Method for recycling lead oxide-containing waste material

Abstract

Provided is a method for recycling a lead oxide-containing waste material, comprising: (1) contacting the lead oxide-containing waste material with a desulphurizer under desulphurization reaction conditions, and performing a solid-liquid separation on the mixture after contacting to obtain a filtrate and a filtration residue; (2) performing a conversion reaction on the above-mentioned filtration residue at a temperature of 350-750° C. so as to convert the lead-containing components in the filtration residue into lead oxide; (3) contacting the product obtained from step (2) with an alkaline solution so as to dissolve the PbO therein, and then performing a solid-liquid separation to obtain a PbO-alkaline solution; and (4) crystallizing the PbO-alkaline solution from step (3) to obtain PbO crystals and an alkaline filtrate. The method can reduce the energy consumption.

Claims

1. A method for recovering lead oxide from lead oxide-containing wastes, comprising the following steps: (1) controlling a lead oxide-containing waste to contact with a desulfurizing agent to desulfurize through wet ball milling, and carrying out solid-liquid separation for a mixture obtained from the contact, to obtain filtrate and filter residue; (2) controlling the filter residue to have a conversion reaction at 350-750° C. temperature, to convert lead-containing components in the filter residue into PbO; (3) controlling a product obtained in step (2) to contact with alkaline solution A, to dissolve the PbO in the product, and then carrying out solid-liquid separation to obtain PbO-alkaline solution; (4) controlling the PbO-alkaline solution obtained in step (3) to crystallize, to obtain PbO crystals and alkaline filtrate; wherein the contact in step (3) is carried out in presence of a dissolution promoter, which is selected from the group consisting of ethylene diamine, sodium acetate, sodium tartrate, EDTA, glycerol, butanediol, pentanol, sorbitol, xylitol, histidine, arginine, and glycocoll; and the dosage of the dissolution promoter is 0.2-20 wt % of the alkaline solution A.

2. The method according to claim 1, wherein the conversion reaction in step (2) is carried out in the presence of a promoter, which is added in step (1) and/or step (2).

3. The method according to claim 2, wherein the promoter is selected from the group consisting of lead powder, barium powder, aluminum powder, sodium powder, lithium powder, potassium powder, magnesium powder, naphthalene, camphor, urea, nickel powder, tin powder, stibium powder, zinc powder, carbon powder, active carbon containing 0.5-95 wt % PbO, and a mixture of above-mentioned substances with β-lead peroxide mixed at any mix ratio.

4. The method according to claim 3, wherein the dosage of the promoter is 0.05-30 wt % of the filter residue obtained in step (1).

5. The method according to claim 1, further comprising: cooling a product obtained in step (2) to 100-300° C. during a period of 0.5-30 min before performing step (3).

6. The method according to claim 5, wherein the cooling is carried out in a manner of liquid mist cooling.

7. The method according to claim 1, wherein the alkaline solution A used in step (3) is either or both of sodium hydroxide solution and potassium hydroxide solution, the concentration of the alkaline solution A is 12-60 wt %, and the dosage of the alkaline solution A ensures that the concentration of a product obtained in step (2) used in the contact in step (3) is 30-120 g/L, the contact temperature in step (3) is 45-135° C., and the contact time in step (3) is 0.5-100 min.

8. The method according to claim 1, wherein in step (4), a crystallization process is carried out in stages, including: a first stage of crystallization at 60-135° C. and a second stage of crystallization at −5° C. to 60° C., wherein, the duration of the first stage of crystallization is 1-60 min, the duration of the second stage of crystallization is 3-600 min.

9. The method according to claim 1, further comprising: (5) treating the PbO crystals obtained in step (4) by ball milling for crystal transformation, to obtain PbO in α-structure.

10. The method according to claim 9, wherein the conditions of ball milling for crystal transformation include: based on 1,000 g lead oxide, the mass of the balls is 5-500 g, the number of the balls is 5-100, the ball milling time is 0.1-200 min, and the temperature is 5-550° C.

11. The method according to claim 1, further comprising: substituting a product obtained in step (2) with the PbO crystal obtained in step (4) and repeating step (3) and step (4) cyclically.

12. The method according to claim 1, wherein the contact between the lead oxide-containing waste and the desulfurizing agent is implemented through a wet ball milling and mixing process.

13. The method according to claim 1, wherein in step (1), the desulfurizing agent is NaOH and/or KOH solution, and the concentration of the NaOH and/or KOH solution is 4-23 wt %.

14. The method according to claim 5, wherein cooling a product obtained in step (2) to 100-150° C. during a period of 1-10 min, before performing step (3).

15. The method according to claim 6, wherein a coolant of the cooling is one or more of water, methanol, ethanol, and acetone.

16. The method according to claim 6, wherein the size of mist droplets is 2-50 μm.

17. The method according to claim 5, further comprising: substituting a product obtained in step (2) with the PbO crystal obtained in step (4) and repeating step (3) and step (4) cyclically.

18. The method according to claim 9, further comprising: substituting a product obtained in step (2) with the PbO crystal obtained in step (4) and repeating step (3) and step (4) cyclically.

Description

DETAILED DESCRIPTION OF THE EMBODIMENTS

(1) Hereunder the present invention will be detailed in some embodiments. It should be appreciated that the embodiments described here are only provided to describe and explain the present invention, but shall not be deemed as constituting any limitation to the present invention.

(2) According to the present invention, a method for recovering lead oxide from lead oxide-containing wastes is provided, comprising the following steps:

(3) (1) controlling a lead oxide-containing waste to contact with a desulfurizing agent under desulphurization reaction conditions, and carrying out solid-liquid separation for the mixture obtained from the contact reaction, to obtain filtrate and filter residue;
(2) controlling the filter residue to have a conversion reaction at 350-750° C. temperature, to convert the lead-containing components in the filter residue into lead oxide;
(3) controlling the product obtained in step (2) to contact with alkaline solution, to dissolve the PbO in the product, and then carrying out solid-liquid separation to obtain PbO-alkaline solution;
(4) controlling the PbO-alkaline solution obtained in step (3) to crystallize, to obtain PbO crystals and alkaline filtrate.

(4) In the method according to the present invention, in step (1), the purpose of controlling the lead oxide-containing waste to contact with a desulfurizing agent is to remove lead sulfate in the lead oxide-containing waste. Therefore, a desulfurizing agent applicable to the present invention can be any known substance that can react with lead sulfate in the lead oxide-containing waste to generate soluble sulfate and sulfur-free lead compounds in the art. The desulfurizing agent is preferably NaOH and/or KOH solution, more preferably NaOH solution.

(5) In the method according to the present invention, in step (1), the process of contact between the lead oxide-containing waste and the desulfurizing agent can be implemented through a conventional desulphurization process in a reactor, or implemented through a wet ball milling process. The inventor of the present invention has found: by controlling the lead oxide-containing waste and the desulfurizing agent (in particular, NaOH and/or KOH solution) to mix and contact in the wet ball milling process, a more homogeneous stirred milling effect can be attained more quickly when compared with the conventional stirred mixing process in a reactor, the yield rate of PbO and the purity of PbO product can be greatly improved subsequently, and the time required for the contact in the follow-up step (1) can be shortened. Therefore, preferably the contact between the lead oxide-containing waste and the desulfurizing agent in the present invention is implemented by means of a wet ball milling and mixing process. The ball milling conditions preferably include: based on 1,000 g lead oxide-containing waste, the mass of the balls is 5-500 g, more preferably 3-300 g, the number of the balls is 5-100, the ball milling time is 0.1-200 min., the ball milling reaction temperature is controlled at −5° C.-105° C., more preferably 10-80° C., wherein, the balls are preferably zirconium balls or agate balls.

(6) Though high-concentration sodium sulfate and/or potassium sulfate solution can be directly obtained from high-concentration alkaline solution (e.g., NaOH and/or KOH solution) after the reaction, it is difficult to fully disperse the lead oxide-containing waste in too little NaOH and/or KOH solution; consequently, the material will be very viscous in the stirring process. Through a large quantity of experiments, it is determined that the concentration of the NaOH and/or KOH solution in the present invention is preferably 4-23 wt %, to maintain an appropriate solid-liquid ratio between the NaOH and/or KOH and the lead oxide-containing waste and appropriate stirring viscosity and obtain mother liquid of sodium sulfate and/or potassium sulfate at appropriate concentration.

(7) In step (1), usually a slightly excessive amount of desulfurizing agent (preferably NaOH and/or KOH solution) is used, and the dosage is equivalent to 101-150% stoichiometric amount of lead sulfate in the lead oxide-containing waste. If the added amount of desulfurizing agent is inadequate, the desulphurization reaction between the PbSO.sub.4 and the desulfurizing agent will be incomplete; if the added amount of desulfurizing agent is excessive, the residual desulfurizing agent will cause PbO dissolution and increased Pb content in the filtrate; in addition, excessive desulfurizing agent solution will dilute the sulfate content in the mother liquid and cause decreased recovery rate of sodium sulfate and/or potassium sulfate in the follow-up procedures, or an additional evaporation procedure is required to ensure sodium sulfate and/or potassium sulfate can precipitate sufficiently.

(8) The method according to the present invention is applicable to recover lead oxide from different kinds of lead oxide-containing wastes, as long as the lead oxide-containing waste contains one or more of PbO, Pb, PbSO.sub.4, and PbO.sub.2. For example, the lead oxide-containing waste can be one or more of lead paste in waste lead-acid batteries, PbO waste obtained from recycled waste pole plates, other lead oxide-containing wastes produced in production of lead-acid batteries, and lead oxide-containing wastes produced in the production in other fields. Preferably, the lead oxide-containing waste is lead paste in waste lead-acid batteries, i.e., waste lead paste. Usually, the waste lead paste contains 10-15 wt % Pb, 10-20 wt % PbO, 25-35 wt % PbO.sub.2, and 30-45 wt % PbSO.sub.4.

(9) In the method according to the present invention, in step (2), the process is an atom-economic conversion process designed to implement conversion of Pb, PbO.sub.2, and PbO—Pb(OH).sub.2 obtained from desulphurization into PbO. The temperature of the conversion reaction in step (2) should be within 350-750° C. range, preferably within 390-620° C. range. The time of the conversion reaction in step (2) can be 3-70 min., preferably 5-40 min.

(10) In the method according to the present invention, the conversion reaction in step (2) preferably is carried out in existence of a promoter for atom-economic reaction. The existence of the promoter for atom-economic reaction can promote the desulphurized lead oxide-containing waste to be converted into PbO quickly and completely. The promoter for atom-economic reaction can be added in step (1) and/or step (2).

(11) In the present invention, the promoter for atom-economic reaction can be any substance that can react with PbO.sub.2 to generate PbO, for example, the promoter for atom-economic reaction can be one or more of metal powder, carbon powder, naphthalene, camphor, urea, and active carbon containing 0.5-95 wt % PbO, or a mixture of one or more of the above-mentioned substances and β-lead peroxide mixed at any ratio. For example, the metal powder can be one or more of lead powder, barium powder, aluminum powder, sodium powder, lithium powder, potassium powder, magnesium powder, nickel powder, tin power, stibium powder, and zinc powder. More preferably, the particle diameter of the promoter for atom-economic reaction is controlled at 80-600 meshes.

(12) In a preferred embodiment according to the present invention, the promoter for atom-economic reaction is a mixture of lead powder and β-lead peroxide, and the weight ratio of lead powder to β-lead peroxide is 1:0.05-2. With the preferred promoter for atom-economic reaction, the reaction can be carried out quickly, and the cost is low.

(13) The dosage of the promoter for atom-economic reaction can be selected as required, as long as it ensures that the above-mentioned conversion process can be executed fully. The dosage of the promoter for atom-economic reaction is preferably 0.05-30 wt % of the total weight of the filter residue obtained in step (1), more preferably 1-20 wt %.

(14) Moreover, the inventor of the present invention has found: by cooling the conversion product obtained in step (2) at an appropriate cooling rate, on one hand, the crystal form of the PbO product can be mainly kept as α-structure, on the other hand, PbO oxidation can be prevented. Accordingly, preferably the method provided in the present invention further comprises: cooling the product obtained in step (2) to 100-300° C. within 0.5-30 min, more preferably cooling to 100-150° C. within 1-10 min, before the step (3) is executed. More preferably, the cooling method is liquid mist cooling, so as to obtain a better cooling effect, wherein, the coolant is preferably one or more of water, methanol, ethanol, and acetone. In the liquid mist cooling procedure, the size of the mist droplets is preferably 2-50 μm.

(15) To obtain a high-purity PbO product, the method disclosed in the present invention further comprises the following step (3): controlling the product obtained in step (2) and/or the cooled product to contact with alkaline solution, to dissolve the PbO in the product, and then carrying out solid-liquid separation. The alkaline solution can be either or both of sodium hydroxide solution and potassium hydroxide solution. The concentration of the alkaline liquid can be 12-60 wt %. The dosage of the alkaline solution is determined in a way that the concentration of the product obtained in step (2) in the contact system in step (3) is 30-120 g/L, the contact temperature is 45-135° C., and the contact time is 0.5-100 min. Preferably, the alkaline solution is pre-heated to the above-mentioned contact temperature, and then the alkaline solution contacts with the product obtained in step (2) and/or the cooled product.

(16) In the method according to the present invention, the alkaline solution may have some PbO dissolved in it. Specifically, the alkaline solution may have PbO of 60 g/L or lower content dissolved in it.

(17) More preferably, to accelerate the dissolution of the product obtained in step (2) and/or the cooled product or improve the solubility of the product obtained in step (2) and/or the cooled product in the alkaline solution, the contact between the product obtained in step (2) and/or the cooled product and the alkaline solution is carried out in existence of a dissolution promoter. The dissolution promoter is preferably one or more of ethylene diamine, sodium acetate, sodium tartrate, EDTA, glycerol, butanediol, pentanol, sorbitol, xylitol, histidine, arginine, and glycocoll. The dosage of the dissolution promoter is 0.2-20 wt % of the alkaline solution, preferably 0.5-15 wt %.

(18) In the method according to the present invention, the solid-liquid separation in step (1) and step (3) can be implemented with any solid and liquid separation method known in the art, such as pressure filtration or centrifugal separation. In a preferred embodiment, the solid-liquid separation in step (3) is pressure filtration at 65-120° C. (preferably 70-110° C.). The pressure filtration can be implemented with a LOX filter press, for example.

(19) To obtain PbO solid at higher purity, the method disclosed in the present invention preferably comprises: repeating step (3) to step (4) again or cyclically, i.e., substitute the product obtained in step (2) with the PbO crystal obtained in step (4) and repeat step (3) and step (4) cyclically. In step (4), the crystallization process is cooling crystallization, and PbO crystals and mother liquid after crystallization (i.e., alkaline filtrate) are obtained through the cooling crystallization process. Experiments have shown: through repeated purification, the purity of the PbO crystals usually can be 99.99% or higher.

(20) In general, the preparation of high-purity lead oxide powder consists of two procedures: the PbO crude product is dissolved in alkaline solution, to complete the first stage of dissolution; in the case that the alkaline solution is NaOH solution, the reaction formula can be expressed as follows:
PbO(impure)+NaOH(aq)=NaHPbO.sub.2(aq)+impurities  (1)

(21) To obtain PbO of high-purity, the alkaline solution with PbO dissolved in it should be treated by solid-liquid separation to obtain PbO-containing alkaline solution (i.e., PbO-alkaline solution) and impurity-containing filter residue.

(22) Usually, the filter residue contains 30-50 wt % barium sulfate and 5-10 wt % Ca(OH).sub.2, while the remaining part is PbO. The barium sulfate can be separated from the filter residue through a simple HClO.sub.4 or nitric acid dissolution process, and then the barium sulfate can be returned to the negative electrode production process of lead-acid batteries.

(23) After the impurities are removed, the PbO solution should be treated through a crystallization process to obtain PbO crystals and alkaline filtrate. The alkaline filtrate can be used in the dissolution-crystallization process of the PbO crude product repeatedly. In case the alkaline solution is NaOH solution, the reaction formula of the crystallization process can be expressed as follows:
NaHPbO.sub.2(aq)=PbO(s)+NaOH(aq)  (2)

(24) It can be seen that if the PbO after crystallization still contains some impurities, the PbO can be further purified through the dissolution-crystallization process in the alkaline solution.

(25) Under actual PbO crystallization conditions, the nucleation process and the growing process are not completely separated from each other. If the nucleation time is too long, some crystal nuclei will enter into the growing process and begin to grow before the nucleation process is completed; consequently, some bulky grain crystals will produce when the nucleation process is completed, and the alkaline mother liquid may be included in the bulky grain crystals. The nucleation process and the growing process can be deemed as completely separated from each other without interference only if the nucleation rate is much higher than the growing rate. In that case, the obtained crystal grains are mono-dispersed crystal grains, the average size of the crystal grains is very small, and the distribution of the crystal grains is concentrated. To obtain such type of crystal grains, the nucleation rate must be increased as much as possible while the growing rate must be decreased as much as possible, or the growing time must be shortened as far as possible on the premise of ensuring full crystallization. Therefore, with respect to the dissolution process of the PbO crude product, the control of the crystallization process of the PbO solution and the post-treatment of the crystallized product are critical. The crystallization process of PbO has a direct influence on the crystal form and structure of PbO, the size of crystal grain, and the content of impurities introduced by adsorption or crystallization process. Hence, in a preferred embodiment, in step (4), the crystallization process is carried out in stages, including: a first stage of crystallization at 60-135° C. and a second stage of crystallization at −5° C. to 60° C., wherein, the duration of the first stage of crystallization is 1-60 min, the duration of the second stage of crystallization is 3-600 min. More preferably, the duration of the first stage of crystallization is 1-60 min, the duration of the second stage of crystallization is 3-600 min.

(26) In another preferred embodiment, the method provided in the present invention further comprises: (5) treating the PbO crystals obtained in step (4) by ball milling for crystal transformation, to obtain PbO in typical α-structure.

(27) The operating conditions of the ball milling for crystal transformation in the present invention may include: based on 1,000 g lead oxide, the mass of the balls is 5-500 g, preferably 3-300 g, the number of the balls is 5-100, the ball milling time is 0.5-200 min, and the temperature of the ball milling for crystal transformation is controlled at 5-550° C., preferably 30-460° C.

(28) The inventor of the present invention has found: in the case that the desulfurizing agent is NaOH solution, by adding denser NaOH solution or solid NaOH into the filtrate obtained in step (1) to increase the concentration of NaOH in the filtrate to 90-150% of the concentration before the contact, the sodium sulfate generated in the desulphurization reaction in step (1) can precipitate directly, and thereby a sodium sulfate product can be obtained through a simple solid-liquid separation procedure, and the filtrate (NaOH solution) can be directly recycled and reused. Hence, preferably, the desulfurizing agent is NaOH solution. Accordingly, the method disclosed in the present invention further comprises: supplementing the desulfurizing agent into the filtrate obtained in step (1), and controlling the concentration of the desulfurizing agent in the filtrate to 90-150% of the concentration before the contact.

(29) With the method provided in the present invention, lead oxide-containing wastes can be converted efficiently into high-purity lead oxide, while the energy consumption can be reduced significantly, the use of any toxic or harmful material in the recovery process and possible secondary pollution thereof can be avoided; in addition, totally enclosed and continuous industrial production can be realized.

(30) Hereunder the present invention will be further detailed in some examples.

Example 1

(31) This example is provided to explain the method for directly recovering lead oxide from waste lead paste of lead-acid batteries used in electric vehicles in the present invention.

(32) Weigh 10 Kg waste lead paste obtained from 12V, 12 Ah waste and worn batteries of electric vehicles. Through analysis, the weight percentages of major components in the waste lead paste are: 20% PbO, 11% Pb, 35% PbSO.sub.4, 30% PbO.sub.2, 0.35% BaSO.sub.4, and 0.2% SiO.sub.2, and the remaining part is sulfuric acid solution of 20 wt % concentration. The lead compounds in the 10 Kg waste lead paste are equivalent to 38.39 mol PbO.

(33) The lead oxide recovery process is as follows:

(34) (1) mix the 10 kg waste lead paste with 15 L 8.5 wt % NaOH solution at 20° C., and carry out ball milling (based on 1,000 g waste lead paste, the mass of the balls is 300 g, agate balls are used) for 10 min, and then filter to obtain filtrate and filter residue;
(2) mix the filter residue with 0.1 Kg promoter for atom-economic reaction of 160 meshes (the weight ratio of Pb powder to β-PbO.sub.2 is 1:0.5) to a homogeneous state, and heat up the mixture to 460° C. using a temperature programming method with a heating rate of 5° C./min, keep the reaction for 20 min at 460° C. temperature, to enable the reaction to be carried out homogeneously and fully;
(3) cool the product obtained in step (2) by water mist cooling within 0.5 min (the size of water mist droplets is 25 μm) to 150° C., and stop water spraying at that temperature;
(4) control the cooled product obtained in step (3) to contact with 80 L 35 wt % NaOH solution to dissolve the PbO in the product, wherein, to promote the dissolution of the PbO, the NaOH solution is heated up to 120° C., and 1,200 g EDTA is added into the solution. Stir at 100 rpm for 15 min, to enable the PbO obtained in step (3) to be fully dissolved in the NaOH solution;
(5) control the filtrate obtained through solid-liquid separation in step (4) to crystallize for 60 min and 300 min at 80° C. and 5° C. respectively, and carry out solid-liquid separation for the PbO obtained in the two crystallization stages to separate it from the mother liquid, wherein, after the separation, the mother liquid contains 20 g/L PbO, and the NaOH mother liquid that contains the residual PbO can be used in step (4) repeatedly;
(6) treat the PbO crystals obtained in step (5) by ball milling in a ball mill for crystal transformation, wherein, the crystal transformation conditions include: based on 1,000 g lead oxide-containing waste, the mass of the balls is 200 g, the number of the balls is 50, the ball milling time is 30 min, and the ball milling reaction temperature is controlled at 130° C.;
(7) supplement NaOH into the filtrate obtained in step (1), till the NaOH concentration in the filtrate reaches 105% of the concentration before the contact, to enable the sodium sulfate in the filtrate to precipitate, and then carry out solid-liquid separation. 3 kg sodium sulfate crystals of 98.5% purity are obtained through solid-liquid separation, while a part of sodium sulfate remains in the NaOH desulfurizing liquid. After concentration adjustment, the NaOH solution can be reused in step (1).

(35) After drying, the recovered PbO sample is weighed 6.95 Kg; an ICP test indicates that the purity is 99.99%, an XRD test indicates that the α-PbO content is 95%; with the PbO that remains in the NaOH mother liquid in step (5) taken into account, the PbO recovery rate is 99.7%.

Example 2

(36) This example is provided to explain the method in the present invention, in which the NaOH mother liquid obtained in step (4) and the NaOH desulfurization liquid in step (7) after a first cycle of lead oxide recovery from waste lead paste in lead-acid batteries of electric vehicles in Example 1 are used in a second cycle to recover PbO.

(37) Weigh another 10 kg waste lead paste that is the same as the waste lead paste in Example L The cyclic PbO recovery process is as follows:

(38) (1) mix the waste lead paste obtained from lead-acid batteries with the 8.9 wt % NaOH solution obtained in step (7) in Example 1 and carry out ball milling (based on 1,000 g waste lead paste, the mass of the balls is 130 g, agate balls are used) for 30 min, and then filter to obtain filtrate and filter residue;
(2) mix the filter residue with 500 g promoter for atom-economic reaction of 200 meshes (the weight ratio of Pb powder to β-PbO.sub.2 is 1:2) to a homogeneous state, and heat up the mixture to 530° C. using a temperature programming method with a heating rate of 10° C./min, keep the reaction for 10 min at 530° C. temperature, to enable the reaction to be carried out homogeneously and fully;
(3) cool the product obtained in step (2) by water mist cooling (the size of water mist droplets is 10 μm) to 120° C., and stop water spraying at that temperature;
(4) control the cooled product obtained in step (3) to contact with the 35 wt % NaOH mother liquid recovered in Example 1, keep the temperature at 125° C., and stir for 10 min at 120 rpm speed, to enable the PbO obtained in step (3) to be fully dissolved in the NaOH mother liquid;
(5) control the filtrate obtained through solid-liquid separation in step (4) to crystallize for 40 min and 300 min at 75° C. and 10° C. respectively, and then carry out solid-liquid separation to obtain PbO crystals and NaOH mother liquid, wherein, the NaOH mother liquid contains 22 g/L PbO, and 70 g water is added to the NaOH mother liquid, so that the NaOH concentration is recovered to the initial concentration; then, the NaOH liquid is reused in step (4);
(6) treat the PbO crystals obtained in step (5) by ball milling in a ball mill for crystal transformation, wherein, the crystal transformation conditions include: based on 1,000 g lead oxide-containing waste, the mass of the balls is 300 g, the number of the balls is 20, the ball milling time is 100 min, and the ball milling reaction temperature is controlled at 60° C.;
(7) supplement NaOH into the filtrate obtained in step (1), till the NaOH concentration in the filtrate reaches 115% of the concentration before the contact, to enable the sodium sulfate in the filtrate to precipitate, and then carry out solid-liquid separation. After solid-liquid separation, 3.4 Kg sodium sulfate crystals of 99.0% purity is obtained, and the recovery rate of sodium sulfate is 95%; after the product is dried at 150° C. for 1 h, and then weighed and analyzed by ICP, the product is 8.4 Kg PbO of 99.99% purity, and an XRD test indicates the product contains 90% α-PbO, and the lead recovery rate is 99.8%.

Example 3

(39) Take 1 Kg waste lead paste obtained from lead-acid batteries. Through analysis, the major components in the waste lead paste are: 13 wt % Pb, 18 wt % PbO, 33 wt % PbO.sub.2, 35 wt % PbSO.sub.4, and 0.3 wt % BaSO.sub.4, and the remaining part is water. The waste lead paste is equivalent to 3.97 mol PbO, and the cyclic PbO recovery process is as follows:

(40) (1) mix the waste lead paste with 1.3 L 10 wt % NaOH solution, and carry out ball milling (based on 1,000 g waste lead paste, the mass of the balls is 200 g, agate balls are used) for 20 min, and then filter to obtain filtrate and filter residue;

(41) (2) mix the filter residue with promoter for atom-economic reaction of 300 meshes (the weight ratio of carbon powder to β-PbO.sub.2 is 1:1) to a homogeneous state, and heat up the mixture to 570° C. using a temperature programming method with a heating rate of 10° C./min, keep the reaction for 5 min at the temperature while turning over, to enable the reaction to be carried out homogeneously and fully, wherein, the dosage of the promoter for atom-economic reaction is 1 wt % of the filter residue;
(3) cool the product obtained in step (2) by water mist cooling (the size of water mist droplets is 30 μm) to 110° C. within 6 min, and stop water spraying at that temperature;
(4) control the cooled product in step (3) to contact with 9 L 25 wt % NaOH solution and ethylene diamine, heat up the mixture to 115° C., stir at 60 rpm speed at the temperature for 10 min, to dissolve the PbO; then, carry out solid-liquid separation, wherein, the weight ratio of NaOH solution to ethylene diamine is 1:0.05;
(5) control the filtrate obtained through solid-liquid separation in step (4) to crystallize for 60 min and 350 min at 70° C. and 10° C. respectively, to obtain PbO crystals and crystallized mother liquid, reuse the crystallized mother liquid obtained in step (5) in step (4);
(6) treat the PbO crystals obtained in step (5) by ball milling in a ball mill for crystal transformation, wherein, the crystal transformation conditions include: based on 1,000 g lead oxide-containing waste, the mass of the balls is 80 g, the number of the balls is 20, the ball milling time is 10 min, and the ball milling reaction temperature is controlled at 80° C.;
(7) supplement NaOH into the filtrate obtained in step (1), till the NaOH concentration in the filtrate reaches 110% of the concentration before the contact, to enable the sodium sulfate in the filtrate to precipitate, and then carry out solid-liquid separation. After solid-liquid separation, 290 g sodium sulfate crystal product of 99.0% purity is obtained, while the residual sodium sulfate remains in the desulphurization mother liquid and can accumulate and precipitate in subsequent desulphurization cycles. The liquid is NaOH solution, and the NaOH desulphurization mother liquid can be reused in step (1) after concentration adjustment.

(42) 790 g PbO is obtained in the experiment. Through ICP analysis, the purity is 99.99%, and an XRD test indicates that the content of α-PbO is 85%. Deducting the 93 g PbO dissolved in the NaOH solution in step (5), the recovery rate is 790/(3.97*223−93)=99.7%.

Example 4

(43) The lead oxide in the waste lead paste is recovered with the method in Example 3, and the NaOH mother liquid obtained in step (5) and the desulphurization mother liquid obtained in step (7) in Example 3 are used cyclically, except that the promoter for atom-economic reaction is lead powder. Finally, 884 g PbO is obtained; an ICP test indicates that the purity is 99.99%, and an XRD test indicates that the content of α-PbO is 86%, and the PbO recovery rate is 99.8%.

Example 5

(44) The lead oxide in the waste lead paste is recovered with the method in Example 3, and the NaOH mother liquid obtained in step (5) and desulphurization mother liquid obtained in step (7) in Example 4 are reused respectively, except that the temperature in step (2) is 500° C. Finally, 883 g PbO is obtained, the purity is 99.99%, and an XRD test indicates that the content of α-PbO is 89%, and the PbO recovery rate is 99.7%.

Example 6

(45) The lead oxide in the waste lead paste is recovered with the method in Example 3, and the NaOH mother liquid obtained in step (5) and desulphurization mother liquid obtained in step (7) in Example 5 are reused respectively, except that the temperature in step (2) is 600° C. Finally, 880 g PbO is obtained, the purity of the product is 99.95%, and an XRD test indicates that the content of α-PbO is 80%, and the PbO recovery rate is 99.4%.

Example 7

(46) The lead oxide in the waste lead paste is recovered with the method in Example 3, and the NaOH mother liquid obtained in step (5) and desulphurization mother liquid obtained in step (7) in Example 6 are reused respectively, except that the product obtained in step (2) is cooled to 100° C. quickly within 1 min in step (3). Finally, 881 g PbO is obtained, the purity of the product is 99.97%, and an XRD test indicates that the content of α-PbO is 85%, and the PbO recovery rate is 99.5%.

Example 8

(47) Take another 1 kg waste lead paste that is the same as the waste lead paste in Example 3. The waste lead paste is equivalent to 3.97 mol PbO, and the PbO recovery process is as follows:

(48) (1) mix the waste lead paste with 1.3 L 12 wt % KOH solution and carry out ball milling at 130% stoichiometric ratio (based on 1,000 g waste lead paste, the mass of the balls is 200 g, agate balls are used) for 20 min, and then filter to obtain filtrate and filter residue;
(2) mix the filter residue with promoter for atom-economic reaction of 300 meshes (the weight ratio of carbon powder to β-PbO.sub.2 is 1:1) to a homogeneous state, and heat up the mixture to 570° C. using a temperature programming method with a heating rate of 10° C./min, keep the reaction for 5 min at the temperature while turning over, to enable the reaction to be carried out homogeneously and fully, wherein, the dosage of the promoter for atom-economic reaction is 1 wt % of the filter residue;
(3) cool the product obtained in step (2) by water mist cooling (the size of water mist droplets is 30 μm) to 110° C. within 6 min, and stop water spraying at that temperature;
(4) control the cooled product in step (3) to contact with 9 L 33 wt % KOH solution and xylitol, heat up the mixture to 122° C., stir at 60 rpm speed at the temperature for 10 min, to dissolve the PbO; then, carry out solid-liquid separation, wherein, the weight ratio of KOH solution to xylitol is 1:0.02;
(5) control the filtrate obtained through solid-liquid separation in step (4) to crystallize for 60 min and 360 min at 65° C. and 5° C. respectively, to obtain PbO crystals and crystallized mother liquid, reuse the crystallized mother liquid obtained in step (5) in step (4);
(6) treat the PbO crystals obtained in step (5) by ball milling in a ball mill for crystal transformation, wherein, the crystal transformation conditions include: based on 1,000 g lead oxide-containing waste, the mass of the balls is 80 g, the number of the balls is 20, the ball milling time is 10 min, and the ball milling reaction temperature is controlled at 80° C.;
(7) supplement KOH into the filtrate obtained in step (1), till the KOH concentration in the filtrate reaches 105% of the concentration before the contact, to enable the potassium sulfate in the filtrate to precipitate, and then carry out solid-liquid separation. After solid-liquid separation, 160 g potassium sulfate crystal product of 99.2% purity is obtained, while the residual potassium sulfate remains in the desulphurization mother liquid and can accumulate and precipitate in subsequent desulphurization cycles. The liquid obtained after potassium sulfate precipitates is KOH solution, and the KOH desulphurization mother liquid can be reused in step (1) after concentration adjustment.

(49) 802 g PbO is obtained in the experiment. Through ICP analysis, the purity is 99.99%, and an XRD test indicates that the content of α-PbO is 83%. Deducting the 81 g PbO dissolved in the KOH solution in step (5), the recovery rate is 802/(3.97*223−81)=99.7%.

Example 9

(50) The lead oxide-containing waste used in this example is lead oxide-containing waste from Henan Jiyuan Smelting Plant. Through analysis, the major components in the lead oxide-containing waste include: 65 wt % PbO, 24 wt % PbSO.sub.4, and the remaining part consists of insoluble impurities, including 4 wt % CaSiO.sub.3, 5 wt % Al.sub.2O.sub.3, and 2 wt % SiO.sub.2, etc. Weigh 1 Kg lead oxide-containing waste, which is equivalent to 826.6 g PbO. The lead oxide recovery process is as follows:

(51) (1) mix and stir the lead oxide-containing waste with 0.9 L 10 wt % NaOH solution at 150% stoichiometric ratio in a reactor for desulphurization. Stir at 60 rpm for 20 min, and then filter to obtain filtrate and filter residue;

(52) (2) heat up the filter residue to 520° C. using a temperature programming method with a heating rate of 10° C./min, keep the reaction at 520° C. for 55 min, to ensure the reaction to be carried out homogeneously and fully;

(53) (3) cool the product obtained in step (2) by ethanol mist cooling (the size of mist droplets is 30 μm) to 100° C. within 6 min, and stop mist spraying at that temperature;

(54) (4) control the cooled product in step (3) to contact with 10 L 33 wt % NaOH solution (with dissolved PbO, and the PbO concentration is 30 g/L) and xylitol, wherein, the weight ratio of NaOH solution to xylitol is 1:0.02; heat up the mixture to 125° C., stir at 60 rpm speed at the temperature for 10 min, to promote the PbO in the product obtained in step (3) to be dissolved; then, carry out solid-liquid separation;
(5) control the filtrate obtained through solid-liquid separation in step (4) to crystallize for 60 min and 350 min at 70° C. and 8° C. respectively, to obtain PbO crystals and crystallized mother liquid; reuse the crystallized mother liquid obtained in step (5) in step (4);
(6) treat the PbO crystals obtained in step (5) by ball milling in a ball mill for crystal transformation, wherein, the crystal transformation conditions include: based on 1,000 g lead oxide-containing waste, the mass of the balls is 80 g, the number of the balls is 20, the ball milling time is 10 min, and the ball milling reaction temperature is controlled at 100° C.;
(7) supplement NaOH into the filtrate obtained in step (1), till the NaOH concentration in the filtrate reaches 102% of the concentration before the contact, to enable the sodium sulfate in the filtrate to precipitate, and then carry out solid-liquid separation. After solid-liquid separation, 140 g sodium sulfate crystal product of 99.2% purity is obtained, while the residual sodium sulfate remains in the desulphurization mother liquid and can accumulate and precipitate in subsequent desulphurization cycles. The liquid obtained after sodium sulfate precipitates is NaOH solution, and the NaOH solution can be reused in step (1) after concentration adjustment.

(55) Through the ball milling process for crystal transformation in step (6), 825.1 g PbO is obtained. Through ICP analysis, the purity is 99.99%, an XRD indicates that the content of α-PbO is 80%, and the recovery rate is 825.1/826.6=99.8%.

(56) Preferred embodiments of the present invention are described above in detail, however, the present invention is not limited to the specific details of the above embodiments, technical solutions of the present invention may have various simple modifications within the technical spirit of the present invention, and these simple modifications belong to the scope of the present invention.

(57) In addition, it should be noted that each specific technical characteristic described in the above specific embodiments can be combined in any suitable manner, without contradictory situation. In order to avoid unnecessary repetition, various possible combinations are not further explained in the present invention.

(58) Moreover, various embodiments of the present invention may also be combined in any suitable manner, as long as it will not depart from the idea of the present invention, and the combinations should be regarded as the disclosure of the present invention.