Aluminum ash pickling impurity removal and recycling process

Abstract

The invention provides an aluminum ash pickling, impurity removing and recycling process. The aluminum ash pickling, impurity removing and recycling process comprises the following steps that S1, aluminum ash is subjected to deamination treatment; s2, diluted hydrochloric acid is added into the deaminated aluminum ash, and impurity elements such as Fe, Ca, Na and F are dissolved; s3, filtering and separating, wherein the obtained solid is a high-alumina-content product subjected to impurity removal; s4, lime and Na2CO3 are added into the pickling wastewater, so that Fe, Ca and F ions in the filtrate react and then are respectively precipitated and removed; s5, filtering and separating precipitated solids, and recycling filter cakes as byproducts of Fe, Ca and F; s6, the filtrate is subjected to evaporation treatment, and concentrated halide salt serves as a by-product. The deaminated aluminum ash product subjected to acid pickling purification is high in additional value, no wastewater is discharged, the deaminated aluminum ash product is more environmentally friendly, the removal rate of by-products obtained in all the steps is high, and particularly the removal rate of fluorine ions is high, so that the fluorine ions remaining in the solution during final evaporation are few, and corrosion to evaporation equipment is effectively avoided.

Description

Technical Field

[0001] The invention relates to a processing technology for aluminum ash, in particular to a process for pickling, removing impurities and recycling aluminum ash. Background Art

[0002] In the process of aluminum casting, in order to obtain qualified performance, the aluminum liquid needs to be purified. Under the action of the refining agent, the impurities in the aluminum liquid float on the surface of the aluminum liquid. The scum is removed by slag removal. The removed scum is usually called aluminum ash. Aluminum ash contains metallic aluminum, inclusions mainly composed of aluminum oxide, and salts remaining from the refining agent. There are a large number of toxic elements. It is listed in the list of hazardous wastes by the Ministry of Ecology and Environment of China because of its reactivity and leaching toxicity. It needs to be harmlessly treated and applied.

[0003] The utilization and treatment process of aluminum ash mainly includes pyrometallurgical process and hydrometallurgical process, among which aluminum ash deammoniation is a common treatment step. After a series of process steps, harmful components such as ammonia and aluminum nitride in aluminum ash are removed to make it harmless and further use it as a resource. The main component of aluminum ash after deammoniation is aluminum oxide. In addition, it also contains a small amount of fluoride, silicate, and other impurities such as iron ions, calcium ions, and sodium ions. It is further processed according to needs, and by-products are obtained after separating harmful impurities.

[0004] Most of the existing aluminum ash treatment processes only carry out harmless treatment, and the obtained aluminum ash products mostly have high impurity content and low added value. Therefore, it is necessary to further separate the salts, iron, calcium and other impurities in the deaminated aluminum ash and convert them into recycled products, so that the main component alumina can be purified and finally used as raw materials for the production of various alumina products. Summary of the invention

[0005] The invention discloses an aluminum ash pickling, impurity removal and recycling process, which aims to solve the problems of low added value of aluminum ash after deammoniation, poor resource utilization effect, more impurities in the by-products obtained by treatment and faster equipment corrosion.

[0006] To achieve the above object, the present invention adopts the following technical solutions: A process for pickling, removing impurities and recycling aluminum ash, comprising the following steps: S1, deammoniation: deammoniation treatment of aluminum ash; S2, pickling: adding dilute hydrochloric acid to the aluminum ash after deammoniation to dissolve element ions such as Fe, Ca, Na, and F from the aluminum ash into the solution; S3, primary filtration; the solution after pickling and impurity removal is filtered, and the solid obtained after filtration and separation is the aluminum ash filter cake after impurities removal, and the aluminum ash filter cake has a water content of 15-30% by mass. The treatment of the aluminum ash filter cake is transferred to S4; after filtration and separation, pickling wastewater is also obtained, and the treatment of the pickling wastewater is transferred to S6; S4, washing: wash the aluminum ash filter cake after the first filter press with distilled water, control the water temperature to be above 60°C, liquid-solid mass ratio: 1:1-3, wash for 0.5-2h, and wash the residual elements in the filter cake into the wastewater; S5, secondary filter pressing; the washed aluminum ash filter cake is filtered again, and the washing wastewater is recycled for pulping to obtain the final high-content aluminum ash filter cake product; S6, neutralization and impurity removal; add lime and Na2CO3 to the pickling wastewater, adjust the pH value of the solution to 8-9, and make the Fe, Ca, and F ions in the filtrate react to generate Fe(OH)3, CaCO3, and CaF2 precipitates respectively; S7, filter pressing; the pickling wastewater after neutralization and impurity removal is filter pressed to obtain impurity removal filter cake including Fe(OH)3, CaCO3, CaF2 precipitation and high brine, and the impurity removal filter cake is used as a by-product for reprocessing; S8, evaporation treatment; the high brine obtained after the filter press is evaporated, and the distilled water obtained by evaporation is used for water washing in step S4. The mixed halide salt after evaporation is used as a by-product for reprocessing.

[0007] Preferably, in step S1, the deammoniation treatment is carried out by a wet process or a pyrometallurgical process.

[0008] Preferably, before step S2, the aluminum ash is first calcined at a high temperature with a heating rate of 12-15°C / s, a calcination temperature of 1200°C, and a calcination time of 1-2h to convert the aluminum-containing compounds in the aluminum ash into stable α-crystalline alumina that does not react with acid.

[0009] Preferably, in step S2, the hydrochloric acid used for pickling is prepared using an acid preparation tank, concentrated hydrochloric acid is added to the acid preparation tank, and at the same time, the washing wastewater after the secondary filter pressing in step S5 is added to the acid preparation tank to dilute the concentrated hydrochloric acid into dilute hydrochloric acid.

[0010] Preferably, in step S2, 5-10% concentration of dilute hydrochloric acid is added, the solid-liquid mass ratio of aluminum ash to dilute hydrochloric acid is 1:1-4, the reaction temperature is 60-90°C, and the reaction time is 40-80 minutes.

[0011] Preferably, in step S5, the mass fraction of aluminum oxide in the solid aluminum ash product obtained after filtration and separation is at least 85%, wherein the sum of the mass fractions of α-alumina and magnesium-aluminum spinel phases is at least 90%.

[0012] Preferably, in step S6, lime is first added to neutralize the excess hydrochloric acid in the pickling waste liquid, the pH value is adjusted to 5-6, most of the impurities are converted into precipitates, and then Na2CO3 is added to raise the pH value of the solution to 8-9, and excess calcium ions and residual aluminum, iron, magnesium, fluorine and other impurity ions are removed to make the water quality meet the evaporation conditions.

[0013] Preferably, in step S4, sodium ions, chloride ions and fluoride ions form an electrolyte balance.

[0014] Preferably, in step S6, the F ion content in the waste liquid before evaporation is less than 10 mg / L, and the calcium and magnesium ion contents are each less than 50 mg / L.

[0015] Preferably, in step S6, the mixed halide salt obtained after evaporation of the waste liquid includes NaCl and KCl.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The aluminum ash after deammoniation is first pickled and then washed with water for resource utilization. It is first pickled with hydrochloric acid of a certain concentration so that the elements Fe, Ca, Na, F and other elements in the aluminum ash are fully dissolved in the solution. After filtration, a high-purity aluminum ash product can be obtained, which can be used to make refractory materials to achieve higher economic value conversion; lime and Na2CO3 are added to the filtered pickling waste liquid to adjust the pH value and make Fe, Ca, F fully react to form a precipitate. The by-products of Fe, Ca and F can be obtained by secondary filtration. Finally, the filtered waste liquid is evaporated to obtain by-products such as NaCl and KCl after evaporating the water.

[0017] In the present invention, the washing wastewater in the secondary filter pressing step and the distilled water in the evaporation step can be recycled, thereby reducing the processing cost and reducing emissions.

[0018] The process of the present invention can remove the fluorine element before the final evaporation, and the fluorine ion content in the waste liquid used for evaporation is lower than 10 mg / L, which can effectively prevent the corrosion of the evaporation equipment.

[0019] The process cost of the present invention is low and the process is relatively simple. The obtained aluminum ash product has high purity, and all components can be separated and reused as by-products. No waste liquid is generated and discharged, which is more environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 It is a flow chart of a process for pickling, removing impurities and recycling aluminum ash; Figure 2 The present invention is an operation flow chart of an aluminum ash pickling, impurity removal and recycling process. DETAILED DESCRIPTION

[0022] In order to further understand the purpose, structure, characteristics, and functions of the present invention, this section will describe in detail the specific embodiments of the present invention. The preferred embodiments of the present invention are shown in the accompanying drawings. The purpose of the accompanying drawings is to supplement the description of the text part of the specification with graphics, so that people can intuitively and vividly understand each technical feature and the overall technical solution of the present invention, but it cannot be understood as a limitation on the scope of protection of the present invention.

[0023] Reference below Figure 1 A process for pickling, removing impurities and recycling aluminum ash of the present invention is described in detail.

[0024] A process for pickling, removing impurities and recycling aluminum ash, comprising the following steps: S1. Deammoniation: Deammoniation treatment is performed on the aluminum ash.

[0025] In some embodiments, the deammoniation treatment can be carried out by a commonly used wet process or a pyrometallurgical process. After deammoniation, Al and AlN in the aluminum ash are converted into Al2O3; the impurities contained include elements such as Fe, Ca, Na, F, and K. If a higher purity aluminum ash product is to be obtained, it is necessary to separate Fe, Ca, Na, F, K and other elements from Al2O3 as completely as possible.

[0026] S2. Pickling: Add dilute hydrochloric acid to the aluminum ash after deammoniation to dissolve element ions such as Fe, Ca, Na, and F from the aluminum ash into the solution.

[0027] The purpose of this pickling step is to dissolve the Fe, Ca, Na, F and other elements in the aluminum ash into the solution and remove them from the aluminum ash. The higher the removal rate, the better. Hydrochloric acid or sulfuric acid is usually used as a solvent for pickling. However, experiments have shown that the removal rate of the Ca element is low when sulfuric acid is used for pickling. Some CaSO4 will not be dissolved and remain in the aluminum ash, reducing the purity of the aluminum ash product and introducing SO4 2- , which increases the complexity of the pickling solution. Therefore, the present invention selects hydrochloric acid as the pickling agent. Aluminum ash itself contains Cl - , and will not produce precipitates with elements such as Fe, Ca, Na, and F, which is more convenient for subsequent waste liquid treatment and the salt composition is simple to obtain.

[0028] In addition, using dilute hydrochloric acid as a pickling agent increases its chloride ion concentration, which is conducive to the formation of chloride ion rejection, thereby facilitating the subsequent fluorine fixation and defluorination.

[0029] In some embodiments, the hydrochloric acid used for pickling is prepared using an acid preparation tank, concentrated hydrochloric acid is added to the acid preparation tank, and the washing wastewater after the secondary filtration in step S5 is added to the acid preparation tank to dilute the concentrated hydrochloric acid into dilute hydrochloric acid, thereby achieving the recycling of the washing wastewater, thereby avoiding wastewater discharge and saving processing resources.

[0030] In some more preferred embodiments, 5-10% dilute hydrochloric acid is added, the solid-liquid mass ratio of aluminum ash to dilute hydrochloric acid is 1:1-4, the reaction temperature is 60-90°C, and the reaction time is 40-80 minutes. Specifically, 5% dilute hydrochloric acid can be added, the solid-liquid ratio of aluminum ash to dilute hydrochloric acid is 1:2, the reaction temperature is 80°C, and the reaction time is 60 minutes.

[0031] After many experiments, it was found that the highest removal rates of Fe, Ca, Na, F and Si could reach about 44.87%, 84.03%, 93.95%, 70.11% and 32.32% respectively, and the mass fraction of alumina in aluminum ash was as high as 84.73%.

[0032] S3, one-time filtration; the solution after pickling and impurity removal is filtered, and the solid obtained after filtration and separation is the aluminum ash filter cake after impurities removal, and the mass percentage of water content in the aluminum ash filter cake is 15-30%. The treatment of the aluminum ash filter cake is transferred to S4; pickling wastewater is also obtained after filtration and separation, and the treatment of the pickling wastewater is transferred to S6.

[0033] In the following, steps S4-S5 are for treating the aluminum ash filter cake, and steps S6-S8 are for further treating the pickling wastewater.

[0034] S4, water washing; the aluminum ash filter cake after the first filter press is washed with distilled water, the liquid-to-solid mass ratio is 1:1-3, the water temperature is controlled above 60°C, and the washing time is 0.5-2h. The residual elements in the filter cake are washed into the wastewater to increase the aluminum content in the aluminum ash filter cake.

[0035] S5, secondary filtration: the washed aluminum ash filter cake is filtered again, and the washing wastewater is recycled for pulping to obtain a final high-content aluminum ash filter cake product. Specifically, the washing wastewater can be connected to the acid preparation tank in step S3 by a pump and a pipeline to dilute the concentrated hydrochloric acid and prepare the dilute hydrochloric acid.

[0036] The aluminum ash obtained by acid washing and filtration according to the present invention has high quality, wherein the mass fraction of aluminum oxide and magnesium aluminum spinel reaches more than 90%, and can be used as a raw material for high-quality aluminum oxide products.

[0037] In some embodiments, the high-quality aluminum ash product of the present invention can be used to make refractory materials after high-temperature sintering, such as producing refractory bricks, preparing brown corundum, preparing magnesia-alumina spinel, preparing mullite, etc.

[0038] S6, neutralization and impurity removal; add lime and Na2CO3 to the pickling wastewater in turn, adjust the pH value of the solution to 8-9, and make the Fe, Ca, and F ions in the filtrate react to generate Fe(OH)3, CaCO3, and CaF2 precipitates respectively.

[0039] In this step, lime is first added to neutralize the excess hydrochloric acid in the pickling waste liquid, the pH value is adjusted to 5-6, and then most of the Fe, Ca, and F ions are precipitated. Then Na2CO3 is added to raise the pH value of the solution to 8-9, and the excess calcium ions and residual aluminum, iron, magnesium, fluorine and other impurity ions are removed to make the water quality meet the evaporation conditions. Lime and Na2CO3 are both low-cost chemical agents. Adding Na2CO3 further adjusts the pH value to a weak alkaline state and precipitates the calcium ions introduced by the lime as calcium carbonate. CO3 in the solution 2- With the residual H + After the reaction, CO2 is generated and escapes, and no harmful waste gas is produced. The H + After being consumed, the OH - Ions and Fe 3+ 、Fe(OH)3,Ca 2+ With excess CO3 2- Combine to form CaCO3.

[0040] Soluble fluorine reacts with calcium in water to form calcium fluoride, completing the fluorine fixation. First, in order to increase the fluoride ion release rate, Na2CO3 is added to the waste liquid to increase the Na + , Cl - 、F - The electrolytes are then distributed in the water under the action of the electric field to form an equilibrium system, namely electrolyte balance; + and Cl - The ions of F have a smaller radius and stronger polarity, so they will move toward the positive electrode under the action of the electric field, while F - The ion radius of the ions is large and the polarity is weak, so they will move toward the negative electrode. As a result, the fluoride ions will move toward the negative electrode under the action of the electric field, thereby achieving removal. Second, chloride ion repulsion is conducive to the removal of fluoride ions; when chloride ion repulsion takes effect, chloride ions will exchange with fluoride ions on the surface of the ion layer, and chloride ions will throw fluoride ions from the ion layer, making it difficult for fluoride ions to combine with the ion layer, thereby achieving the purpose of removing fluoride ions. When the chloride ion concentration is high, the chloride ion repulsion effect is better, and the removal efficiency of fluoride ions is higher. Third, the pH value is also an important factor affecting the defluorination efficiency. When lime and Na2CO3 are added in the present invention to adjust the pH value of the waste liquid, preferably, the pH value is raised to the range of 8-9, which can improve the efficiency of CaCl2 defluorination to form CaF2 precipitation.

[0041] Therefore, lime and Na2CO3 are added in step S4 of the present invention to adjust the pH value and generate OH - Fe, Mg, and Ca are removed from the solution to form a precipitate that is then filtered and reused as a by-product, while also improving the efficiency of fluorine removal; its second function is to increase the Na + , so that Na + , Cl - 、F - Form electrolyte balance and increase the fluoride ion release rate; its third function is to utilize Cl in the solution - The formation of chloride ion repulsion is beneficial to improving the removal efficiency of fluoride ions. After CaCl2 fixes fluoride, CaF2 precipitates are generated and filtered to form a by-product for reuse.

[0042] S7, filter pressing; filter pressing the neutralized and impurity-removed pickling wastewater to obtain a filter cake containing Fe(OH)3, Ca(OH)2, and CaF2 precipitates and a high-salt water. The filter cake is used as a by-product for reprocessing. In this step, the high-salt water obtained after filtering the precipitate contains Na + , K + , Cl - wait.

[0043] S8, evaporation treatment; the high brine obtained after the filter press is evaporated, and the distilled water obtained by evaporation is used for water washing in step S4. The mixed halide salt after evaporation is used as a by-product for reprocessing and utilization. The halide salt obtained after evaporation of the waste liquid includes NaCl and KCl.

[0044] In the prior art, the fluorine ion concentration in the waste liquid is relatively high due to the relatively low fluorine ion release rate in the evaporation process of the secondary aluminum ash treatment. During the evaporation process, the fluorine ions corrode the evaporation equipment, increasing the treatment cost. In this step of the present invention, the fluorine ion concentration is very low. In some preferred embodiments, after the present invention is first acid-washed and then neutralized and washed with water, the F ion content in the waste liquid obtained is less than 10 mg / L, and the calcium and magnesium ion contents are each less than 50 mg / L. Therefore, the evaporation equipment can be effectively prevented from being corroded, the service life of the evaporation equipment can be extended, and the purity of by-products such as NaCl and KCl can also be improved.

[0045] The aluminum ash pickling, impurity removal and recycling process of the present invention first pickles and then washes the aluminum ash after deammoniation, and fully separates various elements in the aluminum ash in batches at one time and reuses them as by-products. Finally, no wastewater will be discharged, which is more environmentally friendly.

[0046] In some embodiments, before step S2, the aluminum ash is first calcined at a high temperature with a heating rate of 12-15°C / s, a calcination temperature of 1200°C, and a calcination time of 1-2h to convert the aluminum-containing compounds in the aluminum ash into stable α-crystalline alumina that does not react with acid.

[0047] The chemical composition of aluminum ash can be analyzed by X-ray fluorescence spectrometry (XRF) and chemical analysis, and the physical phase in aluminum ash can be analyzed by X-ray diffraction (XRD). After the aluminum ash is roasted and transformed, the aluminum oxide is converted from γ-Al2O3 to stable α-Al2O3. α-Al2O3 and MgAl2O4 are difficult to dissolve in acid and alkali solutions, so they will not be redissolved in the subsequent pickling process, which can effectively increase the Al2O3 content in the aluminum ash product obtained after pickling, impurity removal and filtration, thereby obtaining a high-quality aluminum ash product.

[0048] In some preferred embodiments, the mass fraction of aluminum oxide in the solid aluminum ash product obtained after filtration and separation in step S3 is at least 85%, and the sum of the mass fractions of α-alumina and magnesium aluminum spinel phase is at least 90%, and can be as high as 93.54%.

[0049] In summary, the aluminum ash pickling, impurity removal and recycling process of the present invention utilizes a relatively low cost and relatively simple operating procedure to first pickle the aluminum ash, then wash it with water, and finally evaporate it. After pickling, a high-quality aluminum ash product is obtained, which can be used to produce refractory materials; after washing and filtration, iron, calcium, and fluorine byproducts are obtained for reuse; finally, the water in the waste liquid is evaporated to obtain salt byproducts such as NaCl and KCl for reuse. After the ingenious design and treatment of the present invention, no wastewater will be discharged in the end, which is more environmentally friendly, and the byproduct removal rate obtained in each step is relatively high, especially the fluoride ion removal rate is higher than that of the prior art, so very few fluoride ions remain in the solution during the final evaporation, effectively avoiding corrosion to the evaporation equipment.

[0050] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0051] The present invention has been described by the above-mentioned relevant embodiments, but the above-mentioned embodiments are only examples for implementing the present invention, which are used to help understand the technical solutions and core ideas of the present application. It must be pointed out that the disclosed embodiments do not limit the scope of the present invention; on the contrary, the technical solutions recorded in the above-mentioned embodiments can still be modified, or some of the technical features therein can be replaced by equivalents; modifications and embellishments made without departing from the spirit and scope of the present invention are all within the scope of patent protection of the present invention.

Claims

1. A process for pickling, removing impurities and recycling aluminum ash, characterized in that: The following steps are involved: S1, deammoniation: deammoniation treatment of aluminum ash; S2, pickling; adding dilute hydrochloric acid to the aluminum ash after deammoniation to dissolve element ions such as Fe, Ca, Na, and F from the aluminum ash into the solution; S3, primary filtration; the solution after pickling and impurity removal is filtered, and the solid obtained after filtration and separation is the aluminum ash filter cake after impurities removal, and the aluminum ash filter cake has a water content of 15-30% by mass. The treatment of the aluminum ash filter cake is transferred to S4; after filtration and separation, pickling wastewater is also obtained, and the treatment of the pickling wastewater is transferred to S6; S4, washing: wash the aluminum ash filter cake after the primary filtration with distilled water, control the water temperature to be above 60°C, the liquid-solid mass ratio to be 1:1-3, wash for 0.5-2h, and wash the impurities remaining in the filter cake into the wastewater; S5, secondary filter pressing; the washed aluminum ash filter cake is filtered again, and the washing wastewater is recycled for pulping to obtain the final high-content aluminum ash filter cake product; S6, neutralization and impurity removal; add lime and Na2CO3 to the pickling wastewater in sequence, adjust the pH value of the solution to 8-9, and make the Fe, Ca, and F ions in the filtrate react to generate Fe(OH)3, CaCO3, and CaF2 precipitates respectively; S7, filter pressing; the pickling wastewater after neutralization and impurity removal is filter pressed to obtain impurity removal filter cake including Fe(OH)3, CaCO3, CaF2 precipitation and high brine, and the impurity removal filter cake is used as a by-product for reprocessing; S8, evaporation treatment; the high brine obtained after the filter press is evaporated, and the distilled water obtained by evaporation is used for water washing in step S4. The mixed halide salt after evaporation is used as a by-product for reprocessing.

2. The aluminum ash pickling, impurity removal and recycling process according to claim 1, characterized in that: In step S1, the deammoniation treatment is carried out by a wet process or a pyrometallurgical process.

3. The aluminum ash pickling, impurity removal and recycling process according to claim 1, characterized in that: Before step S2, the aluminum ash is first calcined at a high temperature with a heating rate of 12-15°C / s, a calcination temperature of 1200°C, and a calcination time of 1-2h to convert the aluminum compounds in the aluminum ash into stable α-crystalline aluminum oxide that does not react with acid.

4. The aluminum ash pickling, impurity removal and recycling process according to claim 1, characterized in that: In step S2, the hydrochloric acid used for pickling is prepared using an acid preparation tank, and concentrated hydrochloric acid is added to the acid preparation tank. At the same time, the washing wastewater after the secondary filter pressing in step S5 is added to the acid preparation tank to dilute the concentrated hydrochloric acid into dilute hydrochloric acid.

5. The aluminum ash pickling, impurity removal and recycling process according to claim 4, characterized in that: In step S2, 5-10% concentration of dilute hydrochloric acid is added, the solid-liquid mass ratio of aluminum ash to dilute hydrochloric acid is 1:1-4, the reaction temperature is 60-90° C., and the reaction time is 40-80 minutes.

6. The aluminum ash pickling, impurity removal and recycling process according to claim 1, characterized in that: In step S5, the solid aluminum ash product obtained after filtration and separation has an aluminum oxide mass fraction of at least 85%, wherein the sum of the mass fractions of α-alumina and magnesium-aluminum spinel phases is at least 90%.

7. The aluminum ash pickling, impurity removal and recycling process according to claim 1, characterized in that: In step S6, lime is first added to neutralize the excess hydrochloric acid in the pickling waste liquid, the pH value is adjusted to 5-6, most of the impurities are converted into precipitates, and then Na2CO3 is added to raise the pH value of the solution to 8-9, and excess calcium ions and residual aluminum, iron, magnesium, fluorine and other impurity ions are removed to make the water quality meet the evaporation conditions.

8. The aluminum ash pickling, impurity removal and recycling process according to claim 1, characterized in that: In step S4, sodium ions, chloride ions, and fluoride ions form an electrolyte balance.

9. The aluminum ash pickling, impurity removal and recycling process according to claim 1, characterized in that: In step S6, the F ion content in the waste liquid before evaporation is less than 10 mg / L, and the calcium and magnesium ion contents are each less than 50 mg / L.

10. The aluminum ash pickling, impurity removal and recycling process according to claim 1, characterized in that: In step S6, the mixed halide salt obtained after evaporation of the waste liquid includes NaCl and KCl.

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