A method for leaching and preparing hydrocerussite from steel metallurgical dust water washed slag

Abstract

This invention belongs to the field of solid waste recycling, specifically relating to a method for leaching and preparing hydroxyl chloride lead ore from steel metallurgical dust washing slag. The method involves leaching hydroxyl chloride lead ore-containing steel metallurgical dust washing slag in a composite leaching solution, converting the hydroxyl chloride lead ore into water-soluble PbCl. x y‑ The complex was then subjected to solid-liquid separation to obtain PbCl-rich material. x y‑ Leachate and iron slag of the complex; PbCl x y‑ In the above, x is 3 or 4, and y is 1 or 2; the composite leachate is an aqueous solution containing dissolved acid and auxiliaries; the acid is at least one of hydrochloric acid and acetic acid; the auxiliaries are water-soluble salts of at least one cation selected from Na, K, Ca, and Fe; an alkaline precipitant is added to the leachate to remove PbCl... x y‑ The complex is conditioned and precipitated, with the pH of the system during the conditioning and precipitation process being 6-10; subsequently, solid-liquid separation is performed to obtain lead chloride ore. This invention can selectively remove lead enriched in steel metallurgical dust washing slag, reducing its harm to the steel smelting process after return to sintering; at the same time, it realizes the resource recovery of lead.

Description

Technical Field

[0001] This invention pertains to solid waste treatment methods, specifically to the recovery of lead from lead-containing iron and steel metallurgical dust. Background Technology

[0002] Iron and steel metallurgical solid waste is typically characterized by large volume and complex composition. Taking sintering machine head ash from iron and steel metallurgical dust as an example, the annual output of sintering machine head ash in China usually exceeds 15 million tons. This type of dust contains large amounts of iron, alkali metals (potassium, sodium), lead, and chloride. Since most of the alkali metals are present in the form of chloride salts, most domestic iron and steel enterprises treat the sintering dust by water leaching to obtain iron-rich sintering dust wash slag. This wash slag is then returned to the sintering process. However, a simple water washing process cannot remove lead from the sintering dust and may even lead to lead enrichment. The lead content in the wash slag is usually 2-3 times higher than before washing. Since lead increases the lead load in blast furnace smelting, it causes fluctuations in blast furnace conditions and production instability. The national standard GB / T36144—2018 requires that the lead content in iron ore used for iron and steel smelting must be ≤0.60wt%. Therefore, the lead removal issue needs to be considered before the wash slag from the sintering machine head ash is returned to the sintering process. If selective removal of Pb can be achieved, it is expected that the iron grade of the washed slag can be increased by nearly 10%, and the recovered lead products can also generate economic benefits for steel companies.

[0003] The lead in sintering machine head ash mainly originates from lead-containing minerals such as galena, which are associated with the iron-containing raw materials in the sintering batch. During sintering, galena in the raw materials is first oxidized in the low-temperature preheating zone to form lead sulfate; after entering the high-temperature combustion zone, lead compounds generate metallic lead vapor or decompose into gaseous lead oxide under high temperature and local reducing atmosphere. The gaseous lead oxide also reacts with chloride salts in the raw materials to form lead chloride, which has a low boiling point and is highly volatile. Various gaseous lead compounds migrate upward with the sintering flue gas, rapidly condense into fine particles in the low-temperature environment of the flue and dust removal system, and are adsorbed and enriched by iron oxide dust and potassium chloride condensate crystals in the flue gas, ultimately ending up in the sintering machine head ash. Therefore, the lead in the sintering machine head ash mostly exists in the form of lead chloride, lead oxide, and basic lead chloride. After washing with water, some lead may react with SO4 in the washing solution. 2- and OH - This process combines to form potassium lead sulfate, lead sulfate, and hydroxyl chloride. Hydroxyl chloride is almost insoluble in water and alkaline solutions, and in acidic solutions it transforms into lead chloride and other poorly soluble substances. Therefore, there is currently a lack of effective methods for leaching hydroxyl chloride from dust.

[0004] Existing technologies report several methods for extracting lead from sintering machine head ash and washing residue. For example, patent document CN112609083A discloses a method for enriching lead in sintering electrostatic precipitator ash. Specifically, it describes a method for recovering tailings from sintering dust washing residue using magnetic separation, then washing the tailings with a sodium acetate and acetic acid solution to obtain filter residue, and finally calcining the filter residue to prepare lead monoxide powder with a grade exceeding 15%. Patent document CN104843772A discloses a method for recovering lead chloride from sintering ash using acetic acid leaching and preparing lead monoxide. It discloses a method for recovering iron concentrate from sintering dust leaching residue through gravity separation-magnetic separation, chlorinating the magnetic separation tailings, leaching the lead with acetic acid, and then preparing lead oxide products through chemical precipitation and high-temperature roasting.

[0005] Although these methods can separate and recover lead from the slag leaching residue in the sintering machine head, they suffer from problems such as long process time and poor product purity. Summary of the Invention

[0006] To address the problems of ineffective lead removal and lengthy comprehensive treatment processes in existing lead-containing steelmaking dust washing slag, this invention aims to provide a method for leaching lead from steelmaking dust washing slag. This method selectively decomposes and dissolves hydroxyl lead chloride ore in the slag, selectively coordinates and leaches it, and then conditions and precipitates it to recover high-quality hydroxyl lead chloride ore. The main challenge in efficiently removing lead from lead-containing steelmaking dust washing slag and recovering high-quality lead products stems from the complex embedding morphology of lead in the washing slag. Lead mainly exists in the form of hydroxyl lead chloride ore, whose chemical properties make it difficult for Pb to dissolve effectively in conventional acid / alkali leaching solutions. Residual Cl in steelmaking... - CO3 2- SO4 2- The acid radical ions will dissolve the Pb 2+ The lead is re-fixed in the slag. Furthermore, other impurities in the sintering dust and water-leached slag also affect lead recovery, leading to a lengthy lead recovery process and low-grade lead products. To address these problems, this invention, after in-depth research, provides the following improvements:

[0007] A method for leaching and preparing lead chloride ore from steel metallurgical dust washing slag, comprising the following steps:

[0008] Step 1:

[0009] The leaching treatment of steel metallurgical dust and washing slag containing hydroxyl chloride lead ore (also known as steel metallurgical dust or washing slag) in a composite leaching solution converts the hydroxyl chloride lead ore into water-soluble PbCl. x y- The complex was then subjected to solid-liquid separation to obtain PbCl-rich material. x y- Leachate and iron slag of the complex; PbClx y- In the equation, x is 3 or 4, and y is 1 or 2;

[0010] The composite leachate is an aqueous solution containing dissolved acid and auxiliaries; the acid is at least one of hydrochloric acid and acetic acid; the auxiliaries are water-soluble salts of at least one cation selected from Na, K, Ca, and Fe; the concentration of the acid is above 0.04 mol / L; and the concentration of the auxiliaries is above 300 g / L.

[0011] Step 2:

[0012] Add an alkaline precipitant to the leachate to remove PbCl. x y- The complex was selectively conditioned and precipitated, with the pH of the system during the conditioning and precipitation process being 6-10; subsequently, solid-liquid separation was performed to obtain hydroxychlorolead ore.

[0013] For lead-containing solid waste, existing technologies mostly recover the lead as slag (such as PbCl2 and PbSO4) and volatilize it at high temperatures, or convert the solid slag (such as PbCl2 and PbSO4) into lead chloride ore through solid-solid conversion. These methods suffer from unsatisfactory energy consumption and selectivity in lead recovery. To address this problem, and to solve the difficulties in selectively converting and leaching lead chloride ore from iron and steel metallurgical dust, as well as the unsatisfactory selectivity of lead and iron leaching, this invention innovatively employs the aforementioned composite leaching solution for leaching, combined with the joint control of the leaching system and concentration. This allows for the selective conversion of lead chloride ore into water-soluble PbCl2. x y- Complex, then PbCl x y- Conditioning and precipitation of the complex, along with pH control of the precipitation, allows for highly selective precipitation of PbCl₂. x y- The complex precipitates to form high-quality hydroxyl chloride lead ore. This invention enables the selective leaching and precipitation of hydroxyl chloride lead ore in the slag, yielding high-quality hydroxyl chloride lead ore. Furthermore, the composite leaching solution described in this invention does not require secondary concentration adjustment and can be directly recycled.

[0014] In this invention, the lead content in the steel metallurgical dust washing slag is 2wt%~20wt%, and more preferably 8~12wt%.

[0015] Preferably, in the steel metallurgical dust washing slag, the lead in the hydroxyl chloride lead ore accounts for more than 60 wt% of the total lead weight, preferably 60 wt% to 80 wt%.

[0016] In this invention, the iron content in the water-washed slag of iron and steel metallurgical dust is 30wt%~50wt%, and can be further 42wt%~47wt%; the iron-bearing phases include hematite and magnetite, wherein the content of magnetite is 50wt%~60wt% of the iron phase;

[0017] And / or, the washing slag of iron and steel metallurgical dust also contains calcium, chlorine, sulfur and fluorine; wherein the content of calcium is 3wt% to 10wt% (moreover, 4 to 6wt%); the content of chlorine is 0.5wt% to 5wt% (moreover, 1 to 2wt%); the content of sulfur is 0.5wt% to 2wt% (moreover, 0.6 to 0.9wt%); the content of fluorine is 2wt% to 7wt% (moreover, 3 to 5wt%); and the content of carbon is 1wt% to 5wt% (moreover, 2 to 3wt%); the calcium-bearing phases include fluorite and dolomite, wherein the content of fluorite is 50wt% to 80wt% of the calcium phase.

[0018] In this invention, the acid in the composite leachate is hydrochloric acid; the auxiliary agent is calcium chloride.

[0019] Studies have shown that this preferred composite leaching solution can further facilitate the selective conversion and leaching of lead chloride ore in steel metallurgical dust washing slag, improving its leaching rate and leaching selectivity.

[0020] In this invention, the concentration of acid in the composite leaching solution is 0.06 mol / L to 0.15 mol / L; the concentration of the auxiliary agent is 320 g / L to 500 g / L; preferably, the concentration of acid is 0.08 mol / L to 0.12 mol / L; and the concentration of the auxiliary agent is 350 g / L to 400 g / L. The preferred composite leaching solution can further improve the leaching efficiency and effect of lead chloride ore.

[0021] In this invention, in step 1, the leaching temperature is 20 ℃~90 ℃, preferably 20 ℃~30 ℃;

[0022] The leaching time is 5 min to 90 min, preferably 10 min to 20 min;

[0023] The liquid-to-solid ratio of the leaching solution is 1 mL / g to 10 mL / g.

[0024] In this invention, in step 2, the alkaline precipitant is at least one of the oxides and hydroxides of the cations involved in the additives.

[0025] In this invention, in step 2, the alkaline precipitant comprises at least one of calcium oxide, calcium hydroxide, sodium hydroxide, and potassium hydroxide; preferably, at least one of calcium oxide and calcium hydroxide. The preferred alkaline precipitant facilitates the recycling of the mother liquor and achieves better leaching performance.

[0026] The present invention demonstrates that a preferred alkaline precipitant helps to further improve PbCl₂. x y- The conditioning effect of the complex on the conversion of PbCl2 into lead chloride ore improves the selectivity of precipitation and also facilitates the direct recycling of the mother liquor as a leaching agent. In this invention, PbCl2... x y- For example, PbCl3 - and / or PbCl4 2- .

[0027] In step 2, the pH of the reaction process is 6.5-9; preferably 6.7-7.5.

[0028] The precipitation reaction occurs at a temperature of 20-30℃.

[0029] The precipitation reaction takes 20 to 60 minutes.

[0030] In step 2, the liquid obtained from solid-liquid separation is directly recycled back to step 1 as a composite leachate.

[0031] Beneficial effects

[0032] This invention innovatively converts lead chloride ore selectively into water-soluble PbCl. x y- Complex, and the water-soluble PbCl x y- By selectively conditioning and precipitating the complex, lead can be efficiently and selectively converted to produce high-quality hydroxyl chloride lead ore. The method of this invention achieves high lead recovery, high product phase purity, and high overall quality. Furthermore, the leachate described in this invention can be directly recycled as needed without evaporation or secondary solute addition, and the recycled lead has high recovery rate and phase purity.

[0033] This invention enables deep leaching of lead at room temperature in a short time, and selectively converts lead into a hydroxyl chloride lead mineral phase through solution conditioning of the lead-chloride complex, thus achieving efficient one-step lead recovery without introducing other impurity ions. Studies show that after treatment with this invention, the lead removal rate from the water-leached slag of iron and steel dust can reach over 93%, and the residual lead content in the iron-rich filter residue is less than 0.7 wt%. Iron loss during lead leaching is less than 4%, and the iron grade is increased by more than 20%. Furthermore, fluorine is essentially not dissolved during the leaching process. The lead-containing leachate, after conditioning and precipitation, yields a hydroxyl chloride lead mineral product with a purity exceeding 83 wt% in one step, with a lead recovery rate exceeding 80%. The conditioning and precipitation process improves the lead recovery rate by more than 178% compared to the cooling crystallization process. Attached Figure Description

[0034] Figure 1 Example 1 shows the process flow for lead leaching-conditioning precipitation to recover lead products;

[0035] Figure 2 The phase diagram of the hydroxyl chloride lead ore product collected in Example 1;

[0036] Figure 3 The residual amount and removal rate of lead in the iron-rich filter residue of Example 4;

[0037] Figure 4 Example 5: Residual lead and removal rate in iron-rich filter residue.

[0038] Figure 5 The phase diagram is shown for the lead product recovered in Comparative Example 3. Detailed Implementation

[0039] The present invention will be further described in detail below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] A method for leaching and conditioning precipitation of lead from steel metallurgical dust washing slag involves leaching lead-containing steel metallurgical dust in a composite leaching solution; and recovering lead by means of Pb without dissolving the iron phase in the washing slag. 2+ In high Cl - In the environment, it will react with Cl - The lead-containing leaching solution selectively extracts lead from the washing residue, yielding iron-rich filter residue and lead-containing filtrate. Then, an alkaline precipitant is used to induce the lead phase in the lead-containing leaching solution to be converted into lead chloride (Pb(OH)Cl) precipitate, achieving efficient lead recovery. At the same time, no other impurity ions are introduced during the conditioning and precipitation process, and the leaching solution can be reused after acid is added after the lead product is recovered.

[0041] The composite leachate is a mixed solution of chloride salt and hydrochloric acid, or a mixed solution of acetate salt and acetic acid; the chloride salt is one of sodium chloride, calcium chloride, potassium chloride, and ferric chloride; the acetate salt is one of sodium acetate, calcium acetate, and potassium acetate.

[0042] In the lead-containing steel metallurgical dust washing slag, the lead-bearing phase includes hydroxyl chloride ore; wherein the lead content is 2wt%~20wt%.

[0043] The alkaline precipitant contains oxides and hydroxides of alkaline earth metals and alkali metals, the specific types of which are related to the salts used in the leachate. The metal cations in the alkaline precipitant are consistent with those in the salts used in the leachate.

[0044] This invention innovatively demonstrates that using the aforementioned alkaline precipitant for conditioning and precipitation treatment can convert lead in the leachate into a lead hydroxychlorophosphate mineral phase. This allows for efficient one-step recovery of lead without introducing impurity ions, thereby producing high-quality lead products. Furthermore, this invention causes virtually no loss of iron in the water-leached slag from iron and steel metallurgical dust; the iron-rich filter residue after lead removal can be directly returned to the sintering process.

[0045] In this invention, the metallurgical dust containing zinc, carbon, and alkali metal elements comprises the following components and contents: iron 30wt%~50wt%, lead 2wt%~20wt%, calcium 3wt%~10wt%; chlorine 0.5wt%~5wt%, sulfur 0.5wt%~2wt%, fluorine 2wt%~7wt%, and carbon 1wt%~5wt%. The iron-bearing phases include hematite and magnetite, with magnetite comprising 50wt%~60wt% of the iron phase. The lead-bearing phases include hydroxyl chloride, potassium lead sulfate, and potassium sulfate, with hydroxyl chloride comprising 60wt%~80wt% of the lead phase. The calcium-bearing phases include fluorite and dolomite, with fluorite comprising 50wt%~80wt% of the calcium phase. The remainder in the metallurgical dust consists of oxides of silicon, aluminum, and magnesium, as well as unavoidable trace impurities from the metallurgical process.

[0046] In this invention, the salt in the composite leachate can be one of chloride or acetate; further, it can be one of sodium chloride, calcium chloride, potassium chloride, ferric chloride, or sodium acetate, calcium acetate, and potassium acetate; even further, it can be calcium chloride. Studies have shown that the preferred use of calcium chloride can avoid the leaching of fluorine from the lead-containing iron and steel metallurgical dust water leaching residue, and can also avoid the problem of alkali metal residue that may be caused by filtration issues.

[0047] In this invention, the acid in the composite leachate can be either brine or acetic acid; more specifically, hydrochloric acid. Studies have shown that hydrochloric acid is preferred as it has a better promoting effect on the dissolution of lead.

[0048] In this invention, the alkaline precipitant can be an oxide or hydroxide of an alkaline earth metal or an alkali metal; further, it can be calcium oxide, potassium oxide, sodium oxide, calcium hydroxide, potassium hydroxide, or sodium hydroxide; and even further, it can be calcium oxide.

[0049] In this invention, the salt concentration of the composite leachate is 300 g / L to 500 g / L, and more specifically, it can be 350 g / L to 400 g / L.

[0050] In this invention, the acid concentration of the composite leachate is 0.04 mol / L to 2 mol / L; more specifically, it can be 0.06 mol / L to 0.2 mol / L, and even more specifically, it can be 0.08 mol / L to 0.12 mol / L.

[0051] In this invention, the leaching process temperature, time, and stirring speed can be adjusted reasonably as needed.

[0052] The leaching temperature is 20 ℃~90 ℃; further, it can be 20 ℃~40 ℃, and even further, it can be 25 ℃~30 ℃.

[0053] The leaching time is 5 min to 90 min; considering processing efficiency, it can be further reduced to 5 min to 40 min, and even further reduced to 15 min to 20 min. The composite leaching solution used in this invention can achieve efficient leaching of lead in a relatively short time.

[0054] The liquid-to-solid ratio during the leaching process is 1 mL / g to 10 mL / g, and considering the processing cost, it can be further reduced to 7 mL / g to 9 mL / g.

[0055] In this invention, the final pH of the leaching is 2.5 to 5.

[0056] In this invention, the amount of alkaline precipitant added during the conditioning and precipitation process can be reasonably adjusted according to the lead concentration and pH in the leachate.

[0057] In this invention, a powdered alkaline precipitant is slowly added to a lead-containing leaching solution, during which the pH of the lead-containing leaching solution and the precipitation behavior in the leaching solution are continuously measured; the addition of the alkaline precipitant is stopped when the pH of the leaching solution stabilizes at 6.8~7.2 and no more precipitates are precipitated.

[0058] In this invention, based on high Cl - Pb in the environment 2+ With Cl- Leveraging the lead-chloride complex formation and dissolution property, a composite leaching solution was used to achieve highly efficient lead removal. Furthermore, an alkaline precipitant was employed to condition the lead-chloride complex into hydroxyl chloride lead ore, enabling one-step, efficient lead recovery. This method differs from traditional carbonate precipitation and alkaline precipitation methods, as it does not require the introduction of additional CO3. 2- and SO4 2- Pb precipitate 2+ There is no need to adjust the pH of the solution to alkaline.

[0059] To avoid repetition, the raw materials involved in this specific embodiment are described uniformly as follows, and will not be repeated in the specific embodiments:

[0060] The steel metallurgical dust water-leached slag used in the implementation can be sintering machine head ash water-leached slag, in which the iron content is 45.07±0.5wt%, the lead content is 9.81±0.5wt%, the calcium content is 5±0.2wt%, the chlorine content is 1.44±0.1wt%, the sulfur content is 0.75±0.2wt%, the fluorine content is 3.41±0.2wt%, and the carbon content is 2.43±0.2wt%.

[0061] The iron-bearing phases include hematite and magnetite, with magnetite accounting for 50 wt% to 60 wt% of the iron phase; the lead-bearing phases include hydroxyl chloride, with hydroxyl chloride accounting for 70 ± 0.5 wt% of the total lead phase; and the calcium-bearing phases include fluorite and dolomite, with fluorite accounting for 80 wt% of the calcium phase.

[0062] The ash-water leaching residue from the sintering machine head also contains oxides of silicon, aluminum, and magnesium, as well as trace impurities that are unavoidable in the metallurgical process.

[0063] The specific implementation method of this invention is as follows: Appropriate amounts of iron and steel metallurgical dust, alkaline precipitant, and deionized water are weighed according to a set liquid-to-solid ratio and placed in conventional and microwave high-pressure reaction vessels. A mechanical stirring leaching reaction is then carried out at a set temperature for a period of time, with an appropriate stirring speed. After the leaching reaction is completed, the leachate and residue (iron-rich filter residue) are separated using suction filtration or pressure filtration. The residual lead content in the iron-rich filter residue and the grade of the recovered lead chloride ore product are detected using ICP. The total iron grade in the iron-rich filter residue is determined using potassium dichromate titration.

[0064] In this invention, the residual amount of lead in the iron-rich filter residue refers to the weight percentage of lead element, and the removal rate is calculated from the residual amount.

[0065] Example 1

[0066] according to Figure 1 The process involves the following steps:

[0067] Step 1: Leaching:

[0068] Weigh out appropriate amounts of calcium chloride and hydrochloric acid to a concentration of 350 g / L and 0.1 mol / L respectively, dissolve them in water, and stir at room temperature until the calcium chloride is completely dissolved to prepare a composite leachate. Use the leachate after it has cooled.

[0069] At room temperature, an appropriate amount of sintering machine head ash water leaching residue was placed in a composite leaching solution with a calcium chloride concentration of 350 g / L and a hydrochloric acid concentration of 0.1 mol / L at a liquid-to-solid ratio of 8 mL / g. The solution was leached for 15 min under a stirring speed of 300 r / min. After the reaction, solid-liquid separation was carried out by vacuum filtration to obtain lead-containing leaching solution and iron-rich filter residue.

[0070] The lead content in the iron-rich filter residue was measured to be 0.64 wt%; the lead removal rate was calculated to be 93.04%.

[0071] Step 2:

[0072] Step a: At room temperature, slowly add powdered calcium oxide precipitant to the lead-containing leachate, continuously measuring the pH of the leachate and the precipitation behavior within it; stop adding the alkaline precipitant when the pH of the leachate stabilizes at 7.15 and no more precipitates are formed. After solid-liquid separation, obtain the hydroxychlorolead ore product and the leachate.

[0073] Step b: Add hydrochloric acid to the leachate obtained in step a until the concentration of hydrochloric acid in the leachate reaches 0.1 mol / L, and then use it again to leach the washing slag of iron and steel metallurgical dust according to the operation and parameters of Example 1.

[0074] The purity of the hydroxychlorolead ore product obtained in step a was determined to be 83.22%, and the lead recovery rate was 80.27%. The phase composition of the product is as follows: Figure 2 As shown. The lead content in the iron-rich filter residue obtained from the first cycle of the leaching agent in step b was 0.66 wt%; the calculated lead removal rate was 93%.

[0075] Comparative Example 1

[0076] Compared with Example 1, the only difference is that in step 1, the composite leachate is replaced with a chloride salt solution with a calcium chloride concentration of 350 g / L, which does not contain hydrochloric acid. All other operations and parameters are the same as in Example 1.

[0077] The lead content in the iron-rich filter residue was measured to be 9.75 wt%; the lead removal rate was calculated to be 0.6%.

[0078] Comparative Example 2

[0079] Compared with Example 1, the only difference is that in step 1, the composite leachate is replaced with an acid solution with a hydrochloric acid concentration of 0.1 mol / L, and does not contain calcium chloride salt. All other operations and parameters are the same as in Example 1.

[0080] The lead content in the iron-rich filter residue was measured to be 9.30 wt%; the lead removal rate was calculated to be 5.31%.

[0081] Example 2

[0082] Compared with Example 1, the only difference is that in step 1, the composite leachate is replaced with a mixed solution with a sodium chloride concentration of 350 g / L and a hydrochloric acid concentration of 0.1 mol / L. All other operations and parameters are the same as in Example 1.

[0083] The lead content in the iron-rich filter residue was measured to be 0.81 wt%; the lead removal rate was calculated to be 91.49%.

[0084] Example 3

[0085] Compared with Example 1, the only difference is that in step 1, the composite leachate is replaced with a mixed solution of calcium acetate with a concentration of 350 g / L and acetic acid with a concentration of 0.1 mol / L. All other operations and parameters are the same as in Example 1.

[0086] The lead content in the iron-rich filter residue was measured to be 1.00 wt%; the lead removal rate was calculated to be 87.79%.

[0087] Example 4

[0088] Compared to Example 1, the only difference is the change in the concentration of calcium chloride, which ranges from 200 g / L to 450 g / L (specifically: Group A: 200 g / L; Group B: 250 g / L; Group C: 300 g / L; Group D: 350 g / L (Example 1); Group E: 400 g / L; Group F: 450 g / L). All other operations and parameters are the same as in Example 1.

[0089] The lead removal rate from steel dust water-leached slag and the residual lead content in iron-rich filter slag are shown in [reference needed]. Figure 3 .

[0090] When the concentration of calcium chloride is 200 g / L, the residual lead content in the iron-rich filter residue is 4.94 wt%; the calculated lead removal rate is 43.22%.

[0091] When the concentration of calcium chloride is 250 g / L, the residual lead content in the iron-rich filter residue is 3.52 wt%; the calculated lead removal rate is 61.40%.

[0092] When the concentration of calcium chloride is 300 g / L, the residual lead content in the iron-rich filter residue is 1.97 wt%; the calculated lead removal rate is 78.25%.

[0093] Increasing the concentration of calcium chloride to 400 g / L and 450 g / L did not significantly improve the lead removal effect.

[0094] Example 5

[0095] Compared to Example 1, the only difference is the change in the concentration of hydrochloric acid, which ranges from 0.02 mol / L to 0.12 mol / L (specifically: Group A: 0.02 mol / L; Group B: 0.04 mol / L; Group C: 0.06 mol / L; Group D: 0.08 mol / L; Group E: 0.10 mol / L (Example 1); Group F: 0.12 mol / L). All other operations and parameters are the same as in Example 1.

[0096] The lead removal rate from steel dust water-leached slag and the residual lead content in iron-rich filter slag are shown in [reference needed]. Figure 4 .

[0097] When the concentration of hydrochloric acid is 0.02 mol / L, the residual lead content in the iron-rich filter residue is 4.53 wt%; the calculated lead removal rate is 48.09%.

[0098] When the concentration of hydrochloric acid is 0.04 mol / L, the residual lead content in the iron-rich filter residue is 2.66 wt%; the calculated lead removal rate is 70.22%.

[0099] When the concentration of hydrochloric acid was 0.06 mol / L, the residual lead content in the iron-rich filter residue was 1.64 wt%; the lead removal rate was calculated to be 82.30%.

[0100] When the concentration of hydrochloric acid is 0.08 mol / L, the residual lead content in the iron-rich filter residue is 1.49 wt%; the calculated lead removal rate is 84.01%.

[0101] When the concentration of hydrochloric acid is 0.10 mol / L, the residual lead content in the iron-rich filter residue is 0.64 wt%; the lead removal rate is calculated to be 93.04%.

[0102] Increasing the concentration of hydrochloric acid to 0.12 mol / L did not significantly improve the lead removal effect.

[0103] Comparative Example 3

[0104] Compared with Example 1, the difference is that in step 2, the method of recovering lead products is changed to adding 30% cold water to the lead-containing leaching solution, and then letting it stand for 20 min-30 min until the precipitation is complete before solid-liquid separation to obtain lead products.

[0105] The physical phases of lead products are as follows Figure 5 As shown, the main phase of the obtained lead product was lead chloride, with a lead content of 68.49% and a recovery rate of 24.48%.

[0106] Comparative Example 4

[0107] Compared with Example 2, the only difference is that in step 2, the method of recovering lead products is changed to adding 30% cold water to the lead-containing leaching solution, and then letting it stand for 20 min-30 min until the precipitation is complete before solid-liquid separation to obtain lead products.

[0108] The main phases of the obtained lead product were determined to be lead chloride and lead fluoride chloride, with a lead content of 67.45% and a recovery rate of 20.79%.

[0109] Example 6

[0110] Compared with Example 1, the only difference is that in step 2, the final pH of the leachate from step a is stabilized at 5-10 (group A: final pH 5; group B: final pH 6; group C: final pH 7; group D: final pH 8; group E: final pH 9; group F: final pH 10). Other operations and parameters are the same as in Example 1.

[0111] Measurements showed that:

[0112] No precipitate was formed in group A.

[0113] The lead product obtained from Group B was mainly hydroxychlorobolite, with a purity of 80.32% and a lead recovery rate of 40.33%.

[0114] The lead product obtained from Group C was mainly hydroxychlorocoline, with a purity of 82.13% and a lead recovery rate of 78.89%.

[0115] The lead product obtained from Group D was mainly hydroxychlorocoline, with a purity of 84.32% and a lead recovery rate of 85.23%.

[0116] The lead product obtained from Group E was mainly hydroxychlorohydrin, with a purity of 84.21% and a lead recovery rate of 83.27%.

[0117] The lead product obtained from Group F was mainly lead hydroxide, with a purity of 80.22% and a lead recovery rate of 85.27%.

[0118] Example 7

[0119] Compared to Example 1, the only difference is that in step 2, the alkaline precipitant in step a is replaced with sodium hydroxide. All other operations and parameters are the same as in Example 1.

[0120] The purity of the hydroxychlorolead ore product obtained in step a was determined to be 83.13%, and the lead recovery rate was 79.87%. The lead content in the iron-rich filter residue obtained from the first cycle of the composite leaching agent in step b was 1.19 wt%; the calculated lead removal rate was 87.36%. The reuse performance of the composite leaching solution declined.

Claims

1. A method for leaching and preparing lead chloride ore from steel metallurgical dust washing slag, characterized in that the steps include... include: Step 1: Iron and steel metallurgical dust washing slag containing hydroxyl chloride lead ore is leached in a composite leaching solution to convert the hydroxyl chloride lead ore into water-soluble PbCl. x y- The complex was then subjected to solid-liquid separation to obtain PbCl-rich material. x y- Leachate and iron slag of the complex; PbCl x y- In the equation, x is 3 or 4, and y is 1 or 2; The composite leachate is an aqueous solution containing dissolved acid and auxiliaries; the acid is at least one of hydrochloric acid and acetic acid; the auxiliaries are water-soluble salts of at least one cation selected from Na, K, Ca, and Fe; the concentration of the acid is above 0.04 mol / L; and the concentration of the auxiliaries is above 300 g / L. Step 2: Add an alkaline precipitant to the leachate to remove PbCl. x y- The system pH during the conditioning and precipitation process is 6-10. Subsequently, solid-liquid separation was performed to obtain hydroxychlorolead ore.

2. The method for leaching and preparing lead chloride ore from iron and steel metallurgical dust washing slag as described in claim 1, characterized in that, The lead content in the steel metallurgical dust washing slag is 2wt%~20wt%. Preferably, in the steel metallurgical dust washing slag, the lead in the lead oxychloride lead ore accounts for more than 60 wt% of the total lead weight, preferably 60 wt% to 80 wt%.

3. The method for leaching and preparing lead chloride ore from iron and steel metallurgical dust washing slag as described in claim 1, characterized in that, In the slag washed from iron and steel metallurgical dust, the iron content is 30wt%~50wt%; the iron-bearing phases include hematite and magnetite, with magnetite accounting for 50wt%~60wt% of the iron phase. And / or, the washing slag of iron and steel metallurgical dust also contains calcium, chlorine, sulfur and fluorine; wherein the calcium content is 3wt%~10wt%; the chlorine content is 0.5wt%~5wt%; the sulfur content is 0.5wt%~2wt%; the fluorine content is 2wt%~7wt%; and the carbon content is 1wt%~5wt%. The calcium-bearing phases include fluorite and dolomite, wherein the fluorite content is 50wt%~80wt% of the calcium phase.

4. The method for leaching and preparing lead chloride ore from iron and steel metallurgical dust washing slag as described in claim 1, characterized in that, In the composite leachate, the acid is hydrochloric acid; the auxiliary agent is calcium chloride.

5. The method for leaching and preparing lead chloride ore from iron and steel metallurgical dust washing slag as described in claim 1, characterized in that, In the composite leachate, the concentration of acid is 0.06 mol / L to 0.15 mol / L; the concentration of additives is 320 g / L to 500 g / L.

6. The method for leaching and preparing lead chloride ore from iron and steel metallurgical dust washing slag as described in claim 1, characterized in that, In step 1, the leaching temperature is 20 ℃~90 ℃, preferably 20 ℃~30 ℃; The leaching time is 5 min to 90 min, preferably 10 min to 20 min; The liquid-to-solid ratio of the leaching solution is 1 mL / g to 10 mL / g.

7. The method for leaching and preparing lead chloride ore from iron and steel metallurgical dust washing slag as described in claim 1, characterized in that, In step 2, the alkaline precipitant is at least one of the oxides and hydroxides of the cations involved in the additives.

8. The method for leaching and preparing lead chloride ore from iron and steel metallurgical dust washing slag as described in claim 7, characterized in that, In step 2, the alkaline precipitant includes at least one of calcium oxide and calcium hydroxide.

9. The method for leaching and preparing lead chloride ore from iron and steel metallurgical dust washing slag as described in claim 1, characterized in that, In step 2, the pH of the reaction process is 6.5~9; preferably 6.5~7.5; The precipitation reaction occurs at a temperature of 20-30℃. The precipitation reaction takes 20 to 60 minutes.

10. The method for leaching and preparing lead chloride ore from iron and steel metallurgical dust washing slag as described in any one of claims 1 to 9, characterized in that, In step 2, the liquid obtained from solid-liquid separation is directly recycled back to step 1 as a composite leachate.

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