reach a new balance. Therefore, in fluorine In the sodium silicate system, increasing the fluorine concentration will reduce the solubility of silicon. In general hydrofluoric acid waste liquid, the fluorine concentration is between 20,000 and 200,000ppm, and the silicon concentration is about 10,000ppm. The fluorine concentration is higher than the silicon concentration. Add sodium ions Finally, the solubility of silicon in waste acid will be lower than that in water, and its solubility can be reduced to below 0.42ppm (estimated by solubility product, when the fluorine concentration is 5%, the solubility of silicon is 6.7ppm), so , the method of the present invention can remove more than 99% of the silicon in the hydrofluoric acid waste liquid 1, and the inventors have learned that the optimum amount of sodium ions added is 1.64 times by mass of the silicon content through the actual operation of the inventor. the

And the sodium fluorosilicate particle settling rate in the step d is about 150 centimeters/hour (cm/hour), and about 4 meters (m) high liquid level in the general treatment tank 10, takes time-consuming about 3 hours and just can settle down, Therefore as long as a treatment tank 10 containing 20 metric tons is set, the effect of processing 20 tons of hydrofluoric acid waste liquid 1 can be reached every 3 hours, and its processing speed is faster than all existing processing methods. the

The supernatant 4 in the treatment tank 10 in steps e and f is clean hydrofluoric acid without silicon. If the hydrofluoric acid content is low, it can be transported again after adding high-concentration hydrofluoric acid to make up the concentration. Returning to the original manufacturing process, thereby reducing the cost of purchasing additional hydrofluoric acid, relatively simultaneously greatly reducing the generation of hydrofluoric acid waste liquid l, and has environmental protection benefits. the

Furthermore, after the slurry at the bottom of the treatment tank 10 in step g is dehydrated and cleaned, sodium fluorosilicate can be obtained, and there is no large amount of water glass that needs to be added in the current processing method, so there will not be a large amount of fluorosilicate Therefore, the sedimentation rate of the sodium fluorosilicate will be faster than the existing method, and the subsequent treatments such as dehydration and cleaning are also easier and faster, so that the overall treatment cost will be reduced accordingly. significantly reduce. the

In addition, because there is no acid-base neutralization effect in each step of the present invention, no heat will be released during the treatment process, and the treatment tank 10 only needs to be made of plastic material, which can reduce the cost without using high-priced metal tanks. The cost of equipment can also avoid fires caused by high heat caused by process negligence, old equipment or equipment damage, and even hydrofluoric acid will be inhaled by the staff as the smoke drifts away, causing human injury or fatal dangers, which can further improve Overall work environment safety. the

Example 2

Please refer to Fig. 1 and shown in Fig. 2, the processing method of hydrofluoric acid waste liquid recovery reuse of the present invention, its step comprises:

A, hydrofluoric acid (HF) waste liquid 1 is diverted into treatment tank 10;

B, analyze the content of silicon (Si) in the hydrofluoric acid waste liquid 1 in the treatment tank 10, and draw described silicon content numerical value;

c. Add potassium compound 2, which is more than twice the value of silicon content, into the hydrofluoric acid waste liquid 1 in the treatment tank 10, so that the fluorine and silicon in the hydrofluoric acid waste liquid 1 are combined with potassium to generate fluorosilicon Potassium acid solid (K ₂ SiF ₆ (s))3;

d, waiting for the potassium fluorosilicate solid 3 to settle at the bottom of the treatment tank 10;

e, extract the supernatant 4 in the treatment tank 10 to the recovery tank 20;

f. Check whether the hydrofluoric acid content of the supernatant 4 in the recovery tank 20 is higher than the hydrofluoric acid concentration value used in the original process, if it is higher than the hydrofluoric acid concentration value used in the original process, the supernatant 4 is directly transported Return to the original process and use; if it is lower than the hydrofluoric acid concentration value used in the original process, then add high-concentration hydrofluoric acid to make the upper layer liquid 4 reach the hydrofluoric acid concentration value used in the original process, and then transport it back to the original process. Use of the original process;

G, the Potassium Fluosilicate slurry after the bottom of treatment tank 10 settles, obtain Potassium Fluosilicate solid 3 through dehydration, cleaning. the

Wherein, in the step b, because the silicon content of the hydrofluoric acid waste liquid 1 is not fixed, so the silicon content of the hydrofluoric acid waste liquid 1 needs to be analyzed first, and the silicon content in the hydrofluoric acid waste liquid 1 after the current industrial etching process is used Between 1 and 2%. the

The potassium compound 2 added in step c is potassium fluoride or potassium chloride, and the optimal value of its potassium ion is 2.787 mass times of the silicon content value; if adding potassium fluoride (KF), it will react to produce fluorine Potassium silicate precipitate and hydrofluoric acid, the reaction formula is:

2KF+H ₂ SiF ₆ →K ₂ SiF ₆ +2HF

The hydrofluoric acid of above-mentioned reaction output is identical with the hydrofluoric acid that originally existed in the hydrofluoric acid waste liquid 1, so can not change its composition and can be sent back to the original process for use. the

If potassium chloride (KCl) is added, the reaction will produce potassium fluorosilicate precipitate and hydrochloric acid, the reaction formula is:

2KCl(aq)+H ₂ SiF ₆ (aq)→K ₂ SiF ₆ (s)+2HCl(aq)

The hydrochloric acid produced by the above reaction will mix with the hydrofluoric acid originally present in the hydrofluoric acid waste liquid 1 to form a mixed acid. Because the types of hydrofluoric acid used in different industrial etching processes include pure hydrofluoric acid or hydrofluoric acid mixed acid , so the mixed acid containing hydrochloric acid can still be completely applied to different industrial etching processes, and can be transported back to the original process for use. the

At present, in the etching process of the industry, hydrofluoric acid or hydrofluoric acid mixed acid with a concentration of 49% is used. The potassium compound 2 added in the step c of the present invention will interact with the fluorine and silicon in the hydrofluoric acid waste liquid 1 (based on Fluorosilicic acid form) combined to generate and precipitate slightly acid-soluble potassium fluosilicate solid 3, the solubility of potassium fluosilicate in water is about 0.177gm/100ml (at 25°C), at this time, in the solution The saturation solubility of silicon is 0.022%. According to LeChatelier's Principle, when a system in equilibrium is disturbed by external force, the system will adjust towards the direction of reducing the external force disturbance, and reach a new balance. Therefore, in the potassium fluorosilicate system, increasing the fluorine concentration will reduce the solubility of silicon. Generally, in hydrofluoric acid waste liquid, the fluorine concentration is between 20,000 and 200,000 ppm, and the silicon concentration is about 10,000 ppm. The fluorine concentration is higher than the silicon concentration. After adding potassium ions, the solubility of silicon in waste acid will be lower than that in water, and its solubility can be reduced to below 0.0016ppm (estimated by solubility product, when the concentration of fluorine is 5%, the solubility of silicon is 0.026ppm ), therefore, the method of the present invention can remove more than 99% of the silicon in the hydrofluoric acid waste liquid 1, and know that the optimum addition amount of potassium ions is 2.787 mass times of the silicon content through the inventor's practical operation. the

And the sedimentation rate of potassium fluorosilicate particles in the step d is about 155 centimeters/hour (cm/hour), and the about 4 meters (m) high liquid level in the general treatment tank 10 will take about 3 hours to complete the sedimentation. Therefore, as long as a treatment tank 10 containing 20 metric tons is set, the effect of treating 20 tons of hydrofluoric acid waste liquid 1 can be reached every 3 hours, and its treatment speed is faster than all existing treatment methods. the

The supernatant 4 in the treatment tank 10 in steps e and f is clean hydrofluoric acid without silicon. If the hydrofluoric acid content is low, it can be transported again after adding high-concentration hydrofluoric acid to make up the concentration. Returning to the original manufacturing process, thereby reducing the cost of purchasing additional hydrofluoric acid, relatively simultaneously greatly reducing the generation of hydrofluoric acid waste liquid l, and has environmental protection benefits. the

Furthermore, after the slurry at the bottom of the treatment tank 10 in step g is dehydrated and cleaned, potassium fluorosilicate can be obtained, and there is no large amount of water glass that needs to be added in the current processing method, so there will not be a large amount of fluorosilicate Potassium output and the generation of jelly, therefore, the sedimentation speed of described potassium fluorosilicate also can be faster than existing method, simultaneously its subsequent treatment such as dehydration, cleaning is also easier and quicker, makes overall treatment cost with increasing significantly reduce. the

In addition, because there is no acid-base neutralization effect in each step of the present invention, no heat will be released during the treatment process, and the treatment tank 10 only needs to be made of plastic material, which can reduce the cost without using high-priced metal tanks. The cost of equipment can also avoid fires caused by high heat caused by process negligence, old equipment or equipment damage, and even hydrofluoric acid will be inhaled by the staff as the smoke drifts away, causing human injury or fatal dangers, which can further improve Overall work environment safety. the

Example 3

Please refer to Fig. 1 and shown in Fig. 2, the processing method of hydrofluoric acid waste liquid recovery reuse of the present invention, its step comprises:

A, hydrofluoric acid (HF) waste liquid 1 is diverted into treatment tank 10;

B, analyze the content of silicon (Si) in the hydrofluoric acid waste liquid 1 in the treatment tank 10, and draw described silicon content numerical value;

c. Add the barium compound 2 which is more than twice the silicon content value into the hydrofluoric acid waste liquid 1 in the treatment tank 10, so that the fluorine and silicon in the hydrofluoric acid waste liquid 1 are combined with barium to generate fluorosilicon Barium acid solid (BaSiF ₆ (s))3;

d, waiting for the barium fluorosilicate solid 3 to settle at the bottom of the treatment tank 10;

e, extract the supernatant 4 in the treatment tank 10 to the recovery tank 20;

f. Check whether the hydrofluoric acid content of the supernatant 4 in the recovery tank 20 is higher than the hydrofluoric acid concentration value used in the original process, if it is higher than the hydrofluoric acid concentration value used in the original process, the supernatant 4 is directly transported Return to the original process and use; if it is lower than the hydrofluoric acid concentration value used in the original process, then add high-concentration hydrofluoric acid to make the upper layer liquid 4 reach the hydrofluoric acid concentration value used in the original process, and then transport it back to the original process. Use of the original process;

g. The barium fluorosilicate slurry settled at the bottom of the treatment tank 10 is dehydrated and washed to obtain the barium fluorosilicate solid 3 . the

Wherein, in the step b, because the silicon content of the hydrofluoric acid waste liquid 1 is not fixed, so the silicon content of the hydrofluoric acid waste liquid 1 needs to be analyzed first, and the silicon content in the hydrofluoric acid waste liquid 1 after the current industrial etching process is used Between 1 and 2%. the

The barium compound 2 added in step c is barium fluoride or barium chloride, and the optimum value of its barium ion is 4.889 mass times of the silicon content value; if barium fluoride (BaF ₂ ) is added, the reaction will produce Barium fluorosilicate precipitate and hydrofluoric acid, its reaction formula is:

BaF ₂ +H ₂ SiF ₆ →BaSiF ₆ +2HF

The hydrofluoric acid of above-mentioned reaction output is identical with the hydrofluoric acid that originally existed in the hydrofluoric acid waste liquid 1, so can not change its composition and can be sent back to the original process for use. the

If barium chloride (BaCl ₂ ) is added, the reaction produces barium fluorosilicate precipitate and hydrochloric acid, the reaction formula is:

2BaCl ₂ (aq)+H ₂ SiF ₆ (aq)→BaSiF ₆ (s)+2HCl(aq)

The hydrochloric acid produced by the above reaction will mix with the hydrofluoric acid originally present in the hydrofluoric acid waste liquid 1 to form a mixed acid. Because the types of hydrofluoric acid used in different industrial etching processes include pure hydrofluoric acid or hydrofluoric acid mixed acid , so the mixed acid containing hydrochloric acid can still be completely applied to different industrial etching processes, and can be transported back to the original process for use. the

At present, in the etching process of the industry, hydrofluoric acid or hydrofluoric acid mixed acid with a concentration of 49% is used. The barium compound 2 added in the step c of the present invention; Fluorosilicic acid form) combined to generate barium fluorosilicate solid 3 which is slightly soluble in acid, and the solubility of barium fluorosilicate in water is about 0.177gm/100ml (at 25°C). The saturated solubility of silicon is 0.022%. According to LeChatelier's Principle, when a system in equilibrium is disturbed by external force, the system will adjust towards the direction of reducing the external force disturbance, and reach a new balance. Therefore, in the potassium fluorosilicate system, increasing the fluorine concentration will reduce the solubility of silicon. Generally, in hydrofluoric acid waste liquid, the fluorine concentration is between 20,000 and 200,000 ppm, and the silicon concentration is about 10,000 ppm. The fluorine concentration is higher than the silicon concentration. After adding barium ions, the solubility of silicon in waste acid will be lower than that in water, and its solubility can be reduced to below 3.62×10 ^-8 ppm (estimated by solubility product, when the concentration of fluorine is 5%, the solubility of silicon Solubility is 2.9 * 10 ^-7 ppm), therefore, the mode of the present invention can remove the silicon of more than 99% in the hydrofluoric acid waste liquid 1, know that barium ion optimal addition amount is 4.889% of silicon content through actual operation of the inventor Quality times.

And the sedimentation rate of the barium fluorosilicate particle in the step d is about 180 centimeters/hour (cm/hour), and about 4 meters (m) high liquid level in the general treatment tank 10, it takes about 3 hours to complete the sedimentation, Therefore, as long as a treatment tank 10 containing 20 metric tons is set, the effect of treating 20 tons of hydrofluoric acid waste liquid 1 can be reached every 3 hours, and its treatment speed is faster than all existing treatment methods. the

The supernatant 4 in the treatment tank 10 in steps e and f is clean hydrofluoric acid without silicon. If the hydrofluoric acid content is low, it can be transported again after adding high-concentration hydrofluoric acid to make up the concentration. Returning to the original manufacturing process, thereby reducing the cost of purchasing additional hydrofluoric acid, relatively simultaneously greatly reducing the generation of hydrofluoric acid waste liquid l, and has environmental protection benefits. the

Furthermore, after the slurry at the bottom of the treatment tank 10 in step g is dehydrated and cleaned, barium fluorosilicate can be obtained, and there is no large amount of water glass that needs to be added in the current processing method, so there will be no large amount of fluorosilicate Barium output and the generation of jelly, therefore, the settling speed of described barium fluorosilicate also can be faster than existing method, simultaneously its subsequent treatment such as dehydration, cleaning is also simpler and quicker, makes overall processing cost accordingly significantly reduce. the

In addition, because there is no acid-base neutralization effect in each step of the present invention, no heat will be released during the treatment process, and the treatment tank 10 only needs to be made of plastic material, which can reduce the cost without using high-priced metal tanks. The cost of equipment can also avoid fires caused by high heat caused by process negligence, old equipment or equipment damage, and even hydrofluoric acid will be inhaled by the staff as the smoke drifts away, causing human injury or fatal dangers, which can further improve Overall work environment safety. the

In summary, the present invention reuses hydrofluoric acid due to the recyclable hydrofluoric acid waste liquid, and its chemical dosage and waste water discharge are all reduced by 90% compared with the existing method, and the processing speed is fast and in the process It will not release heat and cause danger, and it is indeed highly industrially applicable and meets the patent requirements, so please file an application in accordance with the law. the

The above detailed description is a specific description of a feasible embodiment of the present invention, but the embodiment is not intended to limit the patent scope of the present invention, and any equivalent implementation or change that does not depart from the technical spirit of the present invention shall be Included in the patent scope of this case. the

To sum up, it is a preferred embodiment of the present invention, and it does not limit the scope of patent protection of the present invention. Therefore, reasonable changes made in the description and drawings of the present invention are all included in the scope of protection of the present invention. Together with Chen Ming. the

Claims (7)

1. a treatment method for hydrofluoric acid waste liquid recovery and reuse, is characterized in that: the method may further comprise the steps: A, guide described hydrofluoric acid waste liquid into treatment tank; b. analyzing the silicon content in the hydrofluoric acid waste liquid in the treatment tank and obtaining the silicon content value; c. Add a compound containing sodium, potassium or barium that is more than twice the value of the silicon content into the hydrofluoric acid waste liquid in the treatment tank, so that the fluorine in the hydrofluoric acid waste liquid And the silicon and the sodium, the potassium or the barium form a fluorosilicate solid of sodium fluorosilicate, potassium fluorosilicate or barium fluorosilicate; d. Waiting for the fluorosilicate solids to settle at the bottom of the treatment tank; e, extracting the supernatant in the treatment tank to the recovery tank; f. Detect whether the hydrofluoric acid content of the supernatant in the recovery tank is higher than the hydrofluoric acid concentration value used in the original process, if it is higher than the hydrofluoric acid concentration value used in the original process, directly The upper layer liquid is transported back to the original process for use, and if it is lower than the concentration of hydrofluoric acid used in the original process, then high-concentration hydrofluoric acid is added to make the upper layer liquid reach the concentration of hydrofluoric acid used in the original process After the value, it is sent back to the original process for use; g. The fluorosilicate slurry settled at the bottom of the treatment tank is dehydrated and washed to obtain a fluorosilicate solid. 2. according to the treatment method of hydrofluoric acid waste liquid recovery reuse described in claim 1, it is characterized in that: the sodium compound added in the step c is sodium fluoride or sodium chloride. 3. according to the treatment method of hydrofluoric acid waste liquid recovery reuse described in claim 1, it is characterized in that: the numerical value of the sodium ion in the sodium compound added in the step c is 1.64 mass times of silicon content value. 4. according to the treatment method of hydrofluoric acid waste liquid recovery reuse described in claim 1, it is characterized in that: the potassium compound added in the step c is potassium fluoride or potassium chloride. 5. according to the treatment method of hydrofluoric acid waste liquid recovery reuse described in claim 1, it is characterized in that: the numerical value of the potassium ion in the potassium compound added in the step c is 2.787 mass times of silicon content value. 6. According to the treatment method for recovering and reusing hydrofluoric acid waste liquid according to claim 1, it is characterized in that: the barium compound added in the step c is barium fluoride or barium chloride. 7. The treatment method for reclaiming and reusing hydrofluoric acid waste liquid according to claim 1, characterized in that: the value of the barium ion in the barium compound added in step c is 4.889 mass times of the silicon content value.

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