A special inhibitor for treating uranium-fluorine-containing wastewater and its preparation method

Abstract

The present invention belongs to the field of water treatment, and in particular to a special inhibitor for treating uranium-fluorine wastewater and a preparation method thereof. The special inhibitor for treating uranium-fluorine wastewater, by weight, comprises: 1-9 parts of titanium dioxide, 90-120 parts of calcium hydroxyphosphate, 10.1-196.2 parts of ferrous chloride and 121-4925 parts of calcium chloride. The present invention is directed to the existing technical problems in the treatment process of uranium-fluorine wastewater, and provides a special inhibitor that can effectively inhibit the interference of uranium with fluorine wastewater treatment, so that the fluorine ions produced by the reduction reaction of uranium-fluorine complex ions and some fluorine ions in the wastewater are exchanged with a large number of hydroxyls in the inhibitor, and the fluorine in the wastewater is subjected to a new chemical treatment pathway, which is beneficial to the capture, flocculation, precipitation and separation of the subsequent treatment of uranium-fluorine wastewater. Its treatment effect is stable, the operation is simple and easy, and the industrial feasibility is strong.

Description

Technical Field

[0001] The invention belongs to the field of water treatment, and in particular relates to a special inhibitor for treating uranium-fluorine-containing wastewater and a preparation method thereof. Background Art

[0002] Excessive discharge of fluorine-containing industrial wastewater can lead to an increase in the fluoride content in regional water bodies and soil, directly affecting the safety of drinking water, grain, and crops such as vegetables and fruits, and in turn affecting the health of people living in the area for a long time and the quality of domestic meat, so it must be controlled.

[0003] Fluoride-containing wastewater treatment often uses lime neutralization to generate calcium fluoride CaF2 and then precipitate and separate it. This process technology was widely used by non-ferrous metal industry and nuclear industry design institutes from the 1970s to the 1990s. Its process flow is simple and the treatment cost is low. However, the generated calcium fluoride particles will be wrapped on the surface of Ca(OH)2 particles in the lime emulsion, causing the reaction to be interrupted. Its treatment effect is generally between 35-100 mg / L, and the discharged wastewater also complies with the non-ferrous industry standards at the time.

[0004] With the implementation of the Integrated Sewage Discharge Standard (GB8978-1996), except for low-fluoride areas, all other areas implement the 10 mg / L discharge standard. In order to respond quickly to the new standard requirements, some enterprises directly use activated alumina or calcium hydroxyphosphate for adsorption treatment after lime treatment. However, due to the high fluoride content in industrial wastewater and the limited capacity of the adsorbent, the analysis is too frequent, causing the adsorbent to be "poisoned" and the adsorption facilities cannot operate stably for a long time. Others, after a period of technological development, have added aluminum-based coagulant coagulation reaction and flocculant such as polyphenylene amide flocculation precipitation process after the reaction and precipitation of fluoride-containing wastewater by lime method, and the treated fluoride-containing wastewater can achieve standard discharge.

[0005] From then until the implementation of the new industry standard "Inorganic Chemical Industry Pollutant Emission Standard" GB31573-2015, when the fluoride emission standard of 6 mg / L is implemented, the standard can be achieved by adding soluble calcium through a one-stage neutralization by the lime method, and then using an aluminum-based coagulant such as aluminum sulfate, aluminum chloride or its polymers for coagulation reaction after a primary precipitation, and then using a flocculant such as polyphenylene amide for flocculation and precipitation treatment.

[0006] In view of the existing fluoride-containing wastewater treatment problem, a lot of research work has been done:

[0007] Prior art CN115784408B discloses a method for removing phosphorus, fluorine and heavy metals from wastewater by inducing crystallization using modified crystal seeds, which relates to the field of water treatment. The invention aims to solve the problem that phosphorus-containing wastewater, heavy metal-containing wastewater and fluorine-containing wastewater are difficult to remove. The invention adopts calcium ion or strong base modified crystal seeds, or iron hydroxide colloid or aluminum hydroxide colloid modified crystal seeds, or thiol functional modified crystal seeds, or sulfide ion modified crystal seeds, and uses calcium salt and strong base as crystallization agents to remove phosphorus, fluorine and heavy metals from wastewater. While ensuring excellent removal effect, the concentration of pollutants such as phosphorus, fluorine and heavy metals in the effluent is greatly reduced, avoiding the subsequent deep treatment process of pollutants. However, for the process of using lime to provide calcium ions to treat high-concentration industrial fluoride-containing wastewater, the strongly alkaline-modified crystals will undoubtedly inhibit the hydrolysis of calcium hydroxide in the lime to a large extent, which is not conducive to promoting the main defluorination reaction to the direction of calcium fluoride precipitation. On the other hand, if this technology is used to treat wastewater containing uranium and fluorine, the strongly alkaline-modified crystals will cause various morphological changes of the uranium complex, which will bring more impacts to the treatment process. At the same time, the introduction of sulfur ions can form insoluble metal sulfide precipitates for most heavy metal ions, but it is different for some metal complex ions, and it is difficult to form new precipitates. Moreover, sulfur ions can generate slightly soluble calcium sulfide with calcium ions, and the consumption of effective calcium ions also inhibits the hydrolysis of calcium hydroxide in the lime, which is not conducive to the defluorination reaction.

[0008] Prior art CN112850965B discloses a process and device for recycling high-concentration fluorine-containing wastewater generated by the production of silicon solar cells. The device of this process uses a cyclone mixing device, a self-cleaning filter and a self-cleaning sand filter, etc.; at the same time, in the treatment process of this process, a variety of reagents are screened and compounded to obtain granular reagents. Under the action of centrifugation, the granular reagents are fully contacted with the fluoride ions in the fluoride-containing wastewater to react to generate fluoride. The fluoride after the reaction is taken away by water, and the unreacted granular reagents are left to continue to react with the fluoride-containing wastewater. The present invention can recycle reverse osmosis concentrated water, reduce the amount of reagents added and the amount of slag discharged, the treated water has low hardness, and can be directly reused for the production of silicon solar cells. However, this technology does not consider the influence of uranium-fluorine complex ions on fluoride treatment.

[0009] Prior art CN118416870A discloses a method for preparing a fluoride ion adsorbent: (1) ferric oxide, ferric disulfide and calcium chloride are uniformly mixed to obtain a mixture; wherein the mass ratio of ferric oxide, ferric disulfide and calcium chloride is (10-12): (1-2): (0.08-0.1); (2) the mixture is subjected to a first-stage roasting in an atmosphere containing tin tetrafluoride gas to obtain a first-stage roasting slag; (3) the first-stage roasting slag is subjected to a second-stage roasting in a water vapor atmosphere to obtain a second-stage roasting slag; (4) the second-stage roasting slag is water-soaked, filtered after the water-soaking is completed, and the fluoride ion adsorbent is obtained. The invention selects ferric oxide, ferric disulfide and calcium chloride as raw materials, and combines the process control of the two-stage roasting. Finally, the adsorbent obtained by water-soaking has the characteristics of stable structure, large fluorine adsorption capacity, fast fluorine adsorption rate, etc., and the adsorbent can be separated from the solution without liquid-solid separation. However, when the wastewater contains uranium fluoride complex ions and the fluorine content is above 3000 mg / L, the influence of the uranium fluoride complex ions is not resolved. The uranium fluoride complex ions will still be free in the wastewater in the form of ions, and the standard requirements of U≤50μg / L and F≤6mg / L cannot be met, let alone continuous treatment operation on an industrial scale.

[0010] Due to the variable chemical forms of uranium, it undergoes flexible and diverse changes under different pH values, different redox potentials, and even in different environments where anions and cations coexist. In particular, under the influence of fluorine, which has a very high electronegativity, a variety of uranium-fluorine complexes are formed, causing abnormalities in the existing fluorine removal technology during the treatment process. The various uranium-fluorine complex ions formed by uranium prevent the fluorine itself from combining with calcium ions in an ionic state, resulting in the fluorine in the complex ions being unable to form calcium fluoride and enter the slag phase for precipitation and separation, interfering with the fluorine treatment in the wastewater to meet the standards. Summary of the invention

[0011] The object of the present invention is to provide a special inhibitor for treating uranium-containing fluorine wastewater, which can effectively inhibit the interference of uranium on the treatment of fluorine wastewater, and a preparation method thereof.

[0012] In order to achieve the above object, the technical solution of the present invention is as follows:

[0013] A special inhibitor for treating uranium-fluorine-containing wastewater, wherein the raw materials thereof include, by weight: 1-9 parts of titanium dioxide, 90-120 parts of hydroxy calcium phosphate, 10.1-196.2 parts of ferrous chloride and 121-4925 parts of calcium chloride.

[0014] If ferrous chloride is replaced by ferrous sulfate, the resulting calcium sulfate will solidify the porous structure of calcium hydroxyphosphate, making it unable to play an inhibitory role.

[0015] In a preferred embodiment, the crystal form of the titanium dioxide is anatase.

[0016] This crystal form has high reactivity and can be used in catalysis and photoelectric conversion. In the present invention, this crystal form can increase the ability to form an active apatite layer, increase the anion position on the hydroxyl position, and provide more opportunities for fluorine to enter the crystal lattice. Other common crystal forms such as rutile are too stable, and brookite is unstable and will be converted into rutile at high temperature, so they are not suitable for use in the present invention.

[0017] In a preferred embodiment, the particle size D90 of the titanium dioxide is not greater than 100 nm.

[0018] The use of nano-sized titanium dioxide is conducive to the entry of titanium dioxide into the structural channels of calcium hydroxyphosphate, thereby achieving the purpose of increasing the atomic layer capacity of calcium hydroxyphosphate; if it is too large, it will block the channel.

[0019] In a preferred embodiment, the particle size of the calcium hydroxyphosphate is no greater than 1 μm, preferably 0.5-1 μm.

[0020] If the particle size of hydroxy calcium phosphate is too large, the porosity will be significantly reduced; if the particle size is too small, even reaching the nanometer level, it will be difficult to flocculate and settle as the main carrier in the subsequent wastewater treatment process, which will directly affect the treatment effect and increase the treatment cost.

[0021] In a preferred embodiment, the inhibitor for treating uranium-fluorine-containing wastewater comprises, by weight, 3-5 parts of titanium dioxide, 100 parts of calcium hydroxyphosphate, 10.3-189 parts of ferrous chloride and 375.5-1129.5 parts of calcium chloride.

[0022] Based on the same inventive concept, the present invention also claims a method for preparing the inhibitor for treating uranium-fluorine-containing wastewater, comprising the following steps:

[0023] Titanium dioxide and calcium hydroxyphosphate are uniformly mixed and then calcined and modified to obtain modified calcium hydroxyphosphate; the modified calcium hydroxyphosphate is dispersed in ferrous chloride for coating and modification to obtain a mixture; and the mixture is dispersed in calcium chloride for aging and stabilization to obtain the inhibitor for treating uranium-fluoride-containing wastewater.

[0024] In a preferred embodiment, the calcination modification temperature is 500-850°C, preferably 650-700°C; the calcination time is 1-4 hours, preferably 1.5-2 hours.

[0025] In a preferred embodiment, in order to avoid particle agglomeration, ultrasonic wave disintegration is used after calcination.

[0026] In a preferred embodiment, the weight ratio of ferrous chloride to modified calcium hydroxyphosphate is (0.1-1.8):1.

[0027] The modified hydroxy calcium phosphate coated with ferrous chloride adopts the principle of excess ferrous chloride curing.

[0028] In a preferred embodiment, the coating modification step includes: first dissolving ferrous chloride in water to prepare a ferrous chloride solution with a mass concentration of 5-33%, and then dispersing the modified calcium hydroxyphosphate in the ferrous chloride solution for coating modification under closed conditions for 2-48 hours.

[0029] In a preferred embodiment, the coating modification time is preferably 8-24 hours.

[0030] In a preferred embodiment, the mass concentration of the ferrous chloride solution is preferably 18-33%.

[0031] In a preferred embodiment, the preparation device of ferrous chloride coated modified hydroxy calcium phosphate is a low-pressure reactor with a dispersing stirrer and a pressure safety valve.

[0032] In a preferred embodiment, the aging and stabilization step includes: first dissolving calcium chloride in water to obtain a calcium chloride solution, and then uniformly dispersing the mixture in the calcium chloride solution, the feeding time is 0.8-1.2h, and after the feeding is completed, aging and stabilizing for 2-24h under closed conditions to obtain the inhibitor for treating uranium-fluoride wastewater.

[0033] In a preferred embodiment, the dispersion speed during feeding is 65-120 r / min; the dispersion speed after feeding is 9-17 r / min.

[0034] The dispersion speed is fast when adding materials in order to reduce the contact time with air and reduce the oxidation of ferrous iron; after adding materials, they are slowly stirred in a closed container so as not to disrupt the modified and coated particles that have been formed and prevent them from agglomerating, which is beneficial to aging stability.

[0035] In a preferred embodiment, the aging stabilization time is preferably 4-24 hours.

[0036] In a preferred embodiment, the mass concentration of the calcium chloride solution is 15%-42%, preferably 15-25%.

[0037] In a preferred embodiment, the weight of the mixture is 6-37.5%, preferably 6.4-15%, of the calcium chloride solution.

[0038] In a preferred embodiment, the aging-stable preparation device is a pressure reactor with a stirring device and a pressure safety valve.

[0039] The method for using the inhibitor for treating uranium-fluorine wastewater is as follows: adding the inhibitor for treating uranium-fluorine wastewater with a volume concentration of 4%-21% to the uranium-fluorine wastewater, stirring and reacting for 30-90 minutes, adding lime and reacting for a period of time, and then precipitating and flocculating to obtain treated wastewater.

[0040] The present invention is further explained below:

[0041] 1.1 The reaction of the inhibitor to the fluorine uranium complex ion induced reduction process is as follows:

[0042] Fe 2+ =Fe 3+ +e;

[0043] UO2F + +4H + +2e=U 4+ +2H2O+F - ;

[0044] 2UO2 + +2e=UO2 2+ +U 4+ ;

[0045] UO2 2+ +4H + +2e=U 4+ +2H2O;

[0046] 1.2 The reactions that occur during the uranium inhibition process (and the accompanying new fluorine treatment pathway) are as follows:

[0047] Ca 10 (PO4)6(OH)2 +U 4+ +2F - =Ca m U n (PO4)6F2↓+nCa 2+ (m+n=10);

[0048] 1.3 The reactions that occur during fluorine removal (the main route of fluorine treatment) are as follows: Ca 2+ +2F - =CaF2↓(s);

[0049] 1.4 Principle description: Fe in modified calcium hydroxyphosphate in the inhibitor 2+ Induce the reduction reaction of hexavalent uranium to convert the fluorine uranium complex ion UO2F + The uranium in the + From hexavalent uranium to tetravalent uranium ions U 4+ , while Fe 2 +Oxidized to Fe 3+ Adsorption on the reaction products promotes the coagulation and enlargement of the crystals, which is conducive to precipitation; the induced U 4+ Ca 2+ The ionic radius of the two is very similar, and they are unidirectionally polar isomorphic. They replace each other mainly in the form of ion exchange and enter the modified hydroxyl calcium phosphate lattice in the inhibitor. At the same time, the modification of titanium dioxide provides more hydroxyl sites for the inhibitor which itself has more hydroxyl sites, so that the fluoride ions produced from the reduction reaction of uranium fluoride complex ions and some fluoride ions in the wastewater are exchanged with a large number of hydroxyl groups in the inhibitor. When uranium enters the inhibitor lattice, fluorine also has more opportunities to enter the anion sites of the inhibitor lattice. At the same time, the reaction of uranyl reduction obtains better driving force, and fluorine treatment obtains a new chemical treatment route. The generated uranium calcium fluorophosphate or uranium fluoroapatite is a Freund's salt structure with a very low volume, which is conducive to the capture, flocculation, precipitation and separation of subsequent treatment of uranium-fluoride wastewater.

[0050] The calcium chloride mother liquor in the inhibitor releases a large amount of soluble Ca 2+ , which is the high concentration of F in wastewater - The formation of CaF2 precipitation with Ca(OH)2 provides a reliable concentration driving force for the chemical reaction.

[0051] The beneficial effects of the present invention are:

[0052] The present invention aims at the existing technical problems in the treatment of uranium-fluoride wastewater. The research finds that the interference of uranium on fluoride treatment is the main reason for the defects of the existing fluoride treatment technology. The research further finds and verifies that the chemical mechanism of uranium interference with fluoride treatment is that the uranyl fluoride complex ions cannot freely release free fluoride ions F. - , interfering with its interaction with calcium ions Ca 2+ CaF2 precipitation is generated. The present invention provides a special inhibitor that can effectively inhibit the interference of uranium on fluorine wastewater treatment and its preparation method, with stable treatment effect, simple and easy operation, and strong industrial feasibility. And the inhibitor has achieved stable operation treatment effect in large-scale engineering practice. DETAILED DESCRIPTION

[0053] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention belong to the scope of protection of the present invention.

[0054] In the present invention, if the materials agglomerate after calcination, they are crushed and dispersed by an ultrasonic crusher.

[0055] The wastewater samples used in the test and industrial application of the present invention come from tailings water and production wastewater of two companies, respectively.

[0056] In the experiment and industrial application of the present invention, fluorine and uranium are detected and analyzed by using a fluorine ion selective electrode and an ICP-MS inductively coupled plasma mass spectrometer respectively.

[0057] The particle size of the raw materials used in the preparation of the present invention is detected by a laser particle size analyzer.

[0058] Unless otherwise specified, the raw materials or chemical reagents used in the implementation of the present invention are obtained through conventional commercial channels.

[0059] Example 1

[0060] 3g of anatase titanium dioxide with a particle size of D90 = 50nm and 100g of hydroxy calcium phosphate with a particle size of D50 = 0.5μm were stirred and mixed, and then calcined at a constant temperature of 650℃ in a tube furnace for 1.5 hours. After cooling, they were broken and dispersed again by ultrasound into 309g of a 20% aqueous solution containing 61.8g of ferrous chloride. After dispersion and stirring for 10 minutes, they were placed in a volumetric flask and sealed for 8 hours. They were evenly introduced into 4000g of a 16% calcium chloride aqueous solution. The feeding time was 15 minutes. Stirring was started while adding the materials. The dispersion speed was 120r / min. The dispersion speed after adding the materials was 15r / min. After stirring for 30 minutes after adding the materials, they were placed in a plastic bottle, sealed with a cover, and aged for 4 hours before the effect verification test was carried out.

[0061] Take 20ml of inhibitor and add it into 300ml of uranium-fluoride wastewater containing 25mg / L uranium and 2.5g / L fluorine from a certain tailings, stir and react for 60 minutes, add lime to assist reaction, precipitation and secondary flocculation precipitation, then take the clear liquid to a research institute of China National Nuclear Corporation for analysis. The results showed that the treated clear liquid contained uranium: 0.00500mg / L, fluorine: 2.28mg / L.

[0062] Example 2

[0063] 60g of anatase titanium dioxide with a particle size of D90 = 85nm and 1500g of hydroxy calcium phosphate with a particle size of D50 = 1μm were stirred and mixed, and then calcined at a constant temperature of 690℃ in a tube furnace for 2 hours. After cooling, they were broken and dispersed again by ultrasonic waves into 9480g of a 25% aqueous solution containing 2370g of ferrous chloride. After being dispersed, stirred and mixed for 25min, they were sealed and coated in a plastic barrel for 12 hours; they were evenly introduced into 73600g of a 20% calcium chloride aqueous solution, and the feeding time was 35min. Stirring was started while feeding, and the dispersion speed was 100r / min. The dispersion speed after feeding was 17r / min. After stirring for 30min after feeding, they were placed in a plastic pot, sealed and aged for 10 hours, and then the effect verification test was carried out.

[0064] Take 250ml of inhibitor and add it into 3000ml of uranium-fluoride wastewater containing 1100mg / L uranium and 4500mg / L fluorine of a certain company, stir and react for 60 minutes, add lime to assist the reaction, and then carry out precipitation and flocculation absorption. Then take the clear liquid to a research institute of China National Nuclear Corporation for analysis: uranium 0.01140mg / L, fluorine 4.62mg / L. After effective inhibition, uranium meets the requirement of no more than 50 micrograms / L stipulated by the nuclear industry, and fluorine meets the limit of no more than 6mg / L stipulated in the "Inorganic Chemical Industry Pollutant Emission Standard" GB31573-2015.

[0065] Comparative Example 1

[0066] The two identical wastewater samples (i.e., 3000 ml of uranium-containing and fluorine-containing wastewater from a certain company containing 1100 mg / L uranium and 4500 mg / L fluorine) were used. One was directly added with the same amount of lime as in Example 2 for reaction and then precipitated and flocculated, which was Treatment 1. The other was added with iron powder (according to the same molar amount as in Example 2, with an excess of 10%, i.e., 4.37 g) under ultrasonic conditions to inhibit uranium and lime for fluorine and uranium treatment tests, which was Treatment 2. The treatment results of Treatment 1 were: the uranium content in the clear liquid was 7.102 mg / L and the fluorine content was 12.62 mg / L. The treatment results of Treatment 2 were: the uranium content in the clear liquid was 1.305 mg / L; the fluorine content was 40.86 mg / L, which did not achieve the standard effect.

[0067] Example 3

[0068] 40kg of anatase titanium dioxide with a particle size of D50 = 60nm and 800kg of hydroxy calcium phosphate with a particle size of D50 = 0.8μm were stirred and mixed, and then calcined at 700℃ in a tube furnace for 2 hours. After cooling, they were broken and dispersed again by ultrasound into 933.3kg of 18% aqueous solution containing 168kg of ferrous chloride. After being dispersed, stirred and mixed for 30min, they were sealed and coated in a plastic reaction tank for 24 hours; they were evenly introduced into 27,000kg of 25% calcium chloride aqueous solution, and the feeding time was 60min. Stirring was started at the same time as the feeding, and the dispersion speed was 100r / min. The dispersion speed after the feeding was 17r / min. After stirring for 30min after the feeding, they were loaded into a plastic reactor, sealed and aged for 24 hours, and then sent to a certain (uranium industry) company for wastewater treatment for production verification.

[0069] Volumetric metering pump per 1m 3 / h inhibitor treatment 15m 3 / h parameter setting computer system automatically adds drugs, adopts the trough discharge method of nuclear industry standard, when the batch wastewater volume is 50 cubic meters, the uranium and fluorine contents are: 10mg / L and 1200mg / L respectively, due to the influence of startup and shutdown, the actual dosage is 3.5 cubic meters, and the uranium and fluorine contents of the external wastewater entering the standard detection pool after treatment are: 0.00606mg / L and 0.19mg / L respectively. Fluorine reaches the limit value of no more than 6mg / L specified in the "Inorganic Chemical Industry Pollutant Emission Standard" GB31573-2015, and uranium is also suppressed to meet the nuclear industry requirements of no more than 50 micrograms / liter.

[0070] Example 4

[0071] 16kg of anatase titanium dioxide with a particle size of D50 = 40nm and 500kg of hydroxy calcium phosphate with a particle size of D50 = 0.6μm were stirred and mixed, and then calcined at a constant temperature of 680℃ in a tube furnace for 1.8 hours. After cooling, they were broken and dispersed again by ultrasound into 172kg of a 30% aqueous solution containing 51.6kg of ferrous chloride. After being dispersed, stirred and mixed for 30 minutes, they were sealed and coated in a plastic reaction tank for 10 hours; then they were evenly introduced into 8600kg of a 15% calcium chloride aqueous solution, the feeding time was 45 minutes, and stirring was started while adding the materials. The dispersion speed was 65r / min, and the dispersion speed after adding the materials was 9r / min. After stirring for 30 minutes after adding the materials, they were loaded into a plastic reactor, sealed and aged for 20 hours, and then sent to a company for wastewater treatment for production verification.

[0072] Volumetric metering pump per 1m 3 / h inhibitor treatment 15m 3 / h parameter setting computer system automatically adds drugs, adopts the trough discharge method of nuclear industry standard, when the batch wastewater volume is 35 cubic meters, the uranium and fluorine contents are 8mg / L and 1000mg / L respectively, the actual dosage is 2.3 cubic meters, and the uranium and fluorine contents of the external wastewater entering the standard detection pool after treatment are 0.00365mg / L and 1.36mg / L respectively. It has reached the limit value of no more than 6mg / L stipulated in the "Inorganic Chemical Industry Pollutant Emission Standard" GB31573-2015, and uranium has also reached the requirement of no more than 50 micrograms / liter stipulated by the nuclear industry.

[0073] Comparative Example 2

[0074] 100g of hydroxy calcium phosphate with a particle size of D50 = 0.5μm without nano-titanium dioxide modification was calcined at 650℃ in a tube furnace for 1.5 hours and then cooled. Then, it was dispersed into 309g of a 20% aqueous solution containing 61.8g of ferrous chloride by ultrasonic crushing. After dispersion, stirring and mixing for 10 minutes, it was placed in a volumetric flask and sealed for coating and modification for 8 hours; it was evenly introduced into 4000g of a 16% calcium chloride aqueous solution, the feeding time was 15 minutes, and stirring was started while adding the materials. The dispersion speed was 120r / min, and the dispersion speed after adding the materials was 15r / min. After stirring for 30 minutes after adding the materials, it was placed in a plastic bottle, sealed with a cover, and aged for 4 hours before the effect verification test was carried out.

[0075] Take 20 ml of the agent and add it to 300 ml of uranium-containing and fluorine-containing wastewater of a tailings containing 25 mg / L uranium and 2.5 g / L fluorine as in Example 1, and stir to react for 60 minutes. After adding lime to assist the reaction, precipitation and secondary flocculation precipitation, the clear liquid is taken to a research institute of China National Nuclear Corporation for analysis. The uranium is 0.05900 mg / L and the fluorine is 9.28 mg / L. Both fluorine and uranium exceed the standard, and the excess increase of fluorine is large, indicating that the modifier titanium dioxide has the effect of further increasing the anion position, promoting the entry of fluorine into the inhibitor, and facilitating the decomposition of fluorine-uranium complex ions.

[0076] Comparative Example 3

[0077] 100g of hydroxy calcium phosphate with a particle size of D50 = 0.5μm without nano-titanium dioxide modification was calcined at 650℃ in a tube furnace for 1.5 hours and then cooled. 3g of anatase titanium dioxide with a particle size of D90 = 50nm was added and mixed. Then, ultrasonic waves were used to break and disperse it again into 309g of a 20% aqueous solution containing 61.8g of ferrous chloride. After dispersion, stirring and mixing for 10 minutes, it was placed in a volumetric flask and sealed for coating and modification for 8 hours; it was evenly introduced into 4000g of a 16% calcium chloride aqueous solution, the feeding time was 15 minutes, and stirring was started while adding the materials. The dispersion speed was 120r / min, and the dispersion speed after adding the materials was 15r / min. After stirring for 30 minutes after adding the materials, it was placed in a plastic bottle and sealed with a cover and aged for 4 hours before the effect verification test was carried out.

[0078] Take 20ml of the agent and add it to 300ml of uranium-containing and fluorine-containing wastewater of a tailings, which is the same as the wastewater containing 25mg / L uranium and 2.5g / L fluorine as in Example 1, and stir to react for 60min. After adding lime to assist the reaction, precipitation and secondary flocculation precipitation, the clear liquid is taken to a research institute of China National Nuclear Corporation for analysis. The results show that the treated clear liquid contains 0.07120mg / L uranium and 9.62mg / L fluorine.

[0079] Comparative Example 4

[0080] The operation steps are the same as those in Example 2, except that ferrous chloride is not used to modify the modified hydroxy calcium phosphate. 60g of anatase titanium dioxide with a particle size of D90 = 85nm and 1500g of hydroxy calcium phosphate with a particle size of D50 = 1μm are stirred and mixed, and then calcined at 690°C in a tube furnace for 2 hours. After cooling, they are crushed and dispersed again by ultrasound and uniformly introduced into 73600g of a calcium chloride aqueous solution with a mass concentration of 20%. The feeding time is 35min, and stirring is turned on while feeding. The dispersion speed is 100r / min, and the dispersion speed after feeding is 17r / min. After stirring for 30min after feeding, the mixture is placed in a plastic pot, sealed with a cover, and aged for 10 hours before an effect verification test is performed.

[0081] Take 250ml of the agent and add it into 3000ml of uranium and fluorine-containing wastewater of a certain company containing 1100mg / L uranium and 4500mg / L fluorine as in Example 2, and stir to react for 60min. Then add lime to assist the reaction and perform precipitation and flocculation and absorption. Then take the clear liquid to a research institute of China National Nuclear Corporation for analysis. The results are uranium: 13mg / L, fluorine: 7.39mg / L. The fluorine-uranium complex ion is not reduced by ferrous iron, and the fluorine therein cannot be removed by combining with calcium ions in ionic state.

[0082] Comparative Example 5

[0083] The operation steps are the same as those in Example 1, except that no calcium chloride aqueous solution is added. 3 g of anatase titanium dioxide with a particle size of D90 = 50 nm and 100 g of hydroxy calcium phosphate with a particle size of D50 = 0.5 μm are stirred and mixed, and then calcined at 650° C. in a tube furnace for 1.5 hours. After cooling, ultrasonic waves are used to break and disperse them again into 309 g of a 20% aqueous solution containing 61.8 g of ferrous chloride. After being dispersed, stirred and mixed for 10 minutes, they are placed in a volumetric flask for airtight coating and modification for 8 hours; they are placed in a plastic bottle, sealed and aged for 4 hours, and then an effect verification test is performed.

[0084] Take 20 ml of inhibitor and add it into 300 ml of uranium-fluoride wastewater containing 25 mg / L uranium and 2.5 g / L fluorine from a tailings, stir and react for 60 minutes, add lime to assist reaction, precipitation and secondary flocculation precipitation, then take the clear liquid to a research institute of China National Nuclear Corporation for analysis: uranium 0.09310 mg / L, fluorine 52.31 mg / L.

[0085] Comparative Example 6

[0086] The operation steps are the same as those in Example 1, except that the particle sizes of calcium hydroxyphosphate are D50=0.1 μm and 1.5 μm, respectively, and the other operations are the same as those in Example 1. Finally, an effect verification test is performed.

[0087] Two groups of 20ml inhibitors prepared by D50=0.1μm and 1.5μm hydroxy calcium phosphate were added to two groups of 300ml of uranium-fluoride wastewater containing 25mg / L uranium and 2.5g / L fluorine of a tailings, stirred and reacted for 60 minutes, and then lime was added to assist reaction, precipitation and secondary flocculation precipitation. The clear liquid was taken to a research institute of China National Nuclear Corporation for analysis. The uranium was 0.09155mg / L and 0.08732mg / L respectively; the fluorine was 12.50mg / L and 13.72mg / L respectively. It shows that under the same conditions, small molecules are difficult to flocculate into large molecules that can be completely precipitated when the particle size is too small, resulting in excessive standards; although the flocculation and sedimentation efficiency will be higher if the particle size is too large, the porosity of the coated modified hydroxy calcium phosphate is significantly reduced, the ability of fluorine-uranium complex ions to be reduced is reduced, and the opportunity for fluorine and uranium to exchange ions with the inhibitor is reduced, resulting in the failure of uranium-fluoride wastewater treatment to meet the standards.

[0088] Comparative Example 7

[0089] 309g of 20% aqueous solution of 61.8g of ferrous chloride was dispersed, stirred and mixed for 10min and then placed in a volumetric flask for 8h; then evenly introduced into 4000g of calcium chloride aqueous solution with a mass concentration of 16%, the feeding time was 15min, the stirring was turned on while the feeding, the dispersion speed was 120r / min, and the dispersion speed after the feeding was 15r / min. After stirring for 30min after the feeding, the mixture was put into a plastic bottle and sealed and aged for 4 hours before the effect verification test was carried out. The same batch of wastewater from a company in Example 1 was used for verification.

[0090] Take 20ml of inhibitor and add it to 300ml of uranium-fluoride wastewater containing 25mg / L uranium and 2.5g / L fluorine from a tailings, stir and react for 60 minutes, add lime to assist reaction, precipitation and secondary flocculation precipitation, and take the clear liquid to a research institute of China National Nuclear Corporation for analysis of uranium: 0.10550mg / L and 10.23mg / L. This shows that even though ferrous iron plays the role of reducing fluorine-uranium complex ions, due to the generated U 4+ It failed to enter the crystal lattice of modified calcium hydroxyphosphate in time and be fixed, resulting in the suspended lime particles in the treatment system and the generated uranium hydroxide and calcium fluoride encapsulating and blocking the further hydrolysis of the lime, causing both fluorine and uranium to fail to meet the standards.

[0091] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A special inhibitor for treating uranium-fluorine-containing wastewater, characterized in that: The raw materials include, by weight: 1-9 parts of titanium dioxide, 90-120 parts of calcium hydroxyphosphate, 10.1-196.2 parts of ferrous chloride and 121-4925 parts of calcium chloride; The preparation method of the special inhibitor for treating uranium-fluorine wastewater comprises the following steps: uniformly mixing titanium dioxide and calcium hydroxyphosphate and then calcining and modifying them to obtain modified calcium hydroxyphosphate; dispersing the modified calcium hydroxyphosphate in ferrous chloride for coating and modification to obtain a mixture; and then dispersing the mixture in calcium chloride for aging and stabilization to obtain the special inhibitor for treating uranium-fluorine wastewater.

2. The special inhibitor for treating uranium-fluorine-containing wastewater according to claim 1, characterized in that: The crystal form of the titanium dioxide is anatase; and the particle size D90 of the titanium dioxide is not greater than 100 nm.

3. The special inhibitor for treating uranium-fluorine-containing wastewater according to claim 1, characterized in that: The particle size of the calcium hydroxyphosphate is not greater than 1 μm.

4. The special inhibitor for treating uranium-fluorine-containing wastewater according to any one of claims 1 to 3, characterized in that: The raw materials include, by weight: 3-5 parts of titanium dioxide, 100 parts of calcium hydroxyphosphate, 10.3-189 parts of ferrous chloride and 375.5-1129.5 parts of calcium chloride.

5. A method for preparing a special inhibitor for treating uranium-fluorine-containing wastewater according to any one of claims 1 to 4, characterized in that: The method comprises the following steps: uniformly mixing titanium dioxide and hydroxy calcium phosphate and then calcining and modifying the mixture to obtain modified hydroxy calcium phosphate; The modified hydroxy calcium phosphate is dispersed in ferrous chloride for coating and modification to obtain a mixture; the mixture is then dispersed in calcium chloride for aging and stabilization to obtain the special inhibitor for treating uranium-fluoride-containing wastewater.

6. The method according to claim 5, characterized in that The calcination modification temperature is 500-850° C. and the calcination time is 1-4 hours.

7. The method according to claim 5, characterized in that The coating and modification steps include: first dissolving ferrous chloride in water to prepare a ferrous chloride solution with a mass concentration of 5-33%, and then dispersing the modified hydroxy calcium phosphate in the ferrous chloride solution for coating and modification under closed conditions for 2-48 hours.

8. The method according to claim 7, characterized in that The mass concentration of ferrous chloride solution is 18-33%.

9. The method according to claim 5, characterized in that The aging and stabilization steps include: first dissolving calcium chloride in water to obtain a calcium chloride solution, then uniformly dispersing the mixture in the calcium chloride solution, the feeding time is 0.8-1.2 hours, and after the feeding is completed, aging and stabilizing for 2-24 hours under closed conditions to obtain the special inhibitor for treating uranium-fluoride wastewater.

10. The method according to claim 9, characterized in that The mass concentration of the calcium chloride solution is 15%-42%, and the weight of the mixture is 6-37.5% of the calcium chloride solution.