CN113088684A

CN113088684A - Method for preparing lead powder by wet recovery of waste lead paste with acid leaching circulation

Info

Publication number: CN113088684A
Application number: CN202110288990.3A
Authority: CN
Inventors: 杨家宽; 胡广; 张培源; 喻文昊; 李名扬; 李朝阳; 梁莎; 胡敬平; 侯慧杰; 袁书珊; 刘冰川
Original assignee: Huazhong University of Science and Technology
Current assignee: Huazhong University of Science and Technology
Priority date: 2021-03-18
Filing date: 2021-03-18
Publication date: 2021-07-09

Abstract

The invention belongs to the technical field of wet recovery of lead plaster of a waste lead storage battery, and particularly relates to a method for preparing lead powder by wet recovery of waste lead plaster with acid leaching circulation. The preparation method comprises the following steps: (1) putting the waste lead plaster into an alkaline solution for desulfurization to obtain desulfurized lead plaster, then leaching the desulfurized lead plaster by using a leaching agent, and filtering and separating to obtain a leaching solution and solid residues; (2) adding extraction acid into the leachate, carrying out precipitation reaction to obtain a solid-liquid mixture, standing to promote crystallization, and filtering and separating after the crystallization is finished to obtain a second organic acid lead crystal and a filtrate; (3) and roasting the second organic acid lead crystal to obtain lead powder. The invention uses the waste lead plaster as the raw material, constructs a wet leaching process, can realize the closed circulation of the acid radical ligand leached by the leaching agent, the recycling rate of the leached acid can reach 95 wt%, improves the economy of the wet process, the circulating leaching rate of lead can reach 97 wt%, and the impurity content of the lead powder product meets the requirement.

Description

Method for preparing lead powder by wet recovery of waste lead paste with acid leaching circulation

Technical Field

The invention belongs to the technical field of wet recovery of lead plaster of a waste lead storage battery, and particularly relates to a method for preparing lead powder by wet recovery of waste lead plaster with acid leaching circulation.

Background

More than 70 wt% of lead is used in the production of lead accumulators worldwide, and china, as the largest world producing and consuming lead accumulators, also produces an increasing amount of waste lead accumulators. Recycled lead recovered from lead-containing waste has become a major source of lead worldwide, and particularly in developed countries, the market share of recycled lead has greatly exceeded the proportion of virgin lead. The waste lead storage battery is a main source of secondary lead, and lead-containing waste materials generated after the waste lead storage battery is scrapped comprise a waste grid and waste lead plaster. Wherein the waste lead paste contains lead sulfate (73 wt%), lead dioxide (18 wt%), lead oxide (7 wt%), metallic lead (1 wt%) and trace impurity elements such as Fe, Ba and the like. The waste lead paste contains three lead-containing substances with different valence states and the lead sulfate has stable property, so that the recycling difficulty is high, and the waste lead storage battery recycling method is a main problem. The temperature required by the traditional pyrometallurgical lead smelting technology exceeds 1000 ℃, and SO is easily generated₂Compared with the problems of lead-containing smoke pollution and the like, the environmental impact of the waste lead paste wet recovery process is smaller.

The main inventor of the application continuously develops the wet recovery technology of the lead plaster of the waste lead storage battery, and discloses a method for preparing a lead compound by wet recovery and impurity removal of the waste lead plaster in a patent CN 108531736B. However, this technique focuses on the final product, does not address the disposal of the filtrate generated in the intermediate process, and if it is discharged directly, it will not only cause serious pollution, but also increase the cost of the drug. In patent CN109868366B, a method for preparing high-purity red lead by wet recovery of waste lead paste from filtrate recycling is proposed, which specifically comprises S1: leaching the waste lead plaster by using a mixed solution of a leaching acid salt, a leaching acid and a reducing agent, and filtering and separating to obtain a leaching solution; s2: adding a carbonate solution into the leachate, regulating and controlling the pH value of the reaction, and filtering and separating to obtain a lead carbonate precipitate and a filtrate; s3: roasting the lead carbonate in an aerobic atmosphere to prepare the red lead with high purity and low impurity content. According to the technical scheme, acetic acid-ammonium acetate is adopted to synergistically leach the waste lead plaster to obtain a leachate, the leachate is subjected to precipitation reaction to prepare high-purity lead carbonate, and barium acetate is added into the filtrate to precipitate sulfate ions to obtain a barium sulfate byproduct, so that the recycling of ammonium acetate filtrate is realized. However, the technical scheme has the defect that organic acid salt and organic acid as the leaching agent cannot be used in a closed cycle manner. Although the technical proposal proposes that barium salt is added into the filtrate obtained in the step S2 to remove impurities, and the filtrate is filtered to obtain a barium sulfate byproduct and a recycling solution, wherein the recycling solution is used for leaching waste lead paste in the next cycle, the treatment step is equivalent to converting expensive barium acetate into the barium sulfate byproduct, and a large amount of barium sulfate has a proper marketing problem.

Therefore, there is a need for further process routes based on the atomic economy principle of green chemistry, enabling closed circulation of the lixiviant.

Disclosure of Invention

Aiming at the improvement requirement of the prior art, the invention provides a method for preparing lead powder by wet recovery of waste lead paste with acid leaching circulation, which aims to add extraction acid into a leaching solution, obtain a solid-liquid mixture through precipitation reaction, stand to promote crystallization, and filter and separate after the crystallization is finished to obtain a second organic acid lead crystal and a filtrate. Because the solubility of the first organic acid lead obtained after the reaction of the leaching acid and the desulfurized lead plaster in water is greater than that of the second organic acid lead, a large amount of the leaching acid can be replaced while the second organic acid lead is generated, so that the leaching acid can be used in a closed cycle similar to a catalyst, and the technical problems of large waste of the leaching acid and the like are solved.

In order to achieve the above object, according to one aspect of the present invention, there is provided a method for preparing lead powder by wet recovery of waste lead paste from leaching acid cycle, comprising the steps of:

(1) putting the waste lead plaster into an alkaline solution for desulfurization to obtain desulfurized lead plaster, then leaching the desulfurized lead plaster by using a leaching agent, and filtering and separating to obtain a leaching solution and solid residues;

(2) adding extraction acid into the leachate, carrying out precipitation reaction to obtain a solid-liquid mixture, standing to promote crystallization, and filtering and separating after the crystallization is finished to obtain a second organic acid lead crystal and a filtrate;

(3) and roasting the second organic acid lead crystal to obtain lead powder.

The leaching agent comprises leaching acid and a reducing agent, and the solubility of the first organic acid lead obtained after the leaching acid reacts with the desulfurized lead plaster in water is greater than that of the second organic acid lead; the filtrate can be used as the leaching agent for leaching the desulfurized lead plaster of the next batch.

Preferably, when the filtrate is used as the leaching agent for leaching the desulfurized lead plaster of the next batch with the same mass, leaching acid and a reducing agent are required to be supplemented, and the molar ratio of the supplemented leaching acid to Pb element contained in the desulfurized lead plaster of the next batch is 1: 5-20; supplementary reducing agent and PbO contained in the next batch of desulfurized lead plaster₂In a molar ratio of 1-3: 1.

Preferably, the liquid-solid ratio of the volume of the filtrate after supplementing the leaching acid and the reducing agent to the mass of the desulfurized lead plaster of the next batch is 5-10 mL/g.

Preferably, the filtrate has a pH of 2 to 3 after replenishing the leaching acid and the reducing agent.

Preferably, the leaching acid is one of formic acid and acetic acid.

Preferably, the extracted acid is one of citric acid, oxalic acid, tartaric acid and maleic acid.

Preferably, the reducing agent is a mixture of one or more of hydrogen peroxide, glucose and acetaldehyde.

Preferably, the molar ratio of the extracted acid to the Pb element contained in the leachate is 1:1 to 1.5.

Preferably, the crystallization method is to seal the solid-liquid mixture and to stand for 6 to 48 hours at 40 to 80 ℃.

Preferably, the waste lead plaster is a lead-containing active substance separated from positive and negative plates of the waste lead storage battery after disassembly, crushing and sorting, and comprises lead sulfate, lead dioxide, lead oxide and metallic lead;

preferably, the alkali solution is a sodium hydroxide solution, and the sodium hydroxide and PbSO contained in the waste lead plaster₄The molar ratio of (A) to (B) is 2-2.2: 1;

preferably, the liquid-solid ratio of the volume of the sodium hydroxide solution to the mass of the waste lead plaster is 2-10 mL/g;

preferably, the molar ratio of the leaching acid to Pb element contained in the desulfurized lead paste is 2-2.5: 1;

preferably, the reducing agent and PbO contained in the desulfurized lead paste₂In a molar ratio of 1-3: 1;

preferably, the liquid-solid ratio of the volume of the leaching agent to the mass of the desulfurized lead paste is 5-10 mL/g;

preferably, the pH of the leachate is between 4 and 5.5;

preferably, the roasting is at 350-450 ℃ for 10-300 min.

According to another aspect of the invention, the lead powder prepared by wet recovery of waste lead paste of a leaching acid cycle is prepared according to the preparation method of any one of the preceding claims.

The invention has the following beneficial effects:

(1) aiming at the defects or improvement requirements of the prior art, the invention uses the waste lead storage battery lead plaster as a raw material to construct a wet leaching process. Adding extraction acid into the leachate, carrying out precipitation reaction to obtain a solid-liquid mixture, standing to promote crystallization, and filtering and separating after the crystallization is finished to obtain a second organic acid lead crystal and a filtrate. Because the solubility of the first organic acid lead obtained after the reaction of the leaching acid and the desulfurized lead plaster in water is greater than that of the second organic acid lead, a large amount of the leaching acid can be replaced while the second organic acid lead is generated, so that the leaching acid can be circularly used in a closed manner similar to a catalyst, the use efficiency of the leaching acid is obviously improved, the atomic economic principle of green chemistry is realized, the technical problems of great waste of the leaching acid and the like are solved, and the economy of a wet process is improved.

(2) According to the invention, the solid-liquid mixture is preferably obtained, sealed and kept stand for 6-48h at 40-80 ℃. Through the standing heat preservation treatment, the size of the second organic acid lead crystal is increased, the crystal morphology is more regular, the filtering performance of the second organic acid lead is improved, the difficulty of separation and purification of leached acid is reduced, and the stable operation of the subsequent leached acid filtrate circulation process is facilitated.

(3) According to the occurrence form of the metal elements and the strength difference between the metal elements and the extracted acid radical ligand, the method realizes the high-efficiency recovery of lead and the directional separation of impurity elements. The crystallization is an assembly process of regular arrangement of like molecules or ions, which is beneficial for impurity elements to enter a liquid phase, thereby further removing the impurity elements. Because the impurity content in the leachate is very low, the impurity ion concentration in the filtrate is also maintained at a lower level, and the enrichment of impurity elements in the leachate in the circulation process is avoided, so that a high-purity second organic acid lead crystal is obtained, the impurity content of a lead powder product obtained by subsequent roasting is ensured to meet the requirement, the impurity Fe content in the lead powder is lower than 10mg/kg, the impurity Ba content is lower than 8mg/kg, the impurity Cu content is lower than 2mg/kg, and the impurity Zn and Al contents are lower than 1 mg/kg.

(4) In the process of obtaining the solid-liquid mixture, the molar ratio of the extraction acid to Pb element contained in the leachate is regulated to be 1:1-1.5, so that the problem that when the filtrate is recycled, the extraction acid radical contained in the filtrate reacts with lead in the desulfurized lead paste to generate precipitate to be discharged as residue, the leaching rate of the lead in the recycling process is reduced, and the leaching rate of the lead in the recycling process can reach more than 97 wt%.

(5) According to the invention, the filtrate containing the leached acid is regenerated in the process of preparing the second lead organo-acid crystal by using the first lead organo-acid leaching solution, and the filtrate can be used as a leaching agent again in the leaching process after a small amount of leaching acid and a reducing agent are supplemented. When the amount of the supplementary leaching acid is too small, the content of the leaching acid in the filtrate is not enough to fully leach the desulfurized lead plaster with the same mass, so that the leaching rate of lead is reduced; when the amount of supplementary leaching acid is excessive, the pH value of the filtrate is sharply reduced, so that a large amount of impurity elements are promoted to be dissolved out, and the impurity removal of the product is not facilitated. Therefore, when the filtrate of the present invention is used as the leaching agent to leach the desulfurized lead plaster of the same quality of the next batch, the molar ratio of the supplemented leaching acid to the Pb element contained in the desulfurized lead plaster of the next batch is preferably 1: 5-20. In addition, an acid extracting solid reagent is preferably added in the process of preparing the second organic acid lead, so that the volume of the filtrate is not enlarged, the concentration of the leached acid in the filtrate is reduced, and the leaching rate of the lead in the circulation process is reduced.

Drawings

FIG. 1 is a process flow diagram of the present invention.

Figure 2 is an XRD pattern of lead citrate obtained at different crystallization times at 60 ℃.

FIG. 3 is an SEM image of lead citrate obtained by crystallization at 30 ℃ for 24 h.

FIG. 4 is an SEM image of lead citrate obtained by crystallization at 60 ℃ for 24 h.

FIG. 5 is a diagram showing morphology distribution ratios of impurity elements Fe, Ba, Cu, Zn and Al under different pH conditions, wherein (a) in FIG. 5, (b) in FIG. 5, (c) in FIG. 5, (d) in FIG. 5 and (e) in FIG. 5 are impurity elements Fe, Ba, Cu, Zn and Al at Pb, respectively²⁺-CH₃COO^--Cit^3-In the system, a figure of morphological distribution ratio under different pH conditions.

FIG. 6 shows a lemonThe molar ratio of citric acid to Pb element is different, and when the molar ratio of citric acid to Pb element is 1:1 and 1.05:1, Pb is in CH₃COO^--Cit^3-In the system, a figure of morphological distribution ratio under different pH conditions.

Fig. 7 is an XRD spectrum of the lead powder prepared in example 1.

Figure 8 is an XRD pattern of different recycle batches of lead citrate prepared in example 4.

Figure 9 is a graph of the particle size distribution of lead citrate from different recycle batches prepared in example 4.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

The waste lead plaster is lead-containing active substances separated from positive and negative plates after the waste lead-acid storage battery is disassembled, crushed and sorted, and the lead-containing active substances comprise lead sulfate, lead dioxide, lead oxide, metallic lead and trace impurity elements such as Fe, Ba, Cu, Zn, Al and the like. In order to reduce sulfur pollution and facilitate subsequent reaction, the waste lead paste needs to be desulfurized, and the specific operation method comprises the following steps:

placing the waste lead plaster in the alkali solution to be stirred for reaction, and stirring the PbSO in the waste lead plaster at normal temperature₄Conversion to Pb₃O₂(OH)₂. Preferably, the alkali solution is a sodium hydroxide solution, and the sodium hydroxide and PbSO contained in the waste lead plaster₄The molar ratio of the sodium hydroxide solution to the waste lead plaster is 2-2.2:1, the liquid-solid ratio of the volume of the sodium hydroxide solution to the mass of the waste lead plaster is 2-10mL/g, and the desulfurized lead plaster is obtained by filtering and separating after complete desulfurization. The main reactions that occur in this process are as follows:

3PbSO₄+6NaOH→Pb₃O₂(OH)₂+3Na₂SO₄+2H₂O

the phase composition of the desulfurized lead plaster mainly comprises PbO and Pb₃O₂(OH)₂And PbO₂Also contains residual PbSO₄And trace impurity elements such as Fe, Ba, Cu, Zn, Al and the like. Wherein PbO and Pb₃O₂(OH)₂Can react with the leaching acid directly at normal temperature, and PbO₂The first organic acid lead can be generated by the reaction between the first organic acid lead and the leaching acid under the condition of adding a reducing agent. A small amount of PbSO remained in the desulfurized lead plaster₄Stable in nature and difficult to directly react with leaching acid at normal temperature, and thus will remain in the residue. Taking acetic acid as leaching acid and hydrogen peroxide as a reducing agent as an example, the main reactions in the process are as follows:

PbO+2CH₃COOH→Pb(CH₃COO)₂+H₂O

Pb₃O₂(OH)₂+6CH₃COOH→3Pb(CH₃COO)₂+4H₂O

PbO₂+2CH₃COOH+H₂O₂→Pb(CH₃COO)₂+2H₂O+O₂。

and after leaching is finished, adding extraction acid into the leaching solution, carrying out precipitation reaction on lead ions in the solution and the extraction acid radical ions to generate a second organic acid lead, and simultaneously regenerating the leaching acid. And after filtering and separating, preparing lead powder by roasting the second organic acid lead, and reusing the filtrate in the leaching process of the desulfurized lead plaster. Taking citric acid as an example of the extracted acid, the lead citrate generated in the process is a general name of a series of complexes of citrate and lead ions, wherein Pb is common₃(C₆H₅O₇)₂·3H₂O and Pb (C)₆H₆O₇)·H₂And O. The chemical reaction equation for the preparation of two lead citrates by the reaction of lead acetate and citric acid described above is as follows:

3Pb(CH₃COO)₂+2C₆H₈O₇+3H₂O→Pb₃(C₆H₅O₇)₂·3H₂O+6CH₃COOH

Pb(CH₃COO)₂+C₆H₈O₇+H₂O→Pb(C₆H₆O₇)·H₂O+2CH₃COOH

the reaction is a process of generating a lead citrate target product by a liquid-phase homogeneous reaction, and the particle size of the lead citrate is influenced by a plurality of factors in the preparation process, such as raw material proportion, stirring speed, temperature, time and the like. Therefore, the lead citrate needs to be subjected to a stage of strengthening crystallization, specifically, a solid-liquid mixture obtained by reaction is sealed and kept stand at 40-80 ℃ for 6-48h to promote the lead citrate to grow into crystal particles with larger particle size, so that the subsequent filtering operation is convenient to carry out. XRD characterization was performed on samples taken at different crystallization times during the crystallization of lead citrate, and the results are shown in FIG. 2. As can be seen from fig. 2, the XRD pattern (0h) of the lead citrate suspension obtained after the stirring reaction has broad diffraction peaks and no distinct peak pattern, which indicates that the lead citrate obtained at this time contains a large amount of amorphous substances. When the crystallization time is longer than 6h, the product has sharp peak shape, and the peak position is kept unchanged along with the increase of the crystallization time, which indicates that the crystal appearance is regular at the moment, and the analysis considers that the crystal size is increased along with the increase of the heat preservation time. Fig. 3 and 4 show SEM images of lead citrate obtained at different crystallization temperatures, respectively. It can be seen that the lead citrate crystal has a small grain size of below 20 μm at a low temperature, and is difficult to filter; when the temperature rises, the grain diameter of the obtained product can reach 100 mu m, and the lead citrate product is very easy to precipitate, which shows that the rising of the temperature has a promoting effect on the growth of lead citrate crystals, not only improves the filtration performance of the lead citrate, but also reduces the difficulty of the separation and purification of the leached acid, and is beneficial to the stable operation of the subsequent leached acid filtrate circulation process.

Meanwhile, the pH value of the crystal system is regulated and controlled by utilizing the difference of the solubility product constants of the citrate and different metal ions, so that impurity elements are blocked from entering a target product, and further separation of lead and the impurity elements is realized. In FIG. 5, (a), (b), (c), (d) and (e) areIn which the elements Fe, Ba, Cu, Zn and Al are respectively in Pb²⁺-CH₃COO^--Cit^3-In the system, a figure of morphological distribution ratio under different pH conditions. It can be seen that Fe is in the form of Fe under high pH conditions₂O₃The solid phase exists, and Fe is gradually converted into Fe (cit) OH with the reduction of pH^-The plasma state exists in the liquid phase, and when the pH of the system is about 2.6, most of Fe is retained in the lead citrate in the solid phase form of Fe (Hcit). At pH<When 2, the element Ba is mainly Ba²⁺And Ba (H)₂cit)⁺The plasma state exists in the liquid phase when the pH is high>At 2, part of the Ba begins to convert to a solid form of Ba (Hcit) which is coprecipitated with lead citrate, the pH is further raised>When 5, Ba is mainly Ba (cit)^-Is present in the liquid phase. At 0<pH<7, Cu is always present in the liquid phase in the form of ions. At a pH around 3.1, the Zn and Al fractions remain in the lead citrate product in a solid phase of Zn (Hcit) and Al (cit). Because the content of each impurity in the leaching solution is very low, and the precipitation and crystallization processes also have a certain impurity removal effect, the impurity content of the lead powder obtained by subsequent roasting is further ensured to meet the requirement. Meanwhile, the concentration of impurity ions in the filtrate can be maintained at a lower level, so that the enrichment of impurity elements in the leachate in the next cycle process is avoided.

More importantly, the addition parameters of the extraction acid also influence the properties of the filtrate generated in the process, and the relationship is that the filtrate can be efficiently and stably reused for leaching the desulfurized lead plaster. The applicant finds that the precipitation reaction of lead ions and citric acid in the liquid phase is very sensitive, the improvement of the proportion of the extracted acid to the lead ions can lead to more extracted acid radicals remaining in the filtrate, and when about 5% of the extracted acid radicals are mixed in the recycled liquid, the leaching rate of lead can be reduced to below 90 wt%. In FIG. 6, (a) and (b) represent the molar ratios of citric acid to Pb element of 1:1 and 1.05:1, respectively, where Pb is in CH₃COO^--Cit^3-In the system, a figure of morphological distribution ratio under different pH conditions. As can be seen from fig. 6 (a), when the molar ratio of citric acid to Pb element is 1:1, the citric acid and lead ions are just completely reacted, and the filtrate contains only regenerated acetic acid. In FIG. 6 (b), with citric acidThe molar ratio of the citric acid to Pb element is increased to 1.05:1, even if 5 percent of citrate remained in the filtrate can be combined with lead ions to form insoluble Pb (Hcit), namely Pb (C)₆H₆O₇)·H₂And O. When the filtrate is reused for leaching desulfurized pastel, pb (hcit) enters the residue, so that the leaching rate of lead is reduced. Therefore, the adding amount of the extracted acid is maintained at the theoretical adding amount level, and the situation that the lead leaching rate is reduced in the filtrate circulating process due to the fact that the precipitate generated by the acid radical extracted in the recycling process and the lead in the desulfurized lead plaster is removed as filter residue is avoided while the lead is completely recovered. Specifically, by regulating and controlling the molar ratio of the extracted acid to Pb element contained in the leachate to be 1:1-1.5, the invention obtains the filtrate with simple components, wherein the filtrate basically only contains regenerated leached acid, the regeneration proportion can reach 95 wt%, the residue of extracted acid radicals can not be generated, and the filtrate can be directly recycled after a small amount of leached acid and reducing agent are supplemented. The process can stably run, a precursor with complete crystal form, consistent appearance and particle size within the range of 40-200 mu m can be produced in each cycle, the impurity content is low, and then a lead powder product with the impurity Fe content lower than 10mg/kg, the impurity Ba content lower than 8mg/kg, the impurity Cu content lower than 2mg/kg and the impurity Zn and Al content lower than 1mg/kg is prepared.

The following are specific embodiments.

Example 1

(1) Determination of PbSO in waste lead paste₄The content of (B) was 72.5 wt%, and the content of Pb element was 73.1 wt%. According to sodium hydroxide and PbSO₄The molar ratio is 2.05:1, the liquid-solid ratio of the volume of the sodium hydroxide solution to the mass of the waste lead plaster is 2mL/g, 100g of the waste lead plaster is placed in 200mL of aqueous solution containing 19.6g of sodium hydroxide, the mixture is stirred and reacted for 1h at normal temperature, and the mixture is filtered and separated to obtain 82.6g of desulfurized lead plaster. The content of Pb element in the desulfurized lead paste is measured to be 88.1 wt%, and PbO is measured₂The content of (B) was 21.9 wt%. Hydrogen peroxide and PbO contained in the desulfurized lead plaster according to the molar ratio of acetic acid to Pb element contained in the desulfurized lead plaster being 2.1:1₂According to the molar ratio of 3:1, the liquid-solid ratio of the volume of the leaching agent to the mass of the desulfurized lead plaster is 7mL/g, 82.6g of the obtained desulfurized lead plaster is placed in a solution containing 44.2g of acetic acid and 7.7g of hydrogen peroxide578.2mL of aqueous solution, stirring and reacting for 1h at normal temperature, filtering and separating to obtain lead acetate leaching solution and residue. The Pb concentration in the leachate was measured to be 0.57mol/L, the volume was 600mL, the pH was measured to be 5.1, and the lead leaching rate was 97.5 wt%.

(2) Adding 71.8g of citric acid solid reagent into the prepared lead acetate leachate according to the parameter that the molar ratio of citric acid to Pb element contained in the leachate is 1:1, stirring and reacting for 2 hours at normal temperature, sealing a reaction product, standing for 24 hours at 60 ℃, and filtering and separating to obtain lead citrate crystals and filtrate. The average particle size of lead citrate was determined to be 107 μm, the concentration of acetic acid in the filtrate was 1.23mol/L, the volume was 571mL, the pH was 2.6, and the regeneration rate of acetic acid was 95.3 wt%.

(3) And roasting the obtained lead citrate crystal at 400 ℃ for 120min to obtain a lead powder sample 1. The contents of Fe, Ba, Cu, Zn and Al elements in the lead powder sample 1 are respectively 9.88mg/kg, 7.46mg/kg, 1.89mg/kg, 0.64mg/kg and 0.59mg/kg, and the total lead recovery rate is 95.1 wt%.

Fig. 7 is an XRD spectrum of the lead powder prepared in example 1.

As can be seen from fig. 7, the lead powder has a main crystal form of β -PbO, and also contains a small amount of α -PbO and metal Pb, and the lead powder of a mixture of PbO and metal Pb particles can be used as an active material for manufacturing a plate of a lead storage battery.

Example 2

The difference between the embodiment and the embodiment 1 is that the other acetic acid adding coefficient, the leaching solution solid ratio, the citric acid adding coefficient, the crystallization temperature, the roasting temperature and the roasting time in the claim range are selected.

(1) Determination of PbSO in waste lead paste₄The content of (B) was 72.5 wt%, and the content of Pb element was 73.1 wt%. According to sodium hydroxide and PbSO₄The molar ratio is 2.05:1, the liquid-solid ratio of the volume of the sodium hydroxide solution to the mass of the waste lead plaster is 2mL/g, 100g of the waste lead plaster is placed in 200mL of aqueous solution containing 19.6g of sodium hydroxide, the mixture is stirred and reacted for 1h at normal temperature, and the mixture is filtered and separated to obtain 82.6g of desulfurized lead plaster. The content of Pb element in the desulfurized lead paste is measured to be 88.1 wt%, and PbO is measured₂The content of (B) was 21.9 wt%. According to the molar ratio of acetic acid to Pb element contained in the desulfurized lead plaster of 23:1, PbO contained in Hydrogen peroxide and desulfurized lead paste₂The molar ratio of the leaching agent to the desulfurized lead paste is 3:1, and the liquid-solid ratio of the volume of the leaching agent to the mass of the desulfurized lead paste is 5mL/g, 82.6g of the obtained desulfurized lead paste is placed in 413mL of aqueous solution containing 48.4g of acetic acid and 7.7g of hydrogen peroxide, stirred and reacted for 1h at normal temperature, and filtered and separated to obtain lead acetate leaching solution and residue. The Pb concentration in the leaching solution was measured to be 0.79mol/L, the volume was 433mL, the pH was measured to be 4.8, and the lead leaching rate was 97.4 wt%.

(2) Adding 47.7g of citric acid solid reagent into the prepared lead acetate leachate according to the parameter that the molar ratio of citric acid to Pb element contained in the leachate is 1:1.5, stirring at normal temperature for reaction for 2 hours, sealing a reaction product, standing at 80 ℃ for 24 hours, and filtering and separating to obtain lead citrate crystals and filtrate. The average particle size of lead citrate was determined to be 158 μm, the acetic acid concentration in the filtrate was 1.87mol/L, the volume was 410mL, the pH was 2.4, and the acetic acid regeneration rate was 95.0 wt%.

(3) And roasting the obtained lead citrate crystal at 350 ℃ for 300min to obtain a lead powder sample 2. The contents of Fe, Ba, Cu, Zn and Al elements in the lead powder sample 2 are respectively 9.23mg/kg, 7.01mg/kg, 1.11mg/kg, 0.48mg/kg and 0.33mg/kg, and the total lead recovery rate is 95.2 wt%.

Example 3

This example differs from example 1 in that other types of leaching acids, reducing agents, extraction acids were selected within the scope of the claims.

(1) Determination of PbSO in waste lead paste₄The content of (B) was 72.5 wt%, and the content of Pb element was 73.1 wt%. According to sodium hydroxide and PbSO₄The molar ratio is 2.05:1, the liquid-solid ratio of the volume of the sodium hydroxide solution to the mass of the waste lead plaster is 2mL/g, 100g of the waste lead plaster is placed in 200mL of aqueous solution containing 19.6g of sodium hydroxide, the mixture is stirred and reacted for 1h at normal temperature, and the mixture is filtered and separated to obtain 82.6g of desulfurized lead plaster. The content of Pb element in the desulfurized lead paste is measured to be 88.1 wt%, and PbO is measured₂The content of (B) was 21.9 wt%. According to the mol ratio of formic acid to Pb element contained in the desulfurized lead plaster of 2.1:1, acetaldehyde and PbO contained in the desulfurized lead plaster₂The molar ratio of the leaching agent to the mass of the desulfurized lead plaster is 3:1, and the liquid-solid ratio of the volume of the leaching agent to the mass of the desulfurized lead plaster is 7mL/gAnd putting 82.6g of desulfurized lead paste into 578.2mL of aqueous solution containing 33.9g of formic acid and 10.0g of acetaldehyde, stirring and reacting for 1h at normal temperature, and filtering and separating to obtain a lead formate leaching solution and residues. The Pb concentration in the leachate was measured to be 0.58mol/L, the volume was 590mL, the pH was measured to be 4.9, and the lead leaching rate was 97.4 wt%.

(2) Adding 30.6g of oxalic acid solid reagent into the prepared lead formate leachate according to the parameter that the molar ratio of oxalic acid to Pb element contained in the leachate is 1:1, stirring and reacting for 2 hours at normal temperature, sealing a reaction product, standing for 24 hours at 60 ℃, and filtering and separating to obtain lead oxalate crystals and filtrate. The average particle size of lead oxalate was determined to be 58 μm, the formic acid concentration in the filtrate was 1.24mol/L, the volume was 566mL, the pH was 2.3, and the formic acid regeneration rate was 95.2 wt%.

(3) And roasting the obtained lead oxalate crystal at 400 ℃ for 120min to obtain a lead powder sample 3. The contents of Fe, Ba, Cu, Zn and Al elements in the lead powder sample 3 are respectively 9.64mg/kg, 7.32mg/kg, 1.39mg/kg, 0.79mg/kg and 0.67mg/kg, and the total lead recovery rate is 95.1 wt%.

Example 4

This example differs from example 1 in that the filtrate is used as a leaching agent for leaching the desulfurized pastel of the next batch.

(1) Determination of PbSO in waste lead paste₄The content of (B) was 72.5 wt%, and the content of Pb element was 73.1 wt%. According to sodium hydroxide and PbSO₄The molar ratio is 2.05:1, the liquid-solid ratio of the volume of the sodium hydroxide solution to the mass of the waste lead plaster is 2mL/g, 100g of the waste lead plaster is placed in 200mL of aqueous solution containing 19.6g of sodium hydroxide, the mixture is stirred and reacted for 1h at normal temperature, and the mixture is filtered and separated to obtain 82.6g of desulfurized lead plaster. The content of Pb element in the desulfurized lead paste is measured to be 88.1 wt%, and PbO is measured₂The content of (B) was 21.9 wt%. Hydrogen peroxide and PbO contained in the desulfurized lead plaster according to the molar ratio of acetic acid to Pb element contained in the desulfurized lead plaster being 2.1:1₂The molar ratio of the leaching agent to the desulfurized lead paste is 3:1, and the liquid-solid ratio of the volume of the leaching agent to the mass of the desulfurized lead paste is 7mL/g, 82.6g of the obtained desulfurized lead paste is placed in 578.2mL of aqueous solution containing 44.2g of acetic acid and 7.7g of hydrogen peroxide, stirred and reacted for 1h at normal temperature, and filtered and separated to obtain lead acetate leaching solution and residue. Measuring Pb concentration in leaching solutionThe degree is 0.57mol/L, the volume is 600mL, the pH is 5.1, and the lead leaching rate is 97.5 wt%.

(3) And roasting the obtained lead citrate crystal at 400 ℃ for 120min to obtain a lead powder sample 4. The contents of Fe, Ba, Cu, Zn and Al elements in the lead powder sample 4 are respectively 9.32mg/kg, 7.02mg/kg, 1.07mg/kg, 0.76mg/kg and 0.95mg/kg, and the total lead recovery rate is 95.1 wt%.

(4) Hydrogen peroxide and PbO contained in the desulfurized lead plaster according to the molar ratio of acetic acid to Pb element contained in the desulfurized lead plaster being 1:10₂Is 3:1, and the filtrate is supplemented with acetic acid and hydrogen peroxide for the next leaching run. The glacial acetic acid supplement amount is 2.1g, the hydrogen peroxide supplement amount with the mass concentration of 30 wt% is 25.7g, the liquid-solid ratio is controlled to be 7mL/g when the leaching is recycled, and the reaction time is 1 h.

(5) Repeating the above operation steps until 5 times of circulation, roasting the lead citrate crystals prepared in each round at 400 ℃ for 120min, and maintaining the total lead recovery rate to be more than 95 wt%. The impurity element content of the lead powder samples obtained in different circulation batches is shown in table 1, and the acetic acid regeneration rate and the lead leaching rate in the circulation process are shown in table 2.

TABLE 1 impurity element content (unit: mg/kg) of lead powder samples of different cycles in example 4

Circulating batches	Fe	Ba	Cu	Zn	Al
						First batch	9.21	7.21	1.87	0.32	0.24
Second batch	8.36	7.33	1.63	0.34	0.19
						Third batch	8.21	7.01	1.57	0.41	0.32
Fourth batch	9.45	6.96	1.48	0.38	0.26
						Fifth batch	8.55	5.87	1.49	0.42	0.20

As can be seen from Table 1, the impurity content in each batch of lead powder samples is stable, wherein the impurity Fe content is lower than 10mg/kg, the impurity Ba content is lower than 8mg/kg, the impurity Cu content is lower than 2mg/kg, and the impurity Zn and Al content is lower than 1mg/kg, so that the production standard of new batteries can be met.

TABLE 2 regeneration rate of acetic acid, lead leaching rate (unit: wt%) during the recycling in example 4

Circulating batches	Acetic acid regeneration rate	Lead leaching rate
			First batch	95.1	97.3
Second batch	95.3	97.4
			Third batch	95.2	97.1
Fourth batch	95.6	97.7
			Fifth batch	95.4	97.0

As can be seen from Table 2, the regeneration rate of acetic acid in the filtrate did not reach 100 wt%, so a certain amount of acetic acid was required to be supplemented for leaching the next batch of desulfurized pastel of the same quality. The regeneration rate of acetic acid is stabilized to be more than 95 wt% in the circulation process, and the leaching rate of lead is stabilized to be more than 97 wt%, which shows that the wet leaching process constructed by the invention can efficiently and stably operate while realizing circulation of acid radical ligands leached by a leaching agent.

Figure 8 is the XRD pattern of lead citrate from different recycle batches prepared in example 4.

As can be seen from fig. 8, the crystal forms of the lead citrate produced in each cycle of the method for preparing lead powder by wet recovery of waste lead paste in leaching acid cycle provided by the invention can be kept consistent.

As can be seen from FIG. 9, the average particle size of the lead citrate in each cycle was close to 100. mu.m.

In conclusion, the method for preparing lead powder by wet recovery of waste lead paste in acid leaching circulation, provided by the invention, has the advantages that the crystal form and the particle size of the produced lead citrate in each circulation process are consistent, and the stable operation can be realized.

Comparative examples

Comparative example 1

This example differs from example 4 in that the amount of leaching acid supplementation is selected outside the scope of the claims, and specifically comprises the following steps:

the steps (1) and (2) are the same as the steps (1) and (2) in example 4.

(3) And roasting the obtained lead citrate crystal at 400 ℃ for 120min to obtain a lead powder sample 5. The contents of Fe, Ba, Cu, Zn and Al elements in the lead powder sample 5 are respectively 9.28mg/kg, 7.17mg/kg, 1.53mg/kg, 0.44mg/kg and 0.18mg/kg, and the total lead recovery rate is 95.1 wt%.

(4) Hydrogen peroxide and PbO contained in the desulfurized lead plaster according to the molar ratio of acetic acid to Pb element contained in the desulfurized lead plaster being 1:1₂Is 3:1, and the filtrate is supplemented with acetic acid and hydrogen peroxide for the next leaching run. The glacial acetic acid supplement amount is 21.0g, the hydrogen peroxide supplement amount with the mass concentration of 30 wt% is 25.7g, the liquid-solid ratio is controlled to be 7mL/g when the leaching is recycled, and the reaction time is 1 h.

(5) Repeating the above operation steps until 5 times of circulation, roasting the lead citrate crystals prepared in each round at 400 ℃ for 120min, and maintaining the total lead recovery rate to be more than 95 wt%. The impurity element content of the lead powder samples obtained in different circulation batches is shown in table 3.

TABLE 3 impurity element content (unit: mg/kg) of lead powder samples of different cycles in comparative example 1

Circulating batches	Fe	Ba	Cu	Zn	Al
						First batch	55.69	24.96	5.36	3.18	4.32
Second batch	64.79	37.12	7.12	4.95	5.02
						Third batch	71.54	42.78	9.89	5.37	5.89
Fourth batch	76.33	45.33	10.33	6.18	6.03
						Fifth batch	80.02	47.69	11.21	6.29	6.22

The results in table 3 show that increasing the acetic acid supplementation coefficient increases the acetic acid concentration in the filtrate, and the pH of the leaching system decreases rapidly, so that the impurity content in the leachate increases, and the impurity elements in the lead powder product seriously exceed the standard and do not meet the requirements for preparing the active material of the battery plate. Meanwhile, the acetic acid adding amount exceeds the actual requirement, and each circulation can cause the concentration of the acetic acid in the filtrate to continuously rise, so that the impurity content of the lead powder product gradually rises. Therefore, the invention emphasizes that when the filtrate is used as the leaching agent for leaching the desulfurized lead plaster of the same quality of the next batch, the leaching acid and the reducing agent are required to be supplemented, the molar ratio of the supplemented leaching acid to Pb element contained in the desulfurized lead plaster of the next batch is 1:5-20, the product impurity enrichment is avoided, and the stability of the circulation process is maintained.

Comparative example 2

The difference between the embodiment and the embodiment 4 is that the adding amount of the extracted acid which exceeds the scope of the claims is selected, and the method specifically comprises the following steps:

step (1) is the same as step (1) in example 4.

(2) According to the parameter that the molar ratio of citric acid to Pb element contained in the leaching solution is 1:0.9, 79.7g of citric acid solid reagent is added into the prepared lead acetate leaching solution, the mixture is stirred and reacts for 2 hours at normal temperature, the reaction product is sealed and stands for 24 hours at 60 ℃, and lead citrate crystals and filtrate are obtained through filtration and separation. The average grain diameter of the lead citrate is determined to be 124 mu m, the concentration of acetic acid in the filtrate is 1.23mol/L, the volume is 571mL, and the regeneration rate of the acetic acid is 95.3 wt%.

(3) And roasting the obtained lead citrate crystal at 400 ℃ for 120min to obtain a lead powder sample 6. The contents of Fe, Ba, Cu, Zn and Al elements in the lead powder sample 6 are respectively 9.11mg/kg, 7.89mg/kg, 1.63mg/kg, 0.44mg/kg and 0.17mg/kg, and the total lead recovery rate is 95.1 wt%.

(5) Repeating the above operation steps until 5 times of circulation, roasting the lead citrate crystals prepared in each round at 400 ℃ for 120min, and maintaining the total lead recovery rate to be more than 95 wt%. The lead leaching rate during the cycle is shown in table 4.

TABLE 4 lead Leaching Rate in wt% for different recycle batches in comparative example 2

Circulating batches	Lead leaching rate
		First batch	88.1
Second batch	88.6
		Third batch	88.3
Fourth batch	88.2
		Fifth batch	88.4

As can be seen from table 4, when the ratio of citrate to lead ions is increased, the citrate will precipitate with lead in the desulfurized lead plaster during recycling and be removed as filter residue, resulting in a decrease in the lead leaching rate during the subsequent cycle, because more citrate remains in the filtrate. Through parameter optimization, the dosage of the extraction acid is maintained at a low level by the method, so that the filtrate with simple components is obtained, only regenerated leaching acid is basically contained, residue of extraction acid radicals is avoided, and the extraction acid and the reducing agent can be directly recycled after a small amount of leaching acid and the reducing agent are supplemented.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims

1. A method for preparing lead powder by recovering waste lead paste with leached acid circulation by a wet method is characterized by comprising the following steps:

(3) roasting the second organic acid lead crystal to obtain lead powder;

wherein the leaching agent comprises leaching acid and a reducing agent, and the solubility of the first organic acid lead obtained after the leaching acid reacts with the desulfurized lead plaster in water is greater than that of the second organic acid lead; the filtrate can be used as the leaching agent for leaching the desulfurized lead plaster of the next batch.

2. The method for preparing the lead powder as claimed in claim 1, wherein when the filtrate is used as the leaching agent for leaching the same mass of desulfurized lead plaster of the next batch, a leaching acid and a reducing agent are supplemented, and the molar ratio of the supplemented leaching acid to Pb element contained in the desulfurized lead plaster of the next batch is 1: 5-20; supplementary reducing agent and PbO contained in the next batch of desulfurized lead plaster₂In a molar ratio of 1-3: 1.

3. The method for preparing lead powder as claimed in claim 2, wherein the liquid-solid ratio of the volume of the filtrate after supplementing the leaching acid and the reducing agent to the mass of the desulfurized lead plaster of the next batch is 5-10 mL/g.

4. The method for preparing lead powder as recited in claim 2 or 3, wherein the filtrate has a pH of 2 to 3 after supplementing the leaching acid and the reducing agent.

5. The method for preparing lead powder as recited in claim 2, wherein the leaching acid is one of formic acid and acetic acid.

6. The method for preparing lead powder as claimed in claim 2 or 5, wherein the extracted acid is one of citric acid, oxalic acid, tartaric acid and maleic acid.

7. The method for preparing lead powder according to claim 2 or 5, wherein the reducing agent is a mixture of one or more of hydrogen peroxide, glucose and acetaldehyde.

8. The method for preparing lead powder as recited in claim 1, wherein the molar ratio of the extracted acid to the Pb element contained in the leachate is 1:1 to 1.5.

9. The method for preparing lead powder according to claim 1 or 2, wherein the crystallization method is to seal the solid-liquid mixture and to stand at 40-80 ℃ for 6-48 h;

preferably, the pH of the leachate is between 4 and 5.5;

preferably, the roasting is at 350-450 ℃ for 10-300 min.

10. Lead powder prepared by wet recovery of waste lead paste from leaching acid circulation, which is characterized by being prepared according to the preparation method of any one of claims 1 to 9.