A green process for preparing 4N fine bismuth from bismuth-containing waste material without chlorine and with short process flow

Abstract

This invention discloses a green, chlorine-free, short-process technology for preparing 4N refined bismuth from bismuth-containing waste, belonging to the field of green hydrometallurgical technology for rare and dispersed metals. Addressing the industry pain points of traditional pyrometallurgical bismuth extraction, such as extremely high energy consumption, severe heavy metal flue gas pollution, and large equipment investment, as well as the industry pain points of traditional hydrochloric acid hydrometallurgical bismuth extraction involving chloride ion corrosion of equipment, difficult wastewater treatment, and the generation of highly toxic hydrogen sulfide gas during sulfidation impurity removal, this invention employs a combined short-process hydrometallurgical method: chlorine-free sulfuric acid-citric acid composite atmospheric pressure leaching, non-toxic selective impurity removal with organic sulfiding agents, low-temperature constant current electrowinning, low-temperature vacuum refining, and closed-loop wastewater recycling. This process involves no open flame high-temperature smelting, no chloride ion medium, and no toxic hydrogen sulfide gas leakage, completely avoiding the environmental and safety risks of traditional processes. Process verification shows that the bismuth leaching rate of this invention is ≥92%, the comprehensive removal rate of impurities such as copper, lead, and silver is ≥95%, and the purity of the final prepared metallic bismuth is ≥99.99%. This process is streamlined, the equipment is modular, the initial investment is low, and the operation and maintenance costs are small. It is perfectly suited for small and medium-sized entrepreneurial modular production lines, and its advantages in greenness, industrialization, and economy are prominent.

Description

Technical Field

[0001] This invention relates to the fields of regenerated metallurgy and rare and dispersed metal purification and resource utilization technology, specifically to an industrial process for the green and short-process recovery of 4N high-purity bismuth from lead anode mud, copper anode mud, bismuth-containing metallurgical slag, and waste bismuth alloy waste. Background Technology

[0002] Bismuth is an important strategic rare metal, widely used in biomedicine, metallurgical additives, electronic semiconductors, new energy, and other fields, with consistently stable industrial demand. Currently, domestic processes for recycling and purifying bismuth-containing waste are mainly divided into two categories: pyrometallurgical smelting and hydrochloric acid wet processing. Both mainstream processes have significant drawbacks.

[0003] Pyrometallurgical bismuth extraction relies on large blast furnaces and smelting furnaces for high-temperature smelting and purification, with operating temperatures exceeding 1000℃. This results in extremely high energy consumption, and the smelting process generates a large amount of lead and bismuth-containing heavy metal fumes, causing severe air pollution. Environmental protection equipment is bulky and costly. Furthermore, pyrometallurgical equipment consists of large-scale industrial equipment with an initial investment of tens of millions of yuan, making it suitable only for large-scale smelting enterprises and unable to meet the needs of small and medium-sized production.

[0004] Hydrochloric acid wet bismuth extraction uses high-concentration hydrochloric acid as the leaching medium. The large amount of chloride ions in the system severely corrodes the production equipment, significantly shortening its lifespan and increasing replacement costs. Furthermore, the subsequent treatment of chlorinated wastewater is complex, difficult to meet standards, and incurres high maintenance costs. In addition, traditional processes use sodium sulfide for impurity precipitation and removal, but the reaction continuously generates highly toxic hydrogen sulfide gas, posing extremely high safety risks and significant environmental control challenges.

[0005] Searching revealed that existing publicly available patents and technical documents all focus on optimizing large-scale pyrometallurgical processes, improving hydrochloric acid system parameters, and fine-tuning impurity removal reagents. There is currently no complete industrial-scale bismuth extraction process that is suitable for small and medium-sized production lines, chlorine-free, flame-free, hydrogen sulfide-free, and modular with a short process, indicating a significant technological and market gap. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing pyrometallurgical and hydrometallurgical bismuth extraction processes, such as high pollution, high energy consumption, high investment, and poor safety, and to provide a fully hydrometallurgical, chlorine-free, green, non-toxic, short-process, low-cost, modular, and mass-producible refined bismuth preparation process.

[0007] This invention abandons the traditional open flame smelting and hydrochloric acid leaching system, and adopts a sulfuric acid-citric acid chlorine-free composite green leaching agent to achieve high-efficiency leaching at low temperature and normal pressure; it selects mercaptoacetate organic sulfurizing agent to replace traditional sodium sulfide to achieve non-toxic selective impurity removal and completely eliminate the generation of hydrogen sulfide gas; it is equipped with low-temperature electrowinning and small-scale low-temperature vacuum refining equipment to simplify the process and reduce energy consumption, while supporting closed-loop wastewater circulation throughout the entire process to achieve green production throughout the entire process.

[0008] The process of this invention is adaptable to various bismuth-containing waste materials, has strong versatility, stable and controllable process parameters, high product purity, excellent recovery rate, and strong industrial applicability. Detailed Implementation

[0009] Lead smelting anode mud was selected as raw material, containing 8.2% bismuth, with copper, lead, silver, and iron as the main impurities. The raw material was crushed and sieved to an 80-mesh uniform powder. A composite leaching agent was prepared: 9% dilute sulfuric acid + 3.5% citric acid + the balance deionized water, which was chlorine-free and non-corrosive. The liquid-to-solid ratio was controlled at 3:1, the leaching temperature was 55℃, and the leaching was carried out under normal pressure with stirring for 3 hours. After leaching, plate and frame filter press was used for separation to obtain a clear bismuth-rich filtrate.

[0010] At room temperature, 2% by volume of mercaptoacetate organic sulfurizing agent was added to the bismuth-rich filtrate, the pH of the system was adjusted to 2.0, and the reaction was carried out at a constant temperature with stirring for 30 minutes. Copper, lead and silver impurities were selectively precipitated, and the impurities were removed by filtration. The overall impurity removal rate was 96.2%, and a high-purity bismuth-rich purified solution was obtained.

[0011] The purified solution was fed into a bismuth electrodeposition apparatus, and the electrodeposition temperature was controlled at 45°C and constant current electrodeposition was performed to obtain crude bismuth with a dense surface. The crude bismuth was then fed into a modular vacuum refining furnace, and the vacuum degree was controlled at 0.085 MPa and the refining temperature at 300°C. The furnace was kept at a constant temperature for 2 hours, and after cooling, high-purity refined bismuth was obtained.

[0012] Testing showed that the purity of the refined bismuth prepared in this embodiment was 99.994%, and the overall bismuth recovery rate was 90.7%; all wastewater was collected, treated, and recycled, with no external discharge.

[0013] Copper smelting anode mud was selected as raw material, with a bismuth content of 3.1%. The mud was crushed and sieved to 80 mesh, and leached for 2.5 hours at room temperature and pressure using the same proportion of chlorine-free composite leaching agent. Subsequent impurity removal, electrowinning, and refining process parameters were consistent with those in Example 1. Testing showed that the purified bismuth purity of the product was 99.991%, the overall recovery rate was 89.5%, and the process stability was good.

[0014] Compared with the prior art, the present invention has the following outstanding advantages: (1) Green and safe with no hidden dangers, no open flame high-temperature smelting, no chloride ion medium, and no hydrogen sulfide highly toxic gas generated throughout the process, completely solving the environmental pollution and operational safety problems of traditional processes, and achieving full environmental compliance; (2) Extremely low investment cost, using modular small equipment to replace large smelting equipment, reducing the initial investment of the production line by more than 65%, and suitable for small and medium-sized enterprises to start production; (3) Excellent process performance, high bismuth leaching rate and impurity removal rate, and the product stably reaches the 4N high purity level, with controllable quality; (4) Significantly reduced energy consumption, low temperature and normal pressure operation throughout the process, no need for high temperature smelting, and a significant reduction in production energy consumption; (5) Closed-loop production, zero wastewater discharge, high water resource utilization rate, low operation and maintenance cost, suitable for long-term stable industrial mass production. Attached Figure Description Figure 1 This is a complete process flow diagram of the present invention for preparing 4N refined bismuth from bismuth-containing waste.

Claims

1. A green, chlorine-free, short-process technology for preparing 4N refined bismuth from bismuth-containing waste, characterized in that... Includes the following steps: (1) Raw material pretreatment: crush and screen the bismuth-containing waste to 80~100 mesh to obtain uniform powder raw material; (2) Atmospheric pressure chlorine-free leaching: a sulfuric acid-citric acid chlorine-free composite leaching system is adopted, the liquid-solid ratio is controlled at 3:1, the reaction temperature is room temperature to 60℃, and the stirring leaching is carried out for 2.5 to 3 hours; (3) Solid-liquid separation: The leaching residue and bismuth-rich filtrate are separated by pressure filtration; (4) Non-toxic selective impurity removal: Under normal temperature conditions, add an organic sulfurizing agent to the bismuth-rich filtrate, adjust the pH of the system to 1.5~2.5, selectively precipitate and remove copper, lead and silver impurities, and filter to obtain purified bismuth-rich filtrate; (5) Low-temperature electrowinning: The purified bismuth-rich solution is fed into the electrowinning device and electrowinning is carried out at a low temperature of 40~50℃ to obtain crude bismuth; (6) Vacuum refining: Crude bismuth is refined by low-temperature vacuum distillation to obtain refined bismuth with a purity ≥99.99%; (7) Wastewater recycling: Wastewater from the entire production line is collected, treated, and recycled in a closed loop.

2. The green, chlorine-free, short-process technology for preparing 4N refined bismuth from bismuth-containing waste according to claim 1, characterized in that: In step (4), the organic sulfurizing agent is an aqueous solution of mercaptoacetate, and the amount added is 1% to 3% of the volume of the bismuth-rich filtrate.

3. The green, chlorine-free, short-process technology for preparing 4N refined bismuth from bismuth-containing waste according to claim 1, characterized in that: The bismuth leaching rate of this process is ≥92%, and the comprehensive removal rate of copper, lead, and silver impurities is ≥95%.

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