Method for removing fluorine from fluorine-containing wastewater

Abstract

The present application belongs to the technical field of industrial wastewater treatment, and particularly relates to a method for removing fluorine from fluorine-containing wastewater. The method comprises the following steps: adjusting the fluorine-containing wastewater to be acidic, adding a complexing agent to the wastewater, and stirring until the complexing is complete; making the stirred wastewater flow through an adsorption column provided with a chelating resin to obtain an adsorption column containing fluorine and the complexing agent; and eluting the saturated adsorption column with an eluent to elute out solid fluorides. The present application uses the chelating resin to perform deep fluorine removal, the resin can be recycled after adsorption and desorption, and the cost of fluorine removal is reduced. The obtained fluoride solid can be sold alone or used as a raw material for cerium or fluorine, thereby realizing comprehensive utilization of cerium and fluorine.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of industrial wastewater treatment, and particularly relates to a method for removing fluorine from fluorine-containing wastewater. BACKGROUND

[0002] Fluorine is one of the most difficult substances to treat in water treatment, which is usually derived from the metallurgy, chemical industry, electroplating, printing and dyeing industries, and fluoride is a toxic and strongly corrosive substance. If it is directly discharged into the environment without treatment, it will cause serious harm to the ecological environment and human health. At present, the commonly used methods for treating fluorine-containing wastewater at home and abroad mainly include precipitation, coagulation, adsorption and the like. The prior art CN202211013473.6 discloses a method for removing fluorine by rare earth assisted precipitation, wherein a soluble rare earth salt is put into fluorine-containing wastewater, and after dissolution, a soluble calcium salt and a phosphate salt are added, and then the pH value of the solution is adjusted to make the rare earth ions, calcium ions and phosphate ions form a coprecipitate with fluorine ions. However, the alkali consumption of the method is large, and a large amount of fluorine-containing waste residue is formed. The prior art CN201910685193.1 discloses a method for removing fluoride from water, which realizes the removal of fluorine in wastewater through pretreatment, copper-aluminum internal electrolysis reaction, precipitation reaction and coagulation reaction. The treatment process is long, the reaction steps are many, and the operation is relatively complicated. The prior art CN202011353076.4 discloses a method for adsorbing fluorine in fluorine-containing wastewater that has been pretreated by using a metal chelate resin. The chelate resin is prepared by using polyaluminum chloride and ferric chloride as metal chelating agents and styrene-divinylbenzene as a skeleton. However, the resin used in the patent cannot be recycled.

[0003] The discharge standard of fluorine in fluorine-containing wastewater in many cities has been reduced to 5 mg / L. In view of such stringent discharge standards, a method for deeply purifying fluorine-containing wastewater is needed. SUMMARY

[0004] To solve the problems in the prior art, the main purpose of the present application is to provide a method for removing fluorine from fluorine-containing wastewater, which realizes the deep removal of fluorine in wastewater and also realizes the recycling of fluorine.

[0005] To solve the above technical problems, according to one aspect of the present application, the present application provides the following technical scheme:

[0006] A method for removing fluorine from fluorine-containing wastewater, comprising the following steps:

[0007] S1, adjusting the fluorine-containing wastewater to be acidic, adding a complexing agent to the wastewater, and stirring until the complexing is complete;

[0008] S2, flowing the wastewater after stirring in step S1 through an adsorption column provided with a chelating resin to obtain an adsorption column containing fluorine and a complexing agent;

[0009] S3. Elute the saturated adsorption column with eluent to remove solid fluoride.

[0010] In this invention, a complexing agent is added to complex with fluoride in the wastewater. After complexation, the wastewater is passed through an adsorption column containing extraction resin for further neutral complexation reaction, thereby achieving deep removal of fluoride from the wastewater. After elution and reduction, the fluoride-loaded extraction resin yields solid fluoride, which can be recovered after treatment.

[0011] As a preferred embodiment of the method for removing fluoride from fluoride-containing wastewater according to the present invention, in step S1, the complexing agent is one or a mixture of two of Ce(SO4)2 and Ce(NO3)4 in any proportion.

[0012] As a preferred embodiment of the method for removing fluoride from fluoride-containing wastewater according to the present invention, in step S1, the pH of the fluoride-containing wastewater is adjusted to 2-6.

[0013] In a preferred embodiment of the method for removing fluoride from fluoride-containing wastewater according to the present invention, the molar ratio of the complexing agent to the fluoride in the wastewater is Ce:F. - =1:2~10:1, more preferably, Ce:F - =1:2~2:1.

[0014] As a preferred embodiment of the method for removing fluoride from fluoride-containing wastewater according to the present invention, in step S2, the extraction resin is prepared by emulsion suspension polymerization of styrene, divinylbenzene and neutral phosphine extractant, wherein the neutral phosphine extractant is one or a mixture of three of the following in any proportion: trialkylphosphine oxide extractant, trioctylphosphine oxide extractant, and branched-trialkylphosphine oxide extractant.

[0015] As a preferred embodiment of the method for removing fluoride from fluoride-containing wastewater according to the present invention, the volume ratio of the neutral phosphine extractant to the styrene-divinylbenzene mixture is 1%~50%, more preferably 10%~40%; the particle size of the extraction resin is 1μm~5000μm, more preferably 100μm~1000μm.

[0016] In a preferred embodiment of the method for removing fluoride from fluoride-containing wastewater according to the present invention, the column diameter ratio of the adsorption column is 1:0.5 to 1:5, more preferably 1:1 to 1:2.

[0017] As a preferred embodiment of the method for removing fluoride from fluoride-containing wastewater according to the present invention, in step S3, the eluent is one of H2O2, thiourea, and sulfides, the ratio of the amount of eluent added to the amount of Ce in the wastewater is (1~5):1, and the concentration of the eluent is 0.01mol / L~0.5mol / L, more preferably 0.05mol / L~0.2mol / L.

[0018] As a preferred embodiment of the method for removing fluoride from fluoride-containing wastewater according to the present invention, in step S3, the adsorption column after saturation adsorption is eluted with an eluent to obtain an eluent containing CeF3 solid. The eluent is then subjected to solid-liquid separation by vacuum filtration or plate and frame filtration to obtain CeF3 solid and the eluent. The eluent is added to the adsorption column to rinse the CeF3 solid until no solid flows out of the adsorption column.

[0019] The beneficial effects of this invention are as follows:

[0020] This invention utilizes extraction resin for deep defluorination. The resin can be recycled after adsorption and desorption, resulting in a simple process and low reagent consumption. The fluoride complexing agent used is cerium salt, which is inexpensive. The neutral phosphine extraction resin is prepared in one step by emulsion suspension polymerization of commercially available styrene, divinylbenzene, and neutral phosphine extractant. The extractant is not easily detached from the styrene-divinylbenzene copolymer, and the extraction resin can be reused after desorption, reducing the cost of defluorination. The obtained fluoride solid can be sold separately or used as a raw material for cerium or fluorine, achieving comprehensive utilization of cerium and fluorine. Detailed Implementation

[0021] The technical solutions described below in conjunction with the embodiments will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] According to one aspect of the present invention, the present invention provides the following technical solution:

[0023] A method for removing fluoride from fluoride-containing wastewater includes the following steps:

[0024] S1. Adjust the fluoride-containing wastewater to acidity, add a complexing agent to the wastewater, and stir until the complexation is complete;

[0025] S2. The wastewater after stirring in step S1 is passed through an adsorption column containing extraction resin to obtain an adsorption column containing fluorine-complexing agent.

[0026] S3. Elute the saturated adsorption column with eluent to remove solid fluoride.

[0027] Preferably, in step S1, the complexing agent is one or a mixture of two of Ce(SO4)2 and Ce(NO3)4 in any proportion.

[0028] Preferably, in step S1, the molar ratio of the complexing agent added to the fluoride in the wastewater is Ce:F. - =1:2~10:1, more preferably, Ce:F - =1:2~2:1. The fluorinated complexing agent can be added as a solid or in the form of a solution, preferably as a solid to reduce wastewater volume.

[0029] Preferably, in step S2, the extraction resin is prepared by emulsion suspension polymerization of styrene, divinylbenzene and neutral phosphine extractant, wherein the neutral phosphine extractant is one or a mixture of three of the following in any proportion: trialkylphosphine oxide extractant, trioctylphosphine oxide extractant, and branched-trialkylphosphine oxide extractant.

[0030] In one embodiment, the extraction resin can be prepared by dispersion polymerization of a neutral phosphine extractant with styrene monomer and divinylbenzene monomer. For example, the above-mentioned neutral phosphine extractant is mixed with a mixture of styrene monomer and divinylbenzene monomer, and 2% sodium dodecylbenzenesulfonate is added as an initiator to obtain an oil phase; 10 times the volume of deionized water is taken, and 3% gelatin and 0.5% ammonium thiocyanate are added to the aqueous phase to obtain an aqueous phase; the aqueous phase is heated to 50°C, and after the gelatin dissolves, the oil phase is slowly added and kept at this temperature for half an hour, then the temperature is raised to 80°C and the polymerization reaction is carried out for 5 hours; the temperature is then raised to 90°C to cure the resin for half an hour, the resin is removed, washed, sieved, and air-dried to obtain the desired extraction resin.

[0031] Preferably, the ratio of the neutral phosphine extractant to the styrene-divinylbenzene mixture is 1% to 50%, more preferably 10% to 40%; the particle size of the extraction resin is 1 μm to 5000 μm, more preferably 100 μm to 1000 μm.

[0032] Preferably, the column diameter ratio of the adsorption column is 1:0.5 to 1:5, more preferably 1:1 to 1:2.

[0033] Preferably, in step S3, the eluent is one of H2O2, thiourea, and sulfides, the ratio of the amount of eluent added to the amount of Ce in the wastewater is 1~5:1, and the concentration of the eluent is 0.01mol / L~0.5mol / L, more preferably 0.05mol / L~0.2mol / L.

[0034] Preferably, in step S3, the adsorption column after saturation adsorption is eluted with an eluent to obtain an eluent containing CeF3 solid. The eluent is then subjected to solid-liquid separation by vacuum filtration or plate and frame filtration to obtain CeF3 solid and eluent. The eluent is added to the adsorption column to rinse the CeF3 solid until no solid flows out of the adsorption column.

[0035] This invention incorporates a complexing agent to complex with fluoride in wastewater. After complexation, the wastewater is passed through an adsorption column packed with extraction resin for further neutral complexation, achieving deep removal of fluoride from the wastewater. The fluoride content in the treated wastewater can be below 1 mg / L, meeting national drinking water standards. After elution and reduction, the fluoride-loaded extraction resin yields solid fluoride, which can be recovered after further treatment. The fluoride complexing agent used in this invention is inexpensive and recyclable, reducing the cost of fluoride treatment in wastewater to only 1 / 5 of current costs.

[0036] Taking Ce(NO3)4 as a complexing agent, the extraction resin CL-Cyanex923 is used as an example:

[0037] The reaction is as follows:

[0038] Aqueous complexation: Ce(NO3)4+ F- → CeF2(NO3)2+ 2NO3 - (1)

[0039] Solid phase extraction: CeF2(NO3)2+ CL-Cyanex923 (resin) → CeF2(NO3)2·2 CL-Cyanex923 (resin) (2)

[0040] Desorption: CeF2(NO3)2·2 CL-Cyanex923 + H2O2→ CeF3↓+ Ce(III) + CL-Cyanex923+ H2O + O2↑ (3)

[0041] First, the fluoride-containing wastewater is adjusted to acidity. Then, a fluoride complexing agent is added to the wastewater. After stirring to complex the fluoride, the fluoride-complexing wastewater is passed through an adsorption column pre-loaded with extraction resin. The fluoride and complexing agent are adsorbed by the extraction resin, thereby removing fluoride ions from the wastewater. When the fluoride content in the outflowing wastewater is higher than 5 μg / ml, the addition of wastewater is stopped, and the adsorption column is eluted: that is, the fluoride-containing adsorption column after saturation is eluted with an eluent. The fluoride is recovered and reused in the form of solid fluoride. The adsorption column can be recycled after elution.

[0042] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0043] All reagents used in the following examples are commercially available.

[0044] Example 1

[0045] A method for removing fluoride from fluoride-containing wastewater includes the following steps:

[0046] S1. Take 50L of tungsten smelting wastewater with a pH of 7.5. - To adjust the pH of the wastewater to 3.5, add 20 mL of concentrated industrial sulfuric acid (95% sulfuric acid content) to a concentration of 108 mg / L. Then, add 100 g of Ce(SO4)2 ([Ce(IV)]:[F) to the wastewater. - [=1.06:1], stir for 30 minutes;

[0047] S2. Prepare an oil phase by mixing 1L styrene, 0.5L divinylbenzene, 0.5L trialkylphosphine oxide extractant (Cyanex923), and 3g sodium dodecylbenzenesulfonate. Take 5L deionized water, add 150g gelatin and 25g ammonium thiocyanate, heat to 50℃, and after the gelatin is completely dissolved, slowly add the oil phase. Stir for half an hour, then raise the temperature to 80℃ and react for 5 hours. Then raise the temperature to 90℃ and cure for half an hour. Remove the filtered resin, wash with water, and air dry to obtain 1510g CL-Cyanex923 extraction resin.

[0048] Take 500g of CL-Cyanex923 extraction resin and pack it into an adsorption column with a diameter of 75mm. At this point, the resin height is 150mm and the column diameter ratio is 2. Flow the wastewater treated in step S1 through the prepared adsorption column at a flow rate of 100ml / min. Monitor the fluoride content in the effluent. When the fluoride concentration is greater than 5mg / L, stop adding wastewater. At this point, a total of 30.8L of wastewater has been treated.

[0049] S3. Add 3L of 0.1mol / L H2O2 to the adsorption column for elution. Filter the eluent to obtain a white solid. Repeatedly add the filtrate to the adsorption column until the eluent is clear and free of solid. The obtained white solid is CeF3. The purity is 99.02% and it can be sold as industrial CeF3 or used as a raw material for Ce and F. The eluted adsorption column can be reused in step S2 to adsorb fluoride-containing wastewater.

[0050] Example 2

[0051] A method for removing fluoride from fluoride-containing wastewater includes the following steps:

[0052] S1. Take 100L of rare earth smelting wastewater with a pH of 7.5. - To adjust the pH of the wastewater to 4.0, add 50 mL of concentrated industrial nitric acid to a concentration of 98 mg / L. Then, add 320 g of Ce(NO3)4 ([Ce(IV)]:[F) to the wastewater. - [=1.6:1], stir for 30 minutes;

[0053] S2. Prepare an oil phase by mixing 1L of styrene, 0.5L of divinylbenzene, and 1L of branched-trialkylphosphine oxide extractant (Cyanex925). Take 5L of deionized water, add 175g of gelatin and 30g of ammonium thiocyanate, heat to 50℃, and after the gelatin is completely dissolved, slowly add the oil phase. Stir for half an hour, then raise the temperature to 80℃ and react for 5 hours. Then raise the temperature to 90℃ and cure for half an hour. Remove the filtered resin, wash with water, and air dry to obtain 1960g of CL-Cyanex925 extraction resin.

[0054] 1000g of CL-Cyanex925 extraction resin was packed into an adsorption column with a diameter of 75mm, resulting in a resin height of 300mm and a column diameter ratio of 4. The wastewater treated in step S1 was passed through the prepared adsorption column at a flow rate of 200ml / min. The fluoride content in the effluent was monitored. When the fluoride concentration exceeded 5mg / L, the addition of the rare earth smelting wastewater prepared in step 3 was stopped. A total of 61.05L of wastewater was treated.

[0055] S3. Add 6 L of 0.1 mol / L H2O2 to the adsorption column for elution. Filter the eluent to obtain a white solid. Repeatedly add the filtrate to the adsorption column until the eluent is clear and free of solid. The obtained white solid is CeF3. The purity is 98.62%, which can be sold as industrial CeF3 or used as a raw material for Ce and F. The eluted adsorption column can be reused in step S2 to adsorb fluoride-containing wastewater.

[0056] Example 3

[0057] A method for removing fluoride from fluoride-containing wastewater includes the following steps:

[0058] S1. Take 400L of fluoride-containing wastewater with a pH of 7.0. - To adjust the pH of the wastewater to 3.2, add 100 mL of concentrated industrial sulfuric acid to a concentration of 30 mg / L; then add 106 g of Ce(SO4)2 ([Ce(IV)]:[F) to the wastewater. - =1:2), stir for 30 minutes.

[0059] S2. Prepare an oil phase by mixing 1L of styrene, 0.5L of divinylbenzene, and 1L of trioctylphosphine oxide extractant (TOPO). Take 5L of deionized water, add 175g of gelatin and 30g of ammonium thiocyanate, heat to 50℃, and slowly add the oil phase after the gelatin is completely dissolved. Stir for half an hour, then raise the temperature to 80℃ and react for 5 hours. Then raise the temperature to 90℃ and cure for half an hour. Remove the filtered resin, wash with water, and air dry to obtain 1890g of CL-TOPO extraction resin.

[0060] Take 500g of CL-TOPO extraction resin and pack it into an adsorption column with a diameter of 75mm. At this point, the resin height is 150mm and the column diameter ratio is 2. Flow the wastewater treated in step S1 through the adsorption column prepared in step 2 at a flow rate of 200ml / min. Monitor the fluoride content in the effluent. When the fluoride concentration is greater than 5mg / L, stop adding the rare earth smelting wastewater prepared in step 3. At this point, a total of 370L of wastewater has been treated.

[0061] S3. Add 12 L of 0.1 mol / L thiourea to the adsorption column for elution. Filter the eluent to obtain a white solid. Repeatedly add the filtrate to the adsorption column until the eluent is clear and free of solid. The obtained white solid is CeF3. The purity is 98.08%, which can be sold as industrial CeF3 or used as a raw material for Ce and F. The eluted adsorption column can be reused in step S2 to adsorb fluoride-containing wastewater.

Claims

1. A method for removing fluorine from fluorine-containing waste water, characterized by, The method comprises the following steps: S1, adjusting the fluorine-containing wastewater to be acidic, adding a complexing agent to the wastewater, and stirring until the complexing is complete; the complexing agent is a mixture of one or both of Ce(SO4)2 and Ce(NO3)4 in any proportion; S2, flowing the wastewater after the stirring in step S1 through an adsorption column provided with a macroporous adsorption resin to obtain a fluorine-containing complexing agent adsorption column; S3, eluting the saturated adsorption column with an eluent to elute CeF3 solid fluorine.

2. The method for removing fluorine from fluorine-containing wastewater according to claim 1, characterized by, In step S1, the pH of the fluorine-containing wastewater is adjusted to 2-6.

3. The method for removing fluorine from fluorine-containing wastewater according to claim 1, characterized by, The ratio of the amount of the complexing agent added to the amount of substance of fluorine in the wastewater in the step S1 is Ce:F - =1:2~10:

1.

4. The method for removing fluorine from fluorine-containing wastewater according to claim 1, characterized by, In step S2, the macroporous adsorption resin is prepared by emulsion suspension polymerization of styrene, divinylbenzene, and a neutral phosphine extractant, and the neutral phosphine extractant is one of trialkyl phosphine oxide extractant, trioctyl phosphine oxide extractant, and branched trialkyl phosphine oxide extractant, or a mixture of the three in any proportion.

5. The method for removing fluorine from fluorine-containing wastewater according to claim 4, characterized by, The volume ratio of the neutral phosphine extractant to the styrene-divinylbenzene mixture is 1%-50%, and the particle size of the macroporous adsorption resin is 1-5000 μm.

6. The method for removing fluorine from fluorine-containing wastewater according to claim 1, characterized by, The column diameter ratio of the adsorption column is 1:0.5-1:

5.

7. The method for removing fluorine from fluorine-containing wastewater according to claim 1, characterized by, In step S3, the eluent is one of H2O2, thiourea, and sulfide, the ratio of the amount of the eluent to the amount of substance of Ce in the wastewater is (1-5):1, and the concentration of the eluent is 0.01-0.5 mol / L.

8. The method for removing fluorine from fluorine-containing wastewater according to claim 1, characterized by, In step S3, the saturated adsorption column is eluted with an eluent to obtain an eluate containing CeF3 solid, and the eluate is subjected to solid-liquid separation by suction filtration or plate and frame pressure filtration to obtain CeF3 solid and eluate; the eluate is added to the adsorption column to flush the CeF3 solid until no solid flows out of the adsorption column.