A method for preparing tellurium dioxide from lead anode mud

Abstract

The present invention discloses a method for preparing tellurium dioxide from lead anode mud, which relates to the field of comprehensive recovery and utilization of rare earth metals. The method utilizes the vaporization, volatilization, migration, condensation, and oxidation transformation characteristics of each component in lead anode mud. Based on the advantages of a combined fire-wet process, the method involves a first constant-temperature vacuum distillation to separate tellurium from tellurium-containing dust and valuable metal elements such as gold, silver, and copper. Arsenic, antimony, and tellurium are then completely oxidized to arsenic trioxide, antimony trioxide, and tellurium dioxide by adding a composite oxidant (lead dioxide and hydrogen peroxide). A second variable-temperature vacuum distillation is then performed to control the temperature gradient between two sections to remove excess water, arsenic trioxide, and antimony trioxide from the tellurium-containing dust after oxidation and regulation. The residue contains tellurium dioxide powder with a tellurium dioxide content greater than 15%, and the direct tellurium yield for the entire process is greater than 95%. The method facilitates the efficient preparation of tellurium dioxide from lead anode mud and is suitable for the clean, low-carbon recovery of tellurium in the comprehensive recovery and utilization of rare earth metals.

Description

Technical Field

[0001] The present invention relates to the field of comprehensive recycling of rare metals, and in particular to a method for preparing tellurium dioxide from lead anode mud. Background Art

[0002] Tellurium is a critical rare earth metal that safeguards national security, fuels national economic development, and promotes the advancement of high-tech technologies. Its importance in emerging fields such as defense, aerospace, atomic energy, biomedicine, electronic information, and new energy continues to grow. It is hailed as "a vitamin for modern industry, national defense, and cutting-edge technology, a bridge for creating miracles on earth," and "a supporting material for contemporary high-tech advanced materials." The efficient utilization of tellurium resources and the innovative development of new tellurium products are of fundamental and pioneering strategic significance and are highly valued by the nation and governments at all levels. Resources, energy, and the environment are the primary challenges facing modern nonferrous metallurgy. The level of tellurium smelting is a key indicator of the development of a country's nonferrous metal industry, and clean, efficient, and streamlined extraction processes are constantly pursued. Tellurium in the Earth's crust primarily occurs as an associated mineral in lead, copper, nickel, gold, and silver. There are virtually no single, primary minerals from which tellurium can be directly extracted. Therefore, the primary sources of tellurium are copper anode slime, lead anode slime, and nickel byproducts. Potential sources include tellurium bismuth and tellurium gold ores.

[0003] Currently, over 90% of tellurium comes from anode mud produced during the lead-copper electrolytic refining process, with the remainder coming from flue dust generated during the smelting of bismuth-nickel-copper ore, as well as tellurium-bismuth and tellurium-gold ores. In 2023, lead, copper, and other smelters nationwide produced 430 tons of refined tellurium, accounting for approximately 67.19% of global tellurium production. Lead-copper anode mud is increasingly becoming the primary raw material for tellurium extraction. The traditional process for extracting tellurium from lead-copper anode mud involves high-temperature smelting, slagging, leaching, purification, roasting, liquid preparation, and electrowinning. This process requires the addition of strong acids or bases such as sodium hydroxide and hydrochloric acid, and consumes large quantities of chemical reagents such as sodium sulfite and sodium sulfide, as well as energy resources such as heavy oil and natural gas. This process generates large amounts of wastewater, waste residue, and exhaust gas, causing serious environmental pollution. Furthermore, the process is plagued by common challenges such as lengthy processes, complex operations, low metal recovery rates, and long recycling cycles. These bottlenecks hinder the sustainable development of tellurium extraction. A more prominent problem is that tellurium is dispersed in smelting slag, oxidation slag, refining slag, soot, and other metals, resulting in a direct tellurium recovery rate of less than 40%. Therefore, developing new technologies for green and efficient tellurium extraction, cleanly utilizing tellurium resources in lead anode mud, streamlining separation process design, and improving resource utilization are urgent needs for the integration of lead metallurgy and tellurium extraction, and are also the technological pillars for the industry's ecological development. Summary of the Invention

[0004] The present invention addresses the common challenges of existing tellurium recovery processes from lead anode mud, such as long process flows, cumbersome operations, low metal direct recovery rates, and long recovery cycles. By improving the direct recovery rate of tellurium, reducing reagent consumption, and harmlessly separating arsenic and antimony, the present invention proposes a method for preparing tellurium dioxide from lead anode mud. The method utilizes a three-stage process of constant temperature vacuum distillation, oxidation control, and variable temperature vacuum distillation to separate tellurium from the lead anode mud in the form of tellurium dioxide. The specific steps are as follows:

[0005] (1) Fresh lead anode mud is placed in a vacuum furnace for constant temperature vacuum distillation to obtain tellurium-containing dust.

[0006] (2) Adding the tellurium-containing dust obtained in (1) to a composite oxidant for oxidation regulation, wherein the composite oxidant is lead dioxide and hydrogen peroxide.

[0007] (3) The tellurium-containing dust oxidized and regulated in (2) is placed in a vacuum furnace for variable temperature vacuum distillation to obtain tellurium dioxide powder and arsenic antimony oxide.

[0008] Preferably, the constant temperature vacuum distillation conditions in step (1) are: vacuum degree 1-50 Pa, distillation temperature 500-800° C., and distillation time 60-210 min.

[0009] Preferably, in step (2), the mass ratio of tellurium-containing dust, lead dioxide and hydrogen peroxide is (0.1-1):(0.3-1):2.

[0010] Preferably, the concentration of hydrogen peroxide in step (2) is 30%.

[0011] Preferably, the oxidation regulation time in step (2) is 60 to 240 minutes.

[0012] Preferably, the conditions for variable temperature vacuum distillation in step (3) are: vacuum degree 1-50 Pa, first heating to 100-200° C., keeping warm for 20-60 min, then heating to 300-660° C., keeping warm for 30-180 min.

[0013] Preferably, a vertical vacuum furnace is used for vacuum distillation in step (1) and step (3). BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0015] The technical solutions in the embodiments of the present invention are described in further detail below. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts are within the scope of protection of the present invention.

[0016] Example 1

[0017] A method for efficiently preparing tellurium dioxide from lead anode mud (see Figure 1 ), the specific steps are as follows:

[0018] The lead anode slime used in this example is produced by the lead refining system of a lead smelter, and its composition is shown in Table 1.

[0019] Table 1 Lead anode mud composition

[0020] element As Sb Pb Bi Te Cu Ag Au Content (wt / %) 13.05 36.29 15.74 10.24 0.13 2.01 3.02 0.0012

[0021] (1) 10 kg of fresh lead anode mud was placed in a vertical vacuum furnace for constant temperature vacuum distillation. The vacuum degree in the furnace was controlled at 3 Pa and the temperature was 800 °C. After distillation for 60 min, 4.35 kg of tellurium-containing dust was obtained from the volatiles.

[0022] (2) 0.435 kg of lead dioxide and 6.53 kg of 30% hydrogen peroxide were added to the tellurium-containing dust obtained in step (1) and placed in a glass reactor for oxidation control. The reaction time was 240 min.

[0023] (3) The tellurium-containing dust oxidized and regulated in step (2) was placed in a vertical vacuum furnace for variable temperature vacuum distillation. The vacuum degree in the furnace was controlled at 25 Pa. The temperature was first raised to 110° C. and kept at this temperature for 40 minutes to distill away excess hydrogen peroxide and moisture. The temperature was then raised to 660° C. and kept at this temperature for 180 minutes to obtain 88 g of tellurium dioxide powder from the residue.

[0024] The tellurium dioxide powder was tested and the tellurium dioxide content was 17.68% and the tellurium direct yield was 96.32%.

[0025] Example 2

[0026] A method for efficiently preparing tellurium dioxide from lead anode mud (see Figure 1 ), the specific steps are as follows:

[0027] The composition of the lead anode slime used in Example 2 of the present invention is the same as that in Example 1, and the composition is shown in Table 1.

[0028] (1) Take 10 kg of fresh lead anode mud and put it into a vertical vacuum furnace for constant temperature vacuum distillation. The vacuum degree in the furnace is controlled at 50 Pa and the temperature is 700 °C. After distillation for 180 minutes, 3.85 kg of tellurium-containing dust is obtained from the volatile matter.

[0029] (2) The tellurium-containing dust obtained in step (1) was placed in a glass reactor together with 0.77 kg of lead dioxide and 4.24 kg of 30% hydrogen peroxide for oxidation control. The reaction time was 60 min.

[0030] (3) The tellurium-containing dust oxidized and regulated in step (2) was placed in a vertical vacuum furnace for variable temperature vacuum distillation. The vacuum degree in the furnace was controlled to 1 Pa. The temperature was first raised to 180° C. and kept at this temperature for 20 minutes to distill away excess hydrogen peroxide and moisture. The temperature was then raised to 300° C. and kept at this temperature for 150 minutes to obtain 100 g of tellurium dioxide powder from the residue.

[0031] The tellurium dioxide powder was tested and the tellurium dioxide content was 15.99% and the tellurium direct yield was 98.01%.

[0032] Example 3

[0033] A method for efficiently preparing tellurium dioxide from lead anode mud (see Figure 1 ), the specific steps are as follows:

[0034] The composition of the lead anode slime used in Example 3 of the present invention is the same as that in Example 1, and the composition is shown in Table 1.

[0035] (1) 10 kg of fresh lead anode mud was placed in a vertical vacuum furnace for constant temperature vacuum distillation. The vacuum degree in the furnace was controlled at 25 Pa and the temperature was 500 °C. After distillation for 210 min, 4.69 kg of tellurium-containing dust was obtained from the volatile matter.

[0036] (2) The tellurium-containing dust obtained in step (1) was placed in a glass reactor together with 1.407 kg of lead dioxide and 9.38 kg of 30% hydrogen peroxide for oxidation control. The reaction time was 120 min.

[0037] (3) The tellurium-containing dust oxidized and regulated in step (2) was placed in a vertical vacuum furnace for variable temperature vacuum distillation. The vacuum degree in the furnace was controlled at 50 Pa. The temperature was first raised to 200°C and kept at this temperature for 60 minutes to distill away excess hydrogen peroxide and moisture. The temperature was then raised to 550°C and kept at this temperature for 30 minutes to obtain 94 g of tellurium dioxide powder from the residue.

[0038] The tellurium dioxide powder was tested and the tellurium dioxide content was 16.55% and the tellurium direct yield was 95.48%.

[0039] Comparative Example 1

[0040] For comparison, the only difference between the local ratio and Example 3 is that step (1) is not performed, and a composite oxidant consisting of lead dioxide and hydrogen peroxide is directly added to the fresh lead anode mud. The specific steps are as follows:

[0041] (1) 10 kg of fresh lead anode mud, 1.407 kg of lead dioxide, and 9.38 kg of 30% hydrogen peroxide were placed in a glass reactor for oxidation control. The reaction time was 120 min.

[0042] (2) The lead anode mud oxidized and regulated in step (1) was placed in a vertical vacuum furnace for variable temperature vacuum distillation. The vacuum degree in the furnace was controlled at 50 Pa. The temperature was first raised to 200° C. and kept at this temperature for 60 minutes to distill away excess hydrogen peroxide and moisture. The temperature was then raised to 550° C. and kept at this temperature for 30 minutes to obtain 588 g of tellurium dioxide powder from the residue.

[0043] Testing of the tellurium dioxide powder revealed a tellurium dioxide content of 2.11% and a tellurium direct yield of 76.21%. This comparative example performed worse than Example 3 because, without undergoing the first constant-temperature vacuum distillation stage, large amounts of gold, silver, copper, lead, and bismuth elements in the lead anode mud remained in the residual tellurium dioxide powder and could not be separated and removed, resulting in a significant drop in the tellurium dioxide content in the residue to 2.11%. This significantly impacted the quality of the tellurium dioxide product and hindered the subsequent utilization of the tellurium dioxide powder. Furthermore, metallic compounds formed by elements such as silver and copper reacted with the lead dioxide and hydrogen peroxide in the composite oxidant, consuming some of the composite oxidant. Consequently, the added composite oxidant was insufficient to completely oxidize tellurium to tellurium dioxide, resulting in tellurium volatilization losses during the variable-temperature vacuum distillation process. This directly led to a significant drop in the tellurium direct yield from 95.48% in Example 3 to 76.21%.

[0044] Comparative Example 2

[0045] For comparison, the only difference between this comparative example and Example 3 is that only hydrogen peroxide is added in step (2), and the remaining steps are the same as those in Example 3. The specific steps are as follows:

[0046] (1) 10 kg of fresh lead anode mud was placed in a vertical vacuum furnace for constant temperature vacuum distillation. The vacuum degree in the furnace was controlled at 25 Pa and the temperature was 500 °C. After distillation for 210 min, 4.69 kg of tellurium-containing dust was obtained from the volatile matter.

[0047] (2) The tellurium-containing dust obtained in step (1) was placed in a glass reactor together with 9.38 kg of 30% hydrogen peroxide for oxidation control. The reaction time was 120 min.

[0048] (3) The tellurium-containing dust oxidized and regulated in step (2) was placed in a vertical vacuum furnace for variable temperature vacuum distillation. The vacuum degree in the furnace was controlled at 50 Pa. The temperature was first raised to 200° C. and kept at this temperature for 60 minutes to distill away excess hydrogen peroxide and moisture. The temperature was then raised to 550° C. and kept at this temperature for 30 minutes to obtain 178 g of tellurium dioxide powder from the residue.

[0049] The tellurium dioxide powder was tested, and the tellurium dioxide content was 7.63%, and the tellurium direct yield was 83.47%. The effect of this comparative example was not as good as that of Example 3 because only hydrogen peroxide was added in step (2), which resulted in the hydrogen peroxide added within the same oxidation time not being able to completely oxidize tellurium, arsenic, and antimony into tellurium dioxide, arsenic trioxide, and antimony trioxide. At the same time, lead dioxide also played a role in continuing to oxidize tellurium during the variable temperature vacuum distillation process. The absence of lead dioxide prevented the composite oxidant from playing its due role during the variable temperature vacuum distillation process. When tellurium cannot be completely converted into tellurium dioxide, it is very easy to evaporate from the tellurium dioxide powder during the variable temperature vacuum distillation process, resulting in a rapid decrease in the tellurium dioxide content in the tellurium dioxide powder and a linear drop in the tellurium direct yield.

[0050] Comparative Example 3

[0051] For comparison, the only difference between this comparative example and Example 3 is that only constant temperature distillation is performed in step (3), and the remaining steps are the same as those in Example 3. The specific steps are as follows:

[0052] (1) 10 kg of fresh lead anode mud was placed in a vertical vacuum furnace for constant temperature vacuum distillation. The vacuum degree in the furnace was controlled at 25 Pa and the temperature was 500 °C. After distillation for 210 min, 4.69 kg of tellurium-containing dust was obtained from the volatile matter.

[0053] (2) The tellurium-containing dust obtained in step (1) was placed in a glass reactor together with 1.407 kg of lead dioxide and 9.38 kg of 30% hydrogen peroxide for oxidation control. The reaction time was 120 min.

[0054] (3) The tellurium-containing dust oxidized and regulated in step (2) was placed in a vertical vacuum furnace for constant temperature vacuum distillation. The vacuum degree in the furnace was controlled at 50 Pa, the temperature was raised to 550° C., and the holding time was 30 min. 174 g of tellurium dioxide powder was obtained from the residue.

[0055] The tellurium dioxide powder was tested and the tellurium dioxide content was 8.13%, and the tellurium direct yield was 87.36%. The effect of this comparative example was not as good as that of Example 3 because in step (3), only constant temperature vacuum distillation was performed without removing excess hydrogen peroxide and moisture through a variable temperature vacuum distillation process, which directly caused elements such as arsenic and antimony to be oxidized into high-valent arsenic pentoxide and antimony pentoxide. The high-valent arsenic and antimony oxides were difficult to volatilize and remove during the vacuum distillation process, and part of the arsenic pentoxide and antimony pentoxide remained in the tellurium dioxide powder product, resulting in a significant decrease in the tellurium dioxide content and direct yield. The harmful arsenic and antimony element residues would also greatly affect the subsequent further processing and utilization of the tellurium dioxide powder.

[0056] Comparative Example 4

[0057] For comparison, the vacuum distillation in step (1) was replaced by ordinary drying, and the remaining steps were the same as those in Example 3. The specific steps were as follows:

[0058] (1) Take 10 kg of fresh lead anode mud and dry it at 500 °C for 210 min to obtain 7.46 kg of tellurium-containing dust from the volatile matter.

[0059] (2) The tellurium-containing dust obtained in step (1) was placed in a glass reactor together with 1.407 kg of lead dioxide and 9.38 kg of 30% hydrogen peroxide for oxidation control. The reaction time was 120 min.

[0060] (3) The tellurium-containing dust oxidized and regulated in step (2) was placed in a vertical vacuum furnace for variable temperature vacuum distillation. The vacuum degree in the furnace was controlled at 50 Pa. The temperature was first raised to 200°C and kept at this temperature for 60 minutes to distill away excess hydrogen peroxide and moisture. The temperature was then raised to 550°C and kept at this temperature for 30 minutes to obtain 623 g of tellurium dioxide powder from the residue.

[0061] The tellurium dioxide powder was tested and the tellurium dioxide content was 1.85%, and the tellurium direct yield was 70.84%. The effect of this comparative example was not as good as that of Example 3 because after vacuum distillation was replaced by ordinary drying, step (1) could only remove excess water and part of arsenic and antimony oxides in the fresh lead anode mud. Similar to Comparative Example 1, a large amount of elements such as gold, silver, copper, lead, and bismuth in the lead anode mud entered the tellurium-containing dust and tellurium dioxide powder together with tellurium, resulting in a significant drop in the tellurium dioxide content in the residue to 1.85%, which greatly affected the quality of the tellurium dioxide product and was not conducive to the subsequent further utilization of the tellurium dioxide powder. At the same time, metal compounds formed by elements such as silver and copper will also react with lead dioxide and hydrogen peroxide in the composite oxidant, consuming part of the composite oxidant, so that the added composite oxidant is insufficient to completely oxidize tellurium into tellurium dioxide, resulting in tellurium volatilization loss during the variable temperature vacuum distillation process, which directly leads to a significant decrease in the tellurium direct yield from 95.48% in Example 3 to 70.84%.

[0062] The above describes the specific embodiments of the present invention in detail, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in this field without departing from the scope of the present invention.

Claims

1. A method for preparing tellurium dioxide from lead anode mud, characterized in that: The specific steps are as follows: (1) Fresh lead anode mud is placed in a vacuum furnace for constant temperature vacuum distillation to obtain tellurium-containing dust; (2) adding the tellurium-containing dust obtained in (1) to a composite oxidant for oxidation regulation, wherein the composite oxidant is lead dioxide and hydrogen peroxide; (3) placing the tellurium-containing dust oxidized and regulated in (2) into a vacuum furnace for variable temperature vacuum distillation to obtain tellurium dioxide powder and arsenic antimony oxide; In step (2), the mass ratio of tellurium dust, lead dioxide and hydrogen peroxide is (0.1-1):(0.3-1):2; The conditions for variable temperature vacuum distillation in step (3) are: vacuum degree 1~50Pa, first heating to 100~200℃, keeping warm for 20~60min, then heating to 300~660℃, keeping warm for 30~180min.

2. The method for preparing tellurium dioxide from lead anode mud according to claim 1, characterized in that: The constant temperature vacuum distillation conditions in step (1) are: vacuum degree 1~50Pa, distillation temperature 500~800℃, and distillation time 60~210min.

3. The method for preparing tellurium dioxide from lead anode mud according to claim 1, characterized in that: The concentration of hydrogen peroxide in step (2) is 30%.

4. The method for preparing tellurium dioxide from lead anode mud according to claim 1, characterized in that: The oxidation control time in step (2) is 60~240min.

5. The method for preparing tellurium dioxide from lead anode mud according to claim 1, characterized in that: In steps (1) and (3), a vertical vacuum furnace is used for vacuum distillation.

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