Composite flocculant for treating copper mine tailing filling wastewater as well as preparation method and application of composite flocculant

Abstract

The invention discloses a composite flocculant for treating copper mine tailing filling wastewater and a preparation method and application thereof, the composite flocculant comprises anionic polyacrylamide, a medicament A and a medicament B, the medicament A is at least one of methyl cellulose, chitosan and bentonite, and the medicament B is at least one of sodium sulfate, aluminum sulfate and ferric chloride. The preparation method comprises the following steps: mixing the anionic polyacrylamide, the agent A and the agent B, and drying at the temperature of 60-120 DEG C to obtain the composite flocculant. The composite flocculant disclosed by the invention has the advantages of high settling speed, good flocculation effect, good stability, good adaptability and the like, can be widely used for treating copper mine tailing filling wastewater as a novel flocculant with excellent flocculation performance, can remarkably improve the settling rate, can effectively remove metal ions, organic pollutants and suspended matters in the wastewater, and has the advantages of high efficiency, high efficiency and the like. And moreover, the dosage is as low as 2g / ton of wastewater, the use value is high, and the application prospect is good.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, and relates to a composite flocculant for treating wastewater from copper mine tailings backfilling, its preparation method, and its application. Background Technology

[0002] Copper mine tailings backfill wastewater, as a type of mine wastewater, is rich in various metal ions, dissolved salts, and also includes sand and mud particles, mineral impurities, organic pollutants, acids, and alkalis. Direct discharge would severely impact the water bodies and soil surrounding the mining area. Traditional mine wastewater treatment technologies include sulfide precipitation, conventional treatment processes, bioleaching, and high-concentration slurry treatment. While these methods have certain advantages, they are generally limited by factors such as mine production and the environment.

[0003] Currently, the most widely used technology is the high-concentration slurry treatment (HDS process). This involves adding lime to adjust the pH of the wastewater, followed by the addition of flocculants to form flocs from neutral sludge, improving its settling performance in the thickening tank and achieving separation of bottom sludge and solid waste. However, existing flocculants, including inorganic, organic, and composite flocculants, still have the following drawbacks. For example, inorganic flocculants require large dosages, have a narrow applicable pH range, are prone to leaving metal ions, and have poor stability; organic flocculants, such as common synthetic polyacrylamide and natural polymers, have poor anti-interference capabilities. In addition, existing flocculants face the following challenges when treating copper mine tailings backfill wastewater: First, the complex chemical composition and high concentration of suspended solids in the wastewater can lead to poor floc selectivity and insufficient floc formation, affecting sedimentation efficiency. Second, some organic polymeric flocculants are prone to degradation under strong acid or strong alkali conditions, resulting in decreased flocculation activity and difficulty in adapting to the large pH fluctuations of the wastewater. At the same time, the compounding schemes of existing composite flocculants mostly rely on experience and lack targeted design for the characteristics of copper mine tailings wastewater. Their synergistic mechanism is still unclear, which limits further improvement in treatment effect. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a composite flocculant for treating copper mine tailings backfill wastewater with fast settling speed, good flocculation effect, good stability and good adaptability, as well as its preparation method and application.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A composite flocculant for treating wastewater from copper mine tailings backfilling, wherein the raw materials for preparing the composite flocculant include anionic polyacrylamide, reagent A and reagent B; reagent A is at least one of methylcellulose, chitosan and bentonite; and reagent B is at least one of sodium sulfate, aluminum sulfate and ferric chloride.

[0006] In a further improvement of the above-mentioned composite flocculant, the mass percentage of anionic polyacrylamide in the composite flocculant is 60% to 90%.

[0007] In a further improvement of the above-mentioned composite flocculant, the mass percentage of anionic polyacrylamide in the composite flocculant is 80% to 90%.

[0008] In a further improvement of the aforementioned composite flocculant, the anionic polyacrylamide has a viscosity-average molecular weight of 8 million to 17 million.

[0009] In a further improvement of the above-mentioned composite flocculant, the mass ratio of agent A to agent B in the composite flocculant is 1-3:1-3.

[0010] As a general technical concept, the present invention also provides a method for preparing a composite flocculant for treating wastewater from copper mine tailings backfilling, comprising the following steps: S1. Anionic polyacrylamide, reagent A, and reagent B are mixed to obtain a mixed reagent; reagent A is at least one of methylcellulose, chitosan, and bentonite; reagent B is at least one of sodium sulfate, aluminum sulfate, and ferric chloride. S2. The mixed agent is heated to a temperature of 60℃~120℃ and dried to obtain a composite flocculant.

[0011] In a further improvement to the above preparation method, in step S2, the drying temperature is 80℃~100℃; and the drying time is 12h~24h.

[0012] In a further improvement to the above preparation method, in step S1, the mass ratio of the anionic polyacrylamide to the total mass of reagent A and reagent B is 6-9:1-4; the viscosity-average molecular weight of the anionic polyacrylamide is 8 million to 17 million; and the mass ratio of reagent A to reagent B is 1-3:1-3.

[0013] In a further improvement to the above preparation method, in step S1, the mass ratio of the anionic polyacrylamide to the total mass of the reagent A and reagent B is 8-9:1-2. As a general technical concept, the present invention also provides an application of the above-mentioned composite flocculant or the composite flocculant prepared by the above-mentioned preparation method in the treatment of copper mine tailings backfill wastewater.

[0014] The above-mentioned application, further improved, includes the following steps: mixing the composite flocculant with copper mine tailings backfill wastewater, stirring, and allowing it to stand to complete the treatment of copper mine tailings backfill wastewater; the amount of composite flocculant added is 2g to 6g per ton of copper mine tailings backfill wastewater.

[0015] In a further improvement to the above application, the composite flocculant is mixed with the copper mine tailings backfill wastewater in the form of a composite flocculant solution; the mass percentage of the composite flocculant solution is 0.5‰ to 2‰; the stirring time is 10s to 50s; and the settling time is 0.5h to 3h.

[0016] Compared with the prior art, the advantages of the present invention are as follows: (1) In view of the shortcomings of existing composite flocculants, such as slow settling speed, poor flocculation effect, poor stability, and poor adaptability, and the resulting difficulty in treating copper mine tailings backfill wastewater, this invention creatively proposes a composite flocculant for treating copper mine tailings backfill wastewater. The composite flocculant includes anionic polyacrylamide, reagent A, and reagent B, wherein reagent A is at least one of methylcellulose, chitosan, and bentonite, and reagent B is at least one of sodium sulfate, aluminum sulfate, and ferric chloride. Compared with conventional composite flocculants, the composite flocculant of this invention uses anionic polyacrylamide as the main agent, which can efficiently capture colloidal particles through long-chain bridging to form large-sized flocs. On this basis, methylcellulose, chitosan, and bentonite are used as thickeners, which are combined with anionic polyacrylamide through hydrogen bonds to enhance the density of flocs and prevent breakage. At the same time, sodium sulfate, aluminum sulfate, and ferric chloride are used as inorganic salts to increase the ionic strength in the solution, reduce the zeta potential of the particle surface by compressing the double electric layer, and promote particle aggregation. Thus, it can be used to treat copper mine tailings backfill wastewater. Anionic polyacrylamide, thickener, and inorganic salts work together to construct a three-stage synergistic treatment system of "bridging-thickening-charge neutralization." Therefore, when used to treat copper mine tailings backfill wastewater, it not only significantly improves the settling rate but also effectively removes metal ions, organic pollutants, and suspended solids. In particular, the dosage of the composite flocculant is as low as 2 grams per ton of wastewater, and the treated water quality fully meets the discharge standards of GB25467-2010, such as a suspended solids removal rate exceeding 98% and a total metal ion concentration below the detection limit. Furthermore, the components of the composite flocculant in this invention are inexpensive and readily available, which helps reduce costs. Furthermore, the composite flocculant of this invention is suitable for treating suspended solids in HDS process wastewater from mines. In particular, it operates efficiently within a pH range of 6-9, overcoming the dependence of traditional flocculants on alkaline conditions and saving costs for practical engineering applications. For example, under neutral conditions (pH 7), the hydrogen bonding between anionic polyacrylamide and methylcellulose is enhanced, improving floc stability. Under acidic conditions (pH 6), the charge neutralization effect of Na2SO4 is significant, reducing the amount of lime slurry regulator required. The composite flocculant of this invention for treating copper mine tailings backfill wastewater has advantages such as fast settling speed, good flocculation effect, good stability, and good adaptability. As a novel flocculant with excellent flocculation performance, it can be widely used to treat copper mine tailings backfill wastewater, effectively purifying it and ensuring that the effluent meets relevant standards. It has high practical value and promising application prospects.

[0017] (2) In the composite flocculant of the present invention, by optimizing the mass percentage of anionic polyacrylamide to 60% to 90% and optimizing the mass ratio of reagent A to reagent B to 1 to 3: 1 to 3, the three-level synergistic effect of “bridging-thickening-electric neutralization” can be promoted, thereby improving the sedimentation efficiency and sedimentation effect of the composite flocculant, and further improving the purification effect of the composite flocculant on copper mine tailings backfill wastewater. In particular, it can significantly improve the removal rate of suspended solids in wastewater.

[0018] (3) In the composite flocculant of the present invention, the anionic polyacrylamide used has a viscosity-average molecular weight of 8 million to 17 million, which can assist in the neutralization or chelation of suspended solids (such as clay, mineral particles, etc.) and copper ions (Cu) in wastewater. 2+ Heavy metals such as copper ore precipitate, especially under acidic conditions (copper mine wastewater is often acidic), where the precipitation and flocculation effects are better. Furthermore, by optimizing the viscosity-average molecular weight of anionic polyacrylamide, both flocculation effect and pipe loss can be balanced. For example, when the molecular weight is higher than 17 million, the viscosity is too high, resulting in severe pipe loss during actual use, while when the molecular weight is lower than 8 million, although the viscosity is lower, the flocculation effect is poor.

[0019] (4) To address the shortcomings of existing preparation methods, such as easy agglomeration, poor dispersibility of components, and poor stability, this invention creatively proposes a method for preparing a composite flocculant for treating copper mine tailings backfill wastewater. The composite flocculant is prepared using a dry mixing + low-temperature drying method. On the one hand, the various agents are directly mixed together, and simple stirring ensures uniform mixing, avoiding agglomeration. On the other hand, drying at 60℃~120℃ effectively removes moisture while avoiding damage to the molecular structure of anionic polyacrylamide, thus significantly improving the stability of the composite agent. The agent stability can be extended to 24 months. This allows for the preparation of a composite flocculant for treating copper mine tailings backfill wastewater with low dosage, fast settling speed, good flocculation effect, good stability, and good adaptability. Furthermore, the preparation method of this invention has advantages such as simple process, convenient operation, readily available raw materials, low cost, and high preparation efficiency, making it suitable for large-scale preparation and easy for industrial application.

[0020] (5) The present invention also provides an application of composite flocculant in the treatment of copper mine tailings backfill wastewater. Specifically, the composite flocculant is mixed with copper mine tailings backfill wastewater, stirred, and allowed to stand to complete the effective treatment of copper mine tailings backfill wastewater. It has the advantages of low dosage of composite flocculant, low residual particulate matter in wastewater, and easy sedimentation of flocculent matter. Moreover, the effluent meets the discharge requirements stipulated in GB 25467-2010 Emission Standard of Pollutants for Copper, Nickel and Cobalt Industries. Detailed Implementation

[0021] The present invention will be further described below with reference to specific preferred embodiments, but this does not limit the scope of protection of the present invention.

[0022] Example 1 A composite flocculant for treating copper tailings backfill wastewater comprises the following raw materials in parts by weight: 80 parts anionic polyacrylamide, 15 parts methylcellulose, and 5 parts sodium sulfate.

[0023] In this embodiment, the viscosity-average molecular weight of the anionic polyacrylamide used is 14 million to 15 million.

[0024] A method for preparing a composite flocculant for treating copper tailings backfill wastewater as described in this embodiment includes the following steps: (1) Take 80 parts by weight of anionic polyacrylamide, 15 parts of methylcellulose and 5 parts of sodium sulfate respectively, add them to a stirrer and stir for 1 hour to obtain a mixed agent.

[0025] (2) The mixed agent obtained in step (1) is heated to 80°C and dried for 12 hours to remove the water in the mixed agent and obtain a composite flocculant for treating copper tailings backfill wastewater.

[0026] An application of the composite flocculant prepared in this embodiment in the treatment of copper mine tailings backfill wastewater includes the following steps: The composite flocculant was mixed with water to prepare a composite flocculant solution with a mass percentage of 1‰. The composite flocculant was added at a dosage of 4g per ton of copper mine tailings backfill wastewater. The composite flocculant solution was added to a copper mine wastewater (which is also a type of copper mine tailings backfill wastewater), stirred for 30 seconds, and allowed to stand for 1 hour to complete the treatment of the copper mine wastewater.

[0027] Water samples were taken from the upper layer for water quality analysis, and the results are shown in Table 1.

[0028] Table 1. Treatment effect of composite flocculant on copper mine wastewater in Example 1

[0029] Note: In Table 1, the wastewater volume is 1L. L "" indicates that the detection result is below the method detection limit.

[0030] As can be seen from Table 1, after adding the composite flocculant of the present invention to the wastewater of a copper mine, the removal rate of suspended solids in the upper water sample can reach 99%, and the total copper content is also significantly reduced, both meeting the national emission standards in GB 25467-2010 Emission Standards for Pollutants from Copper, Nickel and Cobalt Industries.

[0031] In this embodiment, the treatment effect of different amounts of composite flocculant on copper mine wastewater was also investigated. Except for the different amounts of composite flocculant, other conditions were the same, as shown in Table 2.

[0032] Table 2. Effects of different amounts of composite flocculant added in Example 1 on the treatment of copper mine wastewater.

[0033] Note: In Table 2, wastewater volume is 1L. L "" indicates that the detection result is below the method detection limit; the detection limit concentrations for each element are: copper 0.05 mg / L, lead 0.2 mg / L, zinc 0.05 mg / L, cadmium 0.05 mg / L, NH3-N 0.025 mg / L, COD 5 mg / L, and suspended solids 4 mg / L.

[0034] As shown in Table 2, the settling performance of wastewater significantly improved with increasing dosage of the composite flocculant. When the dosage increased from 2 g / ton to 4 g / ton, the time required for 1000 mL of wastewater to settle to 300 mL decreased from 30 seconds to 15 seconds, doubling the settling efficiency. Further increasing the dosage to 5-6 g / ton resulted in a stable settling time of approximately 14 seconds. Regarding pollutant removal, the suspended solids concentration showed a significant decreasing trend with increasing dosage, decreasing from 63 mg / L (2 g / ton) to 24 mg / L (6 g / ton). The COD removal effect reached its optimal level at a dosage of 4 g / ton (14 mg / L), and further increases in dosage resulted in a slight rebound. Notably, the detection results for all heavy metal indicators (copper, lead, zinc, and cadmium) were below the method detection limit and far below the emission limits specified in GB25467-2010. Experimental results show that a dosage of 4 g / ton can achieve good flocculation effect, ensuring both sedimentation efficiency and optimal COD removal effect.

[0035] In this embodiment, the treatment effect of different concentrations of composite flocculant solution on copper mine wastewater was also investigated. Except for the different concentrations of composite flocculant solution, other conditions were the same, as shown in Table 3.

[0036] Table 3. Treatment effect of different concentrations of composite flocculant solution on copper mine wastewater in Example 1

[0037] Note: In Table 3, the wastewater volume is 1L. L"" indicates that the detection result is below the method detection limit; the detection limit concentrations for each element are: copper 0.05 mg / L, lead 0.2 mg / L, zinc 0.05 mg / L, cadmium 0.05 mg / L, NH3-N 0.025 mg / L, COD 5 mg / L, and suspended solids 4 mg / L.

[0038] Table 3 shows that the settling performance of wastewater significantly improved with increasing concentration of the composite flocculant solution. When the concentration increased from 0.5‰ to 1‰, the time required for 1000mL of wastewater to settle to 300mL decreased from 30 seconds to 14 seconds, doubling the settling efficiency. Further increasing the concentration to 2‰ resulted in a gradual increase in settling time. Regarding pollutant removal, the suspended solids concentration showed a significant decreasing trend with increasing concentration, decreasing from 43mg / L (0.5‰) to 25mg / L (1‰). After increasing from 1‰ to 2‰, the suspended solids concentration stabilized at around 23mg / L. Notably, the detection results for all heavy metal indicators (copper, lead, zinc, and cadmium) were below the method detection limit and far below the emission limits specified in GB25467-2010. The experimental results indicate that selecting concentrations of 1‰ and 1.5‰ is sufficient to achieve good flocculation effects, ensuring both settling efficiency and optimal suspended solids removal. However, according to the actual production process of copper mines, the higher the flocculant concentration, the greater the pipe loss and the higher the energy consumption. Therefore, choosing to configure a flocculant with a concentration of 1‰ is more in line with the actual production needs.

[0039] In this embodiment, the treatment effect of composite flocculant on copper mine wastewater under different stirring time conditions was also investigated. Except for the different stirring time, the other conditions were the same, as shown in Table 4.

[0040] Table 4. Treatment effect of composite flocculant on copper mine wastewater under different stirring times in Example 1

[0041] Note: In Table 4, wastewater volume is 1L. L "" indicates that the detection result is below the method detection limit; the detection limit concentrations for each element are: copper 0.05 mg / L, lead 0.2 mg / L, zinc 0.05 mg / L, cadmium 0.05 mg / L, NH3-N 0.025 mg / L, COD 5 mg / L, and suspended solids 4 mg / L.

[0042] Table 4 shows that the settling performance of the wastewater significantly improved with increasing mixing time between the composite flocculant and the wastewater. When the mixing time increased from 10 s to 30 s, the suspended solids concentration showed a significant decreasing trend, dropping from 54 mg / L (10 s) to 22 mg / L (30 s). As the time increased from 30 s to 50 s, the suspended solids concentration remained stable at around 22 mg / L. The experimental results indicate that adjusting the mixing time between the flocculant and the wastewater to 30 s is sufficient to achieve a good flocculation effect, ensuring both settling efficiency and optimal suspended solids removal.

[0043] In this embodiment, the treatment effect of composite flocculant on copper mine wastewater under different settling time conditions was also investigated. Except for the different settling time, the other conditions were the same, as shown in Table 5.

[0044] Table 5. Treatment effect of composite flocculant on copper mine wastewater under different settling time conditions in Example 1.

[0045] Note: In Table 5, the wastewater volume is 1L. L "" indicates that the detection result is below the method detection limit; the detection limit concentrations for each element are: copper 0.05 mg / L, lead 0.2 mg / L, zinc 0.05 mg / L, cadmium 0.05 mg / L, NH3-N 0.025 mg / L, COD 5 mg / L, and suspended solids 4 mg / L.

[0046] As shown in Table 5, with increasing settling time (0.5h, 1h, 1.5h, and 3h respectively), the suspended solids concentration in the wastewater showed a significant decreasing trend, decreasing from 39 mg / L (0.5h) to 22 mg / L (1h). Furthermore, as the settling time increased from 1h to 3h, the suspended solids concentration remained stable at around 22 mg / L. The experimental results indicate that the flocculant achieves good flocculation effects in copper mine wastewater after settling for 1h, ensuring both sedimentation efficiency and optimal suspended solids removal. In actual production, the hydraulic retention time of the thickener is approximately 3h; therefore, the composite flocculation performance meets the actual production requirements.

[0047] In this embodiment, the treatment effect of the ratio of reagent A (methylcellulose) and reagent B (sodium sulfate) in the composite flocculant on copper mine wastewater was also investigated. Except for the different ratios of reagent A and reagent B, the other conditions were the same, as shown in Table 6.

[0048] Table 6. Effect of the ratio of reagent A and reagent B in the composite flocculant on the treatment of copper mine wastewater in Example 1.

[0049] Note: In Table 6, the wastewater volume is 1L. L "" indicates that the detection result is below the method detection limit; the detection limit concentrations for each element are: copper 0.05 mg / L, lead 0.2 mg / L, zinc 0.05 mg / L, cadmium 0.05 mg / L, NH3-N 0.025 mg / L, COD 5 mg / L, and suspended solids 4 mg / L.

[0050] Table 6 shows that the settling velocities and flocculation effects of methylcellulose and sodium sulfate vary significantly depending on their ratio. The experimental results indicate that a 3:1 ratio of methylcellulose to sodium sulfate achieves good flocculation in copper mine wastewater treatment, ensuring both settling efficiency and optimal suspended solids removal.

[0051] Comparative Example 1 A method for treating copper mine wastewater is basically the same as that in Example 1, except that in Comparative Example 1, single anionic polyacrylamide and polyaluminum chloride are used instead of the composite flocculant in Example 1 to treat the copper mine wastewater. The results are shown in Table 7.

[0052] Table 7. Treatment effects of polyacrylamide and polyaluminum chloride alone on copper mine wastewater in Comparative Example 1.

[0053] Note: In Table 7, wastewater volume is 1L. L "" indicates that the detection result is below the method detection limit; the detection limit concentrations for each element are: copper 0.05 mg / L, lead 0.2 mg / L, zinc 0.05 mg / L, cadmium 0.05 mg / L, NH3-N 0.025 mg / L, COD 5 mg / L, and suspended solids 4 mg / L.

[0054] As shown in Table 7, when polyacrylamide was used alone in copper mine wastewater, the removal efficiency of suspended solids in the upper layer of the water sample was only 75 mg / L, which is very close to the emission standard in GB 25467-2010 "Emission Standard of Pollutants for Copper, Nickel and Cobalt Industries". However, when polyaluminum chloride was used alone, the removal efficiency of suspended solids in the upper layer of the water sample was only 1538 mg / L, with a removal rate of only 32.8%, which exceeds the national emission standard in GB 25467-2010 "Emission Standard of Pollutants for Copper, Nickel and Cobalt Industries". In addition, although the suspended solids index after treatment with polyacrylamide alone can meet the requirements of GB 25467-2010 "Emission Standard of Pollutants for Copper, Nickel and Cobalt Industries", it is very close to the maximum emission value, which is easy to exceed the standard during production. The composite flocculant used in this invention can not only reduce suspended solids to below the national standard, but also reduce them to an even lower value, which is more in line with actual production.

[0055] Comparative Example 2 A method for treating copper mine wastewater using a composite flocculant is basically the same as the method in Example 1, except that the composite flocculant used in Comparative Example 2 includes 85 parts of anionic polyacrylamide and 15 parts of methylcellulose.

[0056] The analysis results of the upper water sample in Comparative Example 2 are shown in Table 8.

[0057] Table 8. Treatment effect of composite flocculant on copper mine wastewater in Comparative Example 2

[0058] Note: In Table 8, wastewater volume is 1L. L "" indicates that the detection result is below the method detection limit; the detection limit concentrations for each element are: copper 0.05 mg / L, lead 0.2 mg / L, zinc 0.05 mg / L, cadmium 0.05 mg / L, NH3-N 0.025 mg / L, COD 5 mg / L, and suspended solids 4 mg / L.

[0059] As can be seen from Table 8, after adding anionic polyacrylamide and methylcellulose to the wastewater of a copper mine, the removal efficiency of suspended solids in the upper water sample was only 50 mg / L, which is close to the 80 mg / L standard in the national standard GB 25467-2010 Emission Standard of Pollutants for Copper, Nickel and Cobalt Industries.

[0060] Comparative Example 3 A method for treating copper mine wastewater using a composite flocculant is basically the same as the method in Example 1, except that the composite flocculant used in Comparative Example 3 includes 85 parts of anionic polyacrylamide and 15 parts of sodium sulfate.

[0061] The analysis results of the upper water sample in Comparative Example 3 are shown in Table 9.

[0062] Table 9. Treatment effect of composite flocculant on copper mine wastewater in Comparative Example 3

[0063] Note: In Table 9, wastewater volume is 1L. L "" indicates that the detection result is below the method detection limit; the detection limit concentrations for each element are: copper 0.05 mg / L, lead 0.2 mg / L, zinc 0.05 mg / L, cadmium 0.05 mg / L, NH3-N 0.025 mg / L, COD 5 mg / L, and suspended solids 4 mg / L.

[0064] As can be seen from Table 9, after adding anionic polyacrylamide and sodium sulfate to the wastewater of a copper mine, the removal efficiency of suspended solids in the upper water sample was only 68 mg / L, which is close to the 80 mg / L standard in the national standard GB 25467-2010 Emission Standard of Pollutants for Copper, Nickel and Cobalt Industries.

[0065] Example 2 A method using the composite flocculant in Example 1 in high water volume (1000 m³) 3 A method for treating copper mine wastewater under conditions of / h includes the following steps: The composite flocculant prepared in Example 1 was mixed with water to prepare a composite flocculant solution with a mass percentage of 1‰. The composite flocculant was added at a dosage of 4g per ton of copper mine tailings backfill wastewater. The composite flocculant solution was pumped into the process flow of a copper mine wastewater treatment plant (same as in Example 1). After thorough mixing, the solution flowed by gravity into a thickening tank. Overflow water was collected from the periphery of the thickening tank, and water samples were taken every 4 hours for analysis. The analysis results are shown in Table 10. Table 10. Treatment effect of composite flocculant on copper mine wastewater under high water volume conditions in Example 2.

[0066] Note: In Table 10, the wastewater volume is 1L. L "" indicates that the detection result is below the method detection limit; the detection limit concentrations for each element are: copper 0.05 mg / L, lead 0.2 mg / L, zinc 0.05 mg / L, cadmium 0.05 mg / L, NH3-N 0.025 mg / L, COD 5 mg / L, and suspended solids 4 mg / L.

[0067] As shown in Table 10, after adding the composite flocculant to the wastewater treatment process of a copper tailings filling mine, the suspended solids in the effluent were only 10-20 mg / L, far below the national emission standards stipulated in GB 25467-2010 "Emission Standards for Pollutants from Copper, Nickel and Cobalt Industries". This further demonstrates that the composite flocculant provided by this invention for treating copper tailings filling wastewater has broad application prospects.

[0068] Example 3 A composite flocculant for treating copper tailings backfill wastewater comprises the following raw materials in parts by weight: 60 parts anionic polyacrylamide, 30 parts methylcellulose, and 10 parts sodium sulfate.

[0069] In this embodiment, the viscosity-average molecular weight of the anionic polyacrylamide used is 14 million to 15 million.

[0070] Example 4 A composite flocculant for treating copper tailings backfill wastewater comprises the following raw materials in parts by weight: 88 parts anionic polyacrylamide, 9 parts methylcellulose, and 3 parts sodium sulfate.

[0071] In this embodiment, the viscosity-average molecular weight of the anionic polyacrylamide used is 14 million to 15 million.

[0072] Table 11. Treatment effects of composite flocculants with different ratios in Examples 3-4 on copper mine wastewater.

[0073] Note: In Table 11, the wastewater volume is 1L. L "" indicates that the detection result is below the method detection limit; the detection limit concentrations for each element are: copper 0.05 mg / L, lead 0.2 mg / L, zinc 0.05 mg / L, cadmium 0.05 mg / L, NH3-N 0.025 mg / L, COD 5 mg / L, and suspended solids 4 mg / L.

[0074] Table 11 shows that in Examples 3-4, the treatment effects of two different ratios of composite flocculants (60:30:10 and 88:9:3) on copper mine wastewater were compared. Both ratios resulted in effluent suspended solids concentrations below the national standards (60 mg / L and 33 mg / L, respectively), with the 88:9:3 ratio showing superior removal efficiency. All heavy metal indicators were below the detection limit, further validating the high efficiency of the composite flocculant in removing heavy metals at different ratios.

[0075] Examples 5-9 A composite flocculant for treating copper tailings backfill wastewater is basically the same as in Example 1, except that in Examples 5-9, the viscosity-average molecular weight of the anionic polyacrylamide is 8-10 million, 10-12 million, 12-14 million, 14-15 million, and 15-17 million, respectively.

[0076] Table 12. Effects of different viscosity-average molecular weights of anionic polyacrylamides on the treatment of copper mine wastewater.

[0077] Note: In Table 12, wastewater volume is 1L. L "" indicates that the detection result is below the method detection limit; the detection limit concentrations for each element are: copper 0.05 mg / L, lead 0.2 mg / L, zinc 0.05 mg / L, cadmium 0.05 mg / L, NH3-N 0.025 mg / L, COD 5 mg / L, and suspended solids 4 mg / L.

[0078] As shown in Table 12, when the viscosity-average molecular weight of the anionic polyacrylamide in the composite flocculant varied within the range of 8 million to 17 million, the pH value of all effluent samples remained stable (7.2), and all pollutant indicators were far below the limits of the emission standards for copper industry pollutants in GB25467-2010. The removal efficiency of suspended solids and COD varied slightly at different molecular weights, with the best removal efficiency for suspended solids at a viscosity-average molecular weight of 14-15 million (24 mg / L), while the lowest removal efficiency for COD was at 12-14 million (14 mg / L). Overall, within this molecular weight range, the composite flocculant showed extremely significant removal efficiency for heavy metals such as copper, lead, zinc, and cadmium, all below the method detection limit, indicating good applicability and stability.

[0079] Examples 10-13 A method for preparing a composite flocculant for treating copper tailings backfill wastewater is basically the same as the preparation method in Example 1, except that in Examples 10-13, the drying temperatures are 60℃, 90℃, 100℃, and 120℃ respectively.

[0080] Table 13. Effects of different drying temperatures on the treatment of copper mine wastewater.

[0081] Note: In Table 13, the wastewater volume is 1L. L "" indicates that the detection result is below the method detection limit; the detection limit concentrations for each element are: copper 0.05 mg / L, lead 0.2 mg / L, zinc 0.05 mg / L, cadmium 0.05 mg / L, NH3-N 0.025 mg / L, COD 5 mg / L, and suspended solids 4 mg / L.

[0082] Table 13 shows that the composite flocculant, prepared at different drying temperatures (60℃~120℃), exhibited generally stable treatment effects on copper tailings wastewater. All effluent pH values ​​were 7.2, and all heavy metal indicators (total copper, total lead, total zinc, and total cadmium) were below the detection limits, meeting emission standards. Regarding suspended solids removal, the best effect (20 mg / L) was observed at a drying temperature of 80℃. Treatment effects fluctuated slightly at other temperatures, but remained well below the standard limit (80 mg / L). The removal effects of COD and ammonia nitrogen did not change significantly at different temperatures. The results indicate that this flocculant can effectively treat wastewater within a drying temperature range of 60℃~120℃, with 80℃ being the optimal drying condition.

[0083] The results above show that, compared with conventional flocculants, the composite flocculant of the present invention for treating copper mine tailings backfill wastewater has the advantages of fast settling speed, good flocculation effect, good stability, and good adaptability. It can effectively purify copper mine tailings backfill wastewater and make its effluent meet relevant standards. It has high use value and good application prospects. Meanwhile, addressing the shortcomings of existing preparation methods such as easy agglomeration, poor dispersibility of components, and poor stability, the present invention employs a dry mixing + low-temperature drying method to prepare the composite flocculant for treating copper mine tailings backfill wastewater. On the one hand, the various agents are directly mixed together, and simple stirring can achieve uniform mixing, avoiding the problem of agglomeration. On the other hand, drying at 60℃~120℃ effectively removes moisture while also avoiding damage to the molecular structure of anionic polyacrylamide, thereby significantly improving the stability of the composite agent. The agent stability can be extended to 24 months. Thus, a composite flocculant for treating copper mine tailings backfill wastewater can be prepared with low dosage, fast sedimentation speed, good flocculation effect, good stability, and good adaptability.

[0084] The above embodiments are merely preferred embodiments of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A composite flocculant for treating wastewater from copper mine tailings backfilling, characterized in that, The raw materials for preparing the composite flocculant include anionic polyacrylamide, reagent A, and reagent B; reagent A is at least one of methylcellulose, chitosan, and bentonite; reagent B is at least one of sodium sulfate, aluminum sulfate, and ferric chloride.

2. The composite flocculant according to claim 1, characterized in that, The composite flocculant contains 60% to 90% anionic polyacrylamide by mass.

3. The composite flocculant according to claim 2, characterized in that, The viscosity-average molecular weight of the anionic polyacrylamide is 8 million to 17 million.

4. The composite flocculant according to any one of claims 1 to 3, characterized in that, The mass ratio of agent A to agent B in the composite flocculant is 1-3:1-3.

5. A method for preparing a composite flocculant for treating wastewater from copper mine tailings backfilling, characterized in that, Includes the following steps: S1. Anionic polyacrylamide, reagent A, and reagent B are mixed to obtain a mixed reagent; reagent A is at least one of methylcellulose, chitosan, and bentonite; reagent B is at least one of sodium sulfate, aluminum sulfate, and ferric chloride. S2. Heat to a temperature of 60℃~120℃ and dry to obtain composite flocculant.

6. The preparation method according to claim 5, characterized in that, In step S2, the drying temperature is 80℃~100℃; the drying time is 12h~24h.

7. The preparation method according to claim 5 or 6, characterized in that, In step S1, the mass ratio of the anionic polyacrylamide to the total mass of the reagent A and reagent B is 6-9:1-4; the viscosity-average molecular weight of the anionic polyacrylamide is 8 million to 17 million; and the mass ratio of the reagent A to the reagent B is 1-3:1-3.

8. The application of a composite flocculant as described in any one of claims 1 to 4 or a composite flocculant prepared by any one of claims 5 to 7 in the treatment of wastewater from copper mine tailings backfilling.

9. The application according to claim 8, characterized in that, The process includes the following steps: mixing the composite flocculant with copper mine tailings backfill wastewater, stirring, and allowing it to stand to complete the treatment of the copper mine tailings backfill wastewater; the amount of composite flocculant added is 2g to 6g per ton of copper mine tailings backfill wastewater.

10. The application according to claim 9, characterized in that, The composite flocculant is mixed with the copper mine tailings backfill wastewater in the form of a composite flocculant solution; the mass percentage of the composite flocculant solution is 0.5‰ to 2‰; the stirring time is 10s to 50s; and the settling time is 0.5h to 3h.

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