Treatment method of aluminum-containing waste alkali liquor

Abstract

The invention provides a method for treating aluminum-containing waste alkali liquor, which comprises the following steps of: adding silicon dioxide powder with the specific surface area of less than or equal to 100m < 2 > / g into the aluminum-containing waste alkali liquor to form a mixed solution; and performing a hydrothermal reaction on the mixed solution to form an aluminum-containing solid and a purified alkali solution. The invention relates to a method for treating aluminum-containing waste alkali liquor, which comprises the following steps of: adding silicon dioxide powder of which the specific surface area is less than or equal to 100m < 2 > / g into the aluminum-containing waste alkali liquor to form a mixed solution; and performing a hydrothermal reaction on the mixed solution to form an aluminum-containing solid and a purified alkali solution.

Description

Technical Field

[0001] The invention relates to a method for recovering waste alkali liquor, in particular to a method for recovering waste alkali liquor containing aluminum. Background Art

[0002] Aluminum is the third most abundant element in the earth's crust. It is a metal with low hardness and easy ductility. In addition, because aluminum has active chemical properties and can form alloys with many metals, aluminum products are not only used in daily necessities, but can even be used as materials in the aerospace industry. Therefore, the processing of aluminum products has always been the focus of attention in the metal industry. The processing of aluminum products mainly includes casting, extrusion (or aluminum extrusion), electroplating and other processes. In various processing techniques, a strong alkaline solution is usually used to treat aluminum-containing raw materials or molds to dissolve aluminum alloys or other aluminum-containing compounds into aluminum ions, thereby achieving a cleaning effect. Therefore, the treated strong alkaline solution will contain a high concentration of aluminum ions. If the aluminum ions in the solution are not separated, the strong alkaline solution cannot be recycled.

[0003] Taking the electroplating process as an example, before plating other metals on aluminum alloy, the surface of the aluminum alloy is usually pre-treated with a strong alkaline solution to remove impurities such as grease and metal oxides on the surface of the aluminum alloy, thereby improving the efficiency of the electroplating process and the quality of the resulting electroplated layer. After pre-treatment, the strong alkaline solution will inevitably dissolve a portion of the aluminum alloy, so that the strong alkaline solution contains a certain concentration of aluminum ions.

[0004] In addition, taking the aluminum extrusion process as an example, the process includes the steps of storage and cutting of aluminum raw materials, preheating of aluminum extruded rods, preheating of molds, extrusion molding, cooling, etc., thereby producing aluminum extruded products. The molds used in the aluminum extrusion process are, for example, various steel molds, which are used to extrude the heated and softened aluminum raw materials, and then cool the extruded aluminum products to form the final aluminum extruded products. After completing each batch of aluminum extrusion process, more or less aluminum raw materials or aluminum-containing compounds will remain on the steel mold. If the residual aluminum raw materials or aluminum-containing compounds are not completely removed, the quality of subsequent batches of aluminum extruded products may be affected. In the current field, a strong alkaline solution is usually used to clean the steel mold, thereby removing the residual aluminum raw materials or aluminum-containing compounds on the steel mold. The strong alkaline solution after cleaning will therefore dissolve a high concentration of aluminum ions, forming "aluminum-containing waste alkali solution".

[0005] At present, the treatment method of "waste alkali liquid containing aluminum" is to use the principle of acid-base neutralization, by adding acid to the waste alkali liquid containing aluminum to remove its alkalinity. When the pH value of the waste alkali liquid containing aluminum gradually approaches neutrality, the aluminum ions in the waste alkali liquid containing aluminum will gradually "mineralize" to form solid aluminum compounds, which can then be filtered out. In this way, although the aluminum ions in the waste alkali liquid containing aluminum can be removed, the strong alkaline solution loses its strong alkalinity due to acid-base neutralization and cannot be recycled and reused. It can only be discharged after subsequent wastewater treatment. Therefore, the existing treatment method of waste alkali liquid containing aluminum is not only unable to recycle and reuse the strong alkaline solution containing aluminum ions, but also involves the process of acid-base neutralization and subsequent wastewater treatment, which leads to issues such as waste of resources and environmental pollution.

[0006] In view of this, it is indeed necessary to provide a method for treating aluminum-containing waste alkali liquid, which can effectively separate the aluminum ions and the strong alkali solution in the aluminum-containing waste alkali liquid, and enable the strong alkali solution to be recycled and reused. Summary of the invention

[0007] To solve the above problems, the purpose of the present invention is to provide a method for treating aluminum-containing waste alkali liquid, which can effectively separate aluminum ions and strong alkaline solution in the aluminum-containing waste alkali liquid, and enable the strong alkaline solution to be recycled and reused.

[0008] The elements and components described throughout the present invention use the quantifiers "a" or "an" for convenience only and to provide a general meaning of the scope of the present invention; they should be interpreted in the present invention as including one or at least one, and a single concept also includes plural cases, unless it is obvious that it means otherwise.

[0009] The method for treating the aluminum-containing waste alkali liquor of the present invention may include: treating the waste alkali liquor having a specific surface area of ​​≤100m 2 / g of silicon dioxide powder is added to an aluminum-containing waste alkali solution to form a mixed solution; and the mixed solution is subjected to a hydrothermal reaction to form an aluminum-containing solid and a purified alkali solution.

[0010] Therefore, the treatment method of the aluminum-containing waste alkali liquid of the present invention can use silica powder to carry out hydrothermal reaction with aluminum ions in the aluminum-containing waste alkali liquid to form the aluminum-containing solid (i.e., aluminum silicon oxide solid) to remove the aluminum ions in the aluminum-containing waste alkali liquid, and improve the recovery effect of the purified alkali liquid by reducing the specific surface area of ​​the silica powder, which is the effect of the present invention.

[0011] The method for treating the aluminum-containing waste alkali liquor of the present invention, wherein, in the mixed solution, Al2O3:SiO2:Na2O:H2O=1.0:x:y:z, wherein x is between 0.5 and 25.0, y is between 1.7 and 10.0, and z is between 5 and 400. Thus, by controlling the components of the mixed solution within the above range, the method for treating the aluminum-containing waste alkali liquor of the present invention can treat a wide range of aluminum-containing waste alkali liquors.

[0012] In the method for treating aluminum-containing waste alkali liquor of the present invention, the reaction temperature of the hydrothermal reaction is between 50° C. and 130° C., and the reaction time is between 2 hours and 48 hours. Thus, the above reaction conditions can effectively form the aluminum-containing solid (i.e., aluminum silicon oxide solid) with the silicon dioxide powder and the aluminum ions in the aluminum-containing waste alkali liquor, thereby effectively removing the aluminum ions in the aluminum-containing waste alkali liquor.

[0013] The method for treating the aluminum-containing waste alkali liquor of the present invention further comprises separating the aluminum-containing solid from the purified alkali liquor. In this way, the purified alkali liquor treated by the method for treating the aluminum-containing waste alkali liquor of the present invention can be recovered and used in the process of aluminum products, thereby reducing the manufacturing cost and achieving environmentally friendly effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 : XRD diffraction pattern of the solid product of Example A1 of the present invention. DETAILED DESCRIPTION

[0015] In order to make the above and other objects, features and advantages of the present invention more obvious and understandable, preferred embodiments of the present invention are listed below and described in detail with reference to the accompanying drawings.

[0016] The method for treating the aluminum-containing waste alkali liquor of the present invention may for example comprise: treating the waste alkali liquor having a specific surface area of ​​≤100m 2 / g of silicon dioxide powder is added to an aluminum-containing waste alkali solution to form a mixed solution; the mixed solution is subjected to a hydrothermal reaction to form an aluminum-containing solid and a purified alkali solution; and the aluminum-containing solid is separated from the purified alkali solution, so that the purified alkali solution can be recovered.

[0017] In detail, in the present invention, the aluminum-containing solid (i.e., aluminum silicon oxide solid) is formed by using silicon dioxide powder to carry out hydrothermal reaction with aluminum ions in aluminum-containing waste alkali liquid to remove aluminum ions in the aluminum-containing waste alkali liquid, and the recovery effect of purified alkali liquid is improved by reducing the specific surface area of ​​silicon dioxide powder. The specific surface area (specific surface area, SSA) of silicon dioxide can usually be determined according to the manufacturing method and subsequent treatment, and according to the different manufacturing methods, the obtained silicon dioxide can be divided into fumed silica (FSiO2 for short), precipitated silica (PSiO2 for short) and high-temperature oxidation-reduction silica (redox fume for short RSiO2). Fumed silica (FSiO2) is obtained by burning silicon tetrachloride (SiCl4) in air (referred to as combustion method in the art), and its specific surface area is determined to be 220m by BET analysis. 2 / g. Precipitated silica (PSiO2) is obtained by using water glass as a raw material and acid for precipitation reaction. Its specific surface area is 135m 2 / g. Reduced silicon dioxide (RSiO2) is obtained by, for example, using quartz glass as a raw material and carbon or magnesium as a reducing agent, undergoing an oxidation-reduction reaction at a temperature between 700°C and 2000°C. Its specific surface area is 20 m 2 / g.

[0018] The aluminum-containing waste alkali solution can be, for example, a sodium hydroxide (NaOH) solution containing aluminum ions, a potassium hydroxide (KOH) solution, or other strong alkali solutions. In this embodiment, the aluminum-containing waste alkali solution is a sodium hydroxide solution containing aluminum ions; wherein, in the mixed solution, the molar ratio of each component can be, for example, Al2O3:SiO2:Na2O:H2O=1.0:x:y:z, wherein x is between 0.5 and 25.0, y is between 1.7 and 10, and z is between 5 and 400.

[0019] In the present embodiment, the reaction temperature of the hydrothermal reaction can be between 50°C and 130°C, and the reaction time can be between 2 hours and 48 hours. The above reaction conditions can effectively form the aluminum-containing solid (i.e., aluminum silicon oxide solid) with the aluminum ions in the aluminum-containing waste alkali liquid, thereby removing the aluminum ions in the aluminum-containing waste alkali liquid. The aluminum-containing solid can be, for example, zeolite. After the aluminum-containing solid or zeolite is formed, the aluminum-containing solid can be separated from the purified alkali liquid by a filtering device, that is, the purified alkali liquid can be recovered; wherein, the filtering device can be, for example, a filter screen, and the pore size of the filter screen can be adjusted according to the process requirements, which can be understood by technicians in the technical field to which the present invention belongs, and the present invention is not limited thereto.

[0020] In order to confirm the effect of the specific surface area of ​​silicon dioxide on the recovery effect of purified alkali solution, the following test was carried out:

[0021] (A) Effect of Specific Surface Area of ​​Silica (I)

[0022] In this experiment, 9.9 g of the above-mentioned different types of silicon dioxide (FSiO2, PSiO2 and RSiO2) were added to 43.0 g of an aluminum-containing waste alkali solution to form a mixed solution; wherein the aluminum ion concentration in the aluminum-containing waste alkali solution was 11.6 wt%, and the NaOH concentration was 29.0 wt%. In the mixed solution, the molar ratio of each component was Al2O3:SiO2:Na2O:H2O=1.0:1.8:1.7:14.5, wherein SiO2 / Al2O3=1.8, H2O / Na2O=8.5, and H2O / Al2O3=14.5. After the mixed solution was stirred at room temperature for 30 minutes, it was moved to an oven for hydrothermal reaction (reaction temperature was 75°C and reaction time was 4 hours) to obtain a reaction solution. After the hydrothermal reaction is completed, the reaction solution is cooled to room temperature, and then the aluminum-containing solid (i.e., zeolite) and liquid (i.e., purified alkali solution) are separated by a centrifuge. Next, the zeolite yield and the purified alkali solution yield are calculated, and the aluminum content and sodium content in the purified alkali solution are measured using inductively coupled plasma mass spectrometry (ICP-AES), thereby converting the NaOH concentration and aluminum ion concentration in the purified alkali solution. In this experiment, the zeolite yield and the purified alkali solution yield were calculated using the following formulas, respectively. The experimental results are shown in Table 1.

[0023]

[0024]

[0025] Table 1. Recovery data of aluminum-containing waste alkali liquor in each group of this experiment.

[0026]

[0027]

[0028] Please refer to Table 1. The silica powders of Group A1 to Group A3 can effectively recover the alkaline components in the aluminum-containing waste alkali solution (the NaOH concentration before and after purification is not much different), and can effectively reduce the aluminum ion concentration in the aluminum-containing waste alkali solution (from 11.6wt% before purification to about 1.5wt%). However, the yield of the purified alkali solution increases with the decrease in the specific surface area of ​​the silica powder. Therefore, the yield of the purified alkali solution of Group A3 is about 1.7 times that of Group A1, indicating that a lower specific surface area helps to improve the yield of the purified alkali solution. In addition, the crystal structure of the aluminum-containing solid of Group A1 was identified using the XRD diffraction pattern. The results are as follows: Figure 1 As shown in Table 2, the corresponding table of diffraction peak 2θ angle, (hkl) crystal plane and lattice constant d is obtained. After comparing with the standard spectrum of Collection of Simulated XRD Powder Patterns for Zeolites compiled by MMJTreacy and JBHiggins, it can be known that the zeolite structure corresponding to the diffraction spectrum peak belongs to the LTA zeolite group structure, and its structural formula is Na 12 [Al 12 Si 12 O 48 ], indicating that the generated aluminum-containing solid has oxide components of aluminum, silicon and sodium. In addition, the aluminum ion concentration of the purified alkali solution generated by the reaction is significantly lower than the aluminum ion concentration of the aluminum-containing waste alkali solution. The comprehensive properties of the aluminum-containing solid and the purified alkali solution show that during the reaction, the aluminum ions contained in the aluminum-containing waste alkali solution react with silicon dioxide to form zeolite, and silicon dioxide can effectively bind to the aluminum ions contained in the aluminum-containing waste alkali solution, thereby effectively removing the aluminum ions from the aluminum-containing waste alkali solution.

[0029] Table 2. Correspondence between diffraction peak angles, crystal planes and lattice constants of group A1

[0030]

[0031]

[0032] In order to test the effect of different treatment methods on the specific surface area of ​​silicon dioxide powder, the following experiments were conducted:

[0033] (B) Effect of treatment method on specific surface area

[0034] In this test, precipitated silica (PSiO2) was subjected to different treatments, and the specific surface area of ​​each group of silica after treatment was determined by BET analysis. The test conditions of each group are as follows:

[0035] ˙PSiO2-760:

[0036] 15.0 g of PSiO2 powder was placed in a tubular quartz tube, air was introduced, and heat-treated at 760°C for 6 hours. The specific surface area of ​​the obtained sample was measured by BET analysis.

[0037] ˙PSiO2-540AS:

[0038] 15.0 g of PSiO2 powder was placed in a tubular quartz tube, and air containing saturated water vapor was introduced. After hydrothermal treatment at 540°C for 6 hours, the specific surface area of ​​the obtained sample was measured by BET analysis.

[0039] ˙PSiO2-760AS:

[0040] 15.0 g of PSiO2 powder was placed in a tubular quartz tube, and air containing saturated water vapor was introduced. After hydrothermal treatment at 760°C for 6 hours, the specific surface area of ​​the obtained sample was measured by BET analysis.

[0041] ˙PSiO2-X:

[0042] 10.9 g of PSiO2 powder was placed in a three-necked flask, and 6.15 g of tetraethoxysilane (TEOS) and 100 mL of toluene were added, followed by heating and reflux reaction for 6 hours. Then, the solid product was collected by filtration, and after washing the solid product with water several times, the solid product was transferred to an oven at 110°C and dried for 8 hours. Then, the dried product was placed in a tubular quartz tube, air was introduced, and heat-treated at 540°C for 6 hours, and the specific surface area of ​​the obtained sample was determined by BET analysis.

[0043] Table 3. Changes in specific surface area of ​​silicon dioxide powder in each group of this experiment.

[0044]

[0045] Please refer to Table 3. Group B1 subjected precipitated silica (PSiO2) powder to high-temperature heat treatment (i.e., calcination) in air. Although the PSiO2 powder will disintegrate due to the high temperature, causing a slight decrease in the specific surface area after treatment, the decrease is not large. Groups B2 and B3 subjected PSiO2 powder to high-temperature hydrothermal treatment in air containing saturated water vapor. The high-temperature water vapor can help destroy the pore structure of silica, making the PSiO2 powder easier to disintegrate. Therefore, the decrease in the specific surface area of ​​Groups B2 and B3 after treatment is greater than that of Group B1. In addition, the specific surface area of ​​Group B3 after treatment is lower than that of Group B2, indicating that under the same condition of introducing saturated water vapor, a higher temperature (760°C>540°C) can further promote the disintegration of PSiO2 powder, thereby reducing the specific surface area. Group B4 subjected PSiO2 powder to a reflux reaction with tetraethoxysilane (TEOS), so that TEOS was attached to the surface of the PSiO2 powder to block the pores, thereby reducing the specific surface area of ​​the PSiO2 powder.

[0046] Next, in order to further confirm the effect of specific surface area on the recovery effect of purified alkali solution using different PSiO2 powders prepared in experiment (B), the following experiment was conducted:

[0047] (C) Effect of Specific Surface Area of ​​Silica (II)

[0048] In this experiment, 13.3 g of each group of silicon dioxide was added to 122.0 g of an aluminum-containing waste alkali solution to form a mixed solution; wherein the aluminum ion concentration in the aluminum-containing waste alkali solution was 5.5 wt %, and the NaOH concentration was 19.1 wt %. In the mixed solution, the molar ratio of each component was Al2O3:SiO2:Na2O:H2O=1.0:1.8:2.4:41.2, wherein SiO2 / Al2O3=1.8, H2O / Na2O=17.2, and H2O / Al2O3=41.2. After the mixed solution was stirred at room temperature for 30 minutes, a hydrothermal reaction was carried out at 75° C. in a closed environment for 4 hours to obtain a reaction solution. After the hydrothermal reaction was completed, the reaction solution was cooled to room temperature, and then the solid (i.e., zeolite) and the liquid (i.e., purified alkali solution) were separated by a centrifuge. Next, the zeolite yield and the purified alkali liquor yield were calculated, and the aluminum content and sodium content in the purified alkali liquor were measured by inductively coupled atomic emission spectrometry (ICP-AES), thereby converting the NaOH concentration and aluminum ion concentration in the purified alkali liquor. In this experiment, the zeolite yield and the purified alkali liquor yield were calculated using the following formulas, respectively. The test results are shown in Table 4.

[0049]

[0050]

[0051] Table 4. Recovery data of aluminum-containing waste alkali liquor in each group of this experiment.

[0052]

[0053]

[0054] Please refer to Table 4. For the same type of silica powder (i.e., the PSiO2 series of Groups C2 to C6), the yield of purified alkali solution generally increases as the specific surface area of ​​the silica powder decreases. It can be confirmed that a lower specific surface area helps to improve the yield of purified alkali solution, and the yield of purified alkali solution of Group C5 (48wt%) is almost equivalent to the yield of purified alkali solution of Group C1 (50wt%).

[0055] Next, in order to confirm the effect of the temperature of the hydrothermal reaction on the recovery effect of the purified alkali solution, the following test was conducted:

[0056] (D) Effect of reaction temperature on hydrothermal reaction

[0057] In this experiment, 11.1 g of PSiO2-760AS powder was added to 57.7 g of an aluminum-containing waste alkali solution and 19.4 g of water to form a mixed solution; wherein the aluminum ion concentration in the aluminum-containing waste alkali solution was 9.6 wt %, and the NaOH concentration was 27.9 wt %. In the mixed solution, the molar ratio of each component was Al2O3:SiO2:Na2O:H2O=1.0:1.8:1.95:29.3, wherein SiO2 / Al2O3=1.8, H2O / Na2O=15.0, and H2O / Al2O3=29.3. After the mixed solution was stirred at room temperature for 30 minutes, a hydrothermal reaction was carried out at 65°C, 75°C, 85°C and 95°C in a closed environment for 4 hours to obtain a reaction solution. After the hydrothermal reaction was completed, the reaction solution was cooled to room temperature, and then the solid (i.e., zeolite) and the liquid (i.e., purified alkali solution) were separated by a centrifuge. Next, the zeolite yield and the purified alkali solution yield were calculated, and the aluminum content and sodium content in the purified alkali solution were measured using inductively coupled plasma atomic emission spectrometry (ICP-AES), thereby converting the NaOH concentration and aluminum ion concentration in the purified alkali solution. In this experiment, the zeolite yield and the purified alkali solution yield were calculated using the following formulas, respectively. The test results are shown in Table 5.

[0058]

[0059]

[0060] Table 5. Recovery data of aluminum-containing waste alkali liquor in each group of this experiment.

[0061]

[0062] As shown in Table 5, the yield of purified alkali liquor generally increases with the increase of hydrothermal reaction temperature, indicating that higher temperature is helpful to improve the yield of purified alkali liquor. However, the difference in the yield of purified alkali liquor of Group D2 to Group D4 is not large, indicating that the treatment method of aluminum-containing waste alkali liquor of the present invention can obtain good alkali liquor recovery effect within a certain range of hydrothermal reaction temperature, thereby reducing the restriction of reaction conditions.

[0063] Next, in order to confirm the effect of the SiO2 / Al2O3 ratio on the recovery effect of purified alkali solution, the following test was conducted:

[0064] (E) Effect of SiO2 / Al2O3 ratio

[0065] In this experiment, 12.8g, 51.3g and 89.6g of RSiO2 powder were added to 104.2g of an aluminum-containing waste alkali solution, and 61.3g of water was added to form a mixed solution; wherein the aluminum ion concentration in the aluminum-containing waste alkali solution was 5.5wt%, and the NaOH concentration was 15.1wt%. In the mixed solution, the molar ratio of each component was Al2O3:SiO2:Na2O:H2O=1.0:x:1.9:74.5, wherein SiO2 / Al2O3=x, H2O / Na2O=40.0, and H2O / Al2O3=74.5; wherein x was changed by the addition amount of RSiO2 powder, and the range could be between 0.5 and 25.0. In this embodiment, the experiment was conducted under the conditions of x=2.0, 8.0 and 14.0. After the mixed solution was stirred at room temperature for 30 minutes, a hydrothermal reaction was carried out at 105°C in a closed environment for 48 hours to obtain a reaction solution. After the hydrothermal reaction was completed, the reaction solution was cooled to room temperature, and the solid (i.e., zeolite) and the liquid (i.e., purified alkali solution) were separated by a centrifuge. Then, the zeolite yield and the purified alkali solution yield were calculated, and the aluminum content and sodium content in the purified alkali solution were measured by inductively coupled plasma atomic emission spectrometry (ICP-AES), thereby converting the NaOH concentration and aluminum ion concentration in the purified alkali solution. In this experiment, the zeolite yield and the purified alkali solution yield were calculated using the following formulas, respectively. The experimental results are shown in Table 6.

[0066]

[0067]

[0068] Table 6. Recovery data of aluminum-containing waste alkali liquor in each group of this experiment.

[0069]

[0070]

[0071] Please refer to Table 6, the NaOH concentration of the alkali solution mixed with the aqueous solution before the reaction is 9.5wt%, and the difference in the yield of the purified alkali solution generated by the reactions of Groups E1 to E3 is not large, and the NaOH concentration is between 8.3-8.6wt%, indicating that the treatment method of the aluminum-containing waste alkali solution of the present invention can obtain a good alkali solution recovery effect under a certain range of SiO2 / Al2O3 ratios, thereby reducing the restrictions on reaction conditions. In addition, under the hydrothermal reaction conditions of this embodiment (i.e., at 105°C for 48 hours), RSiO2 powder is used to treat the aluminum-containing waste alkali solution. The aluminum ion concentration in the recovered purified alkali solution is no longer detectable, but it has a good purified alkali solution yield, indicating that the treatment method of the aluminum-containing waste alkali solution of the present invention can indeed effectively remove aluminum ions in the aluminum-containing waste alkali solution and recover the purified alkali solution with a high yield.

[0072] Next, in order to confirm the recovery effect of the purified alkali liquor recovered by the treatment method of the aluminum-containing waste alkali liquor of the present invention on the aluminum dissolution rate, the following test was conducted:

[0073] (F) Recovery effect of aluminum dissolution rate

[0074] In this test, each group of alkali solution to be tested in Table 7 is placed in a container, and then a 6061 aluminum sheet with a weight of 0.52±0.01g and a size of 2×1×0.1cm is immersed in each group of alkali solution to be tested. After the container is sealed, it is reacted at room temperature (25°C) for 30 minutes. Then the aluminum sheet after immersion is taken out, the surface residue is removed and the weight is weighed after drying, and the aluminum dissolution rate of each group of alkali solution to be tested is calculated according to the following formula. In this test, the new alkali solution refers to the alkali solution prepared with fresh sodium hydroxide, and the concentrations are shown in Table 7; the purified alkali solution used in Group F1 is the purified alkali solution recovered by the test conditions of Group A3, and the purified alkali solution used in Group F2 is the purified alkali solution recovered by the test conditions of Group E3. The test results are shown in Table 7.

[0075]

[0076] Table 7. Data on the aluminum dissolution rate of each group of alkali solution tested in this experiment.

[0077]

[0078]

[0079] Please refer to Table 7. Since the aluminum-containing waste alkali liquor contains a high concentration of aluminum ions, its aluminum dissolving rate is much lower than that of the new alkali liquor. However, after the aluminum-containing waste alkali liquor is treated by the method for treating the aluminum-containing waste alkali liquor of the present invention, the aluminum dissolving rate of the recovered purified alkali liquor has been greatly restored / improved, indicating that the purified alkali liquor recovered by the method for treating the aluminum-containing waste alkali liquor of the present invention can indeed be recovered and used in the process of aluminum products.

[0080] In summary, the method for treating aluminum-containing waste alkali liquid of the present invention can use silica powder to carry out hydrothermal reaction with aluminum ions in the aluminum-containing waste alkali liquid to form the aluminum-containing solid (i.e., aluminum silicon oxide solid) to remove the aluminum ions in the aluminum-containing waste alkali liquid, and improve the recovery effect of the purified alkali liquid by reducing the specific surface area of ​​the silica powder, which is the effect of the present invention.

[0081] Although the present invention has been disclosed using the above-mentioned preferred embodiments, they are not intended to limit the present invention. Any person skilled in the art may make various changes and modifications to the above-mentioned embodiments without departing from the spirit and scope of the present invention, and these changes and modifications still fall within the technical scope protected by the present invention. Therefore, the protection scope of the present invention shall include all changes within the meaning and equivalent scope of the claims.

Claims

1. A method for treating aluminum-containing waste alkali liquor, characterized in that: include: The specific surface area is ≤100m 2 / g of silicon dioxide powder is added into an aluminum-containing waste alkali solution to form a mixed solution; and The mixed solution is subjected to a hydrothermal reaction to form an aluminum-containing solid and a purified alkaline solution.

2. The method for treating aluminum-containing waste alkali liquor according to claim 1, characterized in that: In the mixed solution, Al2O3:SiO2:Na2O:H2O=1.0:x:y:z, wherein x is between 0.5 and 25.0, y is between 1.7 and 10, and z is between 5 and 400.

3. The method for treating aluminum-containing waste alkali liquor according to claim 1, characterized in that: The reaction temperature of the hydrothermal reaction is between 50° C. and 130° C., and the reaction time is between 2 hours and 48 hours.

4. The method for treating aluminum-containing waste alkali liquor according to any one of claims 1 to 3, characterized in that: The method also includes separating the aluminum-containing solid from the purified alkali solution.

Images