Green resource extraction method for metal gallium in coal-series solid waste

Abstract

The invention discloses a green resource extraction method of metal gallium in coal-series solid waste, gallium element in waste is fully released through high-temperature activation and acid leaching dissolution, efficient selective enrichment of gallium is realized by adopting an ion imprinting modified persimmon peel adsorbent, high recovery rate in subsequent procedures is ensured, and the method is suitable for industrial production. And the high-purity metal gallium is recovered by utilizing a resin secondary enrichment and electrolytic refining technology, so that the process complexity and the equipment cost are reduced, the acid leaching residues can be converted into silica powder and aluminum oxide after being processed and treated, the resource utilization of wastes is realized, and the environmental pollution is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of extraction of metallic gallium from solid waste, and in particular to a green resource extraction method for metallic gallium from coal-based solid waste. Background Art

[0002] Gallium is a rare metal widely used in high-tech fields such as electronics, optoelectronics, semiconductors, and solar energy. However, due to its scarcity and difficulty in recycling, efficient gallium recovery has become a research hotspot in the field of metal resource extraction.

[0003] Coal-based solid waste is a type of solid waste associated with gallium and other metals, with complex composition and large accumulation. The existing process is mostly a combination of "acid leaching-enrichment-electrolysis": the acid leaching process relies on high-concentration acid or high temperature and high pressure, resulting in high acid and energy consumption, and the introduction of Fe 3+ 、Al 3+ impurities; the enrichment stage is mainly based on solvent extraction or ion exchange resin. The former is prone to emulsification, loss of organic phase, and difficulty in regeneration, while the latter has poor selectivity and is interfered by coexisting metals; the accumulation of impurities in electrolytic refining requires frequent replacement of the electrolyte, which increases the environmental and cost burden.

[0004] The high-silicon (SiO2>60%) waste slag produced after acid leaching is not effectively utilized, and long-term storage may cause heavy metal leaching and dust pollution. Although co-precipitation and pH-step precipitation can remove impurities, they have strict requirements for pH and temperature control, which can easily lead to gallium co-precipitation losses. At the same time, most existing technologies focus on the extraction of single metals (such as gallium), ignoring the coordinated recovery and comprehensive utilization of metals such as aluminum, iron, and silicon in coal-based solid waste. The resource utilization rate is low, and there is a lack of efficient waste slag resource means, making it difficult to meet the current requirements of green and low-carbon development. Summary of the Invention

[0005] The purpose of the present invention is to provide a green resource extraction method for metallic gallium from coal-based solid waste to solve the problems raised in the above background technology.

[0006] According to one aspect of the present application, a green resource extraction method for metallic gallium from coal-based solid waste comprises the following steps:

[0007] Step 1: Grind fly ash and coal gangue in coal-based solid waste to a particle size of 0.02-0.1 mm, and activate at a high temperature of 200-300°C for 1-2 hours to obtain activated coal-based solid waste raw materials;

[0008] Step 2: Mix the activated coal-based solid waste with an acid solution at an acid concentration of 10% to 30% and a liquid-to-solid ratio of 3:1-5:1, and react at 80-120° C. for 2-4 hours to obtain a gallium-containing acid leaching solution;

[0009] Step 3: selectively adsorbing gallium from the gallium-containing acid leaching solution using an ion-imprinted persimmon peel adsorbent, with the adsorption column operating at a flow rate of 5-15 BV / h and an adsorption temperature of 35-55°C. After adsorption saturation, the adsorption column is eluted with a 1 mol / L hydrochloric acid solution to release the adsorbed gallium ions, thereby obtaining a gallium-containing acidic desorption solution;

[0010] Step 4: The gallium-containing acidic desorption liquid is subjected to secondary enrichment through a leaching resin or a chelating resin to desorb the hydrochloric acid-thiourea mixed solution to obtain a high-concentration gallium solution;

[0011] Step 5: Add the high-concentration gallium solution to the sodium hydroxide electrolyte, the concentration of the sodium hydroxide electrolyte is 15% to 30%, and perform electrolysis with the metal material as the cathode and anode, and deposit metallic gallium at the cathode;

[0012] Step 6: washing and drying the acid leaching residue from step 2, mixing it with sodium silicate at a mass ratio of 1:2-1:3, and calcining it at 1200-1400° C. to prepare silicon micropowder;

[0013] Sodium hydroxide is added to the effluent of the adsorption column to adjust the pH to 4-5, aluminum hydroxide is precipitated, and aluminum oxide is prepared by calcination.

[0014] Preferably, in step 6, air is introduced into the effluent of the adsorption column in step 3, the pH is adjusted to 3-4, and the precipitated iron element is calcined to prepare iron oxide.

[0015] Preferably, in step 4: the preparation method of the hydrochloric acid-thiourea mixed solution is:

[0016] After diluting concentrated hydrochloric acid to 1.5 mol / L, add thiourea at a molar ratio of thiourea to hydrochloric acid of 1:50 and stir until completely dissolved;

[0017] The volume ratio of the hydrochloric acid-thiourea mixed solution to the resin is 3:1-5:1, and the desorption temperature is 40-60°C.

[0018] Preferably, in step 6, the preparation of the silicon micropowder comprises: mixing the acid leaching residue and sodium silicate in a mass ratio of 1:2.5, and calcining at 1300° C. for 2 hours to obtain silicon micropowder;

[0019] The preparation of the aluminum oxide comprises: adding sodium hydroxide to the aluminum-containing filtrate to a pH of 4.5, precipitating aluminum hydroxide, and then calcining at 900° C. for 3 hours to obtain the aluminum oxide.

[0020] Preferably, in step 2, the activated coal-based solid waste raw material is mixed with hydrochloric acid for acid leaching and dissolution, the hydrochloric acid concentration is 20%, the liquid-solid ratio is 4:1, the reaction temperature is 100° C., and the reaction time is 3 hours.

[0021] Preferably, in step 5, the high-concentration gallium solution is added to an alkaline electrolyte for electrolysis, and the concentration of sodium hydroxide in the alkaline electrolyte used is 20%.

[0022] Preferably, in step 5, during the electrolysis process, the electrolysis current density is 50-100 A / m 2 , the electrolysis time is 4-6h.

[0023] Preferably, in step 6, during the preparation of the silicon micropowder, the mass ratio of acid leaching residue to sodium silicate is 1:2.5, and the silicon micropowder is calcined at 1200-1400° C. for 3 hours, and the particle size of the silicon micropowder is 0.5-3 μm.

[0024] Preferably, in the hydrochloric acid-thiourea mixed solution, the added amount of thiourea is 0.5% to 2% of the molar amount of hydrochloric acid.

[0025] Compared with the existing technology, the beneficial effects of the present invention are: the present invention fully releases the gallium element in the waste through high-temperature activation and acid leaching dissolution, adopts ion-imprinted modified persimmon peel adsorbent to achieve efficient and selective enrichment of gallium, ensuring a high recovery rate in subsequent processes, and utilizes resin secondary enrichment and electrolytic refining technology to recover high-purity metallic gallium, thereby reducing process complexity and equipment costs. The acid leaching residue can be converted into silicon micropowder and alumina after processing, realizing waste resource utilization and reducing environmental pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a flow chart of a green resource extraction method for metallic gallium from coal-based solid waste according to an embodiment of the present invention;

[0027] Figure 2 This is a scanning electron microscope photograph of the persimmon peel imprinted adsorbent after adsorption of gallium-containing acid leaching solution in the green resource extraction method of metallic gallium from coal-based solid waste according to an embodiment of the present invention;

[0028] Figure 3 This is a scanning electron microscope photograph of a persimmon peel imprinted adsorbent in the green resource extraction method for metallic gallium from coal-based solid waste according to an embodiment of the present invention. DETAILED DESCRIPTION

[0029] 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.

[0030] See also Figure 1According to one embodiment of the present invention, a green resource extraction method for metallic gallium from coal-based solid waste is provided, comprising the following steps: Step 1: crushing fly ash and coal gangue in the coal-based solid waste to a particle size of 0.02-0.1 mm, and activating them at a high temperature of 200-300°C for 1-2 hours to obtain activated coal-based solid waste raw materials;

[0031] Step 2: Mix the activated coal-based solid waste with an acid solution at an acid concentration of 10% to 30% and a liquid-to-solid ratio of 3:1-5:1, and react at 80-120° C. for 2-4 hours to obtain a gallium-containing acid leaching solution;

[0032] Step 3: selectively adsorbing gallium from the gallium-containing acid leaching solution using an ion-imprinted persimmon peel adsorbent, with the adsorption column operating at a flow rate of 5-15 BV / h and an adsorption temperature of 35-55°C. After adsorption saturation, the adsorption column is eluted with a 1 mol / L hydrochloric acid solution. After repeated use 10 times, the adsorption capacity retention rate is greater than 85%, and the adsorbed gallium ions are released to obtain a gallium-containing acidic desorption solution;

[0033] Step 4: The gallium-containing acidic desorption liquid is secondary enriched by a leaching resin or a chelating resin, and desorbed by a hydrochloric acid-thiourea mixed solution to obtain a high-concentration gallium solution;

[0034] Step 5: Add sodium hydroxide electrolyte to the high-concentration gallium solution, where the concentration of the sodium hydroxide electrolyte is 15% to 30%, and perform electrolysis using the metal material as the cathode and anode to deposit metallic gallium at the cathode;

[0035] Step 6: washing and drying the acid leaching residue from step 2, mixing it with sodium silicate at a mass ratio of 1:2-1:3, and calcining it at 1200-1400° C. to prepare silicon micropowder;

[0036] In step 3, sodium hydroxide is added to the effluent of the adsorption column to adjust the pH to 4-5, aluminum hydroxide is precipitated, and aluminum oxide is prepared by calcination.

[0037] Furthermore, in step 6, the acid leaching residue is washed with water and then dried at 110° C. for 5 hours until the water content is less than 2%, and 0.5%-1% by mass of polyethylene glycol is added as a dispersant. After calcination, the particle size distribution of the silicon micropowder is 0.5-3 μm, and the purity is ≥98.5%.

[0038] Specifically, in step 6, air is introduced into the effluent of the adsorption column in step 3, the pH is adjusted to 3-4, and the iron element is precipitated and calcined to prepare iron oxide.

[0039] Specifically, in step 4: the preparation method of the hydrochloric acid-thiourea mixed solution is:

[0040] After diluting concentrated hydrochloric acid to 1.5 mol / L, add thiourea at a molar ratio of thiourea to hydrochloric acid of 1:50 and stir until completely dissolved;

[0041] The volume ratio of the hydrochloric acid-thiourea mixed solution to the resin is 3:1-5:1, and the desorption temperature is 40-60°C.

[0042] Specifically, in step 6, the preparation of silicon micropowder includes: mixing the acid leaching residue and sodium silicate in a mass ratio of 1:2.5, and calcining at 1300° C. for 2 hours to obtain silicon micropowder;

[0043] The preparation of aluminum oxide includes: adding sodium hydroxide to the aluminum-containing filtrate to pH=4.5, precipitating aluminum hydroxide, and calcining at 900° C. for 3 hours to obtain aluminum oxide.

[0044] Specifically, in step 2, the activated coal-based solid waste raw material is mixed with hydrochloric acid for acid leaching and dissolution, the hydrochloric acid concentration is 20%, the liquid-solid ratio is 4:1, the reaction temperature is 100° C., and the reaction time is 3 hours.

[0045] Specifically, in step 5, the high-concentration gallium solution is added to an alkaline electrolyte for electrolysis, and the concentration of sodium hydroxide in the alkaline electrolyte used is 20%.

[0046] Specifically, in step 5, during the electrolysis process, the electrolysis current density is 50-100 A / m 2 , the electrolysis time is 4-6h.

[0047] Specifically, in step 6, during the preparation of the silicon micropowder, the mass ratio of the acid leaching residue to the sodium silicate is 1:2.5, and the silicon micropowder is calcined at 1200-1400° C. for 3 hours, and the particle size of the silicon micropowder is 0.5-3 μm.

[0048] Specifically, in the hydrochloric acid-thiourea mixed solution, the added amount of thiourea is 0.5% to 2% of the molar amount of hydrochloric acid.

[0049] Example 1

[0050] Step 1: Grind the fly ash and coal gangue in the coal-based solid waste to a particle size of 0.02-0.1 mm, place the crushed coal-based solid waste in a muffle furnace, heat it to 250°C at a heating rate of 5°C / min, and activate it at a constant temperature for 1.5 hours. After activation, the material is cooled to room temperature to obtain an activated coal-based solid waste raw material with a porous structure.

[0051] Step 2: The activated solid waste raw material is mixed with 20% hydrochloric acid solution at a liquid-solid ratio of 4:1, heated to 100° C. in a reactor, and stirred for reaction for 3 hours. After the reaction is completed, a gallium-containing acid leaching solution is obtained.

[0052] Step 3: The ion-imprinted modified persimmon peel adsorbent is loaded into the adsorption column, activated with 1 mol / L hydrochloric acid and rinsed to neutrality. The acid extract is passed through the adsorption column at a flow rate of 12 BV / h and a temperature of 45°C. It is eluted with 1.2 mol / L hydrochloric acid at a flow rate of 6 BV / h to obtain a gallium-containing desorption solution with a concentration of approximately 1000 mg / L. The arsenic in the effluent of the adsorption column is <0.1 mg / L, mercury is <0.05 mg / L, and lead is <0.2 mg / L.

[0053] Step 4: The leaching resin is activated with 5% hydrochloric acid and rinsed with deionized water until neutral. The gallium-containing desorption solution is passed through the resin column at a flow rate of 8 BV / h, the temperature is 50°C, the hydrochloric acid and thiourea are 1.5 mol / L, and it is regenerated with 0.5 mol / L sodium hydroxide. After recycling for 6 times, the adsorption capacity retention rate is greater than 88%, the adsorption capacity retention rate of the leaching resin is ≥88%, and the desorption temperature is ≤60°C to obtain a high-concentration gallium solution.

[0054] Step 5: Mix the high-concentration gallium solution (5000 mg / L) with 25% sodium hydroxide, adjust the pH to 13.5, and electrolyze using stainless steel electrodes with a cathode current density of 90 A / m 2 The electrolysis time is 4.5 hours, the temperature is 50°C, and the metal gallium deposited at the cathode is about 99.6%.

[0055] Step 6: The acid leaching residue is mixed with sodium silicate at a ratio of 1:2.5, calcined at 1250°C for 2.5 hours, and ground to 1-3 μm to obtain silicon micropowder.

[0056] In step 3, sodium hydroxide is added to the effluent of the adsorption column to adjust the pH to 4.5, aluminum hydroxide is precipitated, and the aluminum oxide is obtained by calcining at 850° C. for 3 hours. The purity of the aluminum oxide is 98.5%.

[0057] According to the above technical solution, leaching resin is used for secondary enrichment in step 4. Levextrude resin has a low desorption temperature (50°C), a high adsorption capacity and good regeneration performance, and can effectively recycle resources.

[0058] In step 5, electrolysis was performed using stainless steel electrodes at a current density of 90 A / m 2 The electrolysis temperature is 50°C, and the purity of the metallic gallium precipitated at the cathode is 99.6%. Stainless steel electrodes are suitable for large-scale industrial production due to their low cost.

[0059] Example 2

[0060] Step 1: Grind the fly ash and coal gangue in the coal-based solid waste to a particle size of 0.05 mm, place the crushed coal-based solid waste in a muffle furnace, heat it to 260°C at a heating rate of 8°C / min, and activate it at a constant temperature for 1.8 hours. After activation, the material is cooled to room temperature to obtain an activated coal-based solid waste raw material with a porous structure.

[0061] Step 2: The activated solid waste raw material is mixed with 28% hydrochloric acid solution at a liquid-solid ratio of 3.5:1, heated to 95° C. in a reactor, and stirred for reaction for 4 hours. After the reaction is completed, a gallium-containing acid leaching solution is obtained.

[0062] Step 3: The ion-imprinted modified persimmon peel adsorbent was loaded into the adsorption column, activated with 1 mol / L hydrochloric acid and rinsed to neutrality. The acid extract was passed through the adsorption column at a flow rate of 8 BV / h at a temperature of 50°C, and eluted with 1.5 mol / L hydrochloric acid at a flow rate of 6 BV / h to obtain a gallium-containing desorption solution with a concentration of approximately 1200 mg / L.

[0063] Step 4: The chelating resin is activated with 5% sodium hydroxide and 5% hydrochloric acid in sequence, and rinsed with deionized water until neutral. The gallium-containing desorption liquid is passed through the resin column at a flow velocity of 5 BV / h, the temperature is 65°C, the hydrochloric acid and thiourea are 1.5 mol / L, and it is regenerated with 2 mol / L hydrochloric acid. After circulating 10 times, the adsorption capacity retention rate is greater than 83%, the selectivity coefficient of the chelating resin for gallium is ≥100, the adsorption capacity is ≥200 mg / g, and the iron and aluminum impurity contents in the filtrate after desorption are 3.5 mg / L, thereby obtaining a high-concentration gallium solution.

[0064] Step 5: Mix the high-concentration gallium solution (6000 mg / L) with 22% sodium hydroxide, adjust the pH to 13.8, and electrolyze using titanium plate electrodes with a cathode current density of 70 A / m 2 The electrolysis time is 6 hours, the temperature is 45°C, and the metal gallium deposited at the cathode is about 99.8%.

[0065] Step 6: The acid leaching residue is mixed with sodium silicate at a ratio of 1:3, calcined at 1350°C for 2 hours, and ground to 0.5-2 μm to obtain silicon micropowder;

[0066] In step 3, sodium hydroxide is added to the effluent of the adsorption column to adjust the pH to 4.8, aluminum hydroxide is precipitated, and the aluminum oxide is obtained by calcining at 920° C. for 3 hours. The purity of the aluminum oxide is 98.5%.

[0067] According to the above technical solution, step 4 uses a chelating resin for secondary enrichment. Chelating resins excel at removing impurities, especially iron and aluminum, efficiently removing these impurities and ensuring high gallium purity. Although chelating resins have a relatively high desorption temperature (65°C), their high impurity removal capacity makes up for this, making them suitable for high-end applications.

[0068] In step 5, electrolysis was performed using titanium plate electrodes with a current density of 70 A / m 2 The electrolysis temperature is 45°C, and the purity of the metallic gallium precipitated at the cathode is 99.8%. Titanium plate electrodes have excellent corrosion resistance and stability, making them particularly suitable for the extraction of high-purity gallium. They can also maintain high stability during long-term use.

[0069] Table 1 is a comparison of gallium extraction performance

[0070] parameter Example 1 Example 2 Final gallium concentration (mg / L) 5000 6000 Gallium metal purity (%) 99.6 99.8 Number of cycles (times) 6 10 Adsorption capacity retention rate (%) >88 >83

[0071] According to the results in Table 1, Example 2 has obvious advantages in gallium purity, impurity control, resource utilization, and environmental friendliness. The chelating resin achieves a final gallium concentration of 6000 mg / L, a gallium purity of 99.8%, and an impurity removal rate of over 95%, meeting the needs of high-end applications. In addition, its wastewater treatment cost is low and it is highly environmentally friendly. The purity of silicon micropowder and alumina is as high as 98.5%, and resource utilization is significantly improved.

[0072] In comparison, the leaching resin of Example 1 has greater advantages in terms of energy consumption and operating costs. Its desorption temperature is as low as 50°C, and its adsorption capacity retention rate is higher than 88%. It is suitable for cost-sensitive scenarios, especially in industrial-grade gallium production, and is economical and easy to operate.

[0073] The present invention significantly improves gallium recovery and purity through activation, acid leaching, adsorption, enrichment, and electrolysis, while also achieving waste resource utilization. The chelating resin of Example 2 achieves gallium purity of 99.8% through efficient enrichment and impurity removal, making it suitable for high-end applications. The leaching resin of Example 1, with its low-temperature desorption and high regeneration performance, reduces energy consumption and costs, making it suitable for industrial-grade gallium production.

[0074] Furthermore, in order to verify the economic and environmental advantages of the green resource extraction method for metallic gallium from coal-based solid waste provided by the embodiment of the present invention, the following comparative experiments were carried out. In step S1 of Examples 1 to 2, the coal-based solid waste raw materials were pretreated according to high-temperature activation conditions, and the gallium leaching rates were compared. In step S3, a modified persimmon peel adsorbent was used for selective adsorption of gallium, and the adsorption capacity and gallium recovery rate were measured. In step S4, a leaching resin and a chelating resin were used for secondary enrichment, respectively, and the final gallium concentration and impurity content were compared. In step S5, metallic gallium was refined by a one-step electrolysis method, and the product purity and current efficiency were evaluated. In step S6, the comprehensive utilization value of the acid leaching residue was analyzed, including the purity of silicon micropowder and alumina.

[0075] Table 2 is a comparison table of environmental performance

[0076]

[0077] According to the results in Table 2, Example 2 uses efficient adsorption and selective separation of chelating resin to reduce the iron and aluminum impurity content in the wastewater to less than 5 mg / L, and can be reused without additional treatment, thereby reducing wastewater discharge and treatment costs. At the same time, the acid leaching residue is converted into silicon micropowder and alumina after high-temperature calcination, realizing the resource utilization of solid waste and having better environmental performance.

[0078] In contrast, Example 1 uses leaching resin. Although the wastewater contains high levels of iron and aluminum impurities, requiring neutralization treatment to meet discharge standards, its desorption and electrolysis temperatures are relatively low, effectively reducing energy consumption. Furthermore, the relatively low acid consumption also reduces chemical use and the environmental burden to a certain extent. Overall, Example 2 performs outstandingly in wastewater treatment and resource utilization, while Example 1 has certain advantages in energy conservation and consumption reduction.

[0079] In summary:

[0080] The present invention achieves efficient gallium recovery and resource utilization of waste through processes such as activation, acid leaching, adsorption, enrichment, and electrolysis. The chelating resin process can achieve a gallium concentration of 6000 mg / L and a purity of 99.8%, meeting the needs of high-end fields. At the same time, the iron and aluminum impurity contents in the wastewater are less than 5 mg / L and can be directly reused, reducing wastewater discharge and treatment costs. The leaching resin process has the advantages of low-temperature desorption and low energy consumption. The adsorbent regeneration performance retention rate is as high as over 88%, making it suitable for the economical production of industrial-grade gallium. In addition, the acid leaching residue can be converted into silicon micropowder and alumina after calcination, realizing the resource utilization of solid waste.

[0081] 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 can 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 green resource extraction method for metallic gallium from coal-based solid waste, characterized in that: The following steps are involved: Step 1: Grind fly ash or coal gangue in coal-based solid waste to a particle size of 0.02-0.1 mm, and activate at a high temperature of 200-300°C for 1-2 hours to obtain activated coal-based solid waste raw materials; Step 2: Mix the activated coal-based solid waste with an acid solution at an acid concentration of 10% to 30% and a liquid-to-solid ratio of 3:1-5:1, and react at 80-120° C. for 2-4 hours to obtain a gallium-containing acid leaching solution; Step 3: selectively adsorbing gallium from the gallium-containing acid leaching solution using a persimmon peel adsorbent modified by ion imprinting technology. The adsorption column operates at a flow rate of 5-15 BV / h and an adsorption temperature of 35-55°C. After adsorption saturation, the adsorption column is eluted with a 1 mol / L hydrochloric acid solution to release the adsorbed gallium ions, thereby obtaining a gallium-containing acidic desorption solution. Step 4: The gallium-containing acidic desorption liquid is secondary enriched by a leaching resin or a chelating resin, and desorbed by a hydrochloric acid-thiourea mixed solution to obtain a high-concentration gallium solution; Step 5: adding sodium hydroxide electrolyte to the high-concentration gallium solution, wherein the concentration of the sodium hydroxide electrolyte is 15% to 30%, and performing electrolysis using the metal material as the cathode and anode, wherein metallic gallium is deposited at the cathode; Step 6: washing and drying the acid leaching residue from step 2, mixing it with sodium silicate at a mass ratio of 1:2-1:3, and calcining it at 1200-1400° C. to prepare silicon micropowder; In step 3, sodium hydroxide is added to the effluent of the adsorption column to adjust the pH to 4-5, aluminum hydroxide is precipitated, and aluminum oxide is prepared by calcination.

2. The green resource extraction method for metallic gallium from coal-based solid waste according to claim 1, characterized in that: In step 6, air is introduced into the effluent of the adsorption column in step 3 to adjust the pH to 3-4, and the iron element is precipitated and calcined to prepare iron oxide.

3. The green resource extraction method for metallic gallium from coal-based solid waste according to claim 1, characterized in that: In step 4: the preparation method of the hydrochloric acid-thiourea mixed solution is: After diluting concentrated hydrochloric acid to 1.5 mol / L, add thiourea at a molar ratio of thiourea to hydrochloric acid of 1:50 and stir until completely dissolved; The volume ratio of the hydrochloric acid-thiourea mixed solution to the resin is 3:1-5:1, and the desorption temperature is 40-60°C.

4. The green resource extraction method for metallic gallium from coal-based solid waste according to claim 1, characterized in that: In step 6, the preparation of the silicon micropowder includes: mixing the acid leaching residue and sodium silicate in a mass ratio of 1:2.5, and calcining at 1300° C. for 2 hours to obtain silicon micropowder; The preparation of the aluminum oxide comprises: adding sodium hydroxide to the aluminum-containing filtrate to a pH of 4.5, precipitating aluminum hydroxide, and then calcining at 900° C. for 3 hours to obtain the aluminum oxide.

5. The green resource extraction method for metallic gallium from coal-based solid waste according to claim 1, characterized in that: In step 2, the activated coal-based solid waste raw material is mixed with hydrochloric acid for acid leaching and dissolution, with a hydrochloric acid concentration of 20%, a liquid-solid ratio of 4:1, a reaction temperature of 100° C., and a reaction time of 3 hours.

6. The green resource extraction method of metallic gallium from coal-based solid waste according to claim 1, characterized in that: In step 5, an alkaline electrolyte is added to the high-concentration gallium solution, wherein the concentration of sodium hydroxide in the alkaline electrolyte is 20%.

7. The green resource extraction method for metallic gallium from coal-based solid waste according to claim 1, characterized in that: In step 5, during the electrolysis process, the electrolysis current density is 50-100 A / m 2 , the electrolysis time is 4-6h.

8. The green resource extraction method for metallic gallium from coal-based solid waste according to claim 1, characterized in that: In step 6, during the preparation of the silicon micropowder, the mass ratio of the acid leaching residue to the sodium silicate is 1:2.5, and the silicon micropowder is calcined at 1200-1400° C. for 3 hours, and the particle size of the silicon micropowder is 0.5-3 μm.

9. The green resource extraction method for metallic gallium from coal-based solid waste according to claim 1, characterized in that: In the hydrochloric acid-thiourea mixed solution, the added amount of thiourea is 0.5% to 2% of the molar amount of hydrochloric acid.

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