Method for treating inorganic fluoride waste solutions

Abstract

This application relates to the technical field of waste liquid treatment, specifically disclosing a method for treating inorganic fluoride waste liquid. The treatment method includes the following steps: S1: Pumping the pre-filtered waste liquid into a seed crystal circulation reactor, adding calcium salt, and mixing to obtain treatment liquid A and precipitate A; the seed crystal circulation reactor contains calcium sulfate dihydrate seeds; S2: Taking treatment liquid A, adjusting the pH, mixing, first adding magnesium salt, then calcium salt, then adding flocculant, and mixing to obtain treatment liquid B and precipitate B; S3: Taking treatment liquid B, adjusting the pH, adding sulfide, and mixing to obtain treatment liquid C and precipitate C; S4: Taking treatment liquid C, adjusting the pH, adding phosphate and magnesium salt, and mixing to obtain treatment liquid D and precipitate D; S5: Taking treatment liquid D, adjusting the pH, adding adsorbent, and mixing to obtain an aqueous solution and precipitate E. The treatment method of this application can effectively remove fluorides.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of waste liquid treatment, and more particularly to a treatment method of inorganic fluoride waste liquid. BACKGROUND

[0002] In the process of semiconductor wafer manufacturing, chemicals such as hydrofluoric acid, sulfuric acid and ammonia are usually used for cleaning, thereby generating complex comprehensive fluoride-containing wastewater. Such waste liquid usually contains high concentrations of fluorosilicate, sulfate, ammonium ions and heavy metal ions such as copper and nickel, and presents complex characteristics of coexistence of high salinity, high ammonia nitrogen, high fluoride and heavy metal toxicity.

[0003] At present, the treatment methods for fluoride-containing wastewater mainly include precipitation method, adsorption method and membrane separation method. In the prior art, each method has significant limitations in treating wafer cleaning waste liquid. The precipitation method: a) calcium ions will preferentially react with sulfate ions to form calcium sulfate scale, which not only causes reagent waste, but also easily causes reactor and pipeline scaling, and calcium fluoride precipitation easily covers the surface of particles, reducing the precipitation efficiency and increasing the reagent dosage; b) it is difficult to stably reduce the fluoride ions to below 10 mg / L, and a large amount of heavy metal-containing sludge is generated, which easily causes secondary pollution. Although the adsorption method can deeply remove fluoride, the adsorption capacity is limited, and the regeneration is frequent and the operation cost is high. Although the membrane separation method can produce high-quality clean water, the pretreatment requirements for the influent are extremely high, the membrane assembly is easily scaled and contaminated, and concentrated liquid that needs further treatment is generated, which limits its large-scale application due to the investment and operation cost.

[0004] The patent application file with publication number CN85101146A discloses a method for closed system circulation treatment of waste liquid containing ammonium ions and fluoride ions, which comprises ion exchange adsorption with strong acid type ion exchange resin to separate ammonium ions, if necessary, distillation method is used to concentrate the remaining dilute hydrogen fluoride solution: concentrated sulfuric acid is added for extractive distillation, hydrogen fluoride is recovered, the remaining dilute sulfuric acid is concentrated, and then recycled to the above extractive distillation process; the ion exchange resin adsorbed with ammonium ions is regenerated with an aqueous solution of hydrochloric acid, and the ion exchange resin from which the ammonium ions are removed is used again to desorb ammonium ions; magnesium hydroxide is added, and the remaining ammonium chloride aqueous solution is distilled to recover ammonia water; hydrolysis heating decomposition method is used to recover hydrochloric acid from the remaining solution containing magnesium chloride; the recovered hydrochloric acid is recycled in the ion exchange resin regeneration process, and the recovered magnesium hydroxide is recycled in the process of distilling ammonia water from the ammonium chloride solution.

[0005] In the technical solution, although it is intended to realize resource utilization through closed circulation, the whole process flow is complex, and depends on the serial coupling of multiple high-energy consumption unit operations such as ion exchange, extractive distillation and pyrolysis hydrolysis, which not only causes large equipment investment, but also causes high running cost due to the inherent high energy consumption characteristics of distillation and pyrolysis processes, which seriously restricts the economic feasibility of the scheme in industrial application. SUMMARY

[0006] In order to solve the above technical problems, the present application provides a treatment method of inorganic fluoride waste liquid.

[0007] The present application provides a treatment method of inorganic fluoride waste liquid, which adopts the following technical scheme:

[0008] A treatment method of inorganic fluoride waste liquid, comprising the following steps:

[0009] S1: Pumping the pre-filtered waste liquid into a seed circulating reactor, adding calcium salt, mixing for 30-40 min, and then separating the solid and liquid to obtain treatment liquid A and precipitate A; the seed circulating reactor is placed with calcium sulfate dihydrate seed;

[0010] S2: Taking the treatment liquid A, adjusting the pH to 8.5-9.0, mixing for 30-40 min, first adding magnesium salt, then adding calcium salt, and then adding flocculant, mixing for 15-25 min, and then separating the solid and liquid to obtain treatment liquid B and precipitate B;

[0011] S3: Taking the treatment liquid B, adjusting the pH to 8.5-9.0, adding sulfide, mixing for 30-40 min, and then separating the solid and liquid to obtain treatment liquid C and precipitate C;

[0012] S4: Taking the treatment liquid C, adjusting the pH to 8.5-9.5, adding phosphate and magnesium salt, mixing for 30-40 min, and then separating the solid and liquid to obtain treatment liquid D and precipitate D;

[0013] S5: Taking the treatment liquid D, adjusting the pH to 7.0-7.5, adding adsorbent, mixing for 30-40 min, and then separating the solid and liquid to obtain effluent and precipitate E;

[0014] In step S1, the molar concentration ratio of calcium ions in the calcium salt to SO4 2- in the waste liquid is (1.05-1.1):1;

[0015] In step S2, the total molar number of magnesium ions and calcium ions in the magnesium salt and calcium salt is (0.45-0.47):1 to the total molar number of fluoride ions and fluoride ions after hydrolysis of fluorosilicate ions in the waste liquid;

[0016] The calcium salt is calcium chloride dihydrate; and the magnesium salt is magnesium chloride hexahydrate;

[0017] The flocculant is anionic polyacrylamide;

[0018] The adsorbent is selected from any one of polyaluminum chloride and hydroxyapatite.

[0019] Preferably, the pH of the pre-filtered waste liquid is about 3±0.5.

[0020] In this scheme, first, under acidic conditions, the seed circulating reactor is used to induce the preferential precipitation of calcium sulfate, thereby avoiding the risk of system fouling from the source and reducing the interference of competitive ions for subsequent fluoride removal. Subsequently, switching to a strong alkaline environment, the complete hydrolysis of fluorosilicate complex is realized, and the magnesium salt co-precipitation strategy is introduced, which effectively improves the settling performance of calcium fluoride precipitation by forming mixed crystal phases of MgF2 and CaF2, thereby completing the simultaneous removal of fluorine and silicon. On this basis, in a weak alkaline system, heavy metal ions are deeply precipitated and fixed by adding sulfides; then, using the struvite crystallization method, ammonium nitrogen is recovered in the form of magnesium ammonium phosphate, realizing the recycling of waste. Finally, through the adsorption and ion exchange of the adsorbent on the residual trace pollutants, the deep purification and quality assurance of the effluent are completed.

[0021] Preferably, before the phosphate is added, a step of adding a carbonate is further included in the step S4.

[0022] Preferably, the carbonate is sodium carbonate.

[0023] In this scheme, sodium carbonate can pre-removal of residual calcium ions in the system, avoiding the subsequent generation of calcium phosphate by-product precipitation with phosphate, thereby preventing the invalid consumption of phosphate.

[0024] Preferably, the calcium salt is calcium chloride dihydrate.

[0025] Preferably, the sulfide is sodium sulfide nonahydrate.

[0026] Preferably, the phosphate is disodium hydrogen phosphate dodecahydrate.

[0027] Preferably, the magnesium salt is magnesium chloride hexahydrate.

[0028] Preferably, the hydroxyapatite is a supported hydroxyapatite.

[0029] Preferably, the supported hydroxyapatite is selected from any one of polyacrylamide gel supported hydroxyapatite and magnetic carrier supported hydroxyapatite.

[0030] In this scheme, the polyacrylamide gel provides a stable carrier skeleton for hydroxyapatite through its three-dimensional network structure, so that the adsorbent maintains regular morphology and excellent hydraulic characteristics; the magnetic carrier realizes rapid separation after adsorption through its magnetic component. Both structures effectively increase the active surface of hydroxyapatite, and realize the recycling of the adsorbent under the support of the carrier skeleton.

[0031] Preferably, the preparation method of the polyacrylamide gel supported hydroxyapatite comprises the following steps:

[0032] Under inert atmosphere, acrylamide monomer and hydroxyapatite suspension with solid content of 5-7% are taken in mass ratio (10-15):(85-90), crosslinking agent is added, temperature is raised to 50-60℃, initiator and polymerization accelerator are added, reaction is carried out for 50-60 min, aging, washing, granulation, drying are carried out, and polyacrylamide gel loaded hydroxyapatite is obtained.

[0033] Preferably, the crosslinking agent is N,N'-methylenebisacrylamide.

[0034] Preferably, the amount of the crosslinking agent is 0.5-1.0% of the mass of acrylamide monomer.

[0035] Preferably, the polymerization accelerator is N,N,N',N'-tetramethylethylenediamine.

[0036] Preferably, the amount of the polymerization accelerator is 0.3-0.5% of the mass of acrylamide monomer.

[0037] Preferably, the initiator is ammonium persulfate.

[0038] Preferably, the amount of the initiator is 0.5-1% of the mass of acrylamide monomer.

[0039] In the scheme, hydroxyapatite nanoparticles are dispersed in water to form a stable suspension system, then acrylamide monomer is polymerized under the action of crosslinking agent, initiator and polymerization accelerator to form a three-dimensional network structure of hydrogel, which limits and uniformly disperses the hydroxyapatite nanocrystals; finally, through aging, washing, granulation and drying processes, a composite adsorption material with regular morphology and excellent hydraulic characteristics is obtained.

[0040] Preferably, the preparation method of the magnetic carrier loaded hydroxyapatite comprises the following steps:

[0041] S11: under inert atmosphere, magnetic Fe3O4 is dispersed in aqueous ethanol solution, pH is adjusted to 9.5-10.0, tetraethyl orthosilicate is added, temperature is raised to 50-60℃, reaction is carried out for 2-3 h, solid-liquid separation is carried out, washing is carried out, drying is carried out, and Fe3O4@SiO2 is obtained;

[0042] S12: under inert atmosphere, Fe3O4@SiO2 is dispersed in water, pH is adjusted to 10-10.5, temperature is raised to 75-85℃, calcium salt and phosphate are added, reaction is carried out for 3-4 h, solid-liquid separation is carried out, washing is carried out, drying is carried out, and the magnetic carrier loaded hydroxyapatite is obtained.

[0043] Preferably, the mass ratio of the magnetic Fe3O4 and tetraethyl orthosilicate is 1:(0.1-0.2).

[0044] Preferably, the mass ratio of Fe3O4@SiO2, calcium salt, and phosphate is 1:(0.6~0.9):(0.9~1.3).

[0045] In this scheme, magnetic Fe3O4 is first used as the core, and a layer of silica is coated on its surface through the hydrolysis-condensation reaction of tetraethyl orthosilicate under alkaline conditions to form a Fe3O4@SiO2 composite carrier. Subsequently, under inert atmosphere and mild hydrothermal conditions, Fe3O4@SiO2 is dispersed in water. By adjusting the pH to alkaline and controlling the molar ratio of calcium salt to phosphate to be close to 1.67, calcium ions and phosphate ions precipitate and crystallize in situ on the surface of the SiO2 layer, gradually growing to form a hydroxyapatite active layer.

[0046] Preferably, step S1 further includes adding polyaspartic acid or hydroxyethylidene diphosphonic acid to the seed crystal circulation reactor before or during the addition of calcium salt.

[0047] In this solution, polyaspartic acid or hydroxyethylidene diphosphonic acid can selectively adsorb onto specific crystal faces of gypsum crystals, inhibiting their development into needle-like or plate-like shapes and promoting the formation of denser and more regular short columnar crystals. This greatly improves sedimentation and filtration performance and reduces adhesion on equipment.

[0048] Preferably, in step S1, when or before adding the calcium salt, the step of adding sodium dodecylbenzenesulfonate to the seed crystal circulation reactor is also included.

[0049] In this scheme, sodium dodecylbenzenesulfonate can reduce the surface tension of the solution and change the interfacial energy between the crystal and the reactor wall, thus physically weakening the adhesion of the crystal to the wall. This makes it easier for the formed micro-crystal nuclei to be flushed off by the fluid and return to the main solution to grow on the seed crystals, thereby enhancing the scale prevention effect.

[0050] In summary, this application has the following beneficial effects:

[0051] Based on the acidity of the waste liquid itself, this application first uses seed crystal circulation to remove a large amount of sulfate ions, and then achieves efficient precipitation of fluorosilicate and fluoride through the synergistic precipitation effect of magnesium salt and calcium salt. On this basis, heavy metal ions are removed by sulfide in sequence, and ammonium nitrogen (mainly struvite) is efficiently precipitated and recycled by magnesium salt and phosphate. Finally, adsorbent is used for deep purification. Detailed Implementation

[0052] The present application will be further described in detail below with reference to the embodiments.

[0053] Unless otherwise specified, the raw materials used in the embodiments and comparative examples of this application are all commercially available.

[0054] The molecular weight of anionic polyacrylamide is 8 million to 10 million;

[0055] The volume fraction of the ethanol-water solution is 75%.

[0056] In the following embodiments, the waste liquid is the waste liquid generated during the wafer cleaning process, and its main water quality parameters are as follows: SiF6 2- 169 mg / L; F - 45 mg / L; Soluble silicon (as SiO2): 53 mg / L; SO4 2- : 1100 mg / L; Ammonium nitrogen: 203 mg / L; Na + 29 mg / L; Cu 2+ 10 mg / L; Ni 2+ : 25mg / L; suspended solids: 46mg / L; pH at 25℃±2℃ is approximately 3.0±0.5; the above waste liquid undergoes the following pretreatment before subsequent treatment: pre-filtration through a ceramic microfiltration membrane module to remove suspended solids, and then set aside for use.

[0057] Reagent dosage (in actual operation, the dosage is scaled proportionally based on the ion concentration, and can fluctuate within 10%):

[0058] In step S1, calcium ions in calcium chloride dihydrate react with SO42-. 2- The molar concentration ratio is (1.05~1.1):1, and the dosage of calcium chloride dihydrate is (1770~1850) mg / L;

[0059] The dosage of polyaspartic acid or hydroxyethylidene diphosphonic acid is (0.2~0.5) g / L;

[0060] The dosage of sodium dodecylbenzenesulfonate is (0.1~0.2) g / L;

[0061] In step S2, the ratio of the total molar number of magnesium ions and calcium ions to the total molar number of fluoride ions after hydrolysis of magnesium chloride hexahydrate and calcium chloride dihydrate is (0.45~0.47):1, the amount of magnesium chloride hexahydrate used is (30~50) mg / L, and the amount of calcium chloride dihydrate used is (600~620) mg / L;

[0062] The dosage of anionic polyacrylamide is (0.5~1) mg / L;

[0063] In step S3, the molar concentration ratio of sodium sulfide nonahydrate to copper ions and nickel ions is (1.05~1.1):1, and the amount of sodium sulfide nonahydrate used is (147~154) mg / L.

[0064] In step S4, the amount of sodium carbonate used is (0.1~0.2) g / L;

[0065] The molar ratio of disodium hydrogen phosphate dodecahydrate, magnesium chloride hexahydrate, and ammonium nitrogen is 1.05:1:(1.05~1.1), the amount of disodium hydrogen phosphate dodecahydrate is (4.95~5.20) g / L, and the amount of magnesium chloride hexahydrate is (2.68~2.80) g / L.

[0066] In step S5, the amount of adsorbent used is (0.2~0.35) g / L.

[0067] Preparation Examples 1-2: Polyacrylamide gel supported on hydroxyapatite

[0068] Preparation Example 1

[0069] The preparation method of polyacrylamide gel-supported hydroxyapatite in this example includes the following steps:

[0070] S11: Add 10g of hydroxyapatite to 190g of deionized water, add 0.03g of sodium hexametaphosphate, and then transfer to an ultrasonic device. Under cooling conditions, ultrasonically treat for 30 minutes at a frequency of 20KHz and a power of 300W to obtain a suspension.

[0071] S12: Under a nitrogen atmosphere, acrylamide and suspension were mixed evenly at a mass ratio of 10:90. Then, 0.5% N,N'-methylenebisacrylamide (by mass of acrylamide) was added and stirred until evenly mixed. The mixture was heated to 50°C, and then 0.5% ammonium persulfate (by mass of acrylamide) and 0.3% N,N,N',N'-tetramethylethylenediamine (by mass of acrylamide) were added. After stirring and mixing evenly, the mixture was reacted for 60 min and aged at 25°C for 12 h. The mixture was washed twice with deionized water and once with anhydrous ethanol, pulverized, and dried at 50°C to constant weight to obtain polyacrylamide gel-supported hydroxyapatite.

[0072] The particle size distribution of hydroxyapatite is 50~100nm.

[0073] Preparation Example 2

[0074] The preparation method of polyacrylamide gel-supported hydroxyapatite in this example includes the following steps:

[0075] S11: Add 14g of hydroxyapatite to 186g of deionized water, add 0.052g of sodium hexametaphosphate, and then transfer to an ultrasonic device. Under cooling conditions, ultrasonically treat for 30 minutes at a frequency of 20KHz and a power of 300W to obtain a suspension.

[0076] S12: Under a nitrogen atmosphere, acrylamide and suspension were mixed evenly at a mass ratio of 15:85. Then, 1.0% of N,N'-methylenebisacrylamide by mass of acrylamide was added and stirred evenly. The mixture was heated to 60°C, and 1.0% of ammonium persulfate and 0.5% of N,N,N',N'-tetramethylethylenediamine by mass of acrylamide were added. After stirring evenly, the mixture was reacted for 50 min and aged at 25°C for 12 h. The mixture was washed twice with deionized water and once with anhydrous ethanol, pulverized, and dried at 50°C to constant weight to obtain polyacrylamide gel-supported hydroxyapatite.

[0077] The particle size distribution of hydroxyapatite is 50~100nm.

[0078] Preparation Examples 3-4: Magnetic Support for Hydroxyapatite

[0079] Preparation Example 3

[0080] The preparation method of magnetic support for hydroxyapatite in this example includes the following steps:

[0081] Under a nitrogen atmosphere, 3g of magnetic Fe3O4 nanoparticles were added to an ethanol aqueous solution and stirred at 500 rpm for 40 min. The pH was adjusted to 9.5 with 5% ammonia. Then, 0.3g of tetraethyl orthosilicate was slowly added, the temperature was raised to 50℃, and the reaction was stirred for 2 h. The magnets were then separated, washed three times with anhydrous ethanol, and dried at 60℃ to constant weight to obtain Fe3O4@SiO2.

[0082] Under a nitrogen atmosphere, 3 g of Fe3O4@SiO2 was added to deionized water and stirred at 500 rpm for 40 min. The pH was adjusted to 10.0 with 5% ammonia water. The temperature was raised to 75 °C, and 1.85 g of calcium chloride dihydrate and 2.7 g of disodium hydrogen phosphate dodecahydrate were slowly added. The mixture was reacted at a constant temperature for 3 h, cooled naturally to room temperature, separated by magnets, washed with deionized water until neutral, and dried at 80 °C to constant weight to obtain hydroxyapatite supported on a magnetic carrier.

[0083] Preparation Example 4

[0084] The preparation method of magnetic support for hydroxyapatite in this example includes the following steps:

[0085] Under a nitrogen atmosphere, 3g of magnetic Fe3O4 nanoparticles were added to an ethanol aqueous solution and stirred at 500 rpm for 40 min. The pH was adjusted to 10.0 with 5% ammonia water. Then, 0.6g of tetraethyl orthosilicate was slowly added, the temperature was raised to 60℃, and the reaction was stirred for 3 h. The magnets were then separated, washed three times with anhydrous ethanol, and dried at 60℃ to constant weight to obtain Fe3O4@SiO2.

[0086] Under a nitrogen atmosphere, 3 g of Fe3O4@SiO2 was added to deionized water and stirred at 500 rpm for 40 min. The pH was adjusted to 10.5 with 5% ammonia water. The temperature was raised to 85 °C, and 2.67 g of calcium chloride dihydrate and 3.9 g of disodium hydrogen phosphate dodecahydrate were slowly added. The mixture was reacted at a constant temperature for 4 h, cooled naturally to room temperature, separated by magnets, washed with deionized water until neutral, and dried at 80 °C to constant weight to obtain hydroxyapatite supported on a magnetic carrier.

[0087] Example 1

[0088] The method for treating inorganic fluoride waste liquid in this embodiment includes the following steps:

[0089] S1: Pump 10L of pre-filtered waste liquid into a circulating reactor containing 200g of calcium sulfate dihydrate seed crystals. While maintaining the pH of the system at approximately 3.5, slowly add an aqueous solution containing 17.7g of calcium chloride. Mix at 200rpm for 40min, filter, and obtain treated liquid A and precipitate A.

[0090] S2: Take treatment solution A, adjust the pH to 8.5 with 1 mol / L sodium hydroxide solution, mix at 300 rpm for 35 min, first add an aqueous solution containing 300 mg of magnesium chloride hexahydrate, continue stirring for 12 min, then add an aqueous solution containing 6.2 g of calcium chloride, mix at 200 rpm for 25 min, finally add 5 mg of anionic polyacrylamide, mix at 50 rpm for 15 min, filter, and obtain treatment solution B and precipitate B;

[0091] S3: Take the treatment solution B, finely adjust the pH to 8.5, then add an aqueous solution containing 1.47g of sodium sulfide, mix at 200rpm for 35min, filter, and obtain treatment solution C and precipitate C.

[0092] S4: Take the treatment solution C, first add an aqueous solution containing 49.5g of disodium hydrogen phosphate dodecahydrate, mix at 200rpm for 3min, then add an aqueous solution containing 26.8g of magnesium chloride hexahydrate, and dynamically adjust the pH to 9.0 using 0.5mol / L sodium hydroxide solution, mix at 200rpm for 40min, filter, and obtain treatment solution D and precipitate D;

[0093] S5: Take the treatment solution D, adjust the pH to 7.0 with 0.5mol / L dilute hydrochloric acid, add 2.0g of polyaluminum chloride, mix at 150rpm for 30min, filter, and obtain the aqueous solution and precipitate E.

[0094] The water solution was tested and found to contain: F - 0.9 mg / L; SiF6 2-Not detected; SO4 2- : 98 mg / L; Ammonium nitrogen ≤ 7 mg / L; Cu 2+ ≤0.1mg / L; Ni 2+ ≤0.1mg / L;

[0095] Example 2

[0096] The method for treating inorganic fluoride waste liquid in this embodiment includes the following steps:

[0097] S1: Pump 10L of pre-filtered waste liquid into a circulating reactor containing 200g of calcium sulfate dihydrate seed crystals. While maintaining the pH of the system at approximately 3.0, slowly add an aqueous solution containing 18.5g of calcium chloride. Mix at 200rpm for 40min, filter, and obtain treated liquid A and precipitate A.

[0098] S2: Take treatment solution A, adjust the pH to 8.5 with 1 mol / L sodium hydroxide solution, mix at 300 rpm for 35 min, first add an aqueous solution containing 500 mg of magnesium chloride hexahydrate, continue stirring for 12 min, then add an aqueous solution containing 6.1 g of calcium chloride, mix at 200 rpm for 25 min, finally add 10 mg of anionic polyacrylamide, mix at 50 rpm for 15 min, filter, and obtain treatment solution B and precipitate B;

[0099] S3: Take treatment solution B, finely adjust the pH to 8.5, then add an aqueous solution containing 1.54g of sodium sulfide, mix at 200rpm for 35min, filter, and obtain treatment solution C and precipitate C.

[0100] S4: Take the treatment solution C, first add 1g of sodium carbonate, stir and mix for 10min, filter, then add an aqueous solution containing 52.0g of disodium hydrogen phosphate dodecahydrate, mix at 200rpm for 3min, then add an aqueous solution containing 28g of magnesium chloride hexahydrate, and dynamically adjust the pH to 9.0 using 0.5mol / L sodium hydroxide solution, mix at 200rpm for 40min, filter, and obtain treatment solution D and precipitate D;

[0101] S5: Take the treatment solution D, adjust the pH to 7.0 with 0.5mol / L dilute hydrochloric acid, add 2.8g of polyaluminum chloride, mix at 150rpm for 30min, filter, and obtain the aqueous solution and precipitate E.

[0102] The water solution was tested and found to contain: F - 0.7 mg / L; SiF6 2- Not detected; SO4 2- : 92 mg / L; Ammonium nitrogen ≤ 5 mg / L; Cu 2+ ≤0.1mg / L; Ni2+ ≤0.1mg / L;

[0103] Example 3

[0104] The method for treating inorganic fluoride waste liquid in this embodiment includes the following steps:

[0105] S1: Pump 10L of pre-filtered waste liquid into a circulating reactor containing 200g of calcium sulfate dihydrate seed crystals. While maintaining the pH of the system at approximately 2.5, slowly add an aqueous solution containing 18.2g of calcium chloride. Mix at 200rpm for 40min, filter, and obtain treated liquid A and precipitate A.

[0106] S2: Take treatment solution A, adjust the pH to 9.0 with 1 mol / L sodium hydroxide solution, mix at 300 rpm for 35 min, first add an aqueous solution containing 470 mg of magnesium chloride hexahydrate, continue stirring for 12 min, then add an aqueous solution containing 6.0 g of calcium chloride, mix at 200 rpm for 25 min, finally add 10 mg of anionic polyacrylamide, mix at 50 rpm for 15 min, filter, and obtain treatment solution B and precipitate B;

[0107] S3: Take treatment solution B, finely adjust the pH to 9.0, then add an aqueous solution containing 1.50g of sodium sulfide, mix at 200rpm for 35min, filter, and obtain treatment solution C and precipitate C.

[0108] S4: Take the treatment solution C, first add 2g of sodium carbonate, stir and mix for 10min, filter, then add an aqueous solution containing 51.0g of disodium hydrogen phosphate dodecahydrate, mix at 200rpm for 3min, then add an aqueous solution containing 27.5g of magnesium chloride hexahydrate, and dynamically adjust the pH to 9.5 using 0.5mol / L sodium hydroxide solution, mix at 200rpm for 40min, filter, and obtain treatment solution D and precipitate D;

[0109] S5: Take the treatment solution D, adjust the pH to 7.5 with 0.5mol / L dilute hydrochloric acid, add 3.5g of polyaluminum chloride, mix at 150rpm for 30min, filter, and obtain the aqueous solution and precipitate E.

[0110] The water solution was tested and found to contain: F - 0.8 mg / L; SiF6 2- Not detected; SO4 2- : 94 mg / L; Ammonium nitrogen ≤ 5 mg / L; Cu 2+ ≤0.1mg / L; Ni 2+ ≤0.1mg / L;

[0111] Example 4

[0112] The difference between this embodiment and embodiment 3 is as follows:

[0113] S5: Take the treatment solution D, adjust the pH to 7.5 with 0.5mol / L dilute hydrochloric acid, add 3.5g of hydroxyapatite, mix at 150rpm for 30min, filter, and obtain the aqueous solution and precipitate E.

[0114] Everything else is the same as in Example 3.

[0115] The water solution was tested and found to contain: F - 0.7 mg / L; SiF6 2- Not detected; SO4 2- : 95 mg / L; Ammonium nitrogen ≤ 5 mg / L; Cu 2+ ≤0.06mg / L; Ni 2+ ≤0.08mg / L;

[0116] Example 5

[0117] The difference between this embodiment and embodiment 4 is that:

[0118] S5: Take the treatment solution D, adjust the pH to 7.5 with 0.5mol / L dilute hydrochloric acid, add 3.5g of polyacrylamide gel-supported hydroxyapatite, mix at 150rpm for 30min, filter, and obtain the aqueous solution and precipitate E.

[0119] The polyacrylamide gel-supported hydroxyapatite was derived from Preparation Example 1.

[0120] The rest is the same as in Example 4.

[0121] The water solution was tested and found to contain: F - 0.5 mg / L; SiF6 2- Not detected; SO4 2- : 94 mg / L; Ammonium nitrogen ≤ 5 mg / L; Cu 2+ ≤0.05mg / L; Ni 2+ ≤0.05mg / L;

[0122] Example 6

[0123] The difference between this embodiment and embodiment 5 is as follows:

[0124] S5: Take the treatment solution D, adjust the pH to 7.5 with 0.5mol / L dilute hydrochloric acid, add 3.5g of hydroxyapatite loaded on the magnetic carrier, mix at 150rpm for 30min, filter, and obtain the aqueous solution and precipitate E.

[0125] The magnetic carrier loaded with hydroxyapatite was from preparation example 3.

[0126] The rest is the same as in Example 5.

[0127] The water solution was tested and found to contain: F - 0.4 mg / L; SiF6 2- Not detected; SO4 2- : 93 mg / L; Ammonium nitrogen ≤ 5 mg / L; Cu 2+ ≤0.05mg / L; Ni 2+ ≤0.05mg / L;

[0128] Example 7

[0129] The difference between this embodiment and embodiment 6 is that:

[0130] S1: Pump 10L of pre-filtered waste liquid into a circulating reactor containing 200g of calcium sulfate dihydrate seed crystals. While maintaining the pH of the system at approximately 2.5, slowly add 5g of polyaspartic acid and an aqueous solution containing 18.2g of calcium chloride. Mix at 200rpm for 40min, filter, and obtain treatment liquid A and precipitate A.

[0131] S5: Take the treatment solution D, adjust the pH to 7.5 with 0.5mol / L dilute hydrochloric acid, add 3.5g of hydroxyapatite loaded on the magnetic carrier, mix at 150rpm for 30min, filter, and obtain the aqueous solution and precipitate E.

[0132] The magnetic carrier loaded with hydroxyapatite was from preparation example 4.

[0133] The rest is the same as in Example 6.

[0134] The solution tested positive for: F - 0.2 mg / L; SiF6 2- Not detected; SO4 2- : 69 mg / L; Ammonium nitrogen ≤ 5 mg / L; Cu 2+ ≤0.05mg / L; Ni 2+ ≤0.05mg / L;

[0135] Example 8

[0136] The difference between this embodiment and embodiment 7 is that:

[0137] S1: Pump 10L of pre-filtered waste liquid into a circulating reactor containing 200g of calcium sulfate dihydrate seed crystals. While maintaining the pH of the system at approximately 2.5, slowly add 2g of hydroxyethylidene diphosphonic acid, 1g of sodium dodecylbenzenesulfonate, and an aqueous solution containing 18.2g of calcium chloride. Mix at 200rpm for 40min, filter, and obtain treated liquid A and precipitate A.

[0138] S5: Take the treatment solution D, adjust the pH to 7.5 with 0.5mol / L dilute hydrochloric acid, add 3.5g of polyacrylamide gel-supported hydroxyapatite, mix at 150rpm for 30min, filter, and obtain the aqueous solution and precipitate E.

[0139] The polyacrylamide gel-supported hydroxyapatite was derived from Preparation Example 1.

[0140] The rest is the same as in Example 7.

[0141] The water solution was tested and found to contain: F - 0.3 mg / L; SiF6 2- Not detected; SO4 2- : 65 mg / L; Ammonium nitrogen ≤ 5 mg / L; Cu 2+ ≤0.05mg / L; Ni 2+ ≤0.05mg / L;

[0142] Example 9

[0143] The difference between this embodiment and embodiment 7 is that:

[0144] S1: Pump 10L of pre-filtered waste liquid into a circulating reactor containing 200g of calcium sulfate dihydrate seed crystals. While maintaining the pH of the system at approximately 2.5, slowly add 5g of polyaspartic acid, 2g of sodium dodecylbenzenesulfonate, and an aqueous solution containing 18.2g of calcium chloride. Mix at 200rpm for 40min, filter, and obtain treated liquid A and precipitate A.

[0145] S5: Take the treatment solution D, adjust the pH to 7.5 with 0.5mol / L dilute hydrochloric acid, add 3.5g of hydroxyapatite loaded on the magnetic carrier, mix at 150rpm for 30min, filter, and obtain the aqueous solution and precipitate E.

[0146] The magnetic carrier loaded with hydroxyapatite was from preparation example 4.

[0147] The rest is the same as in Example 7.

[0148] The water solution was tested and found to contain: F - 0.2 mg / L; SiF6 2- Not detected; SO4 2- : 47 mg / L; Ammonium nitrogen ≤ 5 mg / L; Cu 2+ ≤0.05mg / L; Ni 2+ ≤0.05mg / L;

[0149] The analysis is as follows:

[0150] Examples 1-3 demonstrate that by employing seed-induced crystallization to pre-remove sulfate, calcium-magnesium co-precipitation to remove fluorides, sulfide precipitation to remove heavy metals, and struvite precipitation to remove ammonium nitrogen, effective synergistic removal of multiple pollutants in complex wafer cleaning wastewater can be achieved, laying a solid foundation for subsequent deep treatment. Examples 4-9 show that ordinary hydroxyapatite has limited effect on improving the treatment effect, while hydroxyapatite supported by polyacrylamide gel and hydroxyapatite supported by magnetic carrier exhibit superior deep purification performance due to the significant increase in specific surface area and effective improvement in mass transfer efficiency, achieving deep removal of fluorides. In particular, the introduction of polyaspartic acid or hydroxyethylidene diphosphonic acid in step S1 to optimize the crystallization process, when combined with the above-mentioned supported adsorbents, produces a significant synergistic enhancement effect, not only further reducing the fluoride ion concentration but also unexpectedly achieving deep removal of sulfate. Furthermore, the introduction of sodium dodecylbenzenesulfonate can further optimize the system reaction environment and solid-liquid separation effect.

[0151] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for treating inorganic fluoride waste liquid, characterized in that, Includes the following steps: S1: The pre-filtered waste liquid is pumped into the seed crystal circulation reactor, calcium salt is added, and the mixture is mixed for 30-40 minutes. After solid-liquid separation, the treated liquid A and precipitate A are obtained. Calcium sulfate dihydrate seed crystals are placed in the seed crystal circulation reactor. S2: Take the treatment liquid A, adjust the pH to 8.5~9.0, mix for 30~40 min, add magnesium salt first, then calcium salt, then flocculant, mix for 15~25 min, after solid-liquid separation, obtain treatment liquid B and precipitate B; S3: Take the treatment solution B, adjust the pH to 8.5~9.0, add the sulfide, mix for 30~40 minutes, and after solid-liquid separation, obtain the treatment solution C and precipitate C; S4: Take the treatment solution C, adjust the pH to 8.5~9.5, add phosphate and magnesium salt, mix for 30~40 min, and after solid-liquid separation, obtain treatment solution D and precipitate D; S5: Take the treatment solution D, adjust the pH to 7.0~7.5, add the adsorbent and mix for 30~40 minutes. After solid-liquid separation, the aqueous solution and precipitate E are obtained. In step S1, the calcium ions in the calcium salt react with the SO4 in the waste liquid. 2- The molar concentration ratio is (1.05~1.1):1; In step S2, the ratio of the total molar number of magnesium ions and calcium ions in the magnesium salt and calcium salt to the total molar number of fluoride ions after hydrolysis of fluoride ions and fluorosilicate ions in the waste liquid is (0.45~0.47):

1. The calcium salt is calcium chloride dihydrate; the magnesium salt is magnesium chloride hexahydrate; The flocculant is anionic polyacrylamide; The adsorbent is selected from either polyaluminum chloride or hydroxyapatite.

2. The method for treating inorganic fluoride waste liquid according to claim 1, characterized in that, In step S4, before adding phosphate, a step of adding carbonate is also included.

3. The method for treating inorganic fluoride waste liquid according to claim 1, characterized in that, The hydroxyapatite is a supported hydroxyapatite, and the supported hydroxyapatite is selected from either polyacrylamide gel-supported hydroxyapatite or magnetic carrier-supported hydroxyapatite.

4. The method for treating inorganic fluoride waste liquid according to claim 3, characterized in that, The method for preparing polyacrylamide gel-supported hydroxyapatite includes the following steps: Under an inert atmosphere, acrylamide monomer and a hydroxyapatite suspension with a solid content of 5% to 7% were taken at a mass ratio of (10~15):(85~90), a crosslinking agent was added, the temperature was raised to 50~60℃, an initiator and a polymerization accelerator were added, the reaction was carried out for 50~60 min, aged, washed, granulated and dried to obtain polyacrylamide gel-supported hydroxyapatite.

5. The method for treating inorganic fluoride waste liquid according to claim 3, characterized in that, The method for preparing hydroxyapatite supported on the magnetic carrier includes the following steps: S11: Under an inert atmosphere, magnetic Fe3O4 is dispersed in an aqueous ethanol solution, the pH is adjusted to 9.5~10.0, tetraethyl orthosilicate is added, the temperature is raised to 50~60℃, the reaction is carried out for 2~3 hours, the solid and liquid are separated, washed, and dried to obtain Fe3O4@SiO2. S12: Under an inert atmosphere, Fe3O4@SiO2 is dispersed in water, the pH is adjusted to 10~10.5, the temperature is raised to 75~85℃, calcium salt and phosphate are added, the reaction is carried out for 3~4 hours, solid-liquid separation is performed, washing and drying are carried out to obtain magnetically supported hydroxyapatite.

6. The method for treating inorganic fluoride waste liquid according to claim 5, characterized in that, The mass ratio of the magnetic Fe3O4 to tetraethyl orthosilicate is 1:(0.1~0.2).

7. The method for treating inorganic fluoride waste liquid according to claim 5, characterized in that, The mass ratio of Fe3O4@SiO2, calcium salt, and phosphate is 1:(0.6~0.9):(0.9~1.3).

8. The method for treating inorganic fluoride waste liquid according to claim 1, characterized in that, Step S1 includes, at or before the addition of calcium salt, the addition of polyaspartic acid or hydroxyethylidene diphosphonic acid to the seed crystal circulation reactor.

9. The method for treating inorganic fluoride waste liquid according to claim 1, characterized in that, In step S1, before or during the addition of the calcium salt, sodium dodecylbenzenesulfonate is added to the seed crystal circulation reactor.