Method for high-efficiency phosphorus removal from phosphorus tailing leaching wastewater
By using a stepwise treatment process involving calcium salts, montmorillonite, and coagulants, combined with the use of modified montmorillonite, the problems of complex reagent preparation, high cost, and poor efficacy in high-phosphorus wastewater treatment have been solved. This approach achieves efficient and low-cost wastewater purification, ensuring that the wastewater meets discharge standards.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HUBEI XINGFA CHEM GRP CO LTD
- Filing Date
- 2024-11-12
- Publication Date
- 2026-06-09
AI Technical Summary
Existing technologies for treating high-phosphorus wastewater suffer from problems such as complex reagent preparation processes, high costs, long reaction times, and poor results. In particular, they are difficult to effectively remove total phosphorus from high-concentration phosphorus tailings leaching wastewater, and thus cannot meet emission standards.
High-phosphorus wastewater is treated in stages using calcium salts, montmorillonite, and coagulants. Through stirring, settling, and filtration, combined with the use of modified montmorillonite, efficient phosphorus removal is achieved, reducing total phosphorus, COD, and sulfate in the water, ensuring that the wastewater meets discharge standards.
It achieves low-cost and efficient treatment of high-phosphorus wastewater, simplifies the process, shortens the reaction time, and eliminates the need for additional pH adjustment, ensuring that the effluent quality meets discharge standards.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of wastewater purification and treatment technology, specifically relating to a method for efficient phosphorus removal from phosphorus tailings leaching wastewater. Background Technology
[0002] Large-scale stockpiling of phosphate tailings can harm the surrounding ecological environment. When phosphate tailings are washed away or soaked by rainwater, residual chemicals in the tailings are released into the water, flowing into nearby water bodies and groundwater, causing damage to the ecological environment. High concentrations of pollutants in phosphate tailings include total phosphorus, COD, and sulfate, with total phosphorus levels severely exceeding standards and failing to meet emission standards.
[0003] Phosphorus removal methods for high-phosphorus wastewater include chemical and biological methods. Biological phosphorus removal is affected by factors such as influent conditions and operating conditions; relying solely on biological methods often results in effluent quality that does not meet standards. Chemical phosphorus removal methods include chemical precipitation, adsorption, and ion exchange. However, ion exchange is rarely used due to its high treatment cost.
[0004] Patent CN 109704446B discloses a phosphorus removal agent prepared by mixing cement and bentonite in a specific ratio, used to treat eutrophic water bodies. Total phosphorus can be reduced to 0.118-0.145 mg / L, with good treatment effect, long action time, and the treated water sample has a low phosphorus concentration (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 cost, and high efficiency. However, for inorganic high-phosphorus wastewater of 75 mg / L, when the composite material dosage is 0.5 g / L, the inorganic phosphorus removal rate is only 73%, which is not high treatment efficiency.
[0005] In addition to the aforementioned patents, current phosphorus removal agents still have the following problems in treating phosphorus-containing wastewater:
[0006] 1. The preparation process of phosphorus removal agents is complex, cumbersome, and requires numerous facilities.
[0007] 2. The amount of pesticide used is large, the economic cost is high, and it is not environmentally friendly.
[0008] 3. The drug reaction time is long, resulting in poor efficacy.
[0009] 4. Most phosphorus removal agents can only treat wastewater with low phosphorus content, with a concentration below 10 mg / L; however, they are not very effective in treating high-phosphorus wastewater (>50 mg / L) and cannot directly meet wastewater discharge standards (TP<0.5 mg / L).
[0010] Chemical precipitation is widely used due to its advantages such as short purification cycle, stable phosphorus removal effect, and strong targeting. Currently, commonly used chemical phosphorus removal agents on the market include calcium salts, aluminum salts, and iron salts. Calcium salts are effective precipitants for phosphorus removal, but excessive addition increases the total hardness and pH of the water, requiring additional pH adjustment and affecting the effluent quality. Aluminum and iron salts have coagulation effects, but the treated solution is acidic, resulting in only moderate phosphorus removal effectiveness; they typically play an auxiliary role. Adsorption, on the other hand, is suitable for treating low-concentration phosphorus-containing wastewater and is highly effective. Summary of the Invention
[0011] To address the aforementioned problems, this invention aims to provide a method for efficient phosphorus removal from leaching wastewater of phosphorus tailings. This method utilizes a phosphorus removal agent to treat the leaching wastewater in stages, reducing total phosphorus in the water. It employs calcium salts, montmorillonite, and a coagulant to jointly treat high-phosphorus wastewater, simultaneously reducing COD and sulfate levels. No pH adjustment of the water sample is required, ensuring that the wastewater meets the Class I standard of the "Integrated Wastewater Discharge Standard" (GB8978-1996) and the Class III standard of the "Groundwater Quality Standard" (GB / T 14848-2017), thus preventing secondary pollution of the water body.
[0012] The technical solution of this invention is as follows:
[0013] To solve the above-mentioned technical problems, the present invention provides the following technical solution:
[0014] A method for efficient phosphorus removal from phosphate tailings leaching wastewater, the method comprising the following steps:
[0015] (1) Add calcium salt to the leaching wastewater of phosphorus tailings, stir evenly, let it stand to settle, and then filter the precipitate.
[0016] (2) Add montmorillonite to the filtrate obtained in step (1) and stir well;
[0017] (3) Add flocculant to the solution obtained in step (2), stir evenly, and let it stand to settle;
[0018] (4) Take the supernatant obtained in step (3) and filter it;
[0019] Complete the removal of total phosphorus from the leaching water of phosphorus tailings.
[0020] Preferably, the pH of the leaching wastewater from the phosphorus tailings 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.
[0021] Preferably, the calcium salt in step (1) is one or more of CaO and Ca(OH)2, and the dosage is 100-300 mg / L;
[0022] Step (1) The stirring speed is 500-800 r / min and the stirring time is 5-10 min. Then filter with filter paper.
[0023] Preferably, in step (2), the dosage of montmorillonite is 50-150 mg / L, and the stirring time is 5-10 min.
[0024] Preferably, the montmorillonite is modified before being added, and the modification method is lanthanum chloride modification.
[0025] More preferably, the preparation method of modified montmorillonite includes the following steps:
[0026] 1) Add lanthanum chloride and PTCDA (3,4,9,10-perylenetetracarboxylic dianhydride) to the montmorillonite suspension, stir until homogeneous, and obtain a mixed solution. The particle size of montmorillonite is 1-10 micrometers, the mass concentration of the montmorillonite suspension is 0.1wt%-5wt%, the mass concentration of lanthanum chloride in the mixed solution is 1wt%-20wt%, and the mass concentration of PTCDA is 5-12wt%.
[0027] 2) Filter, dry, grind, and then add montmorillonite with a particle size of 1-10 nanometers to obtain modified montmorillonite.
[0028] Preferably, the flocculant in step (3) is one or more of polyaluminum chloride, polyferric sulfate and alum, and the dosage is 80-1000 mg / L;
[0029] Step (3) The stirring speed is 300-500 r / min, the stirring time is 3-5 min, and the standing time is 5 min.
[0030] Preferably, step (4) uses a 0.4-0.5μm filter, preferably 0.45μm.
[0031] Compared with the prior art, the beneficial effects of the present invention are:
[0032] (1) Low price: The calcium salt precipitant, montmorillonite and coagulant added to the leaching wastewater of phosphorus tailings in this invention are common chemical agents, which are inexpensive and used in small quantities, resulting in extremely low phosphorus removal costs.
[0033] (2) The process is simple. The wastewater treatment method in this 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 min, the treatment time is short, and the efficiency is high.
[0034] (3) High phosphorus removal efficiency. When a precipitant is added to high phosphorus wastewater, the total phosphorus concentration can be rapidly reduced. When modified montmorillonite and coagulant are added, 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 coagulated to reduce the wastewater. After step-by-step treatment, the pH, total phosphorus, sulfate, COD, total hardness and iron ions of the wastewater all meet the discharge standards.
[0035] The treatment method of the present invention can effectively solve the problem of high phosphorus wastewater, and the process is simple, has high phosphorus removal efficiency, and is inexpensive. Detailed Implementation
[0036] The technical solutions of the present invention will be clearly and completely described below with reference to specific embodiments. These embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the protection scope of the present invention.
[0037] In the context of this specification, except where expressly stated, any matters or issues not mentioned are made directly using techniques known in the art. Furthermore, any embodiment described in this patent can be freely combined with one or more other embodiments described in this patent, and the resulting technical solutions or ideas shall be considered part of the original disclosure or original record of this invention, and should not be regarded as new content not disclosed in this patent, unless those skilled in the art consider the combination to be clearly unreasonable.
[0038] The data points disclosed in this 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 considered as the range disclosed or described in this invention, regardless of whether each of these numerical points is disclosed herein.
[0039] raw material
[0040] The phosphorus tailings were selected from the tailings filter press workshop of a phosphorus mine in Yichang; the pH of the phosphorus tailings leaching wastewater was 7.1, and the total phosphorus was 88 mg / L; calcium oxide, calcium hydroxide, polyaluminum chloride, polyferric sulfate and alum were all of analytical grade for laboratory use.
[0041] Examples 1-3
[0042] 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 and let stand for 5 min. Take the supernatant and filter it with a 0.45 μm filter. Measure the pH and total phosphorus.
[0043] Example 4
[0044] 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 for 7 min, let stand for 5 min, take the supernatant, filter it with a 0.45 μm filter, and determine the pH and total phosphorus.
[0045] Table 1 Results of leachate treatment with different calcium salts
[0046]
[0047] Table 1 shows the pH and total phosphorus measured in water samples from Examples 1-4. As the CaO addition increased from 100 mg / L to 300 mg / L, the total phosphorus concentration decreased from 21.26 mg / L to 1.77 mg / L, but the pH of the water sample gradually increased to 10.7, exceeding the discharge standard. With Ca(OH)2 added to 300 mg / L, the total phosphorus concentration remained above 2 mg / L, indicating that the phosphorus removal effect was not as good as with CaO. CaO was subsequently chosen as the calcium salt.
[0048] Examples 5-7
[0049] Take 300 ml of the leachate and place it in a 500 ml beaker. Add 300 mg of polyferric sulfate, polyaluminum chloride and alum. Stir at 500 rpm / min for 5 min. Let stand for 5 min. Take the supernatant and filter it through a 0.45 μm filter. Measure the pH and total phosphorus.
[0050] Table 2 Results of leachate treatment with different coagulants
[0051]
[0052] Table 2 shows the pH and total phosphorus measured in water samples from Examples 5-7. When an excess of 1000 mg / L coagulant was added, the water samples became acidic, with a pH below 4.0. The total phosphorus concentrations showed significant differences, with the water sample treated with polyferric sulfate exhibiting the strongest acidity (pH=2.3) and the lowest total phosphorus concentration, indicating a better treatment effect. Polyferric sulfate was subsequently selected as the coagulant.
[0053] Example 8
[0054] Take 300 ml of the leachate and place it in a 500 ml beaker. Add 90 mg of CaO and 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 for 5 min and let stand for 5 min. Take the supernatant and filter it with a 0.45 μm filter. Determine the total phosphorus content.
[0055] Example 9
[0056] Take 300 ml of the leachate and place it in a 500 ml beaker. Add 90 mg of polyferric sulfate, stir at 500 rpm for 7 min, let stand for 5 min, and determine the pH to be 3.8. Then filter to remove flocculents, add 30 mg of CaO to adjust the water sample to neutral (pH 7.2), stir at 800 rpm for 5 min, let stand for 5 min, take the supernatant, filter through a 0.45 μm filter, and determine the total phosphorus.
[0057] Table 3 Total phosphorus concentration in water samples treated with different reagent addition methods
[0058]
[0059] In Example 8, the total phosphorus concentration was 3.28 mg / L. This method of adding both calcium salt and coagulant can adjust the pH of the water sample, but the total phosphorus concentration is still too high. Calcium salt works better under alkaline conditions, while polyferric sulfate works better under acidic conditions. Therefore, CaO and polyferric sulfate should be treated separately in the wastewater. In Example 9, the total phosphorus concentration was 27.43 mg / L. This was mainly because CaO was used to adjust the pH of the water sample to neutral, requiring a small amount. The total phosphorus concentration is related to the amount of CaO used, hence the higher total phosphorus concentration.
[0060] Example 10
[0061] Take 300 ml of the leachate and place it in a 500 ml beaker. Add 90 mg of CaO and stir for 5 min at a stirring speed of 800 rpm / min. Filter to remove the precipitate. Then add 30 mg of montmorillonite (montmorillonite particle size is 1-10 μm) and stir at 500 rpm / min for 5 min. Adjust the pH of the solution to neutral with 27 mg of polyferric sulfate, stir at 500 rpm / min for 5 min, let stand for 5 min, and filter the supernatant through a 0.45 μm filter. Determine the total phosphorus content.
[0062] Example 11
[0063] Based on Example 10, the montmorillonite in Example 1 was replaced with modified montmorillonite 1. The modification method was as follows:
[0064] 1) Add lanthanum chloride to the montmorillonite suspension and stir until homogeneous to obtain a mixed solution. The particle size of montmorillonite is 1-10 micrometers, the mass concentration of the montmorillonite suspension is 0.3 wt%, and the mass concentration of lanthanum chloride in the mixed solution is in the range of 15 wt%.
[0065] 2) Filter the solution from step 1), dry it, grind it, and then add montmorillonite with a particle size of 1-10 nanometers to obtain modified montmorillonite.
[0066] Example 12
[0067] Based on Example 10, the montmorillonite in Example 1 was replaced with modified montmorillonite 2. The modification method was as follows:
[0068] 1) Add lanthanum chloride and PTCDA to the montmorillonite suspension, stir evenly to obtain a mixed solution. The particle size of montmorillonite is 1-10 micrometers, the mass concentration of montmorillonite suspension is 3 wt%, the mass concentration range of lanthanum chloride in the mixed solution is 15 wt%, and the mass concentration range of PTCDA is 6 wt%.
[0069] 2) Filter the solution from step 1), dry it, grind it, and then add montmorillonite with a particle size of 1-10 nanometers to obtain modified montmorillonite.
[0070] Example 13
[0071] Based on Example 10, the montmorillonite in Example 1 was replaced with modified montmorillonite 3. The modification method was as follows:
[0072] 1) Add lanthanum chloride and PTCDA to the montmorillonite suspension, stir evenly to obtain a mixed solution. The particle size of montmorillonite is 1-10 micrometers, the mass concentration of montmorillonite suspension is 0.3 wt%, the mass concentration range of lanthanum chloride in the mixed solution is 15 wt%, and the mass concentration range of PTCDA is 6 wt%.
[0073] 2) Filter the solution from step 1), dry it, grind it, and then add montmorillonite with a particle size of 1-10 nanometers to obtain modified montmorillonite.
[0074] Table 4 Results of wastewater treatment with modified montmorillonite
[0075]
[0076] The pollutants in the water sample treated in Example 13 were tested, and the results are shown in Table 5:
[0077] Table 5 Concentrations of other pollutants
[0078]
[0079] As shown in Table 5, the treated water sample had a pH of 7.8, indicating neutrality. Fe ions were not detected, the Ca ion concentration was 109.1 mg / L, the Mg ion concentration was 25.7 mg / L, the total calcium and magnesium ion concentration was 134.8 mg / L, the COD concentration decreased to 38 mg / L, and the sulfate concentration decreased to 197 mg / L. This meets the Class I 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), with no additional pollutants introduced. This is because lanthanum adsorbs orthophosphate in lanthanum-modified montmorillonite, forming insoluble lanthanum phosphate. Removing some phosphate ions, and possibly simultaneously binding PTCDA, forms a network structure on the micron-level montmorillonite surface, increasing adsorption sites and improving adsorption efficiency.
[0080] The technical solutions of the present invention have been 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 those skilled in the art based on the present invention, or equivalent substitutions for the materials selected in the present invention, fall within the scope of patent protection.
Claims
1. A method for efficient phosphorus removal from leaching wastewater of phosphorus tailings, characterized in that: The method includes the following steps: (1) Add calcium salt to the leaching wastewater of phosphorus tailings, stir evenly, let it stand to settle and then filter the precipitate. The pH of the leaching wastewater of phosphorus tailings is 6.5-7.8, the total phosphorus concentration is 80-120 mg / L, the COD concentration is 80-100 mg / L, the sulfate concentration is 400-500 mg / L, and the calcium salt is one or more of CaO and Ca(OH)2, with a dosage of 100-300 mg / L. (2) Add montmorillonite to the filtrate obtained in step (1) and stir well; (3) Add flocculant to the solution obtained in step (2), stir evenly, and let it stand to settle; (4) Take the supernatant obtained in step (3) and filter it; Complete the removal of total phosphorus from the leaching water of phosphorus tailings; The modification method of montmorillonite includes the following steps: a) Add lanthanum chloride and PTCDA (3,4,9,10-perylenetetracarboxylic dianhydride) to the montmorillonite suspension, stir until homogeneous, and obtain a mixed solution. The particle size of montmorillonite is 1-10 micrometers, the mass concentration of the montmorillonite suspension is 0.3 wt%, the mass concentration of lanthanum chloride in the mixed solution ranges from 1 wt% to 20 wt%, and the mass concentration of PTCDA ranges from 5-12 wt%. b) Filter, dry, grind, and then add montmorillonite with a particle size of 1-10 nanometers to obtain modified montmorillonite.
2. The method for efficient phosphorus removal from leaching wastewater of phosphorus tailings according to claim 1, characterized in that: In step (1), the stirring speed is 500-800 r / min and the stirring time is 5-10 min, and then the mixture is filtered with filter paper.
3. The method for efficient phosphorus removal from leaching wastewater of phosphorus tailings according to claim 1, characterized in that: In step (2), the dosage of montmorillonite is 50-150 mg / L, and the stirring time is 5-10 min.
4. The method for efficient phosphorus removal from leaching wastewater of phosphorus tailings according to claim 1, characterized in that: The flocculant in step (3) is one or more of polyaluminum chloride, polyferric sulfate and alum, with a dosage of 80-1000 mg / L; Step (3) The stirring speed is 300-500 r / min, the stirring time is 3-5 min, and the standing time is 5 min.
5. The method for efficient phosphorus removal from leaching wastewater of phosphorus tailings according to claim 1, characterized in that: The step (4) involves filtration using a 0.4-0.5 μm filter.