Method for jointly extracting gallium from coal gangue and bauxite waste residues

Abstract

The invention discloses an extraction method for extracting gallium from waste residues of coal gangue and bauxite, which is characterized in that metal elements such as gallium and aluminum in the waste residues can be uniformly distributed through powdering and proper mixing, ammonium sulfate is added in the roasting process, so that not only is the separation and release of gallium and aluminum realized, but also the generated ammonium sulfate gas is cooled, crystallized and recycled, and the production cost is reduced. According to the method, the process cost is reduced, acid leaching, alkaline leaching and composite extraction are adopted step by step, it is ensured that gallium is efficiently enriched and separated in all procedures, gallium oxide with the purity larger than or equal to 99.5% is finally obtained, meanwhile, residual silicon-rich residues and bauxite residues are subjected to hydrothermal crystallization to prepare molecular sieves, comprehensive utilization of waste residues is achieved, and obvious economic and environment-friendly benefits are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of metal extraction from coal gangue, and in particular to a method for jointly extracting gallium from coal gangue and bauxite waste residue. Background Art

[0002] Gallium, as a core element in modern semiconductors, optoelectronic materials, and new energy, continues to see growing global demand. However, in nature, gallium mostly occurs in isomorphous forms in minerals such as bauxite and coal gangue, and independent deposits are scarce. Approximately 90% of gallium needs to be recovered from aluminum smelting slag or coal-based solid waste. Bauxite slag and coal gangue, as typical industrial solid wastes, contain components such as gallium, aluminum, silicon, and iron, and are important carriers of gallium resources.

[0003] The conventional process for extracting gallium from solid waste includes pretreatment, acid leaching, solid-liquid separation, and extraction. After the waste is crushed and homogenized, the gallium is leached with sulfuric acid or hydrochloric acid at high temperature. The solid-liquid separation is then achieved by filtration, and the gallium-containing solution is extracted and separated from the organic solvent. The solution is then purified by precipitation and crystallization. However, the existing process has several problems that need to be solved:

[0004] First, current technologies mainly focus on the extraction of gallium from single solid wastes such as electrolytic aluminum slag and fly ash, while there is a lack of research on the synergistic extraction of gallium from typical industrial solid wastes such as bauxite slag and coal gangue. In particular, the possible leaching synergy and mechanism between different solid wastes have not been deeply explored. Secondly, most studies only focus on the efficient extraction of gallium, and pay insufficient attention to the comprehensive utilization of high-silicon waste slag (SiO2 content usually exceeds 60%) produced after gallium extraction. If such waste slag is directly stored, it will not only waste silicon resources, but may also cause environmental risks. In addition, there is currently little research on the synergistic treatment of bauxite waste slag and coal gangue, and the interactive influence of aluminum, silicon, iron and other components in the two types of waste slag has not yet been clarified. For example, although the existing published patent CN110172597A involves the extraction of scandium from coal gangue, it does not involve the joint extraction of gallium, and the technical route lacks versatility. Summary of the Invention

[0005] The object of the present invention is to provide a method for jointly extracting gallium from coal gangue and bauxite waste residue to solve the problems raised in the above background technology.

[0006] To achieve the above object, the present invention provides the following technical solution: a method for extracting gallium from coal gangue and bauxite waste residue, comprising the following steps:

[0007] Step S1: crushing coal gangue and bauxite into powder and mixing them, adding ammonium sulfate to the mixed powder at a mixing mass ratio of 1:2-2.5, and roasting at 400-500°C for 2-4 hours to release gallium and aluminum.

[0008] Step S2: reacting the calcined slag with hydrochloric acid to obtain an aluminum gallium-containing acid leaching solution and a silicon-rich residue after solid-liquid separation;

[0009] Step S3: Precipitating aluminum hydroxide from the aluminum gallium-containing acid leaching solution and separating to obtain a gallium-rich filtrate;

[0010] Step S4: selecting a kerosene solution containing octadecyl catechol and benzo-15-crown-5 as a composite extractant, extracting the gallium-rich filtrate through a countercurrent extraction device, and controlling the flow ratio of the organic phase to the aqueous phase to be 1:2-1:3;

[0011] Step S5: using 1.0-1.8 mol / L hydrochloric acid to strip the gallium-loaded organic phase, concentrating it, and then oxidizing and roasting it to produce gallium oxide with a purity of ≥99.5%;

[0012] Step S6: The remaining silicon-rich residue is mixed with bauxite slag and then hydrothermally crystallized to synthesize molecular sieves. The acid leaching waste liquid is supplemented with sodium hydroxide and then reused in the step S3.

[0013] Preferably, in step S1, the gangue and bauxite are both crushed to below 200 mesh.

[0014] Preferably, in step S1, the gangue powder and the bauxite powder are mixed in a mass ratio of 1:1-2.

[0015] Preferably, in step S2, the calcined slag is reacted with 15%-20% hydrochloric acid at 80-110° C. for 1-2 hours.

[0016] Preferably, in step S3, a flocculant is added to the aluminum gallium-containing acid leaching solution during precipitation, the solution is allowed to stand for 30 minutes, and the pH value is adjusted to 5.0-5.5.

[0017] Preferably, in step S4, the countercurrent extraction temperature of the gallium-rich filtrate is 25-40° C., and the number of extraction stages is 3-5.

[0018] Preferably, in step S5, the stripping time is 20-30 minutes, and the extraction agent is recycled ≥15 times.

[0019] Preferably, in step S6, the hydrothermal crystallization conditions are: reaction temperature 180-220°C, reaction time 4-8 hours, the molecular sieve product is type 4A, and the specific surface area is ≥500m 2 / g.

[0020] Preferably, in step S1, the ammonium sulfate gas generated during the roasting process is cooled and crystallized and then recovered and regenerated, and the regenerated ammonium sulfate powder is reused in step S1.

[0021] Preferably, in S4, the countercurrent extraction equipment is a stirred sieve plate tower, vortex blades and sieve plates are provided in the tower, the stirring speed is 200-400 rpm, and the two-phase contact time is 10-15 minutes.

[0022] Compared with the prior art, the present invention has the following beneficial effects: by pulverizing and appropriately mixing coal gangue and bauxite, the present invention can evenly distribute metal elements such as gallium and aluminum in the waste slag, and by adding ammonium sulfate during the roasting process, not only can the gallium and aluminum be separated and released, but the generated ammonium sulfate gas can also be recovered and reused through cooling and crystallization, thereby reducing process costs. Acid leaching, alkaline leaching and composite extraction are adopted in steps to ensure efficient enrichment and separation of gallium in each process, ultimately obtaining gallium oxide with a purity of ≥99.5%. In addition, the remaining silicon-rich residue and bauxite slag are hydrothermally crystallized to prepare molecular sieves, thereby realizing the comprehensive utilization of the waste slag and having significant economic and environmental benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The figure is a flow chart of a method for jointly extracting gallium from coal gangue and bauxite waste slag according to an embodiment of the present invention.

[0024] Figure 2 This is a scanning electron microscope image of gallium oxide extracted from bauxite slag in the method for jointly extracting gallium from coal gangue and bauxite waste slag in an embodiment of the present invention.

[0025] Figure 3 This is a scanning electron microscope image of gallium oxide extracted from coal gangue slag in the method for jointly extracting gallium from coal gangue and bauxite waste slag according to an embodiment of the present invention. DETAILED DESCRIPTION

[0026] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. 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 making creative efforts are within the scope of protection of the present invention.

[0027] An embodiment of the present invention provides a method for jointly extracting gallium from coal gangue and bauxite waste residue, comprising the following steps:

[0028] Step S1: crushing coal gangue and bauxite into powder and mixing them, adding ammonium sulfate to the mixed powder at a mixing mass ratio of 1:2-2.5, and roasting at 400-500°C for 2-4 hours to release gallium and aluminum;

[0029] Step S2: reacting the calcined slag with hydrochloric acid to obtain an aluminum gallium acid leaching solution and a silicon-rich residue after solid-liquid separation (refer to Figure 1 and Figure 2 );

[0030] Step S3: Precipitating aluminum hydroxide from the aluminum gallium-containing acid leaching solution and separating to obtain a gallium-rich filtrate;

[0031] Step S4: selecting a kerosene solution containing octadecyl catechol and benzo-15-crown-5 as a composite extractant, extracting the gallium-rich filtrate through a countercurrent extraction device, and controlling the flow ratio of the organic phase to the aqueous phase to be 1:2-1:3;

[0032] Step S5: using 1.0-1.8 mol / L hydrochloric acid to strip the gallium-loaded organic phase, concentrating it, and then oxidizing and roasting it to produce gallium oxide with a purity of ≥99.5%;

[0033] Step S6: The remaining silicon-rich residue is mixed with bauxite slag and then hydrothermally crystallized to synthesize molecular sieves. The acid leaching waste liquid is supplemented with sodium hydroxide and then reused in step S3.

[0034] Specifically, in step S1, the gangue and bauxite are both crushed to below 200 mesh, and the gangue powder and bauxite powder are mixed at a mass ratio of 1:1-2.

[0035] It should be noted that in step S1, the ammonium sulfate gas generated during the roasting process is cooled and crystallized and then recovered and regenerated, and the regenerated ammonium sulfate powder is reused in step S1.

[0036] Specifically, in step S2, the calcined slag is reacted with 15%-20% hydrochloric acid at 80-110° C. for 1-2 hours.

[0037] Specifically, in step S3, a flocculant is added to the aluminum gallium-containing acid leaching solution during precipitation, the solution is allowed to stand for 30 minutes, and the pH value is adjusted to 5.0-5.5.

[0038] Specifically, in step S4, the countercurrent extraction equipment is a stirred sieve plate tower, in which vortex blades and sieve plates are arranged, the stirring speed is 200-400 rpm, the two-phase contact time is 10-15 minutes, the extraction temperature of the countercurrent extraction of the gallium-rich filtrate is 25-40°C, and the extraction stage is 3-5.

[0039] Specifically, in step S5, the stripping time is 20-30 minutes, and the extraction agent is recycled ≥15 times.

[0040] Specifically, in step S6, the hydrothermal crystallization conditions are: reaction temperature 180-220°C, reaction time 4-8 hours, the molecular sieve product is type 4A, and the specific surface area is ≥500m 2 / g.

[0041] Example 1

[0042] Step S1: Grind the gangue and bauxite into powders below 200 mesh respectively, mix them in a mass ratio of 1:1, add ammonium sulfate to the mixed powder, place it in a roasting furnace, and roast it at 400°C for 2 hours. The ammonium sulfate gas generated during the roasting process is condensed, recovered and crystallized, and the regenerated ammonium sulfate powder is reused.

[0043] Step S2: mixing the calcined slag with 15% hydrochloric acid, reacting at 80° C. for 1 hour, and then performing solid-liquid separation to obtain an aluminum gallium-containing acid leaching solution and a silicon-rich residue.

[0044] Step S3: Aluminum hydroxide is precipitated from the aluminum gallium-containing acid leaching solution, and a gallium-rich filtrate is obtained by separation. A flocculant is added during precipitation, and the mixture is allowed to stand for 30 minutes, and the pH value is adjusted to 5.0.

[0045] Step S4: A kerosene solution containing octadecyl catechol and benzo-15-crown-5 was selected as a composite extractant, and a stirred sieve plate tower was used. The tower was equipped with vortex blades and sieve plates. The stirring speed was 200 rpm, the two-phase contact time was 10 minutes, the extraction temperature of the countercurrent extraction of the gallium-rich filtrate was 25-40°C, and the number of extraction stages was 3.

[0046] Step S5: 1.0 mol / L hydrochloric acid is used to strip the gallium-loaded organic phase for 20 minutes. The stripping solution is concentrated and then oxidized and roasted to obtain gallium oxide with a purity of 99.5%. The extractant is recycled 15 times.

[0047] Step S6: Silicon-rich residue and bauxite slag were mixed in a mass ratio of 1:1, deionized water was added to prepare the slurry, and hydrothermal crystallization was carried out at 180°C for 4 hours to synthesize 4A molecular sieve with a specific surface area of 520m 2 / g, and the acid leaching waste liquid is supplemented with sodium hydroxide and then reused in step S3.

[0048] Example 2

[0049] Step S1: Grind the gangue and bauxite into powders below 200 mesh respectively, mix them in a mass ratio of 1:2, add ammonium sulfate to the mixed powder, place it in a roasting furnace, and roast it at 400°C for 2 hours. The ammonium sulfate gas generated during the roasting process is condensed, recovered and crystallized, and the regenerated ammonium sulfate powder is reused.

[0050] Step S2: mixing the calcined slag with 18% hydrochloric acid, reacting at 95° C. for 1.5 hours, and then performing solid-liquid separation to obtain an aluminum gallium-containing acid leaching solution and a silicon-rich residue.

[0051] Step S3: Aluminum hydroxide is precipitated from the aluminum gallium-containing acid leaching solution to separate and obtain a gallium-rich filtrate. A flocculant is added during precipitation and the mixture is allowed to stand for 30 minutes, and the pH value is adjusted to 5.2.

[0052] Step S4: A kerosene solution containing octadecyl catechol and benzo-15-crown-5 was selected as a composite extractant, and a stirred sieve plate tower was used. The tower was equipped with vortex blades and sieve plates. The stirring speed was 300 rpm, the two-phase contact time was 12 minutes, the extraction temperature of the countercurrent extraction of the gallium-rich filtrate was 30°C, and the extraction stage was 4.

[0053] Step S5: 1.4 mol / L hydrochloric acid is used to strip the gallium-loaded organic phase for 25 minutes. The stripping solution is concentrated and then oxidized and roasted to obtain gallium oxide with a purity of 99.6%. The extractant is recycled 18 times.

[0054] Step S6: Silicon-rich residue and bauxite slag were mixed in a mass ratio of 1:1, deionized water was added to prepare the slurry, and hydrothermal crystallization was carried out at 200°C for 6 hours to synthesize 4A molecular sieve with a specific surface area of 580m 2 / g, and the acid leaching waste liquid is supplemented with sodium hydroxide and then reused in step S3.

[0055] Example 3

[0056] Step S1: Coal gangue and bauxite are crushed into powders below 200 mesh respectively, mixed in a mass ratio of 1:2.5, ammonium sulfate is added to the mixed powder, and placed in a roasting furnace, roasted at 500°C for 4 hours. The ammonium sulfate gas generated during the roasting process is condensed, recovered and crystallized, and the regenerated ammonium sulfate powder is reused.

[0057] Step S2: mixing the calcined slag with 20% hydrochloric acid, reacting at 110° C. for 2 hours, and then performing solid-liquid separation to obtain an aluminum gallium-containing acid leaching solution and a silicon-rich residue.

[0058] Step S3: Aluminum hydroxide is precipitated from the aluminum gallium-containing acid leaching solution, and a gallium-rich filtrate is obtained by separation. A flocculant is added during precipitation, and the mixture is allowed to stand for 30 minutes, and the pH value is adjusted to 5.5.

[0059] Step S4: A kerosene solution containing octadecyl catechol and benzo-15-crown-5 was selected as a composite extractant, and a stirred sieve plate tower was used. The tower was equipped with vortex blades and sieve plates. The stirring speed was 400 rpm, the two-phase contact time was 15 minutes, the extraction temperature of the countercurrent extraction of the gallium-rich filtrate was 40°C, and the extraction stage was 4.

[0060] Step S5: 1.8 mol / L hydrochloric acid is used to strip the gallium-loaded organic phase for 30 minutes. The stripping solution is concentrated and then oxidized and roasted to obtain gallium oxide with a purity of 99.8%. The extractant is recycled 20 times.

[0061] Step S6: Silicon-rich residue and bauxite slag were mixed in a mass ratio of 1:1, deionized water was added to prepare the slurry, and hydrothermal crystallization was carried out at 220°C for 8 hours to synthesize 4A molecular sieve with a specific surface area of 600m 2 / g, and the acid leaching waste liquid is supplemented with sodium hydroxide and then reused in step S3.

[0062] Comparative Example

[0063] The comparative experiment used acid leaching precipitation method to extract gallium without adding ammonium sulfate for roasting, and the extractant was a single P204 kerosene solution.

[0064] A gallium extraction performance comparison experiment was conducted using the process flow of the method for jointly extracting gallium from coal gangue and bauxite waste slag provided in the embodiment of the present invention and the process flow of extracting gallium by the acid leaching precipitation method provided in the comparative example.

[0065] Table 1 is a comparison of gallium extraction performance

[0066] project Example 1 Example 2 Example 3 Comparative Example Gallium leaching rate (%) 88 91 92 72 Extraction rate (%) 96 97.5 98.5 80 Gallium oxide purity (%) 99.5 99.6 99.8 95 <![CDATA[Specific surface area of molecular sieve (m 2 / g)]]> 520 580 600 Not synthesized

[0067] According to the results in Table 1, the gallium leaching rate of Example 3 is the highest, and the comparative example is the lowest. The extraction rate of Example 3 is close to 99%, which is significantly better than the comparative example. The gallium oxide purity of Examples 1 to 3 exceeds 95%, while the comparative example is only 95%. The molecular sieve synthesized in Example 3 has the best performance in terms of molecular sieve specific surface area. The present invention significantly improves the gallium extraction efficiency and product purity through ammonium sulfate roasting activation, composite extractant optimization and waste residue resource utilization, while realizing the high-value conversion of waste residue into molecular sieve. The process is environmentally friendly and economical. Example 3 has the best comprehensive performance and is suitable for large-scale production.

[0068] Furthermore, in order to verify the economic and environmental advantages of the method for jointly extracting gallium from coal gangue and bauxite waste provided in the embodiment of the present invention, the following comparative experiments were carried out. In step S1 of Examples 1 to 3, the initial charge amounts of coal gangue, bauxite and ammonium sulfate were accurately weighed, and the unreacted ammonium sulfate gas was recovered by condensation after roasting, and the actual consumption was calculated. In step S2, the initial amount of hydrochloric acid added and the volume of the residual liquid after the reaction were recorded, and the actual consumption of hydrochloric acid was determined by titration. In step S3, the acid leaching waste liquid was recycled after being supplemented with sodium hydroxide, and the sodium ion concentration in the waste liquid was analyzed by ion chromatography to calculate the circulation efficiency. In step S6, the silicon-rich residue and bauxite slag were mixed in proportion, and the crystal form and specific surface area of the molecular sieve were characterized by XRD and BET.

[0069] Table 2 is a comparison of the economic and environmental performance of the process flow

[0070] project Example 1 Example 2 Example 3 Comparative Example Ammonium sulfate consumption (kg / t) 120 110 105 0 (unused) <![CDATA[Dosage of hydrochloric acid (m 3 / t)]]> 3.5 3.2 3.0 5.8 Sodium hydroxide circulation rate (%) 85 90 95 40 Waste residue utilization rate (%) 100 100 100 20 (Landfill disposal) Energy consumption (kWh / t) 850 820 800 1200 <![CDATA[CO2 emissions (t / t)]]> 0.8 0.75 0.7 1.5

[0071] According to the results in Table 2, in Examples 1 to 3, the consumption of ammonium sulfate by roasting activated gangue and bauxite was 120 kg / t, 110 kg / t, and 105 kg / t, respectively, and the gas recovery rate was ≥85%. In the comparative example, ammonium sulfate was not used, and direct acid leaching resulted in a hydrochloric acid consumption of up to 5.8 m3. 3 / t, after the silicon-rich residue and bauxite slag are hydrothermally synthesized into molecular sieves, the waste residue utilization rate of Examples 1 to 3 reaches 100%. In the traditional process, 80% of the waste residue needs to be landfilled. By optimizing the countercurrent extraction parameters, the energy consumption of Example 3 is reduced to 800kWh / t, and the CO2 emission is 0.7t / t, which is 53% less than that of the comparative example (1.5t / t).

[0072] In summary, the present invention achieves uniform distribution of metal elements such as gallium and aluminum in the waste residue by pulverizing and appropriately mixing coal gangue and bauxite. The addition of ammonium sulfate during the roasting process not only achieves the separation and release of gallium and aluminum, but also recovers and reuses the generated ammonium sulfate gas through cooling and crystallization, reducing process costs. The step-by-step adoption of acid leaching, alkaline leaching, and composite extraction ensures efficient enrichment and separation of gallium in each process, ultimately obtaining gallium oxide with a purity of ≥99.5%. In addition, the remaining silicon-rich residue and bauxite slag are hydrothermally crystallized to prepare molecular sieves, achieving comprehensive utilization of the waste residue and having significant economic and environmental benefits.

[0073] Parts not described in the present invention are the same as those in the prior art or can be implemented using the prior art. Although the embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations may be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for extracting gallium from coal gangue and bauxite waste residue, characterized in that: The following steps are involved: Step S1: crushing coal gangue and bauxite into powder and mixing them, adding ammonium sulfate to the mixed powder at a mixing mass ratio of 1:2-2.5, and roasting at 400-500°C for 2-4 hours to release gallium and aluminum; Step S2: reacting the calcined slag with hydrochloric acid to obtain an aluminum gallium-containing acid leaching solution and a silicon-rich residue after solid-liquid separation; Step S3: Precipitating aluminum hydroxide from the aluminum gallium-containing acid leaching solution and separating to obtain a gallium-rich filtrate; Step S4: selecting a kerosene solution containing octadecyl catechol and benzo-15-crown-5 as a composite extractant, extracting the gallium-rich filtrate through a countercurrent extraction device, and controlling the flow ratio of the organic phase to the aqueous phase to be 1:2-1:3; Step S5: using 1.0-1.8 mol / L hydrochloric acid to strip the gallium-loaded organic phase, concentrating it, and then oxidizing and roasting it to produce gallium oxide with a purity of ≥99.5%; Step S6: The remaining silicon-rich residue is mixed with bauxite slag and then hydrothermally crystallized to synthesize molecular sieves. The acid leaching waste liquid is supplemented with sodium hydroxide and then reused in the step S3.

2. The method for extracting gallium from coal gangue and bauxite waste according to claim 1, characterized in that: In step S1, the gangue and bauxite are both crushed to a size of less than 200 mesh.

3. The method for extracting gallium from coal gangue and bauxite waste according to claim 1, characterized in that: In the step S1, the gangue powder and the bauxite powder are mixed in a mass ratio of 1:1-2.

4. The method for extracting gallium from coal gangue and bauxite waste residue according to claim 1, characterized in that: In the step S2, the calcined slag is reacted with 15%-20% hydrochloric acid at 80-110° C. for 1-2 hours.

5. The method for extracting gallium from coal gangue and bauxite waste residue according to claim 1, characterized in that: In the step S3, a flocculant is added to the aluminum gallium acid leaching solution during precipitation, and the solution is allowed to stand for 30 minutes, and the pH value is adjusted to 5.0-5.

5.

6. The method for extracting gallium from coal gangue and bauxite waste residue according to claim 1, characterized in that: In step S4, the countercurrent extraction of the gallium-rich filtrate is performed at an extraction temperature of 25-40° C. and the number of extraction stages is 3-5.

7. The method for extracting gallium from coal gangue and bauxite waste residue according to claim 1, characterized in that: In step S5, the stripping time is 20-30 minutes, and the extraction agent is recycled ≥15 times.

8. The method for extracting gallium from coal gangue and bauxite waste residue according to claim 1, characterized in that: In step S6, the hydrothermal crystallization conditions are: reaction temperature 180-220°C, reaction time 4-8 hours, the molecular sieve product is type 4A, and the specific surface area is ≥500m 2 / g.

9. The method for extracting gallium from coal gangue and bauxite waste residue according to claim 1, characterized in that: In step S1, the ammonium sulfate gas generated during the roasting process is cooled and crystallized before being recovered and regenerated, and the regenerated ammonium sulfate powder is reused in step S1.

10. The method for extracting gallium from coal gangue and bauxite waste residue according to claim 1, characterized in that: In S4, the countercurrent extraction equipment is a stirred sieve plate tower, in which vortex blades and sieve plates are arranged, the stirring speed is 200-400 rpm, and the two-phase contact time is 10-15 minutes.

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