A method for recovering fluorosilicate from high-purity quartz sand pickling wastewater

Abstract

The invention discloses a method for recovering fluorosilicate from high-purity quartz sand pickling wastewater, and belongs to the field of fluorosilicate recovery technology. The method of the present invention comprises the following steps: S1 high-purity quartz sand is pickled with hydrofluoric acid (ultrapure);S2 pickling is press-filtered to pickling solution after the pickling is completed to obtain fine quartz sand solid and fluorosilicic acid filtrate;S3 fluorosilicic acid filtrate is stirred and heated up and concentrated and then continues to add inorganic alkali solution for sedimentation, until the mixed solution pH is 7.2-7.5 and stops adding inorganic alkali solution;S4 carries out press-filtration to the mixed solution after sedimentation, collects filter cakes to dryness and obtains fluorosilicate. The fluorosilicate purity obtained by applying this method to reclaim is high and the recovery rate is high, and it is achieved that waste resources can be reused, and environmental protection is achieved, with the characteristics of green environmental protection economy.

Description

Technical Field

[0001] The invention belongs to the technical field of fluorosilicate recovery, and particularly relates to a method for recovering fluorosilicate from high-purity quartz sand pickling wastewater. Background Art

[0002] High-purity quartz sand boasts unique optical properties, including excellent chemical stability, high-temperature resistance, low thermal expansion coefficient, high insulation, corrosion resistance, piezoelectric effect, and resonance effect. It is the sole raw material for quartz glass and its products, and is widely used in industries such as photovoltaics, electric light sources, semiconductors, fiber-optic communications, and aerospace. The purification process for quartz sand primarily involves silica sorting, roasting / water quenching, crushing / screening, magnetic separation, acid leaching, flotation, drying, cooling, and packaging. The acid leaching process primarily involves hydrofluoric acid pickling. During the pickling process, hydrofluoric acid reacts with the quartz sand to form fluorosilicic acid. Direct discharge of this untreated fluorosilicic acid not only causes severe environmental pollution, but also forms fluorosilicates, which are commonly used in wood preservation, ceramic manufacturing, aluminum and magnesium smelting, agricultural pesticides, optical glass manufacturing, mica synthesis, and the production of ceramic glazes, enamels, and other products. Failure to recycle and reuse this fluorosilicate results in significant waste. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for recovering fluorosilicate from high-purity quartz sand pickling wastewater, so as to solve the problem that waste acid liquid is polluted during the pickling process of high-purity quartz sand and the fluorosilicate product generated by the reaction cannot be recycled and reused.

[0004] The purpose of the present invention can be achieved through the following technical solutions:

[0005] A method for recovering fluorosilicate from high-purity quartz sand pickling wastewater comprises the following steps:

[0006] S1. High-purity quartz sand is added to the reactor, and hydrofluoric acid (ultrapure) is added to the reactor for pickling. The pickling temperature is 60-70 ° C and the pickling time is 2-4h;

[0007] S2. After the pickling is completed, the pickling liquid is placed in a filter press to obtain a product of fine quartz sand solid and fluosilicic acid filtrate;

[0008] S3. The fluorosilicic acid filtrate is placed in a settling tank, the stirring speed is set to 100-200 rpm, and after stirring for 15-20 min, the temperature is raised to 80-100 ° C, and the inorganic base solution is continuously added until the pH of the filtrate is 7.2-7.5, and the addition of the inorganic base solution is stopped; during the addition of the inorganic base solution, solid material will continue to precipitate in the settling tank;

[0009] S4. The material solution in the settling tank is filtered using a filter press to separate the filter cake and the filtrate. The filter cake is rinsed with deionized water 3-5 times and then dried in an oven to obtain fluorosilicate.

[0010] Furthermore, the filtration pressure in S2 is 0.1-0.15 MPa.

[0011] Furthermore, the inorganic alkaline solution in S3 is any one of KOH, NaOH, potassium carbonate, and sodium carbonate.

[0012] Furthermore, the concentration of the inorganic alkali solution in S3 is 5-25 wt%.

[0013] Furthermore, the filter cake is placed in an oven (vacuum state) for drying in S4 by reduced pressure drying, the reduced pressure drying temperature is 60° C., and the reduced pressure drying time is 2-5 h.

[0014] Furthermore, after the addition of the inorganic alkali solution in S3 is stopped, the temperature in the sedimentation tank is raised to 70-85°C under stirring conditions of 75-125 rpm, and kept warm for 30-45 minutes. Then, the temperature in the sedimentation tank is lowered to 0-5°C under stirring conditions of 20-60 rpm and kept warm for 5-10 minutes. During the cooling process, solid material will continue to precipitate in the sedimentation tank.

[0015] Beneficial effects of the present invention:

[0016] The present invention provides a method for recovering fluorosilicate from high-purity quartz sand pickling wastewater. The fluorosilicate recovered by the method has high purity and high recovery rate, realizes the reusability of waste resources, protects the environment, and has the characteristics of being green, environmentally friendly and economical. DETAILED DESCRIPTION

[0017] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0018] Example 1

[0019] A method for recovering fluorosilicate from high-purity quartz sand pickling wastewater comprises the following steps:

[0020] S1. High-purity quartz sand was added to the reactor, and hydrofluoric acid (ultrapure) was added to the reactor for pickling. The pickling temperature was 60 ° C and the pickling time was 4h;

[0021] S2. After the pickling is completed, the pickling liquid is placed in a filter press and the filter pressure is controlled to be 0.15MPa to obtain a product of fine quartz sand solid and fluorosilicic acid filtrate;

[0022] S3. The fluorosilicic acid filtrate was placed in a settling tank, stirred at 150 rpm for 20 min, then heated to 100 ° C, and a 15 wt% NaOH solution was continuously added until the pH of the filtrate reached 7.5, at which time the addition of NaOH solution was stopped. The temperature in the settling tank was raised to 70 ° C under stirring at 100 rpm, kept warm for 30 min, and then lowered to 0 ° C under stirring at 45 rpm. The mixture was allowed to settle for 8 min. During this process, solid material was continuously precipitated in the settling tank.

[0023] S4. The material solution in the sedimentation tank is filtered using a filter press to separate the filter cake and the filtrate. A lime solution is added to the filtrate for harmless and environmentally friendly treatment. The filter cake is rinsed with deionized water 5 times, and then placed in an oven and dried at 60°C under vacuum for 5 hours to recover sodium fluorosilicate.

[0024] Example 2

[0025] A method for recovering fluorosilicate from high-purity quartz sand pickling wastewater comprises the following steps:

[0026] S1. High-purity quartz sand was added to the reactor, and hydrofluoric acid (ultrapure) was added to the reactor for pickling. The pickling temperature was 70 ° C and the pickling time was 4h;

[0027] S2. After the pickling is completed, the pickling liquid is placed in a filter press and the filter pressure is controlled to be 0.1MPa to obtain a product of fine quartz sand solid and fluorosilicic acid filtrate;

[0028] S3. The fluorosilicic acid filtrate was placed in a settling tank, stirred at 150 rpm for 20 min, then heated to 90 ° C, and a 5 wt% KOH solution was continuously added until the pH of the filtrate reached 7.2, at which time the addition of KOH solution was stopped. The temperature in the settling tank was raised to 70 ° C under stirring at 90 rpm, kept warm for 40 min, and then lowered to 5 ° C under stirring at 40 rpm. The mixture was allowed to settle for 10 min. During this process, solid material was continuously precipitated in the settling tank.

[0029] S4. The material solution in the sedimentation tank is filtered using a filter press to separate the filter cake and the filtrate. A lime solution is added to the filtrate for harmless and environmentally friendly treatment. The filter cake is rinsed with deionized water four times, and then placed in an oven and dried at 60°C under vacuum for 5 hours to recover potassium fluorosilicate.

[0030] Example 3

[0031] A method for recovering fluorosilicate from high-purity quartz sand pickling wastewater comprises the following steps:

[0032] S1. High-purity quartz sand was added to the reactor, and hydrofluoric acid (ultrapure) was added to the reactor for pickling at a temperature of 68°C for 2 hours.

[0033] S2. After the pickling is completed, the pickling liquid is placed in a filter press and the filter pressure is controlled to be 0.12MPa to obtain a product of fine quartz sand solid and fluorosilicic acid filtrate;

[0034] S3. The fluorosilicic acid filtrate was placed in a settling tank and stirred at 150 rpm for 15 min. The temperature was then raised to 80 ° C. A 15 wt% K2CO3 solution was continuously added until the pH of the filtrate reached 7.5. The addition of K2CO3 solution was stopped and the temperature in the settling tank was raised to 72 ° C. at 100 rpm. After 40 min of heat preservation, the temperature in the settling tank was lowered to 5 ° C. at 40 rpm of stirring and allowed to settle for 8 min. During this process, solid material was continuously precipitated in the settling tank.

[0035] S4. The material solution in the sedimentation tank is filtered using a filter press to separate the filter cake and the filtrate. A lime solution is added to the filtrate for harmless and environmentally friendly treatment. The filter cake is rinsed with deionized water four times, and then placed in an oven and dried at 60°C under vacuum for 5 hours to recover potassium fluorosilicate.

[0036] Example 4

[0037] A method for recovering fluorosilicate from high-purity quartz sand pickling wastewater comprises the following steps:

[0038] S1. High-purity quartz sand was added to the reactor, and hydrofluoric acid (ultrapure) was added to the reactor for pickling at a temperature of 68°C for 2 hours.

[0039] S2. After the pickling is completed, the pickling liquid is placed in a filter press and the filter pressure is controlled to be 0.12MPa to obtain a product of fine quartz sand solid and fluorosilicic acid filtrate;

[0040] S3. The fluorosilicic acid filtrate was placed in a settling tank and stirred at 150 rpm for 15 min. The temperature was then raised to 95 ° C. An 18 wt% Na2CO3 solution was continuously added until the pH of the filtrate reached 7.5. The addition of Na2CO3 solution was stopped and the temperature in the settling tank was raised to 72 ° C. at 110 rpm. After the temperature was kept at 72 ° C. for 42 min, the temperature in the settling tank was lowered to 5 ° C. at 45 rpm and allowed to settle for 6 min. During this process, solid material was continuously precipitated in the settling tank.

[0041] S4. The material solution in the sedimentation tank is filtered using a filter press to separate the filter cake and the filtrate. A lime solution is added to the filtrate for harmless and environmentally friendly treatment. The filter cake is rinsed with deionized water four times, and then placed in an oven and dried at 60°C under vacuum for 5 hours to recover sodium fluorosilicate.

[0042] The fluorosilicate obtained by drying in Examples 1 to 4 was tested for content, and the test results are shown in Table 1:

[0043] Table 1

[0044]

[0045] As can be seen from Table 1, the silicate recovered by adopting the technical solution disclosed in the present invention has not only high content and high purity, but also high recovery rate.

[0046] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0047] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for recovering fluorosilicate from high-purity quartz sand pickling wastewater, characterized in that: The following steps are involved: S1. High-purity quartz sand is pickled with hydrofluoric acid; S2. After the pickling is completed, the pickling liquid is filtered to obtain fine quartz sand solid and fluosilicic acid filtrate; S3. After the filtrate was concentrated with stirring, the inorganic base solution was continuously added and allowed to settle until the pH of the mixed solution was 7.2-7.5, and the addition of the inorganic base solution was stopped; S4. The mixed solution after settling was filter-pressed, and the filter cake was collected and dried to obtain fluorosilicate; After stopping the addition of the inorganic alkali solution in S3, the temperature is raised to 70-85° C. under stirring at 75-125 rpm and kept warm for 30-45 minutes. Then, the temperature in the settling tank is lowered to 0-5° C. under stirring at 20-60 rpm and kept warm for 5-10 minutes.

2. The method for recovering fluorosilicate from high-purity quartz sand pickling wastewater according to claim 1, wherein: The pickling temperature in S1 is 60-70° C., and the pickling time is 2-4 hours.

3. The method for recovering fluorosilicate from high-purity quartz sand pickling wastewater according to claim 1, wherein: The filter pressure in S2 is 0.1-0.15 MPa.

4. The method for recovering fluorosilicate from high-purity quartz sand pickling wastewater according to claim 1, wherein: In the step S3, the temperature is raised to 80-100° C. with a stirring speed of 100-200 rpm and a stirring time of 15-20 min.

5. The method for recovering fluorosilicate from high-purity quartz sand pickling wastewater according to claim 1, wherein: The inorganic alkaline solution in S3 is any one of KOH, NaOH, potassium carbonate and sodium carbonate.

6. The method for recovering fluorosilicate from high-purity quartz sand pickling wastewater according to claim 1, wherein: The concentration of the inorganic alkali solution in S3 is 5-25 wt %.

7. The method for recovering fluorosilicate from high-purity quartz sand pickling wastewater according to claim 1, wherein: The filter cake is dried under reduced pressure in step S4 at a temperature of 60° C. for 2-5 hours.

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