A method for recovering zinc, lead and silver from zinc-oxygen pressed slag by combining microbial leaching with chloride leaching

Abstract

The present invention discloses a method for recovering zinc, lead, and silver from zinc-oxygen press slag using a combination of microbial leaching and chloride leaching. This method simultaneously recovers zinc, lead, and silver from zinc-oxygen press slag through a process of crushing, slurry adjustment, acid balancing, bioleaching, solid-liquid separation, slurry adjustment, chloride leaching, and solid-liquid separation. The leaching rates for zinc, lead, and silver are ≥95%, ≥95%, and ≥90%, respectively. This method offers the advantages of simple process, environmental friendliness, ease of operation, and high recovery of valuable metals.

Description

Technical Field

[0001] The invention belongs to the technical field of hydrometallurgy and comprehensive utilization of zinc smelting solid waste, and particularly relates to a method for recovering zinc, lead and silver from zinc-oxygen pressed slag by combining microbial leaching with chloride salt leaching. Background Art

[0002] my country is a major zinc smelter and consumer, ranking first in the world in both production and consumption for many consecutive years. Zinc smelting primarily utilizes hydrometallurgical processes, with approximately 85% of zinc production coming from this process. With the continuous advancement of technology and equipment, the zinc oxygen pressure leaching process within the hydrometallurgical process is gaining widespread adoption due to its low pollution, wide raw material compatibility, and high recovery rates. However, after zinc concentrate undergoes oxygen pressure leaching and flotation desulfurization, a large amount of zinc oxygen pressure slag is produced. While some of this waste slag is recycled, the majority is stored, posing a significant environmental risk. Notably, the zinc oxygen pressure slag contains valuable metals such as zinc, lead, and silver, making it a solid waste resource with high comprehensive utilization value. Fully recovering the valuable metals in the zinc oxygen pressure slag will further alleviate my country's mineral resource shortage. Recycled zinc oxygen pressure slag can also be used as construction materials, achieving resource recycling, freeing up vast slag dumps, and alleviating environmental pollution.

[0003] Currently, treatment methods for valuable metals in zinc-oxygen slag include pyro-volatilization, chemical leaching, and flotation. These methods suffer from high energy consumption, large reagent consumption, and low recovery rates, which are contrary to the trend of sustainable socioeconomic development and energy conservation and emission reduction. The development of technologies for recovering valuable metals from zinc-oxygen slag must be comprehensive, efficient, environmentally friendly, and cost-effective. The diverse and high concentrations of valuable metals in zinc-oxygen slag, along with their varying states of occurrence and properties, make comprehensive recovery difficult with a single method. A combined two- or more-step approach is often required.

[0004] Therefore, it is imperative to seek an economical, reasonable and comprehensive method to recover valuable metals from zinc-oxygen slag. Summary of the Invention

[0005] In view of the shortcomings of the existing zinc-oxygen slag recovery process, the purpose of the present invention is to provide a method for recovering zinc, lead and silver in zinc-oxygen slag by combining microbial leaching with chloride salt leaching. This method can not only comprehensively recover the valuable metals in the zinc-oxygen slag, but also realize the recycling of the solution, providing a new idea for green environmental protection, high efficiency and energy saving, and comprehensive recovery of zinc, lead and silver in zinc-oxygen slag.

[0006] To achieve the above object, the present invention provides a method for recovering zinc, lead and silver from zinc-oxygen pressed slag by combining microbial leaching with chloride leaching, comprising the following steps:

[0007] 1) Crushing: Dry the zinc-oxygen pressed slag and grind it to less than 74 μm;

[0008] 2) Slurry preparation: the zinc-oxygen pressed slag after grinding in step 1) is prepared with deionized water into a slurry with a mass concentration of 5 to 30%, and then the prepared slurry is sterilized with high-pressure steam for 2 to 10 minutes and then cooled to room temperature;

[0009] 3) Acid balance: Use 50wt% sulfuric acid solution to adjust the pH value of the slurry to 1.0-3.0, and keep the pH stable for 24 hours;

[0010] 4) Bioleaching: sterilize the 9K culture medium with high-pressure steam for 2 to 10 minutes and cool to room temperature; then inoculate the 9K culture medium with 5 to 20 v / v% of leaching bacteria, adjust the pH value to 1.0 to 3.0 with 50 wt% sulfuric acid solution, and culture in a constant temperature shaking incubator for 10 to 50 days at a temperature of 20 to 45°C and a shaking speed of 140 to 200 rpm to obtain a bacterial solution in the logarithmic growth phase with a bacterial concentration of ≥1.0×10 8 / mL; inoculating the bacterial solution in the logarithmic growth phase into the slurry after acid balance in step 3) at an inoculum rate of 5 to 20 v / v% to obtain a zinc-oxygen slag microbial leaching system, placing the microbial leaching system in a constant temperature shaking incubator, controlling the temperature between 20 and 45 ° C, the oscillator speed at 140 to 200 rpm, and the bioleaching time for 10 to 50 days;

[0011] The leaching bacteria are highly efficient sulfur-oxidizing bacteria, the strain is classified as Acidithiobacillus thiooxidans Retech DW-Ⅱ, and the deposited unit is the General Microbiology Center of China Culture Collection Administration, located at No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing, Institute of Microbiology, Chinese Academy of Sciences, on September 10, 2014, with the deposit number CGMCC NO.9625.

[0012] 5) Solid-liquid separation: The microbial leaching system after bioleaching is filtered and separated to obtain a zinc-containing leachate and a microbial leaching residue. The microbial leaching residue is washed 3 to 4 times with deionized water, dried, and then ground to a size of less than 74 μm. The zinc-containing leachate is recovered by extraction-electrodeposition.

[0013] 6) Slurry preparation: adding chloride salt A and chloride salt B to deionized water to prepare a chloride salt solution containing chloride salt A at a mass concentration of 100-350 g / L and chloride salt B at a mass concentration of 10-30 g / L; using the chloride salt solution to prepare a slurry with a mass concentration of 5-30% by weight of the microbial leaching residue after grinding in step 5), and adjusting the pH value of the slurry to 0.5-5.0 using a 20 wt % hydrochloric acid solution;

[0014] 7) Chloride leaching and solid-liquid separation: the slurry after pH adjustment in step 6) is directly subjected to leaching and stirring, the leaching stirring speed is 100-500 rpm, the reaction time is 0.5-4 h, and the reaction temperature is 40-95° C. After the leaching is completed, the chloride leaching residue and the lead-silver leachate are immediately filtered while hot to obtain the chloride leaching residue; the chloride leaching residue is washed 3-4 times with a chloride salt A solution containing a mass concentration of 100-350 g / L at 70-100° C., and then washed 3-4 times with deionized water, and then the chloride leaching residue is dried; the lead-silver leachate is replaced with lead flakes to obtain coarse silver powder and a replaced solution, and the replaced solution is slowly cooled and crystallized to obtain lead chloride crystals; the lead chloride crystals and the chloride leaching solution are separated by filtration, and the chloride A and chloride B are supplemented to the chloride solution to reach the mass concentration of the chloride solution, and then returned to the chloride leaching for recycling.

[0015] Here, the chloride salt A solution (70-100°C) used to wash the chloride salt leaching residue is used to wash the lead and silver remaining in the chloride salt leaching residue after leaching; then deionized water is used to wash the chloride salt remaining in the chloride salt leaching residue to reduce the influence of the components adsorbed in the chloride salt leaching residue on the yield calculation.

[0016] Furthermore, the zinc-oxygen slag particle size in step 1) is -30 μm, accounting for more than 85%.

[0017] Here, -30 μm means less than 30 μm.

[0018] Furthermore, the mass concentration of the slurry in step 2) is 5-25%, and the sterilization time is 4-8 minutes.

[0019] Furthermore, the formula of the 9K culture medium described in step 3) is: (NH4)2SO4 3.0g; KCl 0.10g; K2HPO4 0.50g; MgSO4.7H2O 0.50g; Ca(NO3)2 0.01g; FeSO4.7H2O 44.40g and distilled water 1000.00mL.

[0020] Furthermore, the pH value of the solution described in step 4) is adjusted to 1.5-3.0 using a 50wt% sulfuric acid solution, the inoculation amount is 5-15% by volume, and the culture is cultured at a constant temperature of 25-45°C for 10-30 days at an oscillator speed of 150-200 rpm to obtain a bacterial solution in the logarithmic growth phase.

[0021] Furthermore, the bacterial concentration in the solution after inoculation in step 4) is 1.0×10 7 ~2.0×10 7 pieces / mL.

[0022] Furthermore, the temperature of the microbial leaching system in step 5) is controlled at 25-45° C., the rotation speed of the oscillator is 150-200 rpm, and the leaching time is 10-40 days.

[0023] Furthermore, the chloride salt A in step 6) is one or more of NaCl, KCl, FeCl3, and MgCl2, and the chloride salt B is one or two of CaCl2 and BaCl2.

[0024] Furthermore, in the chloride solution prepared in step 6), the mass concentration of chloride salt A is 150-350 g / L, and the mass concentration of chloride salt B is 15-30 g / L. The mass concentration of the slurry of the microbial leaching residue prepared using the chloride solution is 5-20%, and the pH value of the slurry is adjusted to a range of 0.5-3.0 using a 20 wt% hydrochloric acid solution.

[0025] Furthermore, the reaction temperature of the chloride leaching of microorganism leaching residue in step 7) is 50-90° C., the leaching stirring speed is 150-450 rpm, and the reaction time is 0.5-3 h.

[0026] The chloride leaching method in chemical leaching can simultaneously and efficiently leach heavy metal lead and precious metal silver. However, since the zinc, lead and silver in the zinc-oxygen slag are partially present in the form of sulfides, it is not conducive to chloride leaching. The present invention uses a method for leaching zinc, lead and silver in the zinc-oxygen slag using a microorganism-chloride combination. First, the zinc sulfide in the zinc-oxygen slag is oxidized to zinc sulfate by the oxidation action of sulfur-oxidizing bacteria for leaching. The oxidation action of the sulfur-oxidizing bacteria also causes the lead sulfide and silver sulfide to be oxidized and converted into sulfates that are more easily reactive with chloride. Then, chloride is used to leach the lead and silver in the microbial leaching slag.

[0027] Among them, chloride salt A provides a high concentration of chloride salt environment, and chloride salt B provides chloride ions that react with lead and silver. If it is a combination of different compounds, the selected compounds can be combined in any proportion.

[0028] The main reaction principle is as follows:

[0029] PbSO4+MeCl2→PbCl2+MeSO4↓Me=Ba, Ca (1)

[0030]

[0031] Ag2SO4+MeCl2→2AgCl+MeSO4↓Me=Ba,Ca (3)

[0032]

[0033] From the above reaction formula, we can see that in the reaction, Me(Ca 2+ 、Ba 2+ ) will be gradually consumed to form sulfate precipitation, while Pb, Ag and Cl - After the complex is formed, it is leached from the zinc-oxygen pressed slag.

[0034] The beneficial effects of the present invention are:

[0035] The present invention provides a method for recovering zinc, lead, and silver from zinc-oxygen slag by combining microbial leaching with chloride leaching. In the microbial leaching step, zinc sulfide, zinc oxide, and zinc sulfate in the zinc-oxygen slag are leached. At the same time, lead sulfide and silver sulfide in the slag are oxidized and converted into sulfates that are more easily reactive with chlorides. The microbial leached slag is then subjected to chloride leaching to recover lead and silver. The leaching rate of zinc is ≥95%, the leaching rate of lead is ≥95%, and the leaching rate of silver is ≥90%. The present invention exhibits good applicability to various types of zinc-oxygen slag, and realizes the step-by-step recovery of valuable metals zinc, lead, and silver from the zinc-oxygen slag. The present invention has the characteristics of simple process, environmental friendliness, and low cost, and exhibits good industrial application prospects. It has huge environmental and economic benefits and meets the current requirements of green metallurgy for clean production. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 The present invention is a process flow chart for recovering zinc, lead and silver from zinc-oxygen pressed slag by combining microbial leaching with chloride salt leaching. DETAILED DESCRIPTION

[0037] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. However, the following embodiments are intended only to explain the present invention, and the scope of protection of the present invention shall include the entire contents of the claims and shall not be limited to the present embodiments.

[0038] The efficient sulfur-oxidizing bacteria used in the bioleaching of the present invention is classified and named as Acidithiobacillus thiooxidans Retech DW-II, hereinafter referred to as the efficient leaching bacteria Retech DW-II. The deposited unit is: General Microbiology Center of China Culture Collection Administration of Microorganisms, address: No. 3, No. 1 Beichen West Road, Chaoyang District, Beijing, Institute of Microbiology, Chinese Academy of Sciences, deposit date: September 10, 2014, deposit number: CGMCCNO.9625.

[0039] The formula of 9K culture medium for cultivating the efficient sulfur oxidizing bacteria is: (NH4)2SO4 3.0g; KCl 0.10g; K2HPO4 0.50g; MgSO4.7H2O 0.50g; Ca(NO3)2 0.01g; FeSO4.7H2O 44.40g and distilled water 1000.00mL.

[0040] The culture method comprises the following steps: sterilizing a 9K culture medium with high-pressure steam for 2 to 10 minutes and cooling the medium to room temperature; inoculating the 9K culture medium with 5 to 20 v / v% of bacteria for leaching; adjusting the pH value to 1.0 to 3.0 using a 50 wt% sulfuric acid solution; and culturing the culture medium in a constant temperature shaking incubator for 10 to 50 days at a temperature of 20 to 45° C. and a shaking speed of 140 to 200 rpm to obtain a bacterial solution in the logarithmic growth phase with a bacterial concentration of ≥1.0×10 8 pcs / mL

[0041] like Figure 1The process flow shown in the figure is to dry the zinc-oxygen pressed slag and grind it to a size of less than 74 μm. The zinc-oxygen pressed slag is then mixed with deionized water to form a 5-30% slurry. The prepared slurry is then sterilized with high-pressure steam for 2-10 minutes and cooled to room temperature. The slurry pH is adjusted to 1.0-3.0 using a 50% sulphuric acid solution. The acid equilibrium pH remains stable for 24 hours. The slurry is then inoculated with Retech DW-II, a high-efficiency leaching bacterium cultured in 9K medium. The microbial leaching process is controlled at a temperature of 20-45°C, with a cycle of 10-50 days and an oscillation speed of 140-200 rpm. The microbial leaching system after bioleaching is filtered to separate the zinc-containing leachate and microbial leachate residue. The microbial leachate residue is washed three to four times with deionized water, dried, and then ground to a size of less than 74 μm. The zinc-containing leachate is recovered by extraction-electrodeposition. The microbial leaching residue is prepared into a slurry with a mass concentration of 5-30% using a chloride solution containing 100-350 g / L of chloride salt A and 10-30 g / L of chloride salt B, and the pH value of the slurry is adjusted to 0.5-5.0 using a 20 wt% hydrochloric acid solution, and then a chloride leaching operation is performed. The reaction temperature of the chloride leaching is 40-95°C, the leaching stirring speed is 100-500 rpm, and the reaction time is 0.5-4 hours. After the leaching is completed, it is immediately filtered while hot, and the leaching residue is washed 3-4 times with hot chloride salt A solution and deionized water respectively to obtain chloride leaching residue and lead-silver leachate. The lead-silver leachate is replaced with lead flakes to obtain coarse silver powder and replaced solution. The replaced solution is slowly cooled and crystallized to obtain lead chloride crystals; the lead chloride crystals and the chloride leachate are separated by filtration, and the chloride leachate is supplemented with chloride salt A and chloride salt B to the mass concentration of the chloride solution and then returned to the chloride leaching for recycling.

[0042] The sterilizer used for high-pressure steam sterilization in the present invention was purchased from Shanghai Shen'an Medical Instrument Factory, model LDZF-50KB, and was operated in accordance with the instrument's operating specifications.

[0043] Example 1

[0044] The zinc-oxygen pressed slag sample of this embodiment comes from a zinc smelter in Guangdong. Its main chemical components and chemical phase compositions are shown in Tables 1 to 4.

[0045] Table 1 Composition of zinc-oxygen pressed slag from a zinc smelter in Guangdong

[0046]

[0047] Table 2 Phase composition of zinc in zinc-oxygen pressed slag from a zinc smelter in Guangdong

[0048]

[0049] Table 3 Phase composition of lead in zinc-oxygen pressed slag from a zinc smelter in Guangdong

[0050]

[0051] Table 4 Silver phase composition in zinc-oxygen pressed slag from a zinc smelter in Guangdong

[0052]

[0053] Process flow such as Figure 1 As shown in the figure, the zinc-oxygen slag from a zinc smelter in Guangdong was dried and ground to -30μm, accounting for more than 85%. Its main chemical components and chemical phase composition are shown in Tables 1 to 4. The zinc-oxygen slag was prepared into a slurry with a mass concentration of 30% using deionized water, and then the prepared slurry was sterilized for 5 minutes using a Shanghai Shen'an LDZX-50KBS high-pressure sterilizer. The pH of the slurry was adjusted to 3.0 using a 50wt% sulfuric acid solution, and the acid was balanced for 24 hours. Then, the efficient leaching bacteria Retech DW-II cultured in 9K medium was inoculated. The bacterial inoculation amount was 5% by volume, and the bacterial concentration in the leaching system after inoculation was 2.0×10 7 The microbial leaching process was controlled at a temperature of 25°C, with a cycle of 10 days and a shaker speed of 150 rpm. After microbial leaching, the filter residue was filtered and washed three times with deionized water to obtain a microbial leaching residue and a zinc-containing leachate. The microbial leaching residue was placed in an oven for drying and then crushed to a size of -30 μm, accounting for more than 85%. The microbial leaching residue was prepared into a 20% slurry using a chloride solution containing 150 g / L of chloride salt A and 10 g / L of chloride salt B. The pH of the slurry was adjusted to 1.0 using a 20 wt% hydrochloric acid solution, and then the chloride leaching operation was carried out. The reaction temperature for chloride leaching is 50°C, the stirring speed is 150 rpm, and the reaction time is 0.5 h. Immediately after leaching, the solution is filtered while hot. The leached residue is washed three times with a 70-100°C chloride salt A solution and deionized water, respectively, to obtain chloride leaching residue and a lead-silver leachate. Samples are then sent for testing of the zinc, lead, and silver contents in the chloride leaching residue. The chloride salt A solution will naturally cool during the multiple washing processes and can be used to wash the leached residue as long as it is maintained within the 70-100°C range.

[0054] The method of the present invention for leaching zinc, lead, and silver from zinc-oxygen pressed slag using microbial leaching combined with chloride leaching has been shown to produce a final slag with a zinc content of 0.20%, a lead content of 1.09%, and a silver content of 31.23 g / t. The slag yield in the microbial leaching step is 97.54%, while the slag yield in the chloride leaching step is 76.86%. The leaching rates for zinc, lead, and silver are 95.26%, 95.19%, and 91.04%, respectively.

[0055] Example 2

[0056] Process flow such as Figure 1As shown in the figure, the zinc-oxygen slag from a zinc smelter in Guangdong was dried and ground to -30μm, accounting for more than 85%. Its main chemical components and chemical phase composition are shown in Tables 1 to 4. The zinc-oxygen slag was prepared into a slurry with a mass concentration of 25% using deionized water, and then the prepared slurry was sterilized for 5 minutes using a Shanghai Shen'an LDZX-50KBS high-pressure sterilizer. The pH of the slurry was adjusted to 2.8 using a 50wt% sulfuric acid solution, and the acid was balanced for 24 hours. Then, the efficient leaching bacteria Retech DW-II cultured in 9K medium was inoculated. The bacterial inoculation volume was 13%. The bacterial concentration in the leaching system after inoculation was 2.8×10 7 The microbial leaching process was controlled at a temperature of 30°C, with a cycle of 20 days and a shaker speed of 180 rpm. After microbial leaching, the filter residue was filtered and washed three times with deionized water to obtain a microbial leaching residue and a zinc-containing leachate. The microbial leaching residue was placed in an oven for drying and then crushed to a size of -30 μm, accounting for more than 85%. The microbial leaching residue was prepared into a 15% ore slurry using a chloride solution containing 200 g / L of chloride salt A and 15 g / L of chloride salt B. The slurry pH was adjusted to 1.5 using a 20 wt% hydrochloric acid solution, and then the chloride leaching operation was carried out. The reaction temperature of chloride leaching is 60°C, the leaching stirring speed is 200 rpm, the reaction time is 1 hour, and the leaching is immediately filtered while hot after the leaching is completed. The leaching residue is washed 3 times with 70-100°C chloride salt A solution and deionized water respectively to obtain chloride leaching residue and lead-silver leachate. Samples are sent for detection of the zinc, lead and silver contents in the chloride leaching residue.

[0057] The method of the present invention for leaching zinc, lead, and silver from zinc-oxygen pressed slag using microbial leaching combined with chloride leaching has been shown to produce a final leached slag with a zinc content of 0.19%, a lead content of 1.08%, and a silver content of 30.89 g / t. The slag yield in the microbial leaching step is 96.78%, while the slag yield in the chloride leaching step is 76.17%. The leaching rates for zinc, lead, and silver are 95.57%, 95.32%, and 91.28%, respectively.

[0058] Example 3

[0059] Process flow such as Figure 1As shown in the figure, the zinc-oxygen slag from a zinc smelter in Guangdong was dried and ground to -30μm, accounting for more than 85%. Its main chemical components and chemical phase composition are shown in Tables 1 to 4. The zinc-oxygen slag was prepared into a slurry with a mass concentration of 20% using deionized water, and then the prepared slurry was sterilized for 5 minutes using a Shanghai Shen'an LDZX-50KBS high-pressure sterilizer. The pH of the slurry was adjusted to 2.5 using a 50wt% sulfuric acid solution, and the acid was balanced for 24 hours. Then, the efficient leaching bacteria Retech DW-II cultured in 9K medium was inoculated. The bacterial inoculation volume was 15%. The bacterial concentration in the leaching system after inoculation was 3.2×10 7 The microbial leaching process was controlled at a temperature of 35°C, with a cycle of 30 days and a shaker speed of 170 rpm. After microbial leaching, the filter residue was filtered and washed three times with deionized water to obtain a microbial leaching residue and a zinc-containing leachate. The microbial leaching residue was placed in an oven for drying and then crushed to a size of -30 μm, accounting for more than 85%. The microbial leaching residue was prepared into a 5% slurry using a chloride solution containing 250 g / L of chloride salt A and 20 g / L of chloride salt B. The pH of the slurry was adjusted to 2.0 using a 20 wt% hydrochloric acid solution, and then the chloride leaching operation was carried out. The reaction temperature of chloride leaching is 70°C, the leaching stirring speed is 450rpm, the reaction time is 1.5h, and the leaching is immediately filtered while hot after the leaching is completed. The leaching residue is washed 3 times with 70-100°C chloride salt A solution and deionized water respectively to obtain chloride leaching residue and lead-silver leachate. Samples are sent for detection of the zinc, lead and silver contents in the chloride leaching residue.

[0060] The method of the present invention for leaching zinc, lead, and silver from zinc-oxygen pressed slag using microbial leaching combined with chloride leaching has been tested to produce a final leached slag with a zinc content of 0.13%, a lead content of 0.97%, and a silver content of 28.67 g / t. The slag yield in the microbial leaching step is 95.42%, while the slag yield in the chloride leaching step is 72.15%. The leaching rates for zinc, lead, and silver are 97.17%, 96.07%, and 92.44%, respectively.

[0061] Example 4

[0062] Process flow such as Figure 1As shown in the figure, the zinc-oxygen slag from a zinc smelter in Guangdong was dried and ground to -30μm, accounting for more than 85%. Its main chemical components and chemical phase composition are shown in Table 1 and Tables 2 to 4. The zinc-oxygen slag was prepared into a slurry with a mass concentration of 15% using deionized water, and then the prepared slurry was sterilized for 5 minutes using a Shanghai Shen'an LDZX-50KBS high-pressure sterilizer. The pH of the slurry was adjusted to 2.0 using a 50wt% sulfuric acid solution, and the acid was balanced for 24 hours. Then, the efficient leaching bacteria Retech DW-II cultured in 9K medium was inoculated. The bacterial inoculation amount was 7% by volume. The bacterial concentration in the leaching system after inoculation was 2.3×10 7 The microbial leaching process was controlled at a temperature of 40°C, with a cycle of 25 days and a shaker speed of 200 rpm. After microbial leaching, the filter residue was filtered and washed three times with deionized water to obtain a microbial leaching residue and a zinc-containing leachate. The microbial leaching residue was placed in an oven for drying and then crushed to a size of -30 μm, accounting for more than 85%. The microbial leaching residue was prepared into a slurry with a mass concentration of 8% using a chloride solution containing 350 g / L of chloride salt A and 25 g / L of chloride salt B. The pH of the slurry was adjusted to 2.5 using a 20 wt% hydrochloric acid solution, and then the chloride leaching operation was carried out. The reaction temperature of chloride leaching is 80°C, the leaching stirring speed is 350rpm, the reaction time is 3.0h, and the leaching is immediately filtered while hot after the leaching is completed. The leaching residue is washed 3 times with 70-100°C chloride salt A solution and deionized water respectively to obtain chloride leaching residue and lead-silver leachate. Samples are sent for detection of the zinc, lead and silver contents in the chloride leaching residue.

[0063] The method for leaching zinc, lead, and silver from zinc-oxygen pressed slag using the present invention's combined microbial leaching and chloride leaching method yields a zinc content of 0.08%, a lead content of 0.88%, and a silver content of 26.32 g / t in the final leached slag. The slag yields in the microbial leaching step were 94.17%, and in the chloride leaching step were 72.87%. The leaching rates for zinc, lead, and silver were 98.26%, 96.45%, and 93.09%, respectively.

[0064] Example 5

[0065] Process flow such as Figure 1As shown in the figure, the zinc slag from a zinc smelter in Guangdong was crushed, dried, and ground to -30μm, accounting for more than 85%. Its main chemical components and chemical phase composition are shown in Tables 1 to 4. The zinc slag was prepared into a slurry with a mass concentration of 10% using deionized water, and then the prepared slurry was sterilized for 5 minutes using a Shanghai Shen'an LDZX-50KBS high-pressure sterilizer. The pH of the slurry was adjusted to 1.5 using a 50wt% sulfuric acid solution, and the acid was balanced for 24 hours. Then, the efficient leaching bacteria Retech DW-II cultured in 9K medium was inoculated. The bacterial inoculation amount was 10% by volume. The bacterial concentration in the leaching system after inoculation was 2.5×10 7 The microbial leaching process was controlled at a temperature of 45°C, with a cycle of 15 days and a shaker speed of 160 rpm. After microbial leaching, the filter residue was filtered and washed three times with deionized water to obtain a microbial leaching residue and a zinc-containing leachate. The microbial leaching residue was placed in an oven for drying and then crushed to a size of -30 μm, accounting for more than 85%. The microbial leaching residue was prepared into a 10% ore slurry using a chloride solution containing 300 g / L of chloride salt A and 30 g / L of chloride salt B. The slurry pH was adjusted to 3.0 using 20 wt% hydrochloric acid solution, and then the chloride leaching operation was carried out. The reaction temperature of chloride leaching is 90°C, the leaching stirring speed is 350rpm, the reaction time is 2.0h, and the leaching is immediately filtered while hot after the leaching is completed. The leaching residue is washed 3 times with 70-100°C chloride salt A solution and deionized water respectively to obtain chloride leaching residue and lead-silver leachate. Samples are sent for detection of the zinc, lead and silver contents in the chloride leaching residue.

[0066] The method of the present invention for leaching zinc, lead, and silver from zinc-oxygen pressed slag using microbial leaching combined with chloride leaching has been tested to produce a final leached slag with a zinc content of 0.05%, a lead content of 0.65%, and a silver content of 25.25 g / t. The slag yield in the microbial leaching step is 92.56%, while the slag yield in the chloride leaching step is 73.57%. The leaching rates for zinc, lead, and silver are 98.92%, 97.40%, and 93.42%, respectively.

[0067] Example 6

[0068] The zinc-oxygen pressed slag sample of this embodiment comes from a zinc smelter in Yunnan. Its main chemical components and chemical phase compositions are shown in Tables 5 to 8.

[0069] Table 5 Composition of zinc-oxygen pressed slag from a zinc smelter in Yunnan

[0070]

[0071] Table 6 Phase composition of zinc in zinc-oxygen pressed slag from a zinc smelter in Yunnan

[0072]

[0073] Table 7 Phase composition of lead in zinc-oxygen pressed slag from a zinc smelter in Yunnan

[0074]

[0075] Table 8 Silver phase composition in zinc-oxygen pressed slag from a zinc smelter in Yunnan

[0076]

[0077] Process flow such as Figure 1 As shown in Figure 5, the zinc-oxygen slag sample was obtained from a zinc smelter in Yunnan. After drying and grinding to -30μm, it accounted for more than 85%. The main chemical components of this sample are shown in Tables 5 to 8. Deionized water was used to prepare the zinc-oxygen slag sample into a 20% mass concentration slurry, and the prepared slurry was sterilized in a Shanghai Shen'an LDZX-50KBS high-pressure sterilizer for 5 minutes. The slurry pH was adjusted to 1.0 using a 50wt% sulfuric acid solution, and the acid was balanced for 24 hours. Then, the efficient leaching bacteria Retech DW-II cultured in 9K medium was inoculated with an inoculation volume of 13%. The bacterial concentration in the leaching system after inoculation was 2.8×10 7 The microbial leaching process was controlled at a temperature of 25°C, with a cycle of 25 days and a shaker speed of 160 rpm. After microbial leaching, solid-liquid separation was performed and the filter residue was washed four times with deionized water to obtain a microbial leaching residue and a zinc-containing leachate. The microbial leaching residue was oven-dried and crushed to a particle size of -30 μm, accounting for more than 85%. The microbial leaching residue was prepared into a slurry with a mass concentration of 8% using a chloride solution containing 250 g / L of chloride salt A and 20 g / L of chloride salt B. The pH of the slurry was adjusted to 1.5 using a 20 wt% hydrochloric acid solution, and then the chloride leaching operation was carried out. The reaction temperature of chloride leaching is 70°C, the leaching stirring speed is 200 rpm, the reaction time is 1.0 h, and the leaching is immediately filtered while hot after the leaching is completed. The leaching residue is washed 4 times with 70-100°C chloride salt A solution and deionized water respectively to obtain chloride leaching residue and lead-silver leachate. The samples are sent for detection of the zinc, lead and silver contents in the chloride leaching residue.

[0078] Testing has shown that the method for leaching zinc, lead, and silver from zinc-oxygen pressed slag using the present invention's combined microbial leaching and chloride leaching method yields a zinc content of 0.13%, a lead content of 1.12%, and a silver content of 54.91 g / t in the final leached slag. The slag yields in the microbial leaching step are 96.32%, and in the chloride leaching step are 69.89%. The leaching rates for zinc, lead, and silver are 95.89%, 96.57%, and 91.91%, respectively.

[0079] Example 7

[0080] Process flow such as Figure 1As shown in Figure 5, the zinc-oxygen slag sample was obtained from a zinc smelter in Yunnan. After drying and grinding to -30μm, it accounted for more than 85%. Its main chemical components and chemical phase composition are shown in Tables 5 to 8. Deionized water was used to prepare the zinc-oxygen slag sample into a slurry with a mass concentration of 5%. The prepared slurry was then sterilized for 5 minutes using a Shanghai Shen'an LDZX-50KBS high-pressure sterilizer. The slurry pH was adjusted to 2.0 using a 50wt% sulfuric acid solution and acid-balanced for 24 hours. The highly efficient leaching bacteria Retech DW-II cultured in 9K medium was then inoculated with an inoculation volume of 10%. The bacterial concentration in the leaching system after inoculation was 2.5×10 7 The microbial leaching process was controlled at a temperature of 40°C, with a cycle of 20 days and a shaker speed of 180 rpm. After microbial leaching, solid-liquid separation was performed and the filter residue was washed four times with deionized water to obtain a microbial leaching residue and a zinc-containing leachate. The microbial leaching residue was oven-dried and crushed to a particle size of -30 μm, accounting for more than 85%. The microbial leaching residue was prepared into a 5% slurry using a chloride solution containing 300 g / L of chloride salt A and 25 g / L of chloride salt B. The slurry pH was adjusted to 1.0 using 20 wt% hydrochloric acid solution, and then the chloride leaching operation was carried out. The reaction temperature of chloride leaching is 80°C, the leaching stirring speed is 450rpm, the reaction time is 3.0h, and the leaching is immediately filtered while hot after the leaching is completed. The leaching residue is washed 4 times with 70-100°C chloride salt A solution and deionized water respectively to obtain chloride leaching residue and lead-silver leachate. Samples are sent for detection of the zinc, lead and silver contents in the chloride leaching residue.

[0081] Testing has shown that the method for leaching zinc, lead, and silver from zinc-oxygen pressed slag using the present invention's combined microbial leaching and chloride leaching method yields a zinc content of 0.09%, a lead content of 1.04%, and a silver content of 46.13 g / t in the final leached slag. The slag yields in the microbial leaching step are 95.28%, and in the chloride leaching step are 69.21%. The leaching rates for zinc, lead, and silver are 97.21%, 96.88%, and 93.34%, respectively.

[0082] Example 8

[0083] Process flow such as Figure 1As shown in Figure 5, the zinc-oxygen slag sample was obtained from a zinc smelter in Yunnan. After drying and grinding to -30μm, it accounted for more than 85%. Its main chemical components and chemical phase composition are shown in Tables 5 to 8. Deionized water was used to prepare the zinc-oxygen slag sample into a slurry with a mass concentration of 10%. The prepared slurry was then sterilized for 5 minutes using a Shanghai Shen'an LDZX-50KBS high-pressure sterilizer. The slurry pH was adjusted to 1.5 using a 50wt% sulfuric acid solution and acid-balanced for 24 hours. The highly efficient leaching bacteria Retech DW-II cultured in 9K medium was then inoculated with an inoculation volume of 15%. The bacterial concentration in the leaching system after inoculation was 3.2×10 7 The microbial leaching process was controlled at a temperature of 45°C, with a cycle of 15 days and a shaker speed of 160 rpm. After microbial leaching, solid-liquid separation was performed and the filter residue was washed four times with deionized water to obtain microbial leaching residue and zinc-containing leachate. The microbial leaching residue was placed in an oven for drying and crushed to a particle size of -30 μm, accounting for more than 85%. The microbial leaching residue was prepared into a 10% slurry using a chloride solution containing 350 g / L of chloride salt A and 30 g / L of chloride salt B. The pH of the slurry was adjusted to 0.5 using 20 wt% hydrochloric acid solution, and then the chloride leaching operation was carried out. The reaction temperature of chloride leaching is 90°C, the leaching stirring speed is 350rpm, the reaction time is 2.0h, and the leaching is immediately filtered while hot after the leaching is completed. The leaching residue is washed 4 times with 70-100°C chloride salt A solution and deionized water respectively to obtain chloride leaching residue and lead-silver leachate. Samples are sent for detection of the zinc, lead and silver contents in the chloride leaching residue.

[0084] Testing has shown that the method for leaching zinc, lead, and silver from zinc-oxygen pressed slag using the present invention's combined microbial leaching and chloride leaching method yields a zinc content of 0.06%, a lead content of 0.92%, and a silver content of 42.89 g / t in the final leached slag. The slag yields in the microbial leaching step are 94.12%, and in the chloride leaching step are 68.76%. The leaching rates for zinc, lead, and silver are 98.18%, 97.29%, and 93.92%, respectively.

[0085] Example 9

[0086] Process flow such as Figure 1As shown in Figure 5, the zinc-oxygen slag sample was obtained from a zinc smelter in Yunnan. After drying and grinding to -30μm, it accounted for more than 85%. Its main chemical components and chemical phase composition are shown in Tables 5 to 8. Deionized water was used to prepare the zinc-oxygen slag sample into a slurry with a mass concentration of 15%. The prepared slurry was then sterilized for 5 minutes using a Shanghai Shen'an LDZX-50KBS high-pressure sterilizer. The pH of the slurry was adjusted to 2.5 using a 50wt% sulfuric acid solution and acid-balanced for 24 hours. The highly efficient leaching bacteria Retech DW-II cultured in 9K medium was then inoculated with an inoculation volume of 7%. The bacterial concentration in the leaching system after inoculation was 2.3×10 7 The microbial leaching process was controlled at a temperature of 35°C, with a cycle of 30 days and a shaker speed of 170 rpm. After microbial leaching, solid-liquid separation was performed, and the filter residue was washed four times with deionized water to obtain a microbial leaching residue and a zinc-containing leachate. The microbial leaching residue was oven-dried and crushed to a particle size of -30 μm, representing at least 85%. The microbial leaching residue was prepared into a 15% slurry using a chloride solution containing 200 g / L of chloride salt A and 15 g / L of chloride salt B. The pH of the slurry was adjusted to 2.0 using 20 wt% hydrochloric acid solution, and then chloride leaching was performed. The chloride leaching reaction temperature was 60°C, the stirring speed was 250 rpm, and the reaction time was 1.5 h. After leaching, the residue was immediately filtered while hot and washed four times with a 70-100°C chloride salt A solution and deionized water, respectively, to obtain a chloride leaching residue and a lead-silver leachate. The chloride salt leaching residue obtained is the product of leaching away zinc, lead and silver after being dried, and samples are sent for testing of the zinc, lead and silver contents therein.

[0087] Testing has shown that the method for leaching zinc, lead, and silver from zinc-oxygen pressed slag using the present invention's combined microbial leaching and chloride leaching method yields a zinc content of 0.11%, a lead content of 1.25%, and a silver content of 56.34 g / t in the final leached slag. The slag yields in the microbial leaching step are 95.87%, and in the chloride leaching step are 71.43%. The leaching rates for zinc, lead, and silver are 96.46%, 96.11%, and 91.56%, respectively.

[0088] Example 10

[0089] Process flow such as Figure 1As shown in Figure 5, the zinc-oxygen slag sample was obtained from a zinc smelter in Yunnan. After drying and grinding to -30μm, it accounted for more than 85%. Its main chemical components and chemical phase composition are shown in Tables 5 to 8. Deionized water was used to prepare the zinc-oxygen slag sample into a slurry with a mass concentration of 30%. The prepared slurry was then sterilized for 5 minutes using a Shanghai Shen'an LDZX-50KBS high-pressure sterilizer. The slurry pH was adjusted to 3.0 using a 50wt% sulfuric acid solution and acid-balanced for 24 hours. The highly efficient leaching bacteria Retech DW-II cultured in 9K medium was then inoculated with an inoculation volume of 5%. The bacterial concentration in the leaching system after inoculation was 2.0×10 7 The microbial leaching process was controlled at a temperature of 30°C, with a cycle of 10 days and a shaker speed of 150 rpm. After microbial leaching, solid-liquid separation was performed and the filter residue was washed four times with deionized water to obtain a microbial leaching residue and a zinc-containing leachate. The microbial leaching residue was placed in an oven for drying and crushed to a particle size of -30 μm, accounting for more than 85%. The microbial leaching residue was prepared into a 20% ore slurry using a chloride solution containing 150 g / L of chloride salt A and 10 g / L of chloride salt B. The slurry pH was adjusted to 3.0 using a 20 wt% hydrochloric acid solution, and then the chloride leaching operation was carried out. The reaction temperature of chloride leaching is 50°C, the leaching stirring speed is 150 rpm, the reaction time is 0.5 h, and the mixture is immediately filtered while hot after the leaching is completed. The leaching residue is washed 4 times with a chloride A solution at 70-100°C and deionized water, respectively, to obtain chloride leaching residue and lead-silver leachate. Samples are sent for testing the contents of zinc, lead and silver in the chloride leaching residue.

[0090] Testing has shown that the method for leaching zinc, lead, and silver from zinc-oxygen pressed slag using the present invention's combined microbial leaching and chloride leaching method yields a zinc content of 0.12%, a lead content of 1.26%, and a silver content of 57.08 g / t in the final leached slag. The slag yields in the microbial leaching step are 97.89%, and in the chloride leaching step are 72.03%. The leaching rates for zinc, lead, and silver are 96.03%, 95.96%, and 91.19%, respectively.

[0091] As can be seen from the above examples, the present invention provides a method for recovering zinc, lead, and silver from zinc-oxygen slag by combining microbial leaching with chloride leaching. During the microbial leaching step, zinc sulfide, zinc oxide, and zinc sulfate are leached from the zinc-oxygen slag. Simultaneously, lead sulfide and silver sulfide in the slag are oxidized and converted into sulfates that more readily react with chloride. The microbial leached slag is then subjected to chloride leaching to recover lead and silver. The leaching rates for zinc, lead, and silver are ≥95%, ≥95%, and ≥90%, respectively. This method is simple, environmentally friendly, and low-cost, providing a new approach for recovering zinc, lead, and silver from zinc-oxygen slag and exhibiting promising industrial application prospects.

[0092] Some parts of the present invention are well known to those skilled in the art and are not described in detail.

[0093] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A method for recovering zinc, lead and silver from zinc-oxygen pressed slag by combining microbial leaching with chloride leaching, characterized in that: The method comprises the following steps: 1) Crushing: Dry the zinc-oxygen pressed slag and grind it to less than 74 μm; 2) Slurry preparation: the zinc-oxygen pressed slag after grinding in step 1) is prepared with deionized water into a slurry with a mass concentration of 5 to 30%, and then the prepared slurry is sterilized with high-pressure steam for 2 to 10 minutes and cooled to room temperature; 3) Acid balance: Use 50wt% sulfuric acid solution to adjust the pH value of the slurry to 1.0-3.0, and keep the pH stable for 24 hours; 4) Bioleaching: sterilize the 9K culture medium with high-pressure steam for 2 to 10 minutes and cool to room temperature; then inoculate the 9K culture medium with 5 to 20 v / v% of leaching bacteria, adjust the pH value to 1.0 to 3.0 with 50 wt% sulfuric acid solution, and culture in a constant temperature shaking incubator for 10 to 50 days at a temperature of 20 to 45°C and a shaking speed of 140 to 200 rpm to obtain a bacterial solution in the logarithmic growth phase with a bacterial concentration of ≥1.0×10 8 / mL; inoculating the bacterial solution in the logarithmic growth phase into the slurry after acid balance in step 3) at an inoculum rate of 5-20v / v% to obtain a zinc-oxygen slag microbial leaching system, placing the microbial leaching system in a constant temperature shaking incubator, controlling the temperature between 20 and 45°C, the oscillator speed at 140-200rpm, and the bioleaching time for 10 to 50d; The leaching bacteria are highly efficient sulfur-oxidizing bacteria, the strain is classified as Acidithiobacillus thiooxidans Retech DW-Ⅱ, and the deposited unit is the General Microbiology Center of China Culture Collection Administration, located at No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing, Institute of Microbiology, Chinese Academy of Sciences, on September 10, 2014, with the deposit number CGMCC NO.9625. 5) Solid-liquid separation: The microbial leaching system after bioleaching is filtered and separated to obtain a zinc-containing leachate and a microbial leaching residue. The microbial leaching residue is washed 3 to 4 times with deionized water, dried, and then ground to a size of less than 74 μm. The zinc-containing leachate is recovered by extraction-electrodeposition. 6) Slurry preparation: adding chloride salt A and chloride salt B to deionized water to prepare a chloride salt solution containing chloride salt A at a mass concentration of 100-350 g / L and chloride salt B at a mass concentration of 10-30 g / L; using the chloride salt solution to prepare a slurry with a mass concentration of 5-30% by weight of the microbial leaching residue after grinding in step 5), and adjusting the pH value of the slurry to 0.5-5.0 using a 20 wt % hydrochloric acid solution; 7) Chloride leaching and solid-liquid separation: the slurry after pH adjustment in step 6) is directly subjected to leaching and stirring, the leaching stirring speed is 100-500 rpm, the reaction time is 0.5-4h, and the reaction temperature is 40-95°C. After the leaching is completed, the chloride leaching residue and the lead-silver leachate are immediately filtered while hot to obtain the chloride leaching residue; the chloride leaching residue is washed 3-4 times with a chloride salt A solution containing a mass concentration of 100-350 g / L at 70-100°C, and then the chloride leaching residue is washed 3-4 times with deionized water, and then the chloride leaching residue is dried; the lead-silver leachate is replaced with lead flakes to obtain coarse silver powder and a replaced solution, and the replaced solution is slowly cooled and crystallized to obtain lead chloride crystals; the lead chloride crystals and the chloride leaching solution are filtered and separated, and the chloride A and chloride B are supplemented to the chloride solution to reach the mass concentration of the chloride solution, and then returned to the chloride leaching for recycling; Wherein, the chloride salt A described in step 6) is one or more of NaCl, KCl, FeCl3, and MgCl2, and the chloride salt B is one or two of CaCl2 and BaCl2; In the prepared chloride solution described in step 6), the mass concentration of chloride salt A is 150-350 g / L, and the mass concentration of chloride salt B is 15-30 g / L; the mass concentration of the slurry of the microbial leaching residue prepared using the chloride solution is 5-20%, and the pH value of the slurry is adjusted to 0.5-3 using 20wt% hydrochloric acid solution.

2. The method for recovering zinc, lead and silver from zinc-oxygen pressed slag by combining microbial leaching with chloride leaching according to claim 1, characterized in that: The zinc-oxygen pressed slag particle size in step 1) is -30 μm, accounting for more than 85%.

3. The method for recovering zinc, lead and silver from zinc-oxygen pressed slag by combining microbial leaching with chloride leaching according to claim 1, characterized in that: The mass concentration of the slurry in step 2) is 5-25%, and the sterilization time is 4-8 minutes.

4. The method for recovering zinc, lead and silver from zinc-oxygen pressed slag by combining microbial leaching with chloride leaching according to claim 1, characterized in that: The formula of the 9K culture medium described in step 3) is: (NH4)2SO4 3.0 g; KCl 0.10 g; K2HPO4 0.50 g; MgSO4.7H2O 0.50 g; Ca(NO3)2 0.01 g; FeSO4.7H2O4 4.40 g and distilled water 1000.00 mL.

5. The method for recovering zinc, lead and silver from zinc-oxygen pressed slag by combining microbial leaching with chloride leaching according to claim 1, characterized in that: The bacterial concentration in the solution after inoculation in step 4) is 1.0×10 7 ~2.0×10 7 pieces / mL.

6. The method for recovering zinc, lead and silver from zinc-oxygen pressed slag by combining microbial leaching with chloride leaching according to claim 1, characterized in that: The pH value of the solution described in step 4) is adjusted to 1.5-3.0 using a 50wt% sulfuric acid solution, the inoculation amount is 5-15v / v%, and the culture is cultured at a constant temperature of 25-45°C for 10-30 days at an oscillator speed of 150-200rpm to obtain a bacterial solution in the logarithmic growth phase.

7. The method for recovering zinc, lead and silver from zinc-oxygen pressed slag by combining microbial leaching with chloride leaching according to claim 1, characterized in that: The temperature of the microbial leaching system in step 4) is controlled at 25-45° C., the rotation speed of the oscillator is 150-200 rpm, and the leaching time is 10-40 days.

8. The method for recovering zinc, lead and silver from zinc-oxygen pressed slag by combining microbial leaching with chloride leaching according to claim 1, characterized in that: The reaction temperature of the chloride leaching microorganism leaching residue in step 7) is 50-90° C., the leaching stirring speed is 150-450 rpm, and the reaction time is 0.5-3 h.

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