Method for recycling magnesium salt in nickel-cobalt industry

Abstract

The invention discloses a method for recycling magnesium salt in the nickel-cobalt industry, and relates to the field of metal ion-containing wastewater treatment.The method comprises the steps that magnesium sulfate wastewater generated after multiple extraction reacts with medium alkali and strong alkali, a trace amount of surface treating agent is added, and a mixed precipitate of magnesium hydroxide and sulfate is generated; a part of water phase is filtered out through a filter press and returned to raw material slurrying, the remaining mixed slurry is pumped into a high-pressure reaction kettle, carbon dioxide is introduced into the kettle, a certain pressure is kept, meanwhile, a composite nano-catalyst La doped Fe3O4atSiO2 is introduced, and mixed slurry of soluble magnesium bicarbonate and insoluble sulfate is prepared; after rapid filtration, the synthesized and prepared magnesium bicarbonate filtrate is used for replacing liquid caustic soda to be saponified with a blank organic phase, carbon dioxide generated in the saponification reaction process is recycled, and soaped organic matter enters different extraction production lines to be subjected to purification and separation of multi-metal mixed feed liquid, so that virtuous cycle of a production system is achieved.

Description

Technical Field

[0001] The present invention relates to the field of wastewater treatment containing metal ions, and is a method for recycling magnesium salts and carbon dioxide. Specifically, it relates to a method for comprehensively recovering and recycling magnesium sulfate waste liquid. Background Art

[0002] The manufacturing of nickel / cobalt metals and related products belongs to the field of hydrometallurgy industry and is an important strategic material resource essential for the country's development. The initial processing of nickel / cobalt products mainly uses nickel / cobalt-containing minerals such as crude nickel cobalt hydroxide, nickel cobalt carbonate, nickel cobalt sulfide flotation materials, high / low nickel matte copper cobalt materials, etc. In addition to nickel and cobalt, the main components of ore materials rich in nickel / cobalt elements also contain certain amounts of base metal elements such as calcium / magnesium / iron, which are regarded as "impurities" in the production process and seriously interfere with and affect the process flow, product yield, product quality, cost control, environmental protection treatment, etc.

[0003] Since the manufacturing of nickel cobalt and derivative high-end products is a product based on wet production, a large amount of water is required as a reaction medium during the process. After the reaction ends, a large amount of saline wastewater needs to be treated, which will cause waste of water resources and increase the investment in environmental protection treatment.

[0004] In addition, waste (tail) gas will inevitably be brought during the wet production process. Carbon dioxide is one of them. The full recovery and recycling of industrial waste gas is also a topic of concern in this innovation project.

[0005] In short, the wastewater, waste residue, waste gas, etc. generated during industrial production always affect the natural environment on which people depend for survival. We will spare no effort to promote technological progress and use the power of science and technology to utilize and overcome it. Summary of the Invention

[0006] The present invention proposes a new method for recycling magnesium salts. Using the magnesium sulfate waste liquid generated by the extraction system as a raw material, the magnesium bicarbonate generated through chemical combination and pressurized reaction is used as a saponification reagent. After saponification, the organic phase is extracted and back-extracted to regenerate magnesium sulfate waste liquid and blank organic to be saponified, which are respectively returned to the precipitation process and the extraction saponification link for a new round of circulation, realizing the comprehensive recycling of various resources.

[0007] To solve the above technical problems, the present invention provides the following technical solution: A method for recycling magnesium salts and carbon dioxide, the method comprising the following steps:

[0008] (1) taking 1000 mL of magnesium sulfate waste liquid remaining after extraction, adding a strong alkaline aqueous solution thereto so that the molar ratio of magnesium sulfate to the strong base is 1:1-1.05, then adding 3-4 ml of a 10% sodium dodecylbenzene sulfonate solution and 3 g of nano-activated carbon particles, reacting at room temperature for 2 h, and the reaction temperature is 40-60° C.;

[0009] (2) After the reaction is completed, a portion of the slurry is filtered with the aid of a vacuum filter, and the filtered water phase is returned to the raw material slurry pretreatment section or step (1) for preparation of a strong alkaline aqueous solution; the filter residue and the remaining unfiltered mixed slurry are placed in a high-pressure reactor, and a composite nano-catalyst of 0.1-0.5% of the total mass of the reaction system is added, and then CO2 gas is introduced into the reactor under stirring at a gas flow rate of 1 L / min, and the pressure in the reactor is maintained at 0.5-0.6 MPa. The reaction is carried out for 1.5-3.5 hours at a temperature of 5-35°C. After the reaction is completed, solid-liquid separation is performed, and the solid is an insoluble sulfate, and the liquid aqueous phase is a magnesium bicarbonate solution.

[0010] 2. A method for recycling magnesium salt and carbon dioxide according to claim 1, characterized in that the source of the magnesium sulfate waste liquid in the extraction section in step (1) is: the mixed liquid to be extracted is brought by itself and magnesium bicarbonate solution is used as a saponification reagent, and a saponification reaction occurs with the blank organic phase. During saponification, the volume ratio of the organic phase to the aqueous phase is 1:1.5-2, the concentration of the blank organic phase is 20-25%, the saponification temperature is 20-40°C, the saponification time is 6min, the saponification rate is 50-60%, and the carbon dioxide generated during the saponification process is recovered and re-pressurized for utilization, and the organic phase after soap and the multi-metal mixed solution enter the extraction; the temperature is set to 30-45°C, the extraction stage is 10, and the volume ratio of the organic phase to the liquid is 1:0.3-3; the raffinate wastewater magnesium sulfate reacts with a strong base as a raw material for combining magnesium bicarbonate, and the blank organic phase after stripping returns to the extraction section to participate in saponification again.

[0011] Furthermore, the blank organic compound is P204 or P507 or Cyanex272.

[0012] Furthermore, the metal components in the metal solution include one or more of Cu, Mn, Zn, Co, Ni, Ca, and Mg.

[0013] Furthermore, the source of the strong alkali in step (1) is: solid barium salt is washed twice with deionized water, dried at 105°C for 2h, and then calcined to prepare barium oxide. Microwave assistance is added during the calcination process. The microwave power is 500-1000W, the calcination temperature is 700-750°C, and the time is 20-40min. After the calcination, it is mixed with deionized water for reaction. The solid-liquid mass ratio is 1:3-5. The reaction time is 2h. After chemical reaction with water, a strong alkali aqueous solution is formed, which is put into the production link for recycling.

[0014] Further, the content of magnesium element in the magnesium sulfate waste liquid described in step (1) is 10 - 21 g / L.

[0015] Further, the strong base described in step (1) can be barium hydroxide or calcium hydroxide.

[0016] Further, the composite nano - catalyst in step (2) is La - doped Fe3O4@SiO2, and the preparation method is as follows: Disperse 0.08 - 0.15 parts of carboxylated porous Fe3O4 nanoparticles in 3 parts of deionized water, ultrasonicate for 3 min, the ultrasonic power is 40 kHz, then add La(NO3)3·6H2O to configure a concentration of 0.1 - 0.5 mol / L to obtain a mixed solution; then mix 50 parts of ethanol, 1 part of deionized water, 2 parts of 25% ammonium hydroxide and 0.24 - 0.9 μL of tetraethyl orthosilicate, react in a water bath at 40°C for 10 - 20 min, add the mixed solution, stir at 120 rpm, react at 40°C for 8 h, wash alternately 4 times with deionized water and absolute ethanol, rotary evaporate to remove the solvent, then dry at 60°C for 12 h, place the dried particles in a muffle furnace, calcine at 500 - 600°C for 2 - 4 h to form the La - doped Fe3O4@SiO2 composite nano - catalyst.

[0017] Further, the particle size of the porous Fe3O4 nanoparticles is 100 - 500 nm.

[0018] Further, the reaction rotation speed in the high - pressure reactor described in step (2) is 200 - 350 rpm.

[0019] Further, the content of magnesium element in the magnesium bicarbonate filtrate produced after the pressurized reaction in step (2) is 10 - 22 g / L.

[0020] Compared with the existing traditional technologies, the benefits that the present invention can produce are:

[0021] (1) The magnesium sulfate wastewater produced after multiple extractions is recycled and then undergoes a double - decomposition reaction with the recycled strong base. When reacting, a trace amount of surface treatment agent is optimally added. Due to the shielding effect of the ion pair of the surface treatment agent on the hydroxyl groups of the layered crystal, the produced magnesium hydroxide and sulfate mixed precipitate is dispersed and not easily polymerized, increasing the reaction contact area in the subsequent treatment, thereby improving the overall recycling efficiency. Adding activated carbon particles can adsorb impurities in the double - decomposition reaction and also provide crystal sites for the mixed precipitate, reducing the precipitation and scaling of supersaturated precipitate on the reaction vessel wall;

[0022] (2) After the double decomposition reaction is completed, filtration is assisted by a vacuum filter. The filtered aqueous phase is returned to the raw material pulping in step (1) or used for the preparation of strong alkali solution. The filter residue and the remaining slurry containing the mixed precipitate of magnesium hydroxide and sulfate are pumped into a high-pressure reactor. Recovered CO2 is introduced into the reactor and maintained at a certain pressure to synthesize a mixed slurry of soluble magnesium bicarbonate and insoluble sulfate. After filtration, a magnesium bicarbonate filtrate is obtained. In the high-pressure reactor, the reaction efficiency of magnesium hydroxide and CO2 to form magnesium bicarbonate is limited by the reaction kinetics. By optimizing the amount of CO2 introduced and the synthesis temperature, the conversion efficiency of magnesium hydroxide to magnesium bicarbonate is ensured. At the same time, a composite nano-catalyst La-doped Fe3O4@SiO2 is introduced. The active sites on the catalyst surface promote the adsorption and activation of CO2, reduce the reaction activation energy, significantly reduce the reaction time and improve the conversion rate. The prepared magnesium bicarbonate filtrate is returned to step (1) as a saponifying agent to complete the cycle. At the same time, the rapid stirring in the high-pressure reactor makes the mixed slurry have a certain flow rate, reducing the crystallization of the product on the reactor wall and generating a scale layer;

[0023] (3) The insoluble solid barium salt is calcined to prepare barium oxide. The microwave-assisted calcination technology is introduced. Through the penetrability and selective heating characteristics of microwaves, the calcination temperature is significantly reduced, the calcination time is shortened, and at the same time, the yield and purity of barium oxide are improved. It is put into the production process for recycling, further reducing the waste gas treatment cost and realizing the green and efficient regeneration of strong alkali. Specific embodiments

[0024] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work belong to the scope of protection of the present invention.

[0025] The reaction equations are as follows:

[0026] 1. Magnesium sulfate solution reacts with calcium / barium hydroxide to synthesize magnesium hydroxide

[0027] MgSO4+R x (OH)2 == Mg(OH)2↓+R x SO4↓ (Rx represents the calcium / barium symbol)

[0028] 2. The generated magnesium hydroxide and others react with carbon dioxide gas under pressure to synthesize magnesium bicarbonate

[0029] Mg(OH)2 + 2CO2 == Mg(HCO3)2

[0030] 3. The generated magnesium bicarbonate reacts with an organic extractant to carry out a saponification reaction

[0031] 2RP-OH + Mg(HCO3)2 == Mg(RP-O)2 + 2H2O + 2CO2↑

[0032] 4. After saponification, the organic phase generates magnesium sulfate after extracting copper / manganese / zinc / cobalt.

[0033] Mg(RP-O)2 + X n SO4 == X n (RP-O)2 + MgSO4

[0034] Note: In the above reaction formula (1), if calcium hydroxide is used, by-product calcium sulfate whiskers are generated; if barium hydroxide is used, by-product barium sulfate is generated; however, barium sulfate and barium hydroxide can also be converted through reactions for infinite cycling.

[0035] 5. The reaction for preparing barium hydroxide using barium sulfate as the main raw material is as follows

[0036] 2BaSO4 (calcined at high temperature) == 2BaO + 2SO2↑ + O2↑

[0037] BaO + H2O == Ba(OH)2

[0038] (Note: Adding an appropriate amount of carbon to the ingredients before calcination enables the reaction according to the following equation)

[0039] BaSO4 + 4C == BaS + 4CO↑

[0040] 2BaS + 2H2O == Ba(HS)2 + Ba(OH)2

[0041] Example 1; (1) Using magnesium bicarbonate solution as the saponification reagent, reacting with P204 blank organic for saponification. During saponification, the volume ratio of the organic phase to the aqueous phase is 1:2, the concentration of P204 is 20%, the saponification temperature is 30°C, the saponification time is 6 min, and the saponification rate is 60%. The CO2 generated during saponification is treated by a gas recovery device and then transported to the high-pressure reaction section of step (3); the organic phase after saponification reacts with the multi-metal mixed solution. In the multi-metal mixed solution: zinc is 2.22 g / L, copper is 1.75 g / L, manganese is 11.08 g / L, and magnesium is 1.5 g / L; the extraction temperature is 35°C, the number of extraction stages is 10, the volume ratio of the organic phase to the feed liquid is 1:1. The raffinate wastewater magnesium sulfate solution is recovered and reacted with barium hydroxide, and the blank organic phase after back-extraction returns to the extraction section to be re-saponified. The present invention uses magnesium bicarbonate prepared by high-pressure synthesis as the alkali saponifying agent. The CO2 generated during the saponification process is recycled by the system and then used as the raw material for bicarbonation to prepare magnesium bicarbonate, reducing carbon emissions while lowering production costs; during the saponification process, the ratio conditions are optimized to improve the saponification rate and extraction efficiency;

[0042] (2) Take 1000 mL of the magnesium sulfate waste liquid after extraction, with a magnesium content of 20.34 g / L. Slowly add a strong base, with the molar ratio of magnesium sulfate to the strong base being 1:1. Then add 3 mL of a 10% sodium dodecylbenzenesulfonate solution and 3 g of nano-activated carbon particles. React at a temperature of 46 °C for 2 h until completion. Assist with filtration using a vacuum filter. The filtrate water is returned to step (1) for raw material pulping or for preparing the strong base solution; Put the filter residue and the remaining unfiltered mixed slurry into a high-pressure reactor, add a composite nano-catalyst accounting for 0.1% of the total mass of the reaction system, and then introduce CO2 gas into the reactor under stirring at a flow rate of 1 L / min, maintain the pressure in the reactor at 0.6 MPa, the stirring speed at 280 rpm, react for 2 h at a temperature of 15 °C. After the reaction is completed, perform solid-liquid separation. The solid is insoluble sulfate, and the liquid phase is magnesium bicarbonate solution, with a magnesium content of 21.3 g / L in the magnesium bicarbonate solution; Return this magnesium bicarbonate filtrate to step (1) as a saponifying agent to complete the saponification cycle with a blank organic extractant;

[0043] The preparation method of the composite nano-catalyst is as follows: Weigh 300 mg of porous Fe3O4 nano-particles and disperse them in 150 mL of ethanol, sonicate for 30 min, then add 5 mL of deionized water and mix evenly. Then add 10 mL of 4-triethoxysilylbutyric acid and sonicate for 10 min for dispersion. Place it in an oil bath and heat to 60 °C. Stir rapidly at 60 °C for 7 h, then wash with ethanol 3 times, take out the nano-particles, and dry to obtain carboxylated porous Fe3O4 nano-particles; Disperse 0.08 part of carboxylated porous Fe3O4 nano-particles in 3 parts of deionized water, sonicate for 3 min with a sonication power of 40 kHz, then add La(NO3)3·6H2O to prepare a solution with a concentration of 0.1 - 0.5 mol / L to obtain a mixed solution; Then mix 50 parts of ethanol, 1 part of deionized water, 2 parts of 25% ammonium hydroxide, and 0.24 μL of tetraethyl orthosilicate, react in a water bath at 40 °C for 10 min, add the mixed solution, stir at 120 rpm, react at 40 °C for 8 h, wash alternately with deionized water and absolute ethanol 4 times, rotary evaporate to remove the solvent, and then dry at 60 °C for 12 h. Place the dried particles in a muffle furnace and calcine at 500 °C for 2 h to form a La-doped Fe3O4@SiO2 composite nano-catalyst;

[0044] Preparation of the strong base: The insoluble solid barium salt is washed twice with deionized water, dried at 105 °C for 2 h, and then calcined to prepare barium oxide. Microwave assistance is added during the calcination process, with a microwave power of 500 W, a calcination temperature of 700 °C, and a time of 20 min. After the calcination, it undergoes a combination reaction with deionized water, with a solid-liquid mass ratio of 1:4 and a reaction time of 2 h, resulting in a barium hydroxide solution after reacting with water. It is then put into the production process for recycling; since liquid alkali is no longer used in this invention, it may achieve a one-time input of production water and an infinite cycle of system water. In theory, industrial high-sodium salt wastewater will not be generated, and thus there is no need to build a large-scale water treatment facility.

[0045] Example 2; (1) Using magnesium bicarbonate solution as the saponification reagent, it reacts with P204 blank organic for saponification. During saponification, the volume ratio of the organic phase to the aqueous phase is 1:2, the concentration of P204 is 20%, the saponification temperature is 25 °C, the saponification time is 5 min, and the saponification rate is 60%. The CO2 generated during saponification is transported to the high-pressure reactor in step (3) through a gas recovery device; the saponified organic phase undergoes an extraction reaction with the feed liquid. The zinc concentration in this feed liquid is 2.22 g / L, copper is 1.75 g / L, manganese is 11.08 g / L, and magnesium is 1.5 g / L; the extraction temperature is 30 °C, the number of extraction stages is 10, and the volume ratio of the organic phase to the feed liquid is 1:1.5; after multiple extractions, the raffinate wastewater containing magnesium sulfate is combined with barium hydroxide, and the blank organic phase after back-extraction returns to the extraction section to await re-saponification;

[0046] (2) Take 1000 mL of magnesium sulfate waste liquid from the extraction section. The magnesium element content in the magnesium sulfate waste liquid is 20.15 g / L. Add a strong base to it, with a molar ratio of magnesium sulfate to the strong base of 1:1.05. Then add 3 mL of a 10% sodium dodecylbenzenesulfonate solution and 3 g of nano-activated carbon particles, and react at room temperature for 2 h, with a reaction temperature of 50 °C;

[0047] (3) After the magnesium precipitation reaction is completed, it is filtered with the assistance of a vacuum filter. The filtered aqueous phase returns to step (1) for raw material pulping or for preparing the strong base solution; the filter residue is combined with the remaining mixed slurry and then put into a high-pressure reactor. Add a composite nano-catalyst accounting for 0.3% of the total mass of the reaction system, and then introduce CO2 gas into the reactor under stirring at a flow rate of 1 L / min, maintaining the pressure in the reactor at 0.5 MPa, with a stirring speed of 300 rpm, react for 2.5 h, and the temperature is 19 °C. After the reaction is completed, solid-liquid separation is carried out. The solid is insoluble sulfate, and the liquid phase is magnesium bicarbonate solution, where the magnesium content in the magnesium bicarbonate solution is 20.65 g / L; this magnesium bicarbonate filtrate returns to step (1) as the saponifying agent to complete the saponification cycle with the blank organic extractant;

[0048] The preparation method of the composite nano-catalyst is as follows: Weigh 300 mg of porous Fe3O4 nano-particles and disperse them in 150 mL of ethanol, sonicate for 30 min, then add 5 mL of deionized water and mix evenly. Then add 10 mL of 4-triethoxysilylbutyric acid and sonicate for 10 min for dispersion. Place it in an oil bath and heat to 60 °C. Stir rapidly at 60 °C for 7 h, then wash 3 times with ethanol, take out the nano-particles and dry them to obtain carboxylated porous Fe3O4 nano-particles; Disperse 0.11 part of carboxylated porous Fe3O4 nano-particles in 3 parts of deionized water, sonicate for 3 min with a sonication power of 40 kHz, then add La(NO3)3·6H2O to configure a solution with a concentration of 0.3 mol / L to obtain a mixed solution; Then mix 50 parts of ethanol, 1 part of deionized water, 2 parts of ammonium hydroxide with a concentration of 25% and 0.56 μL of tetraethyl orthosilicate, react in a water bath at 40 °C for 15 min, add the mixed solution, stir at 120 rpm, react at 40 °C for 8 h, wash 4 times alternately with deionized water and absolute ethanol, rotary evaporate to remove the solvent, and then dry at 60 °C for 12 h. Place the dried particles in a muffle furnace and calcine at 550 °C for 3 h to form a La-doped Fe3O4@SiO2 composite nano-catalyst;

[0049] The preparation of the strong base is as follows: Wash the insoluble solid barium salt 3 times with deionized water, dry it at 105 °C for 2 h, and then calcine it to prepare calcium oxide. During the calcination process, microwave assistance is added, the microwave power is 750 W, the calcination temperature is 725 °C, and the time is 30 min. After the calcination, carry out a chemical combination reaction with deionized water, the solid-liquid mass ratio is 1:4, the reaction time is 1.5 h, and it is put into the production process together with the magnesium sulfate wastewater for recycling.

[0050] Example 3; (1) Use magnesium bicarbonate solution as a saponifying agent to react and saponify with the P507 organic phase. During saponification, the volume ratio of the organic phase to the aqueous phase is 1:1.5, the concentration of the P507 extractant is 25%, the saponification temperature is 23 °C, the saponification time is 6 min, and the saponification rate is 55%. The CO2 generated during saponification is transported to the high-pressure reactor in step (3) through a gas recovery device; The saponified organic phase and the feed liquid carry out an extraction reaction. The cobalt concentration in the feed liquid is 72.52 g / L, nickel is 1.67 g / L, and magnesium is 0.25 g / L; The extraction temperature is 34 °C, the number of extraction stages is 10, and the volume ratio of the organic phase to the feed liquid is 1:0.4; After further extracting and recovering nickel, the wastewater containing magnesium sulfate is combined with calcium hydroxide again, and the blank organic phase after back-extraction is returned to the extraction section for re-saponification;

[0051] (2) Preparation of magnesium hydroxide: Take 1000 mL of magnesium sulfate waste liquid from the extraction section. The magnesium element content in the magnesium sulfate waste liquid is 20.2 g / L. Add a strong base to it, with the molar ratio of magnesium sulfate to the strong base being 1:1.05. Then add 4 mL of a 10% sodium dodecylbenzenesulfonate solution and 3 g of nano-activated carbon particles, and react at room temperature for 2 h, with the reaction temperature being 58 °C;

[0052] (3) After the magnesium precipitation reaction ends, filter it with the assistance of a vacuum filter. The filtered aqueous phase is returned to step (1) for raw material pulping to prepare the strong base solution; Combine the filter residue with the remaining mixed slurry and put it into a high-pressure reactor. Add a composite nano-catalyst accounting for 0.5% of the total mass of the reaction system. Then, while stirring, introduce CO2 gas into the reactor at a flow rate of 1 L / min, keep the pressure in the reactor at 0.55 MPa, the stirring speed at 265 rpm, react for 2.5 h, and the temperature at 23 °C. After the reaction ends, perform solid-liquid separation. The solid is insoluble sulfate, and the liquid phase is magnesium bicarbonate solution, in which the magnesium content in the magnesium bicarbonate solution is 20.39 g / L; Return this magnesium bicarbonate filtrate to step (1) as a saponifying agent to complete the saponification cycle with the blank organic extractant;

[0053] The preparation method of the composite nano-catalyst is as follows: Weigh 300 mg of porous Fe3O4 nano-particles and disperse them in 150 mL of ethanol. Ultrasonic for 30 min, then add 5 mL of deionized water and mix evenly. Then add 10 mL of 4-triethoxysilylbutyric acid and ultrasonic for 10 min to disperse. Place it in an oil bath and heat to 60 °C. Under the condition of 60 °C, stir rapidly for 7 h. Then wash it with ethanol 3 times, take out the nano-particles, and dry them to obtain carboxylated porous Fe3O4 nano-particles; Disperse 0.15 parts of carboxylated porous Fe3O4 nano-particles in 3 parts of deionized water, ultrasonic for 3 min, with the ultrasonic power being 40 kHz. Then add La(NO3)3·6H2O to prepare a solution with a concentration of 0.5 mol / L to obtain a mixed solution; Then mix 50 parts of ethanol, 1 part of deionized water, 2 parts of 25% ammonium hydroxide, and 0.9 μL of tetraethyl orthosilicate, react in a water bath at 40 °C for 20 min, add the mixed solution, stir at 120 rpm, react at 40 °C for 8 h, wash it alternately with deionized water and absolute ethanol 4 times, rotary evaporate to remove the solvent, and then dry it at 60 °C for 12 h. Place the dried particles in a muffle furnace and calcine at 600 °C for 4 h to form a La-doped Fe3O4@SiO2 composite nano-catalyst;

[0054] The strong base: The insoluble solid barium salt is washed twice with deionized water, dried at 105 °C for 2 h, and calcined to prepare barium oxide. Microwave assistance is added during the calcination process. The microwave power is 1000 W, the calcination temperature is 750 °C, and the time is 40 min. After the calcination, it undergoes a combination reaction with deionized water. The solid-liquid mass ratio is 1:4, the reaction time is 1.5 h, and it is put into the production process together with the magnesium sulfate wastewater for recycling.

[0055] Example 4; (1) Using magnesium bicarbonate solution as the saponification reagent, it reacts with the P204 blank organic for saponification. When saponifying, the volume ratio of the organic phase to the aqueous phase is 1:2, the concentration of P204 is 20%, the saponification temperature is 25 °C, the saponification time is 5 min, and the saponification rate is 60%. The CO2 generated during saponification is transported to the high-pressure reactor in step (3) through a gas recovery device; the saponified organic phase undergoes an extraction reaction with the feed liquid. The zinc concentration in this feed liquid is 2.22 g / L, copper is 1.75 g / L, manganese is 11.08 g / L, and magnesium is 1.5 g / L; the extraction temperature is 30 °C, the number of extraction stages is 10, and the volume ratio of the organic phase to the feed liquid is 1:1.5; after multiple extractions, the raffinate wastewater containing magnesium sulfate reacts with calcium hydroxide, and the blank organic phase after back-extraction returns to the extraction section to be saponified again;

[0056] (2) Take 1000 mL of the magnesium sulfate waste liquid from the extraction section. The magnesium element content in the magnesium sulfate waste liquid is 20.15 g / L. Add solid barium salt to it. The molar ratio of magnesium sulfate to the solid barium salt is 1:1.05. Then add 3 mL of a 10% sodium dodecylbenzenesulfonate solution and 3 g of nano-activated carbon particles, and react at room temperature for 2 h. The reaction temperature is 50 °C;

[0057] (3) After the magnesium precipitation reaction is completed, it is filtered with the assistance of a vacuum filter. The filtered aqueous phase returns to step (1) for raw material pulping to prepare the strong base solution; the filter residue is combined with the remaining mixed slurry and then put into a high-pressure reactor. Then, CO2 gas is introduced into the reactor under stirring at a flow rate of 1 L / min, keeping the pressure in the reactor at 0.5 MPa, the stirring speed at 300 rpm, reacting for 2.5 h, and the temperature at 19 °C. After the reaction, solid-liquid separation is carried out. The solid is insoluble sulfate, and the liquid phase is magnesium bicarbonate solution, where the magnesium content in the magnesium bicarbonate solution is 20.65 g / L; this magnesium bicarbonate filtrate returns to step (1) as the saponifying agent to complete the saponification cycle with the blank organic extractant.

[0058] Effect example

[0059] The following Table 1-4 gives the performance analysis results of the raffinate content in one cycle using Examples 1 to 4 of the present invention.

[0060] Table 1 Comparison of data before and after the raffinate metal content in one cycle of Example 1

[0061] Zinc Copper Manganese Magnesium Before Implementation 1 2.22 1.75 11.08 1.5 After Implementation 1 0.0003 0.00065 0.00092 21.05

[0062] Table 2 Comparison of data on the content of residual metals before and after the first cycle in Example 2

[0063] Zinc Copper Manganese Magnesium Before Implementation 2 2.22 1.75 11.08 1.5 After Implementation 2 0.0004 0.00078 0.0011 19.96

[0064] Table 3 Comparison of data on the content of residual metals before and after the first cycle in Example 3

[0065] Cobalt Nickel Magnesium Before Implementation 3 72.52 1.67 0.25 After Implementation 3 0.0023 1.52 20.41

[0066] Table 4 Comparison of data on the content of residual metals before and after the first cycle in Example 4

[0067] Zinc Copper Manganese Magnesium Before Implementation 4 2.22 1.75 11.08 1.5 After Implementation 4 0.0011 0.0023 0.0025 20.71

[0068] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-described exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention. Any reference signs in the claims should not be construed as limiting the claims involved.

Claims

1. A method for recycling magnesium salts and carbon dioxide, characterized in that: The method comprises the following steps: (1) taking 1000 mL of magnesium sulfate waste liquid remaining after extraction, adding a strong alkaline aqueous solution thereto so that the molar ratio of magnesium sulfate to the strong base is 1:1-1.05, then adding 3-4 ml of a 10% sodium dodecylbenzene sulfonate solution and 3 g of nano-activated carbon particles, reacting at room temperature for 2 h, the reaction temperature being 40-60° C.; wherein the source of the strong base is: a solid barium salt is washed twice with deionized water, dried at 105° C. for 2 h, and then calcined to prepare barium oxide, microwave assistance is added during the calcination process, the microwave power is 500-1000 W, the calcination temperature is 700-750° C., the time is 20-40 min, and after the calcination is completed, it is mixed with deionized water for reaction, the solid-liquid mass ratio is 1:3-5, the reaction time is 2 h, and a strong alkaline aqueous solution is formed after chemical reaction with water, which is put into the production link for recycling; (2) After the reaction is completed, a portion of the slurry is filtered with the aid of a vacuum filter, and the filtered water phase is returned to the raw material slurry pretreatment section or step (1) for preparation of a strong alkaline aqueous solution; the filter residue and the remaining unfiltered mixed slurry are placed in a high-pressure reactor, and a composite nano-catalyst of 0.1-0.5% of the total mass of the reaction system is added, and then CO2 gas is introduced into the reactor under stirring at a gas flow rate of 1 L / min, and the pressure in the reactor is maintained at 0.5-0.6 MPa. The reaction is carried out for 1.5-3.5 hours at a temperature of 5-35°C. After the reaction is completed, solid-liquid separation is performed, and the solid is an insoluble sulfate, and the liquid aqueous phase is a magnesium bicarbonate solution.

2. The method for recycling magnesium salt and carbon dioxide according to claim 1, characterized in that: In step (1), the magnesium sulfate waste liquid in the extraction section is sourced from the mixed liquid to be extracted and the magnesium bicarbonate solution is used as a saponification reagent to react with the blank organic phase. During the saponification, the volume ratio of the organic phase to the aqueous phase is 1:1.5-2, the concentration of the blank organic phase is 20-25%, the saponification temperature is 20-40°C, the saponification time is 6 minutes, the saponification rate is 50-60%, the carbon dioxide generated during the saponification process is recovered and re-pressurized for utilization, and the organic phase after soap and the multi-metal mixed solution enter the extraction; the temperature is set to 30-45°C, the extraction level is 10, and the volume ratio of the organic phase to the liquid is 1:0.3-3; the raffinate wastewater magnesium sulfate reacts with a strong base as a raw material for combining magnesium bicarbonate, and the blank organic phase after stripping returns to the extraction section to participate in saponification again.

3. The method for recycling magnesium salt and carbon dioxide according to claim 2, characterized in that: The blank organic compound is P204 or P507 or Cyanex272.

4. The method for recycling magnesium salt and carbon dioxide according to claim 2, characterized in that: The metal components in the metal solution include one or more of Cu, Mn, Zn, Co, Ni, Ca, and Mg.

5. The method for recycling magnesium salt and carbon dioxide according to claim 1, characterized in that: The magnesium content in the magnesium sulfate waste liquid in step (1) is 10-21 g / L.

6. The method for recycling magnesium salt and carbon dioxide according to claim 1, characterized in that: The strong base in step (1) can be barium hydroxide or calcium hydroxide.

7. The method for recycling magnesium salt and carbon dioxide according to claim 1, characterized in that: The composite nanocatalyst in step (2) is La-doped Fe3O4@SiO2, and the preparation method is as follows: 0.08-0.15 parts of carboxylated porous Fe3O4 nanoparticles are dispersed in 3 parts of deionized water, ultrasonicated for 3 minutes, the ultrasonic power is 40kHz, and then La(NO3)3·6H2O is added to prepare a concentration of 0.1-0.5 mol / L to obtain a mixed solution; then 50 parts of ethanol, 1 part of deionized water, 2 parts of ammonium hydroxide with a concentration of 25% and 0.24-0.9 μL of tetraethyl orthosilicate are mixed, reacted in a water bath at 40°C for 10-20 minutes, added to the mixed solution, stirred at 120rpm, reacted at 40°C for 8h, washed alternately with deionized water and anhydrous ethanol for 4 times, rotary evaporated to remove the solvent, and then dried at 60°C for 12h, the dried particles are placed in a muffle furnace, and calcined at 500-600°C for 2-4h to form a La-doped Fe3O4@SiO2 composite nanocatalyst.

8. The method for recycling magnesium salt and carbon dioxide according to claim 1, characterized in that: The reaction speed in the high-pressure reactor in step (2) is 200-350 rpm.

9. The method for recycling magnesium salt and carbon dioxide according to claim 1, characterized in that: The magnesium content in the magnesium bicarbonate filtrate produced after the pressure reaction in step (2) is 10-22 g / L.