Treatment method of aluminum oxidation wastewater slag

Abstract

The invention relates to the technical field of industrial wastewater treatment, and discloses an aluminum oxidation wastewater slag treatment method which comprises the following steps: S1, pretreatment and solid-liquid separation: carrying out sedimentation and filter pressing treatment on aluminum oxidation wastewater slag to separate solid waste slag and liquid wastewater, and adjusting the pH value of the waste slag; s2, preparing an adsorption material and removing heavy metals: preparing a composite adsorption material from chitosan and nano iron oxide, and adding the adsorption material into the waste residues to remove the heavy metals; s3, aluminum oxide extraction and recovery: aluminum oxide in the waste residues is extracted through an acid dissolution method, and aluminum ions are precipitated and calcined to recover aluminum oxide. The low-cost chitosan / nano iron oxide composite adsorption material is used for effectively removing heavy metals in wastewater residues, so that the risk of environmental pollution is reduced. The aluminum oxide is recycled through the steps of acid dissolution, precipitation, calcination and the like, resource utilization is achieved, and economic benefits are improved. Meanwhile, the wastewater is recycled after being treated, so that water resources are saved, and the discharge amount is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of industrial wastewater treatment, and in particular to a method for treating aluminum oxidation wastewater slag. Background Art

[0002] Aluminum oxidation process is widely used in the field of surface treatment of aluminum products. The oxidation process can significantly improve the corrosion resistance and decorative properties of aluminum products. However, a large amount of wastewater slag is produced during the aluminum oxidation process. The wastewater slag contains high concentrations of aluminum oxide, heavy metals (such as lead, cadmium, chromium, etc.), alkaline substances and organic pollutants. Direct discharge of such wastewater slag not only causes serious pollution to the soil and water bodies, but also poses potential health risks. Therefore, the harmless treatment and resource utilization of aluminum oxidation wastewater slag has become an urgent problem to be solved.

[0003] Traditional wastewater slag treatment methods usually include chemical precipitation, heavy metal passivation, acid-base neutralization and other steps. Although these methods can reduce the concentration of pollutants to a certain extent, they have the problems of high treatment costs and unsatisfactory treatment effects. In addition, most of these methods only focus on removing heavy metals and harmful substances, making it difficult to achieve effective recovery of alumina, resulting in waste of resources. Some wastewater slag treatment processes also introduce a large amount of chemical agents, increasing the risk of secondary pollution during the treatment process, which is not conducive to long-term environmental protection and sustainable development of enterprises.

[0004] In recent years, with the development of green chemistry and resource recycling technology, more and more research has focused on using low-cost adsorbent materials, modified biomaterials and nanomaterials to improve the efficiency of wastewater slag treatment. For example, chitosan and nano-iron oxide are widely used in the removal of heavy metals due to their good adsorption properties and environmental friendliness. However, it is difficult for a single adsorbent to balance the treatment effect and cost. Especially in large-scale applications, how to achieve efficient and low-cost heavy metal removal and aluminum oxide resource recovery remains a technical difficulty. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention provides a method for treating aluminum oxidation wastewater slag, which solves the problems in the prior art of high treatment cost of aluminum oxidation wastewater slag, low heavy metal removal efficiency, difficulty in effectively recovering aluminum oxide and easy to cause secondary pollution.

[0006] To achieve the above objectives, the present invention is implemented through the following technical scheme: A method for treating aluminum oxidation wastewater slag, comprising the following steps:

[0007] S1. Pretreatment and solid-liquid separation: The aluminum oxidation wastewater slag is subjected to sedimentation and filter pressing treatment to separate the solid waste slag and liquid wastewater, and the pH value of the waste slag is adjusted;

[0008] S2. Preparation of adsorption materials and removal of heavy metals: A composite adsorption material was prepared using chitosan and nano-iron oxide, and the adsorption material was added to the waste residue to remove heavy metals;

[0009] S3. Alumina extraction and recovery: Alumina is extracted from the waste residue by acid dissolution, and aluminum ions are precipitated and calcined to recover alumina;

[0010] S4. Solidification and stabilization of waste residue: Use curing agent and stabilizer to solidify and stabilize the treated waste residue to reduce the risk of heavy metal leaching;

[0011] S5. Wastewater recycling and standard-compliant discharge: The wastewater generated during the treatment process is subjected to flocculation, sedimentation and separation treatment to achieve recycling or standard-compliant discharge.

[0012] Preferably, the pretreatment and solid-liquid separation steps include:

[0013] S11. The aluminum oxidation wastewater slag was allowed to stand for 24 hours to allow the solid particles to settle;

[0014] S12. Dehydrating the waste residue after sedimentation by a filter press to further reduce the moisture content of the waste residue;

[0015] S13. Using a dilute acid solution to neutralize the waste residue, adjusting the pH value of the waste residue to 6.5 to 7.5.

[0016] Preferably, the adsorption material preparation and heavy metal removal steps include:

[0017] S21. extracting chitosan and performing deacetylation treatment to increase the amino content;

[0018] S22. Nano-iron oxide was synthesized by coprecipitation method, mixed with chitosan, and cross-linked into a composite adsorption material using a cross-linking agent;

[0019] S23. Add the composite adsorption material to the waste residue for heavy metal adsorption treatment, and remove the heavy metals in the waste residue by stirring, mixing, and solid-liquid separation.

[0020] Preferably, the dosage of the composite adsorption material in the heavy metal adsorption step is 0.5 g / L to 2.0 g / L, the reaction time is 30 minutes to 60 minutes, and the adsorption conditions include a pH value of 6.0 to 7.0, a temperature of 20°C to 30°C, and a stirring speed of 200 rpm.

[0021] Preferably, the alumina extraction and recovery step comprises:

[0022] S31. Acid dissolving the waste residue using a 20% sulfuric acid solution at 80°C to extract alumina;

[0023] S32. The pH value of the aluminum-containing solution is adjusted to 5.5 to 6.0, and aluminum hydroxide is generated by precipitation;

[0024] S33. Calcine aluminum hydroxide to generate aluminum oxide.

[0025] Preferably, the solidification and stabilization treatment steps of the waste residue include:

[0026] S41. Mix the waste residue with cement in a mass ratio of 4:1, add water and stir until formed;

[0027] S42. Phosphate is added as a heavy metal stabilizer during the solidification process to generate insoluble heavy metal phosphate precipitates to reduce the leaching toxicity of heavy metals;

[0028] S43. The formed solid body is cured at room temperature for 28 days.

[0029] Preferably, the added amount of the phosphate stabilizer is 1% to 5% of the mass of the waste residue, preferably 2% of the mass of the waste residue.

[0030] Preferably, the wastewater recycling and standard-compliant discharge steps include:

[0031] S51. Adjust the pH value of the wastewater to neutral, add polyaluminium chloride and polyacrylamide as flocculants and coagulants, and perform precipitation treatment;

[0032] S52. The supernatant after precipitation is used as washing water in the pretreatment stage, and the wastewater that is not recycled is discharged after being tested and found to meet the emission standards.

[0033] Preferably, the dosage of polyaluminium chloride is 50 mg / L to 150 mg / L, the dosage of polyacrylamide is 0.5 mg / L to 2 mg / L, and the flocculation sedimentation time is 1 hour to 2 hours.

[0034] Preferably, the regeneration step of the adsorbent material after use comprises:

[0035] a. Desorption was performed using a 0.1 mol / L hydrochloric acid solution to recover the heavy metals in the adsorbent material;

[0036] b. Wash the desorbed adsorbent material with deionized water until it is neutral and dry it for recycling.

[0037] The present invention provides a method for treating aluminum oxidation wastewater slag, which has the following beneficial effects:

[0038] 1. The present invention uses chitosan / nano iron oxide composite adsorption material to efficiently remove heavy metal ions in aluminum oxidation wastewater residue. The composite material has a high specific surface area and active functional groups, can significantly reduce the heavy metal residues in the wastewater residue, and avoids the potential pollution of heavy metals to the environment. The treated waste residue meets the environmental emission standards, reduces the risk of pollution to the surrounding water and soil, and has a high environmental value.

[0039] 2. The present invention extracts aluminum oxide from wastewater slag and recycles it for reuse through processes such as acid dissolution, precipitation, and calcination. This resource recovery step effectively reduces the content of aluminum oxide in the waste slag, allowing aluminum oxide to be recycled and converted into renewable resources, which not only reduces the cost of waste treatment, but also increases the economic benefits of the enterprise, providing a feasible way for the efficient use of resources.

[0040] 3. The present invention extracts aluminum oxide from wastewater slag and recycles it for reuse through processes such as acid dissolution, precipitation, and calcination. This resource recovery step effectively reduces the content of aluminum oxide in the waste slag, allowing aluminum oxide to be recycled and converted into renewable resources, which not only reduces the cost of waste treatment, but also increases the economic benefits of the enterprise, providing a feasible way for the efficient use of resources.

[0041] 4. The present invention passivates the heavy metals in the waste residue into insoluble precipitates through cement solidification and phosphate stabilization treatment, thereby reducing the leaching toxicity of heavy metals. The treated waste residue has good stability and can be safely landfilled or reused, meeting long-term environmental safety requirements, reducing the potential harm of waste residue to the ecosystem, and providing reliable guarantee for the harmless disposal of wastewater residue. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a schematic flow chart of the steps of the method for treating aluminum oxidation wastewater slag in the present invention. DETAILED DESCRIPTION

[0043] The following will be combined with the drawings in the specification of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] Example:

[0045] Please refer to the attached Figure 1The embodiment of the present invention provides a method for treating aluminum oxidation wastewater slag, which aims to effectively remove heavy metals in the wastewater slag, realize resource recovery of aluminum oxide, and make the waste slag reach harmless standards. The treatment method of the present invention removes and recovers harmful components and valuable components in aluminum oxidation wastewater slag through a multi-step, integrated process, and includes the following steps:

[0046] S1. Pretreatment and solid-liquid separation: The aluminum oxidation wastewater slag is subjected to sedimentation and filter pressing treatment to separate the solid waste slag and liquid wastewater, and the pH value of the waste slag is adjusted;

[0047] S11. Solid-liquid separation:

[0048] In the treatment of aluminum oxidation wastewater slag, the wastewater slag usually has high water content and strong alkalinity. In order to reduce the volume and cost of subsequent treatment, the present invention first separates the wastewater slag into solid and liquid. The aluminum oxidation wastewater slag is placed in a sedimentation tank for 24 hours to allow the solid particles to settle naturally, and a portion of the supernatant is separated. Then, the settled wastewater slag is sent to a filter press for mechanical dehydration to reduce the moisture content from 70%-80% to less than 50%, so as to reduce the consumption of reagents and the difficulty of treatment in subsequent steps.

[0049] S12.pH neutralization adjustment:

[0050] After the initial solid-liquid separation, the waste residue still contains strong alkaline components. In order to reduce the alkalinity and optimize the effect of the subsequent adsorption step, the waste residue is neutralized and adjusted with a 10% dilute hydrochloric acid solution to adjust the pH value to a neutral range of 6.5 to 7.5. During the neutralization process, the dilute hydrochloric acid reacts with the alkaline substances in the waste residue to generate water, reducing the corrosiveness. According to the amount of acid required for the neutralization reaction, the required acid volume is calculated according to the following formula:

[0051]

[0052] Among them, C base is the concentration of alkaline substances in the waste residue, V base is the volume of waste residue, C acid is the concentration of hydrochloric acid, V acid is the volume of hydrochloric acid. By stirring evenly, the acid and alkaline substances are fully reacted to ensure that the pH of the waste residue reaches the preset range.

[0053] S2. Preparation of adsorption materials and removal of heavy metals: A composite adsorption material was prepared using chitosan and nano-iron oxide, and the adsorption material was added to the waste residue to remove heavy metals;

[0054] For the preparation of adsorption materials and heavy metal removal steps, chitosan and nano-iron oxide composite materials are used as low-cost adsorption materials to achieve efficient removal of heavy metals in aluminum oxidation wastewater slag. Chitosan is modified by deacetylation to improve its adsorption capacity for heavy metal ions, and nano-iron oxide particles are prepared by co-precipitation. The two are combined to form a composite adsorption material with a larger specific surface area and active adsorption sites, thereby improving the adsorption effect. During the adsorption process, the pH value, temperature, stirring speed and other conditions are optimized to ensure efficient adsorption of heavy metals in wastewater slag by the composite adsorption material. The treated adsorbent is regenerated by acid washing and can be recycled for further heavy metal removal operations. The specific steps are as follows:

[0055] S21. Preparation of adsorption material:

[0056] The preparation steps of the chitosan and nano-iron oxide composite material are as follows:

[0057] 1. Chitosan extraction and modification:

[0058] Chitosan is extracted from discarded shrimp and crab shells, dissolved in a dilute hydrochloric acid solution, and dissolved by stirring to obtain a chitosan solution rich in amino content.

[0059] The dissolved chitosan was neutralized to pH 9 by adding sodium hydroxide solution, and the amino content was further increased by deacetylation to enhance its affinity for heavy metal ions.

[0060] The treated chitosan is repeatedly washed with deionized water until it becomes neutral and dried for later use to ensure its activity in the composite material.

[0061] 2. Synthesis of Nano-Iron Oxide:

[0062] Nano-iron oxide particles were prepared by coprecipitation. 3+ and Fe 2+ Dissolve in deionized water at a molar ratio of 2:1 to form a uniform mixed solution.

[0063] Under stirring conditions, slowly add 1 mol / L NaOH solution and maintain the pH value of the solution at about 10 to allow the iron ions to react with the hydroxide ions to generate nano-iron oxide (Fe3O4) particles. The reaction formula is as follows:

[0064] 2Fe 3+ +Fe 2+ +8OH - →Fe3O4+4H2O

[0065] The generated nano iron oxide particles are separated from the solution by a magnetic separation device, and are repeatedly washed with deionized water until they become neutral to remove residual reactants, and then the washed nano iron oxide is dried for later use.

[0066] 3. Synthesis of composite materials:

[0067] The dried chitosan was dissolved in a 2% acetic acid solution, and nano-iron oxide particles were added thereto, and ultrasonic dispersion was performed to ensure that the nano-iron oxide was evenly distributed in the chitosan solution.

[0068] Then, a cross-linking agent glutaraldehyde was added, and the cross-linking reaction time was controlled to be 2 hours, so that the chitosan and the nano-iron oxide particles were combined with each other to form a chitosan / nano-iron oxide composite material with a stable structure.

[0069] The cross-linked composite material is dried and set aside for use in the subsequent heavy metal removal step.

[0070] S22. Heavy metal removal steps:

[0071] The prepared chitosan / nano iron oxide composite material was applied to the removal of heavy metals in aluminum oxidation wastewater slag. The specific steps are as follows:

[0072] 1. Heavy metal adsorption process:

[0073] The composite adsorbent material is added to the pretreated waste slurry at a dosage of 0.5 g / L to 2.0 g / L, and the stirring speed is controlled to 200 rpm to ensure that the adsorbent is fully in contact with the heavy metals in the waste slag.

[0074] The pH value of the waste residue slurry was adjusted to a neutral range of 6.0 to 7.0, the temperature was maintained at 25°C, and the adsorption was stirred for 60 minutes to optimize the adsorption efficiency.

[0075] 2. Calculation of adsorption capacity:

[0076] During the adsorption process, the heavy metal adsorption capacity q at adsorption equilibrium is calculated using the following formula: e :

[0077]

[0078] in:

[0079] C0 is the initial concentration of heavy metal ions at the beginning of adsorption (mg / L).

[0080] C e is the heavy metal ion concentration at adsorption equilibrium (mg / L).

[0081] V is the volume of waste slurry (L).

[0082] m is the mass of the composite adsorbent material (g).

[0083] The q calculated by the above formula e The values ​​can be used to evaluate the adsorption performance of composite materials for heavy metals and provide data support for the optimization of adsorption conditions.

[0084] S23. Regeneration and recycling of adsorbent:

[0085] The adsorbent after adsorption saturation is regenerated by acid washing to remove the adsorbed heavy metals. The saturated adsorbent is placed in a 0.1 mol / L hydrochloric acid solution and stirred for 1 hour to desorb the heavy metal ions from the adsorbent material.

[0086] The desorbed adsorbent is washed with deionized water until it becomes neutral to remove residual acid and heavy metal ions, and then dried again for use.

[0087] The regenerated adsorbent is reused for subsequent heavy metal removal processes, thereby effectively reducing the use cost of the adsorbent and improving the economic benefits of the method.

[0088] Through the specific implementation of the above steps, the chitosan / nano iron oxide composite adsorption material can effectively remove heavy metals in aluminum oxidation wastewater slag and improve the harmless treatment effect of the waste slag.

[0089] S3. Alumina extraction and recovery: Alumina is extracted from the waste residue by acid dissolution, and aluminum ions are precipitated and calcined to recover alumina;

[0090] S31. Acid dissolution to extract alumina:

[0091] The waste residue contains a high concentration of aluminum oxide (Al2O3), which is extracted by acid dissolution. The waste residue is mixed with a 20% sulfuric acid solution at a solid-liquid ratio of 1:5, heated to 80°C and stirred for 2 hours to dissolve the aluminum oxide in the acid solution. The reaction is as follows:

[0092]

[0093] S32. Precipitation and recovery of aluminum:

[0094] The pH value of the acid solution is adjusted to 5.5 to 6.0, so that the aluminum ions react with the hydroxide ions to form aluminum hydroxide precipitation. The reaction is as follows:

[0095] Al 3+ +3OH - →Al(OH)3↓

[0096] The aluminum hydroxide precipitate is separated by filtration, washed with deionized water and then calcined. The calcination condition is 800℃ and calcined for 2 hours to generate aluminum oxide, realizing resource recovery:

[0097]

[0098] S4. Solidification and stabilization of waste residue: Use curing agent and stabilizer to solidify and stabilize the treated waste residue to reduce the risk of heavy metal leaching;

[0099] Solidification treatment of waste residues For the extraction and recovery steps of alumina, the present invention extracts alumina from aluminum oxidation wastewater residues by acid dissolution, and precipitates and calcines the extracted aluminum ions to recover alumina, thereby realizing resource utilization. This step includes acid dissolution, aluminum precipitation, calcination and other links to ensure efficient recovery of alumina. This method improves the extraction rate of alumina by optimizing the acid dissolution conditions and precipitation conditions, forms reusable alumina, further reduces the disposal amount of wastewater residues, and improves resource utilization.

[0100] The extraction and recovery steps of alumina include the following operations:

[0101] S41. Acid dissolution to extract alumina:

[0102] Use sulfuric acid solution to dissolve the aluminum oxide in the wastewater slag. Mix the wastewater slag with 20% (mass fraction) sulfuric acid solution at a solid-liquid ratio of 1:5, place it in an acid-resistant reaction container, and heat and stir at 80°C for 2 hours to increase the dissolution rate of aluminum oxide. During the reaction, aluminum oxide reacts chemically with sulfuric acid to generate aluminum ions. The reaction formula is as follows:

[0103]

[0104] To ensure sufficient dissolution, the reaction temperature was controlled at 80°C and stirring was continued during the reaction to ensure that the sulfuric acid could evenly contact the alumina in the wastewater slag.

[0105] 2. Filtrate separation and aluminum dissolution rate calculation:

[0106] After the acid dissolution reaction is completed, a hot filtration separation operation is immediately performed to separate the acid solution containing aluminum ions from the acid-insoluble residue to improve the aluminum recovery efficiency.

[0107] Aluminum dissolution rate R Al It can be calculated by the following formula:

[0108]

[0109] in:

[0110] is the mass of aluminum dissolved in the solution;

[0111] is the initial aluminum mass in the wastewater slag.

[0112] 3. Precipitation of aluminum:

[0113] By controlling the pH value of the acid solution, the aluminum ions in the solution are precipitated into aluminum hydroxide. The pH of the acid solution is adjusted to 5.5 to 6.0, and ammonia water is gradually added as a precipitant to react the aluminum ions with the hydroxide ions to generate aluminum hydroxide precipitate. The reaction is as follows:

[0114] Al 3+ +3OH - →Al(OH)3↓

[0115] The precipitation process requires slow stirring to maintain a uniform solution and avoid local oversaturation and agglomeration. After precipitation, the aluminum hydroxide precipitate is collected by filtration and washed with deionized water until neutral to remove residual sulfate ions.

[0116] 4. Calcination of aluminum hydroxide to obtain aluminum oxide:

[0117] After the aluminum hydroxide obtained by precipitation is dried, it is sent to a high-temperature calcining furnace and calcined at 800°C for 2 hours to dehydrate and decompose the aluminum hydroxide to generate aluminum oxide. The reaction is as follows:

[0118]

[0119] During the calcination process, a constant temperature is maintained to completely decompose aluminum hydroxide to obtain pure aluminum oxide powder, avoiding agglomeration that affects product quality.

[0120] 5. Calculation of alumina recovery rate:

[0121] The recovery rate of alumina is calculated by the following formula:

[0122]

[0123] in:

[0124] is the mass of alumina recovered after calcination;

[0125] is the initial alumina mass in the wastewater slag.

[0126] Through the specific implementation of the above steps, alumina can be extracted and recovered from the wastewater slag, reducing the content of alumina in the waste slag and realizing the secondary utilization of resources.

[0127] In order to further reduce the risk of heavy metal leaching from waste residue, cement is used as a curing agent. Waste residue and cement are mixed in a mass ratio of 4:1, and appropriate amount of water is added and stirred evenly to form a mixture, which is then poured into a mold for molding. The formed solid body is cured at room temperature for 28 days to complete the hydration reaction of the cement matrix, solidify the heavy metals inside the matrix, and improve the stability of the solid body.

[0128] S42. Heavy metal stabilization treatment:

[0129] Phosphate stabilizers are added during the mixing process to passivate heavy metals into insoluble heavy metal phosphate precipitates, reducing their leaching toxicity. Taking lead as an example, heavy metal ions react with phosphate ions to generate heavy metal phosphates, and the reaction is as follows:

[0130]

[0131] The amount of phosphate stabilizer added is 2% of the mass of the waste residue to ensure the long-term stability of the waste residue.

[0132] S5. Wastewater recycling and standard-compliant discharge: The wastewater generated during the treatment process is subjected to flocculation, sedimentation and separation treatment to achieve recycling or standard-compliant discharge.

[0133] S51. Wastewater treatment:

[0134] The wastewater generated during the treatment process is treated by pH adjustment and flocculation and sedimentation to remove suspended matter and residual heavy metals. Polyaluminium chloride and polyacrylamide are added as flocculants and coagulants to precipitate suspended matter and colloidal impurities, and the dosage is controlled to be 100mg / L and 1mg / L respectively.

[0135] S52. Wastewater recycling:

[0136] The treated supernatant meets the clean water standards and can be recycled for the cleaning process in the pretreatment stage, reducing the consumption of water resources.

[0137] S53. Wastewater discharge meets the standards:

[0138] If there is any remaining wastewater that needs to be discharged, its heavy metal concentration, chemical oxygen demand (COD) and other indicators must be tested to ensure that they meet the requirements of the "Comprehensive Sewage Discharge Standard" (GB8978-1996) before it can be discharged to ensure that no secondary pollution is caused to the environment.

[0139] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for treating aluminum oxidation wastewater slag, characterized in that: The following steps are involved: S1. Pretreatment and solid-liquid separation: The aluminum oxidation wastewater slag is subjected to sedimentation and filter pressing treatment to separate the solid waste slag and liquid wastewater, and the pH value of the waste slag is adjusted; S2. Preparation of adsorption materials and removal of heavy metals: A composite adsorption material was prepared using chitosan and nano-iron oxide, and the adsorption material was added to the waste residue to remove heavy metals; S3. Alumina extraction and recovery: Alumina is extracted from the waste residue by acid dissolution, and aluminum ions are precipitated and calcined to recover alumina; S4. Solidification and stabilization of waste residue: Use curing agent and stabilizer to solidify and stabilize the treated waste residue to reduce the risk of heavy metal leaching; S5. Wastewater recycling and standard-compliant discharge: The wastewater generated during the treatment process is subjected to flocculation, sedimentation and separation treatment to achieve recycling or standard-compliant discharge.

2. The method for treating aluminum oxidation wastewater slag according to claim 1, characterized in that: The pretreatment and solid-liquid separation steps include: S11. The aluminum oxidation wastewater slag was allowed to stand for 24 hours to allow the solid particles to settle; S12. Dehydrating the waste residue after sedimentation by a filter press to further reduce the moisture content of the waste residue; S13. Using a dilute acid solution to neutralize the waste residue, adjusting the pH value of the waste residue to 6.5 to 7.

5.

3. The method for treating aluminum oxidation wastewater slag according to claim 1, characterized in that: The steps of preparing the adsorption material and removing heavy metals include: S21. extracting chitosan and performing deacetylation treatment to increase the amino content; S22. Nano-iron oxide was synthesized by coprecipitation method, mixed with chitosan, and cross-linked into a composite adsorption material using a cross-linking agent; S23. Add the composite adsorption material to the waste residue for heavy metal adsorption treatment, and remove the heavy metals in the waste residue by stirring, mixing, and solid-liquid separation.

4. The method for treating aluminum oxidation wastewater slag according to claim 1, characterized in that: The dosage of the composite adsorption material in the heavy metal adsorption step is 0.5 g / L to 2.0 g / L, the reaction time is 30 minutes to 60 minutes, and the adsorption conditions include a pH value of 6.0 to 7.0, a temperature of 20° C. to 30° C., and a stirring speed of 200 rpm.

5. The method for treating aluminum oxidation wastewater slag according to claim 1, characterized in that: The aluminum oxide extraction and recovery steps include: S31. Acid dissolving the waste residue using a 20% sulfuric acid solution at 80°C to extract alumina; S32. The pH value of the aluminum-containing solution is adjusted to 5.5 to 6.0, and aluminum hydroxide is generated by precipitation; S33. Calcine aluminum hydroxide to generate aluminum oxide.

6. The method for treating aluminum oxidation wastewater slag according to claim 1, characterized in that: The solidification and stabilization treatment steps of the waste residue include: S41. Mix the waste residue with cement in a mass ratio of 4:1, add water and stir until formed; S42. Phosphate is added as a heavy metal stabilizer during the solidification process to generate insoluble heavy metal phosphate precipitates to reduce the leaching toxicity of heavy metals; S43. The formed solid body is cured at room temperature for 28 days.

7. The method for treating aluminum oxidation wastewater slag according to claim 1, characterized in that: The added amount of the phosphate stabilizer is 1% to 5% of the mass of the waste residue, preferably 2% of the mass of the waste residue.

8. The method for treating aluminum oxidation wastewater slag according to claim 1, characterized in that: The steps of recycling and discharging the wastewater up to standard include: S51. Adjust the pH value of the wastewater to neutral, add polyaluminium chloride and polyacrylamide as flocculants and coagulants, and perform precipitation treatment; S52. The supernatant after precipitation is used as washing water in the pretreatment stage, and the wastewater that is not recycled is discharged after being tested and found to meet the emission standards.

9. The method for treating aluminum oxidation wastewater slag according to claim 1, characterized in that: The dosage of the polyaluminium chloride is 50mg / L to 150mg / L, the dosage of the polyacrylamide is 0.5mg / L to 2mg / L, and the flocculation precipitation time is 1 hour to 2 hours.

10. The method for treating aluminum oxidation wastewater slag according to claim 1, characterized in that: The regeneration step of the adsorbent material after use comprises: a. Use 0.1 mol / L hydrochloric acid solution for desorption treatment to recover heavy metals in the adsorption material; b. Wash the desorbed adsorbent material with deionized water until it is neutral and dry it for recycling.

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