Phosphorus removal agent as well as preparation method and application thereof in sewage treatment

Abstract

The invention discloses a phosphorus removal agent and a preparation method and application thereof in sewage treatment, the phosphorus removal agent comprises a carrier and active components loaded on the carrier, the carrier is modified medical stone, and the active components are FeOCl and La2 (CO3) 3. The phosphorus removal agent can synchronously treat inorganic phosphorus and organic phosphorus in sewage, the needed raw materials are easy to obtain and low in cost, and the prepared adsorption material can be recycled and recycled and is low in secondary pollution.

Description

Technical Field

[0001] The present invention belongs to the technical field of sewage treatment, and particularly relates to a phosphorus removal agent, a preparation method thereof, and an application in sewage treatment. Background Art

[0002] Phosphorus is an important resource widely used in modern agriculture and the chemical industry, and usually exists in aqueous solutions in the forms of organic phosphorus and inorganic phosphates. However, with the development of industry and society, phosphorus enters water bodies through surface runoff or direct drainage, resulting in an increase in the total phosphorus concentration and the eutrophication of water bodies. This causes the overgrowth of aquatic plants, reduces the oxygen content in the water, disrupts the ecological balance, endangers the safety of the ecological environment, and ultimately threatens human health.

[0003] In recent years, various methods have been developed for the removal of phosphorus from sewage, including biological methods, physical adsorption methods, chemical precipitation methods, etc. At present, the advanced treatment of phosphorus-containing wastewater mainly focuses on the removal of inorganic phosphorus, and the commonly used method is chemical precipitation. However, its removal effect on organic phosphorus is not good, resulting in a still high total phosphorus content in the discharged sewage. The existing methods for removing organic phosphorus in wastewater usually involve oxidizing organic phosphorus through advanced oxidation processes to form small molecule inorganic phosphorus and then removing it through chemical precipitation, or removing it through physical adsorption by adsorbents. Although common advanced oxidation processes have good removal effects, their reaction conditions are harsh and the treatment costs are high. While physical adsorption methods have advantages such as simple operation, low cost, and high efficiency, they are difficult to effectively remove highly hydrophobic organic phosphorus, and the utilization of the adsorbed organic phosphorus is also one of the factors restricting the application of adsorption methods.

[0004] In addition, although the degradation methods in the prior art can remove organic phosphorus, after the degradation process, phosphorus exists in the form of inorganic phosphorus. A single degradation method cannot completely remove phosphorus, and still requires a step for removing inorganic phosphorus, resulting in a cumbersome process and high costs. Summary of the Invention

[0005] Aiming at the above problems in the prior art, the present invention provides a phosphorus removal agent, a preparation method thereof, and an application in sewage treatment. This phosphorus removal agent can simultaneously treat inorganic phosphorus and organic phosphorus in sewage, with easily available raw materials, low cost, and the prepared adsorbent material can be recycled, regenerated, and has low secondary pollution.

[0006] To achieve the above object, the present invention adopts the following technical solution: A phosphorus removal agent, comprising: a carrier and an active ingredient supported on the carrier, wherein the carrier is modified zeolite, and the active ingredient is FeOCl and La2(CO3)3.

[0007] Preferably, the modified zeolite is zeolite modified by acid treatment.

[0008] Preferably, the FeOCl and La2(CO3)3 are in-situ synthesized on the carrier.

[0009] The second object of the present invention is to provide a preparation method of the phosphorus remover, comprising the following steps: (1) Adding the modified picrite into the solution of Fe 3+ , stirring and adsorbing, then drying, and calcining at 250-300 °C for 1-2 h to obtain FeOCl supported on the modified picrite; (2) Adding the FeOCl supported on the modified picrite into the solution of La 3+ , uniformly mixing with urea to obtain a precursor solution, and reacting the precursor solution at 80-90 °C for 10-16 h to obtain the phosphorus remover.

[0010] Preferably, in step (1), the solution of Fe 3+ is FeCl3 solution.

[0011] Preferably, in step (1), the mass ratio of the modified picrite to the iron element is 3-4:1.

[0012] Preferably, the drying in step (1) is drying at 80-105 °C.

[0013] Preferably, step (1) further includes a step of washing the FeOCl supported on the modified picrite.

[0014] Preferably, in step (2), the solution of La 3+ is LaCl3 solution.

[0015] Preferably, in step (2), the mass ratio of the FeOCl supported on the modified picrite to the lanthanum element is 3-4:1.

[0016] Preferably, in step (2), the mass ratio of the urea to the FeOCl supported on the modified picrite is 6-8:1.

[0017] Preferably, step (2) further includes steps of washing and drying the reaction product, and the drying temperature is 80-105 °C.

[0018] Preferably, the modified picrite is obtained by the following method: (0) Adding picrite powder into HCl solution for reaction, then washing and drying to obtain it.

[0019] Preferably, the mass fraction of the HCl solution is 5-10%.

[0020] Preferably, the reaction time in step (0) is 1-2 h.

[0021] The third object of the present invention is to provide the application of the phosphorus remover in sewage treatment.

[0022] Preferably, the application further includes using the phosphorus remover simultaneously with persulfate or hydrogen peroxide.

[0023] The beneficial effects of the present invention are as follows: Rare earth metals of the lanthanum (La) series are inherently environmentally friendly and have good biological adaptability, causing relatively little damage to the ecological environment, and still maintaining good adsorption and removal effects on phosphates and water bodies with relatively difficult-to-treat low phosphate concentrations.

[0024] The phosphorus remover of the present invention can be used alone or in combination with persulfate or hydrogen peroxide. When used simultaneously with persulfate or hydrogen peroxide, FeOCl acts as a catalyst to oxidize pollutants not by generating free radicals, but by the surface polymerization coupling effect of the catalyst and the synergistic effect of Fe and Cl connected by an oxygen bridge to directly oxidize pollutants on the surface, thus omitting the intermediate stage of free radical generation and greatly improving the utilization efficiency of the oxidant. It can greatly reduce the usage amounts of persulfate and hydrogen peroxide.

[0025] As a high-quality adsorption material, medical stone is also widely used in adsorption and phosphorus removal, and the Fe2O3 and FeO contained in it can also catalyze hydrogen peroxide and persulfate to generate hydroxyl radicals and sulfate radicals.

[0026] The present invention loads FeOCl and La2(CO3)3 on the surface of medical stone, which can act as an adsorbent and also as a catalyst while being able to adsorb inorganic phosphorus and organic phosphorus in water. In the case of being used together with persulfate or hydrogen peroxide, the loaded FeOCl catalyzes the oxidation of organic phosphorus by hydrogen peroxide or persulfate on the surface, and through the Fe 2+ contained in the medical stone itself to catalyze the generation of hydroxyl radicals and sulfate radicals to oxidize organic phosphorus, and adsorb and remove the generated inorganic phosphate. Description of the Drawings

[0027] Figure 1 It is a comparison chart of the phosphorus removal effects of each group in the adsorption test in Example 1.

[0028] Figure 2 It is a phosphorus removal effect diagram of FeOCl / La2(CO3)3 at different pH values in Example 1.

[0029] Figure 3 It is a comparison chart of the phosphorus removal effects of each group under the condition of a mass ratio of hydrogen peroxide to glyphosate of 2:1 in Example 2.

[0030] Figure 4 It is a comparison chart of the phosphorus removal effects of each group under the condition of a mass ratio of hydrogen peroxide to glyphosate of 5:1 in Example 2.

[0031] Figure 5 They are the phosphorus removal effect diagrams of each group in Example 3 for KH2PO4.

[0032] Figure 6 It is the FTIR diagram of FeOCl / La2(CO3)3 prepared in Example 1. Specific implementation manner Example 1

[0033] 1. Preparation of phosphorus removal agent: (1) Pretreatment of zeolite: The zeolite powder was added to hydrochloric acid with a mass fraction of 5% at a solid-liquid ratio of 1:5 and stirred for reaction for 1 - 2 h. The reaction product was washed with deionized water, filtered, and dried in an oven at 80 °C to obtain zeolite (marked as unloaded).

[0034] (2) Synthesis of FeOCl-loaded composite material: The material treated in (1) was mixed with FeCl3·6H2O at a mass ratio of 3:4, appropriate deionized water was added and stirred for 5 h, filtered, and dried in an oven at 80 °C for 24 h to obtain zeolite loaded with FeCl3 (marked as FeCl3).

[0035] The FeCl3-loaded zeolite was calcined in a muffle furnace at 250 °C for 1 h. After the product was washed several times with deionized water and anhydrous acetone to wash away the unreacted FeCl3·6H2O, it was dried at 80 °C for 6 h. The obtained product was zeolite loaded with FeOCl (marked as FeOCl).

[0036] (3) Synthesis of FeOCl / La2(CO3)3-loaded composite material: The FeOCl-loaded zeolite and LaCl3 were dissolved in deionized water at a mass ratio of 2:1, with a solid-liquid ratio of 1:5. After stirring for 1 - 2 h, a certain amount of urea was added and stirred for another 0.5 - 1 h, with the mass ratio of urea to FeOCl-loaded zeolite being 6:1. The reaction solution was transferred to a hydrothermal reaction kettle and reacted at 80 °C for 12 h. Thereafter, the hydrothermally treated product was centrifuged, the precipitate was washed several times and dried at 80 °C, ground, and passed through an 80-mesh sieve to obtain the phosphorus removal agent (marked as FeOCl / La2(CO3)3).

[0037] (4) Synthesis of La2(CO3)3-loaded composite material: The material treated in (1) was mixed with LaCl3 in deionized water, and the remaining steps were the same as in (3) to obtain zeolite loaded with La2(CO3)3 (marked as La2(CO3)3).

[0038] (5) Synthesis of the FeCl3 / La2(CO3)3 composite supported on the carrier: Mix the FeCl3 supported on the clinoptilolite obtained in (2) with LaCl3 in deionized water. The remaining steps are the same as those in (3) to obtain the FeCl3 / La2(CO3)3 composite supported on the clinoptilolite (denoted as FeCl3 / La2(CO3)3).

[0039] (6) Perform FTIR detection on the obtained materials. As Figure 6 shown, there is a stretching vibration peak of the O-H bond at 3420 cm -1 . This chemical bond comes from the hydroxyl groups in the synthesized material. The stretching vibration peak of the O-C-O bond at 1442 cm -1 is the characteristic vibration of CO3 2- , indicating the formation of CO3 2- in the material. In addition, the stretching vibration peaks of Si=O, Fe-O, and La-O at 1027 cm -1 , 748 cm -1 , and 463 cm -1 show that the main metals contained in the synthesized material are Fe and La, and the non-metal cation is Si.

[0040] 2. Phosphorus removal effect: (1) Adsorption experiment: Select glyphosate (GLY) as the characteristic organic phosphorus pollutant with a concentration of 2 mg / L, a reaction time of 6 h, and a material dosage of 1 g / L. A total of six groups are set up for comparative experiments, namely the unloaded group, FeCl3 group, FeOCl group, La2(CO3)3 group, FeCl3 / La2(CO3)3 group, and FeOCl / La2(CO3)3 group prepared above. The removal rate calculation method is (C - C0)*100 / C0, where C is the GLY concentration after the reaction and C0 is the GLY concentration before the reaction.

[0041] As Figure 1 shown, the FeCl3 / La2(CO3)3 group and the FeOCl / La2(CO3)3 group have better adsorption effects, and the removal rates of glyphosate can reach 75.9% and 77.4% respectively.

[0042] The main reasons are as follows: Lanthanide rare earth metals have good adsorption properties for phosphates. The loading of La 3+ strengthens the adsorption ability of clinoptilolite for GLY.

[0043] The pretreatment with hydrochloric acid unblocks the clogged pores of the clinoptilolite and increases its specific surface area. The modification with Fe 3+ makes the surface of the clinoptilolite carry an obvious positive charge, strengthens the binding ability with negatively charged phosphate ions, and improves the adsorption ability for GLY.

[0044] Fe-loaded 3+ Subsequent calcination further widened the pore size of the zeolite and increased the specific surface area. Therefore, FeOCl-loaded zeolite had a higher GLY removal rate than FeCl3-loaded zeolite.

[0045] (2) GLY adsorption effect of FeOCl / La2(CO3)3-loaded zeolite at different pH values: Glyphosate (GLY) was selected as the characteristic organic phosphorus pollutant with a concentration of 2 mg / L, a reaction duration of 6 h, and a dosage of 1 g / L of the FeOCl / La2(CO3)3 composite. The adsorption effect at pH 3 - 11 was tested. As Figure 2 shown, the material had a strong GLY removal effect when the system pH was between 6 and 8, reaching a maximum of 77.4%. Example 2

[0046] 1. Preparation of phosphorus remover: (1) Pretreatment of zeolite: The zeolite powder was added to 10% hydrochloric acid at a solid-liquid ratio of 1:5 and stirred for 1 - 2 h. The reaction product was washed with deionized water, filtered, and dried in an oven at 80 °C to obtain zeolite (labeled as unloaded).

[0047] (2) Synthesis of FeOCl-loaded composite: The material treated in (1) was mixed with FeCl3·6H2O at a mass ratio of zeolite to iron element of 4:1, and an appropriate amount of deionized water was added and stirred for 5 h. After filtration, it was dried in an oven at 80 °C for 24 h to obtain FeCl3-loaded zeolite.

[0048] The FeCl3-loaded zeolite was calcined in a muffle furnace at 300 °C for 2 h. The product was washed several times with deionized water and anhydrous acetone to remove unreacted FeCl3·6H2O, and then dried at 80 °C for 6 h. The resulting product was FeOCl-loaded zeolite.

[0049] (3) Synthesis of FeOCl / La2(CO3)3 composite: The FeOCl-loaded zeolite and LaCl3 were dissolved in deionized water at a mass ratio of zeolite to lanthanum element of 3:1, with a solid-liquid ratio of 1:5. After stirring for 1 - 2 h, a certain amount of urea was added and stirred for another 0.5 - 1 h, with a mass ratio of urea to FeOCl-loaded zeolite of 6:1. The reaction solution was transferred to a hydrothermal reaction kettle and reacted at 90 °C for 10 h. After that, the hydrothermal product was centrifuged, and the precipitate was washed several times and dried at 105 °C, then ground through an 80-mesh sieve to obtain the phosphorus remover (labeled as FeOCl / La2(CO3)3).

[0050] (4) Synthesis of the FeCl3 / La2(CO3)3 composite supported on the carrier: Mix the FeCl3 supported on the clinoptilolite obtained in (2) with LaCl3 in deionized water. The remaining steps are the same as those in (3) to obtain the FeCl3 / La2(CO3)3 composite supported on the clinoptilolite (labeled as FeCl3 / La2(CO3)3).

[0051] 2. Composite material and H2O2 usage: Select glyphosate (GLY) as the characteristic organic phosphorus pollutant with a concentration of 5 mg / L and mix it with different amounts of H2O2. The dosage of the material is 1 g / L.

[0052] Test the removal rates of GLY when the mass ratio of H2O2 to GLY added is 2:1 and 5:1 respectively. Set up three groups: the unloaded group, the FeCl3 / La2(CO3)3 group, and the FeOCl / La2(CO3)3 supported on the clinoptilolite group.

[0053] From Figure 3 and 4 it can be seen that the FeOCl / La2(CO3)3 supported on the clinoptilolite group has a better GLY removal effect than the other two groups in a shorter time with a lower dosage of H2O2. Here, C is the GLY concentration measured after the reaction, and C0 is the GLY concentration measured before the reaction. When the mass ratio of H2O2 to GLY added is 2:1, the reaction time is 30 min and the removal rate can reach 54.2%. When the mass ratio of H2O2 to GLY added is 5:1, the reaction time is 30 min and the removal rate can reach 79.9%.

[0054] The main reason is that the oxidation of GLY by FeOCl catalyzing H2O2 is through the surface catalysis pathway without going through the generation of ·OH free radical pathway, reducing the consumption of ·OH spontaneous quenching and improving the utilization efficiency of H2O2. While the oxidation of GLY by the clinoptilolite and the clinoptilolite supported with FeCl3 / La2(CO3)3 both go through the free radical pathway with low utilization efficiency. Example 3

[0055] 1. Preparation of the phosphorus remover: (1) Pretreatment of the clinoptilolite: Add the clinoptilolite powder to hydrochloric acid with a mass fraction of 5% at a solid-liquid ratio of 1:5 and stir for 1 - 2 h. The reaction product is washed with deionized water, filtered, and dried in an oven at 80 °C to obtain the clinoptilolite (labeled as unloaded).

[0056] (2) Synthesis of the composite material supported with FeOCl: Mix the material obtained in (1) with FeCl3·6H2O at a mass ratio of clinoptilolite to iron element of 3:1, add an appropriate amount of deionized water and stir for 5 h. After filtration, dry it in an oven at 105 °C for 24 h to obtain the FeCl3 supported on the clinoptilolite (labeled as FeCl3).

[0057] The FeCl3 supported on medical stone was calcined in a muffle furnace at 250 °C for 1 h. After the product was washed several times with deionized water and anhydrous acetone to remove the unreacted FeCl3·6H2O, it was dried at 80 °C for 6 h. The obtained product was the medical stone supported with FeOCl (marked as FeOCl).

[0058] (3)Synthesis of the FeOCl / La2(CO3)3 composite material supported: The medical stone supported with FeOCl and LaCl3 were dissolved in deionized water at a mass ratio of the medical stone to lanthanum element of 3:1, with a solid-liquid ratio of 1:5. After stirring for 1-2 h, a certain amount of urea was added and stirring continued for 0.5-1 h, with the mass ratio of urea to the medical stone supported with FeOCl being 8:1. The reaction solution was transferred to a hydrothermal reactor and reacted at 85 °C for 16 h. Thereafter, the hydrothermally treated product was centrifuged, and the precipitate was washed multiple times and dried at 80 °C, and then ground through an 80-mesh sieve to obtain the phosphorus remover (marked as FeOCl / La2(CO3)3).

[0059] (4)Synthesis of the La2(CO3)3 composite material supported: The material treated in (1) and LaCl3 were mixed in deionized water, and the remaining steps were the same as those in (3) to obtain the medical stone supported with La2(CO3)3 (marked as La2(CO3)3).

[0060] (5)Synthesis of the FeCl3 / La2(CO3)3 composite material supported: The medical stone supported with FeCl3 obtained in (2) and LaCl3 were mixed in deionized water, and the remaining steps were the same as those in (3) to obtain the medical stone supported with FeCl3 / La2(CO3)3 composite material (marked as FeCl3 / La2(CO3)3).

[0061] 2. Adsorption test Potassium dihydrogen phosphate (KH2PO4) was selected as the characteristic inorganic phosphorus pollutant, with a concentration of 2 mg / L, a reaction duration of 6 h, and a material dosage of 1 g / L. A total of six groups were set up for comparative tests, namely the unloaded group, the FeCl3 group, the FeOCl group, the La2(CO3)3 group, the FeCl3 / La2(CO3)3 group, and the medical stone supported with FeOCl / La2(CO3)3 group. The removal rate calculation formula was (C - C0)*100 / C0, where C was the concentration of KH2PO4 after the reaction and C0 was the concentration of KH2PO4 before the reaction.

[0062] From Figure 5It can be seen that after loading La2(CO3)3, the adsorption effect on inorganic phosphorus is significantly improved. After loading FeCl3 / La2(CO3)3 and FeOCl / La2(CO3)3 on the medical stone, the adsorption removal rates reach relatively high levels, which can reach 95.8% and 97.8% respectively. The main reasons are as follows: The pretreatment with hydrochloric acid dredged the blocked pores of the medical stone and increased its specific surface area. Fe 3+ modification made the surface of the medical stone carry obvious positive charges, strengthened the binding ability with negatively charged phosphate ions, and improved the adsorption ability of KH2PO4.

[0063] Lanthanide rare earth metals have good adsorption properties for phosphates and can still maintain good adsorption effects on low-concentration phosphates. La 3+ loading strengthened the adsorption ability of the medical stone for orthophosphate.

[0064] Loading Fe 3+ followed by further calcination widened the pore diameter of the medical stone and increased the specific surface area. Therefore, the removal rate of KH2PO4 is higher for FeOCl loading than for FeCl3 loading.

Claims

1. A phosphorus removal agent, characterized in that, Comprising: A carrier and an active ingredient carried by the carrier, the carrier being modified picrite, and the active ingredient being FeOCl and La2(CO3)3.

2. The phosphorus remover according to claim 1, characterized in that, The modified picrite is picrite modified by acid treatment.

3. The preparation method of the phosphorus remover according to any one of claims 1-2, characterized in that, Including the following steps: (1) Add the modified picrite into the solution of Fe 3+ , stir and adsorb, then dry, and calcine at 250~300°C for 1~2 h to obtain FeOCl supported on the modified picrite; (2) Add the FeOCl supported on the modified picrolite into the solution of La 3+ and uniformly mix it with urea to obtain a precursor solution. React the precursor solution at 80 - 90 °C for 10 - 16 h to obtain the phosphorus removal agent.

4. The preparation method according to claim 3, characterized in that, In step (1), the mass ratio of the modified picrite to the iron element is 3 - 4:

1.

5. The preparation method according to claim 3, characterized in that, In step (2), the mass ratio of the FeOCl carried by the modified picrite to the lanthanum element is 3 - 4:

1.

6. The preparation method according to claim 3, characterized in that, In step (2), the mass ratio of the urea to the FeOCl carried by the modified picrite is 6 - 8:

1.

7. The preparation method according to claim 3, characterized in that, The modified picrite is obtained by the following method: (0) Put picrite powder into an HCl solution for reaction, then wash and dry to obtain it.

8. The preparation method according to claim 7, characterized in that, The mass fraction of the HCl solution is 5 - 10%.

9. Application of the phosphorus remover according to any one of claims 1 - 2 in sewage treatment.

10. The application according to claim 9, wherein The application further includes using the phosphorus remover simultaneously with persulfate or hydrogen peroxide.

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