Treatment process of high-purity quartz sand acid washing wastewater

Abstract

The application discloses a treatment process of high-purity quartz sand acid washing wastewater and belongs to the technical field of wastewater treatment. The treatment process comprises the following steps: S1, high-purity quartz sand acid washing wastewater is discharged into raw water pool and is left standing; S2, the wastewater is pumped to a neutralization pool, lime water is added, and the pH of the wastewater in the pool is adjusted to 6.0-7.0; S3, after neutralization, the wastewater is transported to a coagulation and sedimentation pool, calcium chloride and PAC are added, coagulation stirring is carried out, standing and sedimentation are carried out, and after sedimentation, sludge is discharged to a sludge pool; S4, the supernatant of the coagulation and sedimentation is discharged to an ion adsorption pool, stirring is started, an adsorbent calcium aluminum hydrotalcite is added to the pool for adsorption, and the content of fluorine ions is determined, until the content of fluorine ions is lower than 5 mg / L, the stirring and adsorption are stopped, and the water quality reaches the standard and is discharged to a discharge pool. The method can realize stable adsorption under a low fluorine ion concentration, significantly improves the removal rate of fluorine ions, and finally obtains standard wastewater with a fluorine content of not more than 5 mg / L.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of wastewater treatment, and particularly relates to a treatment process for high-purity quartz sand acid washing wastewater. BACKGROUND

[0002] The photovoltaic quartz sand obtained from the high-purity quartz ore is a basic raw material in the fields of aerospace, electronics, optical fiber communication and military industry. The purification process of the quartz ore mainly includes: silicon stone sorting, roasting / water quenching, crushing / sieving, magnetic separation, acid leaching, flotation, drying, cooling and packaging. The acid leaching process mainly adopts HF acid washing, and therefore a large amount of high-fluorine acid washing wastewater is generated. If the high-fluorine acid washing wastewater is not properly treated and leaks to the surrounding field, the fluorine content in the groundwater is too high, which causes serious environmental pollution problems. Therefore, the removal of fluorine in water treatment is extremely important in water purification and is also a guarantee for the sustainable development of the high-purity quartz sand production industry. -

[0003] The existing treatment method for the acid washing fluorine-containing wastewater is mainly the precipitation method and the adsorption method. The adsorption method mainly removes the fluorine in the wastewater by adsorption of the adsorbent. The commonly used adsorbents include carbonaceous materials, solid industrial waste red mud, fly ash and impregnated activated alumina. Although the adsorption operation is simple, the adsorption capacity of the adsorbent is greatly affected by the fluorine concentration. With the decrease of the fluorine concentration, the adsorption capacity will be significantly reduced, and therefore the defluorination efficiency is low. The precipitation method generally adopts calcium salt precipitation, that is, lime milk is added to the wastewater to make the fluorine ions and calcium ions generate CaF2 precipitation to remove the fluorine. However, under normal conditions, the solubility of CaF2 is 8.9 mg / L, and therefore the effluent after treatment is difficult to meet the standard, the sludge settlement is slow and the dewatering is difficult. SUMMARY

[0004] The purpose of the present application is to provide a treatment process for high-purity quartz sand acid washing wastewater, so as to solve the problems of unstable adsorption capacity of the adsorbent under the condition of low fluorine ion concentration and low fluorine ion removal efficiency in the acid washing wastewater.

[0005] The purpose of the present application can be achieved by the following technical scheme:

[0006] A treatment process for high-purity quartz sand acid washing wastewater, comprising the following steps:

[0007] S1. The high-purity quartz sand acid washing wastewater is discharged into a raw water tank and is allowed to stand for 12-18 hours to achieve water quality balance;

[0008] S2. The wastewater in the tank is pumped to a neutralization tank, and lime water (Ca(OH)2) is added to adjust the pH of the wastewater in the tank to 6.0-7.0;

[0009] ​S3. The neutralized wastewater is transported to a coagulation sedimentation tank, calcium chloride and PAC (polyaluminum chloride) are added, coagulation stirring is performed for 20-30 min, standing and sedimentation are performed, the sludge after sedimentation is discharged to a sludge tank, the content of fluoride ions in the supernatant is determined, if the content of fluoride ions is higher than 20 mg / L, the supernatant is returned to the neutralization tank for treatment;

[0010] S4. The coagulation sedimentation supernatant is discharged to an ion adsorption tank, stirring is started, adsorbent calcium aluminum hydrotalcite is added to the tank in 4-6 times for adsorption, and the content of fluoride ions is determined until the content of fluoride ions is lower than 5 mg / L, the stirring and adsorption are stopped, the final addition amount of adsorbent calcium aluminum hydrotalcite to the coagulation sedimentation supernatant is 1.8-2.2 g:1 L, the adsorption time is 4-6 h, and the water quality meets the standard and is discharged to a discharge tank.

[0011] Further, the concentration of lime water in S2 is 25%-30%.

[0012] Further, the concentration of calcium chloride in S3 is 40%.

[0013] Further, the concentration of PAC in S3 is 15%.

[0014] Further, the stirring speed in S3 is 200 r / min, and the stirring speed in S4 is 200 r / min.

[0015] Further, the preparation method of the adsorbent calcium aluminum hydrotalcite in S4 comprises the following steps:

[0016] 100 mL of 0.25 mol / L calcium nitrate solution and 100 mL of 0.15 mol / L aluminum nitrate solution are uniformly mixed, under stirring conditions, 100 mL of mixed alkali solution prepared by mixing sodium carbonate and sodium hydroxide is added dropwise at a rate of 2 mL / min at 55-65 DEG C, the mixed alkali solution is adjusted to maintain a pH of 11-12, and is placed in a vacuum condition, and is aged at 45 DEG C for 12-15 h, and is filtered and washed to neutral; after freezing drying for 18 h, the adsorbent calcium aluminum hydrotalcite is obtained by calcining at 400 DEG C under Ar protection for 2-3 h.

[0017] Further, the mass ratio of sodium carbonate to sodium hydroxide is 0.2-0.3:0.1.

[0018] Further, the stirring rate is 500 r / min.

[0019] The beneficial effects of the present application are:

[0020] 1. The application provides a high-purity quartz sand acid washing wastewater treatment process, which comprises the following steps: discharging high-purity quartz sand acid washing wastewater into a raw water pool to stand and balance, then sequentially discharging into a neutralization pool, a coagulation sedimentation pool and an ion adsorption pool for wastewater treatment, wherein the ion adsorption agent is calcium-aluminum hydrotalcite, the fluorine ion removal rate of the high-purity quartz sand acid washing wastewater reaches 83.4%, and the fluorine content of the treated wastewater is less than 5 mg / L.

[0021] 2. In the application, the calcium-aluminum bimetallic oxide obtained after calcination is put into a water environment to restore the original layered structure of the calcium-aluminum bimetallic hydroxide, thereby realizing the absorption of anions in the water environment; in addition, the calcium-aluminum hydrotalcite can significantly improve the removal efficiency of fluorine ions and realize stable adsorption at a low fluorine ion concentration, because fluorine ions have a strong coordination effect with aluminum ions and new impurity metal ions are avoided.

[0022] 3. The process adopted by the application has simple operation and low treatment cost. DETAILED DESCRIPTION

[0023] The application will be further described below in combination with the drawings.

[0024] Figure 1 FIG. 1 is a graph showing the relationship between the adsorption capacity of the calcium-aluminum hydrotalcite adsorbent and time in Example 2 of the application. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the application will be clearly and completely described below in combination with the embodiments of the application. Obviously, the described embodiments are only a part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without any creative effort fall within the protection scope of the application.

[0026] Example 1

[0027] The preparation method of the calcium-aluminum hydrotalcite adsorbent comprises the following steps:

[0028] 100 mL of a 0.25 mol / L calcium nitrate solution and 100 mL of a 0.15 mol / L aluminum nitrate solution are uniformly mixed, 100 mL of a mixed alkali solution prepared by mixing 0.25 mol of sodium carbonate and 0.1 mol of sodium hydroxide is added dropwise at a rate of 2 mL / min under the condition of a stirring rate of 500 r / min and a temperature of 60℃, the mixed alkali solution is adjusted to maintain a pH of 11-12, and then the solution is placed in a vacuum condition, aged at 45℃ for 14 h, filtered and washed to neutral, frozen and dried for 18 h, and then calcined at 400℃ for 2.5 h under vacuum and Ar protection to obtain the calcium-aluminum hydrotalcite adsorbent.

[0029] Example 2

[0030] The adsorption capacity of the prepared adsorbent calcium-aluminum hydrotalcite for fluoride ions was tested:

[0031] 125 mg of the adsorbent calcium-aluminum hydrotalcite was put into 100 mL of a NaF aqueous solution with a concentration of 20 mg / L, and the adsorption test was carried out at room temperature (25-30℃) with a stirring speed of 200 r / min. The fluoride ion concentration in the solution was tested every 30 min using a fluoride ion selective electrode, and the test was continued for 5 h. The test results are shown in Table 1, and it can be seen from Table 1 that Figure 1 in the first 2.5 h, the adsorbent calcium-aluminum hydrotalcite exhibited rapid adsorption for fluoride ions, and the maximum adsorption capacity could reach 19.51 mg / L. At this time, the adsorption of fluoride ions reached a saturation equilibrium, and the adsorption capacity remained in a dynamic equilibrium. Figure 1

[0032] Example 3

[0033] A treatment process for high-purity quartz sand acid washing wastewater includes the following steps:

[0034] S1. The high-purity quartz sand acid washing wastewater is discharged into a raw water pool and is allowed to stand for 15 h to achieve water quality balance;

[0035] S2. The wastewater is pumped to a neutralization pool, lime water with a concentration of 28% is added, and the pH of the wastewater in the pool is adjusted to 6.5;

[0036] S3. The neutralized wastewater is transported to a coagulation and sedimentation pool, calcium chloride with a concentration of 40% and PAC with a concentration of 15% are added, coagulation stirring is carried out at a stirring speed of 200 r / min for 25 min, and then the wastewater is allowed to stand for sedimentation. After sedimentation, the sludge is discharged to a sludge pool, and the fluoride ion content in the supernatant is measured to be 18 mg / L;

[0037] S4. The coagulation and sedimentation supernatant is discharged to an ion adsorption pool, stirring is carried out at a speed of 200 r / min, adsorbent calcium-aluminum hydrotalcite is added to the pool in four times for adsorption, and the fluoride ion content is measured until the fluoride ion content is 2.0 mg / L. The stirring and adsorption are stopped, the final addition amount of the adsorbent calcium-aluminum hydrotalcite to the coagulation and sedimentation supernatant is 2 g:1 L, the adsorption time is 5 h, and the water quality meets the standard and is discharged to a discharge water pool.

[0038] Example 4

[0039] A treatment process for high-purity quartz sand acid washing wastewater includes the following steps:

[0040] S1. The high-purity quartz sand acid washing wastewater is discharged into a raw water pool and is allowed to stand for 12 h to achieve water quality balance;

[0041] ​S2. Pump up to the neutralization tank, add lime water with a concentration of 25%, adjust the pH of the wastewater in the tank to 6.0;

[0042] S3. The neutralized wastewater is transported to the coagulation sedimentation tank, calcium chloride with a concentration of 40% and PAC with a concentration of 15% are added, coagulation stirring is carried out at a stirring speed of 200 r / min for 30 min, standing and sedimentation are carried out, the sludge after sedimentation is discharged to the sludge tank, and the fluorine ion content in the supernatant is measured to be 19 mg / L;

[0043] S4. The coagulation sedimentation supernatant is discharged to the ion adsorption tank, stirring is carried out at 200 r / min, adsorbent calcium aluminum hydrotalcite is added to the tank in 6 times for adsorption, and the fluorine ion content is measured, until the fluorine ion content is 3.1 mg / L in the last measurement, the stirring and adsorption are stopped, the final adsorbent calcium aluminum hydrotalcite addition amount and the coagulation sedimentation supernatant usage amount ratio is 1.8 g:1 L, the adsorption time is 6 h, and the water quality meets the standard and is discharged to the discharge water tank.

[0044] Example 5

[0045] A treatment process of high-purity quartz sand acid washing wastewater, comprising the following steps:

[0046] S1. The high-purity quartz sand acid washing wastewater is discharged to the raw water tank, and is left standing for 17.5 h to achieve water quality balance;

[0047] S2. Pump up to the neutralization tank, add lime water with a concentration of 30%, and adjust the pH of the wastewater in the tank to 6.8;

[0048] S3. The neutralized wastewater is transported to the coagulation sedimentation tank, calcium chloride with a concentration of 40% and PAC with a concentration of 15% are added, coagulation stirring is carried out at a stirring speed of 200 r / min for 30 min, standing and sedimentation are carried out, the sludge after sedimentation is discharged to the sludge tank, and the fluorine ion content in the supernatant is measured to be 17 mg / L;

[0049] S4. The coagulation sedimentation supernatant is discharged to the ion adsorption tank, stirring is carried out at 200 r / min, adsorbent calcium aluminum hydrotalcite is added to the tank in 5 times for adsorption, and the fluorine ion content is measured, until the fluorine ion content is 2.6 mg / L, the stirring and adsorption are stopped, the final adsorbent calcium aluminum hydrotalcite addition amount and the coagulation sedimentation supernatant usage amount ratio is 2.2 g:1 L, the adsorption time is 4.2 h, and the water quality meets the standard and is discharged to the discharge water tank.

[0050] Comparative Example 1

[0051] A treatment process of high-purity quartz sand acid washing wastewater, comprising the following steps:

[0052] S1. The high-purity quartz sand acid washing wastewater is discharged to the raw water tank, and is left standing for 15 h to achieve water quality balance;

[0053] S2. Pumping to the neutralization tank, adding lime water with a concentration of 28%, adjusting the pH of the wastewater in the tank to 6.5;

[0054] S3. The neutralized wastewater is transported to the coagulation sedimentation tank, adding calcium chloride with a concentration of 40% and PAC with a concentration of 15%, coagulating and stirring at a stirring speed of 200 r / min for 25 min, standing and depositing, and after depositing, the sludge is discharged to the sludge tank, and the content of fluorine ions in the supernatant is measured to be 18 mg / L;

[0055] S4. The supernatant is returned to the neutralization tank, and the coagulation sedimentation is repeated 4 times.

[0056] The wastewater treated by Examples 3-5 and Comparative Example 1 is detected for fluorine ion content, and the detection results are shown in Table 1:

[0057] Table 1

[0058] Example 3 Example 4 Example 5 Comparative Example 1 F - content]]> 2.0 mg / L 3.1 mg / L 2.6 mg / L 12.4 mg / L F - removal rate 83.4％ 78.6％ 80.5％ 68.1％

[0059] As shown in Table 1, it is difficult to ensure that the F - content in the acid washing wastewater of high-purity quartz sand is less than 10 mg / L by using the method of multiple coagulation sedimentation, and the removal rate of fluorine ions can be significantly improved by using the method of coagulation sedimentation-adsorption combination, and the process is simple and the effect is good.

[0060] It should be noted that, in this text, relational terms such as first and second are used merely to distinguish one entity or action from another, and do not necessarily require or imply that there is any such actual relationship or order between these entities or actions. Moreover, the terms "include", "contain" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or equipment.

[0061] Although the embodiments of the present application have been shown and described, it can be understood by those of ordinary skill in the art that various changes, modifications, replacements and variations can be made to these embodiments without departing from the principles and spirits of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A process for treating high purity quartz sand pickling wastewater, characterized by, It comprises the following steps: S1. High-purity quartz sand acid washing wastewater is discharged into the raw water pool and stands for 12-18h; S2. Pumping to the neutralization pool, adding lime water to adjust the pH of the wastewater in the pool to 6.0-7.0; S3. Delivering the neutralized wastewater to the coagulation sedimentation pool, adding calcium chloride and PAC, coagulating and stirring for 20-30min, standing and depositing, and discharging the sludge to the sludge pool after deposition; S4. Discharging the coagulation sedimentation supernatant to the ion adsorption pool, starting stirring, adding adsorbent calcium aluminum hydrotalcite to the pool in 4-6 times for adsorption, and measuring the fluoride ion content until the fluoride ion content is lower than 5mg / L, stopping stirring and adsorption, the final adsorbent calcium aluminum hydrotalcite addition amount is 1.8-2.2g:1L of the coagulation sedimentation supernatant, the adsorption time is 4-6h, and the water quality meets the standard and is discharged to the discharge water pool; The preparation method of the adsorbent calcium aluminum hydrotalcite in S4 comprises the following steps: Mixing 100mL of calcium nitrate solution with 100mL of aluminum nitrate solution uniformly, adding 100mL of mixed alkali solution prepared by mixing sodium carbonate and sodium hydroxide dropwise at a rate of 2mL / min under stirring at 55-65℃, standing for 20min, adjusting the pH of the mixed alkali solution to maintain 11-12, placing under vacuum condition, aging at 45℃ for 12-15h, filtering and washing to neutral, freezing and drying for 18h, and calcining the adsorbent calcium aluminum hydrotalcite obtained by vacuum calcination at 400℃ for 2-3h under Ar protection.

2. The process for treating high purity quartz sand pickling wastewater according to claim 1, characterized in that, The concentration of lime water in S2 is 25%-30%, and the concentration of calcium chloride in S3 is 40% and the concentration of PAC is 15%.

3. The process for treating high purity quartz sand pickling wastewater according to claim 1, characterized in that, The stirring speed in S3 is 200r / min, and the stirring speed in S4 is 200r / min.

4. The process for treating high purity quartz sand pickling wastewater according to claim 1, characterized in that, The concentrations of the calcium nitrate solution and the aluminum nitrate solution are 0.25mol / L and 0.15mol / L, respectively.

5. The process for treating high purity quartz sand pickling wastewater according to claim 1, characterized in that, The molar ratio of sodium carbonate to sodium hydroxide is 0.2-0.3:0.

1.

6. The process for treating high purity quartz sand pickling wastewater according to claim 1, characterized in that, When preparing the adsorbent calcium aluminum hydrotalcite, the stirring rate is 500r / min.

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