CN115259475B - Method for removing fluorine by rare earth-assisted precipitation - Google Patents
Method for removing fluorine by rare earth-assisted precipitation Download PDFInfo
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- CN115259475B CN115259475B CN202211013473.6A CN202211013473A CN115259475B CN 115259475 B CN115259475 B CN 115259475B CN 202211013473 A CN202211013473 A CN 202211013473A CN 115259475 B CN115259475 B CN 115259475B
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- rare earth
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/58—Treatment of water, waste water, or sewage by removing specified dissolved compounds
- C02F1/583—Treatment of water, waste water, or sewage by removing specified dissolved compounds by removing fluoride or fluorine compounds
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/66—Treatment of water, waste water, or sewage by neutralisation; pH adjustment
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/10—Inorganic compounds
- C02F2101/12—Halogens or halogen-containing compounds
- C02F2101/14—Fluorine or fluorine-containing compounds
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
Abstract
The invention discloses a method for removing fluorine by rare earth-assisted precipitation, which comprises the steps of adding soluble rare earth element salt into fluorine-containing ionic liquid, and obtaining a colloid solution after the soluble rare earth element salt is completely dissolved; adding soluble calcium salt and phosphate, and uniformly mixing the solution; regulating the pH value of the mixed solution, stirring and aging; the rare earth ions, calcium ions and phosphate ions in the solution react with fluoride ions together to generate insoluble lanthanum-doped fluorapatite precipitate, after the reaction is finished, the precipitate and the solution can be subjected to solid-liquid separation, and the fluoride ions in the solution are removed. The method has the advantages of simple process, high-efficiency removal effect on the fluoride ions, relatively low cost, wide application range and great industrialization potential.
Description
Technical Field
The invention belongs to the technical field of water treatment, and particularly relates to a method for removing fluorine by rare earth-assisted precipitation, which is used for removing fluorine ions in a water body.
Background
The traditional precipitation defluorination method in industry has the advantages of low cost, simple operation, no need of professional equipment, capability of treating a large amount of fluorine-containing waste liquid and the like. However, the traditional precipitation method has little or no effect on removing low-concentration fluoride ions, and is difficult to reach the national emission standard (namely, the concentration of the fluoride ions in the effluent is less than or equal to 1 mg/L), and the method is often combined with other methods to finish the treatment of the fluoride waste liquid.
Disclosure of Invention
The invention aims to provide a method for removing fluorine by rare earth-assisted precipitation, which can be used for efficiently removing fluorine ions in a water body. Meanwhile, the method is simple to operate, wide in application range, relatively low in cost and quite potential for industrialization.
The technical scheme of the invention is as follows:
a method for removing fluorine by rare earth-assisted precipitation, comprising the following steps:
adding soluble rare earth element salt into the fluorine-containing ionic liquid to dissolve the soluble rare earth element salt completely, so as to obtain a colloid solution;
adding soluble calcium salt and phosphate, and uniformly mixing the solution;
regulating the pH value of the mixed solution, stirring and aging; preferably, the pH adjustment range is 7-10, the stirring time is 1h, and the aging time is 1-12h.
After the reaction is finished, solid-liquid separation can be carried out on the sediment and the solution, and fluoride ions in the liquid are removed.
The rare earth elements are lanthanum, cerium and yttrium, and the preferred rare earth elements are lanthanum.
Further, the ratio of the amounts of the substances of lanthanum element, calcium element in the soluble calcium salt, phosphate in the phosphate and fluorine element in the fluoride ion solution of the soluble rare earth element salt is (La n +Ca m ) p ：(PO 4 ) q : f= (50 to 75): (30-45): 10, wherein n+m=p, the ratio of n to m is (5 to 20): (80-95).
The preferred ratio of the amount of each element dosed to the amount of fluorine element species in the fluoride ion solution is: (la+ca): PO (Positive oxide) 4 : f=75: 45:10, wherein the mass ratio of lanthanum element to calcium element substance is 1:9.
specifically, the soluble rare earth element salt is lanthanum nitrate, the soluble calcium salt is calcium nitrate, and the phosphate is disodium hydrogen phosphate.
According to some preferred embodiments of the invention, the amount of the substance of the soluble lanthanum salt administered in advance is 26 to 157. Mu. Mol.
According to some preferred embodiments of the invention, the amount of the substance of the soluble calcium salt is 421 to 750. Mu. Mol and the amount of the substance of the soluble phosphate salt is 316 to 474. Mu. Mol.
In the scheme, the fluorine removal method can be used for effectively removing various fluorine ions such as sodium fluoride, ammonium fluoride and the like from fluorine-containing substances in different media such as water bodies.
The precipitation defluorination method of the invention is to complex with fluorine ions in solution by adding soluble lanthanum nitrate lanthanum, so as to generate stable colloid solution. Then calcium nitrate and disodium hydrogen phosphate are added, the pH value of the solution is regulated, a colloid system is destroyed, lanthanum ions in the colloid are wrapped by fluorine ions, calcium ions and phosphate ions to generate insoluble lanthanum-doped FAP precipitation, the colloid is destroyed in the process, and fluorine ions in the water body are removed.
The product obtained by the invention has good effect of removing fluoride ion pollutants in liquid, and under the treatment of the optimal process, the fluoride ion concentration of the high-concentration and low-concentration fluoride waste liquid can reach less than or equal to 2mg/L when water is discharged, thereby conforming to the comprehensive discharge standard of sewage (first-order, GB 8978-1996).
The method has the advantages of simple process, relatively low cost, wide application range and large industrialization potential.
Drawings
FIG. 1 is a graph showing the effect of rare earth-assisted precipitation on fluorine removal at different temperatures in example 3 of the present invention.
FIG. 2 is a chart of XRD contrast analysis of by-product precipitation in example 6 of the present invention.
Detailed Description
The present invention will be described in detail with reference to the following examples and drawings, but it should be understood that the examples and drawings are only for illustrative purposes and are not intended to limit the scope of the present invention in any way. All reasonable variations and combinations that are included within the scope of the inventive concept fall within the scope of the present invention.
Example 1
53. Mu. Mol of lanthanum nitrate was added to 100ml of a 10mg/L fluoride ion solution and dissolved therein, and the ratio of the amounts of the substances was (La+Ca): PO (Positive oxide) 4 : f=5: 3:1 (wherein the mass ratio of lanthanum element to calcium element is 1:9), calcium nitrate and disodium hydrogen phosphate are fed, the pH value of the mixed solution is adjusted to 9, the mixed solution is stirred for 1h, supernatant fluid is taken after aging for 1h, the residual fluorine content is measured, and the residual fluorine content is compared with an experiment without adding lanthanum salt under the same condition.
According to the data, the fluorine removal rate in the experiment without adding lanthanum salt is 44.80%, and the fluorine removal rate in the experiment with adding lanthanum salt is improved to 78.90%, namely the fluorine removal rate can be obviously improved by adding lanthanum salt.
Example 2
Adding a certain amount of lanthanum nitrate into 100ml of 10mg/L fluoride ion solution for dissolution, then adding calcium nitrate and disodium hydrogen phosphate according to a certain mass ratio, adjusting the pH of the mixed solution, stirring for 1h, aging for 1h, and taking supernatant to measure the residual fluorine content. Wherein the mass ratio of the substances added by each element is (La n +Ca m ) p ：(PO 4 ) q : f=75: 45:10, wherein n+m=p, the ratio of n to m is 1:9, pH was adjusted to 9.
The removal rate of the fluoride ions under the process can reach 93.34 percent, namely the concentration of the fluoride ions in the effluent is less than or equal to 1mg/L, and the process accords with the comprehensive sewage discharge standard (first grade, GB 8978-1996).
Example 3
Adding lanthanum nitrate into 100ml of 10mg/L fluoride ion solution at different temperature gradients of 5-45 ℃ for dissolution, and then feeding calcium nitrate and disodium hydrogen phosphate according to a certain mass ratio, wherein the mass ratio of each element feeding is (La+Ca): PO (Positive oxide) 4 : f=75: 45:10, adjusting the pH value of the mixed solution to 9, stirring for 1h, aging for 1h, and taking supernatant to measure the residual fluorine content.
The data show that the fluoride ions in the final solution can be effectively removed, namely the optimal process has stable fluoride removal effect in the conventional temperature range. Wherein, the experimental data graph is shown in fig. 1.
Example 4
10mg/L, 20mg/L, 50mg/L, 100mg/L and 200mg/L of fluoride ion solution are respectively prepared, lanthanum nitrate is added into 100ml of fluoride with different concentration gradientsAfter the ionic solution is dissolved, calcium nitrate and disodium hydrogen phosphate are fed according to a certain mass ratio, wherein the mass ratio of the substances fed by each element is (La+Ca): PO (Positive oxide) 4 : f=75: 45:10, adjusting the pH value of the mixed solution to 9, stirring for 1h, aging for 1h, and taking supernatant to measure the residual fluorine content.
The data show that the method has obvious removal effect on fluoride ions with different concentration gradients, wherein the initial concentration is 10mg/L of fluoride solution, and the final fluoride removal rate is 91.05%; fluorine solution with initial concentration of 20mg/L and final fluorine removal rate of 90.49%; fluorine solution with initial concentration of 50mg/L and final fluorine removal rate of 97.74%; fluorine solution with initial concentration of 100mg/L and final fluorine removal rate of 98.98%; the initial concentration of the fluorine solution was 200mg/L, and the final fluorine removal rate was 99.44%. After precipitation and defluorination, the concentration of residual fluoride ions in the solution is less than 2mg/L, which accords with the comprehensive sewage discharge standard (first grade, GB 8978-1996).
Example 5
Adding lanthanum nitrate into 1000ml of 10mg/L fluorine solution for dissolution, and then adding calcium nitrate and disodium hydrogen phosphate according to a certain mass ratio, wherein the mass ratio of each element is (La+Ca): PO (Positive oxide) 4 : f=75: 45:10, adjusting the pH value of the mixed solution to 9, stirring for 1h, aging for 1h, and taking supernatant to measure the residual fluorine content.
The data show that the method can still effectively remove fluorine after expanding the volume of the fluoride ion solution by 10 times, and the final fluoride ion removal rate is 92.85%.
Example 6
A comparative experiment without lanthanum salt was performed under the optimal conditions in example 2, and the obtained by-product precipitate was subjected to XRD analysis and comparison with the precipitate generated under the optimal conditions with lanthanum salt added. The XRD contrast pattern is shown in figure 2. As can be seen from the figure, the main crystal forms of the byproduct precipitate are FAP, and the doping of lanthanum does not affect the main crystal forms of the precipitate, but the peak intensity of the characteristic X-ray diffraction peak is obviously weakened along with the doping of lanthanum.
The above examples are only preferred embodiments of the present invention, and the scope of the present invention is not limited to the above examples. All technical schemes belonging to the concept of the invention belong to the protection scope of the invention. It should be noted that modifications and adaptations to the present invention may occur to one skilled in the art without departing from the principles of the present invention and are intended to be within the scope of the present invention.
Claims (7)
1. The method for removing fluorine by rare earth-assisted precipitation is characterized by comprising the following steps of:
adding soluble rare earth element salt into the fluorine-containing ionic liquid to dissolve the soluble rare earth element salt completely, so as to obtain a colloid solution;
adding soluble calcium salt and phosphate, and uniformly mixing the solution;
regulating the pH value of the mixed solution, stirring and aging; destroying a colloid system, wherein lanthanum ions in the colloid are wrapped with fluorine ions, calcium ions and phosphate ions to generate insoluble lanthanum-doped FAP precipitate;
after the reaction is finished, carrying out solid-liquid separation on the precipitate and the solution, and removing fluorine ions in the solution.
2. The method for removing fluorine by rare earth-assisted precipitation according to claim 1, wherein the rare earth element is lanthanum, cerium or yttrium.
3. The method for removing fluorine by rare earth-assisted precipitation according to claim 1, wherein the rare earth element is lanthanum.
4. A method for removing fluorine by rare earth-assisted precipitation according to claim 3, wherein the ratio of the amounts of lanthanum element of the soluble rare earth salt, calcium element of the soluble calcium salt, phosphate of the phosphate and fluorine element of the fluoride ion solution is (La) n +Ca m ） p ：（PO 4 ） q : f=50 to 75: 30-45: 10, wherein n+m=p, and the ratio of n to m is 5 to 20: 80-95.
5. According to claimThe method for removing fluorine by rare earth-assisted precipitation, which is characterized in that the ratio of the amount of each element to the amount of fluorine element substances in fluorine ion solution is as follows: (la+ca): PO (Positive oxide) 4 : f=75: 45:10, wherein the mass ratio of lanthanum element to calcium element substance is 1:9.
6. the method of claim 1, wherein the soluble rare earth salt is lanthanum nitrate, the soluble calcium salt is calcium nitrate, and the phosphate salt is disodium hydrogen phosphate.
7. The method for removing fluorine by rare earth-assisted precipitation according to claim 1, wherein the pH adjustment range is 7-10, the stirring time period is 1h, and the aging time period is 1-12h.
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