Antimony alkali residue recovery method

Abstract

The invention provides an antimony alkaline residue recovery method. According to the process, microwave activation and citric acid leaching technologies are combined, so that the energy consumption is reduced by 40% while efficient recovery (gt, 95%) of antimony is realized; through TBP gradient extraction, the recovery rate reaches 98%, and hazardous waste is avoided; zero waste discharge is achieved, tailings are completely converted into qualified building materials, and the waste water recycling rate is 95% or above; the economic benefit is obvious, the treatment cost is about 1200 yuan / ton, and the payback period is less than 3 years; mature industrial equipment is adopted, and large-scale application conditions are achieved; the process stability is ensured by the closed cycle design; perfect safety measures are prepared, and the final product meets the national environmental protection and building material standards.

Description

Technical Field

[0001] The present invention application relates to the technical field of metallurgy, and particularly relates to a method for recycling antimony-alkali slag. Background Art

[0002] Antimony-alkali slag is a typical hazardous solid waste generated in the processes of antimony smelting, lead-zinc smelting, and electronic waste treatment. Its main components include antimony oxide (Sb2O3 / Sb2O5), silicate, heavy metals (arsenic, lead, cadmium), and residual lye. With the growth of global antimony consumption (annual average growth rate of about 4.2%), the stockpile of antimony-alkali slag continues to rise, and the annual output in China alone has exceeded 5 million tons. Existing antimony-alkali slag treatment technologies generally have problems such as low recovery efficiency, high risk of secondary pollution, and single resource utilization path, which seriously restrict the sustainable development of the industry. Traditional processes mostly use high-temperature roasting (600 - 800 °C) to break the silicate coating structure, but this process relies on external heat source conduction and has significant defects: high energy consumption, consuming 1200 - 1500 kWh of electric energy per ton of roasted slag, accounting for more than 60% of the total energy consumption of the whole process, and high temperature causes partial volatilization of antimony oxide (loss rate of 5 - 8%); low activation efficiency, silicate minerals only dissociate on the surface under static heating, and internal antimony is difficult to release, and the subsequent leaching rate is limited to less than 80%; pollution diffusion, the high-temperature environment exacerbates the oxidation and volatilization of arsenic (the boiling point of As2O3 is 460 °C), generating highly toxic arsenic-containing dust, and a complex tail gas purification system needs to be configured, increasing the pollution treatment cost (about ￥500 / ton of slag).

[0003] The mainstream hydrometallurgical technology adopts a full leaching strategy with strong acids (6 - 8 mol / L HCl or H2SO4). Although antimony can be extracted, it faces multiple bottlenecks: poor selectivity, heavy metals such as arsenic, lead, and cadmium are simultaneously dissolved at high acidity (As leaching rate > 40%), resulting in a sharp increase in the subsequent purification load. Multiple stages of sulfide precipitation (Na2S or FeS) are required, generating arsenic-containing hazardous waste (As2S3 content > 15%), and the disposal cost is as high as ￥800 - 1000 per ton; acid mist hazard, chlorine and HCl gases are generated by the volatilization of hydrochloric acid, and the operating environment is harsh (corrosion-resistant closed equipment is required), and the acid consumption reaches 0.8 - 1.2 tons per ton of slag, and the reagent cost accounts for more than 35%; antimony hydrolysis loss, the traditional process ignores the dynamic regulation of pH. When the pH of the leaching solution > 1.5, antimony is easily hydrolyzed to form SbOCl precipitate (solubility is only 0.02 g / L), resulting in a 10 - 15% decrease in the antimony recovery rate. The existing separation technologies mainly rely on sulfide precipitation - pyrometallurgical refining, with obvious shortcomings: multiple-stage precipitation is inefficient. To remove impurities such as As and Pb, sodium sulfide and lime milk need to be added successively to adjust the pH. The process takes more than 8 hours, and the phenomenon of coprecipitation of antimony and impurities is serious (loss rate 12 - 18%); the product added value is low. The final product is antimony concentrate (Sb 70 - 85%), and it needs to be remelted (1200 °C) to purify it to more than 99%, additionally increasing the energy consumption by 800 - 1000 kWh per ton; the chain accumulation of hazardous waste, each ton of slag generates arsenic-containing filter residue (300 - 400 kg), acidic wastewater (8 - 10 m³), and waste residue for waste gas purification (50 - 80 kg), and the comprehensive hazardous waste rate > 45%, far exceeding the limit of the "National Hazardous Waste List" (HW48 category).

[0004] Traditional processes treat leaching residues in a rough manner, with prominent environmental risks: heavy metal residues in the residues under the landfill method (As 5-8%, Pb 0.5-1.2%) are easily leaked under rainwater leaching, and the As concentration in the leachate reaches 2-5 mg / L (20-50 times the limit of GB 5085.3-2007); in terms of simple solidification, some companies use cement solidification, but the silicate matrix has weak fixation ability for As³⁺ / Sb³⁺ (solidification rate <70%) and poor long-term stability; the cost of wastewater treatment is high, and acidic wastewater requires multi-stage treatment of neutralization-precipitation-membrane filtration, with a treatment cost of RMB 30-50 per ton of water, and membrane fouling and clogging occur frequently, with a reuse rate of less than 50%. The existing technology is difficult for small and medium-sized enterprises to bear due to the complex process and large equipment investment (rotary kiln + multi-stage purification system > ￥50 million / 10,000 ton line): the cost is inverted, the comprehensive cost of processing a ton of slag is ￥1,800-2,200, while the selling price of antimony concentrate is only ￥15,000-20,000 / ton (the market price of metallic antimony is ￥30,000 / ton), and the profit margin is <10%; policy risks, environmental protection taxes (￥1,000-1,500 / ton of hazardous waste) and carbon emission costs (about ￥200 / ton of CO2) further compress profit margins; technology is locked, the iteration of traditional processes has stagnated, and 90% of the patents in the past decade are local optimizations (such as leaching agent replacement), lacking systematic innovation.

[0005] The existing antimony alkali slag treatment technology is limited by core defects such as high energy consumption, low selectivity, chain generation of hazardous waste and poor economic efficiency, making it difficult to meet the green smelting needs under the "dual carbon" goal. The industry urgently needs to develop a new recycling process that is efficient, clean, fully resourced and low-cost, to break the dilemma of "recycling means pollution" and promote the transformation of the antimony industry to a circular economy model. Summary of the invention

[0006] In order to solve or partially solve the problems existing in the related art, the present invention provides a method for recovering antimony alkali slag.

[0007] The following steps are involved: (1) Microwave activation pretreatment: crush the antimony alkali slag to a particle size of ≤0.2 mm, and roast it at 300-400°C for 10-20 minutes under the conditions of microwave frequency of 2.0-3.0 GHz and power of 3-7 kW; (2) Acidic oxidation leaching: the product of step (1) is mixed with a mixed acid solution at a liquid-to-solid ratio of 5:1-7:1, wherein the mixed acid is hydrochloric acid and citric acid in a volume ratio of 3:1-5:1, 0.3%-0.7% H2O2 is added, and leaching is carried out at 75-85°C and pH 1.4-1.6 for 1.5-2.5 hours; (3) Gradient extraction separation: adjust the pH of the leaching solution to 1.8-2.2, add TBP-kerosene extractant at a ratio of organic phase: aqueous phase = 1:3-1:5, and use 3%-7% sulfuric acid solution for back extraction; (4) Antimony extraction by electrodeposition: Electrolyze the stripping solution under the conditions of current density of 150 - 250 A / m² and cell voltage of 2.5 - 3.5 V, and control the temperature at 30 - 50 °C; (5) Resource utilization of tailings: Mix the leaching residue and auxiliary materials at a mass ratio of 0.5:1 - 1.5:1, add 5% - 15% binder, and cure in an environment with humidity ≥ 85% after pressing into shape; (6) Waste liquid recycling: Recover HCl with a concentration ≥ 80% by vacuum distillation of waste acid, and reuse the wastewater after neutralization - membrane filtration.

[0008] Further, in step (1), the microwave power is 5 kW, the roasting temperature is 380 °C, and the roasting time is 15 minutes.

[0009] Further, in step (2), the liquid - solid ratio is 6:1, the volume ratio of hydrochloric acid to citric acid is 4:1, the addition amount of H2O2 is 0.5%, the leaching temperature is 80 °C, and the pH is 1.5.

[0010] Further, in step (3), the volume ratio of the organic phase to the aqueous phase is 1:4, and the stripping sulfuric acid concentration is 5%.

[0011] Further, in step (4), the current density is 200 A / m², the cell voltage is 3.0 V, and the electrolysis temperature is 40 °C.

[0012] Further, in step (5), the auxiliary material is fly ash, the mass ratio of the residue to fly ash is 1:1, the binder is cement and the addition amount is 10%, the molding pressure is 15 MPa, and the curing humidity > 90%.

[0013] Further, in step (6), the purity of the recovered HCl ≥ 85%, the membrane filtration uses a nanofiltration membrane with a retention molecular weight of 200 - 400 Da.

[0014] Further, in step (3), the volume ratio of TBP to kerosene is 1:4, and the stripping time is 15 minutes.

[0015] Further, in step (5), the heavy metal sulfide precipitation uses sodium sulfide with an addition amount of 0.2 kg / kg slag.

[0016] Further, in step (2), the antimony ion concentration in the leaching solution ≥ 50 g / L, and in step (4), the purity of the cathode antimony ≥ 99.5%.

[0017] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit this invention application.

[0018] The beneficial technical effects of the present invention:

[0019] This process combines microwave activation and citric acid leaching technologies to achieve efficient antimony recovery (>95%) while reducing energy consumption by 40%; through TBP gradient extraction, a recovery rate of 98% is achieved, avoiding the generation of hazardous waste; zero waste discharge is realized, the tailings are completely converted into qualified building materials, and the wastewater reuse rate is over 95%; the economic benefits are remarkable, the treatment cost is about 1200 yuan / ton, and the investment payback period is less than 3 years; mature industrial equipment is adopted, and it has the conditions for large-scale application; the closed-loop circulation design ensures the process stability; perfect safety measures are equipped, and the final products meet the national environmental protection and building material standards. Detailed implementation manners

[0020] The optional implementation manners of the present invention application will be described in more detail below. Although the optional implementation manners of the present invention application are described, it should be understood that the present invention application can be implemented in various forms and should not be limited by the implementation manners described herein. On the contrary, these implementation manners are provided to make the present invention application more thorough and complete, and to be able to fully convey the scope of the present invention application to those skilled in the art.

[0021] The present invention application provides a method for recovering antimony alkali slag.

[0022] It includes the following steps: (1) Microwave activation pretreatment: Crush the antimony alkali slag to a particle size ≤ 0.2 mm, and roast it at 300 - 400 °C for 10 - 20 minutes under the conditions of a microwave frequency of 2.0 - 3.0 GHz and a power of 3 - 7 kW; Microwaves excite polar molecules (such as H2O, SiO4⁻, etc.) in the antimony alkali slag through a high-frequency electromagnetic field (2.45 GHz), causing the molecules to vibrate and rub violently, and quickly generating heat energy (300–400 °C). This endogenous heating can efficiently destroy the silicate coating structure, expose and activate antimony oxides (Sb2O3 / Sb2O5), and at the same time avoid energy consumption waste caused by uneven heat conduction in traditional roasting.

[0023] (2) Acidic oxidation leaching: Mix the product of step (1) with a mixed acid solution at a liquid-solid ratio of 5:1 - 7:1. The mixed acid is a hydrochloric acid to citric acid volume ratio of 3:1 - 5:1, add 0.3% - 0.7% H2O2, and leach for 1.5 - 2.5 hours at 75 - 85 °C and pH 1.4 - 1.6; In the mixed acid (HCl + citric acid), H⁺ dissolves antimony oxides to generate Sb³⁺ / Sb 5 ⁺ ions, while citric acid complexes antimony ions through carboxyl groups, inhibits their hydrolysis and precipitation, and at the same time reduces the volatilization of HCl. H2O2 is used as an oxidant to oxidize part of Sb³⁺ to Sb 5⁺ (Reaction formula: Sb2O3 + H2O2 → Sb2O5 + H2O), to improve the leaching rate of antimony. By precisely controlling the pH = 1.5, the dissolution of arsenic (As³⁺ is easily soluble when pH > 2) and lead (Pb²⁺ precipitates in the form of PbCl2 at low pH) is inhibited, and the selective separation of antimony is achieved.

[0024] (3) Gradient extraction and separation: Adjust the pH of the leaching solution to 1.8 - 2.2, add the TBP-kerosene extractant according to the organic phase: aqueous phase = 1:3 - 1:5, and use a sulfuric acid solution with a concentration of 3% - 7% for back extraction; Tributyl phosphate (TBP) forms a hydrophobic complex with Sb 5 ⁺ in an acidic medium (Reaction formula: SbCl6⁻ + 3TBP → [SbCl3·3TBP]), and is preferentially extracted into the organic phase, while impurities such as Cu²⁺ and Zn²⁺ remain in the aqueous phase due to their weak complexing ability. During back extraction, dilute sulfuric acid (H2SO4) provides a high concentration of H⁺ to destroy the complex structure ([SbCl3·3TBP]+ H2SO4→ Sb³⁺ + 3TBP + SO4²⁻ + Cl⁻), releasing antimony ions into the aqueous phase, and the organic phase is recycled after regeneration.

[0025] (4) Electroplating for antimony extraction: Electrolyze the back extraction solution under the conditions of a current density of 150 - 250 A / m² and a cell voltage of 2.5 - 3.5 V, and control the temperature at 30 - 50 °C; Sb³⁺ in the back extraction solution is reduced to metallic antimony on the surface of the cathode (titanium plate) under the action of a direct current electric field (Reaction formula: Sb³⁺ + 3e⁻ → Sb), while the lead anode undergoes an oxidation reaction (Pb → Pb²⁺ + 2e⁻). By controlling the current density (200 A / m²) and temperature (40 °C), the crystal morphology of antimony is optimized to avoid short-circuit problems caused by dendrite growth, ensuring that the purity of cathode antimony reaches over 99.5%.

[0026] (5) Resource utilization of tailings: Mix the leaching residue with auxiliary materials at a mass ratio of 0.5:1 - 1.5:1, add 5% - 15% binder, and cure in an environment with a humidity of ≥ 85% after molding; Add Na2S to the residual leaching solution to form insoluble sulfides (such as CuS, ZnS, solubility product Ksp≈10⁻³ 6 ) with Cu²⁺, Zn²⁺, etc., and achieve harmlessness through precipitation separation.

[0027] The leaching residue (SiO2, CaO) and the active Al2O3 in fly ash form a dense structure in the cement hydration reaction (Ca(OH)2 + SiO2 →C-S-H gel), physically wrapping and chemically solidifying the residual heavy metals.

[0028] (6) Waste liquid recycling: The waste acid is recycled by vacuum distillation to recover HCl with a concentration ≥ 80%, and the waste water is recycled through neutralization - membrane filtration.

[0029] Vacuum distillation (80 °C) realizes the recovery of HCl gas through the boiling point difference between HCl and water (HCl boiling point - 85 °C, water 100 °C), and after condensation, it is recycled, with an acid recovery rate > 85%.

[0030] In an embodiment of the present application, in step (1), the microwave power is 5 kW, the roasting temperature is 380 °C, and the roasting time is 15 minutes.

[0031] In an embodiment of the present application, in step (2), the liquid - solid ratio is 6:1, the volume ratio of hydrochloric acid to citric acid is 4:1, the addition amount of H2O2 is 0.5%, the leaching temperature is 80 °C, and the pH is 1.5.

[0032] In an embodiment of the present application, in step (3), the volume ratio of the organic phase to the aqueous phase is 1:4, and the concentration of the stripping sulfuric acid is 5%.

[0033] In an embodiment of the present application, in step (4), the current density is 200 A / m², the cell voltage is 3.0 V, and the electrolysis temperature is 40 °C.

[0034] In an embodiment of the present application, in step (5), the auxiliary material is fly ash, the mass ratio of the residue to fly ash is 1:1, the binder is cement and the addition amount is 10%, the forming pressure is 15 MPa, and the curing humidity > 90%.

[0035] In an embodiment of the present application, in step (6), the purity of the recovered HCl ≥ 85%, the membrane filtration uses a nanofiltration membrane, and the molecular weight cut - off is 200 - 400 Da.

[0036] In an embodiment of the present application, in step (3), the volume ratio of TBP to kerosene is 1:4, and the stripping time is 15 minutes.

[0037] In an embodiment of the present application, in step (5), the heavy metal sulfide precipitation uses sodium sulfide, and the addition amount is 0.2 kg / kg slag.

[0038] In an embodiment of the present application, in step (2), the concentration of antimony ions in the leaching solution ≥ 50 g / L, and in step (4), the purity of the cathode antimony ≥ 99.5%.

[0039] For the sake of clarity, the following is a detailed description through the following examples.

[0040] Example 1: Microwave activation: The particle size of the crushed slag is 0.2 mm, the microwave frequency is 3.0 GHz, the power is 7 kW, the temperature is 400 °C, and the roasting time is 20 minutes; Acid leaching: liquid-solid ratio 7:1, hydrochloric acid:citric acid = 5:1, H2O2 addition amount 0.7%, temperature 85°C, pH = 1.6, leaching for 2.5 hours; Gradient extraction: pH = 2.2, organic phase:aqueous phase = 1:3, stripping sulfuric acid concentration 7%; Electrodeposition: current density 250 A / m², cell voltage 3.5 V, temperature 50°C; Resource utilization of tailings: residue:fly ash = 1.5:1, cement addition amount 15%, pressure 17 MPa; Waste liquid recycling: HCl recovery concentration 80%, nanofiltration membrane molecular weight cut-off 400 Da.

[0041] Example 2: Microwave activation: particle size of crushed slag 0.15 mm, microwave frequency 2.45 GHz, power 5 kW, temperature 380°C, roasting for 15 minutes; Acid leaching: liquid-solid ratio 6:1, hydrochloric acid:citric acid = 4:1, H2O2 addition amount 0.5%, temperature 80°C, pH = 1.5, leaching for 2 hours; Gradient extraction: pH = 2.0, organic phase:aqueous phase = 1:4, stripping sulfuric acid concentration 5%; Electrodeposition: current density 200 A / m², cell voltage 3.0 V, temperature 40°C; Resource utilization of tailings: residue:fly ash = 1:1, cement addition amount 10%, pressure 15 MPa; Waste liquid recycling: HCl recovery concentration 85%, nanofiltration membrane molecular weight cut-off 300 Da.

[0042] Example 3: Microwave activation: particle size of crushed slag 0.1 mm, microwave frequency 2.0 GHz, power 3 kW, temperature 300°C, roasting for 10 minutes; Acid leaching: liquid-solid ratio 5:1, hydrochloric acid:citric acid = 3:1, H2O2 addition amount 0.3%, temperature 75°C, pH = 1.4, leaching for 1.5 hours; Gradient extraction: pH = 1.8, organic phase:aqueous phase = 1:5, stripping sulfuric acid concentration 3%; Electrodeposition: current density 150 A / m², cell voltage 2.5 V, temperature 30°C; Resource utilization of tailings: residue:fly ash = 0.5:1, cement addition amount 5%, pressure 13 MPa; Waste liquid recycling: HCl recovery concentration 83%, nanofiltration membrane molecular weight cut-off 200 Da.

[0043] Result comparison and analysis

[0044] Test example Raw materials: Antimony-alkali slag of the same batch (composition: Sb 12.5%, As 3.2%, Pb 1.8%, SiO2 35%, CaO 20%), treatment capacity 100 kg; Traditional process: Roasting: Rotary kiln at 650°C for 2 hours; Leaching: 6 mol / L HCl, liquid-solid ratio 5:1, at 80°C for 4 hours; Precipitation: Sulfide precipitation with Na2S, and antimony concentrate (Sb 85%) is obtained after drying the filter residue; Waste residue: Landfilled as hazardous waste, and the wastewater is neutralized and discharged.

[0045] Process of Example 2: Microwave activation (380°C for 15 minutes) → Selective leaching (HCl + citric acid) → Gradient extraction (TBP) → Electroplating → Making bricks from tailings → Closed-loop recycling of waste liquid. Comparison of key indicators

[0046] Verification of economic benefits

[0047]

[0048] Test Example 2 Testing method Sample: Building materials bricks produced by the process of Example 2 (cured for 28 days); Standard: "Solid Waste - Extraction Procedure for Toxicity Characteristic - Acetic Acid Buffer Solution Method" (HJ / T 300 - 2007); Conditions: Liquid-solid ratio 20:1, pH = 2.88 ± 0.05, tumbling and shaking for 18 hours; Detection: Determination of the concentration of the leaching solution by ICP-MS.

[0049] 2. Test results

[0050] Note: The measured values are far lower than the national standard limits (As < 1%, Pb < 2.5%), and are lower than the industrial application safety thresholds of the groundwater Class III standard (As ≤ 0.05 mg / L, Pb ≤ 0.05 mg / L).

Claims

1. A method for recovering antimony alkali slag, characterized in that, It includes the following steps: (1) Microwave activation pretreatment: Crush the antimony-alkali residue to a particle size of ≤0.2 mm, and calcine it at 300-400 °C for 10-20 minutes under the conditions of a microwave frequency of 2.0-3.0 GHz and a power of 3-7 kW; (2) Acidic oxidation leaching: Mix the product of step (1) with a mixed acid solution at a liquid-solid ratio of 5:1-7:

1. The mixed acid is a hydrochloric acid to citric acid volume ratio of 3:1-5:1, add 0.3%-0.7% H2O2, and leach at 75-85 °C and pH 1.4-1.6 for 1.5-2.5 hours; (3) Gradient extraction and separation: Adjust the pH of the leaching solution to 1.8-2.2, add a TBP-kerosene extractant at an organic phase:aqueous phase = 1:3-1:5, and use a sulfuric acid solution with a concentration of 3%-7% for back extraction; (4) Electrodeposition for antimony extraction: Electrolyze the back extraction solution under the conditions of a current density of 150-250 A / m² and a cell voltage of 2.5-3.5 V, and control the temperature at 30-50 °C; (5) Resource utilization of tailings: Mix the leaching residue with auxiliary materials at a mass ratio of 0.5:1-1.5:1, add 5%-15% binder, press into shape and cure in an environment with a humidity of ≥85%; (6) Waste liquid recycling: Recover HCl with a concentration of ≥80% from waste acid by vacuum distillation, and reuse the waste water after neutralization-membrane filtration.

2. The method according to claim 1, wherein: In step (1), the microwave power is 5 kW, the calcination temperature is 380 °C, and the calcination time is 15 minutes.

3. The method according to claim 1, characterized in that: In step (2), the liquid-solid ratio is 6:1, the volume ratio of hydrochloric acid to citric acid is 4:1, the addition amount of H2O2 is 0.5%, the leaching temperature is 80 °C, and the pH is 1.

5.

4. The method according to claim 1, characterized in that: In step (3), the volume ratio of the organic phase to the aqueous phase is 1:4, and the back extraction sulfuric acid concentration is 5%.

5. The method according to claim 1, wherein: In step (4), the current density is 200 A / m², the cell voltage is 3.0 V, and the electrolysis temperature is 40 °C.

6. The method according to claim 1, wherein: In step (5), the auxiliary material is fly ash, the mass ratio of the residue to fly ash is 1:1, the binder is cement and the addition amount is 10%, the forming pressure is 15 MPa, and the curing humidity is >90%.

7. The method according to claim 1, wherein: In step (6), the purity of the recovered HCl is ≥85%, the membrane filtration uses a nanofiltration membrane, and the molecular weight cut-off is 200-400 Da.

8. The method according to claim 1, characterized in that: In step (3), the volume ratio of TBP to kerosene is 1:4, and the back extraction time is 15 minutes.

9. The method according to claim 1, characterized in that: In step (5), the heavy metal sulfide precipitation uses sodium sulfide, and the addition amount is 0.2 kg / kg slag.

10. The method according to claim 1, characterized in that: In step (2), the antimony ion concentration in the leaching solution is ≥50 g / L, and in step (4), the purity of the cathode antimony is ≥99.5%.

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