TW201311574A - Treatment method for recycling and reusing hydrofluoric acid waste liquid (I) - Google Patents

Abstract

The present invention relates to a treatment method for recycling and reusing hydrofluoric acid waste liquid (I), including: analyzing the silicon content in hydrofluoric acid waste liquid; adding a sodium-containing compound whose quantity is more than two times of the silicon quantity into the hydrofluoric acid waste liquid in a processing tank to make fluorine and silicon in the hydrofluoric acid waste liquid and sodium carry out bonding reaction for producing sodium fluorosilicate solid; extracting supernatant after precipitating sodium fluorosilicate solid; and adding high concentration hydrofluoric acid solution to meet the concentration of hydrofluoric acid solution used in the original process, thereby allowing the hydrofluoric acid solution to be delivered back to original process for reuse. This treatment method can prepare reusable hydrofluoric acid by only adding a few sodium ions into the hydrofluoric acid waste liquid without consuming too much chemical agent, thereby greatly reducing discharge of waste water, saving the amount of hydrofluoric acid used in the original process and the expenditure of extra purchase cost, having simplified processing steps, lowering processing cost and having the effect of environmental protection.

Description

Treatment method for recycling and reuse of hydrofluoric acid waste liquid (1)

The present invention relates to a "treatment method for recycling and reusing a hydrofluoric acid waste liquid (1)", and more particularly to a method for recovering hydrofluoric acid in a hydrofluoric acid waste liquid and capable of being repeatedly used in an etching process. The utility model has the advantages of saving the purchase cost of the hydrofluoric acid used in the original etching process, and the processing amount is large, fast and simple, and avoids the multiple effects such as the high heat causing the fire to cause the hydrofluoric acid smoke to harm the human body.

With the booming industries such as semiconductors, liquid crystal panels, and solar cells, the use of hydrofluoric acid (HF _(aq) ) as an etching enthalpy and cerium compound in production processes will increase. The amount of hydrazine-containing hydrofluoric acid waste liquid produced by hydrofluoric acid etching of ruthenium or osmium compound is also accompanied by an increase; since the ruthenium content in the hydrofluoric acid waste liquid is high, not only the etching ability of hydrofluoric acid is lowered, but also It will cause protrusions on the surface of the etchant to affect the precision of the etching, and lead to a decrease in the yield of the product and an increase in the etching time. Therefore, the hydrofluoric acid waste liquid containing bismuth cannot be used again, and when hydrofluoric acid is used When the internal cerium content reaches a predetermined value (generally about 10,000 ppm or more), the hydrofluoric acid waste liquid is formed because it can no longer be used.

In addition, some industries use hydrofluoric acid in the form of mixed acid. For example, hydrofluoric acid is added with nitric acid to etch solar panels, or hydrofluoric acid is added with nitric acid and hydrochloric acid to etch glass plates, or hydrofluoric acid is added with hydrochloric acid. Forming an etchant, thus causing the general hydrofluoric acid waste liquid to contain not only about 2 to 10% of hydrogen fluoride and a concentration of slightly less than 1% (10000 ppm), but also containing 1 to 3% of nitric acid or about 5%. As a result of hydrochloric acid, however, whether it is a hydrofluoric acid or a pure hydrofluoric acid of a mixed acid type, when it is used as a waste liquid of hydrofluoric acid, the hydrofluoric acid contained therein is highly corrosive and highly fat-soluble. It not only causes severe burns on the skin of the human body, but also easily penetrates the human body and combines with calcium and magnesium ions in the body to erode bones and muscles. If inhaled by the vapor of hydrofluoric acid, it will cause pulmonary edema and excessive inhalation. It is fatal. In addition, the discharge of hydrofluoric acid waste into the natural world will also destroy the balance of the ecosystem. Therefore, the hydrofluoric acid waste liquid must be treated before it can be discharged to avoid harming the human body and polluting the environment.

In the prior art, the treatment method of the hydrofluoric acid waste liquid is to take out the fluorine in the hydrofluoric acid waste liquid to prepare various types of fluorine chemicals, and the main treatment methods are as follows:

1. The first method, as disclosed in the Republic of China Invention No. I233158, is to add calcium chloride to a hydrofluoric acid waste liquid, so that calcium ions convert fluoride ions into calcium fluoride and allow fluoride ions and calcium ions to act. The calcium fluoride sludge is produced to achieve the removal of the fluorine component in the hydrofluoric acid waste liquid, and the reaction formula is:

Then, adding liquid alkali (aqueous sodium hydroxide solution) to adjust the pH value of the waste liquid to neutral (pH value is 6-9), and the reaction formula is:

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

However, whether it is the addition of calcium chloride in the waste water of the hydrofluoric acid solution, the pH of the waste liquid is adjusted to neutral by the liquid alkali, or the method of adding calcium hydroxide or calcium carbonate to the waste liquid of the hydrofluoric acid, A large amount of sludge will be produced. For example, a 1 kg concentration of 49% hydrofluoric acid waste liquid will produce about 5 kg of calcium fluoride sludge if treated with calcium chloride. If calcium hydroxide is used, it will be produced. About 10 kg of calcium fluoride sludge, and the amount of wastewater generated is extremely large and must be treated before it can be discharged. At the same time, the amount of calcium fluoride sludge deposited is also extremely high, making the overall treatment cost extremely high, and calcium chloride, There are also many purchase expenses such as calcium hydroxide or calcium carbonate, so it is not a good treatment method and is not very suitable for industrial use.

Second, the second method is to add sodium aluminate in the hydrofluoric acid waste liquid, convert the fluoride ion into sodium fluoroaluminate, and add the aluminum-containing compound and the sodium-containing compound (generally adding sodium aluminate) to the hydrofluoric acid. In the waste liquid, to form a non-dissolved sodium fluoroaluminate crystal (Na ₃ AlF ₆ ), the reaction formula is:

However, the amount of waste water produced is quite large and must be treated before it can be discharged. The product of sodium fluoroaluminate is called cryolite, which is mainly used as a high-temperature flux for refining metal aluminum by electrolysis. Aluminum has good ductility, but aluminum is excessively doped. Although the ductility of the compound is greatly reduced, the method can produce cryolite from the hydrofluoric acid waste liquid, but its use is limited and the value is low. In addition, the waste liquid produced after extracting the cryolite has Acidity, still need to add liquid alkali for acid-base neutralization, because the acid-base neutralization is an exothermic reaction, it has certain danger to the operator, and the heat exchanger is needed to increase the processing speed. Furthermore, the fluoroaluminate Sodium (cryolite) is a crystal, and its crystallization rate is slow, which also leads to the inability to process waste liquid quickly, so it is not a good treatment method.

Third, the third method is disclosed in the Republic of China Invention No. 200930663, which firstly adds hydrofluoric acid to the hydrofluoric acid waste liquid, adjusts the hydrofluoric acid waste liquid to a concentration, and then adds the sodium and sodium. In the hydrofluoric acid waste liquid having the adjusted concentration, the fluoride ion is converted into sodium fluoroantimonate, and the excess strontium-containing compound and the sodium-containing compound (generally sodium citrate added; the trade name is water glass) is added. In the hydrofluoric acid waste liquid, an undissolved sodium fluoroantimonate crystal (Na ₂ SiF ₆ ) is formed, and finally the sodium fluoroantimonate crystal is dried to obtain a fluorine recovery; therefore, the chemical agent is expensive. Moreover, the amount of waste water generated is extremely high, which leads to high waste water treatment costs, and at the same time, the disadvantage of gelation occurs during the treatment, which delays the formation rate of sodium fluoroantimonate, and the subsequent dehydration is also affected by the gum. The treatment is extremely difficult. Because the water glass is an alkaline substance, but the hydrofluoric acid is an acidic substance, an acid-base neutralization reaction with an exothermic heat is formed. Instead, a heat exchanger is required to increase the processing speed, but because of the hydrofluoric acid Metal corrosive Only using a differential thermal conductivity of the plastic material of the heat exchanger, so that it is also slow processing speed, but not a very good approach.

The above-mentioned three conventional methods for treating hydrofluoric acid waste liquids have a common deficiency, which are all limited to the removal of fluorine in the waste liquid into inexpensive fluorine chemicals, and waste the recycling of hydrofluoric acid. The inventors have In view of this, the method of the present invention can be finally designed through continuous trial and modification.

The main object of the present invention is to provide a "treatment method for recycling and reusing a hydrofluoric acid waste liquid (1)", which first analyzes the content of cerium (Si) in the hydrofluoric acid (HF) waste liquid, and then the content is greater than cerium content. A sodium compound having a value of more than one time is added to a hydrofluoric acid waste liquid in a treatment tank, and fluorine and strontium in the hydrofluoric acid waste liquid are combined with sodium to form a sodium fluorocarbonate solid (Na ₂ SiF _{6 ( s)} ), after waiting for the solid solution of sodium fluoroantimonate to settle, extract the upper layer liquid and check whether the hydrofluoric acid content of the upper layer liquid is higher than the concentration of hydrofluoric acid used in the original process, if it is higher than the hydrogen used in the original process The concentration of the hydrofluoric acid is directly transferred back to the original process; otherwise, the high concentration of hydrofluoric acid is added to the hydrofluoric acid concentration value used in the original process, and then returned to the original process for use.

Since only a small amount of sodium ions need to be added in the hydrofluoric acid waste liquid, the reusable hydrofluoric acid can be obtained without using a large amount of chemical agents, and the wastewater discharge amount is greatly reduced, and the hydrogen of the original process can be saved. The use of fluoric acid and its additional cost of purchase, in order to simplify the processing steps, reduce processing costs and have environmental benefits.

Another object of the present invention is to provide a "treatment method (1) for recycling and reusing a hydrofluoric acid waste liquid", which has no heat in the process of treating hydrofluoric acid waste liquid due to no exothermic reaction in acid and alkali. Release, so you only need to use the treatment tank made of plastic material, at the same time, it can avoid the high-heat-induced fire and cause the damage of the human body's hydrofluoric acid smoke, not only to reduce the cost of equipment, but also to improve the working environment. Sexual function.

Another object of the present invention is to provide a "treatment method for recycling and reuse of hydrofluoric acid waste liquid (1)", which is due to the reaction of hydrofluoric acid waste liquid during the treatment of sodium fluorophthalate, which is not waiting for sedimentation. It will be interfered by the gel, so the sedimentation speed is fast and it is beneficial to achieve the effect of processing a large amount of hydrofluoric acid waste liquid.

Please refer to the first and second figures, the "treatment method for recycling and reuse of hydrofluoric acid waste liquid (1)", and the steps thereof include:

a. Hydrofluoric acid (HF) waste liquid 1 is introduced into the treatment tank 10;

b. analyzing the content of cerium (Si) in the hydrofluoric acid waste liquid 1 in the treatment tank 10, and obtaining the cerium content value;

c. Adding sodium compound 2 which is more than twice the value of strontium content to the hydrofluoric acid waste liquid 1 in the treatment tank 10, and reacting fluorine and hydrazine in the hydrofluoric acid waste liquid 1 with sodium to form fluoroquinone Sodium solids (Na ₂ SiF _6(s) ) 3;

d. Waiting for the sodium fluoroantimonate solid 3 to settle at the bottom of the treatment tank 10;

e. The upper layer 4 in the treatment tank 10 is extracted to the recovery tank 20;

f. Detect whether the hydrofluoric acid content of the supernatant liquid 4 in the recovery tank 20 is higher than the hydrofluoric acid concentration value used in the original process, and if it is higher than the hydrofluoric acid concentration value used in the original process, the supernatant liquid 4 is directly sent back. If the temperature is lower than the concentration of hydrofluoric acid used in the original process, then the high concentration of hydrofluoric acid is added to make the upper layer 4 reach the concentration of hydrofluoric acid used in the original process, and then transport it back to the original process. Use; and

g. The sodium fluorosilicate slurry after sedimentation at the bottom of the treatment tank 10 is subjected to dehydration and washing to obtain sodium fluorosilicate solidate 3.

Wherein, in step b, since the content of the hydrofluoric acid waste liquid 1 is not fixed, it is necessary to first analyze the content of the hydrofluoric acid waste liquid 1 and the content of antimony in the hydrofluoric acid waste liquid 1 after the industrial etching process is used. Between 1 and 2%.

The sodium compound 2 added in the step c is sodium fluoride or sodium chloride, and the optimum value of the sodium ion is 1.64 times the value of the cerium content; if sodium fluoride (NaF) is added, the reaction will produce fluorine. Sodium citrate precipitate and hydrofluoric acid, the reaction formula is:

The hydrofluoric acid produced by the above reaction is the same as the hydrofluoric acid originally present in the hydrofluoric acid waste liquid 1, so that it can be returned to the original process without changing its composition.

If sodium chloride (NaCl) is added, the reaction produces sodium fluoroantimonate precipitate and hydrochloric acid, and the reaction formula is:

The hydrochloric acid produced by the above reaction is mixed with the hydrofluoric acid originally present in the hydrofluoric acid waste liquid 1 to form a mixed acid, and the hydrofluoric acid type used in different industrial etching processes includes pure hydrofluoric acid or hydrofluoric acid mixed acid. Therefore, the mixed acid containing hydrochloric acid can still be completely applied to the etching process of different industries, and can be transported back to the original process for use.

At present, in the industrial etching process, a mixed acid of hydrofluoric acid or hydrofluoric acid having a concentration of 49% is used, and the sodium compound 2 added in the step c of the present invention and the fluorine and hydrazine in the hydrofluoric acid waste liquid 1 The fluoroantimonic acid form is combined to form a sodium fluorosilicate sodium solid 3 which is slightly soluble in acid. The solubility of the sodium fluorophthalate in water is about 0.652% (at 17 ° C), at which time the hydrazine in the solution is saturated. The solubility is 0.0097%, and in the presence of sodium ions, the saturation solubility of ruthenium is reduced to 97 ppm. According to LeChatelier's Principle, when a system that is in equilibrium is disturbed by external forces, the system will reduce the external force. The direction of the disturbance is adjusted to achieve a new balance. Therefore, in the sodium fluoroantimonate system, increasing the fluorine concentration will reduce the solubility of the ruthenium. In the general hydrofluoric acid waste liquid, the fluorine concentration is between 20,000 and 200,000 ppm. About 10000ppm, the fluorine concentration is higher than the strontium concentration. After adding sodium ions, the solubility of hydrazine in the spent acid will be lower than that in water, and the solubility can be reduced to below 0.42ppm (estimated by solubility product, in fluorine concentration). When it is 5%, the solubility of bismuth is 6.7 ppm), therefore, the method of the present invention can remove more than 99% of the hydrazine in the hydrofluoric acid waste liquid 1, and the optimum amount of sodium ions added by the present inventors is 1.64 times the strontium content.

The sedimentation rate of the sodium fluorocarbonate particles in the step d is about 150 cm/hour, and the high liquid level of about 4 meters (m) in the general treatment tank 10 takes about 3 hours to settle. Therefore, as long as a treatment tank 10 containing 20 metric tons is provided, the treatment of 20 tons of hydrofluoric acid waste liquid 1 can be achieved every 3 hours, and the processing speed is faster than all current treatment methods.

Further, in step e and f, the upper liquid 4 in the treatment tank 10 is clean hydrofluoric acid containing no antimony. If the hydrofluoric acid content is low, the hydrofluoric acid is added to the high concentration to re-deliver. Returning to the original process, the cost of purchasing hydrofluoric acid is reduced, and the amount of hydrofluoric acid waste 1 is also reduced substantially simultaneously, and environmental benefits are also achieved.

Furthermore, in the step g, the slurry at the bottom of the treatment tank 10 is dehydrated and washed to obtain sodium fluoroantimonate, and there is no large amount of water glass to be added in the conventional treatment method, so there is no large amount of fluorine. The sodium citrate output and the production of the gel, therefore, the sedimentation rate of the sodium fluoroantimonate is faster than the conventional method, and the subsequent treatments such as dehydration and cleaning are also simpler and faster, so that the overall treatment cost is Greatly reduced.

In addition, in the various steps of the present invention, since there is no acid-base neutralization, no heat is released during the treatment, and the treatment tank 10 can be made only by using a plastic material, and can be reduced without using a high-priced metal tank. The cost of equipment can also avoid fires caused by high heat caused by process loss, old equipment or equipment damage. Even hydrofluoric acid can cause inhalation of workers with smoke, causing harm to human body or fatality. The security of the overall work environment.

After the actual operation of the invention, the invention has many advantages as follows:

1. The invention only needs to add a small amount of sodium ions to prepare a reusable hydrofluoric acid, which does not need to consume a large amount of chemical agents, and has no problem of waste water discharge, in addition to reducing the cost of chemical chemicals, Save the amount of hydrofluoric acid used in the original process.

2. In the process of the invention, since the heat is not released, only the processing tank made of plastic material can be used for treatment, and the high heat causes the fire to generate hydrofluoric acid smoke to harm the human body.

3. In the treatment process of the present invention, after the solid sodium fluorophthalate solid is produced, it is only necessary to wait for the solidification of the sodium fluorocarbonate solids, since the sedimentation rate of the sodium fluorocarbonate particles is about 150 cm/hr, and the sodium fluoroantimonate is precipitated. It will not be interfered by the rubber. Generally, the processing tank with a high liquid level of about 4 meters can be settled in about 3 hours, and the processing speed is fast.

In summary, the present invention re-uses hydrofluoric acid due to the recovery of hydrofluoric acid waste liquid, and its chemical dosage and wastewater discharge amount are reduced by 90% compared with the conventional method, and the processing speed is fast and In the process, heat will not be released, which will cause danger. It is highly industrially applicable and meets the requirements of patents.

1. . . Hydrofluoric acid waste liquid

2. . . Sodium compound

3. . . Sodium fluoroantimonate solid

4. . . Upper liquid

10. . . Processing tank

20. . . Recovery tank

First Figure: is a block diagram of the process of the present invention.

Second Figure: A schematic diagram of the operation of the present invention.

Claims (4)

A "treatment method for recycling and reusing a hydrofluoric acid waste liquid (1)", the steps comprising: a. introducing a hydrofluoric acid (HF) waste liquid into a treatment tank; b. analyzing the hydrofluoric acid waste liquid in the treatment tank The content of cerium (Si), and the value of the cerium content; c. The sodium compound which is more than twice the value of strontium content is added to the effluent of hydrofluoric acid in the treatment tank to make the effluent in the hydrofluoric acid waste liquid Fluorine and strontium react with sodium to form sodium fluoroclavate solids (Na ₂ SiF _6(s) ); d. wait for sodium fluoroantimonate solids to settle at the bottom of the treatment tank; e. extract the upper layer in the treatment tank The liquid is sent to the recovery tank; f. detecting whether the hydrofluoric acid content of the upper liquid in the recovery tank is higher than the concentration of hydrofluoric acid used in the original process, and if it is higher than the concentration of hydrofluoric acid used in the original process, the upper liquid is directly It is transported back to the original process; 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 supernatant liquid reach the concentration of hydrofluoric acid used in the original process, and then transport it back to the original The process is used; and g. the sodium fluorosilicate slurry after the bottom of the treatment tank is settled, and dehydrated and washed to obtain fluoroantimonic acid. Sodium solids. The "treatment method (1) for recycling and reusing a hydrofluoric acid waste liquid" as described in the first aspect of the patent application, wherein the sodium compound added in the step c is sodium fluoride. The "treatment method (1) for recycling and reusing a hydrofluoric acid waste liquid" as described in the first aspect of the patent application, wherein the sodium compound added in the step c is sodium chloride. In addition, the "treatment method for recycling and reuse of hydrofluoric acid waste liquid (1)" mentioned in the first, second or third paragraph of the patent application, wherein the sodium compound added in the step c has the optimum value of the sodium ion It is 1.64 times the value of the cerium content.