Method for directly recovering lead oxide used for a lead-acid battery cathode from waste lead paste

Abstract

Provided is a method for directly recovering lead oxide used for a lead-acid battery negative electrode from waste lead paste. The method comprises: (1) contacting waste lead paste with a barium-containing desulphurizer under desulphurization reaction conditions, and performing a solid-liquid separation on the mixture after contacting to obtain a filtrate and a filtration residue; and (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. In the method, the direct recovery of a lead oxide raw material applicable to a lead-acid battery negative electrode from waste lead paste is achieved by quantitatively replenishing a barium sulphate additive in the process of desulphuration thereby substantially decreasing the recovery cost and energy consumption, and improving the comprehensive utilization of waste lead paste.

Claims

1. A method for directly recovering lead oxide for negative electrode of lead-acid battery from waste lead paste, comprising the following steps: (1) controlling waste lead paste to contact with a barium-containing 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., to convert lead-containing components in the filter residue into lead oxide, thereby obtaining a product of lead oxide and barium sulfate; wherein the barium-containing desulfurizing agent is NaOH and/or KOH solution containing soluble barium compound and/or barium sulfate and the concentration of the NaOH and/or KOH solution is 4-23 wt %.

2. The method according to claim 1, wherein based on the total weight of the barium-containing desulfurizing agent, the content of the soluble barium compound and/or barium sulfate is 0.001-15 wt %.

3. The method according to claim 1, wherein the soluble barium compound is one or more of barium hydroxide, barium nitrate, barium perchlorate, barium chloride, and barium acetate.

4. 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).

5. The method according to claim 4, wherein the promoter is selected from the group consisting of lead powder, barium powder, aluminum powder, sodium powder, lithium powder, potassium powder, magnesium powder, nickel powder, tin powder, stibium powder, zinc powder, naphthalene, camphor, urea, carbon powder, active carbon containing 0.5-95 wt % PbO, and a mixture of the above-mentioned substances with β-lead peroxide mixed at any mix ratio.

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

7. The method according to claim 1, further comprising: supplementing the barium-containing desulfurizing agent into the filtrate obtained in step (1), and controlling the concentration of the barium-containing desulfurizing agent in the obtained filtrate to 90-150% of the concentration before the contact.

8. The method according to claim 1, further comprising: cooling product obtained in step (2) to 100-300° C. within during a period of 0.5-30 min following the completion of step (2).

9. The method according to claim 8, wherein the cooling is implemented by means of liquid mist cooling, and the coolant is one or more of water, methanol, ethanol, and acetone.

10. The method according to claim 1, wherein the contact between the waste lead paste and the barium-containing desulfurizing agent is implemented by means of a wet ball milling and mixing process.

11. The method according to claim 10, wherein the ball milling conditions include: based on 1,000 g waste lead paste, 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° C. to 105° C.

12. The method according to claim 4, further comprising: supplementing the barium-containing desulfurizing agent into the filtrate obtained in step (1), and controlling the concentration of the barium-containing desulfurizing agent in the obtained filtrate to 90-150% of the concentration before the contact.

13. The method according to claim 8, wherein cooling the product obtained in step (2) to 100-150° C. during a period of 1-10 min following the completion of step (2).

14. The method according to claim 13, wherein the cooling is implemented by means of liquid mist cooling, and the coolant is one or more of water, methanol, ethanol, and acetone.

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 directly recovering lead oxide for negative electrode of lead-acid battery from waste lead paste is provided, comprising the following steps:

(3) (1) controlling waste lead paste 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;

(4) (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.

(5) In the method according to the present invention, in step (1), the process of contact between the waste lead paste and the desulfurizing agent can be implemented through a conventional desulphurization process in a reactor, or implemented through a wet ball milling process, for the purpose of quickly milling large particles in the lead paste and attaining an effect of removing lead sulfate completely from the waste lead paste.

(6) The inventor of the present invention has found: by controlling the waste lead paste and the desulfurizing agent (in particular, NaOH solution) to mix and contact in the wet ball milling process, 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 waste lead paste 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 waste lead paste, 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, more preferably 0.5-60 min, the ball milling reaction temperature is controlled at −5° C. to 105° C., more preferably 10-80° C. The balls are preferably zirconium balls or agate balls.

(7) In the present invention, the desulfurizing agent can be any known material that can have a reaction with lead sulfate in waste lead paste to generate soluble sulfate and lead oxide or lead hydroxide in the art, and preferably is NaOH and/or KOH solution, more preferably is NaOH solution. The concentration of the NaOH and/or KOH solution is preferably 4-23 wt %.

(8) In a preferred embodiment according to the present invention, as the desulfurizing agent, the NaOH and/or KOH solution further contains soluble barium compound and/or barium sulfate. Based on the total weight of the desulfurizing agent, the content of the soluble barium compound and/or barium sulfate can be 0.001-15 wt %. In the present invention, the soluble barium compound can be one or more of barium hydroxide, barium nitrate, barium perchlorate, barium chloride, and barium acetate, and is preferably barium hydroxide. If the NaOH and/or KOH solution that serves as the desulfurizing agent contains barium hydroxide, the barium hydroxide can attain dual effects of desulphurization and barium sulfate addition.

(9) 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 waste lead paste 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 waste lead paste and appropriate stirring viscosity and obtain mother liquid of sodium sulfate and/or potassium sulfate at appropriate concentration.

(10) In step (1), usually a specific amount or slightly excessive amount of desulfurizing agent (preferably NaOH and/or KOH solution) is used according to the content of lead sulfate in the lead paste. Usually, the stoichiometric ratio is 101-150%. If the added amount of desulfurizing agent is inadequate, some PbSO.sub.4 will remain, and the desulphurization effect will be compromised; 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 will cause decreased content of sodium sulfate and/or potassium sulfate in the mother liquid and decreased recovery rate of sodium sulfate and/or potassium sulfate per cycle in the follow-up procedures, or an additional evaporation procedure is required to ensure sodium sulfate can precipitate sufficiently.

(11) In the method according to the present invention, the lead conversion process in step (2), in which an atom-economic conversion reaction is the core, mainly involves the following three reactions:

(12) (1) Pb and PbO.sub.2 in the filter residue generate PbO through an atom-economic reaction;

(13) (2) Residual PbO.sub.2 is decomposed into PbO;

(14) (3) Pb(OH).sub.2 obtained by desulphurization is decomposed into PbO.

(15) The inventor of the present invention has found: if the reaction time in step (2) is controlled within 3-70 min, preferably within 5-40 min, the Pb—PbO.sub.2, Pb(OH).sub.2, and residual PbO.sub.2 can be converted into PbO fully.

(16) 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 converting the waste lead paste after desulphurization into PbO quickly and completely, and can shorten the conversion time required in step (2). The promoter for atom-economic reaction can be added in step (1) and/or step (2).

(17) 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 mix ratio. The metal powder can be one or more of lead powder, barium powder, zinc powder, sodium powder, lithium powder, potassium powder, aluminum powder, magnesium powder, manganese powder, tin power, nickel powder, and stibium powder. More preferably, the particle diameter of the promoter for atom-economic reaction is controlled at 80-600 meshes.

(18) 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.

(19) 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. Preferably, the dosage of the promoter for atom-economic reaction is 0.05-30 wt % of the total weight of the filter residue obtained in step (1), more preferably 0.5-25 wt %, further more preferably 1-20 wt %.

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

(21) 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. 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.

(22) With the method provided in the present invention, waste lead paste can be converted efficiently into lead oxide that can be used for negative electrodes of lead-acid batteries, and, not only the energy consumption in the conversion process can be reduced significantly, but also the barium sulfate in the waste lead paste can be recovered in the recovering process and used as an additive for negative electrodes of new lead-acid batteries. Since an atom-economic reaction is the core in the entire process, the consumption of other chemical raw materials is avoided as far as possible; in addition, by using the mother liquid of desulphurization cyclically, the secondary pollution to the environment resulted from emission of lead-containing waste liquid is avoided, and totally-enclosed, continuous, and clean industrial production is realized. Hereunder the present invention will be further detailed in some examples.

Example 1

(23) 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.

(24) Crush 12V, 12 Ah waste and worn batteries used in electric vehicles to obtain waste lead paste, weigh 2 kg waste lead paste as the sample to be used in this example; through analysis, it is determined that the weight percentages of the main components in the waste lead paste are: 21% PbO, 9% Pb, 37% PbSO.sub.4, 31% PbO.sub.2, and 0.5% BaSO.sub.4, and the remaining part is sulfuric acid solution of 12 wt % concentration; the lead compounds in the waste lead paste are equivalent to 7.79 mol PbO.

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

(26) (1) mix the 2 kg waste lead paste with 2 L NaOH solution of 8.9 wt % concentration at 35° 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) heat up the filter residue to 490° C. using a temperature programming method with a heating rate of 5° C./min keep the reaction at 490° C. for 120 min, to ensure the reaction to be carried out homogeneously and fully;
(3) cool the product obtained in step (2) by water mist cooling within 1 min (the size of water mist droplets is 2-30 μm) to 150° C., and stop water spraying at that temperature;
(4) 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. 0.4 kg sodium sulfate crystals of 99.3% 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).

(27) Crush the product obtained in step (3) and sieve it through a 300 meshes sieve screen, to obtain 1.73 kg recovered PbO sample. Through ICP analysis, it is ascertained that the sample contains 0.55% barium sulfate. Through calculation, it is ascertained that the lead recovery rate is 99.6%, and the barium sulfate recovery rate is 95.5%.

Example 2

(28) This example is provided to explain that the NaOH solution obtained in step (4) in Example 1 in the present invention is reused in the desulphurization procedure in step (1).

(29) Weigh another 2 kg waste lead paste that is the same as the waste lead paste in Example 1. The cyclic PbO recovery process is as follows:

(30) (1) carry out ball milling and mixing for the waste lead paste of lead-acid battery and all NaOH solution obtained in step (4) in Example 1 (through titrimetric analysis, it is ascertained that the concentration of the NaOH solution is 9.5 wt %) for 30 min (based on 1,000 g waste lead paste, the mass of the balls is 130 g, and zirconium dioxide balls are used), and add 10.4 g 300 meshes lead powder and 6.0 g 300 meshes β-PbO.sub.2 (chemically pure) as a promoter for atom-economic reaction in the ball milling process, and then filter to obtain filtrate and filter residue;
(2) heat up the filter residue to 490° C. using a temperature programming method with a heating rate of 10° C./min, keep the reaction at 490° C. for 20 min, to ensure the reaction to be carried out homogeneously and fully;
(3) cool the product obtained in step (2) by water mist cooling within 1 min. (the size of water mist droplets is 2-30 μm) to 150° C., and stop water spraying at that temperature;
(4) 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. 0.55 kg sodium sulfate crystals of 99.2% 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).

(31) Crush the product obtained in step (3) and sieve it through a 300 meshes sieve screen, to obtain 1.75 kg recovered PbO sample. Through ICP analysis, it is ascertained that the sample contains 0.55% barium sulfate. Through calculation, it is ascertained that the lead recovery rate is 99.8%, and the barium sulfate recovery rate is 96.2%.

Example 3

(32) Weigh another 2 kg waste lead paste that is the same as the waste lead paste in Example 1. The composition of the waste lead paste is shown in Example 1.

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

(34) (1) mix the 2 kg waste lead paste with 2 L KOH solution of 13 wt % concentration at 40° 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) add 1.2 g 300 meshes carbon powder and 0.5 g naphthalene into the filter residue and mix homogeneously, heat up the mixture to 490° C. using a temperature programming method with a heating rate of 5° C./min, keep the reaction at 490° C. for 40 min,
(3) cool the product obtained in step (2) by water mist cooling within 1 min (the size of water mist droplets is 20-30 μm) to 150° C., and stop water spraying at that temperature;
(4) supplement KOH into the filtrate obtained in step (1), till the KOH concentration in the filtrate reaches 101% of the concentration before the contact, to enable the potassium sulfate in the filtrate to precipitate, and then carry out solid-liquid separation. 0.28 kg potassium sulfate crystals of 99.3% purity are obtained through solid-liquid separation, while a part of potassium sulfate remains in the KOH filtrate. After concentration adjustment, the KOH filtrate can be reused in step (1).

(35) Crush the product obtained in step (3) and sieve it through a 300 meshes sieve screen, to obtain 1.732 kg recovered PbO sample. Through ICP analysis, it is ascertained that the sample contains 0.56% barium sulfate. Through calculation, it is ascertained that the lead recovery rate is 99.7%, and the barium sulfate recovery rate is 96.8%.

Example 4

(36) Lead oxide is recovered from the waste lead paste with the method described in Example 3, except that 20 g 300 meshes lead powder is added in step (2) as a promoter for atom-economic reaction. In that way, 1.75 kg recovered PbO sample is obtained. Through ICP analysis, it is ascertained that the sample contains 0.55% barium sulfate. Through calculation, it is ascertained that the lead recovery rate is 99.6%, and the barium sulfate recovery rate is 96.2%.

Example 5

(37) Lead oxide is recovered from the waste lead paste with the method described in Example 3, except that 4 g 300 meshes carbon powder, 0.3 g 120 meshes aluminum powder, and 1 g urea are added in step (2) as a promoter for atom-economic reaction. In that way, 1.73 kg recovered PbO sample is obtained. Through ICP analysis, it is ascertained that the sample contains 0.56% barium sulfate. Through calculation, it is ascertained that the lead recovery rate is 99.5%, and the barium sulfate recovery rate is 96.9%.

Example 6

(38) Take 2 kg waste lead paste that is the same as the waste lead paste used in Example 1. The contents (weight percentages) of the components in the waste lead paste are: 21% PbO, 9% Pb, 37% PbSO.sub.4, 31% PbO.sub.2, and 0.5% BaSO.sub.4, and the remaining part is sulfuric acid solution of 12 wt % concentration. The lead compounds in the waste lead paste are equivalent to 7.79 mol PbO.

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

(40) (1) mix the 2 kg waste lead paste with 2 L desulfurizing agent at 35° C., wherein, the desulfurizing agent is NaOH solution of 8.8 wt % concentration, in which 8 g barium hydroxide is added; then, 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) heat up the filter residue to 510° C. using a temperature programming method with a heating rate of 5° C./min, keep the reaction at 510° C. for 60 min, to ensure the reaction to be carried out homogeneously and fully;
(3) cool the product obtained in step (2) by water mist cooling within 1 min (the size of water mist droplets is 2-30 μm) to 120° C., and stop water spraying at that temperature;
(4) 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. 0.4 kg sodium sulfate crystals of 99.3% 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).

(41) Crush the product obtained in step (3) and sieve it through a 300 meshes sieve screen, to obtain 1.73 kg PbO sample. Through ICP analysis, it is ascertained that the recycled PbO contains 0.99% barium sulfate. Through calculation, it is ascertained that the lead recovery rate is 99.6%, and the barium sulfate recovery rate is 96%.

(42) 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.

(43) 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.

(44) 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.