A method for extracting selenium and tellurium by sulphuric acid roasting of copper anode mud

Abstract

The present invention provides a method for sulphating and roasting copper anode mud and extracting selenium and tellurium. After the copper anode mud is mixed with concentrated sulfuric acid and roasted, the selenium extraction method adopts a three-stage series tower to absorb the roasting gas, introduces nitrogen and then roasts and controls the temperature by microwave, roasts and evaporates selenium by sulfuric acid and hydrogen peroxide, and desulfurizes the waste gas by an alkali spray tower; the tellurium extraction method adopts a cyclone electrowinning technology, electrolytic slurry is electrolyzed in a secondary cycle, and the electrolytic slurry is fed in a bottom-in-top-out liquid feeding mode. The three-stage series absorption tower and microwave temperature control method of the present invention increase the selenium leaching rate, the leaching rate is 98.0%, the tellurium is recovered by the cyclone electrowinning technology, the tellurium purity is 99.99%, the waste gas is removed by an alkali spray method, the dust removal efficiency is 99.5%, and the desulfurization efficiency is 95.0%. The process of the present invention is easy to operate, the equipment is highly versatile, and the environmental pollution is small.

Description

Technical Field

[0001] The invention relates to the technical field of ore dressing, in particular to a method for extracting selenium and tellurium by sulphating and roasting copper anode mud. Background Art

[0002] Selenium is widely used in healthcare, agriculture, glass industry, and catalyst industry. Tellurium is one of the semiconductor materials for high-tech industries and is known as the "vitamin of modern industry, national defense, and cutting-edge technology." Due to its low abundance in the earth's crust, tellurium, selenium, rhenium, etc. are generally called "rare elements" or "dispersed metals." With the increasing demand for new materials in various fields, selenium and tellurium, as a dispersed metal, have become supporting materials for the required new materials. At present, the main raw material for recycling selenium and tellurium is copper anode mud, which is rich in various metals and has a very high comprehensive recycling value.

[0003] The method of sulphation roasting-reduction is one of the methods for recovering selenium and tellurium. Roasting temperature, time, acid addition, leaching temperature, time, liquid-solid ratio, etc. affect the leaching efficiency of selenium and tellurium. In the thermodynamic reaction of sulphation roasting-reduction, at low temperature, selenide reacts with sulfuric acid to generate selenium dioxide and intermediate product selenium. At high temperature, there is no intermediate product selenium. Due to the complex composition of copper anode mud, the control of roasting temperature is very critical. Selenium reacts with sulfur dioxide to generate selenosulfate and enter the solution. In strong acid, selenosulfate decomposes to obtain elemental selenium. Sodium sulfite and sulfur dioxide in strong acid solution can completely reduce selenous acid to elemental selenium. Therefore, the type and concentration of strong acid and its ratio with materials affect the extraction efficiency. The chemical method for preparing tellurium is prone to produce a large amount of wastewater, causing environmental pollution. The purity of tellurium is not high and needs further purification. The traditional electrowinning method has a low current density, resulting in low tellurium production efficiency, a long electrolysis cycle, high requirements for the impurity content in the electrolyte, and repeated impurity removal, resulting in a large amount of reagent consumption. Patent CN107447105 B is a method for separating and enriching tellurium by controlling the potential of copper anode mud. The potential control method is used to achieve a replacement rate of tellurium of more than 99.0%. Patent CN111575483B is a method for separating selenium, tellurium, arsenic, copper, lead, and silver from copper anode mud and enriching gold. The recovery rate of gold and silver is clearly increased, but the recovery rate of selenium is not clear. "Thermodynamic and process research on the reduction of selenium dioxide by sodium sulfite" points out that there are optimal conditions for the reduction of selenium dioxide by sodium sulfite, and the kinetic data of the sulfuric acid roasting of low-arsenic antimony and bismuth copper anode mud fits the Avrami Erofeev equation model well. However, there is a lack of research on the extraction of selenium and tellurium under the complex composition of industrial raw copper anode mud, and the existing sulfuric acid roasting-reduction technology has the problems of low selenium and tellurium leaching rate and low purity. Summary of the invention

[0004] In view of this, the present invention proposes a method for extracting selenium and tellurium by sulphate roasting of copper anode mud.

[0005] The technical solution of the present invention is achieved in this way:

[0006] A method for extracting selenium and tellurium by sulphating and roasting copper anode mud comprises the following steps:

[0007] Step 1, mixing copper anode mud with concentrated sulfuric acid solution, stirring, and roasting to obtain roasting gas;

[0008] Preferably, the mass ratio of copper anode mud to concentrated sulfuric acid solution is 1.0:(0.9-1.1), the roasting time is 3-4 hours, the roasting temperature at the feeding end is 250-500°C, and the roasting temperature at the discharge end is 500-650°C;

[0009] The main reaction of deselenization by sulfuric acid roasting:

[0010] SeSO3+H2SO4=SeO2+2SO2+H2O

[0011] Step 2, the roasting gas is absorbed by a three-stage series tower, and the microwave roasting temperature is controlled. Nitrogen is introduced into the three-stage series tower at 10-25° C. and 8-15 mL / min for 30-60 minutes to obtain a mixed gas. The mixed gas is introduced into a first-stage absorption tower at a temperature of 350-450° C. for 15-25 minutes, and the temperature of the second-stage absorption tower is 450-550° C. for 25-30 minutes; the temperature of the third-stage absorption tower is 550-650° C. for 30-50 minutes; and distilled water is sequentially passed through the first-stage absorption tower, the second-stage absorption tower and the third-stage absorption tower for washing with distilled water to obtain a selenious acid solution.

[0012] Step 3, the selenious acid solution is reduced to selenium, the selenium is dried and dissolved to obtain crude selenium, the crude selenium is added to the dissolving solution and SO2 gas is introduced, and then dried, melted, and distilled to obtain a refined selenium product, the waste gas is removed by alkali liquid spraying, and the remaining material is put into roasted sand;

[0013] Preferably, the drying temperature is 15-25°C, the concentration of the sulfuric acid solution is 1.5-2 mol / L, the concentration of the hydrogen peroxide solution is 0.6-1 mol / L, and the mass ratio of the sulfuric acid solution to the hydrogen peroxide solution is 1:(1-1.5); the solid-liquid ratio of the crude selenium to the sulfuric acid solution and the hydrogen peroxide solution is (15-20):(8-10), the dissolved solution is dried after passing SO2 gas at 160-200 mL / min, and the drying temperature is 30-50°C;

[0014] The main reaction of selenium reduction is:

[0015] SeO2+H2O==H2SeO3

[0016] H2SeO3+2SO2+H2O==Se+2H2SO4

[0017] H2SeO3+2SO2+H2O==2H2SO4+Se

[0018] Preferably, the waste gas is drained by a water ring vacuum pump, and desulfurized by an alkali solution spray tower. A Ca(OH)2 solution with a mass concentration of 0.1% to 0.15% is added to the spray to obtain a spray alkali solution, and the spray alkali solution maintains a pH of 8.5 to 12.

[0019] Step 4: ball-mill the material from step 3, dissolve it with strong alkali to obtain a tellurium-containing alkali solution, and then the tellurium-containing alkali solution enters the cyclone electrolysis system at a rate of 0.8L / min to 1.2L / min at 60℃ to 70℃ and 70 to 75A / m 2 The cathode current is swirl electrolyzed for 1 to 1.5 hours to obtain electrolytic slurry. The electrolytic slurry enters the slurry tank for the second time. The electrolytic slurry is fed from the bottom to the top at 75°C to 80°C and 100 to 150A / m 2 The cathode product is boiled and washed with 0.1-0.13 mol / L oxalic acid solution for 10-12 hours, rinsed with deionized water, dried, and ultrasonically washed to obtain a tellurium product.

[0020] Preferably, the material is 100% passed through a 200 mesh sieve after ball milling, the strong base is 120-130 g / L NaOH solution, the mass ratio of the pulverized material to the NaOH solution is (4-5):1, the leaching temperature is 70°C-90°C, and the leaching time is 4-6 hours;

[0021] Preferably, the ultrasonic washing has a frequency of 50k to 60kHz and a washing time of 5 to 10 minutes.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The invention adopts a method of sulphating and roasting copper anode mud to extract selenium and tellurium, a three-stage series absorption tower and a microwave temperature control nitrogen introduction method to increase the selenium leaching rate, the leaching rate is 98.0%, a cyclone electrowinning technology is adopted to recover tellurium, the purity of the recovered tellurium is 99.99%, and the waste gas is removed by an alkali liquid spraying method, the dust removal efficiency is 99.5%, and the desulfurization efficiency is 95.0%. The process of the invention is easy to operate, the equipment is highly versatile, and the environmental pollution is small. DETAILED DESCRIPTION

[0024] In order to better understand the technical content of the present invention, specific embodiments are provided below to further illustrate the present invention.

[0025] Unless otherwise specified, the experimental methods used in the examples and comparative examples of the present invention are all conventional methods, and the materials, reagents, etc. used are all commercially available unless otherwise specified.

[0026] Example:

[0027] The main components of copper anode mud are copper anode mud, tellurium-alkali slag, tellurium sponge, tellurium-bismuth alloy scraps, tellurium dioxide, tellurium-copper slag, tellurium-copper fly ash, tellurium-antimony slag, selenium-tellurium sludge and alkali slag. The specific contents of 16 elements such as Pb and Bi are shown in Table 1.

[0028] Table 1 Element analysis of main components of copper anode mud

[0029]

[0030] 1600 kg of copper anode mud is mixed with concentrated sulfuric acid solution with a weight of 1.0 to 1.1 times the weight of the material, and the mass fraction of the concentrated sulfuric acid solution is 98%. It is stirred into slurry in a mixing tank, and the slurry is continuously fed into the sulphation roasting furnace using a feeding device, and roasted at a temperature of about 600°C for 3.5 hours. At this temperature, the selenium compounds or components in the elemental state in the raw materials react with sulfuric acid to produce SeO2, which volatilizes into the flue gas. The entire kiln body can be divided into two zones, from the kiln head (near the feeding end) to the middle of the kiln is the sulphation roasting zone, with a temperature of 450±30°C; from the middle to the kiln tail (near the discharge end) is the selenium dioxide volatilization zone, with a temperature of 600±30°C.

[0031] The flue gas adopts three-stage absorption towers in series, and microwave roasting heating and temperature control are adopted. The flue gas containing SeO2 and SO2 enters the absorption tower through the outlet pipe at the feed end. SeO2 in the flue gas generates selenious acid when it meets water at 95°C. At 25°C, nitrogen is introduced into the three-stage series tower at 15mL / min for 50 minutes to obtain a mixed gas, which is introduced into the first-stage absorption tower. The temperature of the first-stage absorption tower is 400℃±50℃, which is maintained for 8 minutes, and the temperature of the second-stage absorption tower is 500℃±50℃, which is maintained for 8 minutes; the temperature of the third-stage absorption tower is 600℃±50℃, which is maintained for 5 minutes; distilled water is sequentially passed through the first-stage absorption tower, the second-stage absorption tower and the third-stage absorption tower for distilled water washing.

[0032] In the absorption tower, the generated selenious acid is reduced to monomer selenium by sulfur dioxide in the flue gas, and after washing with water and drying naturally at 25°C, crude selenium is obtained. 2mol / L sulfuric acid and 1mol / L hydrogen peroxide are added to the crude selenium to dissolve it. The solid-liquid ratio of crude selenium to sulfuric acid solution and hydrogen peroxide solution is 1.5:1. SO2 is introduced into the solution at 200mL / min, and the crude selenium is reduced to obtain refined selenium. Refined selenium is dried at 40°C, melted, and distilled to obtain selenium products. The generated flue gas and water vapor are pumped away by a water ring vacuum pump and enter the alkali solution spray system.

[0033] The sulphate roasting furnace produces 2000Nm 3 / h, the main pollutants are smoke and SO2. After being absorbed and reduced in the absorption tower, the flue gas is desulfurized in an alkali spray tower. A Ca(OH)2 solution with a mass concentration of 0.15% is added to the spray to obtain a spray alkali solution. The spray alkali solution maintains pH = 9 ± 1 and is finally discharged through the 2#H50m chimney.

[0034] Table 2 Sulfuric acid roasting flue gas generation (unit: generation / emission kg / h; generation / emission concentration mg / m 3 )

[0035]

[0036] The material was ball milled and pulverized, and then dissolved in 120g / L NaOH solution to obtain tellurium-containing solution. The mass ratio of the pulverized material to the NaOH solution was 5:1, the leaching temperature was 80℃, and the leaching time was 5h. After purification, the tellurium-containing solution entered the cyclone electrolysis system at 1L / min, and the temperature was controlled at 70±5℃ and 75A / m 2 The electrolytic slurry was electrolyzed for 1 hour under the cathode current of 150A / m. The electrolytic slurry was fed into the slurry tank for the second time. The electrolytic slurry was fed from the bottom to the top. 2 The cathode product was boiled and washed with 0.1 mol / L oxalic acid solution for 10 h, rinsed with ionized water, dried, and ultrasonically washed at an ultrasonic frequency of kHz for 10 min to obtain a tellurium product.

[0037] Comparative Example

[0038] The main difference between the comparative example and the embodiment is that the extraction method of selenium adopts a primary absorption tower roasting to replace the three-stage series tower roasting; the extraction method of tellurium adopts heating borax to 500°C, 500°C to replace 600°C, and the vacuum distillation step is eliminated. The raw materials and components of the copper anode mud of the comparative example are the same as those of the embodiment, as shown in Table 1.

[0039] 1600 kg of copper anode mud is mixed with concentrated sulfuric acid solution with a weight of 1.0 to 1.1 times the weight of the material, and the mass fraction of the concentrated sulfuric acid solution is 98%. It is stirred into slurry in a mixing tank, and the slurry is continuously fed into the sulphation roasting furnace using a feeding device, and roasted at a temperature of about 600°C for 3.5 hours. At this temperature, the selenium compounds or components in the elemental state in the raw materials react with sulfuric acid to produce SeO2, which volatilizes into the flue gas. The entire kiln body can be divided into two zones, from the kiln head (near the feeding end) to the middle of the kiln is the sulphation roasting zone, with a temperature of 450±30°C; from the middle to the kiln tail (near the discharge end) is the selenium dioxide volatilization zone, with a temperature of 600±30°C.

[0040] Flue gas containing SeO2 and SO2 enters the primary absorption tower through the outlet pipe at the feed end. SeO2 in the flue gas generates selenious acid when it meets water at 95℃. Heat and control the temperature to 500℃±50℃, maintain for 21 minutes, and then wash with distilled water.

[0041] In the absorption tower, the generated selenious acid is reduced to monomer selenium by sulfur dioxide in the flue gas, and after washing with water and drying naturally at 25°C, crude selenium is obtained. 2mol / L sulfuric acid and 1mol / L hydrogen peroxide are added to the crude selenium to dissolve it. The solid-liquid ratio of crude selenium to sulfuric acid solution and hydrogen peroxide solution is 1.5:1. SO2 is introduced into the solution at 200mL / min, and the crude selenium is reduced to obtain refined selenium. Refined selenium is dried at 40°C, melted, and distilled to obtain selenium products. The leaching rate of selenium is 92%, and the generated flue gas and water vapor are pumped away by a water ring vacuum pump and enter the alkali solution spray system.

[0042] The sulphate roasting furnace produces 2000Nm 3 / h, the main pollutants are smoke and SO2. After being absorbed and reduced in the absorption tower, the flue gas is desulfurized in an alkali spray tower. A Ca(OH)2 solution with a mass concentration of 0.15% is added to the spray to obtain a spray alkali solution. The spray alkali solution maintains pH = 9 ± 1 and is finally discharged through the 2#H50m chimney.

[0043] (1) Leaching and washing: Before leaching, the raw materials are crushed by ball milling and wet grinding to a particle size of 200 mesh. The wet grinding slurry is sent to a mechanical stirring tank, and the liquid-solid ratio is controlled to be 5:1. Then, it is directly heated to 90°C with steam for leaching. 20g / L NaOH is used in the leaching process, and the leaching time is 5h. After leaching, it is filtered and countercurrent washed. After washing and drying, the leached residue is sent to a bismuth reverberatory furnace for reduction smelting, and the leached liquid is sent for purification and neutralization.

[0044] (2) Purification and neutralization: The leachate is purified by filter pressing, and the qualified sodium tellurite solution is pumped into the neutralization tank, and the purified slag is sent to the bismuth smelting system. The neutralization process mainly uses sulfuric acid to neutralize sodium tellurite so that tellurium is precipitated from the solution in the form of tellurium dioxide. The obtained tellurium dioxide is sent to the tellurium electrolysis workshop, and the filtered solution is sent to the water treatment process. The purified solution is returned to the leaching process.

[0045] (3) Electrolytic refining of tellurium dioxide: First, make a liquid, heat tellurium dioxide and water at a ratio of 4:1 at 80°C to dissolve, then add sodium hydroxide to make tellurium in the form of sodium tellurite, and adjust the composition of the solution to contain 120g / L NaOH and 200g / L tellurium; then electrolyze, and use a titanium plate as an anode and a stainless steel plate as a cathode in the electrolytic deposition process. Electrolysis is carried out at room temperature, and the electrolysis cycle is 12 days. The tellurium obtained in the electrolytic deposition process is melted in a graphite crucible furnace, and borax is added to heat it to 500°C to melt, and the grade of the output tellurium ingot is 96%.

[0046] Comparative Example: After the selenium extraction method adopts a primary absorption tower roasting instead of a three-stage series tower roasting, the selenium leaching rate is reduced from 98% to 92%; the tellurium extraction method adopts electrolytic refining to melt borax, and the grade of the output tellurium ingot is reduced from 99.99% to 96%.

[0047] The results show:

[0048] The present invention provides a method for sulphating and roasting copper anode mud and extracting selenium and tellurium. After the copper anode mud is mixed with concentrated sulfuric acid and roasted, a three-stage series tower is used to absorb the roasting gas, nitrogen is introduced and microwave roasting is used to control the temperature, sulfuric acid and hydrogen peroxide are roasted to evaporate selenium, and an alkali liquid spray tower is used to desulfurize the waste gas; the cyclone electrowinning technology is used, and the electrolytic slurry is electrolyzed for secondary circulation to obtain the finished tellurium. The method of the present invention increases the leaching rate of selenium, the leaching rate is 98.0%, and 99.99% high-purity tellurium is produced. The alkali liquid spray method is used to remove the waste gas, the dust removal efficiency is 99.5%, and the desulfurization efficiency is 95.0%. Therefore, the present invention improves the leaching rate of selenium and the grade of tellurium, and effectively controls the dust and sulfur pollution in the waste gas, and realizes the efficient utilization of copper anode mud.

[0049] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for extracting selenium and tellurium by sulphate roasting of copper anode mud, characterized in that The following steps are involved: Step 1, mixing copper anode mud with concentrated sulfuric acid solution, stirring, and roasting to obtain roasting gas; Step 2, the roasting gas is absorbed by a three-stage series tower, and the microwave roasting temperature is controlled. Nitrogen is introduced into the three-stage series tower at 10-25° C. at 8-15 mL / min for 30-60 min to obtain a mixed gas. The mixed gas is introduced into a primary absorption tower at a temperature of 350-450° C. for 15-25 min, and the temperature of the secondary absorption tower is 450-550° C. for 25-30 min; the temperature of the tertiary absorption tower is 550-650° C. for 30-50 min; distilled water is sequentially passed through the primary absorption tower, the secondary absorption tower and the tertiary absorption tower for washing to obtain a selenious acid solution; Step 3, the selenious acid solution is reduced to selenium, which is dried and dissolved to obtain crude selenium, the crude selenium is added with sulfuric acid solution and hydrogen peroxide solution, SO2 gas is introduced, dried, melted and distilled to obtain refined selenium product, the waste gas is removed by alkali liquid spraying method, and the remaining material is put into roasted sand; Step 4: ball-mill the material from step 3, dissolve it with strong alkali to obtain a tellurium-containing alkali solution, purify the tellurium-containing alkali solution and feed it into a cyclone electrolysis system at a rate of 0.8L / min~1.2L / min at 60℃~70℃ and 70~75A / m 2 The cathode current is swirl electrolyzed for 1~1.5h to obtain electrolytic slurry. The electrolytic slurry enters the slurry tank for the second time. The electrolytic slurry is fed from the bottom to the top. The temperature is 75℃~80℃ and 100~150A / m 2 The cathode product is boiled and washed with 0.1-0.13 mol / L oxalic acid solution for 10-12 hours, rinsed with deionized water, dried, and ultrasonically washed to obtain a tellurium product. Step 3, the drying temperature is 15-25°C, the concentration of the sulfuric acid solution is 1.5-2 mol / L, the concentration of the hydrogen peroxide solution is 0.6-1 mol / L, and the mass ratio of the sulfuric acid solution to the hydrogen peroxide solution is 1:(1-1.5); the solid-liquid ratio of the crude selenium to the sulfuric acid solution and the hydrogen peroxide solution is (1.5-2.0):(0.8-1.0), the dissolved solution is dried after passing SO2 gas at 160-200 mL / min, and the drying temperature is 30-50°C; Step 3, the exhaust gas is drained by a water ring vacuum pump, and desulfurized by an alkali solution spray tower, and a Ca(OH)2 solution with a mass concentration of 0.1% to 0.15% is added to the spray to obtain a spray alkali solution, and the spray alkali solution maintains a pH of 8.5 to 12; Step 4, after ball milling, 100% of the material passes through a 200-mesh sieve to obtain a crushed material, the strong base is 120-130 g / L NaOH solution, the mass ratio of the crushed material to the NaOH solution is (4-5):1, the leaching temperature is 70°C-90°C, and the leaching time is 4-6 hours.

2. The method for extracting selenium and tellurium by sulphate roasting of copper anode mud according to claim 1, characterized in that: Step 1, the mass ratio of the copper anode mud to the concentrated sulfuric acid solution is 1.0: (0.9-1.1), the mass fraction of the concentrated sulfuric acid solution is 90%-98%, the roasting temperature at the feeding end is 250-500°C, and the roasting temperature at the discharge end is 500-650°C.

3. The method for extracting selenium and tellurium by sulphate roasting of copper anode mud according to claim 1, characterized in that: Step 4, the ultrasonic washing has a frequency of 50-60 kHz and a washing time of 5-10 min.

Images