Method for strengthening secondary zinc oxide smoke dust leaching through ultrasonic waves and ascorbic acid

Abstract

The invention discloses a method for strengthening secondary zinc oxide smoke dust leaching through ultrasonic waves and ascorbic acid. The method comprises the steps that secondary zinc oxide smoke dust is dried and then mixed with a sulfuric acid solution; by controlling the liquid-solid ratio, separation of silica gel and other adsorptive coprecipitates can be effectively inhibited, and the leaching rate of zinc can be increased; ascorbic acid is added for reduction leaching; the ascorbic acid reduces Fe (III) of zinc ferrite in the secondary zinc oxide smoke dust into Fe (II), the structure of the zinc ferrite is destroyed, and zinc ions are released in the leaching process, so that the leaching rate of zinc is increased; carrying out ultrasonic-assisted intensified leaching for 10-30 minutes, and filtering to obtain a leaching solution and leaching residues; under the action of ultrasonic waves, liquid and solid-liquid interfaces are damaged, and tiny cavitation bubbles are generated; the shear stress generated when the cavitation bubbles are broken penetrates through ion lattices of a product layer to be penetrated through ultrasonic waves, local high temperature and high pressure are caused, finally the granularity of the secondary zinc oxide smoke dust is reduced, ascorbic acid and sulfuric acid can permeate into pores and cracks, and efficiency is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of hydrometallurgy and relates to a method for leaching zinc oxide smoke. Background Art

[0002] Against the backdrop of the rapid development of the global steel industry, the continuous increase in steel production has promoted rapid economic growth, but it has also brought environmental challenges, especially the large-scale generation of secondary zinc oxide dust. According to statistics, secondary zinc oxide dust generated in the steel production process accounts for about 3% to 4% of the total crude steel output. If not handled properly, it will not only occupy a large amount of land resources, but may also cause serious pollution to the soil, water bodies and atmospheric environment, especially the heavy metal elements such as lead and cadmium contained in it. The environmental pollution risk cannot be ignored. However, secondary zinc oxide dust also contains rich resource value, especially zinc and iron. These elements, as recyclable secondary resources, are of great significance to the construction of a resource-saving society. Zinc plays an important role in many fields such as chemical industry, electroplating, and battery manufacturing. Its efficient recycling and utilization are crucial to promoting the green and sustainable development of related industries.

[0003] Traditionally, the treatment methods for zinc oxide dust mainly include landfill, pyrometallurgy and hydrometallurgy. Although these methods each have their own application scenarios, given the unique advantages of hydrometallurgical technology in treating complex metal oxides, it has become the mainstream choice for treating zinc oxide dust in the industry. Hydrometallurgical technology aims to extract valuable metal elements from dust through chemical means such as acid leaching or alkaline leaching. During the oxidative roasting process of zinc oxide dust, most of the zinc element will be converted into ZnO, but some zinc will combine with impurities such as iron to form zinc ferrite, which is difficult to treat. This chemical conversion process greatly limits the leaching efficiency of zinc by traditional acid leaching and alkaline leaching processes, resulting in unsatisfactory resource recovery rates.

[0004] When deeply discussing the field of zinc oxide dust hydrometallurgy, the technical bottlenecks encountered by the traditional acid leaching process are particularly prominent, and innovative solutions are urgently needed to break through the existing limitations. Specifically, these technical difficulties are concentrated in two aspects: (1) Conventional leaching methods generally face the problem of long time and high energy consumption. This defect not only increases production costs, but also limits the improvement of production efficiency, posing a significant obstacle to large-scale industrial applications.

[0005] (2) The zinc in zinc oxide dust exists in a variety of forms, with zinc oxide and zinc ferrite as the main components. Zinc ferrite has a stable chemical structure and hardly reacts during conventional acid leaching, which results in some zinc resources being locked in difficult-to-treat solid waste, restricting the zinc leaching rate and resource recovery efficiency. This situation not only causes a waste of resources, but also increases the risk of environmental pollution. Summary of the invention

[0006] The purpose of the present invention is to deeply extract the zinc element in zinc oxide dust, aiming to effectively solve the leaching problem of difficult-to-treat compounds such as zinc ferrite by optimizing leaching conditions, introducing ultrasound and reducing agents, and significantly improve the leaching rate of zinc, thereby achieving high-value utilization of zinc oxide dust resources and reducing environmental pollution.

[0007] A method for strengthening zinc oxide smoke leaching by ultrasonic and ascorbic acid comprises the following steps: (1) After drying the zinc oxide fume, mix it with sulfuric acid solution; by controlling the liquid-to-solid ratio, the precipitation of silica gel and other adsorptive co-precipitates can be effectively inhibited, which is beneficial to improving the zinc leaching rate.

[0008] (2) Add ascorbic acid for reduction leaching; ascorbic acid reduces Fe(III) of zinc ferrite in zinc oxide dust to Fe(II), destroys the structure of zinc ferrite, releases zinc ions during the leaching process, and thus increases the leaching rate of zinc.

[0009] (3) Ultrasonic-assisted enhanced leaching for 10 to 30 minutes, and the leaching solution and leaching residue are obtained by filtration; under the action of ultrasound, the liquid and solid-liquid interface is destroyed, and tiny cavitation bubbles are generated. The shear stress generated when these cavitation bubbles burst penetrates the ionic lattice of the product layer to be penetrated through ultrasound, resulting in local high temperature and high pressure, and ultimately reducing the particle size of the secondary zinc oxide smoke. Ultrasonic waves destroy the surface of the smoke, causing the entire block to break or disperse into parts, which is conducive to the penetration of ascorbic acid and sulfuric acid into pores and cracks, accelerating the leaching process, shortening the reaction time, increasing the reaction rate, and improving efficiency.

[0010] According to the above scheme, the zinc in the secondary zinc oxide smoke mainly exists in the form of zinc oxide, zinc sulfide and zinc ferrite.

[0011] According to the above scheme, the drying temperature of zinc oxide fume in step (1) is 80-100°C.

[0012] According to the above scheme, the concentration of the sulfuric acid solution in step (1) is 0.5 to 2.5 mol / L.

[0013] According to the above scheme, the liquid-to-solid ratio of the sulfuric acid solution to the secondary zinc oxide smoke in step (1) is (5-8): 1 mL / g.

[0014] In the optimized scheme, step (1) uses a sulfuric acid solution with a concentration of 2 mol / L and a liquid-to-solid ratio of 7:1 mL / g.

[0015] According to the above scheme, the concentration of ascorbic acid in the leaching solution in step (2) is 0.02~1.0 mol / L.

[0016] According to the above scheme, the ultrasonic power used in step (3) is 300 to 800 W.

[0017] According to the above scheme, the ultrasonic frequency used in step (3) is 19.5~25KHz.

[0018] According to the above scheme, the time for ultrasonic-assisted enhanced leaching in step (3) is 10 to 30 minutes.

[0019] By introducing ultrasonic technology and utilizing its unique cavitation effect and chemical effect, the mass transfer and mixing between reactants can be accelerated at the microscopic level, thereby significantly shortening the reaction time and reducing energy consumption. The vibration of ultrasonic waves can break the local equilibrium of the reaction system, promote the exposure of active sites and the effective contact of reactants, and thus accelerate the chemical reaction.

[0020] Ascorbic acid is creatively added as a reducing agent. Under certain conditions, this substance can effectively decompose the zinc ferrite structure in zinc oxide dust and convert it into a form that is more soluble in acid, thereby significantly improving the zinc leaching rate. The introduction of ascorbic acid not only solves the problem of zinc ferrite being difficult to handle, but also further optimizes the overall performance of the leaching system and achieves efficient recycling and utilization of resources.

[0021] Compared with the prior art, the present invention has the following beneficial effects: The invention adds ascorbic acid as a reducing agent, which can reduce trivalent iron to divalent iron, promote the decomposition of zinc ferrite in zinc oxide dust, thereby increasing the zinc leaching rate, so that zinc resources that are difficult to extract by conventional methods can be efficiently recovered. It not only broadens the application field of ascorbic acid, but also provides a new idea for the treatment of zinc oxide dust.

[0022] The cavitation effect induced by ultrasonic technology on the liquid and solid-liquid interface forms tiny cavitation bubbles. The instantaneous rupture of these bubbles produces strong shear stress and local high temperature and high pressure environment, which effectively refines the particle size of the raw materials and promotes the destruction of the solid surface. The present invention uses ultrasound to assist leaching to enhance the solution's penetration into the pores and cracks of the material, accelerates the material exchange and interfacial chemical reaction between the solid phase and the liquid phase, and thus improves the leaching efficiency.

[0023] After combining ultrasound with ascorbic acid, ultrasound can promote the full contact and reaction between ascorbic acid and sulfuric acid and zinc oxide dust, so that the reducing effect of ascorbic acid can be more fully exerted, shorten the reaction time, increase the leaching rate, and make the entire treatment process more efficient.

[0024] The recovery rate of metallic zinc in the present invention is significantly increased from the current industry average level of about 90% to more than 98%, and environmental pollution and resource waste are reduced, making an important contribution to the sustainable development of related industries. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solution and beneficial technical effect of the present invention clearer, the present invention is further described in detail below in conjunction with specific implementation methods. It should be understood that the specific implementation methods described in this specification are only for explaining the present invention, not for limiting the present invention.

[0026] Unless otherwise specified, the raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0027] To avoid repetition, some raw materials or parameters involved in the following embodiments and comparative examples of the present invention are described as follows: the secondary zinc oxide dust used in all embodiments of the present invention is the same. After testing, the main chemical components of the secondary zinc oxide dust used are Zn 20%~60%, Fe 1%~15%, K 5~10%, Cr 3%~5%, S 2%~5%, Ca 2%~5%, Al 0~1%, Pb 0~1%, and the remainder is other element oxides and ignition loss.

[0028] Example 1 A method for ultrasonic-ascorbic acid enhanced zinc oxide dust leaching comprises the following steps: (1) Weigh 20 g of dried zinc oxide dust.

[0029] (2) 20 g of zinc oxide fume was added into a 250 mL double-layer glass reactor containing a sulfuric acid solution with a molar concentration of 2.0 mol / L at a liquid-to-solid ratio of 7:1 ml / g.

[0030] (3) Add 1.0 mol / L ascorbic acid to the solution.

[0031] (4) After mixing, ultrasonic waves of different powers are applied and the leaching reaction is carried out at a temperature of 90°C for 30 minutes.

[0032] (5) After leaching is completed, the mud is taken out and filtered through three layers of filter paper to obtain the leachate and leach residue through liquid-solid separation.

[0033] The zinc content of the leaching solution was tested, and the zinc leaching rate under different ultrasonic powers was calculated as shown in Table 1.

[0034] Table 1

[0035] When ultrasonic energy is radiated to the solution system, the temperature and pressure gradients in the local area increase sharply, inducing micro-turbulence, which in turn triggers mechanical effects, chemical effects and cavitation effects. The cavitation effect is particularly critical, which causes the microbubbles to rupture, effectively thins the boundary layer of zinc oxide dust, and promotes the in-depth reaction. This series of effects optimizes the leaching process to a certain extent, shortens the reaction time, and improves the recovery efficiency of valuable metals, thereby realizing an energy-saving, environmentally friendly and high-efficiency metallurgical process. The experimental results show that when the ultrasonic power is lower than 600W, the zinc leaching rate increases with the increase of ultrasonic power. When the ultrasonic power rises to 600W, the zinc leaching rate reaches the highest value of 98.87%. However, as the ultrasonic power increases further, the zinc leaching rate shows a downward trend. This phenomenon can be attributed to the saturation effect of cavitation intensity: when the power increases to a certain threshold, the cavitation reaches its maximum efficiency. If the power continues to increase, it will trigger the generation of a large number of non-functional bubbles. These bubbles have no substantial contribution to the leaching process, but interfere with the effective reaction, thereby reducing the leaching rate of zinc.

[0036] Comparative Example 1 (1) Weigh 20 g of dried zinc oxide dust.

[0037] (2) 20 g of zinc oxide fume was added into a 250 mL double-layer glass reactor containing a sulfuric acid solution with a molar concentration of 2.0 mol / L at a liquid-to-solid ratio of 7:1 ml / g.

[0038] (3) Add 1 mol / L ascorbic acid to the solution.

[0039] (4) The leaching reaction was controlled at a temperature of 90°C for 30 minutes.

[0040] (5) After leaching is completed, the mud is taken out and filtered through three layers of filter paper to obtain the leachate and leach residue through liquid-solid separation.

[0041] The same method as in Example 1 was used except that ultrasound was not used. The zinc content of the leaching solution was tested and the zinc leaching rate was calculated to be 93.75%.

[0042] Example 2 A method for ultrasonic-ascorbic acid enhanced zinc oxide dust leaching comprises the following steps: (1) Weigh 20 g of dried zinc oxide dust.

[0043] (2) 20 g of zinc oxide fume was added into a 250 mL double-layer glass reactor containing a sulfuric acid solution with a molar concentration of 2.0 mol / L at a liquid-to-solid ratio of 7:1 ml / g.

[0044] (3) Add different concentrations of ascorbic acid to the solution.

[0045] (4) After mixing, add 600W ultrasonic wave and control the leaching reaction at 90°C for 30 minutes.

[0046] (5) After leaching is completed, the mud is taken out and filtered through three layers of filter paper to obtain the leachate and leach residue through liquid-solid separation.

[0047] The zinc content of the leaching solution was tested, and the zinc leaching rate at different ascorbic acid concentrations was calculated as shown in Table 1.

[0048] Example 2 Zinc leaching rate

[0049] Within a certain concentration range, the increase in ascorbic acid concentration will promote the growth of zinc leaching rate. This is mainly due to the reducing property of ascorbic acid, which can reduce zinc ferrite in zinc oxide dust and destroy the original structure of zinc ferrite, so that zinc ions can be released more effectively in the subsequent leaching process. As the concentration of the reducing agent ascorbic acid gradually increases, the zinc leaching rate also increases, until it reaches a peak value at a concentration of 0.08 mol / L, at which time the zinc leaching rate is as high as 98.96%. However, when the concentration of ascorbic acid exceeds this optimal point, its further improvement effect on the zinc leaching rate becomes no longer significant.

[0050] Comparative Example 2 (1) Weigh 20 g of dried zinc oxide dust.

[0051] (2) 20 g of zinc oxide fume was added into a 250 mL double-layer glass reactor containing a sulfuric acid solution with a molar concentration of 2.0 mol / L at a liquid-to-solid ratio of 7:1 ml / g.

[0052] (3) Add different concentrations of formic acid to the solution.

[0053] (4) After mixing, add 600W ultrasonic wave and control the leaching reaction at 90°C for 30 minutes.

[0054] (5) After leaching is completed, the mud is taken out and filtered through three layers of filter paper to obtain the leachate and leach residue through liquid-solid separation.

[0055] The zinc content of the leaching solution was tested, and the zinc leaching rate at different formic acid concentrations was calculated as shown in Table 2.

[0056] Example 2 Zinc leaching rate

[0057] Formic acid is an organic acid containing carboxyl and aldehyde groups, and the aldehyde group gives it reducing properties. Within a certain concentration range, the increase in formic acid concentration will promote the increase in zinc leaching rate. As the concentration of reducing agent formic acid increases to 0.1 mol / L, the zinc leaching rate reaches a peak of 94.07%. Further increasing the formic acid concentration, its further effect on the zinc leaching rate becomes less significant.

[0058] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. A method for leaching zinc oxide dust by ultrasonic and ascorbic acid, characterized in that The following steps are involved: (1) drying the zinc oxide dust and mixing it with sulfuric acid solution; (2) adding ascorbic acid for reduction leaching; (3) Ultrasonic-assisted enhanced leaching for 10 to 30 minutes, and the leaching solution and leaching residue were obtained by filtration.

2. The method for leaching zinc oxide dust by using ultrasound and ascorbic acid as claimed in claim 1, characterized in that The zinc in the secondary zinc oxide dust mainly exists in the form of zinc oxide, zinc sulfide and zinc ferrite.

3. The method for leaching zinc oxide dust by using ultrasound and ascorbic acid as claimed in claim 1, characterized in that The drying temperature of zinc oxide dust in step (1) is 80-100°C.

4. The method for leaching zinc oxide dust by using ultrasound and ascorbic acid as claimed in claim 1, characterized in that The concentration of the sulfuric acid solution in step (1) is 0.5 to 2.5 mol / L.

5. The method for strengthening zinc oxide dust leaching by ultrasonic and ascorbic acid as claimed in claim 1, characterized in that The liquid-to-solid ratio of the sulfuric acid solution in step (1) to the zinc oxide fume is (5-8): 1 mL / g.

6. The method for leaching zinc oxide dust by using ultrasound and ascorbic acid as claimed in claim 1, characterized in that In step (1), the concentration of the sulfuric acid solution used is 2 mol / L; the liquid-to-solid ratio of the sulfuric acid solution to the zinc oxide dust is 7:1 mL / g.

7. The method for leaching zinc oxide dust by using ultrasound and ascorbic acid as claimed in claim 1, characterized in that In step (2), the concentration of ascorbic acid in the leaching solution is 0.02-1.0 mol / L.

8. The method for leaching zinc oxide dust by using ultrasound and ascorbic acid as claimed in claim 1, characterized in that The ultrasonic power used in step (3) is 300 to 800 W.

9. The method for leaching zinc oxide dust by using ultrasound and ascorbic acid as claimed in claim 1, characterized in that The ultrasonic frequency used in step (3) is 19.5~25KHz.

10. The method for leaching zinc oxide dust by using ultrasound and ascorbic acid as claimed in claim 1, characterized in that The ultrasonic-assisted enhanced leaching time in step (3) is 10 to 30 minutes.

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