Leaching method for cadmium in soot of bottom blowing furnace based on ultrasonic cavitation activation-hydrogen peroxide directional oxidation

Abstract

The invention relates to a method for leaching cadmium in soot of a bottom blowing furnace based on ultrasonic cavitation activation-hydrogen peroxide directional oxidation, and belongs to the technical field of non-ferrous metal resource recovery and clean metallurgy. Aiming at the technical bottlenecks of high energy consumption, low efficiency, serious environmental pollution and the like in the existing cadmium leaching process, the invention provides an ultrasonic field hydrogen peroxide synergistic directional conversion technical scheme, and by establishing a selective conversion path from CdS to CdSO4 (soluble) and from PbSO3 to PbSO4 (stable precipitation), efficient leaching of cadmium and stable solidification of lead are synchronously realized under normal-temperature and neutral conditions. By utilizing an ultrasonic cavitation activation-hydrogen peroxide directional oxidation synergistic mechanism, accurate regulation and control of a phase conversion path are realized. By accurately controlling ultrasonic parameters (the power is 300-500 W and the time is 20-40 min), the liquid-solid ratio (2: 1-3: 1) and the H2O2 dosage (0.05-0.15 mL / g soot), collaborative optimization that the Cd leaching rate is larger than or equal to 92.5% and the lead curing rate is larger than or equal to 97% is achieved under the green condition that acid and alkali do not need to be additionally added, and the problems of pollution and energy consumption caused by a traditional high-acidity and high-temperature process are solved.

Description

Technical Field

[0001] The invention relates to a method for leaching cadmium from bottom-blown furnace ash based on ultrasonic cavitation activation-hydrogen peroxide directional oxidation, and belongs to the technical field of non-ferrous metal resource recovery and clean metallurgy. Background Art

[0002] Lead smelting bottom-blown furnace ash, a typical secondary resource containing cadmium, can contain up to 10% to 35% cadmium, offering significant recycling value. However, the high toxicity of cadmium necessitates its recycling through environmentally friendly disposal technologies. Current industry practices face a dilemma: if it is sold cheaply for export, it will lead to the loss of metal resources and reduced economic benefits. Direct recycling, while recovering some metal, will cause cadmium to circulate in a closed loop within the smelting system, reducing lead smelting efficiency and product quality while also accumulating environmental risks.

[0003] Existing cadmium recovery mainly relies on the leaching-replacement process. Although the acid leaching method can achieve a high recovery rate, it has defects such as high pollution risk and extreme energy consumption pressure. For example, Chen Chunlin et al. [Chen Chunlin, Dai Xingzheng, Wei Chang, Production practice of separating and recovering cadmium from oxygen-enriched top-blown lead smelting flue dust by co-treatment of hydrometallurgical zinc smelting, Mining and Metallurgy 32 (2023) 60–64, 83.] used a 20 g / L sulfuric acid system (70°C, liquid-solid ratio 4:1, 3 h) and achieved a cadmium recovery rate of 85.70%, but produced a large amount of acidic waste liquid, and the subsequent treatment cost was high. Li et al. [W. Li, W. Liu, F. Jiao, L. Xie, W. Qin, Comprehensive recovery of arsenic and valuable metals from lead smelting flue dust: process optimization and mechanism investigation, Separation and Purification Technology 353 (2025) 128497.] proposed a pressurized oxidation method, which achieved a cadmium recovery rate of 98.96%, but required an acid concentration of 100 g / L, 170°C, an oxygen pressure of 2.0 MPa, and a temperature of 100 °C. Operating under high liquid-to-solid ratios (mL / g) requires stringent equipment and results in unsustainable energy consumption. In contrast, water leaching, with its simple process and environmental friendliness, is more aligned with clean production priorities. However, the leaching rate of insoluble cadmium compounds in fly ash is extremely low under mild conditions, resulting in low efficiency in existing water leaching techniques. For example, patent CN201810791143.7 discloses a method for recovering cadmium from fly ash in a bottom-blown furnace of lead smelting. At temperatures between 25°C and 70°C, a liquid-to-solid ratio of 3:1 to 4:1, and a leaching time of 2 hours, the cadmium leaching rate is 68.63% to 86.88%. Patent CN201210290669.X discloses a method for recovering cadmium from fly ash in a bottom-blown furnace. At temperatures between 0°C and 60°C, a liquid-to-solid ratio of 1:1 to 4:1, and a leaching time of 1 to 4 hours, the cadmium leaching rate is 81.94% to 90.09%. Even with hot water-enhanced leaching (CN103572061A, 75-85°C, liquid-to-solid ratio 4-5:1, 3-4 hours), energy consumption increases significantly without achieving substantial efficiency improvements. Therefore, developing a synergistic technology for efficient cadmium leaching and lead stabilization under mild conditions has become a key breakthrough in the resource utilization of complex cadmium-containing soot. Summary of the Invention

[0004] In response to the technical bottlenecks of existing cadmium leaching processes such as high energy consumption, low efficiency and serious environmental pollution, the present invention provides a method for leaching cadmium from bottom-blown furnace ash based on ultrasonic cavitation activation-hydrogen peroxide directional oxidation. The method utilizes the synergistic mechanism of ultrasonic cavitation activation-hydrogen peroxide directional oxidation to stimulate H2O2 to produce hydroxyl radicals, establish selective conversion paths of CdS→CdSO4 (soluble) and PbSO3→PbSO4 (stable precipitation), dissociate particle agglomerates, and break up mineral coatings, thereby significantly reducing the reaction activation energy and transforming the control steps of the entire leaching process from mixing control to simple diffusion control. In this way, efficient leaching of cadmium and stable solidification of lead are simultaneously achieved under green conditions of room temperature and neutrality without the need for external acid and alkali, solving the industry problems of high energy consumption, strong corrosion, heavy pollution and difficulty in coordinated optimization of "cadmium extraction" and "lead solidification" of traditional high-temperature and high-acid cadmium leaching technology.

[0005] A method for leaching cadmium from bottom-blown furnace ash based on ultrasonic cavitation activation-hydrogen peroxide directional oxidation, the specific steps are as follows: The flue ash from the bottom-blown furnace of lead smelting is added to water, and the oxidant hydrogen peroxide is added to form an oxidative leaching system. The oxidative leaching system is subjected to ultrasonic leaching at room temperature and neutral conditions to obtain a cadmium-containing solution and a high-lead leaching slag. Specifically, the ultrasonic cavitation activation-hydrogen peroxide directional oxidation synergistic mechanism is utilized to stimulate H2O2 to produce hydroxyl radicals, establish selective conversion pathways from CdS to soluble CdSO4 and from PbSO3 to stable precipitated PbSO4, dissociate particle agglomerates, break up the mineral coating, reduce the reaction activation energy, and transform the control steps of the entire leaching process from mixing control to simple diffusion control, thereby simultaneously achieving cadmium leaching and lead stabilization solidification.

[0006] Calculated by mass percentage, the cadmium content in the lead smelting bottom-blown furnace ash is 10-22%, the lead content is 38-52%, and the sulfur content is 8-18%; the main phases of cadmium are cadmium sulfate, cadmium sulfite and cadmium sulfide, and the main phases of lead are lead sulfate and lead sulfite.

[0007] Preferably, the particle size of the lead smelting bottom-blown furnace ash is 0.3~70μm.

[0008] Preferably, the liquid-solid ratio of water to lead smelting bottom-blown furnace ash is 2-3:1 in mL:g, the liquid-solid ratio of hydrogen peroxide to lead smelting bottom-blown furnace ash is 0.05-0.15:1 in mL:g, the ultrasonic power is 300-500 W, and the leaching time is 20-40 min.

[0009] The beneficial effects of the present invention are: (1) The present invention utilizes the synergistic mechanism of ultrasonic cavitation activation and hydrogen peroxide directional oxidation at room temperature and neutral conditions without the need for external acid to achieve a cadmium leaching rate of ≥92.5% and a lead solidification rate of ≥97%, thereby solving the problem of strong acid waste liquid generated by traditional processes. The process of the present invention is clean, has mild operating conditions, relatively simple equipment requirements, and is easy to implement industrial applications. (2) The present invention utilizes ultrasound to synergistically activate hydrogen peroxide, significantly reducing the reaction activation energy, achieving efficient leaching of Cd at room temperature and reducing energy consumption; (3) The present invention establishes directional conversion pathways of CdS→CdSO4 and PbSO3→PbSO4, which not only efficiently leaches cadmium but also achieves stable solidification of lead, effectively inhibits lead dissolution, and simplifies the subsequent cadmium separation and enrichment process; (4) The present invention simultaneously optimizes the Cd leaching rate and the Pb solidification rate by precisely controlling the ultrasonic parameters (power 300-500 W, time 20-40 min), liquid-solid ratio (2:1-3:1) and H2O2 dosage (0.05-0.15 mL / g ash), thus solving the pollution and energy consumption problems caused by the traditional high-acidity and high-temperature process. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 This is a comparison chart of the effects of ultrasonic cavitation activation-hydrogen peroxide directional oxidation leaching and conventional hydrogen peroxide leaching under different conditions; Figure 2 This is the XRD comparison of the slag from ultrasonic cavitation activation-hydrogen peroxide directional oxidation leaching and conventional hydrogen peroxide leaching in Example 1; Figure 3 This is the change of CdS under the action of ultrasonic activated hydrogen peroxide in Example 1; Figure 4 This is the XRD analysis diagram of the residue after ultrasonic cavitation activation-hydrogen peroxide directional oxidation leaching for 15 minutes in Example 1; Figure 5 This is the case of ultrasonically promoting hydrogen peroxide to produce hydroxyl radicals in Example 1; Figure 6 This is Example 1, which shows the effect of ultrasound on the dispersion of ash particles in a bottom-blown furnace for lead smelting. DETAILED DESCRIPTION

[0011] The present invention will be further described in detail below in conjunction with specific embodiments, but the protection scope of the present invention is not limited to the contents described above.

[0012] Example 1: In the lead smelting bottom-blown furnace ash of this example, the cadmium content is 11.81 wt.%, the lead content is 41.51 wt.%, and the sulfur content is 11.81 wt.%. Among them, the cadmium exists mainly in the form of cadmium sulfate, cadmium sulfite, and cadmium sulfide, and the lead exists mainly in the form of lead sulfate and lead sulfite. A method for leaching cadmium from bottom-blown furnace ash based on ultrasonic cavitation activation-hydrogen peroxide directional oxidation, the specific steps are as follows: Lead smelting bottom-blown furnace fly ash (particle size 0.3-70 μm) was added to water (liquid-to-solid ratio of water to lead smelting bottom-blown furnace fly ash, mL:g, was 2:1). Hydrogen peroxide (liquid-to-solid ratio of hydrogen peroxide to lead smelting bottom-blown furnace fly ash, mL:g, was added as an oxidizing agent (no external acid or base was required). The oxidizing leaching system was subjected to ultrasonic leaching at room temperature and neutral conditions (ultrasonic power of 360 W, leaching time of 20 min), yielding a cadmium-containing solution and high-lead leaching residue. In this example, the leaching rate of cadmium was 96.76%, and the solidification rate of lead was 97.4%; Under the same conditions, ultrasonic cavitation activation-hydrogen peroxide directional oxidation leaching and conventional hydrogen peroxide (no ultrasound) leaching were compared. The effects of ultrasonic cavitation activation-hydrogen peroxide directional oxidation leaching and conventional hydrogen peroxide leaching under different conditions are shown in Figure 2. Figure 1 , utilizing the synergistic mechanism of ultrasonic cavitation activation and hydrogen peroxide directional oxidation to stimulate H2O2 to produce hydroxyl radicals, establish selective conversion pathways of CdS→CdSO4 (soluble) and PbSO3→PbSO4 (stable precipitation), dissociate particle agglomerates, and break up mineral coatings, significantly reducing the reaction activation energy and transforming the control steps of the entire leaching process from mixing control to simple diffusion control. Thus, efficient cadmium leaching and stable lead solidification are simultaneously achieved under green conditions of room temperature and neutrality without the need for external acid or alkali. Under the same conditions of this embodiment, conventional hydrogen peroxide (no ultrasound) leaching achieved a cadmium leaching rate of only 88.57%, 8.19% lower than the ultrasonically activated hydrogen peroxide process, and the lead solidification rate was only 96.7%. The XRD comparison of the slag from ultrasonic cavitation activation-hydrogen peroxide directional oxidation leaching and conventional hydrogen peroxide leaching in this example is shown in Figure 2 The lead content in the leachate of ultrasonic cavitation activation-hydrogen peroxide directional oxidation leaching and conventional hydrogen peroxide leaching at different leaching times is shown in Table 1. Table 1 Lead content in leachate under different leaching conditions (mg / L)

[0013] ; After conventional hydrogen peroxide leaching, obvious CdS and CdSO3 diffraction peaks remained, indicating that they were not completely converted into soluble CdSO4, which is the fundamental reason for the low cadmium leaching rate. At the same time, the residual PbSO3 peak suggests the risk of lead dissolution. As shown in Table 1, when the leaching time was 20 minutes, the lead content in the leachate of conventional hydrogen peroxide leaching reached 2307 mg / L. However, after ultrasonic cavitation activation-hydrogen peroxide directional oxidation leaching, the characteristic peaks of CdS and CdSO3 completely disappeared, confirming that the ultrasonic effect thoroughly promoted the conversion of CdS and CdSO3 to CdSO4. The PbSO3 peak disappeared and the PbSO4 peak increased, indicating that ultrasound simultaneously enhanced the solidification of lead into stable PbSO4. As shown in Table 1, the lead content in the leachate of ultrasonic cavitation activation-hydrogen peroxide directional oxidation leaching was only 19~78 mg / L, effectively inhibiting the dissolution of lead. The changes of CdS under the action of ultrasonic activated hydrogen peroxide are shown in Figure 3 The oxidation process of CdS shows obvious stage characteristics: the solution color changes from dark yellow (CdS) to turbid light yellow, and finally reaches a clear state. The color evolution directly reflects the CdS → S 0 → CdSO3→ CdSO4 stepwise oxidation pathway; the key intermediates were verified by various characterization methods. After 15 min of reaction, the turbid light yellow solution indicated that elemental sulfur (S 0 ) formation; XRD analysis of the residue after ultrasonic cavitation activation-hydrogen peroxide directional oxidation leaching for 15 minutes is shown in Figure 4 , S was clearly detected in the residue 0 The characteristic peak of CdSO3, combined with the change in solution turbidity, confirmed the presence of colloidal S 0 When the reaction was completed (20 min), IC analysis showed that sulfate (SO4 2- ) conversion rate>99% (29.94 mg / L) and sulfite (SO3 2- The residual amount of ) was extremely low (214.3 μg / L), which proved that the reaction was finally converted into the target product CdSO4 efficiently. By precisely controlling the ultrasonic parameters (power 360W, time 20min), liquid-solid ratio (2:1) and H2O2 dosage (0.1mL / g soot), the reaction was ensured to be efficiently advanced to the final soluble product CdSO4, avoiding the intermediate products (such as S 0 , CdSO3) accumulation resulting in efficiency loss; Ultrasound promotes the generation of hydroxyl radicals from hydrogen peroxide. Figure 5 , a significant ·OH characteristic peak (1:2:2:1) was observed only in the ultrasonically activated H2O2 system, confirming that ultrasound can strongly promote the decomposition of H2O2 to produce highly active ·OH radicals (conventional H2O2 only produces a weak signal); Effect of ultrasound on the dispersion of ash particles in bottom-blown furnaces of lead smelting Figure 6 Ultrasonic treatment effectively breaks up particle agglomerates and mineral coatings, greatly increasing the contact efficiency between insoluble phases (such as CdS) and reactants (·OH / H2O2); The activation energy of conventional hydrogen peroxide leaching calculated using the Arrhenius equation is 16.198 kJ / mol, which is in the transition range of 13–40 kJ / mol. This indicates that the conventional hydrogen peroxide leaching process is controlled by a mixture of diffusion and chemical reaction. This is consistent with the analysis that conventional hydrogen peroxide leaching has difficulty in effectively destroying inclusions and inhibiting the formation of agglomerates, leading to mass transfer barriers. It also suggests that its chemical reactivity towards target substances (such as CdSO3 and CdS) is insufficient, making it difficult for hydrogen peroxide to effectively carry out oxidation reactions. The calculated activation energy of ultrasonically activated hydrogen peroxide leaching is only 3.389 kJ / mol, which is far below the upper limit of diffusion control (12.55 kJ / mol), confirming that diffusion control has become the rate-determining step of the reaction. Ultrasonic intervention dramatically reduces the activation energy of the leaching reaction from 16.198 kJ / mol to 3.389 kJ / mol, shifting the control step from mixing control to diffusion control, significantly accelerating the leaching kinetics.

[0014] Example 2: The fly ash from the lead smelting bottom-blown furnace in this example is the same as that in Example 1; A method for leaching cadmium from bottom-blown furnace ash based on ultrasonic cavitation activation-hydrogen peroxide directional oxidation, the specific steps are as follows: Lead smelting bottom-blown furnace fly ash (particle size 0.3-70 μm) was added to water (liquid-to-solid ratio of water to lead smelting bottom-blown furnace fly ash, mL:g, was 2:1). Hydrogen peroxide (liquid-to-solid ratio of hydrogen peroxide to lead smelting bottom-blown furnace fly ash, mL:g, was added as an oxidizing agent (no external acid or alkali required). The oxidizing leaching system was subjected to ultrasonic leaching at room temperature and neutral conditions (ultrasonic power 300 W, leaching time 30 min), yielding a cadmium-containing solution and high-lead leaching residue. In this embodiment, the leaching rate of cadmium is 93.8%, and the solidification rate of lead is 97.2%.

[0015] Example 3: The fly ash from the lead smelting bottom-blown furnace in this example is the same as that in Example 1; A method for leaching cadmium from bottom-blown furnace ash based on ultrasonic cavitation activation-hydrogen peroxide directional oxidation, the specific steps are as follows: Lead smelting bottom-blown furnace fly ash (particle size 0.3-70 μm) was added to water (liquid-to-solid ratio of water to lead smelting bottom-blown furnace fly ash, mL:g, was 2:1). Hydrogen peroxide (liquid-to-solid ratio of hydrogen peroxide to lead smelting bottom-blown furnace fly ash, mL:g, was added as an oxidizing agent (no external acid or alkali required). Ultrasonic leaching was performed in the oxidizing leaching system at room temperature under neutral conditions (ultrasonic power 400 W, leaching time 40 min), yielding a cadmium-containing solution and high-lead leaching residue. In this embodiment, the leaching rate of cadmium is 96.68%, and the solidification rate of lead is 97.9%.

[0016] Example 4: In the lead smelting bottom-blown furnace ash of this example, the cadmium content is 20.53 wt.%, the lead content is 38.52 wt.%, and the sulfur content is 16.35 wt.%. Among them, the cadmium exists mainly in the form of cadmium sulfate, cadmium sulfite, and cadmium sulfide, and the lead exists mainly in the form of lead sulfate and lead sulfite. A method for leaching cadmium from bottom-blown furnace ash based on ultrasonic cavitation activation-hydrogen peroxide directional oxidation, the specific steps are as follows: Lead smelting bottom-blown furnace fly ash (particle size 0.3-70 μm) was added to water (liquid-to-solid ratio of water to lead smelting bottom-blown furnace fly ash, mL:g, 3:1) and hydrogen peroxide (liquid-to-solid ratio of hydrogen peroxide to lead smelting bottom-blown furnace fly ash, mL:g, 0.15:1) as an oxidative leaching system (no external acid or alkali required). The oxidative leaching system was subjected to ultrasonic leaching at room temperature and neutral conditions (ultrasonic power 500 W, leaching time 20 min), producing a cadmium-containing solution and high-lead leaching residue. In this embodiment, the leaching rate of cadmium is 95.12%, and the solidification rate of lead is 98.3%.

[0017] Example 5: In the lead smelting bottom-blown furnace ash of this example, the cadmium content is 16.93 wt.%, the lead content is 51.1 wt.%, and the sulfur content is 13.69 wt.%. Among them, the cadmium mainly exists in the form of cadmium sulfate, cadmium sulfite, and cadmium sulfide, and the lead mainly exists in the form of lead sulfate and lead sulfite. A method for leaching cadmium from bottom-blown furnace ash based on ultrasonic cavitation activation-hydrogen peroxide directional oxidation, the specific steps are as follows: Lead smelting bottom-blown furnace fly ash (particle size 0.3-70 μm) was added to water (the liquid-to-solid ratio of water to lead smelting bottom-blown furnace fly ash, mL:g, was 2.5:1). Hydrogen peroxide (the liquid-to-solid ratio of hydrogen peroxide to lead smelting bottom-blown furnace fly ash, mL:g, was added as an oxidizing agent (no external acid or alkali required). The oxidizing leaching system was subjected to ultrasonic leaching at room temperature and neutral conditions (ultrasonic power 400 W, leaching time 30 min), producing a cadmium-containing solution and high-lead leaching residue. In this embodiment, the leaching rate of cadmium is 92.98%, and the solidification rate of lead is 97.4%.

[0018] The above describes the specific embodiments of the present invention in detail, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in this field without departing from the scope of the present invention.

Claims

1. A method for leaching cadmium from bottom-blown furnace ash based on ultrasonic cavitation activation-hydrogen peroxide directional oxidation, characterized in that: The specific steps are as follows: The flue ash from the bottom-blown furnace of lead smelting is added to water, and the oxidant hydrogen peroxide is added to form an oxidative leaching system. The oxidative leaching system is subjected to ultrasonic leaching at room temperature and neutral conditions to obtain a cadmium-containing solution and a high-lead leaching slag. Specifically, the ultrasonic cavitation activation-hydrogen peroxide directional oxidation synergistic mechanism is utilized to stimulate H2O2 to produce hydroxyl radicals, establish selective conversion pathways from CdS to soluble CdSO4 and from PbSO3 to stable precipitated PbSO4, dissociate particle agglomerates, break up the mineral coating, reduce the reaction activation energy, and transform the control steps of the entire leaching process from mixing control to simple diffusion control, thereby simultaneously achieving cadmium leaching and lead stabilization solidification.

2. The method for leaching cadmium from bottom-blown furnace ash based on ultrasonic cavitation activation-hydrogen peroxide directional oxidation according to claim 1, characterized in that: Calculated by mass percentage, the cadmium content in the lead smelting bottom-blown furnace ash is 10-22%, the lead content is 38-52%, and the sulfur content is 8-18%; the main phases of cadmium are cadmium sulfate, cadmium sulfite and cadmium sulfide, and the main phases of lead are lead sulfate and lead sulfite.

3. The method for leaching cadmium from bottom-blown furnace ash based on ultrasonic cavitation activation-hydrogen peroxide directional oxidation according to claim 1, characterized in that: The particle size of the ash from the bottom-blown furnace of lead smelting is 0.3~70μm.

4. The method for leaching cadmium from bottom-blown furnace ash based on ultrasonic cavitation activation-hydrogen peroxide directional oxidation according to claim 1, characterized in that: The liquid-solid ratio of water to lead smelting bottom-blown furnace ash is 2~3:1 in mL:g, the liquid-solid ratio of hydrogen peroxide to lead smelting bottom-blown furnace ash is 0.05~0.15:1 in mL:g, the ultrasonic power is 300~500 W, and the leaching time is 20~40 min.

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