Composite collecting agent, combined reagent and method for recovering indium from zinc leaching dangerous waste residues

Abstract

The invention discloses a composite collecting agent, a combined reagent and a method for recovering indium from zinc leaching dangerous waste residues, the composite collecting agent for recovering indium from zinc leaching dangerous waste residues comprises a main collecting agent and an auxiliary collecting agent, the mass ratio of the main collecting agent to the auxiliary collecting agent is (3: 1)-(5: 1), and the mass ratio of the main collecting agent to the auxiliary collecting agent is (3: 1)-(5: 1). The main collecting agent comprises N-allyl-O-isobutyl thiocarbamate, and the auxiliary collecting agent comprises diphenyl thiourea. The composite collecting agent and the composite inhibitor are used for carrying out flotation separation on ore pulp of the zinc leaching dangerous waste residues, high-selectivity flotation of indium in the zinc leaching dangerous waste residues can be achieved, meanwhile, volatilization of indium, silver and zinc in flotation tailings is improved in combination with microwave enhanced roasting, and the recovery rate of indium, zinc and silver in the zinc leaching dangerous waste residues is remarkably increased.

Description

Technical Field

[0001] The present invention relates to the technical field of mineral processing, and in particular to a composite collector, a combined reagent and a method for recovering indium from zinc leaching hazardous waste residue. Background Art

[0002] Zinc smelting leaching residue (HW48) typically contains 0.05-0.15% indium, 8-15% zinc, and 50-200g / t silver. Existing processing technologies have the following drawbacks: In traditional flotation processes, indium minerals have similar floatability to iron minerals, resulting in low concentrate grade (In<0.5%); The conventional roasting process has a zinc volatilization rate of only 90-93% and an indium recovery rate of less than 80%; Silver is lost in scattered processes, with total recovery rates typically below 70%; High energy consumption (roasting temperature>1200℃), residual zinc in kiln slag>0.5%.

[0003] CN110616334A uses an acid leaching-extraction process, resulting in an indium recovery cost of up to 800 yuan / kg. Meanwhile, CN102206745A uses a single xanthate collector, resulting in an indium concentrate with an iron content exceeding 15%. Therefore, the development of a new, efficient, and low-cost comprehensive recovery process is urgently needed. Summary of the Invention

[0004] The purpose of the present invention is to overcome the above-mentioned deficiencies of the prior art and to provide a composite collector, a combined reagent and a method for recovering indium from zinc leaching hazardous waste residue.

[0005] The present invention solves the technical problem by adopting the following technical solutions.

[0006] The present invention provides a composite collector for recovering indium from zinc leaching hazardous waste residue. The composite collector comprises a main collector and an auxiliary collector, wherein the mass ratio of the main collector to the auxiliary collector is (3:1) to (5:1), the main collector comprises N-allyl-O-isobutylthiocarbamate, and the auxiliary collector comprises diphenylthiourea.

[0007] The present invention also provides a composite agent for recovering indium, zinc and silver from zinc leaching hazardous waste residue. The composite agent comprises a composite inhibitor and the above-mentioned composite collector, and the composite inhibitor comprises sodium thiosulfate and sodium citrate.

[0008] The present invention also provides a method for recovering indium, zinc and silver from zinc leaching hazardous waste residue, which comprises: using the above-mentioned combined reagent, adopting a combined process of flotation separation and microwave-enhanced roasting to recover indium, zinc and silver from zinc leaching hazardous waste residue.

[0009] The present invention has the following beneficial effects: The present invention provides a composite collector, combined reagent, and method for recovering indium from zinc leaching hazardous waste. This process innovatively employs a composite inhibitor and a specific collector to achieve highly selective indium flotation. This process, combined with microwave activation and enhanced roasting technology to increase the volatility of indium and zinc, simultaneously achieves efficient silver enrichment through gradient temperature control. This process offers advantages such as high metal recovery (indium >94%, zinc >96%, and silver >90%), a 35% reduction in energy consumption, and harmless kiln slag (residual zinc <0.35%, residual indium <0.03%). This process provides an efficient and economical solution for the resource recovery of hazardous smelting waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0011] Figure 1 Flow chart for recovering indium, zinc and silver from zinc leaching hazardous waste residue. DETAILED DESCRIPTION

[0012] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, all are conventional products that can be purchased commercially.

[0013] The following is a detailed description of a composite collector, combined reagent and method for recovering indium from zinc leaching hazardous waste provided by an embodiment of the present invention.

[0014] In a first aspect, an embodiment of the present invention provides a composite collector for recovering indium from zinc leaching hazardous waste residue, the composite collector comprising a main collector and an auxiliary collector, wherein: the mass ratio of the main collector to the auxiliary collector is (3:1) to (5:1), the main collector comprises N-allyl-O-isobutylthiocarbamate, and the auxiliary collector comprises diphenylthiourea.

[0015] The embodiment of the present invention provides a composite collector for recovering indium from zinc leaching hazardous waste residue, the composite collector comprising a main collector and an auxiliary collector, wherein: the main collector comprises N-allyl-O-isobutylthiocarbamate, the molecular formula of N-allyl-O-isobutylthiocarbamate is C8H 15NOS, the structural formula is: CH2=CH-CH2-NH-C(=S)-OCH2-CH2(CH3)2, the auxiliary collector includes diphenylthiourea, the molecular formula of diphenylthiourea is C 13 H 12 N2S, the structural formula is: (C6H5)2N-C(=S)-NH2. In the process of efficiently recovering indium, zinc and silver from zinc leaching hazardous waste residue, In 3+ Preferentially coordinates with the S and N atoms of thiocarbamate to form a stable surface complex, that is, the characteristic group -SC(=S)-NH- in N-allyl-O-isobutylthiocarbamate and In 3+ By forming a five-membered ring chelate, diphenylthiourea enhances the adsorption selectivity of the mineral surface through π-π conjugation, changes the hydrophobicity of the mineral surface through the hydrophobic effect of the aromatic ring, makes the mineral more hydrophobic, and strengthens the bubble mineralization effect, thereby improving the capture effect, improving the flotation index and enhancing the mineral separation effect.

[0016] The composite collector for recovering indium from zinc leaching hazardous waste provided by the embodiment of the present invention is characterized in that the primary collector N-allyl-O-isobutylthiocarbamate preferentially reacts with In 3+ The combination (binding energy -158.7 kJ / mol) significantly improves indium recovery; the auxiliary collector, diphenylthiourea, inhibits the flotation of iron minerals, achieving an indium / iron separation coefficient of 28.5 (compared to only 6.2 in conventional processes). This composite collector enables highly selective flotation of indium from zinc leaching hazardous waste.

[0017] In a second aspect, an embodiment of the present invention further provides a composite agent for recovering indium, zinc, and silver from zinc leaching hazardous waste residue, wherein the composite agent comprises a composite inhibitor and the above-mentioned composite collector, wherein the composite inhibitor comprises sodium thiosulfate and sodium citrate.

[0018] An embodiment of the present invention also provides a combined reagent for recovering indium, zinc, and silver from zinc leaching hazardous waste residue. The combined reagent includes a composite inhibitor and a composite collector. The composite inhibitor is used to inhibit the floating of silver and zinc in the zinc leaching hazardous waste residue and prevent their attachment to bubbles. The composite collector improves the selectivity of indium and achieves high-selective flotation of indium.

[0019] In some optional embodiments, the composite inhibitor consists of sodium thiosulfate and sodium citrate, and the mass ratio of sodium thiosulfate to sodium citrate is (2:1) to (3:1).

[0020] In some optional embodiments, the composite collector is composed of N-allyl-O-isobutylthiocarbamate and diphenylthiourea, and the mass ratio of N-allyl-O-isobutylthiocarbamate to diphenylthiourea is (3:1) to (5:1).

[0021] In a third aspect, an embodiment of the present invention further provides a method for recovering indium, zinc, and silver from zinc leaching hazardous waste residue, which comprises: using a combined process of flotation separation and microwave-enhanced roasting to recover indium, zinc, and silver from zinc leaching hazardous waste residue.

[0022] The embodiment of the present invention provides a method for recovering indium, zinc, and silver from zinc leaching hazardous waste residue. Flotation separation is used to achieve efficient enrichment of indium in the zinc leaching hazardous waste residue to obtain indium-rich concentrate and flotation tailings. The flotation tailings are then subjected to microwave-enhanced roasting treatment to promote the volatilization of zinc and indium in the flotation tailings, thereby recovering zinc and a small amount of indium from the flotation tailings. In addition, silver can also be recovered from the indium-rich concentrate and roasting smoke, thereby achieving efficient recovery of indium, zinc, and silver from zinc leaching hazardous waste residue.

[0023] In some optional embodiments, the steps include: providing zinc leaching hazardous waste slag slurry, successively adding a composite inhibitor and a composite collector to the slurry for flotation separation to obtain indium-rich concentrate and flotation tailings, then mixing the flotation tailings with a reducing agent for microwave roasting treatment, and recovering indium and zinc from the roasting dust through bag dust collection.

[0024] In some optional embodiments, the method further comprises: recovering silver from the indium-rich concentrate and the roasting fumes.

[0025] The embodiment of the present invention provides a method for recovering indium, zinc, and silver from zinc leaching hazardous waste residue. The method can not only achieve high-selective recovery of indium and zinc, but also achieve high-efficiency recovery of silver. The process of recovering silver is as follows: (1) Silver enrichment in the flotation separation stage: Sodium thiosulfate in the composite inhibitor added to the zinc leaching hazardous waste slurry can selectively inhibit the floating of zinc minerals and promote the partial enrichment of silver minerals in the indium concentrate. Sodium citrate can complex calcium and magnesium ions to prevent them from interfering with indium adsorption. In addition, diphenylthiourea in the composite collector enhances the adsorption selectivity of silver minerals on the surface of indium-rich concentrate through the hydrophobic effect of aromatic rings. Compared with the traditional process in which silver is dispersed and lost in the process, the method provided in the embodiment of the present invention optimizes the distribution of silver through the combination of reagents.

[0026] (2) Silver enrichment in the microwave roasting stage: The flotation tailings are mixed with a reducing agent and subjected to microwave irradiation to increase the specific surface area of ​​the tailings by >50%, so that the silver minerals are fully in contact with the reducing agent and the activation of silver is promoted. In the subsequent roasting process, the silver is converted into volatile silver chloride or elemental silver at high temperature, which evaporates into the smoke along with indium and zinc.

[0027] (3) Final recovery of silver: Silver in indium-rich concentrate is recovered through subsequent hydrometallurgy (such as acid leaching-replacement). Silver in roasting dust is captured with the dust bag and separated by electrolysis or chemical precipitation.

[0028] In some optional embodiments, the flotation separation step is as follows: after adjusting the pH value of the slurry with sulfuric acid, a composite depressant and a composite collector are added to the slurry in sequence to obtain indium-rich concentrate and flotation tailings, wherein: The slurry is made by filtering zinc leaching hazardous waste slag to a moisture content of <25%, and then grinding the ore to -0.074mm, accounting for 82±3% of the total material. Among them, the indium content in the zinc leaching hazardous waste slag is 0.056%~0.10%, and the zinc content is 8.62%~11.39%; The dosage of sodium thiosulfate in the composite inhibitor is 1.5kg / t-2kg / t, and the dosage of sodium citrate is 0.5kg / t-1kg / t; The dosage of N-allyl-O-isobutylthiocarbamate in the composite collector is 300g / t-500g / t, and the dosage of diphenylthiourea is 100g / t-200g / t; The flotation pH is 5.0-6.0; The flotation process is two roughing selections + three cleaning selections + two scavenging selections.

[0029] In some optional embodiments, the microwave-enhanced roasting step is as follows: after mixing the flotation tailings with a reducing agent, sequentially performing microwave irradiation treatment and roasting treatment, the roasting flue gas is collected by bag dust collection to recover indium and zinc, and the roasting flue gas from which indium and zinc are recovered is subjected to desulfurization treatment and discharged in compliance with the GB25466-2016 standard, wherein: Mix the flotation tailings with anthracite and coke in a mass ratio of 1:(0.2-0.3):(0.1-0.15); The frequency of microwave treatment is 4 GHz, and the time is 5-10 minutes. The specific surface area of ​​flotation tailings increases by more than 50% after microwave treatment. The roasting temperature of the roasting treatment is 1100±20°C, the time is 0.5h-1h, and the rotation speed of the rotary kiln during the roasting treatment is 0.5r / min-1r / min.

[0030] It should be noted that the recovery method in the present invention is mainly aimed at zinc leaching hazardous waste residue with an indium content of 0.056% to 0.10% and a zinc content of 8.62% to 11.39%. This does not mean that the recovery method in the present invention is only applicable to zinc leaching hazardous waste residue with the above-mentioned content, but the content of valuable metal elements in the zinc leaching hazardous waste residue is limited. This is because the content of valuable metal elements in the zinc leaching hazardous waste residue as waste residue will not be too high, but if it is too low, the recovery cost will be too high, the economic value will be low, or even it will have no recovery value.

[0031] In some optional embodiments, the indium grade of the indium-rich concentrate obtained by flotation separation is >0.8%, the indium recovery rate is >92%, the zinc recovery rate after microwave roasting treatment is >96%, the total indium recovery rate is >94%, the total silver recovery rate is >90%, the residual zinc in the kiln slag is <0.35%, and the residual indium is <0.03%.

[0032] The present invention will be further described below with reference to the embodiments.

[0033] Example 1 Treatment of hazardous waste residue from zinc leaching in a smelter (In 0.082%, Zn 10.2%, Ag 135g / t), see Figure 1 , the steps are as follows: Step 1: filter the zinc leaching hazardous waste residue to a moisture content of <25%, and then grind the ore with a rod mill to -0.074 mm, accounting for 83% of the total material, to obtain slurry.

[0034] Step 2: First, an inhibitor (sodium thiosulfate 1.8 kg / t + sodium citrate 0.6 kg / t) was added to the raw ore pulp, and then a composite collector (N-allyl derivative 350 g / t + diphenylthiourea 120 g / t) was added. After flotation separation, indium-rich concentrate (In 0.85%, recovery rate 96.5%) and flotation tailings were obtained.

[0035] Step 3: The flotation tailings are blended with coal (anthracite accounts for 25% of the total mass of the flotation tailings and coke accounts for 12% of the total mass of the flotation tailings). After being treated with a 4 GHz microwave for 8 minutes, the tailings are fed into a rotary kiln and roasted at 1100° C. for 0.5 hours. The roasting ash is recovered by a bag dust collector for dust removal, and zinc and indium are recovered from the roasting dust. Silver is also recovered from the indium-rich concentrate and the roasting dust. The flue gas is then desulfurized to meet the emission standards of GB 25466-2016.

[0036] The final indicators are as follows: Zn recovery rate 98.9%; The total recovery rate of In was 96.8%; The total recovery of Ag was 92.3%; The residual Zn content in the kiln slag is 0.21%, and the residual In content is 0.018%.

[0037] Example 2 Processing of high silver leaching residue (In 0.068%, Zn 11.5%, Ag 185g / t), see Figure 1 , the steps are as follows: Step 1: filter the zinc leaching hazardous waste residue to a moisture content of <25%, and then grind the ore with a rod mill to -0.074 mm, accounting for 85% of the total material, to obtain slurry.

[0038] Step 2: First, an inhibitor (sodium thiosulfate 2 kg / t + sodium citrate 0.8 kg / t) was added to the raw ore pulp, and then a composite collector (N-allyl derivative 400 g / t + diphenylthiourea 150 g / t) was added for flotation separation to obtain indium-rich concentrate (In 0.82%, recovery rate 95.6%) and flotation tailings.

[0039] Step 3: The tailings are blended with coal (anthracite accounts for 28% of the total mass of the flotation tailings and coke accounts for 14% of the total mass of the flotation tailings). After being treated with a 4 GHz microwave for 10 minutes, the tailings are fed into a rotary kiln and roasted at 1080° C. for 0.8 hours. The roasting ash is recovered by a bag dust collector to remove dust, and zinc and indium are recovered from the roasting dust. Silver is also recovered from the indium-rich concentrate and the roasting dust. The flue gas is then desulfurized to meet the emission standards of GB 25466-2016.

[0040] The final indicators are as follows: Zn recovery rate: 98.5%; The total recovery rate of In was 95.9%; The total recovery of Ag was 93.7%; The residual Zn content in the kiln slag is 0.23%, and the residual In content is 0.017%.

[0041] Example 3 The steps are basically similar to those in Example 1, except that: in step 2, an inhibitor (sodium thiosulfate 2 kg / t + sodium citrate 0.8 kg / t) is first added to the original ore slurry, and then a composite collector (N-allyl derivative 300 g / t + diphenylthiourea 150 g / t) is added for flotation separation to obtain indium-rich concentrate (In 0.86%, recovery rate 95.3%) and flotation tailings.

[0042] The final indicators are as follows: Zn recovery rate 98.01%; The total recovery rate of In was 95.3%; The total recovery of Ag was 93.21%; The residual Zn content in the kiln slag is 0.26%, and the residual In content is 0.013%.

[0043] Example 4 The steps are basically similar to those in Example 1, except that: in step 2, an inhibitor (sodium thiosulfate 2 kg / t + sodium citrate 0.8 kg / t) is first added to the original ore slurry, and then a composite collector (N-allyl derivative 400 g / t + diphenylthiourea 200 g / t) is added for flotation separation to obtain indium-rich concentrate (In 0.82%, recovery rate 94.87%) and flotation tailings.

[0044] The final indicators are as follows: Zn recovery rate 97.89%; The total recovery rate of In was 94.97%; The total recovery rate of Ag was 93.02%; The residual Zn content in the kiln slag is 0.28%, and the residual In content is 0.016%.

[0045] Example 5 The steps are basically similar to those in Example 1, except that: in step 2, an inhibitor (sodium thiosulfate 2 kg / t + sodium citrate 1.5 kg / t) is first added to the raw ore slurry, and then a composite collector (N-allyl derivative 350 g / t + diphenylthiourea 120 g / t) is added for flotation separation to obtain indium-rich concentrate (In 0.89%, recovery rate 92.87%) and flotation tailings.

[0046] The final indicators are as follows: Zn recovery rate 96.02%; The total recovery rate of In was 94.87%; The total recovery rate of Ag was 90.58%; The residual Zn content in the kiln slag is 0.34%, and the residual In content is 0.030%.

[0047] Comparative Example 1 The steps are basically similar to those in Example 1, except that the inhibitor in step 2 is only sodium thiosulfate, with an amount of 2000 kg / t.

[0048] The final indicators are as follows: Zn recovery rate: 88.5%; The total recovery rate of In was 90.21%; The total recovery rate of Ag was 87.26%; The residual Zn content in the kiln slag is 0.54%, and the residual In content is 0.03%.

[0049] Comparative Example 2 The steps are basically similar to those in Example 1, except that the inhibitor in step 2 is only sodium citrate, with an amount of 1000 g / t.

[0050] The final indicators are as follows: Zn recovery rate was 86.39%; The total recovery rate of In was 87.26%; The total recovery rate of Ag was 88.69%; The residual Zn content in the kiln slag is 0.66%, and the residual In content is 0.12%.

[0051] Comparative Example 3 The steps are basically similar to those in Example 1, except that the collector in step 2 is only diphenylthiourea in an amount of 200 g / t.

[0052] The final indicators are as follows: Zn recovery rate 87.87%; The total recovery rate of In was 88.39%; The total recovery rate of Ag was 85.69%; The residual Zn content in the kiln slag is 0.84%, and the residual In content is 0.76%.

[0053] Comparative Example 4 The steps are basically similar to those in Example 1, except that the collector in step 2 is only N-allyl-O-isobutylthiocarbamate, with an amount of 400 g / t.

[0054] The final indicators are as follows: Zn recovery rate: 89.23%; The total recovery rate of In was 85.32%; The total recovery rate of Ag was 82.01%; The residual Zn content in the kiln slag is 0.61%, and the residual In content is 0.66%.

[0055] Comparative Example 5 The steps are basically similar to those in Example 1, except that the collector in step 2 is xanthate.

[0056] The final indicators are as follows: Zn recovery rate: 73.01%; The total recovery rate of In was 72.05%; The total recovery of Ag was 70.23%; The residual Zn content in the kiln slag is 2.36%, and the residual In content is 1.59%.

[0057] Comparative Example 6 The steps are basically similar to those in Example 1, with the only difference being that the collector in step 2 is black medicine.

[0058] The final indicators are as follows: Zn recovery rate: 70.23%; The total recovery rate of In was 69.86%; The total recovery of Ag was 68.56%; The residual Zn content in the kiln slag is 3.68%, and the residual In content is 2.87%.

[0059] Comparative Example 7 The steps are basically similar to those in Example 1, except that in step 3, the flotation tailings are only blended with coal and subjected to microwave treatment.

[0060] The final indicators are as follows: Zn recovery rate: 79.61%; The total recovery rate of In was 75.08%; The total recovery rate of Ag was 72.32%; The residual Zn content in the kiln slag is 1.25%, and the residual In content is 1.03%.

[0061] Comparative Example 8 The steps are basically similar to those in Example 1, except that there is no step 3.

[0062] The final indicators are as follows: Zn recovery rate: 65.23%; Total recovery of In: 59.26%; Total Ag recovery: 58.28%; Residual Zn in kiln slag: 5.28%, residual In: 6.20%.

[0063] As can be seen from the above, the embodiments of the present invention provide a composite collector, a combined reagent and a method for recovering indium from zinc leaching hazardous waste residue. For zinc leaching hazardous waste residue with an indium content of 0.056% to 0.10% and a zinc content of 8.62% to 11.39%, the present invention proposes to adopt a new flotation-microwave enhanced roasting synergistic process, combined with a combined reagent of a composite inhibitor and a composite collector, to significantly improve the recovery rate of indium, zinc and silver. The specific steps include: high-efficiency flotation: after grinding, composite depressants and new indium-selective collectors are used for flotation to achieve efficient indium enrichment; microwave-enhanced roasting: the flotation tailings and anthracite / coke are treated with microwave irradiation and high-temperature roasting to promote the volatilization of indium and zinc in zinc leaching hazardous waste, so that the zinc recovery rate is greater than 96% and the indium recovery rate is greater than 94%. In addition, silver can also be recovered from indium-rich concentrate and roasting dust, with a total silver recovery rate of greater than 90%; after the zinc leaching hazardous waste is treated through the above processes, the residual zinc content in the kiln slag is less than 0.35%, and the residual indium content is less than 0.03%. After desulfurization, the flue gas meets the emission standards of GB 25466-2016.

[0064] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A composite collector for recovering indium from zinc leaching hazardous waste residue, characterized in that: The composite collector includes a main collector and an auxiliary collector, wherein: the mass ratio of the main collector to the auxiliary collector is (3:1) to (5:1), the main collector includes N-allyl-O-isobutylthiocarbamate, and the auxiliary collector includes diphenylthiourea.

2. A combined reagent for recovering indium, zinc and silver from zinc leaching hazardous waste residue, characterized in that: The combined agent comprises a composite inhibitor and the composite collector according to claim 1, wherein the composite inhibitor comprises sodium thiosulfate and sodium citrate.

3. The combined pharmaceutical preparation according to claim 2, characterized in that The composite inhibitor consists of sodium thiosulfate and sodium citrate, and the mass ratio of sodium thiosulfate to sodium citrate is (2:1) to (3:1).

4. The combination drug according to claim 2, characterized in that The composite collector consists of N-allyl-O-isobutylthiocarbamate and diphenylthiourea, and the mass ratio of N-allyl-O-isobutylthiocarbamate to diphenylthiourea is (3:1) to (5:1).

5. A method for recovering indium, zinc and silver from zinc leaching hazardous waste residue, characterized in that: The method comprises: utilizing the combined reagent according to any one of claims 2 to 4 and adopting a combined process of flotation separation and microwave-enhanced roasting to recover indium, zinc and silver from the zinc leaching hazardous waste residue.

6. The method according to claim 5, characterized in that The following steps are involved: A zinc leaching hazardous waste slag slurry is provided, and a composite depressant and a composite collector are successively added to the slurry for flotation separation to obtain indium-rich concentrate and flotation tailings. The flotation tailings are then mixed with a reducing agent and subjected to microwave-enhanced roasting treatment. The roasting dust is collected by bag dust collection to recover indium and zinc.

7. The method according to claim 6, characterized in that The method further comprises: recovering silver from the indium-rich concentrate and the roasting fumes.

8. The method according to claim 6, characterized in that The flotation separation steps are as follows: after adjusting the pH value of the slurry with sulfuric acid, a composite depressant and a composite collector are added to the slurry in sequence to obtain indium-rich concentrate and flotation tailings, wherein: The slurry is prepared by filtering zinc leaching hazardous waste slag to a moisture content of <25%, and then grinding the ore to -0.074 mm, accounting for 82±3% of the total material, wherein the indium content of the zinc leaching hazardous waste slag is 0.056%~0.10%, and the zinc content is 8.62%~11.39%; The dosage of sodium thiosulfate in the composite inhibitor is 1.5kg / t-2kg / t, and the dosage of sodium citrate is 0.5kg / t-1kg / t; The amount of N-allyl-O-isobutylthiocarbamate in the composite collector is 300g / t-500g / t, and the amount of diphenylthiourea is 100g / t-200g / t; The flotation pH value is 4.5~6.5; The flotation process is two roughing selections + three cleaning selections + two scavenging selections.

9. The method according to claim 6, characterized in that The microwave-enhanced roasting process comprises the following steps: mixing the flotation tailings with a reducing agent, sequentially subjecting the mixture to microwave irradiation and roasting, collecting the roasting dust through a bag filter to recover indium and zinc, and subjecting the roasting flue gas from which indium and zinc are recovered to desulfurization treatment and then discharging the flue gas in compliance with the GB25466-2016 standard, wherein: The flotation tailings are mixed with anthracite and coke in a mass ratio of 1:(0.2-0.3):(0.1-0.15); The microwave irradiation treatment has a frequency of 4 GHz and a duration of 5-10 minutes, and the specific surface area of ​​the flotation tailings is increased by more than 50% after the microwave irradiation treatment; The roasting temperature of the roasting treatment is 1100±20° C., the time is 0.5h-1h, and the rotation speed of the rotary kiln during the roasting treatment is 0.5r / min-1r / min.

10. The method according to any one of claims 6 to 9, characterized in that: The indium grade of the indium-rich concentrate obtained by flotation separation is >0.8%, the indium recovery rate is >92%, the zinc recovery rate after microwave roasting treatment is >96%, the total indium recovery rate is >94%, the total silver recovery rate is >90%, the residual zinc in the kiln slag is <0.35%, and the residual indium is <0.03%.

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