Method for recovering antimony from antimony secondary resources by wet leaching

Abstract

The application discloses a method for recovering antimony from secondary antimony resources by wet leaching, and belongs to the technical field of metallurgical solid waste resource recovery. After water-quenched slag generated in an antimony smelting process is ground, the ground water-quenched slag is subjected to leaching by taking a strong alkali solution as a leaching agent and taking a multi-element organic carboxylic compound and a water-soluble sulfide salt as leaching aids, so as to obtain an antimony-containing leaching solution. The method adopts a special alkaline leaching system, inhibits the leaching of impurity metals such as iron by sulfidation, and simultaneously strengthens the leaching of antimony by complexation, so that high-selectivity and high-efficiency leaching of antimony is realized, and the resource recovery of antimony is facilitated.

Description

Technical Field

[0001] This invention relates to a method for secondary antimony resource recovery, and more particularly to a method for secondary antimony resource recovery by wet leaching, belonging to the field of metallurgical solid waste resource recovery technology. Background Technology

[0002] Antimony is a scarce metal resource, and antimony compounds and antimony alloys play an irreplaceable role in industries such as flame retardant materials, lead-acid batteries, alloy hardeners, fluorochemical catalysts, and semiconductors.

[0003] The development and utilization of existing antimony resources mainly rely on pyrometallurgy, hydrometallurgy, and combined beneficiation and smelting processes. Pyrometallurgy typically employs a process route of blast furnace volatilization smelting followed by reverberatory furnace reduction smelting and refining. This method offers advantages such as strong raw material adaptability, large production capacity, and high metal recovery rates. However, it also suffers from drawbacks such as long process flow, high energy consumption, large amounts of recycled material, low SO2 concentration, and significant pollution problems. Hydrometallurgy mainly includes acid leaching and alkaline leaching processes. Alkaline leaching is represented by leaching with a Na2S–NaOH system followed by electrowinning to recover antimony, while acid leaching primarily uses FeCl3–HCl leaching followed by electrodeposition. However, during these pyrometallurgical and hydrometallurgical processes, a considerable amount of antimony still enters the smelting waste in the form of dispersed antimony beads, antimony oxide, or antimonates, resulting in the waste of valuable metal resources and posing potential environmental risks.

[0004] In the antimony smelting process, typical solid waste mainly includes three categories: lead-removing slag, arsenic-alkali slag, and water-quenched slag. Antimony in lead-removing slag is mostly in the form of antimony phosphate or antimony metaphosphate, and its recovery methods mainly include pyrometallurgical reduction smelting and hydrometallurgical treatment. Pyrometallurgical treatment typically returns the lead-removing slag to the blast furnace or uses iron filings to recover lead-antimony alloys, but this method is difficult to achieve effective separation of lead and antimony and has problems with secondary waste generation and high energy consumption. Hydrometallurgical treatment often uses the water-ammonia method or sulfidation method to reduce phosphorus content and recover antimony, but the process is complex and reagent consumption is high, making stable industrial application difficult. Arsenic-alkali slag mainly contains arsenic in the form of sodium arsenate, while antimony exists in the form of sodium antimonyite and some metallic antimony. Its treatment methods include pyrometallurgical, hydrometallurgical, and combined pyrometallurgical and hydrometallurgical processes. Pyrometallurgical treatment often enriches antimony through secondary smelting and carbon reduction, but it easily produces low-grade secondary arsenic-alkali slag, posing a risk of malignant arsenic enrichment and environmental hazards. Wet treatment mainly utilizes the difference in solubility of arsenic and antimony in solution for separation, such as calcium salt precipitation and sulfide precipitation. However, the resulting arsenic-containing solidified products have poor stability and often fail to meet toxicity leaching standards, requiring further treatment and making large-scale application difficult. While pyrometallurgical-hydrometallurgical combined processes can effectively enrich antimony, they suffer from high energy consumption and high costs. In summary, lead-removing slag and arsenic-alkali slag generally face challenges in separation, high energy consumption, and high environmental risks during recycling, hindering their widespread resource utilization. Compared to lead-removing slag and arsenic-alkali slag, water-quenched slag has a relatively lower antimony grade, typically 1%–3%, and its production volume is large, with massive stockpiles. However, there are currently few reports on antimony resource recovery from water-quenched slag, mainly because it is glassy particulate matter formed by rapid water quenching of high-temperature molten slag during antimony smelting. The difficulty in its recovery lies in the fact that antimony elements are often trapped in silicate network structures as micron-sized inclusions or complex bonds, resulting in low efficiency of physical desorption and conventional chemical leaching. Existing processing methods primarily involve returning the smelting system for pyrometallurgical reprocessing, enriching antimony through volatilization. For example, Chinese patent application (publication number CN1621544A) discloses the treatment of indium-containing lead-antimony smelting water-quenched slag in reduction furnaces such as rotary kilns, zinc white furnaces, or fuming furnaces. After reduction by carbon and carbon monoxide at high temperatures (above 1100℃) in these furnaces, the indium-containing lead-antimony smelting water-quenched slag can be volatilized to recover indium, zinc, lead, antimony, and silver, respectively. This method, relying on pyrometallurgical smelting, suffers from drawbacks such as high energy consumption, long processing cycles, and poor economic efficiency. Summary of the Invention

[0005] To address the shortcomings of existing antimony smelting technologies, which primarily employ pyrometallurgical methods for refining water-quenched slag, resulting in high energy consumption, long processing cycles, and poor economic efficiency, this invention aims to provide a method for secondary antimony recovery through wet leaching. This method utilizes an alkaline leaching system, inhibiting the leaching of impurities such as iron through sulfidation while simultaneously enhancing antimony leaching through complexation. This achieves highly selective and efficient antimony leaching, facilitating the resource recovery of antimony. The method is simple, energy-efficient, and yields a high antimony recovery rate, thus possessing significant economic value.

[0006] To achieve the above-mentioned technical objectives, this invention provides a method for secondary antimony recovery through wet leaching. The method involves grinding water-quenched slag produced during antimony smelting, then leaching it using a strong alkaline solution as the leaching agent, and a poly-organic carboxylic acid compound and a water-soluble sulfide salt as leaching aids to obtain an antimony-containing leachate. The leaching conditions are: a liquid-to-solid ratio of 4L:1kg to 6L:1kg, a temperature of 80 to 100℃, a stirring rate of 500 to 700 r / min, a leaching time of 1 to 2 hours, and a sodium hydroxide solution, wherein the mass of sodium hydroxide is 30% to 50% of the mass of the water-quenched slag; the amount of water-soluble sulfide salt added is 5% to 15% of the mass of the water-quenched slag; and the amount of poly-organic carboxylic acid compound added is 0.1% to 0.5% of the mass of the water-quenched slag.

[0007] The key to this invention's antimony leaching process in water-quenched slag lies in the simultaneous use of polybasic organic carboxylic acid compounds as complexing agents and water-soluble sulfides as sulfiding agents within a strong alkali leaching system. The strong alkali, polybasic organic carboxylic acid compounds, and water-soluble sulfides synergistically promote the leaching of antimony. Specifically, the strong alkali primarily disrupts the structural stability of the silicate and antimony phases, while the sulfides mainly neutralize the antimony. 2- The ions react with partially oxidized or complexed antimony in the water-quenched slag through a sulfidation reaction, transforming the originally dense and insoluble antimony oxide or antimony silicate phase into more reactive antimony sulfide or soluble antimony thiocomplexes. This significantly lowers the reaction energy barrier for antimony migration from the solid to the liquid phase. Simultaneously, S... 2- Ions have a good selective sulfidation effect on impurity metals such as iron in the system, which helps to inhibit the synchronous dissolution of impurity elements in the early stage of leaching and improve the selective leaching behavior of antimony. Meanwhile, polycarboxylic acid compounds can form a stable chelate structure with Sb(V) and Sb(III) ions through the multidentate carboxyl group structure, effectively reducing the free activity of antimony ions and inhibiting their hydrolysis, polymerization and redeposition behavior, thereby significantly increasing the stable presence ratio of antimony in the leachate and effectively promoting the leaching of antimony.

[0008] As a preferred embodiment, the mass percentage of the water-quenched slag ground to a particle size of less than 200 mesh is not less than 70%. Grinding to an appropriate particle size is beneficial to improving the specific surface area and chemical reactivity of the water-quenched slag.

[0009] The amount of water-soluble sulfide salt added in this invention is 5% to 15% of the mass of the water-quenched slag. If the amount of water-soluble sulfide salt added is too low, it will not achieve the purpose of promoting antimony leaching. Excessive water-soluble sulfide salt will not promote antimony leaching, but will instead increase the cost of the reagent.

[0010] As a preferred embodiment, the water-soluble sulfide salt comprises sodium sulfide. The water-soluble sulfide salt can be a water-soluble hydrosulfate or a sulfide salt, primarily providing S. 2- or HS - However, HS - Since it consumes alkali, a water-soluble sulfide salt is preferred, and sodium sulfide is even more preferred, as it provides sulfur. 2- It undergoes a sulfidation reaction with partially oxidized or complexed antimony in water-quenched slag, transforming the originally dense and insoluble antimony oxides or antimony and antimonate phases into more reactive antimony sulfide precursors or soluble antimony thioreanes, significantly lowering the reaction energy barrier for antimony migration from the solid to the liquid phase. Simultaneously, S... 2- It has a selective sulfidation effect on impurity metals such as iron in the system, which helps to inhibit the synchronous dissolution of impurity elements in the early stage of leaching and improve the selective leaching behavior of antimony.

[0011] The amount of the poly-organic carboxylic acid compound added in this invention is 0.1% to 0.5% of the mass of the water-quenched slag. If the amount of the poly-organic carboxylic acid compound added is too low, the leaching effect on antimony will not be significantly promoted; if the amount of the poly-organic carboxylic acid compound added is too high, the leaching effect on antimony will not be significantly promoted, and the subsequent antimony precipitation will be more difficult.

[0012] As a preferred embodiment, the polybasic organic carboxylic acid compound includes at least one selected from ethylenediaminetetraacetic acid, ethylenediaminetetraacetic acid salt, diethylenetriaminepentaacetic acid, diethylenetriaminepentaacetic acid salt, citric acid, citrate, tartaric acid, and tartrate. Most preferably, it is disodium ethylenediaminetetraacetate and / or sodium citrate. Extensive experiments have shown that in a strongly alkaline leaching system, the preferred polybasic organic carboxylic acid compound can form a stable chelate structure with Sb(V) and Sb(III) ions through its multidentate carboxyl group structure, effectively reducing the free activity of antimony ions and inhibiting their hydrolysis, polymerization, and redeposition behavior, thereby significantly increasing the stable proportion of antimony in the leachate.

[0013] The leaching conditions of this invention are as follows: liquid-to-solid ratio of 4L:1kg to 6L:1kg, temperature of 80-100℃, stirring rate of 500-700 r / min, leaching time of 1-2 h, and the strong alkali solution is a sodium hydroxide solution, wherein the mass of sodium hydroxide is 30%-50% of the mass of the water-quenched slag. Under the preferred liquid-to-solid ratio, good mass transfer conditions in the reaction system are ensured, and the volume of the leachate is effectively reduced, thus reducing the load on subsequent treatments. Under the preferred concentration of the strong alkali solution, the structural stability of antimony oxides and some sulfides is effectively disrupted, while avoiding excessive alkali consumption that leads to increased system viscosity and intensified impurity dissolution. Under the preferred ambient temperature and stirring rate, the dissociation rate of mineral structures and the kinetics of complexation reactions are significantly accelerated. Within the preferred leaching time range, sufficient antimony leaching is ensured without increasing the dissolution of excessive impurity metals. After leaching, the system is allowed to stand for 30 min for solid-liquid separation to obtain a stable and clear leachate. The leaching temperature is further preferably 80-90℃. The sodium hydroxide mass is further preferably 40% to 50% of the mass of the water-quenched slag.

[0014] As a preferred embodiment, the antimony-containing leachate is adjusted to a pH range of 6.0–8.0 to form antimony precipitate. Hydrochloric acid or sulfuric acid is added dropwise to the antimony-containing leachate as a neutralizing agent under continuous stirring, slowly adjusting the pH to the range of 6.0–8.0. Antimony gradually transforms from a stable dissolved state into a sparingly soluble precipitate. After precipitation, the product is allowed to stand, filtered, and washed with water to obtain a precipitated antimony product mainly composed of antimony compounds, providing a raw material basis for subsequent reduction to prepare metallic antimony or refining.

[0015] Compared with the prior art, the beneficial technical effects of the technical solution of the present invention are as follows:

[0016] The key to this invention in the alkaline leaching process of water-quenched slag lies in the simultaneous introduction of poly-organic carboxylic acid compounds and water-soluble sulfide salts into the strong alkaline leachate. This significantly promotes the leaching of antimony and inhibits the dissolution of impurity metals, thereby improving the leaching efficiency and selectivity of antimony. This achieves efficient and stable leaching of water-quenched slag, providing a new technical approach for the clean treatment and high-value utilization of arsenic and antimony resources, and has good prospects for industrial promotion. Attached Figure Description

[0017] Figure 1 The image shows the XRD pattern of the water-quenched slag.

[0018] Figure 2 This is a picture of antimony precipitate residue. Detailed Implementation

[0019] The following specific embodiments are intended to further illustrate the content of the present invention, rather than to limit the scope of protection of the claims of the present invention.

[0020] Unless otherwise specified, the chemical reagents used in the following examples are all commercially available, common analytical grade reagents.

[0021] Unless otherwise specified, all percentages (%) in the following examples are mass percentages.

[0022] Example 1

[0023] The water-quenched slag produced by the smelter of Hunan Chenzhou Mining Co., Ltd. was used as the research object. Its main elemental composition is shown in Table 1. As can be seen from Table 1, the water-quenched slag has high contents of Fe, Si, and Ca, and also contains a certain amount of antimony, with trace amounts of gold. It is a typical antimony-containing polymetallic smelting water-quenched slag and has high comprehensive recovery value. The XRD pattern is shown below. Figure 1 As shown, no obvious Sb diffraction peaks were observed by XRD, indicating that Sb exists in the phase in an amorphous state.

[0024] Table 1. Main elemental composition (%) of water-quenched slag

[0025] The water-quenched slag was ground to a particle size of less than 200 mesh, with 80% of the sample being pre-treated. 10g of the pre-treated water-quenched slag sample was weighed, in which antimony mainly existed as antimonates and antimony oxide. The water-quenched slag was placed in a beaker, and deionized water was added at a liquid-to-solid ratio of 5L:1kg. Sodium hydroxide (40% of the slag mass) was added and fully dissolved. Then, a polycarboxylic acid compound (0.5% of the slag mass) was added, followed by sodium sulfide (10% of the slag mass). The leaching reaction was carried out at 80℃ with magnetic stirring at a stirring rate of 600r / min for 2 hours. After the reaction, the mixture was allowed to stand for 1 hour, and then filtered to achieve solid-liquid separation. The resulting leachate was used for antimony content analysis, and the leachate residue was used for residual antimony determination. The antimony-containing leachate was adjusted to neutral pH to form an antimony precipitate, which was used as a raw material for antimony refining.

[0026] Table 2. Effects of different types of polycarboxylic acid compounds on the leaching rates of antimony and iron in water-quenched slag.

[0027] As shown in Table 2, compared to the absence of added polycarboxylic acids, the introduction of polycarboxylic acids significantly improves the antimony leaching rate in water-quenched slag. However, different polycarboxylic acids exhibit varying degrees of improvement in antimony leaching. For instance, polycarboxylic acid salts generally show better results than their corresponding polycarboxylic acids, while disodium ethylenediaminetetraacetate (EDTA-2Na) is more effective than sodium citrate and sodium tartrate, significantly reducing the antimony content in the leaching slag and increasing the antimony leaching rate. Conversely, the various polycarboxylic acids have a relatively small effect on increasing the iron leaching rate in the water-quenched slag, with iron consistently maintaining a low leaching rate.

[0028] Example 2

[0029] The specific operation and steps are the same as in Example 1, except that: the polycarboxylic acid compound selected is EDTA-2Na, and its content is controlled within the range of 0~1% of the mass of the water-quenched slag.

[0030] Table 3. Effect of EDTA-2Na addition on the leaching rate of antimony and iron in water-quenched slag

[0031] Table 3 shows that with the increase of EDTA-2Na addition, the antimony leaching rate initially increases significantly and then levels off. The antimony leaching effect is optimal when the EDTA-2Na addition is between 0.3% and 0.5%, and further increases in EDTA-2Na do not significantly improve the antimony leaching rate. Meanwhile, with the increase of EDTA-2Na addition, the iron leaching rate remains consistently below 5%.

[0032] Example 3

[0033] The specific operation and steps are the same as in Example 1, except that: the polycarboxylic acid compound selected is EDTA-2Na, and its content is 0.5% of the mass of the water-quenched slag. The reaction temperature is controlled within the range of 60 to 100°C.

[0034] Table 4. Effects of different leaching temperatures on the leaching rates of antimony and iron in water-quenched slag

[0035] The effects of reaction temperature on the leaching rates of antimony and iron in water-quenched slag are shown in Table 4. The results indicate that the antimony leaching rate increases significantly with increasing reaction temperature, reaching its maximum at 80℃. Further increases in temperature exacerbate sulfide decomposition and antimony re-precipitation, leading to a slight decrease in the antimony leaching rate. Meanwhile, the iron leaching rate remains below 5% with increasing temperature. Therefore, the preferred reaction temperature is 70–90℃, with an optimal value of approximately 80℃.

[0036] Example 4

[0037] The specific operation and steps are the same as in Example 1, except that: the polycarboxylic acid compound selected is EDTA-2Na, and its content is 0.5% of the mass of the water-quenched slag, and the mass of sodium hydroxide is adjusted to 10% to 50% of the mass of the water-quenched slag.

[0038] Table 5. Effects of different NaOH concentrations on the leaching rates of antimony and iron in water-quenched slag.

[0039] The effects of different sodium hydroxide concentrations on the leaching of antimony and iron in water-quenched slag are shown in Table 5. The results indicate that when the sodium hydroxide concentration is too low, it is difficult to disrupt the silicate network structure in the water-quenched slag, thus limiting antimony release. When the NaOH concentration is increased to 40%, the antimony leaching rate significantly improves. Further increasing the NaOH concentration has little effect on promoting the antimony leaching rate and significantly increases alkali consumption. However, with increasing sodium hydroxide content, the iron leaching rate remains below 5%. Therefore, the preferred sodium hydroxide mass fraction is 30%–45%, with an optimal value of approximately 40%.

[0040] Example 5

[0041] The pH of the antimony-containing leachate was adjusted to precipitate antimony. When the solution pH was adjusted to neutral, the Sb content in the solution was low, and the color of the leachate changed from black to milky white. The actual image of the antimony precipitate residue is shown below. Figure 2 As shown.

[0042] Table 6. Precipitation rate of antimony in antimony-containing leachate under different pH conditions

[0043] XRF elemental analysis was performed on the antimony precipitate slag, and the elemental content analysis results are shown in Table 7 below, realizing the resource recovery and utilization of Sb component in water-quenched slag.

[0044] Table 7. XRF content analysis of antimony precipitate residue

[0045] Comparative Example 1

[0046] The specific operation and steps are the same as in Example 1, except that the effects of four additive combinations—no sodium sulfide and EDTA-2Na, sodium sulfide only, EDTA-2Na only, and both sodium sulfide and EDTA-2Na—on the leaching behavior of antimony and iron in water-quenched slag were investigated. Except for the additive combination, the liquid-to-solid ratio, NaOH dosage, reaction temperature, stirring rate, and leaching time remained the same as in Example 1.

[0047] Table 8. Effect of sodium sulfide and EDTA-2Na combination on the leaching rate of antimony and iron in water-quenched slag

[0048] As shown in Table 8, without the introduction of sodium sulfide and EDTA-2Na, the antimony leaching rate was only 28.60%, and the iron leaching rate was 10.42%. When only sodium sulfide was added, the iron leaching rate decreased to 1.96%, indicating that sodium sulfide has a significant sulfidation inhibition effect on impurity metals such as iron, but the antimony leaching rate is still limited. When only EDTA-2Na was added, the antimony leaching rate increased to 55.36%, but the iron leaching rate increased to 14.28%, indicating that EDTA-2Na can complex and enhance antimony leaching. At the same time, without the inhibition of sodium sulfide, impurity metals such as iron are easily complexed and dissolved simultaneously. When sodium sulfide and EDTA-2Na were added together, the antimony leaching rate reached 68.75%, and the iron leaching rate was controlled at 3.26%, indicating that the impurity sulfidation inhibition effect of sodium sulfide and the complexation stabilization effect of EDTA-2Na form a synergistic effect, which can achieve efficient antimony leaching and low-level iron dissolution.

Claims

1. A method for secondary antimony recovery through wet leaching, characterized in that: The water-quenched slag produced in the antimony smelting process is ground and then leached with a strong alkaline solution as the leaching agent and with poly-organic carboxylic acid compounds and water-soluble sulfide salts as leaching aids to obtain an antimony-containing leachate. The leaching conditions are as follows: liquid-to-solid ratio of 4L:1kg to 6L:1kg, temperature of 80 to 100℃, stirring rate of 500 to 700 r / min, leaching time of 1 to 2 hours, and the strong alkaline solution is sodium hydroxide solution, wherein the mass of sodium hydroxide is 30% to 50% of the mass of the water-quenched slag. The amount of water-soluble sulfide added is 5% to 15% of the mass of the water-quenched slag; The amount of the poly-organic carboxylic acid compound added is 0.1% to 0.5% of the mass of the water-quenched slag; The polycarboxylic acid compound is ethylenediaminetetraacetic acid salt.

2. The method for secondary antimony recovery by wet leaching according to claim 1, characterized in that: The mass percentage of water-quenched slag ground to a particle size of less than 200 mesh shall not be less than 70%.

3. The method for secondary antimony recovery by wet leaching according to claim 1, characterized in that: The water-soluble sulfide salt includes sodium sulfide.

4. The method for secondary antimony recovery by wet leaching according to claim 1, characterized in that: The antimony-containing leachate is adjusted to a pH range of 6.0 to 8.0 to form an antimony precipitate.

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