阅读说明：本技术 一种利用废酸生产高纯氟化钙及提浓废盐酸的方法 (Method for producing high-purity calcium fluoride and concentrating waste hydrochloric acid by using waste acid ) 是由 张凯 鮑鑫 邢岁平 于 2021-07-21 设计创作，主要内容包括：本发明公开了一种利用废酸生产高纯氟化钙及提浓废盐酸的方法,包括以下步骤：步骤1：将含氢氟酸、盐酸的混合酸进行过滤,将过滤后的混合酸加热至恒温50-60℃搅拌；步骤2：向经所述步骤1处理得到的混合酸溶液中滴加氯化钙溶液,搅拌反应结束后得到混合溶液,对所述混合溶液进行真空抽滤处理,得到盐酸溶液和沉淀物；步骤3：向所述沉淀物中加入氢氧化钠溶液,搅拌反应得到混合物,将混合物过滤分离出滤渣和碱性滤液,滤渣用去离子水冲洗后再烘干粉碎,得到高纯度氟化钙。解决了现有大量的含氢氟酸和盐酸的混合酸不能有效再利用的问题。(The invention discloses a method for producing high-purity calcium fluoride and concentrating waste hydrochloric acid by using waste acid, which comprises the following steps: step 1: filtering the mixed acid containing hydrofluoric acid and hydrochloric acid, heating the filtered mixed acid to a constant temperature of 50-60 ℃, and stirring; step 2: dropwise adding a calcium chloride solution into the mixed acid solution obtained by the treatment in the step 1, stirring and reacting to obtain a mixed solution, and performing vacuum filtration treatment on the mixed solution to obtain a hydrochloric acid solution and a precipitate; and step 3: and adding a sodium hydroxide solution into the precipitate, stirring and reacting to obtain a mixture, filtering the mixture to separate out filter residue and alkaline filtrate, washing the filter residue with deionized water, and drying and crushing the filter residue to obtain the high-purity calcium fluoride. Solves the problem that the existing large amount of mixed acid containing hydrofluoric acid and hydrochloric acid can not be effectively reused.)

1. A method for producing high-purity calcium fluoride and concentrating waste hydrochloric acid by using waste acid is characterized by comprising the following steps:

step 1: filtering the mixed acid containing hydrofluoric acid and hydrochloric acid, heating the filtered mixed acid to a constant temperature of 50-60 ℃, and stirring;

step 2: dropwise adding a calcium chloride solution into the mixed acid solution obtained by the treatment in the step 1, stirring and reacting to obtain a mixed solution, and performing vacuum filtration treatment on the mixed solution to obtain a hydrochloric acid solution and a precipitate;

and step 3: and adding a sodium hydroxide solution into the precipitate, stirring and reacting to obtain a mixture, filtering the mixture to separate out filter residue and alkaline filtrate, washing the filter residue with deionized water, and drying and crushing the filter residue to obtain the high-purity calcium fluoride.

2. The method for producing high-purity calcium fluoride and concentrating waste hydrochloric acid by using waste acid as claimed in claim 1, wherein in the step 2, the mass ratio of the calcium chloride solution to the mixed acid is (4:3) - (2:1), and the concentration of the calcium chloride solution is 10-40%.

3. The method for producing high-purity calcium fluoride and concentrating waste hydrochloric acid by using waste acid as claimed in claim 2, wherein in the step 2, the mass ratio of the calcium chloride solution to the mixed acid is 3: 2.

4. the method for producing high-purity calcium fluoride and concentrating waste hydrochloric acid by using waste acid as claimed in claim 1 or 2, wherein in the step 3, a NaOH solution with a concentration of 10% -30% is added, and the filter residue obtained by filtering and separating is subjected to primary water washing to obtain calcium fluoride.

5. The method for producing high-purity calcium fluoride and concentrating waste hydrochloric acid by using waste acid as claimed in claim 4, wherein in the step 3, the stirring reaction time is 20-30min, the drying temperature is 100-120 ℃, and the drying time is 1-2 h.

Technical Field

The invention belongs to the field of waste acid recycling, and particularly relates to a method for producing high-purity calcium fluoride and concentrating waste hydrochloric acid by using waste acid.

Background

With the continuous development of industries such as semiconductors, electronic chemistry and the like, the yield of waste acid such as acidic and alkaline etching cleaning solution and the like is more and more. During the production process, a large amount of mixed acid containing hydrofluoric acid and hydrochloric acid is generated due to process requirements. The composition of the mixed acid is hydrofluoric acid, hydrochloric acid, water, and a small amount of other impurities (mainly silicide). In daily life, the mixed acid cannot be directly sold, and is generally discharged after wastewater is neutralized and defluorinated. If the waste liquid is not well treated, serious environmental pollution can be caused.

Disclosure of Invention

The invention aims to provide a method for producing high-purity calcium fluoride and concentrating waste hydrochloric acid by using waste acid, so as to solve the problem that a large amount of mixed acid containing hydrofluoric acid and hydrochloric acid cannot be effectively reused.

The invention adopts the following technical scheme: a method for producing high-purity calcium fluoride and concentrating waste hydrochloric acid by using waste acid comprises the following steps:

step 1: filtering the mixed acid containing hydrofluoric acid and hydrochloric acid, heating the filtered mixed acid to a constant temperature of 50-60 ℃, and stirring;

step 2: dropwise adding a calcium chloride solution into the mixed acid solution obtained by the treatment in the step 1, stirring and reacting to obtain a mixed solution, and performing vacuum filtration treatment on the mixed solution to obtain a hydrochloric acid solution and a precipitate;

and step 3: and adding a sodium hydroxide solution into the precipitate, stirring and reacting to obtain a mixture, filtering the mixture to separate out filter residue and alkaline filtrate, washing the filter residue with deionized water, drying and crushing to obtain the high-purity calcium fluoride.

Further, in the step 2, the mass ratio of the calcium chloride solution to the mixed acid is (4:3) - (2:1), and the concentration of the calcium chloride solution is 10-40%.

Further, in the step 2, the mass ratio of the calcium chloride solution to the mixed acid is 3: 2.

further, in the step 3, a NaOH solution with the concentration of 10% -30% is added, and the filter residue obtained by filtering and separating is subjected to primary water washing to obtain calcium fluoride.

Further, in the step 3, the stirring reaction time is 20-30min, the drying temperature is 100-120 ℃, and the drying time is 1-2 h.

The invention has the beneficial effects that: the method of the invention firstly drops calcium chloride solution into waste acid containing hydrochloric acid and hydrofluoric acid at a certain speed, so that calcium chloride reacts with hydrofluoric acid to generate calcium fluoride which precipitates out, and the residual aqueous solution is hydrochloric acid with improved concentration; and dissolving the precipitate in sodium hydroxide water solution to eliminate silicon and drying to obtain high purity calcium fluoride solid. The calcium fluoride obtained by the method has high purity and few impurities, and can be directly sold or used; the hydrochloric acid solution with the increased concentration can be sold or used for waste water neutralization and the like; the treatment cost of neutralizing fluoride ions in the sewage is reduced; the mixed waste acid is recycled, the purposes of environmental protection and resource utilization are achieved, and obvious social and economic benefits are achieved.

Detailed Description

The present invention will be described in detail with reference to the following embodiments.

The invention provides a method for producing high-purity calcium fluoride and concentrating waste hydrochloric acid by using waste acid, which comprises the following steps:

step 1: filtering the mixed acid containing hydrofluoric acid and hydrochloric acid, heating the filtered mixed acid to a constant temperature of 50-60 ℃, and stirring;

step 2: and (2) dropwise adding a calcium chloride solution into the mixed acid solution obtained by the treatment in the step (1), stirring and reacting to obtain a mixed solution, and performing vacuum filtration treatment on the mixed solution to obtain a hydrochloric acid solution and a precipitate. The calcium chloride reacts with hydrofluoric acid in the mixed acid to generate hydrochloric acid, so that the concentration of the hydrochloric acid obtained by the step 2 is increased compared with the original waste acid, and the hydrochloric acid solution with the increased concentration can be sold or used for waste water neutralization.

And step 3: and adding a sodium hydroxide solution into the precipitate, stirring and reacting to obtain a mixture, filtering the mixture to separate out filter residue and alkaline filtrate, washing the filter residue with deionized water, and drying and crushing the filter residue to obtain the high-purity calcium fluoride.

In some embodiments, in the step 2, the mass ratio of the calcium chloride solution to the mixed acid is (4:3) - (2:1), and the concentration of the calcium chloride solution is 10-40%. The calcium chloride mainly reacts with hydrofluoric acid in the mixed acid to generate calcium fluoride and hydrochloric acid, generally, the concentration of the hydrofluoric acid in the waste mixed acid does not exceed the concentration before use, and the concentration of the electronic grade hydrofluoric acid is 49%. Therefore, 40% of calcium chloride can completely react with hydrofluoric acid in the mixed acid. The excess calcium chloride with the concentration of the calcium chloride exceeding 40 percent does not participate in the reaction and can bring new pollution.

In some embodiments, in step 2, the mass ratio of the calcium chloride solution to the mixed acid is 3: 2.

in some embodiments, in step 3, a NaOH solution with a concentration of 10% to 30% is added, and the filter residue separated by filtration is subjected to one-time water washing to obtain calcium fluoride. The sodium hydroxide is used for washing away silicon by alkali, and the impurity silicon in the calcium fluoride does not exceed 30 percent, so the silicon removal requirement can be met by the concentration of the sodium hydroxide between 10 and 30 percent. After the sodium oxide is washed with alkali to remove silicon, the silicon is washed with water, the content of sodium hydroxide exceeds 30%, and a large amount of heat release between the sodium hydroxide and water occurs during the washing with water, which is not beneficial to the operation of personnel.

In some embodiments, in the step 3, the stirring reaction time is 20-30min, the drying temperature is 100-120 ℃, and the drying time is 1-2 h.

In some embodiments, the alkaline filtrate separated in step 3 is discharged into acidic wastewater for neutralization and utilization.

Example 1

Step 1: filtering mixed acid containing 10% by mass of hydrofluoric acid and 15% by mass of hydrochloric acid to remove impurities, heating the filtered mixed acid to a constant temperature of 50 ℃, and stirring.

Step 2: and (2) dropwise adding a 10% calcium chloride solution into the mixed acid solution obtained by the treatment in the step (1), stirring and reacting for 10 minutes to obtain a mixed solution, and after the reaction is finished, carrying out vacuum filtration treatment on the mixed solution to obtain a hydrochloric acid solution with the concentration of 18.06% and a precipitate. Wherein the mass ratio of the calcium chloride solution to the mixed acid solution is 2:1 respectively.

And step 3: adding 10% sodium hydroxide solution into the precipitate, stirring and reacting for 20min to obtain a mixture, filtering the mixture to separate out filter residue and alkaline filtrate, washing the filter residue with deionized water, drying, crushing and drying at 105 ℃ for 1.6h to obtain 90.3% calcium fluoride.

Example 2

Step 1: filtering mixed acid containing 15% by mass of hydrofluoric acid and 15% by mass of hydrochloric acid to remove impurities, heating the filtered mixed acid to a constant temperature of 55 ℃, and stirring.

Step 2: and (2) dropwise adding a 40% calcium chloride solution into the mixed acid solution obtained by the treatment in the step (1), stirring and reacting for 10 minutes to obtain a mixed solution, and after the reaction is finished, carrying out vacuum filtration treatment on the mixed solution to obtain a 20.4% hydrochloric acid solution and a precipitate. Wherein the mass ratio of the calcium chloride solution to the mixed acid solution is 3:2 respectively.

And step 3: adding a sodium hydroxide solution with the concentration of 20% into the precipitate, stirring and reacting for 25min to obtain a mixture, filtering the mixture to separate out filter residue and alkaline filtrate, washing the filter residue with deionized water, drying and crushing, wherein the drying temperature is 120 ℃, and the drying time is 2h to obtain the calcium fluoride with the mass ratio of 93.5%.

Example 3

Step 1: filtering mixed acid containing 20% by mass of hydrofluoric acid and 15% by mass of hydrochloric acid to remove impurities, heating the filtered mixed acid to a constant temperature of 60 ℃, and stirring.

Step 2: and (2) dropwise adding a 20% calcium chloride solution into the mixed acid solution obtained by the treatment in the step (1), stirring and reacting for 10 minutes to obtain a mixed solution, and after the reaction is finished, carrying out vacuum filtration treatment on the mixed solution to obtain a 20.7% hydrochloric acid solution and a precipitate. Wherein the mass ratio of the calcium chloride solution to the mixed acid solution is 3:2 respectively.

And step 3: adding 30% sodium hydroxide solution into the precipitate, stirring and reacting for 30min to obtain a mixture, filtering the mixture to separate out filter residue and alkaline filtrate, washing the filter residue with deionized water, drying and crushing, wherein the drying temperature is 110 ℃, and the drying time is 1.5h to obtain 93.6% calcium fluoride by mass ratio.

Example 4

Step 1: filtering mixed acid containing 30% by mass of hydrofluoric acid and 15% by mass of hydrochloric acid to remove impurities, heating the filtered mixed acid to a constant temperature of 52 ℃, and stirring.

Step 2: and (2) dropwise adding a 40% calcium chloride solution into the mixed acid solution obtained by the treatment in the step (1), stirring and reacting for 10 minutes to obtain a mixed solution, and after the reaction is finished, carrying out vacuum filtration treatment on the mixed solution to obtain a hydrochloric acid solution with the concentration of 12.6% and a precipitate. Wherein the mass ratio of the calcium chloride solution to the mixed acid solution is 4:3 respectively.

And step 3: adding a 26% sodium hydroxide solution into the precipitate, stirring and reacting for 22min to obtain a mixture, filtering the mixture to separate out filter residue and alkaline filtrate, washing the filter residue with deionized water, drying and crushing, wherein the drying temperature is 100 ℃, and the drying time is 1h to obtain 93.7% by mass of calcium fluoride.

TABLE 1

As the 12 sets of experimental data are provided in table 1 above, the steps of the 12 sets of experiments are the same as those of the method for producing high-purity calcium fluoride and concentrating waste hydrochloric acid by using waste acid, and the differences only lie in that the contents of hydrofluoric acid and hydrochloric acid in the used mixed acid solution are different, and the mass ratio of the added calcium fluoride solution to the mixed acid solution is different, so that different experimental results are obtained by using different amounts, and the influence of different calcium chloride adding amounts on the quality of calcium fluoride products and the quality of hydrochloric acid is analyzed.

As shown in table 1, each group uses a 40% calcium chloride solution, the mass fractions of hydrofluoric acid and hydrochloric acid in the mixed acid solutions of groups 1 to 3 are 10% and 15%, respectively, and the mass ratios of the amount of the calcium fluoride solution to the mixed acid solution are 2:1, 3:2 and 4:3, respectively; in the mixed acid solution of the 4 th to 6 th groups, the mass fractions of hydrofluoric acid and hydrochloric acid are 15% and 15%, respectively, and the mass ratios of the use amount of the calcium fluoride solution to the mixed acid solution are 2:1, 3:2 and 4:3, respectively; in the mixed acid solution of the 7 th to 9 th groups, the mass fractions of hydrofluoric acid and hydrochloric acid are respectively 20% and 15%, and the mass ratios of the use amount of the calcium fluoride solution to the mixed acid solution are respectively 2:1, 3:2 and 4: 3; in the mixed acid solution of the 10 th to 12 th groups, the mass fractions of hydrofluoric acid and hydrochloric acid are respectively 30% and 15%, and the mass ratios of the amount of the calcium fluoride solution to the mixed acid solution are respectively 2:1, 3:2 and 4: 3.

In the above 12 experiments, calcium chloride was prepared as an aqueous solution with a concentration of 40%, as shown in Table 1, when m (CaCl)₂) M (mixed acid) is 4: 1 hour, although CaF can be lifted₂Concentration, but due to CaCl₂Excessive addition will result in a decrease in the concentration of HCl in the solution. When m (CaCl)₂) M (mixed acid) mass ratio of 2: at 1, CaF in precipitate B can be seen₂The content is low. When m (CaCl)₂) M (mixed acid) mass ratio is 3: and 2, the content of calcium fluoride and the content of hydrochloric acid are optimal schemes.

TABLE 2

The above table 2 provides 6 sets of experimental data, and the methods of the 6 sets of experiments all adopt the steps of the method for producing high-purity calcium fluoride and concentrating waste hydrochloric acid by using waste acid, and the differences only lie in that the treatment process in the step 3 is different, and the influence of the concentration of sodium hydroxide on the quality of calcium fluoride is analyzed through different data.

When the content of calcium fluoride in the precipitate B is less than 97.5%, the precipitate B cannot be directly used or sold. It needs alkali washing to remove silicon and water washing to remove impurities. In order to ensure the quality of calcium fluoride products, the alkali washing and the water washing are carried out for experiment selection to determine the washing impurity removal mode. As seen from Table 2, the product recovery rate was highest without washing, but the product content was low, the silica content was high, and the product quality requirements could not be satisfied. The silica impurities cannot be removed by simple water washing. The calcium fluoride has small solubility in water, and the product recovery rate is low after 2 times of washing. When NaOH with the concentration of 10% is added and primary washing is combined, the silicon dioxide impurities of the obtained calcium fluoride product exceed the standard (the requirement of the national standard of calcium fluoride on the silicon dioxide content cannot be more than 0.4%), and when NaOH with the concentration of 30% is added and primary washing is combined, the drying yield of the obtained calcium fluoride product is too low. Therefore, when NaOH with the concentration of 20% is adopted and one-time water washing is combined, the product quality and the product recovery rate can be ensured, and simultaneously, the silicon dioxide can also meet the requirements.

Comparative example analysis

Taking 15kg of waste mixed acid (the waste acid contains 20 mass percent of hydrofluoric acid and 15 mass percent of hydrochloric acid) of a certain photovoltaic enterprise, and dividing the waste mixed acid into 3 barrels (5 kg/barrel). Comparative example 1A barrel was charged with 40% Ca (OH)₂Comparative example 2 CaCO with a concentration of 40% was added to a barrel₃Example 3A 40% strength CaCl was added to a barrel₂Respectively stirring for 10min, performing solid-liquid separation, and respectively measuring the content of HCL in the separated liquid; three groups of solids (CaF)₂) Adding 20% NaOH solution, stirring, reacting for 20min to obtain mixture, filtering the three mixtures to separate out residue and alkaline filtrate, washing the residue with deionized water, oven drying, pulverizing, and measuring CaF in solid respectively₂Content of (A) and SiO₂The contents are shown in Table 3.

TABLE 3

As can be seen from Table 3, the hydrochloric acid concentration of solution A obtained by the method of example 3 is high and reaches the commercial standard. And Ca (OH)₂Combined with water washing or CaCO₃Combined water washing processes except reaction with HF in mixed acid to form CaF₂And the mixed acid can also react with HCL to produce other substances, so that the concentration of HCL in the mixed acid is reduced. The method of alkali washing and water washing in example 3 can further improve CaF₂Purity, removal of CaF₂The impurities inside.

The method of the invention firstly drops calcium chloride solution into waste acid containing hydrochloric acid and hydrofluoric acid at a certain speed, so that calcium chloride reacts with hydrofluoric acid to generate calcium fluoride which precipitates out, and the residual aqueous solution is hydrochloric acid with improved concentration; and dissolving the precipitate in sodium hydroxide water solution to eliminate silicon and drying to obtain high purity calcium fluoride solid. The calcium fluoride obtained by the method has high purity and few impurities, and can be directly sold or used; the hydrochloric acid solution with the increased concentration can be sold or used for waste water neutralization and the like; the treatment cost of neutralizing fluoride ions in the sewage is reduced; the invention recycles the mixed acid from the viewpoint of recycling economy, and produces other fluorine chemical products by using hydrofluoric acid in the mixed acid, thereby separating the fluorine chemical products from hydrochloric acid and selling the fluorine chemical products and related products formed by the hydrochloric acid respectively. Therefore, the method can reduce a large amount of fluorine-containing industrial waste, improve the environment, realize the maximum resource utilization rate, reduce the production cost and have obvious social and economic benefits.