Method for forming aluminum trihydrate

Abstract

A method for forming aluminum trihydrate is provided, comprising: mixing aluminum scrap with sodium hydroxide at a first predetermined temperature to form a mixture, the aluminum scrap having an aluminum oxide content of 30% or more based on the total weight of the aluminum scrap; filtering the mixture to obtain a first filtrate and a first residue; diluting the first filtrate with water; and mixing the first filtrate with carbon dioxide at a second predetermined temperature to obtain an ATH residue and a second filtrate.

Description

Technical Field

[0001] Technical Field The present invention relates to a method for forming aluminum trihydrate.

Background Art

[0002] Background Aluminum scraps are by-products from aluminum refining and may contain metallic aluminum, aluminum oxide, and other metal oxides. Generally, after the recovery of aluminum from aluminum scraps, the scraps are discarded by landfill, which may lead to the leaching of toxic metal ions into groundwater, causing water pollution problems and loss of raw materials. Further, when aluminum scraps come into contact with water, ammonia, hydrogen gas, and other flammable gases may be generated, which not only pollute the air when stored inappropriately but may also be a source of fire and explosion.

[0003] There are several methods for recovering aluminum from aluminum scraps. For example, 85 - 90% of the aluminum oxide in the scraps can be recovered and purified using an acid dissolution method and a sodium hydroxide high-temperature melting method. Such methods can recover more than 90% of the aluminum in aluminum scraps. However, both methods are energy-intensive and, therefore, not cost-effective and energy-efficient.

[0004] Aluminum trihydrate (ATH) can be converted into alumina and then into aluminum. ATH is also widely used in polymers protected by refractory materials for use in the electronics and automotive industries. However, these applications are a small percentage compared to the capacity converted into alumina for aluminum production.

Summary of the Invention

Problems to be Solved by the Invention

[0005] Therefore, improved methods are needed to recover large quantities of aluminum in metallic and chemical forms from aluminum scrap. [Means for solving the problem]

[0006] Summary of the present invention The present invention aims to address these problems and / or to provide an improved method for preparing aluminum trihydrate.

[0007] According to the first aspect, the present invention is a method for preparing aluminum trihydrate (ATH), - Mixing aluminum scrap with sodium hydroxide at a first predetermined temperature to form a mixture (wherein the aluminum scrap has an aluminum oxide content of 30% or more relative to the total weight of the aluminum scrap); - Filter the mixture to obtain the first filtrate and the first residue; - Diluting the first filtrate with water; and - The first filtrate is mixed with carbon dioxide at a second predetermined temperature to obtain the ATH residue and the second filtrate. This provides a method that includes [something].

[0008] The aluminum scrap may be any suitable aluminum scrap. In particular, the aluminum scrap may have an aluminum oxide content of 60-90% of the total weight of the aluminum scrap.

[0009] In another specific embodiment, the aluminum scrap may be powdered aluminum scrap. In particular, the aluminum scrap may have an average particle size of 0.002 to 10.0 mm.

[0010] The mixture may contain any suitable amount of aluminum scrap and sodium hydroxide. For example, the mixture may contain aluminum scrap and sodium hydroxide in a ratio of 1:0.2 to 1:8.

[0011] The first predetermined temperature may be any suitable temperature. For example, the first predetermined temperature may be 50 to 100°C.

[0012] Dilution may include diluting the filtrate with any suitable amount of water. In particular, dilution may include diluting the first filtrate at a dilution ratio of 1.5 to 4.

[0013] In certain embodiments, mixing the first filtrate with carbon dioxide may include introducing carbon dioxide into the first filtrate at a flow rate of 9 to 20 kg / min. The second predetermined temperature at which the first filtrate is mixed with carbon dioxide may be a suitable temperature. For example, the second predetermined temperature may be 40 to 100°C.

[0014] Mixing the first filtrate with carbon dioxide may include allowing carbon dioxide to flow into the first filtrate for a suitable period of time. For example, the mixing may take 60 to 180 minutes.

[0015] This method may be carried out under any suitable conditions. In particular, this method may be carried out at atmospheric pressure.

[0016] In certain embodiments, the method may further include evaporating the second filtrate to form sodium bicarbonate. The evaporation may be any preferred form of evaporation. In particular, the evaporation may include evaporation under reduced pressure.

[0017] In certain embodiments, the method may further include heating sodium bicarbonate to form sodium carbonate.

[0018] Brief explanation of the drawing In order to fully understand the present invention and to easily translate it into practical effects, the following description will be based on non-limiting, illustrative embodiments, which relate to the accompanying illustrative drawings. In these drawings: [Brief explanation of the drawing]

[0019] [Figure 1]Shows the weight of the aluminum scraps used and the weight of the recovered wet and dry reaction oxide residues (ROR); [Figure 2] Shows the weight of the aluminum scraps used and the weight of the recovered wet and dry white precipitate residues (WPP); [Figure 3] Shows the percentage purity of the recovered aluminum trihydrate (ATH); [Figure 4] Shows the oil absorption (g / 100g) of the recovered aluminum trihydrate (ATH); [Figure 5] Shows the whiteness of the recovered aluminum trihydrate (ATH); [Figure 6] Shows the moisture content (wt%) of the recovered aluminum trihydrate (ATH).

Mode for Carrying Out the Invention

[0020] Detailed Description As described above, there is a need for an improved method for recovering aluminum from aluminum scraps.

[0021] Generally speaking, the present invention provides an improved method for preparing aluminum trihydrate (ATH). The ATH may then be converted to aluminum. In this way, effective recovery of aluminum may be achieved from aluminum scraps in an environmentally friendly manner. Furthermore, the method of the present invention utilizes carbon dioxide and thereby helps to reduce carbon emissions. The by-products of the method may also have further uses, thereby making the method advantageous in terms of minimizing waste and reducing the loss of resources to landfill.

[0022] According to a first aspect, the present invention is a method for preparing aluminum trihydrate (ATH), the method comprising - Mixing aluminum scraps with sodium hydroxide at a first predetermined temperature to form a mixture, wherein the aluminum scraps have an aluminum oxide content of 30% or more based on the total weight of the aluminum scraps; - Filter the mixture to obtain the first filtrate and the first residue; - Diluting the first filtrate with water; and - The first filtrate is mixed with carbon dioxide at a second predetermined temperature to obtain the ATH residue and the second filtrate. This provides a method that includes [something].

[0023] The aluminum scrap may be any suitable aluminum scrap. For example, the aluminum scrap may have an aluminum oxide content of 30-95%, 35-90%, 40-85%, 45-80%, 50-75%, 55-70%, or 60-65% of the total weight of the aluminum scrap. In particular, the aluminum scrap may have an aluminum oxide content of 60-90% of the total weight of the aluminum scrap.

[0024] Aluminum scrap may contain salts. These salts may include, but are not limited to, silicates, chlorides, fluorides, and nitrates. For example, aluminum scrap may contain sodium chloride.

[0025] The aluminum scrap may be in any preferred form. For example, the aluminum scrap may be in powder form. The aluminum scrap may be formed into powder by any preferred method known in the art. For example, the aluminum scrap may be processed by physical crushing methods using a hammer, a jaw crusher, or a crusher to grind the aluminum scrap. In certain embodiments, the aluminum scrap may be in block form, in which case the aluminum scrap may be further processed as described above to convert it into a form more suitable for the purposes of the method of the present invention.

[0026] The aluminum scrap may be of any preferred size. For example, the aluminum scrap may have an average particle size of 0.002 to 10.0 mm. For the purposes of the present invention, the average particle size may mean the average height of the aluminum scrap particles or the average width of the aluminum scrap particles. In particular, the aluminum scrap may have an average particle size of 0.01 to 9.0 mm, 0.05 to 8.0 mm, 0.1 to 7.0 mm, 0.5 to 6.0 mm, 1.0 to 5.0 mm, 2.0 to 4.0 mm, or 2.5 to 3.0 mm. More particularly, the aluminum scrap may have an average particle size of 0.002 to 3.0 mm.

[0027] The mixing may involve mixing a suitable amount of aluminum scrap with sodium hydroxide to form a mixture. In a particular embodiment, the mixing may involve mixing the aluminum scrap and sodium hydroxide in a weight ratio of 1:0.2 to 1:8. For example, the ratio may be 1:0.5 to 1:7, 1:0.7 to 1:6, 1:1 to 1:5, 1:1.3 to 1:4, 1:1.5 to 1:3, or 1:2 to 1:2.5. In particular, the ratio may be 1:0.7 to 1:1.3, and more particularly, the ratio may be 1:0.7.

[0028] The mixing may take place at any preferred temperature. For example, the mixing may take place at a first predetermined temperature of 50 to 100°C. In particular, the mixing may take place at temperatures of 55 to 95°C, 60 to 90°C, 65 to 85°C, 70 to 80°C, or 75 to 78°C. More specifically, the temperature may be 80 to 100°C.

[0029] The mixing may be carried out for a suitable period of time. For example, the mixing may be carried out for 1 to 4 hours. In particular, the mixing may be carried out for 1.5 to 3.5 hours, 1.75 to 3.0 hours, or 2.0 to 2.5 hours. More specifically, the mixing may be carried out for 2 hours.

[0030] The mixture may include the following reactions:

[0031] [ka]

[0032] After mixing, the mixture may be filtered. Filtration may be carried out by any preferred method. Filtration may be performed to separate the first residue from the first filtrate. The first residue may be collected and stored for further use and / or processing.

[0033] The first filtrate may contain a sodium aluminate solution. The first filtrate may be diluted with water to obtain a diluted filtrate. For example, dilution of the first filtrate may involve diluting the first filtrate with a suitable amount of water. In particular, dilution may involve diluting the filtrate at a dilution ratio of 1.5 to 4. More specifically, the dilution ratio may be 2.

[0034] As soon as the first filtrate is diluted, the method may include mixing the first filtrate with carbon dioxide. Mixing may include mixing the first filtrate with carbon dioxide, or it may include introducing carbon dioxide into the first filtrate. In particular, mixing may include bubbling carbon dioxide into the first filtrate. Mixing the first filtrate with carbon dioxide may include the following reactions:

[0035] [ka]

[0036] Mixing the first filtrate with carbon dioxide results in the formation of carbonic acid and its reaction with sodium hydroxide in the first filtrate to form NaHCO3. Consequently, the pH of the first filtrate decreases. The depletion of NaOH leads the solution toward equilibrium, which results in the dissociation of sodium aluminate into NaOH and Al(OH)3, with the latter precipitating as the second residue. In particular, the reaction may be considered to reach equilibrium when the pH of the first filtrate is approximately 7.0–8.6, preferably approximately 8.3–8.6.

[0037] After mixing, any silica contained in the aluminum scrap may become inert and may no longer be reactive enough to produce ammonia or hydrogen.

[0038] Carbon dioxide may be mixed with the first filtrate at any preferred flow rate. For example, the flow rate may be 9 to 20 kg / min. In particular, the flow rates may be 9 to 18.5 kg / min, 10 to 18 kg / min, 12 to 16 kg / min, 13 to 15 kg / min, or 13.5 to 14 kg / min. More specifically, the flow rate may be 9 to 10 kg / min.

[0039] The mixing of the first filtrate with carbon dioxide may be carried out under preferred conditions. For example, the mixing of the first filtrate with carbon dioxide may be carried out for a preferred period of time. The mixing may be carried out for a predetermined period of time. According to a particular embodiment, the predetermined period may be any preferred time that allows the pH of the first filtrate to be lowered to about 7.0 to 8.6. For example, the predetermined period may be 60 to 180 minutes. In particular, the predetermined period may be 70 to 160 minutes, 75 to 150 minutes, 90 to 120 minutes, or 100 to 110 minutes. More particularly, the predetermined period may be 120 to 135 minutes.

[0040] The mixing of the first filtrate with carbon dioxide may be carried out at a suitable temperature. For example, the mixing may be carried out at a second predetermined temperature. In a particular embodiment, the second predetermined temperature may be 40 to 100°C. In particular, the second predetermined temperature may be 45 to 95°C, 50 to 90°C, 65 to 85°C, 70 to 80°C, or 75 to 78°C. More particularly, the second predetermined temperature may be 55 to 70°C.

[0041] Mixing the first filtrate with carbon dioxide results in the formation of ATH as a residue in the second filtrate. In particular, high-purity ATH may be obtained from this method. In certain embodiments, the purity of ATH may be 70% or higher. In particular, the purity may be 70-90%.

[0042] The method of the present invention may be carried out at any suitable pressure. In particular, the method may be carried out at atmospheric pressure. In this way, the method is safe and contributes to keeping the method economical.

[0043] This method may further include evaporating the second filtrate to form sodium bicarbonate. The evaporation may be any preferred form of evaporation. In particular, the evaporation may include evaporation under reduced pressure.

[0044] In certain embodiments, the method may further include heating sodium bicarbonate to form sodium carbonate. The heating may be carried out at a suitable temperature. For example, the temperature may be 150 to 200°C.

[0045] Overall, the method of the present invention produces ATH, as well as sodium bicarbonate and / or sodium carbonate. Sodium bicarbonate and / or sodium carbonate may be formed as by-products of the method, and they may be used in turn for other purposes. Thus, the method of the present invention not only enables the effective recycling of waste aluminum scrap to obtain ATH for use in the extraction of metallic aluminum, but also enables the production of other useful by-products.

[0046] While the present invention has been described in general terms, the same will be more readily understood by referring to the following embodiments, which are provided as examples and are not intended to be limiting. [Examples]

[0047] Examples Aluminum scrap was obtained, and the oxide layer was ground off from the aluminum scrap. The oxide layer was in powder form and was collected. The scrap powder was chemically analyzed using XRF scanning (LaFarge Aluminates Laboratory). The results of the analysis are shown in Table 1.

[0048] [Table 1]

[0049] Next, approximately 100g of kudzu starch was added to the sodium hydroxide solution in a ratio of approximately 3:2 and stirred steadily. The mixture was maintained at 100°C for 2 hours.

[0050] After 2 hours, a sodium aluminate solution was obtained. The solution was filtered off the reaction oxide residue (ROR) cake. The sodium aluminate solution remained soluble in water and therefore had a concentration of approximately 68%.

[0051] Next, carbon dioxide gas was pumped into the filtered sodium aluminate solution to form carbonic acid and H2CO3. Due to the high alkalinity of the solution, carbonic acid neutralized the NaOH that kept the sodium aluminate soluble. Therefore, the sodium aluminate dissociated back into NaOH and aluminum trihydrate. Since there was insufficient NaOH to keep the aluminum trihydrate soluble, the aluminum trihydrate precipitated as a fluid white precipitate product (WPP). The overall reaction is shown below:

[0052] [ka]

[0053] To investigate the effects of various different conditions on the overall reaction, five different combinations of conditions were implemented as shown in Table 2.

[0054] [Table 2]

[0055] It was observed that stirring and the stoichiometric ratio of carbon dioxide to NaOH pumped into the solution determined which compound structure was formed. In the case of neutralization without stirring and in non-equilibrium, an aggregated crystalline structure of Na2O,Al2O3,CO2,nH2O was formed, which is extremely difficult to physically separate into individual chemically distinct components.

[0056] Next, the obtained WPP and ROR were subjected to various tests as follows:

[0057] 1.1 Weight Analysis of WPP The obtained WPP was filtered and dried in a muffler furnace at 100°C for 2-5 days before analysis. Elemental analysis of the dried WPP was performed using XRF and TOC / TC analysis.

[0058] 1.2 ATH purity, whiteness test, oil absorption test, and moisture content measurement of test runs using the CO2 neutralization method The purity of aluminum trihydrate (ATH) in dry WPP was determined using XRF and TOC / TC analysis. Whiteness testing was performed using the CIE L*a*b color space. Oil absorption testing was performed using ASTM D281-12, and moisture content was measured using TGA analysis.

[0059] 1.3 Chemical composition analysis of test runs using the CO2 neutralization method The purity of aluminum trihydrate in dried WPP was determined using XRF and TOC / TC analysis.

[0060] 1.4 Chemical composition analysis of dried ROR RORs from various orchids were mixed together, and a 100g sample was collected. RORs were analyzed using XRF and TGA / TC methods.

[0061] The results of the above test are as follows:

[0062] Gravimetric analysis of dried reaction oxide residue (ROR) and white precipitate product (WPP) from the test run. Figure 1 shows that the dry ROR weights from the five samples ranged from 58.43g to 64.59g. Despite the identical drying conditions, there was noticeable heterogeneity in drying among all the samples. Figure 2 shows that sample 3 had the lowest WPP weight and highest moisture loss among all the samples.

[0063] ATH purity, oil absorption, whiteness, and moisture content of WPP in the comparative run. Figures 3-6 show that the dried WPP of sample 3 had the highest ATH purity (89.84%, industrial grade) and whiteness (whiteness index of 98.32), as well as the lowest moisture content (3.30%). Its oil absorption test level was also within the range of industrial grade ATH used in paint fillers.

[0064] Chemical composition analysis of WPP from test runs Table 3 shows that CO3 contamination was common. For example, sample 3 had the lowest level of CO3 contamination among all the samples.

[0065] [Table 3]

[0066] Comparison of the chemical composition of aluminum scrap and ROR (Roller of Iron). Table 4 shows the percentage chemical composition of the original waste powder and the reaction oxide residue (ROR) after NaOH extraction. From these results, it was observed that the amount of aluminum oxide decreased by 25.73% after treatment, while CaO increased 13.83 times, BaO increased 17.43 times, and Fe2O3 increased 3.14 times.

[0067] [Table 4]

[0068] While the foregoing description has presented exemplary embodiments, those skilled in the art will understand that many modifications may be made without departing from the present invention.

Claims

1. Method for preparing sodium alumate: - Mixing aluminum scrap with sodium hydroxide at a first predetermined temperature to form a mixture containing the aluminum scrap and sodium hydroxide in a ratio of 1:0.2 to 1:0.7, wherein the aluminum scrap has an aluminum oxide content of 30% or more relative to the total weight of the aluminum scrap; and - The mixture is filtered to obtain a first filtrate containing sodium aluminate and a first residue.

2. The preparation method described above - Diluting the first filtrate with water; and The method according to claim 1, further comprising: - mixing the first filtrate with carbon dioxide at a second predetermined temperature to obtain an aluminum trihydrate (ATH) residue and a second filtrate.

3. The method according to claim 1 or 2, wherein the aluminum scrap has an aluminum oxide content of 60 to 90% relative to the total weight of the aluminum scrap.

4. The method according to any one of claims 1 to 3, wherein the aluminum scrap is powdered aluminum scrap.

5. The aluminum scrap has an average particle size of 0.002 to 10.0 mm, according to any one of claims 1 to 4.

6. The method according to any one of claims 1 to 5, wherein the first predetermined temperature is 50 to 100°C.

7. The method according to claim 2, wherein the dilution includes diluting the first filtrate at a dilution ratio of 1.5 to 4.

8. The method according to claim 2, wherein mixing the first filtrate with carbon dioxide includes introducing carbon dioxide into the first filtrate at a flow rate of 9 to 20 kg / min.

9. The method according to claim 2, wherein the second predetermined temperature is 40 to 100°C.

10. The method according to claim 2, wherein mixing the first filtrate with carbon dioxide includes introducing carbon dioxide into the first filtrate for 60 to 180 minutes.

11. The method according to claim 2, wherein mixing the first filtrate with carbon dioxide lowers the pH of the first filtrate to 7.0 to 8.

6.

12. The method according to any one of claims 1 to 11, performed at atmospheric pressure.

13. The method according to claim 2, further comprising evaporating the second filtrate to form sodium bicarbonate.

14. The method according to claim 13, wherein the evaporation includes evaporation under reduced pressure.

15. The method according to any one of claims 13 and 14, further comprising heating the sodium bicarbonate to form sodium carbonate.

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