A system and method for advanced defluoridation of fluoride-containing wastewater

Abstract

The application belongs to the field of industrial wastewater defluorination, and discloses a system and method for deep defluorination of fluorine-containing wastewater. The system comprises a fluorine-containing wastewater feeding pipeline, a sand filter, an activated carbon adsorption column device, an aluminum-based resin defluorination column device, a regeneration liquid resourceization reaction kettle and a solid-liquid separator; the outlet of the fluorine-containing wastewater feeding pipeline is connected with the fluorine-containing wastewater inlet of the sand filter; the SS-removed wastewater outlet of the sand filter is connected with the SS-removed wastewater inlet of the activated carbon adsorption column device; the COD-removed wastewater outlet of the activated carbon adsorption column device and the mother liquor outlet of the solid-liquid separator are both connected with the COD-removed wastewater inlet of the front column; the regeneration liquid outlet of the front column is connected with the regeneration liquid inlet of the regeneration liquid resourceization reaction kettle; and the reaction liquid outlet of the regeneration liquid resourceization reaction kettle is connected with the material inlet of the solid-liquid separator. The application solves the technical problems that impurity metal ions are introduced in the existing deep defluorination process of fluorine-containing wastewater and fluorine-containing sludge is difficult to be resourceized.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of industrial wastewater defluorination, and more particularly relates to a system and method for deep defluorination of fluorine-containing wastewater. BACKGROUND

[0002] With the development of modern technology, photovoltaic, mine, chemical, electronic, semiconductor, battery, glass manufacturing and other industries will produce different concentrations of fluorine-containing wastewater, in which the concentration of fluoride ions ranges from tens of mg / L to tens of thousands of mg / L. Fluorine-containing wastewater can seriously pollute soil and groundwater, and further damage the metabolic balance of plants, animals and humans, causing great toxic side effects. The existing methods for treating fluorine-containing wastewater include chemical precipitation, coagulation sedimentation, membrane separation and electrochemical method. Among them, the chemical precipitation method is widely used due to its simple operation and low cost. This method is to add lime, quicklime or calcium chloride and other reagents to the wastewater, and the fluoride ions in the wastewater combine with the calcium ions in the reagent to form insoluble calcium fluoride precipitate. Then, through the bridging action of flocculants such as polyacrylamide, flocculation is completed, and after solid-liquid separation, the concentration of fluoride ions can be reduced to about 8-20 mg / L. However, the current relevant standards require that the concentration of fluorine in the central water supply effluent water be ≤1.0 mg / L, so the chemical precipitation method cannot meet the requirements of deep defluorination of fluorine-containing wastewater.

[0003] Currently, for deep defluorination of wastewater, polyaluminum chloride, polyferric sulfate and polyacrylamide and other reagents are generally added, and after reaction, the concentration of fluoride ions in the wastewater can be removed to ≤1 mg / L. However, the above-mentioned reagents generally have low purity, which can introduce impurity metal ions such as aluminum, iron and manganese into the wastewater, and the addition of polyacrylamide can also cause the COD of the wastewater to increase. In addition, the fluorine-containing sludge produced during deep defluorination has complex composition, containing heavy metal ions such as aluminum, iron and manganese, which can cause new pollution. Patent application 202210673977.4 proposes to prepare defluorination agents from aluminum salts, iron salts and lanthanide materials, which can combine with fluoride ions in wastewater and precipitate, reducing the concentration of fluoride ions to ≤1 mg / L. However, this scheme will form a mixed fluoride salt containing iron, aluminum and rare earth elements, and the price of rare earth elements is relatively high, increasing the treatment cost. Patent application 202410512911.6 proposes to add polyaluminum, magnetic iron-zirconium, polybasic magnesium carbonate and other coagulation materials to the wastewater after secondary calcium salt treatment, which increases the precipitation rate of fluoride ions and reduces the concentration of fluoride ions in the effluent to ≤1 mg / L. However, this process produces fluorine-containing mixed sludge with complex composition, which is difficult to recycle, causing waste of fluorine resources.

[0004] Therefore, there is an urgent need to develop a deep defluorination process that can remove fluoride ions in wastewater to ≤1 mg / L, avoid pollution by aluminum, iron and other metal ions, and recycle fluorine-containing sludge. SUMMARY

[0005] The present application aims at the deficiencies of the prior art, and provides a system and method for deep fluorine removal from fluorine-containing wastewater.

[0006] In order to achieve the above-mentioned purpose, the present application provides a system for deep fluorine removal from fluorine-containing wastewater, which comprises a fluorine-containing wastewater feeding pipeline, a sand filter, an activated carbon adsorption column device, an aluminum-based resin fluorine removal column device, a regeneration liquid resourceization reaction kettle and a solid-liquid separator.

[0007] The upper part of the sand filter is provided with a fluorine-containing wastewater inlet, and the lower part is provided with an SS-removed wastewater outlet; the upper part of the activated carbon adsorption column device is provided with an SS-removed wastewater inlet, and the lower part is provided with a COD-removed wastewater outlet; the activated carbon adsorption column device is filled with activated carbon particle fillers;

[0008] The aluminum-based resin fluorine removal column device comprises two aluminum-based resin fluorine removal columns connected in series, the upper part of each aluminum-based resin fluorine removal column is provided with a COD-removed wastewater inlet, a regeneration liquid outlet and an in-column liquid inlet, and the lower part of each aluminum-based resin fluorine removal column is provided with a regenerant inlet and a water outlet; the regenerant inlet is connected with an aluminum-based resin regenerant feeding pipeline and a pure water feeding pipeline; the two aluminum-based resin fluorine removal columns connected in series are alternatively used as a front column and a rear column, the water outlet of the front column is connected with the in-column liquid inlet of the rear column through an in-column liquid outlet pipeline, and the water outlet of the rear column is connected with a water outlet pipeline, so as to form the series connection; the aluminum-based resin fluorine removal column device is filled with aluminum-based resin fillers;

[0009] The regeneration liquid resourceization reaction kettle is provided with a regeneration liquid inlet, a sodium salt feeding port and a reaction liquid outlet; and the solid-liquid separator is provided with a material inlet, an ice crystal outlet and a mother liquor outlet;

[0010] The outlet of the fluorine-containing wastewater feeding pipeline is connected with the fluorine-containing wastewater inlet of the sand filter; the SS-removed wastewater outlet of the sand filter is connected with the SS-removed wastewater inlet of the activated carbon adsorption column device; the COD-removed wastewater outlet of the activated carbon adsorption column device and the mother liquor outlet of the solid-liquid separator are both connected with the COD-removed wastewater inlet of the front column; the regeneration liquid outlet of the front column is connected with the regeneration liquid inlet of the regeneration liquid resourceization reaction kettle; and the reaction liquid outlet of the regeneration liquid resourceization reaction kettle is connected with the material inlet of the solid-liquid separator.

[0011] According to the present application, preferably, the upper part of the sand filter is further provided with a backwash water outlet, and the lower part of the sand filter is further provided with a backwash water inlet; and the fluorine-containing wastewater feeding pipeline is further connected with the backwash water inlet of the sand filter.

[0012] According to the application, preferably, the upper part of the active carbon adsorption column device is further provided with a regenerative gas outlet, and the lower part of the active carbon adsorption column device is further provided with a hot air inlet; the hot air inlet is connected with a hot air feeding pipeline.

[0013] According to the application, preferably, the active carbon adsorption column device comprises a plurality of active carbon adsorption columns connected in parallel and working alternately; the upper part of each active carbon adsorption column is provided with an SS removal wastewater inlet and a regenerative gas outlet, and the lower part of each active carbon adsorption column is provided with a COD removal wastewater outlet and a hot air inlet; the SS removal wastewater outlet of the sand filter is connected with the SS removal wastewater inlet of the working active carbon adsorption column; the COD removal wastewater outlet of the working active carbon adsorption column and the mother liquor outlet of the solid-liquid separator are both connected with the COD removal wastewater inlet of the front column.

[0014] According to the application, preferably, in the active carbon adsorption column, the ratio of the packing height of the active carbon particle filler to the diameter of the active carbon adsorption column is 0.5-5:1.

[0015] According to the application, preferably, the particle size of the active carbon particle filler is 1-5 mm.

[0016] According to the application, preferably, the iodine value of the active carbon particle filler is 600-1000 mg / g.

[0017] In the application, the column body of the active carbon adsorption column is made of high-temperature resistant enamel, or the column body of the active carbon adsorption column is lined with an enamel material.

[0018] According to the application, preferably, in the aluminum-based resin fluoride removal column, the ratio of the packing height of the aluminum-based resin filler to the diameter of the aluminum-based resin fluoride removal column is 0.5-5:1.

[0019] According to the application, preferably, the particle size of the aluminum-based resin filler is 0.3-2 mm.

[0020] In the application, the column body of the aluminum-based resin fluoride removal column is preferably made of an acid-resistant material. The series connection of the front column and the rear column enables the COD removal wastewater and the mother liquor from the solid-liquid separator to pass through the aluminum-based resin fluoride removal column device in an up-and-down manner, and finally obtain the product water.

[0021] In the application, the regenerative liquid resourceization reaction kettle is provided with a stirring device, so that the reaction in the regenerative liquid resourceization reaction kettle can be fully carried out through stirring.

[0022] The inlet and outlet of each device in the application are provided with valves, so as to control when to feed and discharge.

[0023] Another aspect of the present application provides a method for deep fluorine removal from fluorine-containing wastewater, which uses the system described above and comprises the following steps:

[0024] S1: sending the fluorine-containing wastewater from a fluorine-containing wastewater inlet into the sand filter, filtering to obtain SS-removed wastewater;

[0025] S2: sending the SS-removed wastewater into the activated carbon adsorption column device, adsorbing COD in the SS-removed wastewater by the activated carbon particles to obtain COD-removed wastewater;

[0026] S3: sending the COD-removed wastewater and the mother liquor from the solid-liquid separator into the front column of the aluminum-based resin fluorine removal column device, adsorbing fluorine ions in the liquid in the aluminum-based resin fluorine removal column device by the aluminum-based resin filler, and obtaining water production at the outlet of the water production pipeline of the rear column;

[0027] S4: when the fluorine ion content in the water production obtained in the step S3 is ≥1 mg / L, stopping the operation of the aluminum-based resin fluorine removal column device, sending a regenerant and pure water into the front column through the regenerant inlet of the front column in sequence to regenerate the front column, obtaining a regeneration liquid at the regeneration liquid outlet of the front column; sending the regeneration liquid and sodium salt into the regeneration liquid resourceization reaction kettle at the same time, obtaining a reaction liquid through reaction; and sending the reaction liquid into the solid-liquid separator for solid-liquid separation to obtain a resourceization product cryolite and the mother liquor.

[0028] In the present application, the "SS" refers to suspended solids, and the "COD" refers to chemical oxygen demand.

[0029] According to the present application, preferably, in the step S1:

[0030] the fluorine ion content of the fluorine-containing wastewater is ≤20 mg / L;

[0031] the method further comprises: making the fluorine-containing wastewater enter the sand filter from a backwashing water inlet, and backwashing the sand filter by the down-up method.

[0032] In the present application, the sign for judging whether the sand filter needs to be backwashed is the pressure difference between the inlet and outlet of the sand filter. When the pressure difference between the inlet and outlet of the sand filter reaches 0.1 MPa, the sand filter needs to be backwashed by the down-up method, and the solid pollutants washed out are discharged from the backwashing water outlet.

[0033] According to the present invention, preferably, step S2 involves feeding the SS-removing wastewater into a working activated carbon adsorption column of the activated carbon adsorption column device, where activated carbon granules in the working activated carbon adsorption column adsorb the COD in the SS-removing wastewater to obtain COD-removed wastewater; after the working activated carbon adsorption column becomes saturated, it is switched to another activated carbon adsorption column connected in parallel to continue adsorption; at the same time, hot air is introduced from the hot air inlet into the saturated activated carbon adsorption column for regeneration treatment to obtain a regenerated activated carbon adsorption column for reuse.

[0034] In this invention, as a preferred embodiment, such as Figure 1 As shown, the SS-removed wastewater enters activated carbon adsorption column 2-A (No. 1). The SS-removed wastewater inlet valve 21 and the COD-removed wastewater outlet valve 22 of activated carbon adsorption column 2-A are opened. The hot air inlet valve 23 and the regeneration gas outlet valve 24 of activated carbon adsorption column 2-A, as well as all valves of activated carbon adsorption column 2-B, are closed to complete the COD removal process, yielding COD-removed wastewater. After activated carbon adsorption column 2-A becomes saturated, the SS-removed wastewater inlet valve 21 and the COD-removed wastewater outlet valve 22 of activated carbon adsorption column 2-A are closed. The SS-removed wastewater inlet valve 21 and the COD-removed wastewater outlet valve 22 of activated carbon adsorption column 2-B are then opened, switching the removal of COD from the wastewater to activated carbon adsorption column 2-B. Simultaneously open the hot air inlet valve 23 and the regeneration gas outlet valve 24 of the No. 1 activated carbon adsorption column 2-A. Hot air is introduced into the No. 1 activated carbon adsorption column 2-A from the bottom to regenerate it, and a regenerated activated carbon adsorption column is obtained for reuse.

[0035] According to the present invention, preferably, the temperature of the hot air is 400-900°C.

[0036] According to the present invention, preferably, the feed flow rate of the SS-removed wastewater is 8-12 BV / h.

[0037] According to the present invention, preferably, in step S3:

[0038] The fluoride ion content in the COD-removed wastewater is ≤20mg / L, SS ≤10mg / L, and COD ≤20mg / L;

[0039] The fluoride ion content of the produced water obtained from the outlet of the product water pipeline of the rear column is ≤1 mg / L;

[0040] The feed flow rate of the COD-removed wastewater is 8-12 BV / h.

[0041] In the present application, the aluminum-based resin filler adsorbs the fluorine ions in the liquid in the aluminum-based resin fluorine removal column device, so that the fluorine ions are retained on the aluminum-based resin, and then the fluorine ion content of the produced water at the outlet of the water production pipeline of the post-column is ≤1 mg / L. The regenerant and pure water are sequentially sent from the regenerant inlet of the pre-column to regenerate the pre-column, and the regeneration mechanism is that the fluorine ions and the aluminum ions in the regenerant easily form a complex, and under the action of high-concentration regenerant, the aluminum ions in the regenerant combine with the fluorine ions in the resin to form Al-F compounds, and the subsequent pure water washing can remove the residual aluminum ions to restore the ion exchange function of the resin.

[0042] According to the present application, preferably, in the step S4:

[0043] The regenerant is an aluminum chloride aqueous solution with a mass concentration of 0.1-10% and / or an aluminum sulfate aqueous solution with a mass concentration of 0.1-10%;

[0044] The sodium salt is at least one of sodium chloride, sodium sulfate, sodium carbonate and sodium hydroxide;

[0045] The reaction end point pH value in the regenerant resourceization reaction kettle is 3-8, and the reaction time in the regenerant resourceization reaction kettle is 5-120 min;

[0046] The method further comprises: periodically performing the steps S1-S4, and taking the pre-column after the regeneration treatment in the step S4 as the post-column in the next period, and taking the post-column without the regeneration treatment as the pre-column in the next period.

[0047] In the present application, as a preferred scheme, as shown in Figure 1 The regeneration liquid resourceization reaction kettle is connected to the outlet of the post-column, and the outlet of the regeneration liquid resourceization reaction kettle is connected to the inlet of the pre-column in the next period.

[0048] After the COD wastewater and the mother liquor from the solid-liquid separator enter the No. 1 aluminum-based resin fluorine removal column 3-1, open: the COD wastewater inlet valve 311 of the No. 1 aluminum-based resin fluorine removal column, the in-column liquid outlet pipeline valve 331 of the No. 1 aluminum-based resin fluorine removal column, the in-column liquid inlet valve 342 of the No. 2 aluminum-based resin fluorine removal column, and the water production pipeline valve 322 of the No. 2 aluminum-based resin fluorine removal column; close: the COD wastewater inlet valve 312 of the No. 2 aluminum-based resin fluorine removal column, the in-column liquid outlet pipeline valve 332 of the No. 2 aluminum-based resin fluorine removal column, the in-column liquid inlet valve 341 of the No. 1 aluminum-based resin fluorine removal column, the water production pipeline valve 321 of the No. 1 aluminum-based resin fluorine removal column, the regenerant inlet valve 351 of the No. 1 aluminum-based resin fluorine removal column, the regenerant inlet valve 352 of the No. 2 aluminum-based resin fluorine removal column, the regeneration liquid outlet valve 361 of the No. 1 aluminum-based resin fluorine removal column, and the regeneration liquid outlet valve 362 of the No. 2 aluminum-based resin fluorine removal column, complete the deep fluorine removal process, and the produced water is discharged through the water production pipeline valve 322 of the No. 2 aluminum-based resin fluorine removal column.

[0049] When the fluorine ion content in the product water of the product water pipeline valve 322 of the No. 2 aluminum-based resin fluorine removal column is greater than or equal to 1 mg / L, stop the operation, close the COD removal wastewater inlet valve 311 of the No. 1 aluminum-based resin fluorine removal column, the in-column liquid outlet pipeline valve 331 of the No. 1 aluminum-based resin fluorine removal column, open the regenerant inlet valve 351 of the No. 1 aluminum-based resin fluorine removal column, the regenerant outlet valve 361 of the No. 1 aluminum-based resin fluorine removal column, and sequentially open the aluminum-based resin regenerant feeding pipeline valve 310 and the pure water feeding pipeline valve 39, so that the regenerant and the pure water are sequentially fed, the regeneration of the No. 1 aluminum-based resin fluorine removal column 3-1 is completed, and the regenerant liquid enriched with fluorine ions is sent to the regenerant liquid resource reaction kettle 4.

[0050] After the regeneration of the No. 1 aluminum-based resin fluorine removal column 3-1, open the COD removal wastewater inlet valve 312 of the No. 2 aluminum-based resin fluorine removal column, the in-column liquid outlet pipeline valve 332 of the No. 2 aluminum-based resin fluorine removal column, the in-column liquid inlet valve 341 of the No. 1 aluminum-based resin fluorine removal column, and the product water pipeline valve 321 of the No. 1 aluminum-based resin fluorine removal column, close the in-column liquid inlet valve 342 of the No. 2 aluminum-based resin fluorine removal column, the product water pipeline valve 322 of the No. 2 aluminum-based resin fluorine removal column, the regenerant inlet valve 351 of the No. 1 aluminum-based resin fluorine removal column, the regenerant inlet valve 352 of the No. 2 aluminum-based resin fluorine removal column, the regenerant outlet valve 361 of the No. 1 aluminum-based resin fluorine removal column, and the regenerant outlet valve 362 of the No. 2 aluminum-based resin fluorine removal column, so that the No. 2 aluminum-based resin fluorine removal column 3-2 is used as a front column and the No. 1 aluminum-based resin fluorine removal column 3-1 is used as a rear column to continue the operation.

[0051] In the present application, the regenerant liquid contains fluorine ions and aluminum ions, therefore, the regenerant liquid reacts with sodium salt to generate sodium fluoroaluminate (cryolite). The reaction equation is H3AlF6+3Na + →Na3AlF6+3H + .

[0052] The beneficial effects of the technical solution of the present application are as follows: the present application solves the technical problems of introducing impurity metal ions and fluorine-containing sludge which is difficult to be recycled in the existing deep fluorine removal process of fluorine-containing wastewater. Specifically:

[0053] 1. The present application realizes deep fluorine removal of fluorine-containing wastewater, so that the fluorine ion concentration in the product water of the rear column of the aluminum-based resin fluorine removal column device is less than or equal to 1 mg / L, and the present application removes fluorine by aluminum-based resin, so that the product water of the present application does not contain impurity metal ions such as aluminum and iron, and meets the discharge standard.

[0054] 2. The present application recycles the aluminum-based resin regenerant containing high-concentration fluorine ions, that is, a small amount of fluorine in the fluorine-containing wastewater is concentrated by aluminum-based resin and then recycled to obtain the resource product cryolite, thereby avoiding the generation of fluorine-containing sludge, saving sludge disposal costs, and generating economic benefits.

[0055] 3、The present application removes COD and fluoride ions in wastewater respectively by using high-iodine-value activated carbon and aluminum-based resin, which can effectively prevent COD in wastewater from occupying exchange sites of aluminum-based resin, affecting the exchange capacity of aluminum-based resin, and prolonging the service life of aluminum-based resin.

[0056] Other features and advantages of the present application will be described in detail in the following specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0057] The above and other objects, features and advantages of the present application will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which like reference characters refer to like parts throughout the several views.

[0058] Figure 1 A schematic diagram of a deep fluorine removal system for fluorine-containing wastewater provided by Embodiment 1 of the present application is shown.

[0059] The reference signs are explained as follows:

[0060] 1, sand filter; 11, fluorine-containing wastewater inlet valve; 12, backwash water inlet valve; 13, SS removal wastewater outlet valve; 14, backwash water outlet valve;

[0061] 2-A, No. 1 activated carbon adsorption column; 2-B, No. 2 activated carbon adsorption column; 21, SS removal wastewater inlet valve; 22, COD removal wastewater outlet valve; 23, hot air inlet valve; 24, regenerant outlet valve;

[0062] 3-1, No. 1 aluminum-based resin fluoride removal column; 3-2, No. 2 aluminum-based resin fluoride removal column;

[0063] 311, COD removal wastewater inlet valve of No. 1 aluminum-based resin fluoride removal column; 321, water production pipeline valve of No. 1 aluminum-based resin fluoride removal column; 331, in-column liquid outlet pipeline valve of No. 1 aluminum-based resin fluoride removal column; 341, in-column liquid inlet valve of No. 1 aluminum-based resin fluoride removal column; 351, regenerant inlet valve of No. 1 aluminum-based resin fluoride removal column; 361, regenerant outlet valve of No. 1 aluminum-based resin fluoride removal column;

[0064] 312, COD removal wastewater inlet valve of No. 2 aluminum-based resin fluoride removal column; 322, water production pipeline valve of No. 2 aluminum-based resin fluoride removal column; 332, in-column liquid outlet pipeline valve of No. 2 aluminum-based resin fluoride removal column; 342, in-column liquid inlet valve of No. 2 aluminum-based resin fluoride removal column; 352, regenerant inlet valve of No. 2 aluminum-based resin fluoride removal column; 362, regenerant outlet valve of No. 2 aluminum-based resin fluoride removal column;

[0065] 310, aluminum-based resin regenerant feeding pipeline valve; 39, pure water feeding pipeline valve;

[0066] 4, Regeneration liquid resource reactor; 38, Regeneration liquid inlet; 41, Agitation motor; 42, Agitation paddle; 43, Sodium salt feeding port;

[0067] 5, Solid-liquid separator; 44, Material inlet; 51, Mother liquor outlet; 52, Cryolite outlet; 53, Mother liquor outlet valve;

[0068] 61, Fluorine-containing wastewater feeding pipeline; 62, Hot air feeding pipeline; 63, Aluminum-based resin regenerant feeding pipeline; 64, Pure water feeding pipeline; 65, Sodium salt feeding pipeline. DETAILED DESCRIPTION

[0069] The preferred embodiments of the present application will be described in more detail below. Although the preferred embodiments of the present application are described below, it is understood that the present application can be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided so that the present application will be thorough and complete, and will fully convey the scope of the present application to those skilled in the art.

[0070] In the following examples:

[0071] The aluminum-based resin filler is purchased from Lianglet MTS9510PF imino phosphonic acid chelating resin, which is soaked in 2-3% aluminum chloride solution for 8h, 0.1mol / L hydrochloric acid for 2h, and distilled water for 4-5 times until pH=3-4, and then loaded into the resin defluorination column, with an average particle size of 0.3-0.8mm.

[0072] The activated carbon particle filler is prepared by the following steps: taking Hainan waste coconut shell as raw material, first slowly heating to 600°C in air for carbonization for 2h, then activating at 1000°C under nitrogen for 2h, and then screening to obtain particles with a particle size of 1-3mm, an iodine value of 800mg / g, a bulk density of 0.5-0.55g / cm³, and a pore size of 2-50nm>15%.

[0073] Example 1

[0074] This embodiment provides a deep defluorination system for fluorine-containing wastewater, as shown in Figure 1 The system includes a fluorine-containing wastewater feeding pipeline 61, a sand filter 1, an activated carbon adsorption column device, an aluminum-based resin defluorination column device, a regeneration liquid resource reactor 4, and a solid-liquid separator 5.

[0075] The sand filter 1 is provided with a fluorine-containing wastewater inlet and a backwash water outlet at the upper part, and an SS-removed wastewater outlet and a backwash water inlet at the lower part.

[0076] The active carbon adsorption column device comprises two active carbon adsorption columns (No. 1 active carbon adsorption column 2-A and No. 2 active carbon adsorption column 2-B, one standby, when the No. 1 active carbon adsorption column 2-A is saturated, the other No. 2 active carbon adsorption column 2-B is switched to continue working) working in parallel and alternately; the upper part of each active carbon adsorption column is provided with an SS removal wastewater inlet and a regeneration gas outlet, and the lower part of each active carbon adsorption column is provided with a COD removal wastewater outlet and a hot air inlet, which is connected with a hot air inlet pipeline 62; each active carbon adsorption column is filled with active carbon particle filler; the filling height of the active carbon particle filler in each active carbon adsorption column is 1.3 m, and the diameter of the active carbon adsorption column is 1 m;

[0077] The aluminum-based resin fluoride removal column device comprises two aluminum-based resin fluoride removal columns connected in series, the upper part of each aluminum-based resin fluoride removal column is provided with a COD removal wastewater inlet, a regeneration liquid outlet and an in-column liquid inlet, and the lower part of each aluminum-based resin fluoride removal column is provided with a regeneration agent inlet and a water outlet; the regeneration agent inlet is connected with an aluminum-based resin regeneration agent inlet pipeline 63 and a pure water inlet pipeline 64; the two aluminum-based resin fluoride removal columns connected in series are alternatively used as a front column and a rear column, the water outlet of the front column is connected with the in-column liquid inlet of the rear column through an in-column liquid outlet pipeline, and the water outlet of the rear column is connected with a water outlet pipeline, so as to form the series connection; each aluminum-based resin fluoride removal column is filled with aluminum-based resin filler, the filling height of the aluminum-based resin filler in each aluminum-based resin fluoride removal column is 1.3 m, and the diameter of the aluminum-based resin fluoride removal column is 1 m;

[0078] The regeneration liquid resourceization reaction kettle 4 is provided with a regeneration liquid inlet 38, a sodium salt feeding port 43, a reaction liquid outlet, a stirring motor 41 and a stirring paddle 42; the solid-liquid separator 5 is provided with a material inlet 44, an ice crystal outlet 52 and a mother liquor outlet 51;

[0079] The outlet of the fluorine-containing wastewater inlet pipeline 61 is connected with the fluorine-containing wastewater inlet and the backwashing water inlet of the sand filter 1 respectively; the SS removal wastewater outlet of the sand filter 1 is connected with the SS removal wastewater inlet of the working No. 1 active carbon adsorption column 2-A; the COD removal wastewater outlet of the working No. 1 active carbon adsorption column 2-A and the mother liquor outlet 51 of the solid-liquid separator are connected with the COD removal wastewater inlet of the front column; the regeneration liquid outlet of the front column is connected with the regeneration liquid inlet 38 of the regeneration liquid resourceization reaction kettle; the reaction liquid outlet of the regeneration liquid resourceization reaction kettle 4 is connected with the material inlet 44 of the solid-liquid separator.

[0080] In this embodiment, first, the No. 1 aluminum-based resin fluoride removal column 3-1 is used as the front column, the No. 2 aluminum-based resin fluoride removal column 3-2 is used as the rear column, and after the step S4 of the deep fluoride removal method of the fluorine-containing wastewater, the front column (i.e. the No. 1 aluminum-based resin fluoride removal column 3-1) after the regeneration treatment of the step S4 is used as the rear column in the next cycle, and the rear column (i.e. the No. 2 aluminum-based resin fluoride removal column 3-2) without the regeneration treatment is used as the front column in the next cycle. Valves are arranged on the inlets and outlets of each device in this embodiment to control when the materials are fed and discharged.

[0081] This embodiment also provides a deep fluoride removal method of fluorine-containing wastewater, which uses the system described above.

[0082] The fluorine-containing wastewater treated in this embodiment uses fluorine-containing mine water generated on site of a gold mine in Shandong, and the water quality characteristics are shown in Table 1, wherein: F - The detection method uses ion selective electrode method; the detection method of COD is performed according to HJ / T399-2007; the detection of pH value is completed by using a pH meter; and the detection method of SS is GB 18918 2002.

[0083] The method comprises the following steps:

[0084] S1: The fluorine-containing wastewater is fed from the fluorine-containing wastewater inlet into the sand filter 1, filtered to obtain SS-removed wastewater; when the pressure difference between the inlet and outlet of the sand filter 1 reaches 0.1 MPa, the fluorine-containing wastewater is fed from the backwashing water inlet into the sand filter 1, and the sand filter 1 is backwashed by the way of down-up, and the solid pollutants washed out are discharged from the backwashing water outlet;

[0085] S2: The SS-removed wastewater (the feed flow rate is 10 BV / h) is fed from the SS-removed wastewater inlet into the working No. 1 activated carbon adsorption column 2-A of the activated carbon adsorption column device, and the COD in the SS-removed wastewater is adsorbed by the activated carbon particles in the working No. 1 activated carbon adsorption column 2-A to obtain COD-removed wastewater (SS≤10 mg / L); after the working No. 1 activated carbon adsorption column 2-A is saturated, another parallel No. 2 activated carbon adsorption column 2-B is switched to continue working and adsorbing; at the same time, hot air (600℃) is introduced into the saturated No. 1 activated carbon adsorption column 2-A from the hot air inlet to regenerate the column for 30 min to obtain regenerated activated carbon adsorption column for reuse;

[0086] S3: The COD wastewater (feed flow rate of 10 BV / h) and the mother liquor from the solid-liquid separator 5 are fed into the front column (aluminum-based resin fluoride removal column 3-1) of the aluminum-based resin fluoride removal column device, the fluorine ions in the liquid in the aluminum-based resin fluoride removal column device are adsorbed by the aluminum-based resin filler, and the produced water (fluorine ion content ≤1 mg / L) is obtained at the outlet of the water production pipeline of the rear column (aluminum-based resin fluoride removal column 3-2).

[0087] S4: When the fluorine ion content in the produced water obtained in the step S3 is ≥1 mg / L, the operation of the aluminum-based resin fluoride removal column device is stopped, the regenerant (2-3% aluminum chloride aqueous solution) and pure water (regenerant and pure water feed flow rate of 2-3 BV / h) are sequentially fed into the front column through the regenerant inlet of the front column, the front column is subjected to regeneration treatment, and the regeneration liquid is obtained at the regeneration liquid outlet of the front column; the regeneration liquid and sodium salt (sodium chloride and sodium carbonate, mass ratio of 1:1) are simultaneously fed into the regeneration liquid resourceization reaction kettle 4, stirred and reacted for about 30 min, the reaction end point pH is controlled to be 4-5, and the reaction is completed to obtain a reaction liquid; the reaction liquid is fed into the solid-liquid separator 5 for solid-liquid separation to obtain a resourceization product cryolite 8-10 kg and the mother liquor (fluorine ion content of 20-50 mg / L, and the regenerant and pure water feed flow rate is small, so that the fluorine ions in the mother liquor are concentrated).

[0088] The current cycle is completed;

[0089] The present embodiment is carried out for ten cycles, and the steps S1-S4 are carried out in each cycle, and the front column (aluminum-based resin fluoride removal column 3-1) after the regeneration treatment in the step S4 of the current cycle is used as the rear column of the next cycle, and the rear column (aluminum-based resin fluoride removal column 3-2) without regeneration treatment is used as the front column of the next cycle.

[0090] The aluminum-based resin exchange capacity and the purity of the resourceization recovery product cryolite in each cycle are shown in Table 2, wherein:

[0091] The purity of the cryolite is detected according to GB / T 4291-2017, and in Table 2: the percentage content of the cryolite refers to the sum of the percentages of fluorine, aluminum and sodium obtained by X-ray fluorescence spectroscopy; the running time refers to the time from when the COD wastewater (feed flow rate of 10 V / h) and the mother liquor from the solid-liquid separator are fed into the front column of the aluminum-based resin fluoride removal column device to when the fluorine ion content in the produced water obtained in the step S3 is ≥1 mg / L; the water treatment amount refers to the amount of water treated by the aluminum-based resin fluoride removal column device; and the aluminum-based resin exchange capacity is the product of the water amount treated in each cycle and the fluorine ion concentration, i.e. the absolute amount of adsorbed fluorine ions divided by the volume of resin loading.

[0092] Table 1

[0093]

[0094] Table 2

[0095]

[0096] From the above table 2, in the process of ten cycles, the exchange capacity of aluminum-based resin is relatively stable, without obvious decrease, and the purity and yield of recovered cryolite product are also relatively stable.

[0097] The foregoing description of the various embodiments of the application has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the application to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. It is intended that the scope of the application be limited not with this detailed description, but rather by the claims appended hereto.

Claims

1. A system for advanced defluorination of fluorine-containing wastewater, characterized in that, The system comprises a fluorine-containing wastewater feed pipeline, a sand filter, an activated carbon adsorption column device, an aluminum-based resin fluoride removal column device, a regeneration liquid resourceization reaction kettle and a solid-liquid separator; The upper part of the sand filter is provided with a fluorine-containing wastewater inlet, and the lower part is provided with an SS removal wastewater outlet; the upper part of the activated carbon adsorption column device is provided with an SS removal wastewater inlet, and the lower part is provided with a COD removal wastewater outlet; the activated carbon adsorption column device is filled with activated carbon particle fillers; The aluminum-based resin fluoride removal column device comprises two aluminum-based resin fluoride removal columns connected in series, the upper part of each aluminum-based resin fluoride removal column is provided with a COD removal wastewater inlet, a regeneration liquid outlet and an in-column liquid inlet, and the lower part of each aluminum-based resin fluoride removal column is provided with a regenerant inlet and a water outlet; the regenerant inlet is connected with an aluminum-based resin regenerant feed pipeline and a pure water feed pipeline; the two aluminum-based resin fluoride removal columns connected in series are alternatively used as a front column and a rear column, the water outlet of the front column is connected with the in-column liquid inlet of the rear column through an in-column liquid outlet pipeline, and the water outlet of the rear column is connected with a water outlet pipeline, so as to form the series connection; the aluminum-based resin fluoride removal column device is filled with aluminum-based resin fillers; The regeneration liquid resourceization reaction kettle is provided with a regeneration liquid inlet, a sodium salt feed inlet and a reaction liquid outlet; and the solid-liquid separator is provided with a material inlet, an ice crystal outlet and a mother liquor outlet; The outlet of the fluorine-containing wastewater feed pipeline is connected with the fluorine-containing wastewater inlet of the sand filter; the SS removal wastewater outlet of the sand filter is connected with the SS removal wastewater inlet of the activated carbon adsorption column device; the COD removal wastewater outlet of the activated carbon adsorption column device and the mother liquor outlet of the solid-liquid separator are connected with the COD removal wastewater inlet of the front column; the regeneration liquid outlet of the front column is connected with the regeneration liquid inlet of the regeneration liquid resourceization reaction kettle; and the reaction liquid outlet of the regeneration liquid resourceization reaction kettle is connected with the material inlet of the solid-liquid separator; In the aluminum-based resin fluoride removal column, the ratio of the filling height of the aluminum-based resin filler to the diameter of the aluminum-based resin fluoride removal column is 0.5-5:1; The particle size of the aluminum-based resin filler is 0.3-2 mm.

2. The system for advanced defluorination of fluorochemical wastewater according to claim 1, wherein, The upper part of the sand filter is further provided with a backwash water outlet, and the lower part of the sand filter is further provided with a backwash water inlet; and the fluorine-containing wastewater feed pipeline is further connected with the backwash water inlet of the sand filter.

3. The system for advanced defluorination of fluorochemical wastewater according to claim 1, wherein, The upper part of the activated carbon adsorption column device is further provided with a regeneration gas outlet, and the lower part of the activated carbon adsorption column device is further provided with a hot air inlet; and the hot air inlet is connected with a hot air feed pipeline.

4. The deep fluoride removal system for fluorine-containing wastewater according to claim 3, wherein The activated carbon adsorption column device comprises a plurality of activated carbon adsorption columns connected in parallel and working alternately; the upper part of each activated carbon adsorption column is provided with an SS removal wastewater inlet and a regeneration gas outlet, and the lower part of each activated carbon adsorption column is provided with a COD removal wastewater outlet and a hot air inlet; the SS removal wastewater outlet of the sand filter is connected with the SS removal wastewater inlet of the working activated carbon adsorption column; the COD removal wastewater outlet of the working activated carbon adsorption column and the mother liquor outlet of the solid-liquid separator are connected with the COD removal wastewater inlet of the front column; The ratio of the packing height of the activated carbon granular filler to the diameter of the activated carbon adsorption column is 0.5-5:1; The particle size of the activated carbon granular filler is 1-5 mm; The iodine value of the activated carbon granular filler is 600-1000 mg / g.

5. A method for advanced defluoridation of fluorine-containing wastewater, characterized in that, The method adopts the system of any one of claims 1-4, and comprises the following steps: S1: sending the fluorine-containing wastewater from a fluorine-containing wastewater inlet into the sand filter, filtering to obtain SS-removed wastewater; S2: sending the SS-removed wastewater into the activated carbon adsorption column device, adsorbing COD in the SS-removed wastewater by the activated carbon granular filler to obtain COD-removed wastewater; S3: sending the COD-removed wastewater and the mother liquor from the solid-liquid separator into the front column of the aluminum-based resin fluorine removal column device, adsorbing fluorine ions in the liquid in the aluminum-based resin fluorine removal column device by the aluminum-based resin filler, and obtaining product water at the outlet of the water production pipeline of the rear column; S4: when the fluorine ion content in the product water obtained in the step S3 is ≥1 mg / L, stopping the operation of the aluminum-based resin fluorine removal column device, sending a regenerant and pure water into the front column through the regenerant inlet of the front column in sequence to regenerate the front column, obtaining a regeneration liquid at the regeneration liquid outlet of the front column, and simultaneously sending the regeneration liquid and a sodium salt into the regeneration liquid resourceization reaction kettle to obtain a reaction liquid through reaction, sending the reaction liquid into the solid-liquid separator for solid-liquid separation to obtain a resourceization product cryolite and the mother liquor.

6. The method for advanced defluorination of fluorochemical wastewater according to claim 5, wherein, In the step S1: The fluorine ion content in the fluorine-containing wastewater is ≤20 mg / L; The method further comprises: making the fluorine-containing wastewater enter the sand filter from a backwashing water inlet, and backwashing the sand filter by the down-up method.

7. The method for advanced defluorination of fluorochemical wastewater according to claim 5, wherein, The step S2 is: sending the SS-removed wastewater into a working activated carbon adsorption column of the activated carbon adsorption column device, adsorbing COD in the SS-removed wastewater by the activated carbon granular filler in the working activated carbon adsorption column to obtain COD-removed wastewater; after the working activated carbon adsorption column is saturated, switching to another activated carbon adsorption column in parallel to continue working and adsorbing; at the same time, hot air is introduced into the saturated activated carbon adsorption column from a hot air inlet to regenerate the saturated activated carbon adsorption column to obtain a regenerated activated carbon adsorption column for reuse; The temperature of the hot air is 400-900 ℃; The feed flow rate of the SS-removed wastewater is 8-12 BV / h.

8. The method for advanced defluorination of fluorochemical wastewater according to claim 5, wherein, In the step S3: The fluorine ion content in the COD-removed wastewater is ≤20 mg / L, the SS is ≤10 mg / L, and the COD is ≤20 mg / L; The fluorine ion content in the product water obtained at the outlet of the water production pipeline of the rear column is ≤1 mg / L; The feed flow rate of the COD-removed wastewater is 8-12 BV / h.

9. The method for advanced defluorination of fluorochemical wastewater according to claim 5, wherein, In the step S4: The regenerant is an aluminum chloride aqueous solution with a mass concentration of 0.1-10% and / or an aluminum sulfate aqueous solution with a mass concentration of 0.1-10%; The sodium salt is at least one of sodium chloride, sodium sulfate, sodium carbonate and sodium hydroxide; The reaction end point pH value in the regeneration liquid resource reaction kettle is 3-8; the reaction time in the regeneration liquid resource reaction kettle is 5-120 min; The method further comprises: periodically performing steps S1-S4, and taking the front column after the regeneration treatment of step S4 as the rear column of the next period, and taking the rear column without the regeneration treatment as the front column of the next period.

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