A process for preparing high-purity lead oxide

Abstract

The present invention discloses a process for preparing high-purity lead oxide. By utilizing four core technologies, namely, green leaching using citric acid and hydrogen peroxide, deep purification using a chelating resin and nanofiltration membrane, hydrothermal synthesis of crystal phases, and microwave low-temperature calcination, the process achieves a comprehensive breakthrough in the preparation of high-purity lead oxide. The process achieves a product purity of 99.999% (5N grade), a β-phase content of >99%, and a grain size of 50-80 nm. Compared with traditional methods, the process energy consumption is reduced by 60-70%, the lead recovery rate is >95%, and the raw material cost is reduced by 40%. The process completely eliminates the emission of harmful gases such as SO2, and the heavy metal leaching rate is <0.1%, complying with RoHS environmental protection standards. The process speed is increased by five times compared with traditional crystallization methods, and the resin can be reused more than 10 times. The process achieves the technical goals of "high purity, low energy consumption, and zero pollution," providing a feasible industrialization path for the large-scale green production of electronic-grade lead oxide.

Description

Technical Field

[0001] The present invention relates to the field of metallurgy technology, and in particular to a process for preparing high-purity lead oxide. Background Art

[0002] High-purity lead oxide (PbO), a key electronic material, is widely used in high-end applications such as multilayer ceramic capacitors (MLCCs), perovskite solar cells, and radiation-shielding glass. As electronic devices evolve towards miniaturization and high reliability, stringent requirements are placed on PbO's purity (≥99.999%), crystal phase uniformity (β-phase >99%), and nanostructure controllability. However, existing industrial preparation technologies are limited by outdated process routes, poor environmental performance, and high energy consumption, making it difficult to meet the performance requirements of the next generation of electronic devices. Traditional processes use lead ingots or lead ore as raw material, reducing lead paste (PbSO4 / PbO2) through high-temperature smelting (800-1000°C). This consumes large amounts of coke and releases pollutants such as SO2 and lead dust. Taking a typical pyrometallurgical-wet metallurgical combined process as an example, the production of 1 ton of PbO consumes 1200-1500 kWh of electricity and emits 200-300 kg of CO2 and 5-10 kg of SO2, seriously violating the "Integrated Emission Standard of Air Pollutants" (GB16297-1996). In addition, the wet metallurgical process for recycling lead from waste lead-acid batteries mostly uses sulfuric acid leaching. Although it can dissolve PbSO4, PbO2 requires the addition of Fe 2+ / Na2SO3 and other reducing agents, resulting in Fe 3+ 、Sb 3+ If the concentration of impurity ions exceeds the standard (>100ppm), subsequent multi-stage chemical precipitation purification is required. The process is lengthy and the lead recovery rate is only 80%~85%, resulting in a waste of resources.

[0003] The existing purification process relies on multiple crystallization-redissolution (usually 5 to 8 cycles) combined with activated carbon adsorption, which has two major drawbacks: purity limitation and high cost constraints. 2+ 、Fe 3+ etc. and Pb 2+The separation efficiency of metal impurities with similar solubility is low, and the purity of the final solution is only 99.9%~99.99% (3N~4N grade), which is difficult to meet the requirements of 5N grade electronic materials. At the same time, a single crystallization takes 8~12 hours, and 5%~10% of the lead raw material is lost with each cycle. The annual loss cost of a thousand-ton production line exceeds 5 million yuan. In addition, activated carbon needs to be regenerated at high temperature (300~400℃) after adsorption, further increasing energy consumption and carbon emissions. The mainstream solid-phase calcination method heat treats PbO or Pb(OH)2 at 600~800℃ for 4~6 hours, which also has many problems: at high temperature, α-PbO (tetragonal phase) and β-PbO (orthorhombic phase) coexist, and the mixing rate is as high as 5%~10%, while electronic devices require a single β phase (for example, MLCC dielectrics require the stable dielectric properties of β-PbO); long-term high temperature causes the grains to grow to the micron level (1~5μm), with a specific surface area of less than 1m 2 / g, and when used as a hole transport layer in perovskite cells, the interface contact is poor, and the device efficiency is limited (<18%); the calcination process accounts for more than 60% of the energy consumption of the entire process, and relies on natural gas / coal heating, with a carbon emission intensity of 2.1tCO2 / tPbO.

[0004] The traditional process adopts the "pollution first, treatment later" model, which has prominent environmental problems: SO2 in smelting waste gas relies on limestone-gypsum desulfurization, with a removal efficiency of only 90%~95%, and residual SO2 (50~100mg / m 3 ) still exceeds the new national standard (GB39728-2020 limit of 35mg / m 3 ); Lead-containing wastewater (Pb 2+ >5ppm) requires sodium sulfide precipitation treatment, which produces hazardous waste lead sludge (HW31 category), with a disposal cost of 8,000 to 10,000 yuan / ton; the valuable metals such as antimony (Sb) and tin (Sn) associated with the lead paste are not recovered. For an enterprise with an annual output of 10,000 tons, the annual loss of metal value exceeds 20 million yuan. The lagging technology upgrade is also a major problem. The purity of the current commercially available PbO products is generally 99.9% to 99.99% (3N to 4N), and the crystal form and particle size distribution are uneven, resulting in the need for additional purification (such as vacuum distillation) for downstream electronic companies, which increases costs by 30% to 50%. Taking perovskite solar cells as an example, due to the insufficient purity of traditional PbO (Fe content>10ppm), Fe 3+ / Cu 2+ This induces carrier recombination, causing the device efficiency to decay at a rate exceeding 1% per thousand hours, seriously restricting the commercialization process.

[0005] Existing high-purity lead oxide production technologies are hampered by systemic flaws such as high pollution levels in raw material processing, inefficient solution purification, high energy consumption in the synthesis process, and incomplete environmental management. These flaws result in low product purity, uncontrollable crystal phases, and high costs, making it difficult to meet the demand for high-end and green electronic materials. The industry urgently needs an innovative process that integrates resource recycling, low-temperature synthesis, and closed-loop environmental protection to overcome the "purity-energy-environmental" dilemma and promote the upgrading of the electronic chemicals industry. Summary of the Invention

[0006] In order to solve or partially solve the problems existing in the related art, the present invention provides a process for preparing high-purity lead oxide.

[0007] The following steps are involved:

[0008] (1) Raw material pretreatment and electrolytic refining: crush the lead paste of waste lead-acid batteries to a particle size of ≤100 mesh, and leach it with a mixture of citric acid solution and hydrogen peroxide, wherein the citric acid concentration is 0.1-1 mol / L, the hydrogen peroxide concentration is 1-5wt%, the liquid-solid ratio is (5-15):1, the leaching temperature is 50-70℃, and the leaching time is 2-6 hours; electrolytically refine the leachate at a current density of 150-250A / m 2 , the pH of the electrolyte is 2-4, the electrolysis temperature is 30-50°C, and the cathode obtains metallic lead with a purity of ≥99.99%;

[0009] The raw material pretreatment and electrolytic refining technology is based on the citric acid-hydrogen peroxide leaching system and electrochemical separation principle. Citric acid (C6H8O7) as an organic acid works synergistically with H2O2 to convert PbSO4 and PbO2 in the lead paste into soluble lead citrate complex (Pb(C6H6O7)), avoiding the production of SO2 gas by traditional sulfuric acid leaching. H2O2 acts as an oxidant to promote the reduction and dissolution of PbO2 (Pb 4+ →Pb 2+ ), while suppressing the formation of sulfides. Electrorefining is based on the selectivity of metal electrochemical deposition: the reduction potential of lead (-0.13V vs. SHE) is lower than that of impurity metals (such as Cu 2+ :+0.34V,Fe 3+ : +0.77V), high-purity lead is preferentially deposited at the cathode, while impurities are dissolved by oxidation at the anode. The titanium-based IrO2-Ta2O5 anode offers strong corrosion resistance, avoiding the dissolution contamination associated with traditional lead anodes. This process offers significant technical advantages: environmentally friendly, with no sulfur oxide emissions, a heavy metal leaching rate of <0.1%, and RoHS compliance. It is highly efficient and energy-efficient, with a lead recovery rate of >95% and 70% lower energy consumption than pyrometallurgical reduction. It also boasts strong raw material compatibility, allowing direct processing of waste battery lead paste, reducing raw material costs by 40%.

[0010] (2) Purification of lead nitrate solution: reacting the metallic lead obtained in step (1) with 4-8 mol / L nitric acid at a molar ratio of 1:(2-4) and a dissolution temperature of 40-80°C to obtain a Pb(NO3)2 solution; purifying the solution by passing it through a chelating resin column and a nanofiltration membrane in sequence, wherein the chelating resin is a DTPA-modified polystyrene-based resin, the nanofiltration membrane has a molecular weight cut-off of 100-300 Da, and the operating pressure is 1-2 MPa;

[0011] The deep purification technology of lead nitrate solution adopts a dual purification mechanism of chelating resin adsorption and nanofiltration membrane separation. The chelating resin modified with DTPA (diethylenetriaminepentaacetic acid) preferentially binds transition metal ions (Cu 2+ 、Fe 3+ ), while for Pb 2+ The complexing ability is weak (selectivity coefficient Cu 2+ / Pb 2+ =10 3 During the dynamic adsorption process, impurity ions are fixed and lead ions flow out with the solution. Nanofiltration membrane separation uses a polyamide membrane with a pore size of 200Da to screen colloidal particles (>2nm) and large molecular organic matter, while rejecting multivalent ions (such as SO4 2- ), retain Pb 2+ This technology achieves ultra-high purity, with metal impurity content less than 1ppm and solution purity reaching 5N level (99.999%); low operating costs, the resin can be regenerated more than 10 times, and the energy consumption of membrane separation is only 20% of that of distillation; it also has a fast processing speed, with purification speed increased by 5 times compared to traditional crystallization methods.

[0012] (3) Hydrothermal synthesis of precursor: The purified Pb(NO3)2 solution was mixed with ammonia water in a molar ratio of 1:(1-1.5), the pH was adjusted to 9-11, and the mixture was transferred to a hydrothermal reactor and reacted at 150-200°C for 4-8 hours to generate β-Pb(OH)2 nanosheet precursor;

[0013] The hydrothermal synthesis of β-PbO precursor technology achieves high-quality precursor preparation through crystal phase regulation and morphology control. Under alkaline hydrothermal conditions (pH=10.5), Pb 2+ With OH - Formation of [Pb(OH)3] -The intermediate, through the Ostwald ripening mechanism, preferentially grows into hexagonal β-Pb(OH)2 nanosheets along the (001) crystal plane. High temperature (180°C) and high pressure (1.2MPa) promote lattice reorganization and inhibit the formation of α phase. Ammonia water is used as a mineralizer to adjust the supersaturation of the solution, limit the three-dimensional growth of particles, and form a two-dimensional sheet structure. This process can obtain a single crystal phase with a β-PbO content of >99%, avoiding the traditional solid-phase method of α / β mixed phase (mixing ratio <0.5%); prepare nanostructures with a sheet thickness of 20-50nm and a specific surface area of 25m 2 / g, improving the activity of subsequent calcination reaction; achieving low-temperature synthesis, the reaction temperature is 70% lower than the traditional high-temperature solid-phase method (>600℃).

[0014] (4) Microwave calcination conversion: Place the precursor in a microwave reactor, heat it to 250-350°C at 5-15°C / min under an oxygen atmosphere, and calcine it for 1-3 hours to obtain β-PbO product;

[0015] Microwave low temperature calcination technology is based on microwave selective heating and oxidative dehydroxylation mechanism. Polar molecules (H2O, OH)2 in β-Pb(OH)2 - ) generates molecular frictional heat in a 2.45GHz microwave field, achieving rapid and uniform heating within the material. Inert carriers (such as quartz crucibles) absorb little microwave radiation. In an oxygen atmosphere, β-Pb(OH)2 loses its structural hydroxyl group (-OH) to form β-PbO (reaction equation: Pb(OH)2→PbO+H2O↑). The oxygen flow suppresses carbonization of organic residues. This technology achieves energy savings and reduces consumption, with a calcination temperature of 300°C (compared to 500°C required by traditional processes), reducing energy consumption by 60%. It also eliminates carbon pollution, with the product exhibiting no carbon deposits in an oxygen atmosphere and achieving a purity of 99.999% (5N). Furthermore, the rapid microwave heating suppresses grain coarsening, resulting in grain sizes of 50-80nm and excellent dispersion.

[0016] (5) Closed-loop environmental protection treatment: waste gas is condensed to recover nitric acid, and the remaining gas is passed into alkaline solution for absorption; waste water is treated by a combination of reverse osmosis and electrodialysis, with a water reuse rate of ≥90%; electrolytic residue is treated by acid leaching and extraction to recover valuable metals.

[0017] Furthermore, in step (1), the concentration of citric acid is 0.5 mol / L, the concentration of hydrogen peroxide is 3 wt %, the liquid-solid ratio is 10:1, the leaching temperature is 60° C., and the leaching time is 4 hours.

[0018] Furthermore, the current density of the electrolytic refining in step (1) is 200A / m 2 , the electrolyte pH is 3, and the electrolysis temperature is 40℃.

[0019] Furthermore, the nitric acid concentration in step (2) is 6 mol / L, the molar ratio of metallic lead to nitric acid is 1:3, and the dissolution temperature is 60°C.

[0020] Furthermore, the molecular weight cut-off of the nanofiltration membrane in step (2) is 200 Da, and the operating pressure is 1.5 MPa.

[0021] Furthermore, in step (3), the concentration of aqueous ammonia is 25%, the molar ratio of Pb(NO3)2 to aqueous ammonia is 1:1.2, the pH is adjusted to 10.5, the hydrothermal reaction temperature is 180°C, and the reaction time is 6 hours.

[0022] Furthermore, in step (4), the microwave frequency is 2.45 GHz, the heating rate is 10°C / min, the calcination temperature is 300°C, the calcination time is 2 hours, and the oxygen flow rate is 30-70 mL / min.

[0023] Furthermore, the exhaust gas condensation temperature in step (5) is -20-0°C, and the alkaline solution is 5-10wt% NaOH solution.

[0024] Furthermore, the reverse osmosis membrane desalination rate in step (5) is ≥98%, and the purity of ammonium nitrate recovered by electrodialysis is ≥99%.

[0025] Furthermore, in step (5), the acid leaching of the electrolytic residue adopts 4-6 mol / L hydrochloric acid, the extractant is Cyanex923, and the antimony recovery rate is ≥90%.

[0026] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present invention.

[0027] Beneficial technical effects of the present invention:

[0028] This innovative process achieves a comprehensive breakthrough in the preparation of high-purity lead oxide through four core technologies: green leaching with citric acid and hydrogen peroxide, deep purification with chelating resin and nanofiltration membrane, hydrothermal synthesis and crystal phase regulation, and microwave low-temperature calcination. The product purity reaches 99.999% (5N grade), the β-phase content is >99%, and the grain size is controlled at 50-80nm. The process energy consumption is reduced by 60-70% compared with traditional methods, the lead recovery rate is >95%, and the raw material cost is reduced by 40%. The emission of harmful gases such as SO2 is completely eliminated, the heavy metal leaching rate is <0.1%, and it complies with RoHS environmental protection standards. The processing speed is increased by 5 times compared with traditional crystallization methods, and the resin can be reused more than 10 times, achieving the technical goals of "high purity, low energy consumption, and zero pollution", and providing a feasible industrialization path for the large-scale green production of electronic-grade lead oxide. DETAILED DESCRIPTION

[0029] The following describes alternative embodiments of the present invention in more detail. Although alternative embodiments of the present invention are described, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. Instead, these embodiments are provided to make the present invention more thorough and complete, and to fully convey the scope of the present invention to those skilled in the art.

[0030] The terms used in this application are for the purpose of describing specific embodiments only and are not intended to limit this application. The singular forms "a," "an," "the," and "the" used in this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term "and / or" as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.

[0031] The present invention provides a process for preparing high-purity lead oxide.

[0032] The following steps are involved:

[0033] (1) Raw material pretreatment and electrolytic refining: crush the lead paste of waste lead-acid batteries to a particle size of ≤100 mesh, and leach it with a mixture of citric acid solution and hydrogen peroxide, wherein the citric acid concentration is 0.1-1 mol / L, the hydrogen peroxide concentration is 1-5wt%, the liquid-solid ratio is (5-15):1, the leaching temperature is 50-70℃, and the leaching time is 2-6 hours; electrolytically refine the leachate at a current density of 150-250A / m 2 , the pH of the electrolyte is 2-4, the electrolysis temperature is 30-50°C, and the cathode obtains metallic lead with a purity of ≥99.99%;

[0034] (2) Purification of lead nitrate solution: reacting the metallic lead obtained in step (1) with 4-8 mol / L nitric acid at a molar ratio of 1:(2-4) and a dissolution temperature of 40-80°C to obtain a Pb(NO3)2 solution; purifying the solution by passing it through a chelating resin column and a nanofiltration membrane in sequence, wherein the chelating resin is a DTPA-modified polystyrene-based resin, the nanofiltration membrane has a molecular weight cut-off of 100-300 Da, and the operating pressure is 1-2 MPa;

[0035] (3) Hydrothermal synthesis of precursor: The purified Pb(NO3)2 solution was mixed with ammonia water in a molar ratio of 1:(1-1.5), the pH was adjusted to 9-11, and the mixture was transferred to a hydrothermal reactor and reacted at 150-200°C for 4-8 hours to generate β-Pb(OH)2 nanosheet precursor;

[0036] (4) Microwave calcination conversion: Place the precursor in a microwave reactor, heat it to 250-350°C at 5-15°C / min under an oxygen atmosphere, and calcine it for 1-3 hours to obtain β-PbO product;

[0037] (5) Closed-loop environmental protection treatment: waste gas is condensed to recover nitric acid, and the remaining gas is passed into alkaline solution for absorption; waste water is treated by a combination of reverse osmosis and electrodialysis, with a water reuse rate of ≥90%; electrolytic residue is treated by acid leaching and extraction to recover valuable metals.

[0038] In one embodiment of the present invention, the citric acid concentration in step (1) is 0.5 mol / L, the hydrogen peroxide concentration is 3 wt %, the liquid-solid ratio is 10:1, the leaching temperature is 60° C., and the leaching time is 4 hours.

[0039] In one embodiment of the present invention, the current density of the electrolytic refining in step (1) is 200A / m 2 , the electrolyte pH is 3, and the electrolysis temperature is 40℃.

[0040] In one embodiment of the present invention, the concentration of nitric acid in step (2) is 6 mol / L, the molar ratio of metallic lead to nitric acid is 1:3, and the dissolution temperature is 60°C.

[0041] In one embodiment of the present invention, the molecular weight cut-off of the nanofiltration membrane in step (2) is 200 Da, and the operating pressure is 1.5 MPa.

[0042] In one embodiment of the present invention, the concentration of the aqueous ammonia is 25%, the molar ratio of Pb(NO3)2 to aqueous ammonia is 1:1.2, the pH is adjusted to 10.5, the hydrothermal reaction temperature is 180°C, and the reaction time is 6 hours.

[0043] In one embodiment of the present invention, the microwave frequency in step (4) is 2.45 GHz, the heating rate is 10°C / min, the calcination temperature is 300°C, the calcination time is 2 hours, and the oxygen flow rate is 30-70 mL / min.

[0044] In one embodiment of the present invention, the exhaust gas condensation temperature in step (5) is -20-0°C, and the alkaline solution is a 5-10 wt% NaOH solution.

[0045] In one embodiment of the present invention, the reverse osmosis membrane desalination rate in step (5) is ≥98%, and the purity of ammonium nitrate recovered by electrodialysis is ≥99%.

[0046] In one embodiment of the present invention, the acid leaching of the electrolytic residue in step (5) adopts 4-6 mol / L hydrochloric acid, the extractant is Cyanex923, and the antimony recovery rate is ≥90%.

[0047] For the purpose of greater clarity, the present invention is described in detail with reference to the following examples.

[0048] Example 1: Steps and parameters

[0049] 1. Raw material pretreatment and electrolytic refining

[0050] Lead paste particle size: 100 mesh

[0051] Leaching solution: citric acid 1mol / L + hydrogen peroxide 5wt%, liquid-to-solid ratio 15:1, leaching at 70℃ for 6 hours

[0052] Electrolysis conditions: current density 250A / m 2 , pH=4, electrolyte temperature 50℃

[0053] 2. Purification of lead nitrate solution

[0054] Nitric acid concentration 8 mol / L, lead to nitric acid molar ratio 1:4, dissolution temperature 80°C

[0055] Nanofiltration membrane molecular weight cut-off 300Da, operating pressure 2MPa

[0056] 3. Hydrothermal synthesis of precursors

[0057] Ammonia addition amount: Pb(NO3)2 to ammonia molar ratio 1:1.5, pH=11

[0058] Hydrothermal conditions: 200℃ for 8 hours

[0059] 4. Microwave calcination conversion

[0060] Heating rate 15℃ / min, calcination temperature 350℃, time 3 hours, oxygen flow rate 70mL / min

[0061] 5. Closed-loop environmental protection treatment

[0062] Exhaust gas condensation temperature -20℃, NaOH concentration 10wt%

[0063] The reverse osmosis desalination rate is 98%, and the purity of ammonium nitrate recovered by electrodialysis is 99%.

[0064] Acid leaching of electrolytic residue: hydrochloric acid 6mol / L, Cyanex923 extraction

[0065] result

[0066]

[0067] Example 2: Steps and parameters

[0068] 1. Raw material pretreatment and electrolytic refining

[0069] Lead paste particle size: 100 mesh

[0070] Leaching solution: citric acid 0.5mol / L + hydrogen peroxide 3wt%, liquid-to-solid ratio 10:1, leaching at 60℃ for 4 hours

[0071] Electrolysis conditions: current density 200A / m 2 , pH=3, electrolyte temperature 40℃

[0072] 2. Purification of lead nitrate solution

[0073] Nitric acid concentration 6 mol / L, lead to nitric acid molar ratio 1:3, dissolution temperature 60 ° C

[0074] Nanofiltration membrane molecular weight cut-off 200Da, operating pressure 1.5MPa

[0075] 3. Hydrothermal synthesis of precursors

[0076] Ammonia addition amount: Pb(NO3)2 to ammonia molar ratio 1:1.2, pH=10.5

[0077] Hydrothermal conditions: 180℃ for 6 hours

[0078] 4. Microwave calcination conversion

[0079] Heating rate 10℃ / min, calcination temperature 300℃, time 2 hours, oxygen flow rate 50mL / min

[0080] 5. Closed-loop environmental protection treatment

[0081] Exhaust gas condensation temperature -10°C, NaOH concentration 7.5wt%

[0082] The reverse osmosis desalination rate is 98.5%, and the purity of ammonium nitrate recovered by electrodialysis is 99.2%.

[0083] Acid leaching of electrolytic residue: hydrochloric acid 5mol / L, Cyanex923 extraction

[0084] result

[0085]

[0086] Example 3: Steps and parameters

[0087] 1. Raw material pretreatment and electrolytic refining

[0088] Lead paste particle size: 100 mesh

[0089] Leaching solution: 0.1mol / L citric acid + 1wt% hydrogen peroxide, liquid-to-solid ratio 5:1, leaching at 50℃ for 2 hours

[0090] Electrolysis conditions: current density 150A / m 2 , pH=2, electrolyte temperature 30℃

[0091] 2. Purification of lead nitrate solution

[0092] Nitric acid concentration 4 mol / L, lead to nitric acid molar ratio 1:2, dissolution temperature 40°C

[0093] Nanofiltration membrane molecular weight cut-off 100Da, operating pressure 1MPa

[0094] 3. Hydrothermal synthesis of precursors

[0095] Ammonia addition amount: Pb(NO3)2 to ammonia molar ratio 1:1, pH=9

[0096] Hydrothermal conditions: 150℃ for 4 hours

[0097] 4. Microwave calcination conversion

[0098] Heating rate 5℃ / min, calcination temperature 250℃, time 1 hour, oxygen flow rate 30mL / min

[0099] 5. Closed-loop environmental protection treatment

[0100] Exhaust gas condensation temperature 0℃, NaOH concentration 5wt%

[0101] The reverse osmosis desalination rate is 98%, and the purity of ammonium nitrate recovered by electrodialysis is 99%.

[0102] Acid leaching of electrolytic residue: hydrochloric acid 4mol / L, Cyanex923 extraction

[0103] result

[0104]

[0105] Test example

[0106] 1. Comparison of process flow and parameters

[0107]

[0108] 2. Comparison of key performance data

[0109]

[0110] 3. Environmental protection index testing

[0111]

[0112] 4. Economic analysis (based on 1,000-ton production capacity)

[0113]

Claims

1. A process for preparing high-purity lead oxide, characterized in that: The following steps are involved: (1) Raw material pretreatment and electrolytic refining: crush the lead paste of waste lead-acid batteries to a particle size of ≤100 mesh, and leach it with a mixture of citric acid solution and hydrogen peroxide, wherein the citric acid concentration is 0.1-1 mol / L, the hydrogen peroxide concentration is 1-5wt%, the liquid-solid ratio is (5-15):1, the leaching temperature is 50-70℃, and the leaching time is 2-6 hours; electrolytically refine the leachate at a current density of 150-250A / m 2 , the pH of the electrolyte is 2-4, the electrolysis temperature is 30-50°C, and the cathode obtains metallic lead with a purity of ≥99.99%; (2) Purification of lead nitrate solution: reacting the metallic lead obtained in step (1) with 4-8 mol / L nitric acid at a molar ratio of 1:(2-4) and a dissolution temperature of 40-80°C to obtain a Pb(NO3)2 solution; purifying the solution by passing it through a chelating resin column and a nanofiltration membrane in sequence, wherein the chelating resin is a DTPA-modified polystyrene-based resin, the nanofiltration membrane has a molecular weight cut-off of 100-300 Da, and the operating pressure is 1-2 MPa; (3) Hydrothermal synthesis of precursor: The purified Pb(NO3)2 solution was mixed with ammonia water in a molar ratio of 1:(1-1.5), the pH was adjusted to 9-11, and the mixture was transferred to a hydrothermal reactor and reacted at 150-200°C for 4-8 hours to generate β-Pb(OH)2 nanosheet precursor; (4) Microwave calcination conversion: Place the precursor in a microwave reactor, heat it to 250-350°C at 5-15°C / min under an oxygen atmosphere, and calcine it for 1-3 hours to obtain β-PbO product; (5) Closed-loop environmental protection treatment: waste gas is condensed to recover nitric acid, and the remaining gas is passed into alkaline solution for absorption; waste water is treated by a combination of reverse osmosis and electrodialysis, with a water reuse rate of ≥90%; electrolytic residue is treated by acid leaching and extraction to recover valuable metals.

2. The process according to claim 1, characterized in that In step (1), the concentration of citric acid is 0.5 mol / L, the concentration of hydrogen peroxide is 3 wt %, the liquid-solid ratio is 10:1, the leaching temperature is 60° C., and the leaching time is 4 hours.

3. The process according to claim 1, characterized in that The current density of the electrolytic refining in step (1) is 200A / m 2 , the electrolyte pH is 3, and the electrolysis temperature is 40℃.

4. The process according to claim 1, characterized in that The nitric acid concentration in step (2) is 6 mol / L, the molar ratio of metallic lead to nitric acid is 1:3, and the dissolution temperature is 60°C.

5. The process according to claim 1, characterized in that The molecular weight cut-off of the nanofiltration membrane in step (2) is 200 Da, and the operating pressure is 1.5 MPa.

6. The process according to claim 1, characterized in that In step (3), the concentration of aqueous ammonia is 25%, the molar ratio of Pb(NO3)2 to aqueous ammonia is 1:1.2, the pH is adjusted to 10.5, the hydrothermal reaction temperature is 180°C, and the reaction time is 6 hours.

7. The process according to claim 1, characterized in that In step (4), the microwave frequency is 2.45 GHz, the heating rate is 10°C / min, the calcination temperature is 300°C, the calcination time is 2 hours, and the oxygen flow rate is 30-70 mL / min.

8. The process according to claim 1, characterized in that The exhaust gas condensation temperature in step (5) is -20-0°C, and the alkaline solution is 5-10wt% NaOH solution.

9. The process according to claim 1, characterized in that In step (5), the reverse osmosis membrane desalination rate is ≥98%, and the purity of ammonium nitrate recovered by electrodialysis is ≥99%.

10. The process according to claim 1, characterized in that The acid leaching of the electrolytic residue in step (5) adopts 4-6 mol / L hydrochloric acid, the extractant is Cyanex923, and the antimony recovery rate is ≥90%.

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