TW202444647A - Method for treating sulfuric acid waste containing hydrogen peroxide - Google Patents

Abstract

A method for treating sulfuric acid waste containing hydrogen peroxide begins by heating the sulfuric acid waste containing hydrogen peroxide to 50 DEG C to 90 DEG C for 1 to 2 hours to produce a sulfuric acid waste without hydrogen peroxide. Then, a calcium-containing material is added to the sulfuric acid waste without hydrogen peroxide to form a calcium sulfate solution containing calcium sulfate crystals. Next, the calcium sulfate solution is treated by a hydrothermal method to produce a calcium sulfate crystal solution containing dihydrate calcium sulfate crystals. Finally, the dihydrate calcium sulfate crystals are filtered out of the calcium sulfate crystal solution and washed and dried.

Description

Treatment method of sulfuric acid waste liquid containing hydrogen peroxide

The present invention relates to a method for treating waste sulfuric acid solution, and more particularly to a method for treating waste sulfuric acid solution containing hydrogen peroxide.

In recent years, as environmental awareness has risen, more and more factories have begun to build waste recycling systems. Most of the waste can be processed through classified recycling, but some high-tech factory waste is chemical substances that cannot be recycled through simple classification. For example, semiconductor factories, panel factories or PCB factories usually use sulfuric acid to clean machines or semiconductor semi-finished products, thus generating a large amount of sulfuric acid waste liquid.

In the existing technology, some manufacturers mix sulfuric acid waste liquid with ammonia nitrogen waste water to produce ammonium sulfate waste liquid, and then further purify the ammonium sulfate waste liquid into ammonium sulfate with economic value, thereby effectively reducing waste and converting waste into economically valuable materials.

As mentioned above, when some technology plants use sulfuric acid for cleaning operations, in order to completely decompose organic matter, hydrogen peroxide ( _H2O2 ) is usually added to sulfuric acid to form _a strong oxidant to decompose organic matter into _CO2 and _H2O . Therefore, the sulfuric acid waste liquid after cleaning often contains some hydrogen peroxide. In the sulfuric acid waste liquid recovery system, the presence of hydrogen peroxide will affect the recovery process of sulfuric acid waste liquid, and may even affect the quality of the final recovered product. Therefore, the existing sulfuric acid waste liquid recovery system will also treat hydrogen peroxide.

However, the existing sulfuric acid waste liquid recovery system has two ways to treat hydrogen peroxide, one is to add other reagents (such as ferrous sulfate or hydrochloric acid) to decompose hydrogen peroxide, the other is to use ultraviolet light to promote the decomposition of hydrogen peroxide, and the other is to use a centrifuge to pressurize the sulfuric acid waste liquid to promote the decomposition of hydrogen peroxide. However, these treatment methods still have some problems. For example, the addition of reagents will produce other products, and may even produce highly dangerous and highly toxic products. However, even non-toxic products need to be treated separately, which increases the complexity of the process and causes an increase in cost. The treatment methods of ultraviolet irradiation and centrifuges require the construction of additional machines and equipment, which will also greatly increase the cost of treating waste liquid.

In view of the fact that in the prior art, although the existing sulfuric acid waste liquid recovery system can decompose the hydrogen peroxide in the sulfuric acid waste liquid, it usually increases the cost of the entire recovery. When the overall recovery cost of the sulfuric acid waste liquid is greater than the economic value of the recovered product, it is very likely to affect the recycling willingness of the manufacturer, resulting in the difficulty in promoting the recovery and treatment of the sulfuric acid waste liquid, and then choosing a low-cost but highly polluting treatment method, which ultimately cannot achieve the purpose of environmental protection; therefore, the main purpose of the present invention is to provide a method for treating sulfuric acid waste liquid containing hydrogen peroxide, which can reduce the cost of treating hydrogen peroxide in sulfuric acid waste liquid and can also convert sulfuric acid waste liquid into a recyclable product with high economic value.

The present invention solves the problems of the prior art by adopting a necessary technical means to provide a method for treating sulfuric acid waste liquid containing hydrogen peroxide, comprising the following steps (A) to (D).

Step (A) is to heat a sulfuric acid waste liquid containing hydrogen peroxide to 50°C to 90°C for 1 to 2 hours, so that the hydrogen peroxide contained in the sulfuric acid waste liquid is decomposed into water and oxygen, thereby generating a hydrogen peroxide-free sulfuric acid waste liquid.

Step (B) is to add a calcium-containing raw material into the hydrogen peroxide-free sulfuric acid waste liquor, so that the calcium ions in the calcium-containing raw material react with the sulfate ions in the hydrogen peroxide-free sulfuric acid waste liquor to generate calcium sulfate crystals, thereby forming a calcium sulfate solution containing the calcium sulfate crystals.

Step (C) treating the calcium sulfate solution by a hydrothermal method to transform the calcium sulfate crystals into calcium sulfate dihydrate crystal whiskers, thereby forming a calcium sulfate crystal whisker solution containing the calcium sulfate dihydrate crystal whiskers.

Step (D): filtering the calcium sulfate dihydrate crystal whiskers from the calcium sulfate crystal whisker solution, and washing and drying the calcium sulfate dihydrate crystal whiskers.

In an auxiliary technical means derived from the above essential technical means, step (C) further includes the following steps (C1) and (C2). Step (C1) is to place the calcium sulfate solution and a crystal whisker growth promoter in a reactor, and use a sulfuric acid solution to control the pH value of the calcium sulfate solution between 3 and 4. Step (C2) is to control the temperature of the reactor between 150° C. and 180° C. and maintain it for 5 to 9 hours, so that the calcium sulfate crystals are transformed into the dihydrate calcium sulfate crystal whiskers.

In an auxiliary technical means derived from the above necessary technical means, step (D) further includes the following steps (D1) to (D4). Step (D1) is to filter the calcium sulfate crystal whisker solution containing the calcium sulfate dihydrate crystal whiskers to obtain the calcium sulfate dihydrate crystal whiskers. Step (D2) is to wash the calcium sulfate dihydrate crystal whiskers with clean water. Step (D3) is to dehydrate the calcium sulfate dihydrate crystal whiskers. Step (D4) is to control the environment of the calcium sulfate dihydrate crystal whiskers at a temperature of 70°C to 100°C for drying.

In an auxiliary technical means derived from the above essential technical means, a step (E) is further included after step (D), wherein the calcium sulfate dihydrate crystal whiskers are controlled at a temperature between 130° C. and 160° C. for 5 to 8 hours to transform the calcium sulfate dihydrate crystal whiskers into calcium sulfate hemihydrate crystal whiskers.

In an auxiliary technical means derived from the above essential technical means, a step (E) is further included after step (D), wherein the calcium sulfate dihydrate crystal whiskers are controlled at a temperature between 170° C. and 200° C. for 5 to 8 hours to transform the calcium sulfate dihydrate crystal whiskers into anhydrous calcium sulfate crystal whiskers.

As described above, the present invention mainly utilizes heating to decompose hydrogen peroxide in sulfuric acid waste liquor, then adds calcium-containing raw materials into hydrogen peroxide-free sulfuric acid waste liquor to form calcium sulfate solution, and then utilizes hydrothermal generation to crystallize calcium sulfate in the calcium sulfate solution to form dihydrate calcium sulfate crystal whiskers, and finally filters, washes and dries the dihydrate calcium sulfate crystal whiskers to obtain clean dihydrate calcium sulfate crystal whiskers; in addition, users can also selectively convert the dihydrate calcium sulfate crystal whiskers into hemihydrate calcium sulfate crystal whiskers or anhydrous calcium sulfate crystal whiskers through drying temperature and time.

The specific embodiments of the present invention will be further described by the following embodiments and drawings.

Please refer to the first figure, which is a flow chart showing the steps of the method for treating sulfuric acid waste liquid containing hydrogen peroxide provided by the first preferred embodiment of the present invention. As shown in the first figure, a method for treating sulfuric acid waste liquid containing hydrogen peroxide is used to treat a sulfuric acid waste liquid containing hydrogen peroxide, and the method for treating sulfuric acid waste liquid containing hydrogen peroxide includes the following steps S110 to S140.

First, step S110 is to heat the sulfuric acid waste liquid containing hydrogen peroxide to 50° C. to 90° C. and maintain it for 1 to 2 hours, thereby generating sulfuric acid waste liquid without hydrogen peroxide; wherein, the purpose of heating the sulfuric acid waste liquid containing hydrogen peroxide to 50° C. to 90° C. in step S110 is to accelerate the rate at which the hydrogen peroxide contained in the sulfuric acid waste liquid decomposes into water and oxygen because it is in a temperature environment higher than room temperature, and because the temperature is lower than 90° C., it is possible to avoid the violent decomposition of hydrogen peroxide and cause a large amount of sulfuric acid waste liquid to splash, and maintaining the temperature environment of 50° C. to 90° C. for 1 to 2 hours can ensure that the hydrogen peroxide is completely decomposed into water and oxygen.

Next, step S120 is to add a calcium-containing raw material to the hydrogen peroxide-free sulfuric acid waste solution to form a calcium sulfate solution containing calcium sulfate crystals; wherein, after the calcium-containing raw material is added to the hydrogen peroxide-free sulfuric acid waste solution, the calcium ions (Ca ²⁺ ) in the calcium-containing raw material react with the sulfate ions (SO ₄ ^2- ) in the hydrogen peroxide-free sulfuric acid waste solution to generate calcium sulfate crystals (CaSO ₄ ). The calcium-containing raw material is, for example, calcium carbonate, calcium oxide, calcium hydroxide, and calcium sulfate.

Then, step S130 is to treat the calcium sulfate solution by hydrothermal generation method to transform the calcium sulfate crystals into calcium sulfate dihydrate crystal whiskers (CaSO ₄ ·2H ₂ O), thereby forming a calcium sulfate crystal whisker solution containing calcium sulfate dihydrate crystal whiskers; wherein the hydrothermal generation method mainly controls the calcium sulfate solution at a specific temperature so that the calcium sulfate crystals in the calcium sulfate solution can continue to grow to form calcium sulfate dihydrate crystal whiskers in the form of crystal whiskers, and the calcium sulfate dihydrate crystal whiskers refer to calcium sulfate crystal whiskers with two crystal waters.

Finally, step S140 is to filter out the calcium sulfate crystal whiskers from the calcium sulfate crystal whisker solution, and wash and dry the calcium sulfate crystal whiskers. In step S130, the calcium sulfate crystal whisker solution in which the calcium sulfate crystal whiskers exist is transformed from the calcium sulfate solution, and the calcium sulfate solution is transformed from the sulfuric acid waste liquid without hydrogen peroxide in step S120. When calcium sulfate dihydrate crystal whiskers are formed in step S140, the calcium sulfate crystal whisker solution in which the calcium sulfate dihydrate crystal whiskers are located may still contain impurities contained in the original sulfuric acid waste liquid without hydrogen peroxide. Therefore, after the calcium sulfate dihydrate crystal whiskers are filtered out from the calcium sulfate crystal whisker solution, the calcium sulfate dihydrate crystal whiskers still need to be washed and dried to obtain clean calcium sulfate dihydrate crystal whiskers for further use.

Please continue to refer to the second figure, which is a detailed flow chart showing the detailed steps of treating the calcium sulfate solution by hydrothermal generation in the method for treating the sulfuric acid waste liquid containing hydrogen peroxide provided in the first preferred embodiment of the present invention. As shown in the first and second figures, step S130 in this embodiment further includes two detailed steps, namely step S131 and step S132.

Step S131 is to place a calcium sulfate solution and a hair growth promoter in a reaction vessel, and to control the pH value of the calcium sulfate solution to be between 3 and 4 using a sulfuric acid solution. Among them, in actual application, the sulfuric acid solution used to control the pH value of the calcium sulfate solution between 3 and 4 is a sulfuric acid solution with a pH value less than 3. For example, sulfuric acid with a concentration of 0.1 mol/L has a pH value of 1. The higher the concentration of sulfuric acid, the less amount is needed to adjust the pH value of the calcium sulfate solution. Since the source of the calcium sulfate solution is sulfuric acid waste liquid, and the pH value of the sulfuric acid waste liquid varies according to the method and location of use, when adjusting the pH value of the calcium sulfate solution, the amount of sulfuric acid solution used is determined according to the amount of the calcium sulfate solution and the concentration of the sulfuric acid solution. In practice, it is more likely that the sulfuric acid solution is added while the pH value of the calcium sulfate solution is measured until the pH value of the calcium sulfate solution is adjusted to between 3 and 4.

In addition, the beard growth promoters are compounds such as ammonium chloride (NH ₄ Cl), manganese chloride (MnCl ₂ ), copper sulfate (CuSO ₄ ), manganese sulfate (MnSO ₄ ) or magnesium chloride (MgCl ₂ ). The use of these beard growth promoters is often seen in the hydrothermal synthesis method. They are well known and flexibly used by technicians in this field, so they will not be elaborated here.

Next, step S132 is to control the temperature of the reactor between 150°C and 180°C and maintain it for 5 to 9 hours to transform the calcium sulfate crystals into calcium sulfate dihydrate crystal whiskers.

Please continue to refer to the third figure, which is a flow chart showing the detailed steps of filtering, washing and drying of calcium sulfate dihydrate crystal whiskers in the method for treating sulfuric acid waste liquid containing hydrogen peroxide provided in the first preferred embodiment of the present invention. As shown in the first and third figures, step S140 in this embodiment further includes four detailed steps, namely, step S141 to step S144.

Step S141 is to filter the calcium sulfate crystal whisker solution containing calcium sulfate dihydrate crystal whiskers to obtain calcium sulfate dihydrate crystal whiskers; wherein the filtering method can be to use filter paper or filter membrane for filtering, and even to cooperate with centrifugal equipment to accelerate the filtering.

Step S142 is to wash the calcium sulfate dihydrate crystal whiskers with clean water; wherein the clean water is deionized water or pure water.

Step S143 is to dehydrate the calcium sulfate dihydrate crystal whiskers; wherein the dehydration treatment is, for example, drying and dehydration using a centrifugal dehydrator.

Step S144 is to control the environment of the calcium sulfate dihydrate crystal whiskers to be dried at a temperature of 70°C to 100°C; wherein the calcium sulfate dihydrate crystal whiskers are placed in an oven for drying, and the temperature of the oven is set between 70°C and 100°C, but not limited thereto, and can also be dried by blowing hot air at 70°C to 100°C.

Please continue to refer to the fourth figure, which is a flow chart showing the steps of the method for treating sulfuric acid waste liquid containing hydrogen peroxide provided by the second preferred embodiment of the present invention. As shown in the first and fourth figures, the method for treating sulfuric acid waste liquid containing hydrogen peroxide of this embodiment includes the following steps S210 to S250; wherein, steps S210 to S240 are the same as the above-mentioned steps S110 to S140, so no further description is given here.

After step S240, step S250 is to control the calcium sulfate dihydrate crystal whiskers at a temperature between 130° C. and 160° C. for 5 to 8 hours to transform the calcium sulfate dihydrate crystal whiskers into calcium sulfate hemihydrate crystal whiskers.

Please continue to refer to the fifth figure, which is a flow chart showing the steps of the method for treating sulfuric acid waste liquid containing hydrogen peroxide provided by the third preferred embodiment of the present invention. As shown in the first and fifth figures, the method for treating sulfuric acid waste liquid containing hydrogen peroxide of this embodiment includes the following steps S310 to S350; wherein, steps S310 to S340 are the same as the above-mentioned steps S110 to S140, so no further description is given here.

After step S340, step S350 is to control the calcium sulfate dihydrate crystal whiskers at a temperature between 170° C. and 200° C. for 5 to 8 hours to transform the calcium sulfate dihydrate crystal whiskers into anhydrous calcium sulfate crystal whiskers.

In summary, compared with the prior art, in order to recycle sulfuric acid waste liquid containing hydrogen peroxide, other chemicals are usually added to react with hydrogen peroxide, which may produce other by-products, even toxic substances, resulting in increased difficulty in the subsequent recycling process. The use of ultraviolet irradiation or centrifuge pressurization methods requires additional equipment, which will also greatly increase the overall recycling cost. The present invention's method for treating sulfuric acid waste liquid containing hydrogen peroxide mainly The process is to first heat the waste sulfuric acid solution to 50°C to 90°C and maintain the temperature for 1 to 2 hours to decompose the hydrogen peroxide in the waste sulfuric acid solution due to the high temperature environment. Then, the calcium-containing raw material is added to the waste sulfuric acid solution without hydrogen peroxide to form a calcium sulfate solution. After that, the hydrothermal generation method is used to crystallize the calcium sulfate in the calcium sulfate solution to form calcium sulfate dihydrate crystal whiskers. Finally, the calcium sulfate dihydrate crystal whiskers are filtered, washed and dried to obtain clean calcium sulfate dihydrate crystal whiskers. Among them, since calcium sulfate dihydrate crystal whiskers, calcium sulfate hemihydrate crystal whiskers and calcium sulfate anhydrous crystal whiskers can be applied to resins, plastics, rubbers, coatings, paints, papermaking, asphalt or sealing materials as reinforcing and toughening agents or functional fillers, and can also improve fire resistance, heat insulation and sound insulation, their economic value is much higher than the economic value of ammonium sulfate recycled by existing technologies.

More importantly, since it takes a while for the hydrothermal method to grow calcium sulfate dihydrate crystal whiskers, and the time required for crystal growth is much longer than the time required to heat the sulfuric acid waste liquid to remove hydrogen peroxide at the beginning, more batches of sulfuric acid waste liquid can be processed while the hydrothermal method is used to allow calcium sulfate to crystallize into calcium sulfate dihydrate crystal whiskers, and there will be no problem of the early process catching up with the subsequent process and affecting the production progress. In addition, the present invention uses heating to remove Hydrogen peroxide can effectively increase the sulfuric acid concentration of sulfuric acid waste liquid without generating more impurities. It not only has low energy consumption, but also does not require the addition of additional reagents for decomposing hydrogen peroxide. It can indeed effectively reduce the overall cost. In addition, the heating method is simpler and more convenient than ultraviolet light irradiation and centrifugal pressure. Most factories even have related heating devices inside, so there is no need to purchase other equipment and devices, which can effectively avoid the increase of process costs.

The above detailed description of the preferred specific embodiments is intended to more clearly describe the features and spirit of the present invention, but is not intended to limit the scope of the present invention by the preferred specific embodiments disclosed above. On the contrary, the purpose is to cover various changes and arrangements with equivalents within the scope of the patent application for the present invention.

S110-S140,S131-S132,S141-S144,S210-S250,S310-S350: Steps

The first figure is a flow chart showing the steps of the method for treating sulfuric acid waste liquid containing hydrogen peroxide provided in the first preferred embodiment of the present invention; The second figure is a flow chart showing the detailed steps of treating the calcium sulfate solution by hydrothermal generation in the method for treating sulfuric acid waste liquid containing hydrogen peroxide provided in the first preferred embodiment of the present invention; The third figure is a flow chart showing the detailed steps of filtering, washing and drying the calcium sulfate dihydrate crystal whiskers in the method for treating sulfuric acid waste liquid containing hydrogen peroxide provided in the first preferred embodiment of the present invention; The fourth figure is a flow chart showing the steps of the method for treating sulfuric acid waste liquid containing hydrogen peroxide provided in the second preferred embodiment of the present invention; and The fifth figure is a flow chart showing the steps of the method for treating sulfuric acid waste liquid containing hydrogen peroxide provided in the third preferred embodiment of the present invention.

S110-S140: Steps

Claims (5)

A method for treating sulfuric acid waste liquid containing hydrogen peroxide comprises the following steps: (A) heating a sulfuric acid waste liquid containing hydrogen peroxide to 50°C to 90°C and maintaining the temperature for 1 to 2 hours to decompose the hydrogen peroxide contained in the sulfuric acid waste liquid into water and oxygen, thereby generating a hydrogen peroxide-free sulfuric acid waste liquid; (B) adding a calcium-containing raw material to the hydrogen peroxide-free sulfuric acid waste liquid, so that the calcium ions in the calcium-containing raw material react with the sulfate ions in the hydrogen peroxide-free sulfuric acid waste liquid to generate calcium sulfate crystals, thereby forming a calcium sulfate solution containing the calcium sulfate crystals; (C) The calcium sulfate solution is treated by a hydrothermal method to transform the calcium sulfate crystals into calcium sulfate dihydrate crystal whiskers, thereby forming a calcium sulfate crystal whisker solution containing the calcium sulfate dihydrate crystal whiskers; and (D) the calcium sulfate dihydrate crystal whiskers are filtered out from the calcium sulfate crystal whisker solution, and the calcium sulfate dihydrate crystal whiskers are washed and dried. The method for treating sulfuric acid waste liquid containing hydrogen peroxide as described in claim 1, wherein step (C) further comprises the following steps: (C1) placing the calcium sulfate solution and a crystal whisker promoter in a reactor, and controlling the pH value of the calcium sulfate solution to be between 3 and 4 using a sulfuric acid solution; and (C2) controlling the temperature of the reactor to be between 150°C and 180°C and maintaining it for 5 hours to 9 hours, so that the calcium sulfate crystals are transformed into the calcium sulfate dihydrate crystal whiskers. The method for treating sulfuric acid waste liquid containing hydrogen peroxide as described in claim 1, wherein step (D) further comprises the following steps: (D1) filtering the calcium sulfate crystal whisker solution containing the calcium sulfate dihydrate crystal whisker to obtain the calcium sulfate dihydrate crystal whisker; (D2) washing the calcium sulfate dihydrate crystal whisker with clean water; (D3) dehydrating the calcium sulfate dihydrate crystal whisker; and (D4) controlling the environment of the calcium sulfate dihydrate crystal whisker at a temperature of 70°C to 100°C for drying. The method for treating sulfuric acid waste liquid containing hydrogen peroxide as described in claim 1 further comprises a step (E) after step (D), wherein the calcium sulfate dihydrate crystal whiskers are controlled at a temperature between 130° C. and 160° C. for 5 to 8 hours to convert the calcium sulfate dihydrate crystal whiskers into calcium sulfate hemihydrate crystal whiskers. The method for treating sulfuric acid waste liquid containing hydrogen peroxide as described in claim 1 further comprises a step (E) after step (D), wherein the calcium sulfate dihydrate crystal whiskers are controlled at a temperature between 170°C and 200°C for 5 hours to 8 hours to transform the calcium sulfate dihydrate crystal whiskers into anhydrous calcium sulfate crystal whiskers.

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