A red mud-based acidic mine water treatment agent, its preparation method and application method

Abstract

This application relates to the field of wastewater treatment technology, specifically disclosing an acidic mine water treatment agent based on red mud, its preparation method, and its application method. The treatment agent comprises the following raw materials in parts by weight: 100 parts of pre-treated red mud by acid washing, 1-10 parts of humic acid, and 5-20 parts of an inert carrier. This application reduces the initial reactivity of the red mud through acid washing pretreatment, and then achieves spatial isolation and reaction rate control of the two-phase reaction between red mud and humic acid by incorporating an inert carrier. This not only ensures the stability of the treatment agent during preparation and storage, but also ensures that the effective components are gradually and synergistically released in the AMD as expected during use, achieving efficient neutralization, adsorption, and stabilization.

Description

Technical Field

[0001] This application relates to the field of wastewater treatment technology, and more specifically, to an acidic mine water treatment agent based on red mud, and its preparation and application methods. Background Technology

[0002] Acid mine drainage (AMD) is a typical acidic wastewater generated during mining operations. Its pH value is typically ≤3, and it contains high concentrations of sulfates, iron, aluminum, and various heavy metal ions. Direct discharge without effective treatment can severely damage aquatic ecosystems, pollute soil, and threaten human health. Currently, AMD treatment methods mainly include neutralization precipitation, adsorption, and bioremediation, but these methods generally suffer from high costs, complex processes, and the risk of secondary pollution.

[0003] Red mud is a large quantity of alkaline solid waste generated during the alumina industrial production process. Its main components are Fe2O3, Al2O3, SiO2, and small amounts of calcium and sodium compounds. Red mud is characterized by its strong alkalinity, large specific surface area, and rich content of active metal oxides. It can neutralize acidic wastewater and adsorb and precipitate some heavy metal ions, achieving "waste treatment with waste." In recent years, research on using red mud to treat AMD has gradually increased, but its practical application still has certain limitations: on the one hand, alkaline ions such as sodium and potassium in red mud are easily soluble, which may lead to an increase in effluent salinity; on the other hand, the trace heavy metals contained in red mud itself may dissolve during water treatment, causing secondary pollution.

[0004] To improve the treatment efficiency of red mud and inhibit its release of heavy metals, current research often combines red mud with organic modifiers. Humic acid and its salts, due to their abundant functional groups (such as carboxyl and phenolic hydroxyl groups) and strong complexing ability, are widely used for red mud modification. For example, Chinese patent CN117101600A discloses a heavy metal ion adsorbent, its preparation method, and its application. This method enhances the complexation and fixation effect on heavy metals by mixing red mud with steel slag and sodium humate (a type of sodium humate) for AMD treatment, while also improving the dispersibility and reactivity of the red mud. However, this method still has significant shortcomings: sodium humate is highly water-soluble and easily lost with the effluent during treatment, reducing its residue in the sludge and affecting long-term stability. It also introduces a large amount of sodium ions into the system, exacerbating the problem of excessive sodium concentration in the effluent. Furthermore, the strong dispersing effect of sodium humate hinders the aggregation of red mud particles, resulting in small flocs with poor settling performance and difficulty in solid-liquid separation.

[0005] To address the aforementioned issues, this study proposes using humic acid instead of sodium humate as a complexing modifier to avoid the introduction of sodium ions and enhance the settling properties and stability of the sludge. However, humic acid itself contains a large number of acidic functional groups. If directly mixed with alkaline red mud, it not only affects the overall stability of the composite material but may also trigger a violent acid-base reaction during use, which is detrimental to the control of the treatment process and the durability of the treatment effect. Therefore, how to optimize the preparation process of the red mud-humic acid composite system and balance its reactivity and structural stability has become an urgent technical problem to be solved in this field. Summary of the Invention

[0006] To address the aforementioned technical problems, this application provides an acidic mine water treatment agent based on red mud, along with its preparation and application methods. This application reduces the initial reactivity of red mud through acid washing pretreatment, and then achieves spatial isolation and reaction rate control of the two-phase reaction between red mud and humic acid by incorporating an inert carrier. This transforms the inevitable acid-base neutralization reaction, which is a rapid and violent reaction detrimental to material stability, into a mild and controllable gradual reaction. This not only ensures the stability of the treatment agent during preparation and storage but also guarantees that, during use, the active ingredients are gradually and synergistically released in the AMD as expected, achieving efficient neutralization, adsorption, and stabilization.

[0007] In a first aspect, this application provides an acidic mine water treatment agent based on red mud, employing the following technical solution: An acidic mine water treatment agent based on red mud comprises the following raw materials in parts by weight: 100 parts of pre-treated red mud by acid washing, 1-10 parts of humic acid, and 5-20 parts of inert carrier.

[0008] More preferably, the acidic pretreatment step of the red mud is as follows: the red mud and the pickling solution are mixed at a solid-liquid ratio of 1g / (5-10)mL, and the mixture is continuously mechanically stirred at a speed of 100-200rpm for 0.5-1.5h at a temperature of 25-50℃. After the reaction is completed, the mixture is filtered to separate the solids, which are then washed with water and dried to obtain the final product.

[0009] More preferably, the pickling solution is hydrochloric acid or sulfuric acid. To reduce the possibility of small amounts of calcium sulfate precipitation caused by sulfuric acid, which could cover the pores on the surface of the red mud, the pickling solution is preferably hydrochloric acid.

[0010] More preferably, the concentration of the pickling solution is 0.05-0.5 mol / L.

[0011] Acid washing pretreatment removes free, highly reactive alkaline substances such as Na₂O, NaOH, and Na₂CO₃ from the surface or interstitial spaces of red mud, preventing violent and rapid acid-base neutralization reactions between red mud and humic acid during storage or mixing. This low-concentration, short-duration, and controlled-dosage acid washing preserves the structural alkali within the red mud particles, ensuring the normal processing of mine water from red mud. Furthermore, after surface acid pretreatment, the surface reactivity of the red mud is passivated. When added to AMD (Advanced Dioxide Treatment), the acid gradually penetrates and dissolves the internal structural alkali, achieving a smoother and more persistent neutralization process. This is highly beneficial for the gradual precipitation and removal of heavy metals and the stabilization of the effluent pH.

[0012] More preferably, the inert carrier is at least one of diatomaceous earth, kaolin, and attapulgite.

[0013] The inert carrier plays two main roles. First, the carrier powder disperses between the red mud and humic acid particles, increasing the microscopic distance between them and reducing the instantaneous, large-scale contact area, thereby further slowing down the reaction rate. Second, when treating AMD, the dissolved components of humic acid and red mud are adsorbed onto the carrier surface, which has a huge specific surface area. The reaction occurs more at this new interface provided by the carrier, which helps to form a more stable and structured precipitate.

[0014] More preferably, the raw material further includes one or more functional components, wherein the functional components are selected from at least one of chemical precipitants, redox agents, flocculants, and structure modifiers.

[0015] More preferably, the chemical precipitant is at least one of phosphate rock powder, magnesium phosphate rock powder, or ferrous sulfide.

[0016] More preferably, the redox agent is at least one of zero-valent iron or persulfate.

[0017] More preferably, the flocculant is at least one of polymeric metal silicate, chitosan, and polyacrylamide.

[0018] More preferably, the structure modifier is at least one of porous ceramic microspheres or biochar.

[0019] Secondly, this application provides a method for preparing an acidic mine water treatment agent based on red mud, using the following technical solution: A method for preparing an acidic mine water treatment agent based on red mud includes the following steps: The red mud was pretreated by acid washing, followed by water washing and drying to obtain pretreated red mud. An inert carrier is added to water to form a slurry, humic acid is added, the mixture is stirred evenly, and then dried to obtain a composite powder. The pretreated red mud, composite powder, and functional components are uniformly mixed to obtain the treatment agent.

[0020] Thirdly, this application provides a method for using an acidic mine water treatment agent based on red mud, employing the following technical solution: A method for using an acidic mine water treatment agent based on red mud includes the following steps: The treatment agent is added to acidic mineral water and stirred for a period of time. After the reaction is completed, solid-liquid separation is performed to obtain treated effluent and stabilized sludge.

[0021] More preferably, the dosage of the treatment agent is 5-200 g / L, based on the volume of the acidic mineral water.

[0022] More preferably, the stirring reaction time is 1-8 hours.

[0023] In summary, this application has the following beneficial effects: This application significantly reduces the environmental risk of heavy metal re-leaching from treated sludge (red mud) by using humic acid and leveraging its ability to solidify heavy metals. Furthermore, by combining red mud, humic acid, and an inert carrier in a single process, simultaneous neutralization, heavy metal adsorption, and stabilization are achieved, thereby improving treatment efficiency, simplifying operation, and avoiding the use of sodium humate, which reduces the concentration of sodium ions in the effluent from the source and is beneficial to improving the quality of the effluent.

[0024] This application improves the physical stability and controllability of the treatment agent by pretreating the red mud with acid washing and adding an inert carrier, thus buffering the acid-base reaction. Detailed Implementation

[0025] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. This application can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application.

[0026] Furthermore, it should be understood that the one or more method steps mentioned in this application do not preclude the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps, unless otherwise stated. Moreover, unless otherwise stated, the numbering of each method step is merely a convenient tool for identifying each method step, and is not intended to limit the order of the method steps or limit the scope of implementation of this application. Changes or adjustments to their relative relationships, without substantially altering the technical content, shall also be considered as within the scope of implementation of this application.

[0027] Unless otherwise specified, the experimental conditions used in the examples are generally in accordance with conventional conditions in the art or the conditions recommended by the reagent company. Unless otherwise specified, the materials and reagents used in the examples can be purchased commercially.

[0028] The red mud used in the following examples and comparative examples was selected from an alumina plant, passed through a 100-mesh sieve, and its main chemical components were: SiO2 7.6%, Al2O3 19.5%, CaO 19.5%, Fe2O3 22.3%, and Na2O 4.6%.

[0029] Humic acid and sodium humate were purchased from Beijing Bio-Lab Technology Co., Ltd. 1g of humic acid was dissolved in 10mL of deionized water and the pH value was measured to be 4.12 after shaking.

[0030] Diatomaceous earth and kaolin were purchased from Hebei Maikemaini Mineral Products Co., Ltd. and passed through a 100-mesh sieve; attapulgite was purchased from Hebei Chidi Mineral Products Co., Ltd. and passed through a 100-mesh sieve.

[0031] Example 1: Preparation of an acidic mine water treatment agent based on red mud Take 100g of dried red mud and add it to 500mL of 0.2mol / L dilute hydrochloric acid solution. Stir the mixture at 200rpm for 45min at 45℃. Then wash it three times with deionized water and dry it to obtain pretreated red mud.

[0032] Add 20g of diatomaceous earth to 40mL of water and stir to form a slurry. Weigh 10g of humic acid and add it to the slurry. Stir and react for 2 hours. After drying, the composite powder is obtained.

[0033] The pretreated red mud and composite powder obtained above are mixed evenly to obtain the treatment agent.

[0034] Example 2: Preparation of an acidic mine water treatment agent based on red mud Take 100g of dried red mud and add it to 500mL of 0.2mol / L dilute hydrochloric acid solution. Stir the mixture at 200rpm for 45min at 45℃. Then wash it three times with deionized water and dry it to obtain pretreated red mud.

[0035] Add 5g of diatomaceous earth to 10mL of water and stir to form a slurry. Weigh 1g of humic acid and add it to the slurry. Stir and react for 2 hours. After drying, the composite powder is obtained.

[0036] The pretreated red mud and composite powder obtained above are mixed evenly to obtain the treatment agent.

[0037] Example 3: Preparation of an acidic mine water treatment agent based on red mud Take 100g of dried red mud and add it to 500mL of 0.2mol / L dilute hydrochloric acid solution. Stir the mixture at 200rpm for 45min at 45℃. Then wash it three times with deionized water and dry it to obtain pretreated red mud.

[0038] Add 10g of diatomaceous earth to 20mL of water and stir to form a slurry. Weigh 5g of humic acid and add it to the slurry. Stir and react for 2 hours. After drying, the composite powder is obtained.

[0039] The pretreated red mud and composite powder obtained above are mixed evenly to obtain the treatment agent.

[0040] Example 4: Preparation of an acidic mine water treatment agent based on red mud Take 100g of dried red mud and add it to 500mL of 0.2mol / L dilute hydrochloric acid solution. Stir the mixture at 200rpm for 45min at 45℃. Then wash it three times with deionized water and dry it to obtain pretreated red mud.

[0041] Add 20g of kaolin to 40mL of water and stir to form a slurry. Weigh 10g of humic acid and add it to the slurry. Stir and react for 2 hours. After drying, the composite powder is obtained.

[0042] The pretreated red mud and composite powder obtained above are mixed evenly to obtain the treatment agent.

[0043] Example 5: Preparation of an acidic mine water treatment agent based on red mud Take 100g of dried red mud and add it to 500mL of 0.2mol / L dilute hydrochloric acid solution. Stir the mixture at 200rpm for 45min at 45℃. Then wash it three times with deionized water and dry it to obtain pretreated red mud.

[0044] Add 20g of attapulgite to 40mL of water and stir to form a slurry. Weigh 10g of humic acid and add it to the slurry. Stir and react for 2 hours. After drying, the composite powder is obtained.

[0045] The pretreated red mud and composite powder obtained above are mixed evenly to obtain the treatment agent.

[0046] Example 6: Preparation of an acidic mine water treatment agent based on red mud Take 100g of dried red mud and add it to 500mL of 0.2mol / L dilute hydrochloric acid solution. Stir the mixture at 200rpm for 45min at 45℃. Then wash it three times with deionized water and dry it to obtain pretreated red mud.

[0047] Add 20g of diatomaceous earth to 40mL of water and stir to form a slurry. Weigh 10g of humic acid and add it to the slurry. Stir and react for 2 hours. After drying, the composite powder is obtained.

[0048] Mix the pretreated red mud and composite powder obtained above, add 5g of polyacrylamide, and mix evenly to obtain the treatment agent.

[0049] Comparative Example 1: Preparation of an acidic mine water treatment agent based on red mud Take 100g of dried red mud and add it to 500mL of 0.2mol / L dilute hydrochloric acid solution. Stir the mixture at 200rpm for 45min at 45℃. Then wash it three times with deionized water and dry it to obtain pretreated red mud.

[0050] Add 20g of diatomaceous earth to 40mL of water and stir to form a slurry. Weigh 10g of sodium humate and add it to the slurry. Stir and react for 2 hours. After drying, the composite powder is obtained.

[0051] The pretreated red mud and composite powder obtained above are mixed evenly to obtain the treatment agent.

[0052] The difference from Example 1 is that sodium humate is used instead of humic acid in this comparative example.

[0053] Comparative Example 2: Preparation of an acidic mine water treatment agent based on red mud Take 100g of dried red mud, add it to 500mL of deionized water, stir at 200rpm for 45min at 45℃, then wash it three times with deionized water and dry it to obtain pretreated red mud.

[0054] Add 20g of diatomaceous earth to 40mL of water and stir to form a slurry. Weigh 10g of humic acid and add it to the slurry. Stir and react for 2 hours. After drying, the composite powder is obtained.

[0055] The pretreated red mud and composite powder obtained above are mixed evenly to obtain the treatment agent.

[0056] The difference from Example 1 is that this comparative example uses water washing instead of acid washing to pretreat the red mud.

[0057] Comparative Example 3: Preparation of an acidic mine water treatment agent based on red mud Take 100g of dried red mud and add it to 500mL of 0.2mol / L dilute hydrochloric acid solution. Stir the mixture at 200rpm for 45min at 45℃. Then wash it three times with deionized water and dry it to obtain pretreated red mud.

[0058] Mix the pretreated red mud obtained above with 10g of humic acid evenly to obtain the treatment agent.

[0059] The difference from Example 1 is that no inert carrier was added to this comparative treatment agent.

[0060] Example 7: Treatment method for acidic mine water with high metal ion content Preparation of acidic mine water: A solution was prepared using ferrous sulfate heptahydrate and manganese sulfate, and the pH was adjusted with sulfuric acid to obtain simulated acidic mine water with an iron ion concentration of 800 mg / L, a manganese ion concentration of 15 mg / L, and a pH of 2.5.

[0061] Processing steps: Take 10g of each of the treatment agents prepared in Examples 1-6 and Comparative Examples 1-3, add them to a 500mL conical flask, add 200mL of simulated acidic mineral water, and react in a constant temperature shaker at 25℃ at 100rpm for 4h. After the reaction is complete, precipitate for 2h, and separate the solid and liquid to obtain the treated effluent and sludge.

[0062] Results determination: Fe in the water was determined using inductively coupled plasma optical emission spectrometry (ICP-OES). 2+ Mn 2 + Na + The mass concentration of suspended solids in the water was determined using a Malvern laser particle size analyzer. The results are recorded in Table 1.

[0063] Table 1. Mass concentrations of metal ions and suspended solids in the effluent after simulated mine inrush water treatment. Table 1 shows the treatment results of high-concentration simulated acidic mine water. It can be seen that: Na in the effluent + Regarding concentration, Examples 1-6, which used a mixture of humic acid and red mud, showed that the effluent Na... + The sodium concentration was significantly lower than in Comparative Example 1, which used sodium humate, because the introduction of sodium ions was avoided at the source. Furthermore, Example 1 underwent red mud acid washing pretreatment, which, compared to the water washing pretreatment in Comparative Example 2, more effectively suppressed the dissolution of sodium from the red mud itself. Comparing Example 1 and Comparative Example 3, it can be seen that without the addition of an inert carrier, the sodium ion concentration in the effluent increased, presumably because the direct contact reaction between the red mud and humic acid was more vigorous, leading to the precipitation of more sodium ions.

[0064] Regarding the heavy metal removal effect, Examples 1-6 showed that Fe... 2+ and Mn 2+ The removal rates remained at a high level, and the Fe in the effluent was... 2+ When the concentration is below 51.3 mg / L, Mn 2+ Concentrations below 2.0 mg / L, especially in Example 6, showed that after the addition of a flocculant, Fe... 2 + and Mn 2+ The removal effect is optimal.

[0065] Regarding settling performance, by introducing inert carriers such as diatomaceous earth and kaolin, Examples 1-5 formed flocs that were easy to settle, with the effluent suspended solids concentration controlled at 12-25 mg / L. Example 6, after further adding a flocculant, reduced the suspended solids to 6 mg / L. In contrast, Comparative Example 3 (48 mg / L) without the flocculant and Comparative Example 1 (88 mg / L) using sodium humate produced more turbid effluent and made solid-liquid separation more difficult.

[0066] In summary, this invention, through the synergistic effect of acid washing pretreatment of red mud, the use of humic acid to replace sodium humate, and the combination of inert carriers, effectively controls the salinity of effluent while ensuring efficient neutralization and heavy metal adsorption, and significantly improves the settling performance of sludge, thus achieving a highly efficient and stable "waste-to-waste" process.

[0067] Example 8: Treatment method for acidic mine water with low metal ion content Preparation of acidic mine water: A solution was prepared using ferrous sulfate heptahydrate and manganese sulfate, and the pH was adjusted with sulfuric acid to obtain simulated acidic mine water with an iron ion concentration of 100 mg / L, a manganese ion concentration of 5 mg / L, and a pH of 5.6.

[0068] Processing steps: Take 2g of each of the treatment agents prepared in Examples 1-6 and Comparative Examples 1-3, add them to a 500mL conical flask, add 200mL of simulated acidic mineral water, and react in a constant temperature shaker at 25℃ at 100rpm for 4h. After the reaction is complete, precipitate for 2h, and separate the solid and liquid to obtain the treated effluent and sludge.

[0069] Results determination: Fe in the water was determined using inductively coupled plasma optical emission spectrometry (ICP-OES). 2+ Mn 2 + Na + The mass concentration of suspended solids in the water was determined using a Malvern laser particle size analyzer. The results are recorded in Table 2.

[0070] Table 2. Mass concentrations of metal ions and suspended solids in the effluent after simulated mine inrush water treatment. Table 2 shows the treatment results of low-concentration simulated acidic mine water. It can be seen that: At a low dosage of 2g / 200mL, the treatment agent of this application achieved deeper purification of low concentrations of heavy metals, with the effluent Fe... 2+ Mn 2+ The concentrations were extremely low, below 0.8 mg / L and 0.08 mg / L, respectively. Meanwhile, the effluent Na... +The concentration was further reduced to below 38.5 mg / L, far lower than the 103.1 mg / L of Comparative Example 1, demonstrating its excellent salinity control capability in low-dosage scenarios.

[0071] Due to the low turbidity of the raw water and the small amount of reagent added, the suspended solids concentration in all test groups decreased significantly. The suspended solids concentration in the effluent of each embodiment of this application was reduced to below 5 mg / L, and in Example 6 it even reached a level close to transparency (<1 mg / L), which once again verified the effectiveness of its formula in promoting flocculation and sedimentation.

[0072] The results in Table 2 show that the treatment agent of the present invention is not only suitable for high-concentration, strongly acidic extreme mine water, but also highly effective for medium- and low-concentration, weakly acidic mine water. By reducing the dosage, the discharge can meet the standards, which significantly reduces the treatment cost and broadens the application scope.

[0073] The above description is merely a preferred embodiment of this application and is not intended to limit this application in any form or substance. It should be noted that those skilled in the art can make various improvements and additions without departing from the method of this application, and these improvements and additions should also be considered within the scope of protection of this application. Any modifications, alterations, and equivalent variations made by those skilled in the art based on the disclosed technical content without departing from the spirit and scope of this application are equivalent embodiments of this application. Furthermore, any modifications, alterations, and variations made to the above embodiments based on the essential technology of this application still fall within the scope of the technical solution of this application.

Claims

1. An acidic mine water treatment agent based on red mud, characterized in that, The raw materials include the following parts by weight: 100 parts of red mud pretreated by acid washing, 1-10 parts of humic acid, and 5-20 parts of inert carrier.

2. The treatment agent according to claim 1, characterized in that, The pretreated red mud is obtained by the following steps: mixing red mud and pickling solution at a solid-liquid ratio of 1g / (5-10)mL, and continuously mechanically stirring at a speed of 100-200rpm for 0.5-1.5h at a temperature of 25-50℃. After the reaction is completed, the mixture is filtered to separate the solids, and then washed with water and dried to obtain the final product.

3. The treatment agent according to claim 2, characterized in that, The pickling solution is an aqueous solution of hydrochloric acid or sulfuric acid.

4. The treatment agent according to claim 3, characterized in that, The concentration of the pickling solution is 0.05-0.5 mol / L.

5. The treatment agent according to claim 1, characterized in that, The inert carrier is at least one of diatomaceous earth, kaolin, and attapulgite.

6. The treatment agent according to claim 1, characterized in that, The raw material also includes one or more functional components, which are selected from at least one of chemical precipitants, redox agents, flocculants, and structure modifiers. The chemical precipitant is at least one of phosphate rock powder, magnesium phosphate rock powder, or ferrous sulfide. The redox agent is at least one of zero-valent iron or persulfate. The flocculant is at least one of polymeric metal silicate, chitosan, and polyacrylamide. The structure modifier is at least one of porous ceramic microspheres or biochar.

7. A method for preparing an acidic mine water treatment agent based on red mud as described in any one of claims 1-6, characterized in that, Includes the following steps: The red mud was pretreated by acid washing, followed by water washing and drying to obtain pretreated red mud. An inert carrier is added to water to form a slurry, humic acid is added, the mixture is stirred evenly, and then dried to obtain a composite powder. The pretreated red mud, composite powder, and functional components are uniformly mixed to obtain the treatment agent.

8. A method of using the red mud-based acidic mine water treatment agent according to any one of claims 1-6, characterized in that, Includes the following steps: The treatment agent is added to acidic mineral water and stirred for a period of time. After the reaction is completed, solid-liquid separation is performed to obtain treated effluent and stabilized sludge.

9. The method of using the treatment agent according to claim 8, characterized in that, The dosage of the treatment agent is 5-200 g / L, based on the volume of acidic mineral water.

10. The method of using the treatment agent according to claim 8, characterized in that, The stirring reaction time is 1-8 hours.

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