Fly ash / metal oxide composite material and method for recovering phosphorus and fluorine in phosphogypsum leaching wastewater by using fly ash / metal oxide composite material

Abstract

The invention discloses a fly ash / metal oxide composite material preparation method, which comprises: 1) adding a silicon source, an aluminum source and fly ash into an alkali liquid, carrying out heating stirring treatment, adding a template agent, and carrying out a thermal insulation reaction to obtain a mixed liquid I; 2) adding a metal salt solution into the mixed solution I, and continuously stirring to obtain a mixed solution II; (3) heating and crystallizing the mixed solution II, carrying out centrifugal separation, collecting solid substances, cleaning and drying for later use; and 4) calcining the obtained solid substance to obtain the fly ash / metal oxide composite material. The adsorbent can remove and recover phosphorus and fluorine in phosphogypsum leaching wastewater, is high in adsorption capacity, high in adsorption rate and high in anti-interference capability, and can be used for treating actual wastewater containing phosphorus and fluorine; and the related preparation method is relatively simple, relatively low in cost and suitable for popularization and application.

Description

Technical Field

[0001] The invention belongs to the technical field of wastewater treatment, and in particular relates to a fly ash / metal oxide composite material and a method for recovering phosphorus and fluorine in phosphogypsum leaching wastewater by using the fly ash / metal oxide composite material. Background Art

[0002] With the rapid development of economy and chemical industry, the problem of phosphorus and fluoride pollution in water has become increasingly serious. Wastewater containing phosphorus and fluoride mainly comes from industrial production processes such as mining, chemical industry and semiconductor, and the phosphorus and fluoride content in wastewater ranges from tens to tens of thousands of mg / L. Wastewater containing phosphorus and fluoride is mainly treated by precipitation, adsorption, membrane separation and other methods. Among them, adsorption method is widely used in actual wastewater treatment due to its advantages of simple operation, low cost and good removal effect.

[0003] As a byproduct of coal combustion, fly ash accounts for 60-88% of the total solid waste of coal-fired power plants; if not handled properly, it may cause water and soil pollution and endanger human health. Fly ash contains a large amount of valuable elements such as silicon, aluminum, and iron. The rational and efficient use of fly ash is crucial to the sustainable development of the industry. Using fly ash as a raw material and modifying it to prepare a composite high-efficiency adsorbent can achieve the dual goals of resource recycling and environmental protection. At present, there have been some reports on fly ash-based adsorption materials, but they mainly modify or consolidate fly ash to form lightweight porous materials, and the adsorption effect involved is limited; especially for wastewater systems with many impurities and strong interference, such as phosphogypsum leaching wastewater, it is impossible to achieve efficient adsorption and removal of phosphorus and fluorine. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing an adsorbent with abundant and readily available raw materials, economy and simple operation. The adsorbent can remove and recover phosphorus and fluorine in phosphogypsum leaching wastewater, and has high adsorption capacity, fast adsorption rate and strong anti-interference ability, and can be used for the treatment of actual phosphorus- and fluorine-containing wastewater.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] A method for preparing a fly ash / metal oxide composite material comprises the following steps:

[0007] 1) adding a silicon source, an aluminum source and fly ash into an alkali solution, heating and stirring the solution, adding a template, and performing a heat-insulating reaction to obtain a mixed solution I;

[0008] 2) adding a metal salt solution to the mixed solution I, and continuously stirring to obtain a mixed solution II;

[0009] 3) heating the mixed solution II for crystallization, centrifuging and collecting the solid matter, washing and drying it for later use;

[0010] 4) calcining the obtained solid material to obtain a fly ash / metal oxide composite material.

[0011] In the above scheme, the silicon source in step 1) can be selected from at least one of silicon dioxide, sodium silicate, tetraethyl orthosilicate, fumed silica, aluminosilicate minerals, etc.; the aluminum source can be selected from at least one of aluminum hydroxide, aluminate, aluminum nitrate, aluminum sulfate, aluminum oxide, etc.

[0012] In the above scheme, the SiO2 content in the fly ash is 15-55wt%, and the Al2O3 content is 5-40wt%.

[0013] In the above scheme, in the mixed system obtained from silicon source, aluminum source and fly ash, the molar ratio of SiO2 / Al2O3 is 1-150.

[0014] In the above scheme, the total mass of the silicon source, aluminum source, and fly ash in step 1) and the solid-liquid ratio (g / mL) of the alkali solution is 1:(3-9), and the concentration of the alkali solution is 4-16wt%.

[0015] In the above scheme, the alkali solution in step 1) is an aqueous solution of NaOH, KOH, Na2CO3 or K2CO3; its concentration is 1-8 mol / L.

[0016] In the above scheme, the insulation reaction temperature in step 1) is 90-150° C., and the reaction time is 12-48 hours.

[0017] In the above scheme, the template agent in step 1) is at least one of hexadecyltrimethylammonium chloride, sodium dodecyl sulfate, tetrapropylammonium hydroxide, n-propylamine, n-butylamine, isobutylamine, etc.; and its mass ratio to fly ash is 0.001-0.1.

[0018] In the above scheme, in step 2), the metal salt solution is added to the mixed solution I at a flow rate of 3-15 mL / min.

[0019] In the above scheme, the metal salt in the metal salt solution is two or more of soluble aluminum, iron, manganese, zinc, calcium, cerium, lanthanum, zirconium, magnesium salts and the like.

[0020] Furthermore, the metal ion concentration in the metal salt solution is 0.1-3 mol / L.

[0021] In the above scheme, in step 2), the volume ratio of the metal salt solution to the alkali solution is (0.25-3):1.

[0022] In the above scheme, the stirring treatment time in step 2) is 2-10 hours.

[0023] In the above scheme, the temperature used for the heating crystallization in step 3) is 30-80° C., and the crystallization time is 4-24 hours.

[0024] In the above scheme, the calcination temperature in step 4) is 150-900° C. and the calcination time is 1-8 hours.

[0025] The fly ash / metal oxide composite material prepared according to the above scheme has a specific surface area of ​​50-1000m 2 / g.

[0026] The present invention also provides a method for recovering phosphorus and fluorine in phosphogypsum leaching wastewater using the above-mentioned fly ash / metal oxide composite material, comprising the following steps: adding fly ash / metal oxide composite material to the phosphogypsum leaching wastewater, performing a shaking treatment, and standing to achieve effective adsorption of phosphorus and fluorine components in the phosphogypsum leaching wastewater.

[0027] Furthermore, the fly ash / metal oxide composite material is added in an amount of 1-40 g:1 L to the phosphogypsum leaching wastewater.

[0028] In the above scheme, the P content in the phosphogypsum leaching wastewater is 50-1500 mg / L, the fluorine content is 10-1000 mg / L, the sulfate content is 1000-10000 mg / L, the calcium ion content is 100-1000 mg / L; and the pH is 1.0-3.0.

[0029] Furthermore, the shaking treatment is carried out at a rate of 80-250 r / min and a time of 0.5-5 h.

[0030] Furthermore, the standing time is 5-30 minutes.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. The fly ash / metal oxide composite material prepared by the present invention has the advantages of high specific surface area, large metal oxide loading, stable performance, high adsorption capacity for phosphorus and fluorine, and strong anti-interference ability;

[0033] 2. The present invention uses fly ash as the main raw material, which not only reduces the production cost, but also realizes the resource utilization of solid waste, and provides a new way for the high-value utilization of fly ash. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0035] In the following examples, the fly ash used was provided by a power plant in Shandong, wherein the SiO2 content was 48.12wt% and the Al2O3 content was 36.75wt%.

[0036] Example 1

[0037] A method for recovering phosphorus and fluorine in phosphogypsum leaching wastewater comprises the following steps:

[0038] 1) Weigh 5 g of silicon dioxide, 10 g of sodium aluminate, 75 g of fly ash, and 0.5 g of tetrapropylammonium hydroxide, add them into 450 mL of NaOH (2 mol / L) solution, and stir and react at 95° C. for 24 h to obtain a mixed solution I; wherein the SiO2 / Al2O3 molar ratio of the mixed system obtained by the silicon source, the aluminum source, and the fly ash is 2.1;

[0039] 2) adding 450 mL of AlCl3 / CaCl2·2H2O mixed solution to the mixed solution I at a flow rate of 10 mL / min through a peristaltic pump, wherein the concentration of AlCl3 is 0.3 mol / L and the concentration of CaCl2·2H2O is 0.5 mol / L, and stirring is continued for 4 h to obtain a mixed solution II;

[0040] 3) After the mixed solution II was placed at 45°C for crystallization for 4 hours, it was centrifuged to collect the solid matter, washed and dried, and then placed in a muffle furnace for calcination at 500°C for 1 hour to obtain a fly ash / metal oxide composite material (specific surface area of ​​157 m 2 / g).

[0041] The material obtained in this example is used to remove and recover phosphorus and fluorine in phosphogypsum leaching wastewater, and the specific steps include: adding 0.05g of fly ash / metal oxide composite material to 50mL of leaching wastewater with a phosphorus concentration of 25mg / L, a fluorine concentration of 50mg / L, a sulfate radical of 1200mg / L, and a pH of 1.5, shaking the reaction in a shaker at 250r / min for 2h, standing for 0.5h, and taking the supernatant to detect the phosphorus and fluorine concentrations; the results show that the phosphorus removal rate is 96.5%, and the fluorine removal rate is 97.9%.

[0042] Example 2

[0043] A method for recovering phosphorus and fluorine in phosphogypsum leaching wastewater comprises the following steps:

[0044] 1) Weigh 5 g of silicon dioxide, 10 g of sodium aluminate, 75 g of fly ash, and 0.85 g of n-propylamine, add them into 450 mL of NaOH (2 mol / L) solution, and stir and react at 105° C. for 24 h to obtain a mixed solution I; wherein the SiO2 / Al2O3 molar ratio of the mixed system obtained by the silicon source, the aluminum source, and the fly ash is 2.1;

[0045] 2) adding 450 mL of AlCl3 / LaCl3 mixed solution to the mixed solution I at a flow rate of 10 mL / min by a peristaltic pump, wherein the concentration of AlCl3 is 0.5 mol / L and the concentration of LaCl3 is 0.5 mol / L, and stirring is continued for 4 h to obtain a mixed solution II;

[0046] 3) After the mixed solution II was placed at 60°C for crystallization for 4 hours, it was centrifuged to collect the solid matter, washed and dried, and then placed in a muffle furnace for calcination at 500°C for 1 hour to obtain a fly ash / metal oxide composite material (specific surface area of ​​171m 2 / g).

[0047] The material obtained in this example is used to remove and recover phosphorus and fluorine in phosphogypsum leaching wastewater, and the specific steps include: adding 0.1 g of the material to 50 mL of leaching wastewater with a phosphorus concentration of 50 mg / L, a fluorine concentration of 70 mg / L, a sulfate concentration of 1500 mg / L, and a pH of 2.1, shaking the reaction in a shaker at 250 r / min for 2 hours, standing for 0.5 hours, and taking the supernatant to detect the phosphorus and fluorine concentrations; the results showed that the phosphorus removal rate reached 97.1%, and the fluorine removal rate reached 98.5%.

[0048] Example 3

[0049] A method for recovering phosphorus and fluorine in phosphogypsum leaching wastewater comprises the following steps:

[0050] 1) Weigh 5 g of silicon dioxide, 2.5 g of aluminum oxide, 75 g of fly ash, and 0.85 g of n-propylamine, add them into 450 mL of NaOH (2 mol / L) solution, and stir and react at 95° C. for 24 h to obtain a mixed solution I; wherein the SiO2 / Al2O3 molar ratio of the mixed system of silicon source, aluminum source, and fly ash is 2.36;

[0051] 2) adding 450 mL of FeCl3 / LaCl3 mixed solution to the mixed solution I at a flow rate of 10 mL / min by a peristaltic pump, wherein the concentration of FeCl3 is 0.3 mol / L and the concentration of LaCl3 is 0.5 mol / L, and stirring is continued for 4 h to obtain a mixed solution II;

[0052] 3) The mixed solution II was placed at 45°C for crystallization for 4 hours, and then centrifuged to collect the solid matter, which was washed and dried and then calcined in a muffle furnace at 500°C for 1 hour to obtain a fly ash / metal oxide composite material (with a specific surface area of ​​183 m 2 / g).

[0053] The material obtained in this example is used to remove and recover phosphorus and fluorine in phosphogypsum leaching wastewater, and the specific steps include: adding 0.25g of the material to 50mL of leaching wastewater with a phosphorus concentration of 105mg / L, a fluorine concentration of 50mg / L, a sulfate concentration of 1400mg / L, and a pH of 1.7, shaking the reaction in a shaker at 250r / min for 2h, standing for 0.5h, and taking the supernatant to detect the phosphorus and fluorine concentrations; the results showed that the phosphorus removal rate reached 98.1%, and the fluorine removal rate reached 98.9%.

[0054] Comparative Example 1

[0055] A method for recovering phosphorus and fluorine in phosphogypsum leaching wastewater comprises the following steps:

[0056] 1) Weigh 5 g of silicon dioxide, 10 g of sodium aluminate, and 75 g of fly ash, add them into 450 mL of NaOH (2 mol / L) solution, and stir and react at 105° C. for 24 h to obtain a mixed solution I; wherein the SiO2 / Al2O3 molar ratio of the mixed system of silicon source, aluminum source, and fly ash is 2.1;

[0057] 2) adding 450 mL of FeCl3 solution with a concentration of 0.6 mol / L to the mixed solution I through a peristaltic pump at a flow rate of 10 mL / min, and continuously stirring for 4 h to obtain a mixed solution II;

[0058] 3) Place the mixed solution II at 60°C for crystallization for 4 hours, centrifuge and collect the solid matter, wash and dry to obtain a fly ash / metal oxide composite material (specific surface area of ​​107m 2 / g).

[0059] The material obtained in this comparative example is used to remove and recover phosphorus and fluorine in phosphogypsum leaching wastewater. The specific steps include: adding 0.1g of material to 50mL of leaching wastewater with a phosphorus concentration of 50mg / L, a fluorine concentration of 70mg / L, a sulfate concentration of 1500mg / L, and a pH of 1.5, shaking the reaction in a shaker at 250r / min for 2h, standing for 0.5h, and taking the supernatant to detect the phosphorus and fluorine concentrations; the results showed that the phosphorus removal rate was 60.1%, and the fluorine removal rate was 37.2%.

[0060] Comparative Example 2

[0061] A method for recovering phosphorus and fluorine in phosphogypsum leaching wastewater comprises the following steps:

[0062] 1) Weigh 5 g of silicon dioxide, 10 g of sodium aluminate, 20 g of fly ash, and 0.5 g of hexadecyltrimethylammonium chloride, add them into 450 mL of NaOH (2 mol / L) solution, and stir and react at 105° C. for 24 h to obtain a mixed solution I; wherein the SiO2 / Al2O3 molar ratio of the mixed system obtained by the silicon source, the aluminum source, and the fly ash is 1.85;

[0063] 2) adding 450 mL of AlCl3 solution with a concentration of 0.5 mol / L to the mixed solution I at a flow rate of 10 mL / min through a peristaltic pump, and stirring for 4 h to obtain a mixed solution II;

[0064] 3) Place the mixed solution II at 60°C for crystallization for 4 hours, centrifuge and collect the solid matter, wash and dry to obtain a fly ash / metal oxide composite material (specific surface area of ​​122 m 2 / g).

[0065] The material obtained in this comparative example is used to remove and recover phosphorus and fluorine in phosphogypsum leaching wastewater. The specific steps include: adding 0.1g of material to 50mL of leaching wastewater with a phosphorus concentration of 50mg / L, a fluorine concentration of 70mg / L, a sulfate concentration of 1000mg / L, and a pH of 1.5, shaking the reaction in a shaker at 250r / min for 2h, standing for 0.5h, and taking the supernatant to detect the phosphorus and fluorine concentrations; the results showed that the phosphorus removal rate was 64.5%, and the fluorine removal rate was 50.1%.

[0066] Comparative Example 3

[0067] A method for recovering phosphorus and fluorine in phosphogypsum leaching wastewater comprises the following steps:

[0068] 1) Weigh 5 g of silicon dioxide, 10 g of sodium aluminate, and 20 g of fly ash, add them into 450 mL of NaOH (2 mol / L) solution, and stir and react at 105° C. for 24 h to obtain a mixed solution I; wherein the SiO2 / Al2O3 molar ratio of the mixed system of silicon source, aluminum source, and fly ash is 1.85;

[0069] 2) adding 450 mL of FeCl3 / AlCl3 mixed solution to the mixed solution I at a flow rate of 10 mL / min through a peristaltic pump, wherein the concentration of FeCl3 is 0.4 mol / L and the concentration of AlCl3 is 0.1 mol / L, and stirring is continued for 4 h to obtain a mixed solution II;

[0070] 3) Place the mixed solution II at 60°C for crystallization for 4 hours, centrifuge and collect the solid matter, wash and dry to obtain a fly ash / metal oxide composite material (specific surface area of ​​105m 2 / g).

[0071] The material obtained in this comparative example is used to remove and recover phosphorus and fluorine in phosphogypsum leaching wastewater. The specific steps include: adding 0.1 g of material to 50 mL of leaching wastewater with a phosphorus concentration of 60 mg / L, a fluorine concentration of 75 mg / L, a sulfate concentration of 1000 mg / L, and a pH of 1.5, shaking the reaction in a shaker at 250 r / min for 2 hours, standing for 0.5 hours, and taking the supernatant to detect the phosphorus and fluorine concentrations; the results showed that the phosphorus removal rate was 64.2%, and the fluorine removal rate was 63%.

[0072] The present invention is not limited to the above-mentioned embodiments. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention. The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in this field.

Claims

1. A method for preparing a fly ash / metal oxide composite material, characterized in that: The steps include: 1) adding a silicon source, an aluminum source and fly ash into an alkali solution, heating and stirring the solution, adding a template, and performing a heat-insulating reaction to obtain a mixed solution I; 2) adding a metal salt solution to the mixed solution I, and continuously stirring to obtain a mixed solution II; 3) heating the mixed solution II for crystallization, centrifuging and collecting the solid matter, washing and drying it for later use; 4) calcining the obtained solid material to obtain a fly ash / metal oxide composite material.

2. The preparation method according to claim 1, characterized in that: In the mixed system obtained from silicon source, aluminum source and fly ash, the molar ratio of SiO2 / Al2O3 is 1-150.

3. The preparation method according to claim 1, characterized in that: The insulation reaction temperature of step 1) is 90-150° C., and the reaction time is 12-48 hours.

4. The preparation method according to claim 1, characterized in that: Step 1) The template agent is at least one of hexadecyltrimethylammonium chloride, sodium dodecyl sulfate, tetrapropylammonium hydroxide, n-propylamine, n-butylamine, and isobutylamine; and the mass ratio of the template agent to the fly ash is 0.001-0.

1.

5. The preparation method according to claim 1, characterized in that: The metal salt in the metal salt solution is two or more of soluble aluminum, iron, manganese, zinc, calcium, cerium, lanthanum, zirconium and magnesium salts.

6. The preparation method according to claim 1, characterized in that: Step 2) The stirring treatment time is 2-10 hours.

7. The preparation method according to claim 1, characterized in that: The temperature used for the heating crystallization in step 3) is 30-80° C. and the crystallization time is 4-24 hours.

8. The preparation method according to claim 1, characterized in that: Step 4) The calcination temperature is 150-900°C and the calcination time is 1-8h.

9. The fly ash / metal oxide composite material prepared by the preparation method according to any one of claims 1 to 8, characterized in that: Its specific surface area is 50-1000m 2 / g.

10. Use of the fly ash / metal oxide composite material according to claim 9 in phosphogypsum leaching wastewater.