Deep defluorination process for electrolyte chemical industry production wastewater

Abstract

The invention discloses a deep defluorination process for electrolyte chemical industry production wastewater, which comprises the following steps: feeding the electrolyte chemical industry production wastewater into a primary precipitation reaction tank, adding calcium salt and a coagulant aid to carry out initial defluorination precipitation reaction, and carrying out solid-liquid separation to obtain initial defluorination wastewater; feeding the initial defluorination wastewater into a Fenton oxidation reaction tank, adding a Fenton reagent for oxidation reaction, and filtering to obtain oxidized defluorination wastewater; and feeding the oxidized defluorination wastewater into a secondary precipitation reaction tank, adding calcium fluoride seed crystals and an inducer, carrying out a deep defluorination precipitation reaction, and carrying out solid-liquid separation to obtain deep defluorination wastewater. According to the deep fluorine removal process for the electrolyte chemical industry production wastewater, the fluorine content of effluent can be stably smaller than 1 mg / L, so that the effluent meets the discharge standard and even lower discharge requirements, the treatment cost can be reduced, and the defects that a traditional wastewater treatment technology is high in cost and secondary pollution exists are overcome.

Description

Technical Field

[0001] The invention belongs to the technical field of fluorine-containing wastewater treatment, and in particular relates to a deep defluorination process for electrolyte chemical production wastewater. Background Art

[0002] With the development of the electrolyte chemical industry, the fluorine-containing wastewater generated in its production process has posed a serious threat to the environment. Traditional defluorination methods often have problems such as low treatment efficiency, high cost, and difficulty in achieving deep defluorination standards, and cannot meet increasingly stringent environmental protection requirements.

[0003] For example, the common chemical precipitation method for defluoridation is to add chemical substances such as calcium chloride, calcium hydroxide or calcium oxide to fluoride-containing wastewater to form calcium fluoride precipitation with fluoride ions to achieve the purpose of defluoridation. However, calcium fluoride itself has a certain solubility and will dissolve with calcium hydroxide, which often leads to the fluoride content in the treated wastewater still being 20-30 mg / L, which is difficult to meet the discharge standards. There are also problems such as large sludge volume and serious secondary pollution. Calcium sulfate, calcium fluorosilicate and other precipitates are formed in the solution at the same time, adsorbed on the surface of calcium fluoride precipitation, hindering the formation of calcium fluoride precipitation. The calcium fluoride particles generated by the reaction are wrapped on the surface of the lime particles, hindering the further reaction of the precipitant inside the particles, reducing the use efficiency of calcium oxide. Therefore, it is often necessary to treat the wastewater twice or even multiple times to meet the discharge requirements.

[0004] Therefore, it is of great practical significance to develop an efficient, economical and stable deep defluorination treatment process for electrolyte chemical production wastewater. Summary of the invention

[0005] Based on the above technical problems, the present invention provides a deep defluorination process for electrolyte chemical production wastewater, which can not only stabilize the fluorine content of the effluent to less than 1 mg / L, thereby meeting the emission standards or even lower emission requirements, but also reduce the treatment cost, thereby overcoming the shortcomings of traditional wastewater treatment technology with high cost and secondary pollution.

[0006] The present invention proposes a deep defluorination process for electrolyte chemical production wastewater, comprising the following steps:

[0007] S1. The electrolyte chemical production wastewater is sent to a primary precipitation reaction tank, calcium salt and coagulant are added to perform an initial defluorination precipitation reaction, and initial defluorination wastewater is obtained after solid-liquid separation;

[0008] S2, sending the initial defluorination wastewater into a Fenton oxidation reaction tank, adding a Fenton reagent for oxidation reaction, and obtaining oxidized defluorination wastewater after filtration;

[0009] S3, sending the oxidative defluorination wastewater to a secondary precipitation reaction tank, adding calcium fluoride seeds and an inducer to carry out a deep defluorination precipitation reaction, and obtaining a deep defluorination wastewater after solid-liquid separation.

[0010] In the present invention, a calcium salt precipitation method is first used for preliminary fluorine removal, and calcium salt is used to form calcium fluoride precipitation with fluoride ions in wastewater to achieve fluorine removal. Since the calcium fluoride precipitation has a slow sedimentation rate and is difficult to filter, a coagulant is added to accelerate the precipitation formation and sedimentation rate, thereby improving the fluorine removal effect. Thereafter, an advanced oxidation method is used for further fluorine removal, and high molecular weight organic fluorides and inorganic fluorides in the wastewater are removed by Fenton oxidation reaction, while COD, suspended matter and chromaticity are removed. Finally, an induced crystallization method is used for deep fluorine removal, and calcium fluoride is added as a crystal seed, and an inducer is used to induce crystallization, and the fluoride ions remaining in the wastewater are induced to crystallize on the surface of the crystal seed to form calcium fluoride crystals, thereby further reducing the fluorine content in the wastewater and fully utilizing the calcium ions.

[0011] Preferably, in step S1, the calcium salt is at least one of calcium chloride, calcium hydroxide, calcium oxide or calcium sulfate;

[0012] Preferably, the molar ratio of calcium in the calcium salt to fluorine in the electrolyte chemical production wastewater is 1.5-2:1.

[0013] Preferably, in step S1, the coagulant aid is polyacrylamide or polyaluminium chloride;

[0014] Preferably, the amount of the coagulant aid added is 1-5 mg / L.

[0015] Preferably, in step S1, the initial defluorination precipitation reaction specifically comprises: firstly adding a calcium salt to generate calcium fluoride precipitation, and then adding a coagulant to promote the precipitation of calcium fluoride into agglomerates;

[0016] Preferably, the initial defluorination precipitation reaction time is 20-40 min, and the stirring rate is 30-50 r / min.

[0017] In the present invention, the initial defluorination precipitation reaction time is specifically 20-40 minutes, and the stirring speed is specifically 30-50 r / min, which ensures that the fluoride ions and calcium ions fully react to form precipitation.

[0018] Preferably, in step S2, the Fenton reagent is ferrous sulfate and hydrogen peroxide;

[0019] Preferably, the added amount of the Fenton reagent is 10-30 mg / L.

[0020] Preferably, in step S2, the filtration specifically includes: first performing multi-media filtration, then performing ultrafiltration, and finally performing reverse osmosis filtration.

[0021] In the present invention, after Fenton oxidation, multi-media filtration, ultrafiltration and reverse osmosis are continued to achieve further removal of COD, ammonia nitrogen, total phosphorus, total nitrogen and the like.

[0022] Preferably, in step S3, the inducing agent is aluminum sulfate or cation-activated aluminum hydroxide colloid;

[0023] Preferably, the calcium fluoride seed crystal addition amount is 1-3 g / L, and the inducer addition amount is 5-10 mg / L.

[0024] Preferably, the cation-activated aluminum hydroxide colloid is prepared by the following method: after aluminum sulfate and sodium hydroxide are subjected to solution reaction, an aqueous solution of hexadecyltrimethylammonium bromide is added and stirred and mixed, solid-liquid separation is performed, and vacuum drying is performed to obtain the cation-activated aluminum hydroxide colloid.

[0025] In the present invention, when the cation-activated aluminum hydroxide colloid is combined with calcium fluoride seed crystals to induce crystallization, on the one hand, the cation-activated aluminum hydroxide colloid can utilize electrostatic adsorption and Al 3+ With F - The strong affinity between them promotes the aggregation and precipitation of fluoride ions. On the other hand, the porous structure of the cation-activated aluminum hydroxide colloid itself has an adsorption effect, which makes the calcium fluoride precipitate adsorbed, and the final fluoride content in the effluent can be ≤0.5mg / L.

[0026] Preferably, in step S3, the deep defluorination precipitation reaction temperature is 20-30°C, the time is 30-60min, and the stirring rate is 10-20r / min.

[0027] In the present invention, the deep defluorination precipitation reaction temperature is 20-30°C, and the reaction time is 30-60min, so that the residual fluoride ions in the wastewater are induced to crystallize on the surface of the seed crystal to form calcium fluoride crystals, thereby further reducing the fluoride ion concentration in the wastewater; the stirring speed is 10-20r / min, and the reaction process is controlled to stir slowly, which promotes crystal growth and precipitation.

[0028] Preferably, in step S3, the fluorine content in the deep defluorination wastewater is ≤1 mg / L.

[0029] The beneficial effects of the present invention are as follows:

[0030] The present invention provides a deep defluorination process for electrolyte chemical production wastewater, which first uses calcium salt for pretreatment and then performs Fenton oxidation and induced crystallization for deep defluorination, thereby solving the problems of large amount of solid waste generated and incomplete defluorination in conventional precipitation methods, saving energy and water resources, achieving zero discharge of fluorine wastewater and resource recovery and reuse of calcium fluoride and sodium chloride salts in the wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1The figure is a schematic flow chart of the deep defluorination process for electrolyte chemical production wastewater according to the present invention. DETAILED DESCRIPTION

[0032] Hereinafter, the present invention will describe the technical solution in detail through specific embodiments, but it should be clearly stated that these embodiments are for illustration only and are not to be construed as limiting the scope of the present invention.

[0033] Example 1

[0034] Reference Figure 1 This embodiment proposes a deep defluorination process for electrolyte chemical production wastewater, comprising the following steps:

[0035] The electrolyte chemical production wastewater used in this embodiment has a fluorine content of 21.32 mg / L, a pH value of 4.23, and a COD content of 2186.5 mg / L;

[0036] (1) sending the electrolyte chemical production wastewater into a primary precipitation reaction tank, adding calcium chloride in an amount of 1.8 times the molar ratio of calcium to fluorine in the electrolyte chemical production wastewater for precipitation reaction, stirring at a rate of 40 r / min for 30 min, adding anionic polyacrylamide (PAM) during the reaction, and adding PAM in an amount of 3 mg / L. After completion, standing and settling, after solid-liquid separation by a centrifuge, obtaining initial defluorinated wastewater, and recovering the obtained calcium fluoride precipitate for calcium fluoride resource recovery;

[0037] (2) sending the above-mentioned initial defluorination wastewater into a Fenton oxidation reaction tank, adding ferrous sulfate solution (20wt%) and hydrogen peroxide (30wt%) for oxidation reaction, wherein the addition amount of ferrous sulfate solution (20wt%) is 10mg / L, and the addition amount of hydrogen peroxide (30wt%) is 10mg / L. After stirring and reacting for 2h, the wastewater after the oxidation reaction is first subjected to multi-media filtration, then to ultrafiltration, and finally to reverse osmosis filtration to obtain oxidized defluorination wastewater;

[0038] (3) The above-mentioned oxidative defluorination wastewater is sent to a secondary precipitation reaction tank, and calcium fluoride seeds and aluminum sulfate are added to induce crystallization precipitation. The amount of calcium fluoride seeds added is 2 g / L, and the amount of aluminum sulfate added is 8 mg / L. The induced crystallization precipitation reaction temperature is 25°C, the time is 50 min, and the stirring rate is 15 r / min. After completion, it is allowed to stand and settle. After solid-liquid separation by a centrifuge, high-purity calcium fluoride and deep fluoride precipitation wastewater are obtained. After testing, the fluorine content of the deep defluorination wastewater is 0.89 mg / L, and the COD content is 102.4 mg / L.

[0039] Example 2

[0040] Reference Figure 1 This embodiment proposes a deep defluorination process for electrolyte chemical production wastewater, comprising the following steps:

[0041] The electrolyte chemical production wastewater used in this embodiment has a fluoride ion content of 21.32 mg / L, a pH value of 4.23, and a COD content of 2186.5 mg / L;

[0042] (1) sending the electrolyte chemical production wastewater into a primary precipitation reaction tank, adding calcium hydroxide in an amount of calcium 1.5 times the molar ratio of fluorine in the electrolyte chemical production wastewater for precipitation reaction, stirring at a rate of 50 r / min for 20 min, adding anionic polyacrylamide (PAM) during the reaction, and adding PAM in an amount of 5 mg / L. After completion, standing and settling, after solid-liquid separation by a centrifuge, obtaining initial defluorinated wastewater, and recovering the obtained calcium fluoride precipitate for calcium fluoride resource recovery;

[0043] (2) sending the above-mentioned initial defluorination wastewater into a Fenton oxidation reaction tank, adding ferrous sulfate solution (20wt%) and hydrogen peroxide (30wt%) for oxidation reaction, wherein the addition amount of ferrous sulfate solution (20wt%) is 5mg / L, and the addition amount of hydrogen peroxide (30wt%) is 25mg / L. After stirring and reacting for 2h, the wastewater after the oxidation reaction is first subjected to multi-media filtration, then to ultrafiltration, and finally to reverse osmosis filtration to obtain oxidized defluorination wastewater;

[0044] (3) The above-mentioned oxidative defluorination wastewater is sent to a secondary precipitation reaction tank, and calcium fluoride seeds and aluminum sulfate are added to induce crystallization precipitation. The amount of calcium fluoride seeds added is 1 g / L, and the amount of aluminum sulfate added is 10 mg / L. The induced crystallization precipitation reaction temperature is 20°C, the time is 60 min, and the stirring rate is 10 r / min. After completion, it is allowed to stand and settle. After solid-liquid separation by a centrifuge, high-purity calcium fluoride and deep fluoride precipitation wastewater are obtained. After testing, the fluorine content of the deep defluorination wastewater is 0.98 mg / L, and the COD content is 90.9 mg / L.

[0045] Example 3

[0046] Reference Figure 1 This embodiment proposes a deep defluorination process for electrolyte chemical production wastewater, comprising the following steps:

[0047] The electrolyte chemical production wastewater used in this embodiment has a fluoride ion content of 21.32 mg / L, a pH value of 4.23, and a COD content of 2186.5 mg / L;

[0048] (1) sending the electrolyte chemical production wastewater into a primary precipitation reaction tank, adding calcium chloride in an amount of calcium twice the molar ratio of fluorine in the electrolyte chemical production wastewater for precipitation reaction, the stirring rate is 30r / min, the time is 40min, anionic polyacrylamide (PAC) is added during the reaction, and the amount of PAC added is 1mg / L. After completion, the reaction is allowed to stand and settle, and after solid-liquid separation by a centrifuge, an initial defluorinated wastewater is obtained, and the obtained calcium fluoride precipitate is recycled as a calcium fluoride resource;

[0049] (2) sending the above-mentioned initial defluorination wastewater into a Fenton oxidation reaction tank, adding ferrous sulfate solution (20wt%) and hydrogen peroxide (30wt%) for oxidation reaction, wherein the addition amount of ferrous sulfate solution (20wt%) is 5mg / L, and the addition amount of hydrogen peroxide (30wt%) is 5mg / L. After stirring and reacting for 2h, the wastewater after the oxidation reaction is first subjected to multi-media filtration, then to ultrafiltration, and finally to reverse osmosis filtration to obtain oxidized defluorination wastewater;

[0050] (3) The above-mentioned oxidative defluorination wastewater is sent to a secondary precipitation reaction tank, and calcium fluoride seeds and aluminum sulfate are added to induce crystallization precipitation. The amount of calcium fluoride seeds added is 3g / L, and the amount of aluminum sulfate added is 5mg / L. The induced crystallization precipitation reaction temperature is 30°C, the time is 30min, and the stirring rate is 20r / min. After completion, it is allowed to stand and settle. After solid-liquid separation by a centrifuge, high-purity calcium fluoride and deep fluoride precipitation wastewater are obtained. After testing, the fluorine content of the deep defluorination wastewater is 0.91mg / L, and the COD content is 123.2mg / L.

[0051] Example 4

[0052] Reference Figure 1 This embodiment proposes a deep defluorination process for electrolyte chemical production wastewater, comprising the following steps:

[0053] The electrolyte chemical production wastewater used in this embodiment has a fluorine content of 21.32 mg / L, a pH value of 4.23, and a COD content of 2186.5 mg / L;

[0054] (1) sending the electrolyte chemical production wastewater into a primary precipitation reaction tank, adding calcium chloride in an amount of 1.8 times the molar ratio of calcium to fluorine in the electrolyte chemical production wastewater for precipitation reaction, stirring at a rate of 40 r / min for 30 min, adding anionic polyacrylamide (PAM) during the reaction, and adding PAM in an amount of 3 mg / L. After completion, standing and settling, after solid-liquid separation by a centrifuge, obtaining initial defluorinated wastewater, and recovering the obtained calcium fluoride precipitate for calcium fluoride resource recovery;

[0055] (2) sending the above-mentioned initial defluorination wastewater into a Fenton oxidation reaction tank, adding ferrous sulfate solution (20wt%) and hydrogen peroxide (30wt%) for oxidation reaction, wherein the addition amount of ferrous sulfate solution (20wt%) is 10mg / L, and the addition amount of hydrogen peroxide (30wt%) is 10mg / L. After stirring and reacting for 2h, the wastewater after the oxidation reaction is first subjected to multi-media filtration, then to ultrafiltration, and finally to reverse osmosis filtration to obtain oxidized defluorination wastewater;

[0056] (3) The above-mentioned oxidative defluorination wastewater is sent to a secondary precipitation reaction tank, and calcium fluoride seeds and cation-activated aluminum hydroxide colloid are added to induce crystallization precipitation. The amount of calcium fluoride seeds added is 2 g / L, and the amount of cation-activated aluminum hydroxide colloid added is 8 mg / L. The induced crystallization precipitation reaction temperature is 25°C, the time is 50 min, and the stirring rate is 15 r / min. After completion, it is allowed to stand and precipitate, and then separated by solid-liquid separation by a centrifuge to obtain high-purity calcium fluoride and deep fluoride precipitation wastewater.

[0057] The cation-activated aluminum hydroxide colloid is prepared by the following method: dissolving aluminum sulfate in deionized water, adding a 100 g / L NaOH solution under stirring until the pH value of the solution is 5.0 and then stopping the addition, stirring and reacting for 24 hours, adding a 2 g / L hexadecyltrimethylammonium bromide solution, stirring and reacting for 6 hours, separating the solid and liquid by a centrifuge, placing in a vacuum drying oven and drying at 95° C. for 12 hours, and obtaining the cation-activated aluminum hydroxide colloid;

[0058] After testing, the fluoride content of deep defluorination wastewater was 0.46 mg / L and the COD content was 97.5 mg / L.

[0059] Comparative Example 1

[0060] Reference Figure 1 This embodiment proposes a deep defluorination process for electrolyte chemical production wastewater, comprising the following steps:

[0061] The electrolyte chemical production wastewater used in this embodiment has a fluorine content of 21.32 mg / L, a pH value of 4.23, and a COD content of 2186.5 mg / L;

[0062] (1) sending the electrolyte chemical production wastewater into a primary precipitation reaction tank, adding calcium chloride in an amount of 1.8 times the molar ratio of calcium to fluorine in the electrolyte chemical production wastewater for precipitation reaction, stirring at a rate of 40 r / min for 30 min, adding anionic polyacrylamide (PAM) during the reaction, and adding PAM in an amount of 3 mg / L. After completion, standing and settling, after solid-liquid separation by a centrifuge, obtaining initial defluorinated wastewater, and recovering the obtained calcium fluoride precipitate for calcium fluoride resource recovery;

[0063] (2) sending the above-mentioned initial defluorination wastewater into a Fenton oxidation reaction tank, adding ferrous sulfate solution (20wt%) and hydrogen peroxide (30wt%) for oxidation reaction, wherein the addition amount of ferrous sulfate solution (20wt%) is 10mg / L, and the addition amount of hydrogen peroxide (30wt%) is 10mg / L. After stirring and reacting for 2h, the wastewater after the oxidation reaction is first subjected to multi-media filtration, then to ultrafiltration, and finally to reverse osmosis filtration to obtain oxidized defluorination wastewater;

[0064] (3) The above-mentioned oxidative defluorination wastewater is sent to a secondary precipitation reaction tank, and calcium fluoride seeds and aluminum hydroxide colloid are added to induce crystallization precipitation. The amount of calcium fluoride seeds added is 2 g / L, and the amount of aluminum hydroxide colloid added is 8 mg / L. The induced crystallization precipitation reaction temperature is 25°C, the time is 50 min, and the stirring rate is 15 r / min. After completion, it is allowed to stand and settle, and then separated by solid-liquid separation by a centrifuge to obtain high-purity calcium fluoride and deep fluoride precipitation wastewater.

[0065] The aluminum hydroxide colloid is prepared by the following method: dissolving aluminum sulfate in deionized water, adding a 100 g / L NaOH solution under stirring until the pH value of the solution is 5.0 and then stopping the addition, stirring and reacting for 24 hours, separating the solid and liquid by a centrifuge, and drying in a vacuum drying oven at 95° C. for 12 hours to obtain the aluminum hydroxide colloid;

[0066] After testing, the fluoride content of deep defluorination wastewater was 1.81 mg / L and the COD content was 101.4 mg / L.

[0067] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A deep defluorination process for electrolyte chemical production wastewater, characterized in that: The steps include: S1. The electrolyte chemical production wastewater is sent to a primary precipitation reaction tank, calcium salt and coagulant are added to perform an initial defluorination precipitation reaction, and initial defluorination wastewater is obtained after solid-liquid separation; S2, sending the initial defluorination wastewater into a Fenton oxidation reaction tank, adding a Fenton reagent for oxidation reaction, and obtaining oxidized defluorination wastewater after filtration; S3, sending the oxidative defluorination wastewater to a secondary precipitation reaction tank, adding calcium fluoride seeds and an inducer to carry out a deep defluorination precipitation reaction, and obtaining a deep defluorination wastewater after solid-liquid separation.

2. The deep defluorination process for electrolyte chemical production wastewater according to claim 1, characterized in that: In step S1, the calcium salt is at least one of calcium chloride, calcium hydroxide, calcium oxide or calcium sulfate; Preferably, the molar ratio of calcium in the calcium salt to fluorine in the electrolyte chemical production wastewater is 1.5-2:

1.

3. The deep defluorination process for electrolyte chemical production wastewater according to claim 1 or 2, characterized in that: In step S1, the coagulant aid is polyacrylamide or polyaluminium chloride; Preferably, the amount of the coagulant aid added is 1-5 mg / L.

4. The deep defluorination process for electrolyte chemical production wastewater according to any one of claims 1 to 3, characterized in that: In step S1, the initial defluorination precipitation reaction specifically includes: firstly adding calcium salt to generate calcium fluoride precipitation, and then adding a coagulant to promote the precipitation of calcium fluoride into agglomerates; Preferably, the initial defluorination precipitation reaction time is 20-40 min, and the stirring rate is 30-50 r / min.

5. The deep defluorination process for electrolyte chemical production wastewater according to any one of claims 1 to 4, characterized in that: In step S2, the Fenton reagent is ferrous sulfate and hydrogen peroxide; Preferably, the amount of Fenton's reagent added is 10-30 mg / L.

6. The deep defluorination process for electrolyte chemical production wastewater according to any one of claims 1 to 5, characterized in that: In step S2, the filtration specifically includes: firstly performing multi-media filtration, then performing ultrafiltration, and finally performing reverse osmosis filtration.

7. The deep defluorination process for electrolyte chemical production wastewater according to any one of claims 1 to 6, characterized in that: In step S3, the inducing agent is aluminum sulfate or cation-activated aluminum hydroxide colloid; Preferably, the calcium fluoride seed crystal addition amount is 1-3 g / L, and the inducer addition amount is 5-10 mg / L.

8. The deep defluorination process for electrolyte chemical production wastewater according to claim 7, characterized in that: The cation-activated aluminum hydroxide colloid is prepared by the following method: aluminum sulfate and sodium hydroxide are subjected to solution reaction, and then a hexadecyltrimethylammonium bromide aqueous solution is added and stirred and mixed, and after solid-liquid separation, vacuum drying is performed to obtain the cation-activated aluminum hydroxide colloid.

9. The deep defluorination process for electrolyte chemical production wastewater according to any one of claims 1 to 8, characterized in that: In step S3, the deep defluorination precipitation reaction temperature is 20-30°C, the time is 30-60min, and the stirring rate is 10-20r / min.

10. The deep defluorination process for electrolyte chemical production wastewater according to any one of claims 1 to 9, characterized in that: In step S3, the fluorine content in the deep defluorination wastewater is ≤1 mg / L.

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