Two-stage acid leaching process for zinc, indium and tin

Abstract

The present invention relates to a two-stage acid leaching process for zinc, indium and tin, belonging to the technical field of valuable metal element recovery, and comprising the following steps: using the neutral leaching residue in the process of producing zinc sulfate from secondary zinc oxide as raw material, performing low-acid leaching to obtain a low-acid leaching filtrate; adding iron powder to the low-acid leaching filtrate for reaction, and after the reaction, filtering to obtain a bismuth-removed filtrate; performing extraction on the bismuth-removed filtrate to obtain an extraction solution; adding hydrochloric acid to the extraction solution for back-extraction, the back-extraction solution enters the neutralization process to neutralize the back-extraction solution, adding zinc flakes to displace Sn<supgt;4+< / supgt; in the solution, performing pressure filtration, and the filter cake is acid-leached and pressure-filtered to obtain crude tin; adding zinc flakes to the filtrate for reaction, and pressure-filtering to obtain crude indium. This method is simple and environmentally friendly, and can realize the recovery of indium and tin.

Description

Technical Field

[0001] The present invention belongs to the technical field of recovery of valuable metal elements, and relates to a two-stage acid leaching process for zinc, indium and tin leaching. Background Art

[0002] With the continuous development of the comprehensive utilization technology level of solid waste resources, the utilization value of metallurgical solid waste resources containing valuable metals such as zinc, indium, tin, and bismuth has been increasingly emphasized by society. In the process of producing zinc sulfate by wet zinc smelting with secondary zinc oxide as the raw material, the neutral leaching residue is a rich indium and tin waste residue, containing various valuable metal elements such as indium, zinc, tin, and bismuth. By adopting a reasonable process for harmless treatment, many valuable metals can be recovered. In particular, associated rare and dispersed metals such as indium, tin, and bismuth have considerable recovery prospects, which not only solves the resource problem but also solves the environmental protection problem, and can promote the green and sustainable development of the metallurgical industry.

[0003] At present, extraction, ion exchange, liquid membrane and other methods are mainly used to separate and recover indium and tin from the leaching solution of the leaching residue. However, the components in the leaching residue are complex, and indium, tin, zinc, and bismuth coexist, and the current recovery and utilization effect is not ideal. Summary of the Invention

[0004] The present invention aims to provide a two-stage acid leaching process for zinc, indium and tin leaching to recover indium and tin.

[0005] The technical solution adopted by the present invention to achieve its purpose:

[0006] The two-stage acid leaching process for zinc, indium and tin leaching includes the following steps:

[0007] S1. Low-acid leaching: Using the neutral leaching residue in the process of producing zinc sulfate from secondary zinc oxide as the raw material, adding lead sludge rinsing water, bismuth residue rinsing water, and the high-acid leaching filtrate obtained in step S2 (when there is no high-acid leaching solution, adding lead sludge rinsing water, neutral leaching residue, and 92% sulfuric acid in the high-leaching tank and reacting for 2 - 2.5 hours, with a final acidity of 220 - 250 g / L), reacting in a reaction tank for 2 - 2.5 hours, with a final acidity of 140 - 160 g / L. After the reaction, filtration is carried out to obtain a low-acid leaching filtrate and a low-acid leaching filter cake. The low-acid leaching filtrate is reserved for use, and the low-acid leaching filter cake enters the high-acid leaching process;

[0008] The high-acid leaching process is as follows: Add the low-acid leaching filter cake obtained in step S1 to a reaction kettle, add 92% sulfuric acid (it is also possible to add the high-acid leaching filtrate from the first reaction, which is the lead mud rinsing water and bismuth slag rinsing water for neutral leaching residue), react for 2 - 2.5 h, and the final acidity is 220 - 250 g / L. After the reaction for 2 - 2.5 hours and the final acidity of 220 - 250 g / L, after filtration, a high-acid leaching filtrate and a high-acid leaching filter cake are obtained. The high-acid leaching filtrate is returned to step S1, and the rinsing liquid obtained after rinsing the high-acid leaching filter cake is also returned to step S1;

[0009] S2. Bismuth removal: Add iron powder to the low-acid leaching filtrate obtained in step S1 for reaction. The end-point acidity of the reaction is 120 - 140 g / L. Potassium thiocyanate is used for qualitative detection of ferric iron without trace, and thiourea is used for qualitative detection of bismuth without trace. After the reaction, after filtration, the bismuth-removed filtrate enters the indium and tin extraction process. The filter cake is acid-rinsed and pressure-filtered, and the acid-rinsed and pressure-filtered liquid is returned to step S1;

[0010] S3. Indium and tin extraction: Use the lean extract in the stripping process to extract the bismuth-removed filtrate (when there is no lean extract, P204 and light white oil need to be mixed in a ratio of 2:1). The ratio of bismuth-removed water to oil is 3:1, the temperature is 60 - 70 °C, and four-stage countercurrent continuous extraction is carried out. The final extract enters the stripping process; When the extraction effect decreases, the oil and water are difficult to separate, and the indium content in the raffinate is high, the extract needs to be alkali-washed and acid-washed to wash out supersaturated impurities such as tin in the organic phase.

[0011] S4. Stripping: Pump the extract from step S3 into a stripping tank, add 6 mol / L hydrochloric acid for indium stripping, and then add 10 - 12 mol hydrochloric acid for tin stripping. Four-stage countercurrent continuous stripping is carried out. The ratio of oil to hydrochloric acid is 15:1. The upper-layer lean extract is returned to step S3, and the stripping liquid enters the neutralization process. The raffinate is used to treat the leaching residue;

[0012] S5. Neutralization: The indium stripping liquid enters the indium neutralization tank, add liquid caustic soda, and the acidity after neutralization is about 2 - 2.5 mol / L to obtain indium neutralized water; The tin stripping liquid enters the tin neutralization tank, add liquid caustic soda, and the acidity after neutralization is about 1.3 - 1.8 mol / L to obtain tin neutralized water;

[0013] S6. Tin removal from indium neutralized water: Add the indium neutralized water in step S5 to the tin removal tanks 3# and 4#, add zinc plates to remove tin. After qualitative detection of tin without trace, the tin-removed water is filtered and pumped into the indium replacement tank. Add zinc flakes for reaction. The reaction temperature is 40 - 60 °C. After the reaction for 3 - 4 hours, the sponge indium is fished out. After the reaction, press the cake and melt-cast it with molten sodium hydroxide to obtain the by-product crude indium.

[0014] S7. Tin neutralization and tin removal with water: Add the tin-neutralized water from step S5 into the No. 1 and No. 1 tin-removal tanks, add zinc plates to displace tin, keep the temperature at 40 - 60 °C, after reacting for 3 - 4 hours, fish out the wet tin dross, rinse and centrifuge to obtain the by-product tin concentrate.

[0015] Furthermore, the neutral leaching residue described in step S1 is specifically prepared by the following method:

[0016] Using zinc suboxide as the initial raw material, after three times of rinsing, add the filter cake into the acidic zinc sulfate solution, control the end-point pH at 4.5 - 5.0 for reaction, after the reaction ends, filter, and the filter cake is the neutral leaching residue.

[0017] Furthermore, the three times of rinsing are as follows (when there is no rinsing filtrate, it can be rinsed with multi-effect condensed water):

[0018] First rinsing: Use the filtrate of the second rinsing as the rinsing liquid, add caustic soda, displacement tail water, and acid mist absorption tower water in a closed stirring tank to adjust the pH value to 8.5 - 9, then conduct rinsing, after rinsing, filter, the filtrate goes to the water treatment system, and the filter cake is subjected to the second rinsing;

[0019] Second rinsing: Use the filtrate of the steel ash rinsing as the rinsing liquid, after rinsing in the stirring tank, filter, the filtrate is recycled for the first rinsing, and the filter cake is subjected to the third rinsing;

[0020] Third rinsing: The third rinsing is carried out in the stirring tank with fresh water and multi-effect evaporation condensed water, after rinsing, filter, the filtrate is recycled for the steel ash rinsing, and the filter cake enters the subsequent process.

[0021] Furthermore, the filtrate of the steel ash rinsing is the filtrate after the filtrate of the third rinsing is used to rinse the steel ash.

[0022] Furthermore, during the acid bleaching treatment in step S3, control the acidity at 90 g / L.

[0023] The beneficial effects of the present invention are:

[0024] The method of the present invention is simple and environmentally friendly, without generating waste water and waste residue, meeting the national production requirements of green, safe and environmental protection. The method of the present invention can improve the purity of crude indium and tin concentrate, and separate them better. Finally, the indium recovery rate ≥ 85%, and the tin recovery rate ≥ 30%. Description of the Drawings

[0025] Figure 1 is the process flow chart of the present invention. Detailed Embodiments

[0026] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0027] Example 1

[0028] Secondary zinc oxide powder, the composition is shown in Table 1.

[0029] Table 1

[0030] Element Zn Fe Pb K In Sn Content / % 40 4 5 7 0.03 0.2

[0031] 1. Using secondary zinc oxide powder as raw material, the secondary zinc oxide powder is rinsed three times:

[0032] First rinse: For the first rinse, the filtrate from the second rinse is used as the rinsing solution. In a closed stirring tank, caustic soda, replacement tail water, and acid mist absorption tower water are added to adjust the pH value to 8.5 - 9, and then rinsing is carried out. After rinsing, it is filtered by a plate and frame filter. The filtrate (mainly containing a small amount of zinc chloride, sodium chloride, and potassium chloride) goes to the water treatment system, and the filter cake is subjected to a second rinse. Since the pH value is 8.5 - 9 and the temperature is about 70°C after adding caustic soda, ammonia gas overflows from the solution in the plate and frame under the conditions of high temperature and high pH value.

[0033] Second rinse: For the second rinse, the filtrate from the steel ash rinse is used as the rinsing solution. After rinsing in a stirring tank, it is filtered by a plate and frame filter. The filtrate is recycled for the first rinse, and the filter cake is subjected to a third rinse.

[0034] Third rinse: For the third rinse, fresh water and multi-effect evaporation condensate water are used for rinsing in a stirring tank. After rinsing, it is filtered by a plate and frame filter. The filtrate is recycled for the steel ash rinse, and the filter cake goes to neutral leaching.

[0035] 2. Neutral leaching

[0036] Neutral leaching is to add the filter cake from the third rinse to the raffinate (mainly composed of sulfuric acid and ferrous sulfate) and the acid leaching solution (acidic zinc sulfate solution). The filter cake is added until the pH value of the solution reaches 5.2 - 5.5. ZnO, FeO, and CdO react with sulfuric acid to form ZnSO4, FeSO4, and CdSO4 respectively.

[0037] The reacted solution is filtered by a plate and frame filter. The filtrate enters the iron removal by oxidation process; the filter cake goes to low-acid leaching.

[0038] 3. Low-acid leaching

[0039] Low-acid leaching is to add neutral leaching filter cake, lead sludge rinsing water, bismuth residue rinsing water, and high-acid leaching filtrate (when there is no high-acid leaching solution, add lead sludge rinsing water, neutral leaching residue, and 92% sulfuric acid to the high-leaching tank and react for 2 - 2.5 hours, with the final acidity of 220 - 250 g / L, then filter to obtain high-acid leaching solution) to the low-acid reaction tank for low-acid leaching. React for 2 - 2.5 hours, with the final acidity of 140 - 160 g / L. In2O3, SnO2, and Bi2O3 react with sulfuric acid to form trace amounts of In2(SO4)3, Sn(SO4)2, and Bi2(SO4)3 respectively. After the low-acid leaching slurry enters the plate and frame filter press for filtration, the filter cake is sent for high-acid leaching; the filtrate goes to the bismuth removal by displacement process.

[0040] For the composition of the low-acid leaching filtrate, see Table 2.

[0041] Table 2

[0042] Element Volume (m³) Zn (g / L) Fe (g / L) In (g / L) Sn (g / L) Bi (g / L) Content 30 40 20 0.5 1 0.6

[0043] 4. High-acid leaching

[0044] High-acid leaching is to add 92% sulfuric acid to the low-acid leaching filter cake for high-acid leaching. React for 2 - 2.5 hours, with the final acidity of 220 - 250 g / L, so that In2O3, SnO2, and Bi2O3 in the filter cake react with sulfuric acid to form In2(SO4)3, Sn(SO4)2, and Bi2(SO4)3, and maximize the leaching of valuable metals in the material. After the high-acid leaching solution passes through the plate and frame filter press, the filtrate is returned to low-acid leaching; add the filter cake to the rinsing tank, inject fresh water for rinsing to remove the remaining In 3+ , Sn 4+ , Zn 2+ , and the rinsing solution enters the plate and frame filter press for filtration to obtain the by-product lead concentrate (lead ≥ 25%); the filtrate is returned to low-acid leaching.

[0045] For the composition of the high-acid leaching filtrate, see Table 3.

[0046] Table 3

[0047] Element Volume (m³) Zn (g / L) Fe (g / L) In (g / L) Sn (g / L) Bi (g / L) Content 30 70 35 0.9 1.5 1.1

[0048] 5. Bismuth removal by displacement

[0049] The low-acid leaching filtrate enters the bismuth removal by displacement tank, add iron powder, and the end-point acidity of the reaction is 120 - 140 g / L. Potassium thiocyanate is used for qualitative determination of ferric iron with no trace, and thiourea is used for qualitative determination of bismuth with no trace. The Bi in the solution 3+ is displaced by iron to form sponge bismuth, removing Bi in the solution 3 +, crude bismuth is obtained. After removing bismuth by displacement, it is pumped into a plate and frame filter press for filtration. The filtrate goes to the extraction process; the filter cake is added with water and sulfuric acid to control the acidity at 90 g / L for acid bleaching. After acid bleaching, it is filtered to obtain the by-product crude bismuth (Bi≥20%); the acid bleaching filtrate is recycled for low-acid leaching.

[0050] The composition of the filtrate after bismuth removal is shown in Table 4.

[0051] Table 4

[0052] Element Volume (m³) Zn (g / L) Fe (g / L) In (g / L) Sn (g / L) Bi (g / L) Content 30 40 30 0.5 1 0

[0053] 6. Extraction

[0054] Use the lean extractant from the stripping process to extract In2(SO4)3 and Sn(SO4)2 from the filtrate after bismuth removal by displacement. (When there is no lean extractant, P 204 and light white oil are mixed in a ratio of 2:1), the ratio of water to oil for bismuth removal is 3:1, the temperature is 60 - 70 °C, and four-stage countercurrent continuous extraction is carried out. The final extractant enters the stripping process, and the lower raffinate is recycled for the neutral leaching process. When the extraction effect decreases, the oil and water are difficult to separate, and the indium content in the raffinate is high, the extractant needs to be alkali-washed and acid-washed to wash out the supersaturated impurities such as tin in the organic phase.

[0055] The composition table of the extractant is shown in Table 5.

[0056] Table 5

[0057]

[0058]

[0059] The composition table of the raffinate is shown in Table 6.

[0060] Table 6

[0061] Element Volume (m³) Zn (g / L) Fe (g / L) In (g / L) Sn (g / L) Bi (g / L) Content 30 40 30 0.03 0.17 0

[0062] 7. Stripping

[0063] Pump the extractant into the stripping tank, add 6 mol / L hydrochloric acid for indium stripping, and then add 10 - 12 mol / L hydrochloric acid for tin stripping. Four-stage countercurrent continuous stripping is carried out, and the ratio of oil to hydrochloric acid is 15:1. The upper lean extractant is returned to the indium and tin extraction process, the stripping solution enters the neutralization process, and the raffinate is used for treating the leaching residue.

[0064] The composition of the indium stripping solution is shown in Table 7.

[0065] Table 7

[0066] Element Volume (m³) Zn (g / L) Fe (g / L) In (g / L) Sn (g / L) Bi (g / L) Content 0.67 0 0 20.5 0.5 0

[0067] The composition of the tin stripping solution is shown in Table 8.

[0068] Table 8

[0069] Element Volume (m³) Zn (g / L) Fe (g / L) In (g / L) Sn (g / L) Bi (g / L) Content 0.67 0 0 0.2 25.5 0

[0070] For the composition of the lean extractant, refer to Table 9.

[0071] Table 9

[0072] Element Volume (m³) Zn (g / L) Fe (g / L) In (g / L) Sn (g / L) Bi (g / L) Content 10 0 0 0.01 0.8 0

[0073] 8. Neutralization and replacement for removing tin

[0074] The indium stripping solution enters the indium neutralization tank, and liquid caustic soda is added. After neutralization, the acidity is about 2 - 2.5 mol / L to obtain indium neutralized water; the tin stripping solution enters the tin neutralization tank, and liquid caustic soda is added. After neutralization, the acidity is about 1.3 - 1.8 mol / L to obtain tin neutralized water.

[0075] For the indium neutralized water, refer to Table 10.

[0076] Table 10

[0077] Element Volume (m³) Zn (g / L) Fe (g / L) In (g / L) Sn (g / L) Bi (g / L) Content 0.8 0 0 17 0.8 0

[0078] For the composition of the tin neutralized water, refer to Table 11

[0079] Table 11

[0080] Element Volume (m³) Zn (g / L) Fe (g / L) In (g / L) Sn (g / L) Bi (g / L) Content 0.9 0 0 0.15 18.7 0

[0081] 9. The indium neutralized water goes for tin replacement

[0082] Add the indium neutralized water into the tin - removing tanks No. 3 and No. 4, add zinc plates to remove tin. After qualitative detection shows no trace of tin, the tin - removed water is filtered and pumped into the indium replacement tank. Add zinc flakes for reaction. The reaction temperature is 40 - 60 °C. After 3 - 4 hours of reaction, the sponge indium is fished out. After the reaction ends, press cakes and melt - cast with molten sodium hydroxide to obtain the by - product crude indium (indium content ≥ 98%). The principle of tin removal is that due to the different metallic activity orders of zinc, indium, and tin, tin is the least active, and it is preferentially displaced after adding zinc plates.

[0083] 10. The tin neutralized water goes for tin removal

[0084] Add the tin neutralized water into the tin - removing tanks No. 1 and No. 1, add zinc plates to replace tin. At a temperature of 40 - 60 °C, after 3 - 4 hours of reaction, the wet tin slag is fished out, rinsed, and centrifuged to obtain the by - product tin concentrate.

[0085] For the leaching rate and recovery rate of each element, refer to Table 12.

[0086] Table 12

[0087]

Claims

1. Two-stage acid leaching process for zinc, indium and tin, characterized in that, It includes the following steps: S1. Low-acid leaching: Using the neutral leaching residue in the process of producing zinc sulfate from secondary zinc oxide as raw material, adding lead sludge rinsing water, bismuth residue rinsing water, and high-acid leaching filtrate, reacting in a reaction tank for 2 - 2.5 h, with the final acidity being 140 - 160 g / L. After the reaction ends, through filtration, a low-acid leaching filtrate and a low-acid leaching filter cake are obtained. The low-acid leaching filtrate is reserved for later use, and the low-acid leaching filter cake enters the high-acid leaching process; S2. Bismuth removal: Adding iron powder to the low-acid leaching filtrate obtained in step S1 for reaction, with the reaction end-point acidity being 120 - 140 g / L, and using potassium thiocyanate for qualitative detection of ferric iron with no trace and thiourea for qualitative detection of bismuth with no trace. After the reaction ends, through filtration, the bismuth-removed filtrate enters the indium and tin extraction process. The filter cake is acid-leached and pressure-filtered, and the acid-leached and pressure-filtered filtrate is returned to step S1. When performing acid-leaching treatment, the acidity is controlled at 90 g / L; S3. Indium and tin extraction: Adding an extractant to extract the bismuth-removed filtrate, with the volume ratio of bismuth-removed water to oil being 3:1, at a temperature of 60 - 70 °C, and performing four-stage countercurrent continuous extraction. The obtained extract enters the stripping process; S4. Stripping: Pumping the extract in step S3 into a stripping tank, adding 6 mol / L hydrochloric acid for indium stripping, and then adding 10 - 12 mol / L hydrochloric acid for tin stripping, and performing four-stage countercurrent continuous stripping. The volume ratio of the extract in S3 to hydrochloric acid is 15:

1. The upper-layer lean extract is returned to step S3, and the stripping solution enters the neutralization process. The raffinate is used for treating leaching residues; S5. Neutralization: The indium stripping solution enters an indium neutralization tank, adding liquid caustic soda, with the acidity after neutralization being 2 - 2.5 mol / L to obtain indium-neutralized water; the tin stripping solution enters a tin neutralization tank, adding liquid caustic soda, with the acidity after neutralization being 1.3 - 1.8 mol / L to obtain tin-neutralized water; S6. Removing tin from indium-neutralized water: Adding the indium-neutralized water to a first tin-removing tank, adding zinc plates to remove tin. After qualitative detection shows no trace of tin, the tin-removed water is filtered and pumped into an indium replacement tank, adding zinc flakes for reaction. The reaction temperature is 40 - 60 °C. After reacting for 3 - 4 hours, the spongy indium is fished out. After the reaction ends, it is pressed into cakes and melted and cast using molten sodium hydroxide to obtain the by-product crude indium; S7. Removing tin from tin-neutralized water: Adding the tin-neutralized water in step S5 to a second tin-removing tank, adding zinc plates to displace tin, at a temperature of 40 - 60 °C. After reacting for 3 - 4 hours, the wet tin slag is fished out, rinsed, and centrifuged to obtain the by-product tin concentrate.

2. The two-stage acid leaching zinc indium tin leaching process according to claim 1, characterized in that The neutral leaching residue described in step S1 is specifically prepared by the following method: Using secondary zinc oxide as the initial raw material, after three times of rinsing, adding the filter cake to an acidic zinc sulfate solution, controlling the end-point pH at 5.2 - 5.

5. After the reaction ends, through filtration, the filter cake is the neutral leaching residue.

3. The two-stage acid leaching process for zinc, indium, and tin according to claim 2, characterized in that, The three times of rinsing are as follows: First rinsing: Using the secondary-rinsing filtrate as the rinsing solution, adding caustic soda flakes, displacement tail water, and acid mist absorption tower water in a closed stirring tank to adjust the pH value to 8.5 - 9, and then performing rinsing. After rinsing, through filtration, the filtrate goes to the water treatment system, and the filter cake is subjected to secondary rinsing; Second rinsing: Using the steel ash rinsing filtrate as the rinsing solution, rinsing in a stirring tank and then through filtration. The filtrate is recycled for first rinsing, and the filter cake is subjected to third rinsing; Three - stage rinsing: In the three - stage rinsing process, fresh water and multi - effect evaporation condensate water are used to rinse in a stirring tank. After rinsing, it is filtered, the filtrate is recycled for rinsing steel ash, and the filter cake enters the subsequent process.

4. The two-stage acid leaching process for zinc, indium, and tin according to claim 1, characterized in that, The high - acid leaching process is as follows: The low - acid leaching filter cake obtained in step S1 is added to a reaction kettle, 92% sulfuric acid by mass concentration is added, and the reaction lasts for 2 - 2.5 h. The final acidity is 220 - 250 g / L. After the reaction ends, it is filtered to obtain a high - acid leaching filtrate and a high - acid leaching filter cake. The high - acid leaching filtrate is returned to step S1, and the rinsing liquid obtained after rinsing the high - acid leaching filter cake is also returned to step S1.

5. The two-stage acid leaching process for zinc, indium, and tin according to claim 1, characterized in that, In step S1, the high - acid leaching filtrate is prepared in the following way: First, lead sludge rinsing water, neutral leaching residue, and 92% sulfuric acid are added to a high - leaching tank and reacted for 2 - 2.5 hours. The final acidity is 220 - 250 g / L. After filtration, the high - acid leaching filtrate is obtained.

6. The two-stage acid leaching process for zinc indium tin according to claim 1, characterized in that, In step S3, the extractant is the lean extractant from the stripping process; or an extractant formed by mixing P204 and light white oil in a ratio of 2:1.

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