Method for extracting scattered metal by comprehensively utilizing bauxite waste residues

Abstract

The invention relates to the technical field of recycling of waste resources, in particular to a method for extracting scattered metal through comprehensive utilization of bauxite waste residues. The method is characterized in that silicon dioxide, copper, iron and aluminum impurities in the bauxite waste residues are removed by adopting a method of first acid leaching and then alkaline leaching, basic conditions are provided for extracting scattered metal gallium, meanwhile, valuable metal is recycled, and comprehensive utilization of the bauxite waste residues is achieved; octadecyl catechol is selected as an extracting agent, so that the method is suitable for extraction under an alkaline condition, the synthesis is relatively simple, and the cost is relatively low.

Description

Technical Field

[0001] The invention relates to the technical field of recycling waste resources, and in particular to a method for extracting rare metals by comprehensive utilization of bauxite waste residue. Background Art

[0002] In the electrolytic refining of aluminum, in addition to the production of metallic aluminum, gallium-containing anode alloys, electrolytic cell coal foam, and soot are also obtained. The above waste residues contain gallium, silicon dioxide, copper, iron, and aluminum. The composition of the anode alloy in the waste residue is analyzed as follows: Ga 0.1-0.4%; Al 40-60%; Zn 0.1-1.3%; Cu 25-35%; Fe 4-19%; SiO 21~12%; Mn0.1~1.5%. The recovery of scattered metal gallium, copper and aluminum in waste slag has important economic benefits, especially the extraction of scattered metal gallium is an important source of gallium. The Chinese invention patent (patent number CN202410569871.9, patent name Gallium Extractant and its preparation and application in Gallium Extraction) discloses a gallium extractant and its preparation and application in gallium extraction, characterized in that: in view of the technical defects of low recycling application of existing hydroxamic acid extractants when extracting gallium, the first purpose of the present invention is to provide a gallium extractant with a new synergistic structure, aiming to improve the extraction efficiency and cyclic extraction stability of gallium. The second purpose of the present invention is to provide a preparation method of the gallium extractant. The third purpose of the present invention is to provide a combined extractant for gallium extraction comprising the gallium extractant. The fourth purpose of the present invention is to provide a method for gallium extraction using the gallium extractant. In the initial application stage, the existing gallium extractant can adapt well to the physicochemical characteristics of gallium and can show acceptable effects. However, as the number of cyclic applications increases, the physicochemical structure of the extractant is prone to change, making it difficult to continue to adapt to the physicochemical characteristics of gallium, unable to continue to show acceptable extraction performance, and the cyclic extraction stability is not ideal. In response to this problem, the present invention has conducted in-depth research and provided the following scheme: a gallium extractant is a compound having a structure of formula 1. The R1 is an alkyl or olefin group of C10 to C22; the R2 is H or an alkyl group of C1 to C4. The present invention provides a new compound of formula 1 structure, and it is found that the combination of NC-CO-NH-OH in the compound structure can achieve synergy, which has an excellent gallium adaptation effect and can show excellent gallium extraction activity. In addition, it can also avoid the problem of physical and chemical property degradation during the cyclic extraction process and can show excellent cyclic extraction stability. In the present invention, the R1 is a straight or branched alkyl group of C11 to C19, and further a straight alkyl group of C12 to C18; preferably, the R2 is an alkyl group of C1 to C3. The present invention has shown that under this preferred result, the melting point of the compound can be further reduced, making it more suitable for the application requirements of gallium extraction. The present invention also provides a method for preparing the gallium extractant, wherein the raw material of formula 2 is subjected to an esterification reaction with an alcohol to obtain an esterification product, which is then subjected to an oximation reaction with hydroxylamine, and then subjected to an acidification treatment to obtain the product. The selection range of R1 and R2 in the formula 2 is the same as that of formula 1. The present invention successfully prepares the gallium extractant by conducting an esterification reaction between formula 2 and an alcohol, followed by oximation and acidification.The Chinese invention patent (patent number CN202410527342.2, patent name is a method for enriching gallium ions) discloses a method for enriching gallium ions, characterized in that it includes the following steps: 1) converting gallium-containing iron raw materials into precipitates containing gallium hydroxide and iron hydroxide; 2) mixing the precipitate, hydrochloric acid aqueous solution, chlorinated waste salt and reducing agent to obtain an acid leaching solution; 3) using polyurethane to adsorb and desorb gallium ions from the acid leaching solution. The present invention enriches gallium from gallium-containing iron raw materials, chemically adsorbs and desorbs the acid leaching solution through a polyurethane adsorbent, and achieves efficient separation of gallium. The acid leaching solution is prepared by the synergistic action of hydrochloric acid and chlorinated waste iron, and then adsorbed and desorbed by a polyurethane adsorbent, thereby achieving the purpose of enriching gallium.

[0003] Prior art 1 Gallium extractant selects the NC-CO-NH-OH compound structure, which has many extracting functional groups, such as the oxygen of oxime acid CO-NH-OH and isomer oxime group C=N-OH can provide lone pairs of electrons to chelate with gallium cations, such as keto CO-N and isomer nitrogen enol HOC=N in nitrogen, oxygen can provide lone pairs of electrons to chelate with gallium cations, the extractant molecule and gallium cation form a double five-membered ring ligand structure, because the extractant molecule has C 10 ~C 22 The alkane or olefin chain is dissolved in an organic solvent, and the gallium cation is extracted from the aqueous phase to the organic phase. The NC-CO-NH-OH compound structure in the gallium extractant of prior art 1 is easily hydrolyzed under alkaline conditions, such as the oxime acid group in its compound structure, so it is not suitable as an extractant under alkaline conditions. In addition, the extractant has a strong ability to chelate with metal cations and form a relatively stable chelate ring, so the back extraction becomes more difficult. Prior art 1 does not disclose the technical details of how to back extract. In addition, the extractant is relatively complex to synthesize and has a high cost. Prior art 2 selects polyurethane as an extractant, and its extraction functional group is mainly oxygen in the enone type -CO-. This compound structure is easily hydrolyzed under alkaline conditions, so it is not suitable as an extractant under alkaline conditions. Therefore, the process flow of acid leaching after removing impurities by alkali leaching is adopted. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention aims to provide a method for extracting rare metals from bauxite waste residues by comprehensive utilization, which is characterized by: step 1, crushing the bauxite waste residues into particles with a particle size of 8 to 10 mm, sending them into an oxidation roasting furnace, roasting them at a temperature of 500 to 700°C for 5 to 6 hours to remove the F element that is more harmful to the equipment, and then crushing them into a reactor and reacting them with 20% hydrochloric acid at 110°C for 1 hour, and sending the resulting clarified liquid to a clarification tank, and SiO in the waste residue is removed. 2The components are removed, and the clarified liquid is stirred and then left to cool at room temperature, and precipitation and crystallization are precipitated to obtain aluminum chloride crystals, thereby completing the purpose of removing aluminum from the waste slag clarified liquid. The reaction formula is: Al 2 O 3 +6HCl+3H 2 O→2AlCl 3 •6H 2 O, aluminum chloride can be oxidized and roasted to obtain alumina powder, realizing the recycling of metallic aluminum.

[0005] Step 2: The hydrochloric acid leaching solution from which aluminum and silicon dioxide have been removed is neutralized by adding NaOH, and the pH value is slowly adjusted to 4.2-5.0. The solution is allowed to stand at room temperature for 2 hours to precipitate Fe(OH) 3 Separate the precipitate and continue to slowly adjust the pH value of the clarified liquid to 7.5-8.0. Let it stand at room temperature for 1 hour to precipitate Cu(OH) 2 and Zn(OH) 2 Separate the precipitate and adjust the pH value of the clear solution to 10.4. Let it stand at room temperature for 0.5 hours to precipitate Mn(OH) 2 Precipitation: During the alkaline leaching process, 95% to 97% of the gallium enters the alkaline leaching solution.

[0006] Step 3: Select octadecylcatechol as the extractant. Its extracting functional groups are two adjacent hydroxyl groups on the benzene ring. The ß position of the benzene ring links the octadecane chain to make it soluble in organic solvents. In the presence of alkali, the catechol group is in a resonance-stabilized enol-ß-diketone state. The unpaired electrons of the adjacent hydroxyl oxygen anions form a hyperconjugated electron cloud with the benzene ring in a fluffy state. Its electron-donating ability is stronger than that of OH. - Negative ions, thus reacting with OH - Negative ions rob gallium metal cations, realize the chelation of catechol groups with gallium metal cations, generate a double five-membered chelate ring ligand structure, and lose the -OH hydrophilic group, so that it is difficult to dissolve in water phase but easy to dissolve in organic phase. The reaction mechanism is as follows: The organic phase is selected to be kerosene containing 20% ​​of octadecyl catechol, the gallium metal ion content in the original aqueous phase feed liquid is 0.16-0.2 g / L, the pH value is 10.0-10.4, the flow ratio of the organic phase to the aqueous phase is controlled to be 1:2, the extracted gallium-containing organic phase is then stripped of gallium using a 1.6-1.8 mol / L hydrochloric acid solution, the flow ratio of the organic phase to the aqueous phase is controlled to be 1:1, the extraction and stripping equipment both use a stirred sieve plate extraction tower, the obtained extract phase enters an evaporator for distillation, the solvent HCl is recovered, and a gallium-enriched aqueous solution is obtained, and finally oxidative roasting is performed to obtain finished gallium oxide particles. The stirring sieve plate extraction tower comprises a light phase outlet, a light phase collecting kettle, an aqueous phase inlet, a stirring assembly, an organic phase inlet, a heavy phase collecting kettle, an aqueous phase outlet, a reduction motor, a stirring connecting rod, a paddle, a vortex blade, and a sieve plate. During extraction, the organic phase flows upstream from the organic phase inlet and contacts with the original aqueous phase liquid input from the aqueous phase inlet. Each tower stage is designed with a sieve plate. The paddles are designed to be arranged below the sieve plate in parallel with the paddles, and the spacing between the paddles is 1.0 to 1.5 cm. The sieve plate is a stationary device. The reduction motor drives the paddles to rotate via the stirring connecting rod. The paddles are composed of 16 to 32 vortex blades. When the solution passes through the pores of the sieve plate, a fine liquid flow is formed. The vortex blades shear and collide with the fine liquid flow to destroy its surface tension and turn it into fine droplets. When the reduction motor rotates forward, the fluid flows from the center to the circumference under the guidance of the vortex blades. When the reduction motor rotates reversely, the fluid flows from the circumference to the center under the guidance of the vortex blades. Regardless of whether the reduction motor rotates forward or reversely, the pressure direction, velocity direction, and movement direction of the fluid in the flow channels of the sieve plate and the blades are very different and continuously change. Then the two-phase liquid is easy to form turbulence, thereby obtaining better mixing, increasing the interphase contact area of ​​the two phases, and improving the interphase contact mass transfer efficiency of the two phases. After mass transfer between the organic phase and the original aqueous phase feed liquid, the organic phase for extracting gallium is gradually enriched in the light phase collecting kettle and output from the light phase outlet, and the aqueous phase is gradually enriched in the heavy phase collecting kettle and output from the aqueous phase outlet. During stripping, the process flow is the same as the above process.

[0007] Compared with the prior art, the present invention has at least the following advantages: 1. The method of acid leaching followed by alkaline leaching is adopted to remove silicon dioxide, copper, iron and aluminum impurities in the bauxite waste residue, thereby providing basic conditions for extracting scattered metal gallium, while recovering valuable precious metals and realizing the comprehensive utilization of bauxite waste residue; 2. Octadecyl catechol is selected as the extractant, which is suitable for extraction under alkaline conditions, has a relatively simple synthesis and is relatively low in cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 This is a schematic diagram of the main structure of a method for extracting rare metals by comprehensive utilization of bauxite waste slag according to the present invention.

[0009] Figure 2This is a schematic diagram of the structure of sample A of a method for extracting rare metals by comprehensive utilization of bauxite waste slag in the present invention.

[0010] Figure 3 It is a schematic diagram of the BB cross-sectional structure of a method for extracting rare metals by comprehensive utilization of bauxite waste slag according to the present invention.

[0011] Figure 4 It is a CC cross-sectional structural schematic diagram of a method for extracting rare metals by comprehensive utilization of bauxite waste slag according to the present invention.

[0012] 1-light phase outlet 2-light phase collection kettle 3-water phase inlet 4-stirring component 5-Organic phase inlet 6-Heavy phase collection kettle 7-Water phase outlet 8-Reduction motor 9 - stirring connecting rod 10 - paddle blade 11 - vortex blade 12 - sieve plate. DETAILED DESCRIPTION

[0013] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0014] like Figure 1 , Figure 2 , Figure 3 , Figure 4 As shown, a method for extracting rare metals by comprehensive utilization of bauxite waste residue is characterized by: step 1, crushing the bauxite waste residue into particles with a particle size of 8 to 10 mm, sending it into an oxidation roasting furnace, roasting it at a temperature of 500 to 700°C for 5 to 6 hours to remove the F element that is more harmful to the equipment, and then crushing it and adding it to a reactor to react with 20% hydrochloric acid at 110°C for 1 hour, and the resulting clarified liquid is sent to a clarification tank, and SiO in the waste residue is removed. 2 The components are removed, and the clarified liquid is stirred and then left to cool at room temperature, and precipitation and crystallization are precipitated to obtain aluminum chloride crystals, thereby completing the purpose of removing aluminum from the waste slag clarified liquid. The reaction formula is: Al 2 O 3 +6HCl+3H 2 O→2AlCl 3 •6H 2 O, aluminum chloride can be oxidized and roasted to obtain alumina powder, realizing the recycling of metallic aluminum.

[0015] Step 2: The hydrochloric acid leaching solution from which aluminum and silicon dioxide have been removed is neutralized by adding NaOH, and the pH value is slowly adjusted to 4.2-5.0. The solution is allowed to stand at room temperature for 2 hours to precipitate Fe(OH) 3 Separate the precipitate and continue to slowly adjust the pH value of the clarified liquid to 7.5-8.0. Let it stand at room temperature for 1 hour to precipitate Cu(OH) 2 and Zn(OH) 2Separate the precipitate and adjust the pH value of the clear solution to 10.4. Let it stand at room temperature for 0.5 hours to precipitate Mn(OH) 2 Precipitation: During the alkaline leaching process, 95% to 97% of the gallium enters the alkaline leaching solution.

[0016] Step 3: Select octadecylcatechol as the extractant. Its extracting functional groups are two adjacent hydroxyl groups on the benzene ring. The ß position of the benzene ring links the octadecane chain to make it soluble in organic solvents. In the presence of alkali, the catechol group is in a resonance-stabilized enol-ß-diketone state. The unpaired electrons of the adjacent hydroxyl oxygen anions form a hyperconjugated electron cloud with the benzene ring in a fluffy state. Its electron-donating ability is stronger than that of OH. - Negative ions, thus reacting with OH - Negative ions rob gallium metal cations, realize the chelation of catechol groups with gallium metal cations, generate a double five-membered chelate ring ligand structure, and lose the -OH hydrophilic group, so that it is difficult to dissolve in water phase but easy to dissolve in organic phase. The reaction mechanism is as follows: The organic phase is selected to be kerosene containing 20% ​​of octadecyl catechol, the gallium metal ion content in the original aqueous phase feed liquid is 0.16-0.2 g / L, the pH value is 10.0-10.4, the flow ratio of the organic phase to the aqueous phase is controlled to be 1:2, the extracted gallium-containing organic phase is then stripped of gallium using a 1.6-1.8 mol / L hydrochloric acid solution, the flow ratio of the organic phase to the aqueous phase is controlled to be 1:1, the extraction and stripping equipment both use a stirred sieve plate extraction tower, the obtained extract phase enters an evaporator for distillation, the solvent HCl is recovered, and a gallium-enriched aqueous solution is obtained, and finally oxidative roasting is performed to obtain finished gallium oxide particles. The stirring sieve plate extraction tower comprises a light phase outlet 1, a light phase collecting kettle 2, an aqueous phase inlet 3, a stirring assembly 4, an organic phase inlet 5, a heavy phase collecting kettle 6, an aqueous phase outlet 7, a reduction motor 8, a stirring connecting rod 9, a paddle 10, a vortex blade 11, and a sieve plate 12. During extraction, the organic phase flows upstream from the organic phase inlet 5 and contacts with the original aqueous phase liquid input from the aqueous phase inlet 3. Each tower stage is designed with a sieve plate 12. The paddle blades 10 are designed to be arranged below the sieve plate 12 and are paired in parallel with each other. The spacing between the paddle blades 10 and the sieve plate 12 is 1.0-1.5 cm. The sieve plate 12 is a stationary device. The reduction motor 8 drives the paddle blades 10 to rotate via the stirring connecting rod 9. The paddle blades 10 are composed of 16-32 vortex blades 11. When the solution passes through the pores of the sieve plate 12, a fine liquid flow is formed. The vortex blades 11 shear and collide with the fine liquid flow to destroy its surface. Tension turns into fine droplets. At the same time, when the reduction motor 8 rotates forward, the fluid flows from the central direction to the circumferential direction under the guidance of the vortex blades 11. When the reduction motor 8 is reversed, the fluid flows from the circumferential direction to the central direction under the guidance of the vortex blades 11. Regardless of whether the reduction motor 8 is rotating forward or reverse, the pressure direction, speed direction, and movement direction of the fluid in the flow channels of the sieve plate 12 and the blades 10 are very different and continuously change. Then the two-phase liquid is easy to form turbulence, thereby obtaining better mixing, increasing the interphase contact area of ​​the two phases, and improving the interphase contact mass transfer efficiency of the two phases. After mass transfer between the organic phase and the original aqueous phase feed liquid, the organic phase for extracting gallium is gradually enriched in the light phase collecting kettle 2 and output from the light phase outlet 1, and the aqueous phase is gradually enriched in the heavy phase collecting kettle 6 and output from the aqueous phase outlet 7. During stripping, its process flow is the same as the above process.

Claims

1. A method for extracting rare metals by comprehensive utilization of bauxite waste residue, characterized in that: Step 1: crush the bauxite waste slag into particles with a size of 8 to 10 mm, send it into an oxidation roasting furnace, roast it at a temperature of 500 to 700°C for 5 to 6 hours to remove the F element that is more harmful to the equipment, and then add it to a reactor after crushing and react with 20% hydrochloric acid at 110°C for 1 hour. The resulting clarified liquid is sent to a clarification tank, and the SiO2 component in the waste slag is removed. The clarified liquid is stirred and allowed to stand and cool at room temperature, and precipitation and crystallization are precipitated to obtain aluminum chloride crystals, thereby completing the purpose of removing aluminum from the waste slag clarified liquid. The reaction formula is: Al2O3+6HCl+3H2O→2AlCl3•6H2O. Aluminum chloride can be oxidized and roasted to obtain alumina powder, thereby realizing the recycling of metallic aluminum; Step 2: remove aluminum and silicon dioxide hydrochloric acid leaching solution, add NaOH to neutralize it, and slowly adjust the pH value to 4.2 to 5.0, stand it at room temperature for 2 hours, and precipitate Fe(OH)3. The pH value of the clarified liquid of the separated precipitate is further slowly adjusted to 7.5-8.0, and it is allowed to stand at room temperature for 1 hour to precipitate Cu(OH)2 and Zn(OH)2. The pH value of the clarified liquid of the separated precipitate is further adjusted to 10.4, and it is allowed to stand at room temperature for 0.5 hour to precipitate Mn(OH)2. During the alkaline leaching process, 95%-97% of the gallium enters the alkaline leaching solution; Step three, the organic phase is selected to be kerosene containing 20% ​​octadecyl catechol, and the extraction and back-extraction equipment both use a stirred sieve plate extraction tower. The obtained extract phase enters the evaporator for distillation, and the solvent HCl is recovered to obtain a gallium-enriched aqueous solution, and finally oxidative roasting is performed to obtain finished gallium oxide particles. The stirring sieve plate extraction tower comprises a light phase outlet, a light phase collecting kettle, a water phase inlet, a stirring assembly, an organic phase inlet, a heavy phase collecting kettle, a water phase outlet, a reduction motor, a stirring connecting rod, a paddle, a vortex blade, and a sieve plate. During extraction, the organic phase flows upstream from the organic phase inlet and contacts with the original water phase liquid input from the water phase inlet. After mass transfer between the organic phase and the original water phase liquid, the organic phase for extracting gallium gradually enriches in the light phase collecting kettle and is output from the light phase outlet, and the water phase gradually enriches in the heavy phase collecting kettle and is output from the water phase outlet. During stripping, the process flow is the same as the above process.

2. The method for extracting rare metals by comprehensive utilization of bauxite waste according to claim 1, characterized in that: The bauxite waste slag is crushed into particles with a size of 8 to 10 mm, sent to an oxidation roasting furnace, and roasted at a temperature of 500 to 700°C for 5 to 6 hours to remove the F element that is more harmful to the equipment.

3. The method for extracting rare metals by comprehensive utilization of bauxite waste according to claim 1 is characterized by: Octadecylcatechol was selected as the extractant, and its extraction functional groups were two adjacent hydroxyl groups on the benzene ring. The ß position of the benzene ring was linked to the octadecane chain, making it soluble in organic solvents.

4. The method for extracting rare metals by comprehensive utilization of bauxite waste residue according to claim 1 is characterized by: In the presence of base, the catechol group is in a resonance-stabilized enol-β-diketone state, and the unpaired electrons of the adjacent hydroxyl oxygen anion form a hyperconjugated electron cloud with the benzene ring in a fluffy state, and its electron-donating ability is stronger than that of OH - Negative ions, thus reacting with OH - Negative ions rob gallium metal cations, realize the chelation of catechol groups with gallium metal cations, generate a double five-membered chelate ring ligand structure, and lose the -OH hydrophilic group, so that it is difficult to dissolve in water phase but easy to dissolve in organic phase. The reaction mechanism is as follows: 。 5. The method for extracting rare metals by comprehensive utilization of bauxite waste residue according to claim 1 is characterized by: The gallium metal ion content in the original aqueous phase liquid is 0.16-0.2 g / L, the pH value is 10.0-10.4, the flow ratio of the organic phase to the aqueous phase is controlled to be 1:2, and the extracted gallium-containing organic phase is then stripped of gallium using a 1.6-1.8 mol / L hydrochloric acid solution, and the flow ratio of the organic phase to the aqueous phase is controlled to be 1:

1.

6. The method for extracting rare metals by comprehensive utilization of bauxite waste residue according to claim 1 is characterized by: Each tower level is designed with a sieve plate, and the paddles are designed to be paired parallel to the sieve plates below, with a spacing of 1.0 to 1.5 cm between them. The sieve plates are stationary devices, and the reduction motor drives the paddles to rotate through the stirring connecting rod. The paddles are composed of 16 to 32 vortex blades.

7. The method for extracting rare metals by comprehensive utilization of bauxite waste residue according to claim 1 is characterized by: When the solution passes through the pores of the sieve plate, a small liquid flow is formed. The vortex blades shear and collide with the small liquid flow, destroying its surface tension and turning it into small droplets.

8. The method for extracting rare metals by comprehensive utilization of bauxite waste residue according to claim 1 is characterized by: When the reduction motor rotates forward, the fluid flows from the central direction to the circumferential direction under the guidance of the vortex blades. When the reduction motor rotates reversely, the fluid flows from the circumferential direction to the central direction under the guidance of the vortex blades.

9. The method for extracting rare metals by comprehensive utilization of bauxite waste residue according to claim 1 is characterized by: Regardless of whether the reduction motor is rotating forward or reverse, the pressure direction, velocity direction, and movement direction of the fluid in the flow channels of the sieve plate and the paddle are very different and continuously changing. Then the two-phase liquid is likely to form turbulence, thereby achieving better mixing, increasing the interphase contact area of ​​the two phases, and improving the interphase contact mass transfer efficiency of the two phases.

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