Method for efficiently removing phosphorus from phosphorus tailing leaching wastewater

Abstract

The invention relates to a method for efficiently removing phosphorus from phosphorus tailing leaching wastewater, which comprises the following steps: adding calcium salt into the phosphorus tailing leaching wastewater, stirring for 5-10 minutes, fully reacting, and filtering to remove precipitate; then montmorillonite is added to adsorb pollutants, stirring is conducted for 5-10 min, full reaction is conducted, finally, the pH of a water sample is adjusted through a coagulant, standing and precipitation are conducted, total phosphorus is further reduced, meanwhile, other pollutants reach the standard and are discharged, and removal of the total phosphorus in the phosphorus tailing wastewater is completed. The dephosphorization agent used in the method is small in dosage and low in cost; the treatment process is simple and the action efficiency is high; meanwhile, the treatment effect on the high-phosphorus wastewater is good, no other pollutants are introduced, and the method is environment-friendly. After the stage treatment by the method, the total phosphorus in the phosphorus tailing leaching wastewater is rapidly reduced, and the wastewater discharge standard is reached.

Description

Technical Field

[0001] The invention belongs to the technical field of wastewater purification and treatment, and particularly relates to a method for efficiently removing phosphorus from phosphorus tailings leaching wastewater. Background Art

[0002] Large-scale storage of phosphate tailings will harm the surrounding ecological environment. When the phosphate tailings are washed or soaked by rainwater, the residual chemicals in the phosphate tailings will be released into the water body, and then flow into nearby waters and groundwater, causing damage to the ecological environment. The indicators with higher concentrations of pollutants in phosphate tailings include total phosphorus, COD and sulfate, among which total phosphorus seriously exceeds the standard and does not meet the emission standards.

[0003] There are chemical and biological methods for removing phosphorus from high-phosphorus wastewater. Biological phosphorus removal is affected by factors such as influent conditions and operating conditions. It is difficult for the effluent quality to meet the standards if it relies solely on biological phosphorus removal. Chemical phosphorus removal includes chemical precipitation, adsorption, ion exchange, etc. Ion exchange is difficult to use due to its high processing cost. Patent CN 109704446B discloses a phosphorus removal agent prepared by mixing cement and bentonite to treat eutrophic water bodies. The total phosphorus can be reduced to 0.118-0.145 mg / L, with good treatment effect and long action time, and the treated water sample is low-concentration phosphorus (1.4 mg / L). Patent CN 115028245A discloses a method for preparing a composite phosphorus removal material by mixing calcium copper and biochar, which has the advantages of good stability, low price and high efficiency. However, for 75 mg / L inorganic high-phosphorus wastewater, when the composite material dosage is 0.5 g / L, the inorganic phosphorus removal rate is 73%, and the treatment efficiency is not high.

[0004] In addition to the above patents, the current treatment of phosphorus-containing wastewater by phosphorus removal agents still has the following problems: 1. The preparation process of phosphorus removal agent is complicated, the process is cumbersome and many facilities are required.

[0005] 2. The dosage of chemicals is large, the economic cost is high, and it is not environmentally friendly.

[0006] 3. The drug reaction time is long and the effect is poor.

[0007] 4. Most phosphorus removal agents can only treat wastewater with low phosphorus content, with a concentration below 10 mg / L; however, the treatment effect on high-phosphorus wastewater (>50 mg / L) is poor and cannot directly meet the wastewater discharge standard (TP<0.5 mg / L).

[0008] Chemical precipitation has many advantages such as short purification cycle, stable phosphorus removal effect and strong pertinence, and is widely used. At present, the commonly used chemical phosphorus removal agents on the market include calcium salts, aluminum salts and iron salts. Calcium salts have significant phosphorus removal effects as precipitants, but after excessive addition, the total hardness of the water increases and the pH will increase significantly, requiring additional pH adjustment, which affects the effluent quality; aluminum salts and iron salts have coagulation effects, but the aqueous solution after treatment is acidic, and the phosphorus removal effect is general, usually playing an auxiliary role. The adsorption method is suitable for treating low-concentration phosphorus-containing wastewater and has a good effect. Summary of the invention

[0009] In order to solve the above problems, the present invention aims to provide a method for efficient phosphorus removal from phosphate tailings leaching wastewater, a method for treating the leaching wastewater in steps by using a phosphorus removal agent to reduce the total phosphorus in the water body, and a method for jointly treating high-phosphorus wastewater with calcium salt, montmorillonite and a coagulant to reduce COD and sulfate at the same time without adjusting the pH of the water sample, thereby ensuring that the wastewater meets the first-level standard of the "Comprehensive Sewage Discharge Standard" (GB8978-1996) and the Class III standard in the "Groundwater Quality Standard" GB / T 14848-2017, and does not cause secondary pollution to the water body.

[0010] The technical solution of the present invention is as follows: In order to solve the above technical problems, the present invention provides the following technical solutions: A method for efficiently removing phosphorus from phosphate tailings leaching wastewater, the method comprising the following steps: (1) Add calcium salt to the wastewater from phosphate tailings leaching, stir evenly, let it stand and settle, then filter the precipitate; (2) adding montmorillonite to the filtrate obtained in step (1) and stirring evenly; (3) adding a flocculant to the solution obtained in step (2), stirring evenly, and allowing to stand for precipitation; (4) taking the supernatant obtained in step (3) and filtering; Complete the removal of total phosphorus in the leaching water of phosphate tailings.

[0011] Preferably, the pH of the phosphate tailings leaching wastewater in step (1) is 6.5-7.8, the total phosphorus concentration is 80-120 mg / L, the COD concentration is 80-100 mg / L, and the sulfate concentration is 400-500 mg / L. Preferably, the calcium salt in step (1) is one or more of CaO and Ca(OH)2, with an amount of 100-300 mg / L; Step (1) The stirring speed is 500-800 r / min, the stirring time is 5-10 min, and then filtering is performed with filter paper.

[0012] Preferably, in step (2), the dosage of montmorillonite agent is 50-150 mg / L, and the stirring time is 5-10 min. Preferably, the montmorillonite is modified before being added, and the modification method is modification with lanthanum chloride.

[0013] Further preferably, the preparation method of modified montmorillonite comprises the following steps: 1) Add lanthanum chloride and PTCDA (3,4,9,10-perylenetetracarboxylic dianhydride) to the montmorillonite suspension, stir evenly to obtain a mixed solution, the particle size of the montmorillonite is 1-10 microns, the mass concentration of the montmorillonite suspension is 0.1wt%-5wt%, the mass concentration of lanthanum chloride in the mixed solution is in the range of 1wt%-20wt%, and the mass concentration of PTCDA is in the range of 5-12 wt%; 2) Filter the solution in step 1), dry it, grind it, and then add montmorillonite, the particle size of which is 1-10 nanometers, to obtain modified montmorillonite. Preferably, the flocculant in step (3) is one or more of polyaluminium chloride, polyferric sulfate and alum, and the dosage is 80-1000 mg / L; In step (3), the stirring speed is 300-500 r / min, the stirring time is 3-5 min, and the standing time is 5 min.

[0014] Preferably, the step (4) is filtered using a 0.4-0.5 μm filter, preferably 0.45 μm.

[0015] Compared with the prior art, the present invention has the following beneficial effects: (1) Low price: The calcium salt precipitant, montmorillonite and coagulant added to the phosphate tailings leaching wastewater in the present invention are all common chemical agents, which are cheap and used in small amounts, making the phosphorus removal cost extremely low.

[0016] (2) The process is simple. The wastewater treatment method of the present invention does not require the addition of acid or alkali to adjust the pH of the effluent. The stirring reaction time is only 5-10 minutes, the treatment time is short, and the efficiency is high.

[0017] (3) High phosphorus removal efficiency. By adding a precipitant to high-phosphorus wastewater, the total phosphorus concentration can be rapidly reduced. By adding modified montmorillonite and coagulant, the total phosphorus concentration can be further reduced to the discharge standard. At the same time, the pH of the wastewater can be adjusted, and other pollutants in the wastewater can be further reduced by coagulation. After step-by-step treatment, the pH, total phosphorus, sulfate, COD, total hardness and iron ions of the wastewater all meet the discharge standards.

[0018] The treatment method of the present invention can effectively solve the problem of high-phosphorus wastewater, and has simple process, high phosphorus removal efficiency and low price. DETAILED DESCRIPTION

[0019] The following will be combined with the specific embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. The embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the protection scope of the present invention.

[0020] In the context of this specification, except for the contents explicitly described, any matters or items not mentioned directly use the technology known in the art. Moreover, any embodiment described in this patent can be freely combined with one or more other embodiments described in this patent, and the technical solutions or technical ideas formed thereby are regarded as part of the original disclosure or original record of the present invention, and should not be regarded as new content not disclosed in this patent, unless a person skilled in the art considers that the combination is obviously unreasonable.

[0021] The data points disclosed in the present invention include not only the specifically disclosed numerical points, but also the endpoints of each numerical range. Any combination of these data points should be regarded as the disclosed or recorded range of the present invention, regardless of whether these numerical points are disclosed one by one in this article. raw material Phosphate tailings were selected from a phosphate tailings filter press workshop in Yichang; the pH of the phosphate tailings leaching wastewater was 7.1, and the total phosphorus was 88 mg / L; calcium oxide, calcium hydroxide, polyaluminium chloride, polyferric sulfate and alum were all analytical grade used in the laboratory. Examples 1-3 Take 300 ml of phosphate tailings leaching wastewater and place it in a 500 ml beaker. Add 30 mg, 60 mg and 90 mg of CaO respectively. Stir at 800 rpm / min for 5 min. Let stand for 5 min. Take the supernatant, filter with a 0.45 μm filter head, and determine the pH and total phosphorus.

[0022] Example 4 Take 300 ml of the extract and place it in a 500 ml beaker, add 90 mg of Ca(OH)2, stir at 600 rpm / min, stir for 7 min, let stand for 5 min, take the supernatant, filter with a 0.45 μm filter, and determine the pH and total phosphorus.

[0023] Table 1 Results of leachate treatment with different calcium salts

[0024] Table 1 shows the pH and total phosphorus measured in the water samples of Examples 1-4. As the amount of CaO added increases from 100 mg / L to 300 mg / L, the total phosphorus can be reduced from 21.26 mg / L to 1.77 mg / L, but the pH of the water sample gradually increases to 10.7, exceeding the discharge standard; when Ca(OH)2 is added to 300 mg / L, the total phosphorus concentration is above 2 mg / L, and the phosphorus removal effect is not as good as CaO. CaO is selected as the subsequent calcium salt.

[0025] Embodiment 5-7 Take 300 ml of the leaching solution and place it in a 500 ml beaker, add 300 mg of polyferric sulfate, polyaluminium chloride and alum, stir at 500 rpm / min, stir for 5 min, let stand for 5 min, take the supernatant, filter with a 0.45 μm filter, and determine the pH and total phosphorus.

[0026] Table 2 Results of leachate treatment with different coagulants

[0027] Table 2 shows the pH and total phosphorus measured in the water samples of Examples 5-7. When an excess of 1000 mg / L of coagulant is added, the water samples are acidic, with a pH below 4.0, and the total phosphorus concentration has significant differences. The water samples treated with polyferric sulfate have the strongest acidity, pH=2.3, and the lowest total phosphorus concentration, indicating a good treatment effect. Polyferric sulfate is selected as the subsequent coagulant.

[0028] Example 8 Take 300 ml of the leachate and place it in a 500 ml beaker, add 90 mg of CaO, stir for 5 min, then add 126 mg of polyferric sulfate to adjust the pH of the solution to 8.7, stir at 500 rpm / min, stir for 5 min, let stand for 5 min, take the supernatant, filter with a 0.45 μm filter head, and determine the total phosphorus.

[0029] Example 9 Take 300 ml of the leaching solution and place it in a 500 ml beaker, add 90 mg of polyferric sulfate, stir at 500 rpm / min, stir for 7 min, let stand for 5 min, and measure the pH to 3.8. Then filter out the flocs, add 30 mg of CaO to adjust the water sample to neutral, pH 7.2, stir at 800 rpm / min, stir for 5 min, let stand for 5 min, take the supernatant, filter with a 0.45 μm filter, and measure the total phosphorus.

[0030] Table 3 Total phosphorus concentration in water samples treated with different reagent addition methods

[0031] The total phosphorus concentration in Example 8 is 3.28 mg / L. This method of adding calcium salt and coagulant together can adjust the pH of the water sample, but the total phosphorus concentration is still high. Calcium salt works better under alkaline conditions, and polyferric sulfate works better under acidic conditions. Therefore, CaO and polyferric sulfate should be used to treat wastewater in stages. The total phosphorus in Example 9 is 27.43 mg / L, mainly because CaO is used to adjust the pH of the water sample to neutral, and the required amount is small, while the total phosphorus concentration is related to the amount of CaO used, so the total phosphorus concentration is higher.

[0032] Example 10 Take 300 ml of the leaching solution and place it in a 500 ml beaker, add 90 mg of CaO, stir for 5 min at a stirring speed of 800 rpm / min, and filter to remove the precipitate. Then add 30 mg of montmorillonite (montmorillonite particle size is 1-10 microns) and stir at 500 rpm / min for 5 minutes, 27 mg of polyferric sulfate to adjust the solution pH to neutral, stir at a speed of 500 rpm / min, stir for 5 minutes, let stand for 5 minutes, take the supernatant and filter it with a 0.45 μm filter head to determine the total phosphorus.

[0033] Embodiment 11 Based on Example 10, the montmorillonite in Example 1 was changed to modified montmorillonite 1, and the modification method was as follows: 1) Add lanthanum chloride to the montmorillonite suspension and stir evenly to obtain a mixed solution, wherein the particle size of the montmorillonite is 1-10 microns, the mass concentration of the montmorillonite suspension is 0.3wt%, and the mass concentration of lanthanum chloride in the mixed solution is 15wt%; 2) Filter the solution in step 1), dry it, grind it, and then add montmorillonite, the particle size of which is 1-10 nanometers, to obtain modified montmorillonite.

[0034] Example 12 Based on Example 10, the montmorillonite in Example 1 was changed to modified montmorillonite 2, and the modification method was as follows: 1) Add lanthanum chloride and PTCDA to the montmorillonite suspension, stir evenly to obtain a mixed solution, the particle size of the montmorillonite is 1-10 microns, the mass concentration of the montmorillonite suspension is 3wt%, the mass concentration of lanthanum chloride in the mixed solution is 15wt%, and the mass concentration of PTCDA is 6wt%; 2) Filter the solution in step 1), dry it, grind it, and then add montmorillonite, the particle size of montmorillonite is 1-10 nanometers, to obtain modified montmorillonite.

[0035] Example 13 Based on Example 10, the montmorillonite in Example 1 was changed to modified montmorillonite 3, and the modification method was as follows: 1) Add lanthanum chloride and PTCDA to the montmorillonite suspension, stir evenly to obtain a mixed solution, the particle size of the montmorillonite is 1-10 microns, the mass concentration of the montmorillonite suspension is 0.3wt%, the mass concentration of lanthanum chloride in the mixed solution is 15wt%, and the mass concentration of PTCDA is 6wt%; 2) Filter the solution in step 1), dry it, grind it, and then add montmorillonite, the particle size of montmorillonite is 1-10 nanometers, to obtain modified montmorillonite.

[0036] Table 4 Results of wastewater treatment by modified montmorillonite

[0037] The pollutants in the water sample after treatment in Example 13 were tested, and the results are shown in Table 5: Table 5 Concentrations of other pollutants

[0038] As shown in Table 5, the pH of the treated water sample was 7.8, neutral, no Fe ions were detected, the Ca ion concentration was 109.1 mg / L, the Mg ion concentration was 25.7 mg / L, the total calcium and magnesium ions were 134.8 mg / L, the COD concentration dropped to 38 mg / L, and the sulfate concentration dropped to 197 mg / L, which met the first-level standard of the Integrated Wastewater Discharge Standard (GB8978-1996) and the Class III standard of the Groundwater Quality Standard GB / T 14848-2017 (total hardness ≤450 mg / L, iron ≤0.3 mg / L, COD ≤60 mg / L, sulfate ≤250 mg / L), and no additional pollutants were introduced. This is because lanthanum in lanthanum-modified montmorillonite adsorbs orthophosphate to form insoluble lanthanum phosphate, removes some phosphates, and the PTCDA that may be combined at the same time first forms a network structure on the surface of micron-level montmorillonite, increasing the adsorption sites and improving the adsorption effect.

[0039] The technical solution of the present invention is explained through the above embodiments, but the present invention is not limited to the above embodiments, that is, it does not mean that the present invention must rely on the above specific embodiments to be implemented. Any improvements made by technicians in the relevant field based on the present invention, or equivalent replacement of the materials selected by the present invention, etc., fall within the scope of protection of the patent.

Claims

1. A method for efficiently removing phosphorus from phosphate tailings leaching wastewater, characterized in that: The method comprises the following steps: (1) Add calcium salt to the wastewater from phosphate tailings leaching, stir evenly, let it stand and settle, then filter the precipitate; (2) adding montmorillonite to the filtrate obtained in step (1) and stirring evenly; (3) adding a flocculant to the solution obtained in step (2), stirring evenly, and allowing to settle; (4) taking the supernatant obtained in step (3) and filtering; Complete the removal of total phosphorus in the leaching water of phosphate tailings.

2. The method for efficient phosphorus removal from phosphate tailings leaching wastewater according to claim 1, characterized in that: The pH of the phosphate tailings leaching wastewater in step (1) is 6.5-7.8, the total phosphorus concentration is 80-120 mg / L, the COD concentration is 80-100 mg / L, and the sulfate concentration is 400-500 mg / L.

3. The method for efficient phosphorus removal from phosphate tailings leaching wastewater according to claim 1, characterized in that: The calcium salt in step (1) is one or more of CaO and Ca(OH)2, with an amount of 100-300 mg / L; Step (1) The stirring speed is 500-800 r / min, the stirring time is 5-10 min, and then filtering is performed with filter paper.

4. The method for efficient phosphorus removal from phosphate tailings leaching wastewater according to claim 1, characterized in that: In the step (2), the dosage of montmorillonite is 50-150 mg / L, and the stirring time is 5-10 min.

5. The method for efficient phosphorus removal from phosphate tailings leaching wastewater according to claim 1, characterized in that: The montmorillonite is modified before being added, and the modification method is to modify it with lanthanum chloride.

6. The method for efficient phosphorus removal from phosphate tailings leaching wastewater according to claim 1, characterized in that: The flocculant in step (3) is one or more of polyaluminium chloride, polyferric sulfate and alum, and the dosage is 80-1000 mg / L; In step (3), the stirring speed is 300-500 r / min, the stirring time is 3-5 min, and the standing time is 5 min.

7. The method for efficient phosphorus removal from phosphate tailings leaching wastewater according to claim 1, characterized in that: The step (4) is filtered using a 0.4-0.5 μm filter head.

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