CN116770415A - A short-process method for preparing lead chloride crystals using waste lead paste wet method - Google Patents

Abstract

The invention belongs to the technical field of recycling waste lead-acid batteries and preparing lead chloride crystals. It discloses a method for preparing lead chloride crystals with waste lead paste by wet method in a short process, which specifically includes the following steps: S1: Place waste lead paste in Stir and react in the carbonate solution to obtain desulfurized lead paste; S2: Use HCl-NaCl mixed solution as the leaching agent to perform a leaching reaction on the desulfurized lead paste to obtain a leachate; S3: Recrystallize to obtain lead chloride crystals. By improving the overall process design of the preparation method, the present invention first uses a carbonate solution to desulfurize the waste lead paste, then uses an HCl-NaCl mixed solution as a leaching agent to perform a leaching reaction with the desulfurized lead paste, and finally recrystallizes it. High-purity lead chloride crystals can be obtained, which effectively solves the existing technical problems of lengthy process steps, large input of reagents, and low lead chloride conversion rate.

Description

A short-process method for preparing lead chloride crystals using waste lead paste wet method

Technical field

The invention belongs to the technical field of recycling waste lead-acid batteries and preparing lead chloride crystals. More specifically, it relates to a method for preparing lead chloride crystals in a short-process wet process from waste lead paste.

Background technique

Lead chloride is one of the most important raw materials in the preparation process of lead-based perovskite solar cells and PbS quantum dot materials. With the rapid development of photovoltaic devices, PbS quantum dot optoelectronic devices have attracted much attention due to their outstanding advantages such as high efficiency, light weight, simple manufacturing process, and can be prepared into large-area flexible devices. However, they are compared with the leading crystalline silicon photovoltaic devices in the market today. Compared with other products, its production cost is still high, and low-cost, high-purity lead chloride is needed to solve the problem of expensive raw materials. The current preparation process of commercial lead chloride raw materials is to react lead carbonate, lead oxide or lead acetate with hydrochloric acid to obtain lead chloride. The process consumes a large amount of acidic reagents and energy, and the process by-products cannot be recycled and have low utilization value. On the other hand, the rapid development of lithium-ion batteries will cause certain replacements in the consumption of lead-acid batteries, resulting in a decline in lead demand. At present, the trend of "lead withdrawing and lithium advancing" is obvious. Lead consumption is affected by substitution, the consumer application market is shrinking, and the recycled lead market, with lead-acid batteries as the main product, faces challenges.

Waste lead paste is the main recycled lead raw material obtained from lead-acid batteries after crushing and screening. Its main components include PbSO ₄ , PbO ₂ , PbO, metal Pb and a small amount of Fe, Ba and other metal impurities. The current traditional pyro-smelting technology for recycling waste lead-acid batteries can easily cause the emission of acidic gases such as _SO2 . At the same time, the volatile products of lead at high temperatures are also harmful and serious pollutants to the human body. Although the wet recycling process has greatly reduced energy consumption and lead and waste gas pollution, it still has lengthy processes (often requiring desulfurization, reduction, leaching, precipitation and other steps in sequence), high energy consumption, high cost, and Problems such as serious electrolyte pollution. Therefore, if the short-process wet recovery of waste lead paste and high-purity lead chloride products can be realized, it will effectively promote the green and high-quality development of the recycled lead industry and provide a new goal for the supply direction of recycled lead.

CN201710820603. After condensation and crystallization, a crude lead chloride product is obtained. This process involves high temperature (400℃-650℃) and excessive dosage of chlorinating agent (two chlorination reagents, calcium chloride and silicon dioxide, are required, among which calcium chloride and lead are required. The molar ratio of elements is 12:1-30:1, the molar ratio of silica and lead elements is 12:1-60:1) and the product needs to be further purified and optimized (the crude lead chloride product needs to be prepared first, and then Crude product purification) and other problems, high energy and reagent consumption. CN202110909314.3 and CN201510935345.0 disclose a method for recovering lead chloride from lead waste residue. The lead-containing reagent is obtained through calcination and acid leaching, and then excess chlorine-containing reagent is added to synthesize lead chloride. The whole process includes high-temperature calcination-acid Complex processes such as immersion-chlorination synthesis have high energy consumption and difficult pollution control. CN 201911191909.9 and ^{CN201010211871 . 8} ), so excess hydrochloric acid needs to be added to the chlorine salt solution (for example, the weight ratio of lead paste to saturated sodium chloride solution is 1:13~15, the weight ratio of lead paste to 37% hydrochloric acid solution is 1:2~2.5), and cooled After crystallization and synthesis of lead chloride, there is a sulfate by-product in the crystallization filtrate, which needs to be treated with calcium chloride before it can be recycled. The accumulation of unreacted calcium ions in the filtrate in this step will affect the recycling leaching effect; and for treatment The lead dioxide in waste lead paste has a reducing agent added during the leaching process.

In summary, the existing lead chloride preparation process has the problems of high energy consumption, large reagent dosage, unstable filtrate recycling method and low lead chloride conversion rate. Regarding Fe, Ba, etc. in waste lead paste, The migration and transformation of the main impurities have not been clearly analyzed. There is an urgent need to develop a new short-flow wet process from waste lead paste to high-purity lead chloride.

Contents of the invention

In view of the above defects or improvement needs of the prior art, the purpose of the present invention is to provide a method for preparing lead chloride crystals by using waste lead paste wet method in a short process, in which the overall flow process design of the preparation method is improved, and carbon is first used. The waste lead paste is desulfurized with acid salt solution, and then the HCl-NaCl mixed solution is used as a leaching agent to perform a leaching reaction with the desulfurized lead paste. Finally, high-purity lead chloride crystals can be obtained by recrystallization, which effectively solves the existing process steps. Technical problems include lengthy process, large input of reagents and low lead chloride conversion rate. The process of the invention uses a small dosage of reagents, a high conversion rate, low impurity content, and few by-products, and realizes a short-process clean conversion from waste lead paste to high-purity lead chloride. Moreover, the solution containing chloride ions (i.e., the leaching agent) in the present invention can be 100% closed-circulated to the next leaching process of desulfurized lead paste, and the resource utilization rate is high.

In order to achieve the above object, according to the present invention, a method for preparing lead chloride crystals by wet method from waste lead paste in a short process is provided, which is characterized in that it includes the following steps:

S1: Place the waste lead paste in a carbonate solution and stir for at least 1 hour, then solid-liquid separation. The solid obtained by the solid-liquid separation is desulfurized lead paste; wherein, the carbonate ions in the carbonate solution and The molar ratio of sulfate ions in the waste lead paste is greater than or equal to 1:1;

S2: Use HCl-NaCl mixed solution as the leaching agent, place the desulfurized lead paste obtained in step S1 into the leaching agent, perform a leaching reaction at a temperature of 70°C-90°C for at least 2 hours, and then separate the solid and liquid to obtain the filtrate ; Wherein, the pH value of the leaching agent does not exceed 2.0;

S3: Recrystallize the filtrate obtained in step S2 and then perform solid-liquid separation. The solid obtained by the solid-liquid separation is lead chloride crystal.

As a further preference of the present invention, in step S3, the recrystallization specifically adopts cooling recrystallization;

Preferably, the filtrate obtained by the solid-liquid separation can be used as a leaching agent and reused in step S2;

More preferably, the temperature used for the cooling recrystallization is -20°C to -4°C.

As a further preference of the present invention, in step S2, the chloride ion concentration in the leaching agent is not less than 4.32 mol/L;

Preferably, the pH value of the leaching agent is 1.0-2.0; the chloride ion concentration in the leaching agent is 4.32mol/L-5.19mol/L; the solid-liquid ratio of the desulfurization lead paste and the leaching agent is 30g/L-40g/L; more preferably, the HCl-NaCl mixed solution is made by dropping 37-38% hydrochloric acid into the sodium chloride solution with a concentration of 250g/L-300g/L to make the pH value of the system 1.0- 2.0, obtained from this.

As a further preference of the present invention, in step S1, the carbonate ion concentration in the carbonate solution is 0.36mol/L-0.29mol/L, and the mass of the waste lead paste is equal to that of the carbonate solution. The volume ratio is 100g/L-125g/L.

As a further preference of the present invention, in step S1, the molar ratio of carbonate ions in the carbonate solution and sulfate ions in the waste lead paste is greater than or equal to 1.2:1; preferably, The molar ratio of carbonate ions in the carbonate solution and sulfate ions in the waste lead paste is 1.2:1-1.4:1;

The stirring reaction is carried out at a temperature of 35°C to 55°C; preferably, the temperature of 35°C to 55°C is provided by heating in a water bath.

As a further preference of the present invention, in step S1, the stirring speed used for the stirring reaction is 300rpm-500rpm.

As a further preference of the present invention, in step S2, the temperature condition of 70°C to 90°C is provided by water bath heating.

As a further preference of the present invention, in step S2, the leaching reaction is carried out under stirring conditions, and the stirring speed is 300rpm-500rpm.

Through the above technical solutions conceived by the present invention, compared with the existing technology, the following beneficial effects can be achieved:

(1) The present invention uses waste lead-acid battery lead paste as raw material, and proposes a short process process that can realize efficient and clean conversion from waste lead paste to high-purity lead chloride. The existing wet conversion process of waste lead paste into lead chloride generally uses the chlorine salt method for leaching, which requires a large amount of reagents, the filtrate needs to be treated before it can be recycled, and the lead chloride conversion rate is low (the lead conversion rate is about around 85%). By improving the process flow, the present invention first desulfurizes the waste lead paste and converts lead sulfate into lead carbonate that is more reactive with chlorine salt solution, which can greatly improve the lead conversion rate (i.e., recovery rate). ; Moreover, by using the HCl-NaCl mixed solution as the leaching agent and performing the leaching reaction with the desulfurized lead paste at a temperature of 70°C-90°C, especially for the difficult-to-treat + 4-valent lead (i.e., PbO ₂ ), it can be Simultaneous reduction and chlorination are achieved in HCl-NaCl solution, overcoming the technical difficulties of requiring external reducing agents such as methanol and iron powder. In addition, by using the method of the present invention, impurities such as Fe and Ba in the waste lead paste are retained in the solid phase waste residue in the intermediate step during the entire recycling process, thereby realizing the conversion of high-purity lead chloride.

Lead chloride is an important raw material for preparing PbS quantum dots. Lead chloride with a purity of more than 99.9% is usually used and is expensive. The traditional preparation method of analytically pure pharmaceuticals is to react lead carbonate, lead oxide or lead acetate with hydrochloric acid to obtain lead chloride. To prepare lead chloride through wet recovery, the waste lead paste is usually reduced by roasting or adding an oxidant, and then leached with a chlorine salt solution, followed by cooling and recrystallization to obtain lead chloride. The existing processes require the addition of a large amount of hydrochloric acid to simultaneously treat the lead sulfate in the waste lead paste, and additional reagents are added to treat the filtrate before it can be recycled. How to reduce the amount of acidic reagent added in the process, improve the conversion rate of lead chloride and Reducing the uncontrollable influence during the filtrate circulation process is a difficulty that the present invention focuses on solving.

Waste lead paste is obtained by crushing and splitting waste lead-acid batteries. Its main components include PbSO ₄ , PbO ₂ , PbO, metal Pb and a small amount of other metal impurities. Among the more difficult ingredients to deal with are lead sulfate and tetravalent lead. The present invention uses carbonate to desulfurize waste lead paste, so that the lead sulfate in the waste lead paste is converted into lead carbonate that is easy to react with acid. As for tetravalent lead, tetravalent lead needs to be reduced through high-temperature pyrolysis or the addition of reducing agents such as H ₂ O ₂ and Na ₂ SO ₃ in the existing process. In the present invention, the waste lead paste is desulfurized first, and then used to perform a chlorine salt leaching reaction to achieve simultaneous reduction chlorination (as shown in the following reaction equations (2) to (6)). By first converting lead sulfate into lead carbonate that is easier to react with hydrochloric acid, the present invention can effectively reduce the acid dosage of the entire process and improve the final yield. Moreover, in particular, cooling recrystallization can be used to recrystallize lead chloride crystals, and the reused filtrate can be used directly without processing it (that is, the solid obtained by solid-liquid separation after cooling recrystallization is high-purity chlorinated Lead crystals, the filtrate is a chloride-containing salt filtrate, which can be used again in the method of the present invention as a leaching agent to achieve recycling; specifically, the filtrate is a filtrate containing NaCl, HCl and a small amount of dissolved lead chloride, NaPbCl ₃ and Na ₂ PbCl ₄ mixed solvent, the pH value is basically the same as that of the leaching agent before the leaching reaction, no further adjustment is required, and it can be recycled for the leaching reaction; if there is a situation where the pH value of the leaching agent changes and no longer meets ≤2.0 after repeated use , you can use the originally prepared HCl-NaCl mixed solution and adjust the pH value of the leaching agent).

Taking ammonium carbonate as a desulfurization reagent as an example, the chemical reaction that occurs during the desulfurization process is shown in the following formula (1).

PbSO ₄ +(NH ₄ ) ₂ CO ₃ =(NH ₄ ) ₂ SO ₄ +PbCO ₃ (1)

The ammonium carbonate content used for desulfurization can be calculated based on the lead sulfate content in the waste lead paste. The molar ratio of carbonate ions to sulfate ions in the waste lead paste needs to be greater than or equal to 1:1. In order to ensure sufficient desulfurization, the molar ratio of carbonate ions to sulfate ions in waste lead paste can be further controlled to be greater than or equal to 1.2:1 (even if carbonate ions are excessive, since unreacted carbonate is still dissolved in the filtrate, desulfurization will not be affected) Subsequent treatment of lead paste; of course, taking into account the cost of reagents and avoiding the waste of a large amount of unreacted carbonate, in particular, the molar ratio of carbonate ions and sulfate ions can be controlled to 1.2:1-1.4:1); stirring reaction After at least 1 hour, the solid and liquid are separated. The solid is desulfurized lead paste, and the main component of the filtrate is ammonium sulfate solution, which can be recycled as a by-product.

The obtained desulfurized lead paste is leached through the HCl-NaCl mixed solution at a temperature of 70°C-90°C. The possible reactions are as shown in formulas (2) to (6). Among them, the most difficult to process in the desulfurized lead paste is dioxide. The reaction between lead and hydrochloric acid (formula (3)) is also thermodynamically feasible (as shown in Figure 3 below, △G<0, indicating that the reaction can proceed in the forward direction, and as the temperature increases, △G decreases , the reaction is more likely to proceed spontaneously), and simultaneous reductive chlorination can be achieved. By simulating and calculating the existence form of lead chloride in sodium chloride solution at different pH, as shown in Figure 4 below, when the pH is greater than 6.5, the lead component will take the form of lead hydroxide (Pb(OH) ₂ ). When the pH is greater than 4.5 and less than 6.5, the lead component will exist in the form of basic lead chloride (Pb(OH)Cl); when the pH is less than 4.5, the lead component will mainly exist in the form of PbCl ⁺ and a small amount of dissolved chlorine It exists in the form of lead chloride (lead chloride has dissolved under the temperature condition of 70℃-90℃). In the present invention, by using a small amount of hydrochloric acid solution to adjust the pH value of the leaching agent to no more than 2.0 (eg, 1.0-2.0), the lead component can be transferred to the leaching solution.

PbCO ₃ +2HCl＝PbCl ₂ +H ₂ O+CO ₂ ↑ (2)

PbO ₂ +4HCl＝PbCl ₂ +2H ₂ O+Cl ₂ ↑ (3)

PbO+2HCl=PbCl ₂ +2H ₂ O (4)

Pb+2HCl＝PbCl ₂ +H ₂ ↑ (5)

After filtration, the liquid and solid are separated. The solid is the leaching residue containing metal element impurities such as Fe and Ba; the solution is dissolved lead chloride, NaPbCl ₃ and Na ₂ PbCl ₄ complexes.

The behavior of the main impurities Fe and Ba in the leaching process was analyzed. From the simulated distribution morphology of iron elements in sodium chloride solutions of different pH (as shown in Figure 5 below), most of the iron elements are in the form of Fe ₃ O The form ₄ remains in the leaching residue, and a small amount of iron will be leached. Even if it is mixed into the product PbCl ₂ crystal during subsequent cooling and crystallization, it will have little impact on the purity of the product and will not affect the recycling of the filtrate. The impurity barium in the desulfurized lead paste is mostly BaSO ₄ and a small amount of BaCO _3. As shown in Figure 6 below, the barium element is almost not leached and all remains in the leaching residue. Therefore, the main components of the obtained solid leaching residue are BaFeO ₃ and Fe ₃ O ₄ , and the content of Fe, Ba and other metal impurities in the leach solution is greatly reduced.

In this way, high-purity lead chloride crystals can be obtained by simply recrystallizing the leachate, without the need to first obtain a solid crude product and then purify it.

(2) In particular, the present invention can use the conventional cooling recrystallization method to re-precipitate the lead chloride in the leaching filtrate in the form of crystals at the cooling temperature (such as -20°C ~ -4°C), and then undergo solid-liquid separation. The target lead chloride crystal product can be obtained. As for the filtrate obtained by solid-liquid separation, the filtrate is a mixed solvent of HCl-NaCl and incompletely precipitated dissolved lead chloride, which can be recycled for hot leaching recrystallization of desulfurized lead paste. There is almost no solvent consumption and will be used in the next step. Improve the lead chloride production rate in the cycle.

(3) Using the method of the present invention, before the leaching reaction, the chloride ion concentration in the leaching agent can preferably be at least 4.32 mol/L; taking into account the cost of the reagent and avoiding the waste of a large amount of unreacted Cl ions, the HCl-NaCl mixed solution can be The concentration of chlorine ions is controlled to be 4.32mol/L-5.19mol/L (of course, even if there are unreacted Cl ions, waste can be avoided if the leaching agent is recycled). In actual operation, the present invention can add 37-38% hydrochloric acid dropwise to a sodium chloride solution with a concentration of 250g/L-300g/L to make the pH value of the system 1.0-2.0, thereby obtaining a HCl-NaCl mixed solution as a leaching solution. agent; unlike the prior art that directly adds excess hydrochloric acid to a saturated sodium chloride solution for leaching, the present invention reduces the concentration of the sodium chloride solution and can achieve optimal results by integrating lead conversion rate and reagent cost.

(4) The existing wet process currently involves leaching waste lead paste directly and then cooling and crystallizing it to obtain lead chloride. Calcium chloride needs to be added to the crystallization filtrate to treat the sulfate radicals in the filtrate, and the filtrate can be recycled again after the sulfate radical removal treatment. There is a problem with the dosage of calcium chloride. If less is added, sulfate ions cannot be completely absorbed; if too much is added, calcium ions will accumulate in the filtrate, affecting the leaching effect of subsequent cycles. This process is cumbersome, which will increase the operational difficulty and uncertainty of the operational effects during actual large-scale production. However, in the present invention, the waste lead paste is not directly leached, but desulfurization treatment is performed first, which can achieve at least two effects: (1) Reduce the amount of hydrochloric acid added. Lead sulfate is difficult to be leached by chlorination, requiring a large amount of hydrochloric acid and a longer leaching time. The desulfurization process converts lead sulfate into lead carbonate that is easier to chloride, which can greatly reduce the amount of acidic reagents and effectively reduce costs; (2 ) desulfurizes the sulfate radicals in advance, so there is no need to further process the crystallization filtrate, which can be directly used in the next cycle and ensures that the cycle leaching effect remains unchanged.

By adding desulfurization pretreatment to the process of preparing lead chloride from existing waste lead paste, the present invention realizes the transformation of lead sulfate into lead carbonate and obtains recoverable sulfate by-products, which not only avoids the need to add additional reagents to treat the circulating filtrate, but also This leads to the problem of introducing other impurities into the entire process, and reduces the acid dosage of the entire process. The dosage of hydrochloric acid in the method of the present invention can be only 3.8mL/L-5.6mL/L (that is, every liter of HCl -NaCl mixed solution, you can only use 3.8mL-5.6mL concentrated hydrochloric acid with a concentration of 37-38% to adjust the pH value to no more than 2.0; of course, you can also use a high-concentration NaCl solution with a low-concentration HCl solution to prepare HCl -NaCl mixed solution, as long as the pH value meets the requirements). The overall process does not use high temperature, high pressure, high energy consumption and other process conditions, and there is no discharge of lead-containing solution or solid waste, which controls economic consumption and environmental impact to the lowest level. The total lead yield of the present invention can reach 97%, and the short-process wet method can be used to prepare lead chloride crystals with a purity of up to 99.99%, and metal impurities such as Fe and Ba do not exceed 10 ppm.

(4) There are only three reagent emissions in the entire process of the present invention. The sulfate solution generated during the desulfurization process can be recycled as a by-product, while the waste residue generated during the recrystallization process of the HCl-NaCl mixed solvent is mainly waste lead paste. of Fe, Ba and Cu impurities, and the filtrate is recycled as a leaching solvent. The chlorine waste gas produced during the leaching reaction is very small. Taking the _PbO2 content in waste lead paste as an example of 17.93wt%, the amount of chlorine gas produced per kilogram of waste lead paste processed is only 0.74 mol. The process discharges less pollutants and the overall environmental pollution is small.

(5) The present invention only uses three chemical reagents: carbonate solution, sodium chloride solution, and hydrochloric acid. In the desulfurization and chlorination processes, carbonate and sodium chloride are used as desulfurization agents and chlorine sources respectively; the amount of hydrochloric acid added Only 3.8mL/L-5.6mL/L; after the chloride salt solution is recrystallized and filtered, the lead in the filtrate exists in the form of dissolved lead chloride, PbCl ₃ ^- and PbCl ₄ ^2- , which can be directly used in the next batch Thermal leaching of desulfurized lead paste will not only not affect the purity of the next batch of products, but also improve the yield of the next batch of products.

(6) The reaction conditions of each step of the present invention are mild and the reaction efficiency is high. The reaction time of desulfurization reaction can be as low as 1 hour, and the reaction time of leaching reaction can be as low as 2 hours, which is short and time-consuming, greatly increasing production efficiency. The reaction process does not use reaction conditions such as high temperature, high pressure, and high-speed stirring. The maximum reaction temperature does not exceed 90°C, and the process is simple and controllable.

(7) The present invention can especially directly obtain high-purity lead chloride crystals with metal impurities such as Fe and Ba below 10 ppm. Similar to the recrystallization process control known in the prior art, the crystal size can be controlled by controlling the recrystallization process conditions. (Take cooling recrystallization as an example. The crystal size of cooling crystallization is mainly affected by the cooling rate and crystallization temperature. The crystal size obtained under rapid cooling conditions is small, and the crystal size obtained under slow cooling conditions is large; the crystal size obtained under higher crystallization temperature The crystal size is large and the crystal size obtained by the low crystallization temperature is small), which is beneficial to subsequent use. The lead chloride yield during the process can especially exceed 90% (for example, up to 95%), and 5%-10% of the uncrystallized lead-containing components remain in the crystallization filtrate and can enter the next round of reaction.

Description of drawings

Figure 1 is a process flow chart for preparing lead chloride crystals using a short wet process from waste lead paste in the present invention.

Figure 2 is the XRD pattern of the desulfurized lead paste and waste lead paste raw materials obtained in the process of Example 1.

Figure 3 shows the reaction thermodynamic parameters during the reaction between HCl and lead dioxide.

Figure 4 shows the distribution form of lead-containing components under different pH conditions (the concentration of lead chloride in the solution is 0.01mol/L, the concentration of sodium chloride is 0.1mol/L, and the set reaction temperature is 25℃).

Figure 5 shows the distribution form of impurity iron under different pH conditions (the concentration of iron ions in the solution is 0.01mol/L, the concentration of sodium chloride is 0.1mol/L, and the set reaction temperature is 25°C).

Figure 6 is the E-pH phase diagram of the impurity barium (the concentration of barium ions in the solution is 3mol/kg, the concentration of carbonate ions is 1mol/kg, the concentration of sulfate ions is 2mol/kg, and the concentration of chloride ions is 1mol/kg, and assume The reaction temperature is set at 25°C).

Figure 7 is the XRD pattern of the leached impurities obtained during Example 1.

Figure 8 is an XRD pattern of the high-purity lead chloride crystal obtained in the process of Example 1.

Figure 9 is an SEM pattern of the high-purity lead chloride crystal obtained in the process of Example 1.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

The following are specific embodiments, and each embodiment satisfies the process flow chart shown in Figure 1.

In addition, the waste lead paste used in each embodiment comes from the same batch and is obtained by crushing and splitting waste lead-acid batteries using methods known in the art. The actual content of lead element in the waste lead paste was measured by chemical titration method to be 72.79wt%, the content of lead sulfate in the waste lead paste was 72.45wt%, the content of lead dioxide was 17.93wt%, the impurity content of the waste lead paste was The test results are as follows:

Fe: 125.3ppm; Ba: 111.2ppm; Cu: 9.19ppm; Zn: 4.90ppm; Al: 1.74ppm.

Example 1

(1) Take 5g of waste lead paste and place it in 50mL of ammonium carbonate solution with a concentration of 30g/L. The solid-liquid ratio is 100g/L. Stir the reaction at 35°C for 1 hour, filter and separate, and dry the solid in an oven at 60°C for 3 hours to obtain a desulfurized lead paste with a mass of 4.42g. The filtrate obtained by filtration in this step is the sulfate filtrate.

(2) Add a small amount of hydrochloric acid with a volume fraction of 37%-38% to 111 mL of sodium chloride solution with a concentration of 250g/L to prepare a NaCl-HCl solution until the pH of the solution does not exceed 2.0. The hydrochloric acid added dropwise in this example is The volume is 600 μL and the final pH of the solution is 1.08. Place the desulfurized lead paste obtained in the previous step into 111 mL of NaCl-HCl solution, with a solid-liquid ratio of 40 g/L. Stir and leaching at a water bath heating temperature of 80°C for 2h-3h, then perform solid-liquid separation by suction filtration while hot to obtain 113 mL of leachate. The solid residue obtained by solid-liquid separation in this step is the solid leaching residue containing metal element impurities such as Fe and Ba (metal impurities such as Fe and Ba mainly remain in the residue in the form of solid phase); the filtrate is chlorinated in a dissolved state Lead-based leachate.

(3) Recrystallize the leach solution at -4°C for 4 hours, perform solid-liquid separation by suction filtration, and dry the obtained solid in an oven at 60°C for 2 hours to obtain lead chloride crystals. The product mass is 4.67g. Detect the chlorine in the product. The purity of lead is 99.99%. Calculating the total lead yield shows that the total lead yield is 95.58%.

The total lead yield is calculated by first using chemical titration to test the actual lead content in the waste lead paste, and then using the actual lead chloride yield, purity, and the mass percentage of lead element in lead chloride. The formula is as follows (Subsequent embodiments are also similar):

In the formula: m _{lead chloride} is the mass of lead chloride finally obtained in the experiment (unit: g); w ₁ is the lead content of lead chloride finally obtained in the experiment (unit: %); m _{waste lead paste} is the waste lead used as the raw material in the experiment The mass of the paste (unit: g); w ₁ is the lead content of the raw material waste lead paste (unit: %).

The XRD patterns of the desulfurized lead paste and waste lead paste raw materials before and after the treatment in step (1) are shown in Figure 2. It can be seen that after the treatment in step (1), all lead sulfate is converted into lead carbonate, and the desulfurization lead paste also contains A small amount of lead dioxide remains.

The solid leaching residue obtained by solid-liquid separation in step (2) is shown in Figure 7. The main components are BaFeO ₃ and Fe ₃ O ₄ .

The solid product of step (3) is lead chloride crystals, as shown in Figures 8 and 9. The crystals do not contain other components and are needle-shaped.

Example 2

(1) Take 5g of waste lead paste and place it in 50mL of ammonium carbonate solution with a concentration of 32g/L. The solid-liquid ratio is 100g/L. Stir the reaction at 45°C for 1 hour, filter and separate, and dry the solid in an oven at 60°C for 3 hours to obtain a desulfurized lead paste with a mass of 4.41g.

(2) Add a small amount of hydrochloric acid with a volume fraction of 37%-38% to 134 mL of sodium chloride solution with a concentration of 300 g/L to prepare a NaCl-HCl solution until the pH of the solution does not exceed 2.0. The hydrochloric acid added dropwise in this example is The volume is 750 μL and the final pH of the solution is 1.01. Place the desulfurized lead paste obtained in the previous step into 134 mL of NaCl-HCl solution, with a solid-liquid ratio of 33 g/L. Stir and leach at a water bath heating temperature of 80°C for 2h-3h, then perform solid-liquid separation by suction filtration to obtain 137 mL of leachate.

(3) Recrystallize the leach solution at -4°C for 4 hours, perform solid-liquid separation by suction filtration, and dry the obtained solid in an oven at 60°C for 2 hours to obtain lead chloride crystals. The product mass is 4.51g. Check the chlorine in the product. The purity of lead reached 99.99%, and the total lead yield was 92.31%.

Example 3

(1) Take 5g of waste lead paste and place it in 40mL of ammonium carbonate solution with a concentration of 37g/L. The solid-liquid ratio is 125g/L. Stir the reaction at 55°C for 1 hour, filter and separate, and dry the solid in an oven at 60°C for 3 hours to obtain 4.45g of desulfurized lead paste.

(2) Add a small amount of hydrochloric acid with a volume fraction of 37%-38% to 127 mL of sodium chloride solution with a concentration of 260 g/L to prepare a NaCl-HCl solution until the pH of the solution does not exceed 2.0. The hydrochloric acid added dropwise in this example is The volume was 490 μL and the final pH of the solution was 1.77. Place the desulfurized lead paste obtained in the previous step into 127 mL of NaCl-HCl solution, with a solid-liquid ratio of 35 g/L. Stir and leach at a water bath heating temperature of 80°C for 2h-3h, then perform solid-liquid separation by suction filtration to obtain 129 mL of leachate.

(3) Recrystallize the leach solution at -4°C for 4 hours, perform solid-liquid separation by suction filtration, and dry the obtained solid in an oven at 60°C for 2 hours to obtain lead chloride crystals. The product mass is 4.58g. Check the chlorine in the product. The purity of lead chemical reached 99.99%, and the total lead yield was 93.74%.

Example 4

(1) Take 5g of waste lead paste and place it in 50mL of ammonium carbonate solution with a concentration of 27g/L. The solid-liquid ratio is 100g/L. Stir the reaction at 55°C for 1 hour, filter and separate, and dry the solid in an oven at 60°C for 3 hours to obtain 4.44g of desulfurized lead paste.

(2) Add a small amount of hydrochloric acid with a volume fraction of 37%-38% to 120 mL of sodium chloride solution with a concentration of 270 g/L to prepare a NaCl-HCl solution until the pH of the solution does not exceed 2.0. The hydrochloric acid added dropwise in this example The volume was 608 μL and the final pH of the solution was 1.26. Place the desulfurized lead paste obtained in the previous step into 120 mL of NaCl-HCl solution, with a solid-liquid ratio of 37 g/L. Stir and leach at a water bath heating temperature of 80°C for 2h-3h, then perform solid-liquid separation by suction filtration to obtain 123 mL of leachate.

(3) Recrystallize the leach solution at -4°C for 4 hours, perform solid-liquid separation by suction filtration, and dry the obtained solid in an oven at 60°C for 2 hours to obtain lead chloride crystals. The product mass is 4.65g. Detect the chlorine in the product. The purity of lead reached 99.99%, and the total lead yield was 95.17%.

Example 5

(1) Take 5g of waste lead paste and place it in 40mL of ammonium carbonate solution with a concentration of 40g/L. The solid-liquid ratio is 125g/L. Stir the reaction at 35°C for 1 hour, filter and separate, and dry the solid in an oven at 60°C for 3 hours to obtain a desulfurized lead paste with a mass of 4.39g.

(2) Add a small amount of hydrochloric acid with a volume fraction of 37%-38% to 146 mL of sodium chloride solution with a concentration of 280 g/L to prepare a NaCl-HCl solution until the pH of the solution does not exceed 2.0. The hydrochloric acid added dropwise in this example is The volume was 792 μL and the final pH of the solution was 1.13. Place the desulfurized lead paste obtained in the previous step into 146 mL of NaCl-HCl solution, with a solid-liquid ratio of 30 g/L. Stir and leach at a water bath heating temperature of 80°C for 2h-3h, then perform solid-liquid separation by suction filtration to obtain 147 mL of leachate.

(3) Recrystallize the leachate at -20°C for 4 hours, perform solid-liquid separation by suction filtration, and dry the obtained solid in an oven at 60°C for 2 hours to obtain lead chloride crystals. The product mass is 4.49g. Check the chlorine in the product. The purity of lead is 99.99%, and the total lead yield is 91.90%.

Example 6

(1) Take 5g of waste lead paste and place it in 55mL of ammonium carbonate solution with a concentration of 20g/L. The solid-liquid ratio is 90g/L. Stir the reaction at 45°C for 1 hour, filter and separate, and dry the solid in an oven at 60°C for 3 hours to obtain a desulfurized lead paste with a mass of 4.91g (carbonate ions in the carbonate solution and sulfate ions in the waste lead paste) The molar ratio between the two is 1:1, desulfurization is incomplete, and the sulfur content is 0.25%).

(2) Add a small amount of hydrochloric acid with a volume fraction of 37%-38% to 111mL of sodium chloride solution with a concentration of 250g/L to prepare a NaCl-HCl solution until the pH of the solution is in the range of 1.0-2.0. The volume is 600 μL and the final pH of the solution is 1.08. Place the desulfurized lead paste obtained in the previous step into 111 mL of NaCl-HCl solution, with a solid-liquid ratio of 40 g/L. Stir and leached at a water bath heating temperature of 80°C for 2h-3h, then perform solid-liquid separation by suction filtration to obtain 113 mL of leachate.

(3) Recrystallize the leach solution at -4°C for 4 hours, perform solid-liquid separation by suction filtration, and dry the obtained solid in an oven at 60°C for 2 hours to obtain lead chloride crystals. The product mass is 4.33g. Detect the chlorine in the product. The purity of lead reached 99.74%, and the total lead yield was 88.40%.

Example 7

(1) Take 5g of waste lead paste and place it in 40mL of ammonium carbonate solution with a concentration of 37g/L. The solid-liquid ratio is 125g/L. Stir the reaction at 45°C for 1 hour, filter and separate, and dry the solid in an oven at 60°C for 3 hours to obtain a desulfurized lead paste with a mass of 4.45g.

(2) Add a small amount of hydrochloric acid with a volume fraction of 37%-38% to 100mL of sodium chloride solution with a concentration of 200g/L (chloride ion concentration is 3.44mol/L) to prepare a NaCl-HCl solution until the pH of the solution is between 1.0- Within the range of 2.0, the volume of hydrochloric acid added dropwise is 400 μL, and the final pH of the solution is 1.42. Place the desulfurized lead paste obtained in the previous step into 100 mL of NaCl-HCl solution, with a solid-liquid ratio of 45 g/L. Stir and leached at a water bath heating temperature of 80°C for 2h-3h, then perform solid-liquid separation by suction filtration to obtain 103 mL of leachate.

(3) Recrystallize the leachate at -4°C for 4 hours, perform solid-liquid separation by suction filtration, and dry the obtained solid in an oven at 60°C for 2 hours to obtain lead chloride crystals. The product mass is 4.01g. Detect the chlorine in the product. The purity of lead reached 99.99%, and the total lead yield was 82.08%.

Table 1 Comparison table of parameter conditions, total lead yield, and product purity results in Examples 1-7

The lead chloride purity of the products obtained in the above examples is as high as 99% or more, especially the products obtained in Examples 1-5 and 7, the purity is as high as 99.99%, and metal impurities such as Fe and Ba do not exceed 10ppm (0.01% purity corresponds to (with an impurity content of 10 ppm), they have the characteristics of a short process, and high-purity products are obtained directly (without the need for further purification of the crude product).

Moreover, it can be seen from Table 1 that in order to obtain a higher total lead conversion rate (such as a total lead conversion rate of ≥90%), in the desulfurization step of the preparation method of the present invention, the carbonate ions and carbonate ions in the carbonate solution can be particularly controlled. The molar ratio of sulfate ions in the waste lead paste is greater than or equal to 1.2:1; and in the leaching step, the leaching agent can especially contain an excess concentration of chloride ions (for example, the chloride ion concentration in the leaching agent can be controlled to be no less than 4.32 mol/L).

Example 8

The filtrate obtained by solid-liquid separation in step (3) of Example 1 is used as the leachate, and the method of the present invention is recycled. Specifically:

(1) Take 5g of waste lead paste and place it in 50mL of ammonium carbonate solution with a concentration of 30g/L. The solid-liquid ratio is 100g/L. Stir the reaction at 35°C for 1 hour, filter and separate, and dry the solid in an oven at 60°C for 3 hours to obtain a desulfurized lead paste with a mass of 4.42g.

(2) Place the desulfurized lead paste obtained in the previous step into 113 mL of filtrate (pH=1.38) obtained by solid-liquid separation in step (3) of Example 1, stir and leaching at a water bath heating temperature of 80°C for 2h-3h, and pump Filtrate for solid-liquid separation to obtain 113 mL of leachate.

(3) Recrystallize the leach solution at -4°C for 4 hours, perform solid-liquid separation by suction filtration, and dry the obtained solid in an oven at 60°C for 2 hours to obtain lead chloride crystals. The product mass is 4.77g. The chlorine in the product is detected. The purity of lead is 99.99%, and the total lead yield is 97.63%.

Comparative example 1

(1) Take 5g of waste lead paste and place it in 40mL of ammonium carbonate solution with a concentration of 37g/L. The solid-liquid ratio is 125g/L. Stir the reaction at 45°C for 1 hour, filter and separate, and dry the solid in an oven at 60°C for 3 hours to obtain a desulfurized lead paste with a mass of 4.45g.

(2) Add a small amount of hydrochloric acid with a volume fraction of 37%-38% to 111 mL of sodium chloride solution with a concentration of 250 g/L to prepare a NaCl-HCl solution. The volume of hydrochloric acid added dropwise is 50 μL, and the final pH of the solution is 3.47. Place the desulfurized lead paste obtained in the previous step into 111 mL of NaCl-HCl solution, with a solid-liquid ratio of 40 g/L. Stir and leached at a water bath heating temperature of 80°C for 2h-3h, then perform solid-liquid separation by suction filtration to obtain 113 mL of leachate.

(3) Recrystallize the leach solution at -4°C for 4 hours, perform solid-liquid separation by suction filtration, and dry the obtained solid in an oven at 60°C for 2 hours to obtain lead chloride crystals. The product mass is 3.26g. The chlorine in the product is detected. The purity of lead reached 99.99%, and the total lead yield was 66.73%.

The above embodiments are only examples. For example, in addition to ammonium carbonate, other soluble carbonates (such as sodium carbonate, potassium carbonate, ammonium bicarbonate) can also be used, all of which can achieve similar effects. The amount of carbonate solution is specifically determined by the lead sulfate content in the waste lead paste (for example, when the concentration of the carbonate solution is fixed, the higher the lead sulfate content in the waste lead paste, the greater the volume of carbonate solution. big).

It is easy for those skilled in the art to understand that the above descriptions are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements, etc., made within the spirit and principles of the present invention, All should be included in the protection scope of the present invention.

Claims (8)

1. A short-process method for preparing lead chloride crystals by wet method from waste lead paste, which is characterized in that it includes the following steps: S1: Place the waste lead paste in a carbonate solution and stir for at least 1 hour, then solid-liquid separation. The solid obtained by the solid-liquid separation is desulfurized lead paste; wherein, the carbonate ions in the carbonate solution and The molar ratio of sulfate ions in the waste lead paste is greater than or equal to 1:1; S2: Use HCl-NaCl mixed solution as the leaching agent, place the desulfurized lead paste obtained in step S1 into the leaching agent, perform a leaching reaction at a temperature of 70°C-90°C for at least 2 hours, and then separate the solid and liquid to obtain the filtrate ; Wherein, the pH value of the leaching agent does not exceed 2.0; S3: Recrystallize the filtrate obtained in step S2 and then perform solid-liquid separation. The solid obtained by the solid-liquid separation is lead chloride crystal. 2. The method for preparing lead chloride crystals by the wet short-process method of waste lead paste as claimed in claim 1, characterized in that in the step S3, the recrystallization specifically adopts cooling recrystallization; Preferably, the filtrate obtained by the solid-liquid separation can be used as a leaching agent and reused in step S2; More preferably, the temperature used for the cooling recrystallization is -20°C to -4°C. 3. The method for preparing lead chloride crystals by wet short process from waste lead paste as claimed in claim 1, characterized in that in step S2, the chloride ion concentration in the leaching agent is not less than 4.32mol/L; Preferably, the pH value of the leaching agent is 1.0-2.0; the chloride ion concentration in the leaching agent is 4.32mol/L-5.19mol/L; the solid-liquid ratio of the desulfurization lead paste and the leaching agent is 30g/L-40g/L; more preferably, the HCl-NaCl mixed solution is made by dropping 37-38% hydrochloric acid into the sodium chloride solution with a concentration of 250g/L-300g/L to make the pH value of the system 1.0- 2.0, obtained from this. 4. The method for preparing lead chloride crystals by wet short process of waste lead paste as claimed in claim 1, characterized in that, in the step S1, the carbonate ion concentration in the carbonate solution is 0.36mol/L- 0.29 mol/L, and the ratio of the mass of the waste lead paste to the volume of the carbonate solution is 100g/L-125g/L. 5. The method for preparing lead chloride crystals by wet short process of waste lead paste as claimed in claim 1, characterized in that, in the step S1, the carbonate ions in the carbonate solution and the waste lead paste are The molar ratio of the sulfate ions in the carbonate solution is greater than or equal to 1.2:1; preferably, the molar ratio of the carbonate ions in the carbonate solution to the sulfate ions in the waste lead paste is 1.2:1 -1.4:1; The stirring reaction is carried out at a temperature of 35°C to 55°C; preferably, the temperature of 35°C to 55°C is provided by heating in a water bath. 6. The short-process method for preparing lead chloride crystals from waste lead paste by wet method as claimed in claim 1, characterized in that in step S1, the stirring speed used for the stirring reaction is 300rpm-500rpm. 7. The short-process method for preparing lead chloride crystals by wet method from waste lead paste as claimed in claim 1, characterized in that in step S2, the temperature condition of 70°C to 90°C is provided by water bath heating. 8. The method for preparing lead chloride crystals by wet short process of waste lead paste as claimed in claim 1, characterized in that, in the step S2, the leaching reaction is carried out under stirring conditions, and the stirring speed is 300rpm- 500rpm.