System and method for cooperatively treating mine acid wastewater based on multi-stage modified ardealite

Abstract

The invention relates to the technical field of industrial pollutant cooperative treatment, in particular to a system and method for cooperatively treating mine acid wastewater based on multi-stage modified phosphogypsum. The system comprises a modified ardealite preparation unit, a wastewater treatment unit and a resource recovery unit, and the system converts ardealite into a high-activity material through purification, alkali modification and activation treatment, and is used for gradient purification and resource recovery of wastewater. The invention also provides a wastewater treatment method based on the system, and the method comprises the following steps: adding a modified material according to a ratio, regulating the pH value, and sequentially carrying out neutralization precipitation, deep precipitation, sulfate radical crystallization and residue solidification to realize efficient purification of acidic wastewater and resource utilization of byproducts. According to the method, waste is treated by waste, the problems of large sludge amount, difficult removal of sulfate radicals and phosphogypsum stockpiling pollution in a traditional treatment technology are solved, the wastewater treatment efficiency and the phosphogypsum utilization rate are improved, the secondary pollution is less, the resource recovery rate is high, and the method has both environmental and economic benefits.

Description

Technical Field

[0001] This invention relates to the field of industrial pollutant co-treatment technology, specifically to a system and method for co-treating acidic mine wastewater based on multi-stage modified phosphogypsum. Background Technology

[0002] Acid mine drainage (AMD) is a highly acidic, sulfate-rich wastewater produced during mining operations. It is also rich in various heavy metal ions (such as Fe). 2+ Mn 2+ Cu 2+ Zn 2+ Cd 2+ AMD (Ammonium sulfate) pollutes water bodies. Long-term discharge of AMD can severely damage surrounding water bodies, soil, and ecosystems, and may harm human health through the food chain. Currently, treatment methods for AMD mainly include neutralization precipitation (such as adding lime or sodium hydroxide), sulfide precipitation, biological methods, and adsorption methods. Among these, lime neutralization is widely used due to its simplicity and relatively low cost. However, this method has the following significant drawbacks: First, it produces a large amount of sludge containing heavy metals, which is difficult to dewater, has poor stability, poses secondary environmental risks, and is costly to treat. Second, during neutralization, precipitates such as gypsum may form, encapsulating unreacted lime particles, leading to reduced reagent utilization. Third, lime neutralization can only adjust pH and precipitate heavy metals; its ability to remove high concentrations of sulfate ions from wastewater is limited, easily leading to excessive sulfate levels in the effluent and causing pollution.

[0003] Phosphogypsum is a large-scale industrial solid waste discharged during the wet-process phosphoric acid production. Its main component is calcium sulfate dihydrate, and its global stockpiles are enormous. Long-term stockpiling not only occupies land, but also poses an environmental leaching risk due to its soluble phosphorus, fluorine, and trace heavy metal impurities. Achieving safe and high-value utilization of phosphogypsum has been a long-standing challenge. Phosphogypsum itself contains calcium and is weakly acidic, theoretically it could be used to neutralize acidic wastewater. However, raw phosphogypsum has many impurities, low reactivity, and poor efficiency, and it may introduce new pollutants, posing technical and environmental risks to its direct application.

[0004] Therefore, developing a synergistic treatment technology that can simultaneously dispose of phosphogypsum waste and efficiently and deeply treat acidic mine wastewater, while also realizing the resource utilization of by-products, is of great significance for reducing the cost of mine environmental governance and promoting the recycling of industrial solid waste. Summary of the Invention

[0005] The purpose of this invention is to overcome the existing problems of generating large amounts of hazardous sludge, high operating costs, difficulty in removing sulfate, and environmental pressure and technical bottlenecks caused by the large-scale stockpiling of phosphogypsum in existing methods for treating acidic mine wastewater. The invention provides a system and method for treating acidic mine wastewater based on multi-stage modified phosphogypsum, which is a waste-to-waste treatment system that is highly efficient and deep-processed and can achieve resource recovery.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a system for the synergistic treatment of acidic mine wastewater based on multi-stage modified phosphogypsum.

[0007] A system for the synergistic treatment of acidic mine wastewater based on multi-stage modified phosphogypsum includes a modified phosphogypsum preparation unit, a wastewater treatment unit, and a resource recovery unit. The modified phosphogypsum preparation unit includes a purification module, a modification module, and an activation module arranged in sequence. The phosphogypsum is processed by the preparation unit to obtain multi-stage modified phosphogypsum. The wastewater treatment unit is connected to the modified phosphogypsum preparation unit and is used to receive the multi-stage modified phosphogypsum and treat the acidic wastewater from the mine. The wastewater treatment unit includes a neutralization precipitation module, a deep precipitation module, and a sulfate treatment module arranged in sequence. The resource recovery unit is used to receive and process solid residues and / or liquid residues generated by the wastewater treatment unit.

[0008] Furthermore, the purification module is configured to perform low-temperature calcination and dilute acid washing treatment on phosphogypsum.

[0009] In some embodiments, the purification module is further equipped with a low-temperature calcining furnace and a dilute acid washing reactor. The low-temperature calcining furnace and the dilute acid washing reactor are connected by a material conveying pipeline to realize continuous washing treatment of the material after calcination of phosphogypsum.

[0010] Furthermore, the modification module is configured to mix and react the purified phosphogypsum with an alkaline modifier.

[0011] Furthermore, the alkaline modifier is selected from one or more of calcium hydroxide, calcium oxide, or magnesium oxide.

[0012] In some embodiments, the modification module is provided with a stirring and mixing reaction device, which is equipped with a temperature control component and a stirring paddle with adjustable speed to achieve uniform mixing and controllable reaction of purified phosphogypsum and alkaline modifier.

[0013] Furthermore, the activation module is configured to load the activator onto the surface of the modified phosphogypsum by in-situ growth or deposition.

[0014] Furthermore, the activator is selected from one or more of citric acid, tartaric acid, or sodium dodecyl sulfonate.

[0015] In some embodiments, the activation module is provided with a loading reaction device, which has an in-situ growth reaction chamber and a deposition reaction chamber built in.

[0016] Furthermore, the neutralization and precipitation module is equipped with a wastewater inlet, a multi-stage modified phosphogypsum feeding port, and a pH online monitoring component. This monitoring component is linked with the quantitative feeding device at the feeding port to achieve real-time pH control of the reaction.

[0017] Furthermore, the deep precipitation module is equipped with a precipitant quantitative dosing device and a solid-liquid separation component to achieve efficient separation of solid and liquid after the reaction.

[0018] Furthermore, the sulfate treatment module includes a reaction vessel, an evaporation and concentration device, and a cooling and crystallization device connected in sequence.

[0019] In some embodiments, the cooling crystallization apparatus is further connected to a solid-liquid separation and collection assembly for the separation and collection of solid sulfates.

[0020] Furthermore, the resource recycling unit is equipped with a residue mixing chamber and a pressing and molding device, and the residue mixing chamber is equipped with a stirring and mixing component.

[0021] Furthermore, the modified phosphogypsum preparation unit, wastewater treatment unit, and resource recycling unit are all connected by material conveying pipelines or solid waste conveying devices. Each pipeline and device is equipped with a flow control component to achieve continuous and automated operation of the entire system.

[0022] Secondly, the present invention provides a method for treating acidic mine wastewater based on the above-mentioned system, comprising the following steps: S1. The phosphogypsum is sequentially dried, pulverized, calcined at low temperature, and washed with dilute acid in the modified phosphogypsum preparation unit to obtain purified phosphogypsum; the purified phosphogypsum is mixed with an alkaline modifier and modified, and then an activator is loaded through in-situ growth or deposition to prepare multi-level modified phosphogypsum materials. S2. The multi-stage modified phosphogypsum material is added to the neutralization and precipitation module to neutralize the acidic mine wastewater. After the pH reaches the first preset value, solid-liquid separation is performed to obtain a first mixed liquid and a first solid residue. S3. Transfer the first mixture into the deep sedimentation module, add a precipitant and adjust the pH to the second preset value. After the reaction, the solid and liquid are separated to obtain the second mixture and the second solid residue. S4. The second mixture is transferred to the sulfate treatment module, a sulfate precipitant is added, and after evaporation, concentration and cooling crystallization, solid sulfate is obtained. S5. The first solid residue and the second solid residue are mixed and pressed into shape in the resource recycling unit to prepare a solidified material for mine backfilling.

[0023] Furthermore, the temperature of the low-temperature calcination is 160~260℃.

[0024] Furthermore, the multi-stage modified phosphogypsum is added according to the molar ratio of the effective alkalinity provided by the phosphogypsum to the initial acidity of the wastewater, wherein the molar ratio of the effective alkalinity to the initial acidity of the wastewater is 1~1.5:1.

[0025] Furthermore, the precipitant is sodium sulfide or soluble phosphate, and its dosage is 5% to 10% of the mass of the multi-stage modified phosphogypsum material.

[0026] Furthermore, the first preset pH value is 3.5~4.5, and the second preset pH value is 6.0~7.0.

[0027] Furthermore, the sulfate precipitant includes sodium chloride, sodium sulfate, ammonium chloride, or ammonium sulfate.

[0028] Beneficial effects This invention effectively overcomes many shortcomings of existing acidic wastewater treatment technologies for mines, solving the problems of generating large amounts of hazardous sludge, high risk of secondary pollution, and insufficient sulfate removal associated with traditional methods. Simultaneously, the system provided by this invention breaks through the bottleneck of raw phosphogypsum having many impurities, low activity, poor purification effect when used directly, and easily introducing new pollution. Through multi-stage modification treatment of phosphogypsum, its reactivity and purification performance are significantly improved. This system can achieve highly efficient removal of heavy metals and sulfate from acidic mine wastewater, ensuring that the effluent meets standards, while significantly reducing the generation of secondary pollutants.

[0029] This invention achieves the co-treatment of industrial solid waste and acidic mine wastewater through waste-to-waste conversion. It transforms phosphogypsum into a highly efficient wastewater treatment material, completely eliminating the environmental pressure of phosphogypsum stockpiling and promoting its high-value resource utilization. Through a resource recovery unit, the treated residue can be made into mine backfill material, while solid sulfate is recovered, realizing the resource recycling of pollutants. This significantly reduces overall treatment costs, offering environmental, economic, and social benefits, and has broad application prospects. Attached Figure Description

[0030] The present invention will be further described below with reference to the accompanying drawings and embodiments: Figure 1 This is a flowchart of a method for treating acidic wastewater from mines, as described in an embodiment of the present invention. Detailed Implementation

[0031] Example 1: A system for the synergistic treatment of acidic mine wastewater based on multi-stage modified phosphogypsum This embodiment provides a system for the synergistic treatment of acidic mine wastewater based on multi-stage modified phosphogypsum. The system is as follows: Figure 1 As shown.

[0032] A system for the synergistic treatment of acidic mine wastewater based on multi-stage modified phosphogypsum includes a modified phosphogypsum preparation unit, a wastewater treatment unit, and a resource recovery unit. The modified phosphogypsum preparation unit includes a purification module, a modification module, and an activation module arranged in sequence. The phosphogypsum is processed by the preparation unit to obtain multi-stage modified phosphogypsum. The wastewater treatment unit is connected to the modified phosphogypsum preparation unit and is used to receive the multi-stage modified phosphogypsum and treat the acidic wastewater from the mine. The wastewater treatment unit includes a neutralization precipitation module, a deep precipitation module, and a sulfate treatment module arranged in sequence. The resource recovery unit is used to receive and process solid residues and / or liquid residues generated by the wastewater treatment unit.

[0033] Furthermore, the purification module is configured to perform low-temperature calcination and dilute acid washing on phosphogypsum to remove soluble phosphorus, fluorine, and some heavy metal impurities, thereby improving the purity and reactivity of the phosphogypsum.

[0034] In some embodiments, the purification module is further equipped with a low-temperature calcining furnace and a dilute acid washing reactor. The low-temperature calcining furnace and the dilute acid washing reactor are connected by a material conveying pipeline to realize continuous washing treatment of the material after calcination of phosphogypsum.

[0035] Furthermore, the modification module is configured to mix and react the purified phosphogypsum with an alkaline modifier.

[0036] Furthermore, the alkaline modifier is selected from one or more of calcium hydroxide, calcium oxide, or magnesium oxide.

[0037] In some embodiments, the modification module is provided with a stirring and mixing reaction device, which is equipped with a temperature control component and a stirring paddle with adjustable speed to achieve uniform mixing and controllable reaction of purified phosphogypsum and alkaline modifier.

[0038] Furthermore, the activation module is configured to load the activator onto the surface of the modified phosphogypsum through in-situ growth or deposition, thereby enhancing the modified phosphogypsum's ability to adsorb, complex, or precipitate heavy metal ions.

[0039] Furthermore, the activator is selected from one or more of citric acid, tartaric acid, or sodium dodecyl sulfonate.

[0040] In some embodiments, the activation module is provided with a loading reaction device, which has an in-situ growth reaction chamber and a deposition reaction chamber built in.

[0041] Furthermore, the neutralization and precipitation module is equipped with a wastewater inlet, a multi-stage modified phosphogypsum feeding port, and a pH online monitoring component. This monitoring component is linked with the quantitative feeding device at the feeding port to achieve real-time pH control of the reaction.

[0042] Furthermore, the deep precipitation module is equipped with a precipitant quantitative dosing device and a solid-liquid separation component to achieve efficient separation of solid and liquid after the reaction.

[0043] Furthermore, the sulfate treatment module includes a reaction vessel, an evaporation and concentration device, and a cooling and crystallization device connected in sequence.

[0044] In some embodiments, the cooling crystallization apparatus is further connected to a solid-liquid separation and collection assembly for the separation and collection of solid sulfates.

[0045] Furthermore, the resource recycling unit is equipped with a residue mixing chamber and a pressing and molding device, and the residue mixing chamber is equipped with a stirring and mixing component.

[0046] Furthermore, the modified phosphogypsum preparation unit, wastewater treatment unit, and resource recycling unit are all connected by material conveying pipelines or solid waste conveying devices. Each pipeline and device is equipped with a flow control component to achieve continuous and automated operation of the entire system.

[0047] Example 2: A method for treating acidic mine wastewater based on the system of Example 1 This embodiment describes a method for treating acidic mine wastewater based on the system of Embodiment 1, the process of which is as follows: Figure 1 As shown. The method includes the following steps: S1. The phosphogypsum is sequentially dried, pulverized, calcined at low temperature, and washed with dilute acid in the modified phosphogypsum preparation unit to obtain purified phosphogypsum; the purified phosphogypsum is mixed with an alkaline modifier and modified, and then an activator is loaded through in-situ growth or deposition to prepare multi-level modified phosphogypsum materials. S2. The multi-stage modified phosphogypsum material is added to the neutralization and precipitation module to neutralize the acidic mine wastewater. After the pH reaches the first preset value, solid-liquid separation is performed to obtain a first mixed liquid and a first solid residue. S3. Transfer the first mixture into the deep sedimentation module, add a precipitant and adjust the pH to the second preset value. After the reaction, the solid and liquid are separated to obtain the second mixture and the second solid residue. S4. The second mixture is transferred to the sulfate treatment module, a sulfate precipitant is added, and after evaporation, concentration and cooling crystallization, solid sulfate is obtained. S5. The first solid residue and the second solid residue are mixed and pressed into shape in the resource recycling unit to prepare a solidified material for mine backfilling.

[0048] Furthermore, the temperature of the low-temperature calcination is 160~260℃.

[0049] Furthermore, the multi-stage modified phosphogypsum is added according to the molar ratio of the effective alkalinity provided by the phosphogypsum to the initial acidity of the wastewater, wherein the molar ratio of the effective alkalinity to the initial acidity of the wastewater is 1~1.5:1.

[0050] Furthermore, the precipitant is sodium sulfide or soluble phosphate, and its dosage is 5% to 10% of the mass of the multi-stage modified phosphogypsum material.

[0051] Furthermore, the first preset pH value is 3.5~4.5, and the second preset pH value is 6.0~7.0.

[0052] Furthermore, the sulfate precipitant includes sodium chloride, sodium sulfate, ammonium chloride, or ammonium sulfate.

[0053] This embodiment also provides a specific example of applying the above method to acidic wastewater from mines.

[0054] Acidic wastewater from a lead-zinc mine was selected as the treatment target (influent pH around 2.3, sulfate content approximately 3200 mg / L, and Pb² content). + Zn² + Cd² + Cu² + (equal to heavy metal ions), processed using the system described in Example 1, with the specific steps as follows: Preparation of multi-stage modified phosphogypsum: Industrial waste phosphogypsum was selected, dried and pulverized at 85℃, calcined at 240℃ for 3 hours, and then washed with 5% dilute sulfuric acid to obtain purified phosphogypsum; an alkaline modifier was added to the purified phosphogypsum, and the mixture was stirred and reacted at 65℃ for 2 hours. After centrifugation and dehydration, the mixture was in-situ deposited with 3% citric acid solution at 45℃ for 1.5 hours, and then spray-dried to obtain multi-stage modified phosphogypsum.

[0055] Neutralization and precipitation treatment: Acidic mine wastewater is sent to the neutralization and precipitation module, and multi-stage modified phosphogypsum is added at a ratio of 10.4 kg / m³ of wastewater. The reaction pH is adjusted to 4.0. After 90 min of reaction, solid and liquid are separated to obtain the first mixed liquid and the first solid residue. The content of heavy metal ions in the first mixed liquid is significantly reduced.

[0056] Deep sedimentation treatment: The first mixture is transferred to the deep sedimentation module, a precipitant is added and the pH is adjusted to 6.8. After reacting for 60 minutes, solid and liquid are separated to obtain a second mixture and a second solid residue. The pH of the second mixture is stable between 6.8 and 7.5, and the content of heavy metal ions is reduced to below the emission standard limit.

[0057] Sulfate treatment and resource recovery: Sodium chloride precipitant is added to the second mixture. After reaction, the mixture is concentrated by evaporation, cooled and crystallized, and then separated into solid and liquid components to obtain solid sulfate and treated water. The treated water meets the Class I standard of mine wastewater discharge and can be discharged directly.

[0058] Solid residue recycling: The first and second solid residues are mixed, an auxiliary molding agent is added, the moisture content is adjusted, and the mixture is pressed into shape under a pressure of 15 MPa. It is then cured for 7 days at 25°C and 85% relative humidity to obtain a solidified material for mine backfilling.

[0059] This embodiment achieves the standard treatment of acidic wastewater from mines and the resource utilization of waste phosphogypsum. The treatment process is continuous and automated, with low cost, and combines environmental protection and economic benefits.

[0060] The above embodiments are merely preferred technical solutions of the present invention and should not be considered as limitations on the present invention. The embodiments and features described in this application can be arbitrarily combined with each other without conflict. The scope of protection of the present invention should be limited to the technical solutions described in the claims, including equivalent substitutions of the technical features described in the claims. That is, equivalent substitutions and improvements within this scope are also within the scope of protection of the present invention.

Claims

1. A system for treating mine acid wastewater based on multi-stage modified phosphogypsum, characterized in that, It includes a modified phosphogypsum preparation unit, a wastewater treatment unit, and a resource recycling unit; The modified phosphogypsum preparation unit includes a purification module, a modification module, and an activation module arranged in sequence. The phosphogypsum is processed by the preparation unit to obtain multi-stage modified phosphogypsum. The wastewater treatment unit is connected to the modified phosphogypsum preparation unit and is used to receive the multi-stage modified phosphogypsum and treat the acidic wastewater from the mine. The wastewater treatment unit includes a neutralization precipitation module, a deep precipitation module, and a sulfate treatment module arranged in sequence. The resource recovery unit is used to receive and process solid residues and / or liquid residues generated by the wastewater treatment unit.

2. The system according to claim 1, characterized in that, The purification module is configured to perform low-temperature calcination and dilute acid washing treatment on phosphogypsum.

3. The system according to claim 1, characterized in that, The modification module is configured to mix and react the purified phosphogypsum with an alkaline modifier; the alkaline modifier is selected from one or more of calcium hydroxide, calcium oxide, or magnesium oxide.

4. The system according to claim 1, characterized in that, The activation module is configured to load an activator onto the surface of modified phosphogypsum by in-situ growth or deposition; the activator is selected from one or more of citric acid, tartaric acid, or sodium dodecyl sulfonate.

5. A method for treating acidic mine wastewater based on the system described in any one of claims 1-4, characterized in that, Includes the following steps: S1. The phosphogypsum is sequentially dried, pulverized, calcined at low temperature, and washed with dilute acid in the modified phosphogypsum preparation unit to obtain purified phosphogypsum; the purified phosphogypsum is mixed with an alkaline modifier and modified, and then an activator is loaded through in-situ growth or deposition to prepare multi-level modified phosphogypsum materials. S2. The multi-stage modified phosphogypsum material is added to the neutralization and precipitation module to neutralize the acidic mine wastewater. After the pH reaches the first preset value, solid-liquid separation is performed to obtain a first mixed liquid and a first solid residue. S3. Transfer the first mixture into the deep sedimentation module, add a precipitant and adjust the pH to the second preset value. After the reaction, the solid and liquid are separated to obtain the second mixture and the second solid residue. S4. The second mixture is transferred to the sulfate treatment module, a sulfate precipitant is added, and after evaporation, concentration and cooling crystallization, solid sulfate is obtained. S5. The first solid residue and the second solid residue are mixed and pressed into shape in the resource recycling unit to prepare a solidified material for mine backfilling.

6. The method according to claim 5, characterized in that, The temperature for the low-temperature calcination is 160~260℃.

7. The method according to claim 5, characterized in that, The multi-stage modified phosphogypsum is added according to the molar ratio of the effective alkalinity provided by the phosphogypsum to the initial acidity of the wastewater, wherein the molar ratio of the effective alkalinity to the initial acidity of the wastewater is 1~1.5:

1.

8. The method according to claim 5, characterized in that, The precipitant is sodium sulfide or soluble phosphate, and its dosage is 5% to 10% of the mass of the multi-stage modified phosphogypsum material.

9. The method according to claim 5, characterized in that, The first preset pH value is 3.5~4.5, and the second preset pH value is 6.0~7.

0.

10. The method according to claim 5, characterized in that, The sulfate precipitant includes sodium chloride, sodium sulfate, ammonium chloride, or ammonium sulfate.

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