Method for recycling lead paste in spent lead-acid battery

Abstract

The disclosure discloses a method for recycling lead paste in a spent lead-acid battery, comprising: (1) pretreating lead paste in a spent lead-acid battery as a raw material under vacuum; mixing the pretreated lead paste with a chlorination reagent to obtain reactants; and heating the reactants under vacuum to carry out a chlorination volatilization reaction, so that lead element in the pretreated lead paste is combined with chlorine element in the chlorination reagent to form lead chloride, which is then volatilized, and after the reaction is completed, chlorination residue and a crude lead chloride product are obtained by condensation and crystallization after volatilization; (2) purifying the crude lead chloride product obtained in the step (1) under vacuum to obtain a refined lead chloride product. The disclosure improves the overall process flow of the recycling method as well as parameter conditions of the respective steps thereof, and can effectively solve the problem of serious pollution in lead paste recycling in the prior art.

Claims

1. A method for recycling lead paste in a spent lead-acid battery, comprising: pretreating lead paste in a spent lead-acid battery as a raw material under vacuum to convert lead dioxide in the lead paste into lead oxide; mixing the pretreated lead paste with a chlorination reagent to obtain reactants, the chlorination reagent being used to provide a chlorine element; and heating the reactants under vacuum to carry out a chlorination volatilization reaction, so that a lead element in the pretreated lead paste is combined with the chlorine element in the chlorination reagent to form lead chloride, which is then volatilized, and after the reaction is completed, chlorination residue and a crude lead chloride product are obtained by condensation and crystallization after volatilization; and purifying the crude lead chloride product under vacuum to separate other chloride impurities therein, thereby obtaining a refined lead chloride product.

2. The method for recycling lead paste in a spent lead-acid battery according to claim 1, further comprising: dissolving the chlorination residue with water, performing filtration to obtain a filtrate, and evaporating the filtrate to obtain a precipitate.

3. The method for recycling lead paste in a spent lead-acid battery according to claim 1, wherein the chlorination reagent is a mixture of calcium chloride and silica; and a temperature of the chlorination volatilization reaction and a ratio of the calcium chloride to the silica are optimized such that a residual amount of lead in the chlorination residue is minimized.

4. The method for recycling lead paste in a spent lead-acid battery according to claim 1, wherein the chlorination volatilization reaction is carried out by heating at a vacuum pressure of 0.1 to 10.sup.5 Pa and a temperature of 400 to 650° C.; the chlorination reagent is a mixture of calcium chloride and silica, wherein a molar ratio of the calcium chloride to the lead element in the pretreated lead paste is 12:1 to 30:1, and a molar ratio of the silica to the lead element in the pretreated lead paste is 12:1 to 60:1; and a percentage of lead element contained in the crude lead chloride product relative to lead element contained in the reactants is at least 68.5%.

5. The method for recycling lead paste in a spent lead-acid battery according to claim 1, wherein the step of purifying the crude lead chloride product is carried out by heating at a vacuum pressure of 0.1 to 1 Pa and a temperature of 200 to 400° C.

6. The method for recycling lead paste in a spent lead-acid battery according to claim 2, wherein the step of evaporating the filtrate is carried out at a temperature of 100 to 120° C.

7. The method for recycling lead paste in a spent lead-acid battery according to claim 1, wherein the lead paste has a lead content of 70 to 75 wt %.

8. The method for recycling lead paste in a spent lead-acid battery according to claim 2, further comprising constituting the chlorination reagent from the precipitate.

9. The method for recycling lead paste in a spent lead-acid battery according to claim 1, wherein a residual amount of lead in the chlorination residue is less than 0.05 mg/L.

10. The method for recycling lead paste in a spent lead-acid battery according to claim 1, wherein lead chloride in the refined lead chloride product has a purity of 99.8 wt % or more.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows XRD comparative patterns of the obtained lead chloride product and the analytically pure lead chloride product.

(2) FIG. 2 shows an SEM photograph of the obtained lead chloride product.

(3) FIG. 3 shows a schematic flow chart of a method for recycling lead paste in a spent lead-acid battery according to the present disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(4) For clear understanding of the objectives, features and advantages of the present disclosure, detailed description of the present disclosure will be given below in conjunction with accompanying drawings and specific embodiments. It should be noted that the embodiments described herein are only meant to explain the present disclosure, and not to limit the scope of the present disclosure. Furthermore, the technical features related to the embodiments of the disclosure described below can be mutually combined if they are not found to be mutually exclusive.

(5) In the present disclosure, the method for converting waste lead paste into a high-purity lead compound by a vacuum chlorination and volatilization process is a method for converting waste lead paste into a volatile lead compound by a vacuum chlorination and volatilization process, taking an example that the chlorination reagent is calcium chloride and silica (in the chlorination reagent, silica is used as an auxiliary reagent). As shown in FIG. 3, the method generally comprises the following steps:

(6) S1: manually disassembling a spent lead-acid battery to obtain waste lead paste, and calcining the waste lead paste under vacuum at a specific temperature to decompose lead dioxide in the waste lead paste into lead oxide and oxygen.

(7) S2: mixing the obtained pretreated waste lead paste with a mixture of calcium chloride and silica at a specific ratio, and performing a chlorination volatilization reaction under vacuum. Lead and lead oxides in the lead paste are converted into a volatile lead compound, and after the reaction is finished, a condensed lead compound product is collected on the tube wall; the condensed lead compound product is further purified by volatilizing chloride impurities in the lead compound product under vacuum at a specific temperature to obtain a secondary purified chlorination product.

(8) S3: dissolving the chlorination residue in water, and regenerating the excess of chlorination reagent (such as an excess of calcium chloride) by dissolution-filtration-evaporation processes (the regenerated calcium chloride can be recycled).

(9) Specifically, in the above step S1, there is no special requirement for component contents of lead and its compounds in the raw waste lead paste, and therefore the method has universality. Thus, the method has good adaptability to the waste lead paste with different species, and is applicable to most lead paste with a lead content of 70 to 75 wt %.

(10) In the step S1, the lead paste may have a pretreatment temperature of 500° C., at which lead dioxide can be decomposed, and lead sulfate and lead oxide are retained in the sample due to their difficulty in volatility, so that only oxygen is released throughout the process.

(11) In the above step S2, the chlorination temperature and the additive amounts of calcium chloride and silica (that is, calcium chloride and silica at a specific ratio) can be optimized by taking the residual amount of lead in the chlorination residue as an index to obtain optimal recycling conditions of the lead compound (i.e., an optimal dosing ratio of calcium chloride and silica and an optimal chlorination temperature). By subjecting the obtained lead compound product to secondary purification, a high-purity lead compound product can be obtained.

(12) In the above step S3, the chlorination reaction residue is subjected to dissolution-filtration-separation, and specifically, the aqueous phase (i.e., filtrate) is evaporated to dryness at 100 to 120° C. to obtain regenerated calcium chloride.

(13) By using calcium chloride and silica as a chlorination reagent, lead in waste lead paste is subjected to chlorination volatilization treatment under vacuum based on the volatility of lead chloride under vacuum, and the present disclosure will be further described in detail based on different chlorination temperatures.

Embodiment 1

(14) 2 g of waste lead paste (the lead content of the waste lead paste is 73.5 wt %, that is, there are 7.1×10.sup.−3 mol of lead element in 2 g of waste lead paste) was calcined at a vacuum pressure of 1 Pa and 500° C. for 10 min to decompose lead dioxide in the waste lead paste into lead oxide. In addition, elemental lead is also oxidized by lead dioxide into lead oxide. The pretreated waste lead paste is uniformly mixed with a calcium chloride/silica reagent mixture having a molar ratio of calcium chloride to lead of 30:1 and a molar ratio of silica to lead of 60:1, and then heated at a vacuum pressure of 1 Pa and 400° C. for 30 min. After heating was finished, a volatilized and condensed lead chloride product was collected on the quartz tube wall. The volatilization percentage of lead chloride was calculated by calculating lead contents in the sample before and after the reaction by the acid digestion method, and thus the volatilization percentage of lead chloride was calculated to be 68.5 wt %. The collected lead chloride product is heated at a vacuum pressure of 1 Pa and 350° C. for 10 min to obtain a secondary purified lead chloride product, and the purity of lead chloride can reach 99.8 wt %. The chlorination residue was dissolved in deionized water, insoluble matters in the chlorination residue were separated by a vacuum suction device, and the filtrate was evaporated to dryness at 105° C. to obtain a regenerated calcium chloride reagent.

Embodiment 2

(15) 2 g of waste lead paste (the lead content of the waste lead paste is 73.5 wt %, that is, there are 7.1×10.sup.−3 mol of lead element in 2 g of waste lead paste) was calcined at a vacuum pressure of 1 Pa and 500° C. for 10 min to decompose lead dioxide in the waste lead paste into lead oxide. In addition, elemental lead is also oxidized by lead dioxide into lead oxide. The pretreated waste lead paste is uniformly mixed with a calcium chloride/silica reagent mixture having a molar ratio of calcium chloride to lead of 30:1 and a molar ratio of silica to lead of 60:1, and then heated at a vacuum pressure of 1 Pa and 550° C. for 30 min. After heating was finished, a volatilized and condensed lead chloride product was collected on the quartz tube wall. The volatilization percentage of lead chloride was calculated by calculating lead contents in the sample before and after the reaction by the acid digestion method, and thus the volatilization percentage of lead chloride was calculated to be 99.7 wt %. The collected lead chloride product is heated at a vacuum pressure of 1 Pa and 350° C. for 10 min to obtain a secondary purified lead chloride product, and the purity of lead chloride can reach 99.8 wt %. The chlorination residue was dissolved in deionized water, insoluble matters in the chlorination residue were separated by a vacuum suction device, and the filtrate was evaporated to dryness at 105° C. to obtain a regenerated calcium chloride reagent.

Embodiment 3

(16) 2 g of waste lead paste (the lead content of the waste lead paste is 73.5 wt %, that is, there are 7.1×10.sup.−3 mol of lead element in 2 g of waste lead paste) was calcined at a vacuum pressure of 1 Pa and 500° C. for 10 min to decompose lead dioxide in the waste lead paste into lead oxide. In addition, elemental lead is also oxidized by lead dioxide into lead oxide. The pretreated waste lead paste is uniformly mixed with a calcium chloride/silica reagent mixture having a molar ratio of calcium chloride to lead of 30:1 and a molar ratio of silica to lead of 60:1, and then heated at a vacuum pressure of 1 Pa and 650° C. for 30 min. After heating was finished, a volatilized and condensed lead chloride product was collected on the quartz tube wall. The volatilization percentage of lead chloride was calculated by calculating lead contents in the sample before and after the reaction by the acid digestion method, and thus the volatilization percentage of lead chloride was calculated to be 99.4 wt %. The collected lead chloride product is heated at a vacuum pressure of 1 Pa and 350° C. for 10 min to obtain a secondary purified lead chloride product, and the purity of lead chloride can reach 99.8 wt %. The chlorination residue was dissolved in deionized water, insoluble matters in the chlorination residue were separated by a vacuum suction device, and the filtrate was evaporated to dryness at 105° C. to obtain a regenerated calcium chloride reagent.

Embodiment 4

(17) 2 g of waste lead paste (the lead content of the waste lead paste is 73.5 wt %, that is, there are 7.1×10.sup.−3 mol of lead element in 2 g of waste lead paste) was calcined at a vacuum pressure of 1 Pa and 500° C. for 10 min to decompose lead dioxide in the waste lead paste into lead oxide. In addition, elemental lead is also oxidized by lead dioxide into lead oxide. The pretreated waste lead paste is uniformly mixed with a calcium chloride/silica reagent mixture having a molar ratio of calcium chloride to lead of 30:1 and a molar ratio of silica to lead of 36:1, and then heated at a vacuum pressure of 1 Pa and 550° C. for 30 min. After heating was finished, a volatilized and condensed lead chloride product was collected on the quartz tube wall. The volatilization percentage of lead chloride was calculated by calculating lead contents in the sample before and after the reaction by the acid digestion method, and thus the volatilization percentage of lead chloride was calculated to be 99.7 wt %. The collected lead chloride product is heated at a vacuum pressure of 1 Pa and 350° C. for 10 min to obtain a secondary purified lead chloride product, and the purity of lead chloride can reach 99.8 wt %. The chlorination residue was dissolved in deionized water, insoluble matters in the chlorination residue were separated by a vacuum suction device, and the filtrate was evaporated to dryness at 105° C. to obtain a regenerated calcium chloride reagent.

Embodiment 5

(18) 2 g of waste lead paste (the lead content of the waste lead paste is 73.5 wt %, that is, there are 7.1×10.sup.−3 mol of lead element in 2 g of waste lead paste) was calcined at a vacuum pressure of 1 Pa and 500° C. for 10 min to decompose lead dioxide in the waste lead paste into lead oxide. In addition, elemental lead is also oxidized by lead dioxide into lead oxide. The pretreated waste lead paste is uniformly mixed with a calcium chloride/silica reagent mixture having a molar ratio of calcium chloride to lead of 12:1 and a molar ratio of silica to lead of 60:1, and then heated at a vacuum pressure of 1 Pa and 550° C. for 30 min. After heating was finished, a volatilized and condensed lead chloride product was collected on the quartz tube wall. The volatilization percentage of lead chloride was calculated by calculating lead contents in the sample before and after the reaction by the acid digestion method, and thus the volatilization percentage of lead chloride was calculated to be 93.7 wt %. The collected lead chloride product is heated at a vacuum pressure of 1 Pa and 350° C. for 10 min to obtain a secondary purified lead chloride product, and the purity of lead chloride can reach 99.8 wt %. The chlorination residue was dissolved in deionized water, insoluble matters in the chlorination residue were separated by a vacuum suction device, and the filtrate was evaporated to dryness at 105° C. to obtain a regenerated calcium chloride reagent.

Embodiment 6

(19) 2 g of waste lead paste (the lead content of the waste lead paste is 73.5 wt %, that is, there are 7.1×10.sup.−3 mol of lead element in 2 g of waste lead paste) was calcined at a vacuum pressure of 1 Pa and 500° C. for 10 min to decompose lead dioxide in the waste lead paste into lead oxide. In addition, elemental lead is also oxidized by lead dioxide into lead oxide. The pretreated waste lead paste is uniformly mixed with a calcium chloride/silica reagent mixture having a molar ratio of calcium chloride to lead of 30:1 and a molar ratio of silica to lead of 12:1, and then heated at a vacuum pressure of 1 Pa and 550° C. for 30 min. After heating was finished, a volatilized and condensed lead chloride product was collected on the quartz tube wall. The volatilization percentage of lead chloride was calculated by calculating lead contents in the sample before and after the reaction by the acid digestion method, and thus the volatilization percentage of lead chloride was calculated to be 87.2 wt %. The collected lead chloride product is heated at a vacuum pressure of 1 Pa and 350° C. for 10 min to obtain a secondary purified lead chloride product, and the purity of lead chloride can reach 99.8 wt %. The chlorination residue was dissolved in deionized water, insoluble matters in the chlorination residue were separated by a vacuum suction device, and the filtrate was evaporated to dryness at 105° C. to obtain a regenerated calcium chloride reagent.

Embodiment 7

(20) 2 g of waste lead paste (the lead content of the waste lead paste is 73.5 wt %, that is, there are 7.1×10.sup.−3 mol of lead element in 2 g of waste lead paste) was calcined at a vacuum pressure of 1 Pa and 500° C. for 10 min to decompose lead dioxide in the waste lead paste into lead oxide. In addition, elemental lead is also oxidized by lead dioxide into lead oxide. The pretreated waste lead paste is uniformly mixed with a calcium chloride/silica reagent mixture having a molar ratio of calcium chloride to lead of 30:1 and a molar ratio of silica to lead of 36:1, and then heated at a vacuum pressure of 10.sup.5 Pa and 550° C. for 30 min. After heating was finished, a volatilized and condensed lead chloride product was collected on the quartz tube wall. The volatilization percentage of lead chloride was calculated by calculating lead contents in the sample before and after the reaction by the acid digestion method, and thus the volatilization percentage of lead chloride was calculated to be 67.3 wt %. The collected lead chloride product is heated at a vacuum pressure of 1 Pa and 350° C. for 10 min to obtain a secondary purified lead chloride product. The chlorination residue was dissolved in deionized water, insoluble matters in the chlorination residue were separated by a vacuum suction device, and the filtrate was evaporated to dryness at 105° C. to obtain a regenerated calcium chloride reagent.

Embodiment 8

(21) 2 g of waste lead paste (the lead content of the waste lead paste is 73.5 wt %, that is, there are 7.1×10.sup.−3 mol of lead element in 2 g of waste lead paste) was calcined at a vacuum pressure of 1 Pa and 500° C. for 10 min to decompose lead dioxide in the waste lead paste into lead oxide. In addition, elemental lead is also oxidized by lead dioxide into lead oxide. The pretreated waste lead paste is uniformly mixed with a calcium chloride/silica reagent mixture having a molar ratio of calcium chloride to lead of 30:1 and a molar ratio of silica to lead of 36:1, and then heated at a vacuum pressure of 10.sup.3 Pa and 550° C. for 30 min. After heating was finished, a volatilized and condensed lead chloride product was collected on the quartz tube wall. The volatilization percentage of lead chloride was calculated by calculating lead contents in the sample before and after the reaction by the acid digestion method, and thus the volatilization percentage of lead chloride was calculated to be 85.7 wt %. The collected lead chloride product is heated at a vacuum pressure of 1 Pa and 350° C. for 10 min to obtain a secondary purified lead chloride product. The chlorination residue was dissolved in deionized water, insoluble matters in the chlorination residue were separated by a vacuum suction device, and the filtrate was evaporated to dryness at 105° C. to obtain a regenerated calcium chloride reagent.

Embodiment 9

(22) 2 g of waste lead paste (the lead content of the waste lead paste is 73.5 wt %, that is, there are 7.1×10.sup.−3 mol of lead element in 2 g of waste lead paste) was calcined at a vacuum pressure of 1 Pa and 500° C. for 10 min to decompose lead dioxide in the waste lead paste into lead oxide. In addition, elemental lead is also oxidized by lead dioxide into lead oxide. The pretreated waste lead paste is uniformly mixed with a calcium chloride/silica reagent mixture having a molar ratio of calcium chloride to lead of 30:1 and a molar ratio of silica to lead of 36:1, and then heated at a vacuum pressure of 10 Pa and 550° C. for 30 min. After heating was finished, a volatilized and condensed lead chloride product was collected on the quartz tube wall. The volatilization percentage of lead chloride was calculated by calculating lead contents in the sample before and after the reaction by the acid digestion method, and thus the volatilization percentage of lead chloride was calculated to be 99.6 wt %. The collected lead chloride product is heated at a vacuum pressure of 1 Pa and 350° C. for 10 min to obtain a secondary purified lead chloride product. The chlorination residue was dissolved in deionized water, insoluble matters in the chlorination residue were separated by a vacuum suction device, and the filtrate was evaporated to dryness at 105° C. to obtain a regenerated calcium chloride reagent.

(23) In the present disclosure, the chlorination volatilization reaction may be carried out by using a conventional high-temperature chlorination resistant apparatus. In the present disclosure, in addition to the preferable vacuum conditions in the above embodiments, other vacuum conditions can be adopted, as long as the vacuum pressure is much less than 1 standard atmospheric pressure (this experiment can be carried out at a vacuum pressure of 0.1 to 10.sup.5 Pa. Preferably, the vacuum pressure of the chlorination volatilization reaction is 0.1 to 10 Pa, and the vacuum pressure of the purification reaction is 0.1 to 1 Pa. The smaller the pressures, the better the effect).

(24) It should be readily understood to those skilled in the art that the above description is only preferred embodiments of the present disclosure, and does not limit the scope of the present disclosure. Any change, equivalent substitution and modification made without departing from the spirit and scope of the present disclosure should be included within the scope of the protection of the present disclosure.