A graded treatment method of heavy metal wastewater containing antimony, gallium and indium

Abstract

The application discloses a kind of grading treatment methods of heavy metal wastewater containing antimony, gallium, indium, belongs to wastewater treatment technical field.The application proposes the comprehensive process of grading treatment, accurate process parameter control and optimization reagent addition for high-concentration heavy metal wastewater containing antimony, gallium, indium (Sb≥50 mg / L;Ga+In total amount≥10 mg / L), realizes the efficient removal of heavy metal and resource recovery, while significantly reduces processing cost and reagent consumption.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to a graded treatment method for wastewater containing antimony, gallium, and indium heavy metals. Background Technology

[0002] Antimonide infrared technology, as an important development direction in the semiconductor field, relies on the preparation and industrial application of single-crystal materials such as indium antimonide (InSb) and gallium antimonide (GaSb). During the large-scale production of antimonide single-crystal growth, industrial wastewater characterized by high concentrations of antimony (Sb) is generated, often exceeding 50 mg / L. This wastewater is also accompanied by heavy metal ions with high recovery value, such as gallium (Ga) and indium (In), and in some wastewater systems, the total Ga and In content exceeds 10 mg / L. Treating this type of high-concentration heavy metal ion wastewater is significantly more difficult than treating conventional low-concentration heavy metal-containing wastewater.

[0003] If such high-concentration wastewater containing heavy metals is discharged directly, it will cause serious pollution to the ecological environment. It will not only disrupt the ecological balance of water and soil, but also endanger human health through bioaccumulation in the food chain. Therefore, it must be strictly treated before it can be discharged. Currently, the industry generally uses alkaline neutralization and precipitation processes to treat this type of wastewater containing high concentrations of heavy metals such as Sb, Ga, and In. However, for high-concentration scenarios where Sb content is >50 mg / L and / or the total Ga and In content is >10 mg / L, the technical defects of this process are particularly prominent. It mainly consists of the following two implementation methods, each with obvious shortcomings: First, when sodium hydroxide is used as a neutralizing precipitant, not only is the reagent procurement cost high, resulting in poor economic efficiency of the treatment process, but also, in high-concentration systems where Sb content is >50 mg / L and / or the total Ga and In content is >10 mg / L, the antimony-based precipitates generated by the reaction are prone to redissolution. At the same time, the precipitation of Ga and In ions is incomplete, resulting in poor removal efficiency of metal ions and low recovery rates of Sb, Ga, and In, which makes it difficult to meet the current stringent environmental emission standards and resource recovery requirements. Secondly, when calcium hydroxide is used as a neutralizing precipitant, a large amount of calcium ions are introduced into the wastewater system. These calcium ions easily combine with anions in the water to form insoluble salts such as calcium carbonate, which in turn causes frequent blockages in the pipelines and equipment of the treatment system, significantly increasing the daily operation and maintenance costs and the frequency of shutdowns for repairs. Especially in high-concentration scenarios where the Sb content is >50mg / L and / or the total Ga and In content is >10mg / L, the combined co-precipitation of heavy metal ions and calcium ions will further aggravate the scaling and blockage problems in the pipelines. At the same time, the purity of the precipitate is low, which is not conducive to the subsequent recovery and purification of precious metals such as Ga and In.

[0004] While the two alkaline neutralization and precipitation processes mentioned above can achieve preliminary removal of heavy metal ions from wastewater, they both have significant technical shortcomings for high-concentration heavy metal wastewater with Sb content > 50 mg / L and / or total Ga and In content > 10 mg / L. They cannot simultaneously achieve treatment effectiveness, resource recovery, and economic rationality, thus restricting their large-scale and industrial application in the treatment of high-concentration wastewater from antimony single crystal growth. Therefore, it is urgent to develop a treatment technology that is suitable for this high-concentration scenario and takes into account both environmental protection and resource recovery. Summary of the Invention

[0005] Therefore, the purpose of this invention is to provide a graded treatment method for wastewater containing antimony, gallium, and indium heavy metals.

[0006] This invention provides a graded treatment method for wastewater containing antimony, gallium, and indium heavy metals, comprising the following steps: S1: Antimony, gallium and indium in heavy metal wastewater containing antimony, gallium and indium are detected. When the Sb content in the wastewater containing antimony, gallium and indium is >50mg / L and / or the total content of Ga and In is >10mg / L, it enters the first gradient treatment process. S2: The first gradient processing technology is: S2-1: Add Ca(OH)2 to the wastewater containing antimony, gallium and indium heavy metals, control the pH of the wastewater to 7.0~8.0, stir to carry out precipitation reaction, after the reaction is completed, add polyferric sulfate (PFS), stir to mix well, then add polyacrylamide (PAM) aqueous solution, stir a second time, and let stand; S2-2: Take the supernatant after settling and test it: ① When Sb < 0.3 mg / L and the total content of Ga and In < 1 mg / L in the supernatant, add sodium carbonate to the wastewater for calcium precipitation. After calcium precipitation, the wastewater is filtered by pressure to obtain sludge and wastewater with heavy metals removed; ② When the content of Sb in the supernatant is 0.3 mg / L ≤ 50 mg / L and / or the total content of Ga and In is 1 mg / L ≤ 10 mg / L, filter to obtain sludge and wastewater. The wastewater enters the second gradient treatment process; ③ When the content of Sb in the supernatant is > 50 mg / L and / or the total content of Ga and In is > 10 mg / L, repeat step S2-1 until it meets ① or ②, and proceed to the next step accordingly; S3: The second gradient processing technology is: S3-1: Add NaOH or hydrochloric acid to the wastewater to control the pH of the wastewater to 8-9, stir to carry out the precipitation reaction, after the reaction is completed, add polyferric sulfate (PFS), stir to mix well, then add polyacrylamide (PAM) aqueous solution, stir again, and let stand. S3-2: Take the supernatant after settling and test it: ① When the Sb content in the supernatant is <0.3mg / L and the total content of Ga and In is <1mg / L, filter it to obtain sludge and wastewater with heavy metals removed; ② When the Sb content in the supernatant is ≥0.3mg / L and / or the total content of Ga and In is ≥1mg / L, repeat step S3-1 until it meets ①, and proceed to the next step.

[0007] Preferably, in step S1, when the Sb content in the wastewater containing antimony, gallium, and indium is ≤50mg / L and the total Ga and In content is ≤10mg / L, it directly enters the second gradient treatment process.

[0008] Preferably, in step S2-1, the precipitation reaction time is 15-30 min; the stirring and mixing time is 3-8 min; the secondary stirring time is 1-5 min; and the standing time is 1.5-2.5 h.

[0009] Preferably, in step S2-1, the concentration of polyferric sulfate added to the wastewater is 3~3.5 g / L; the mass concentration of the polyacrylamide aqueous solution is 0.5~1.5%, and the volume ratio of the polyacrylamide aqueous solution added to the wastewater is 0.5~1 L / m³. 3 .

[0010] Preferably, in step S2-2, the specific steps for adding sodium carbonate to the wastewater for calcium precipitation are as follows: based on the Ca concentration in the supernatant, sodium carbonate is added at a mass concentration of 2 to 4 times that of Ca. After stirring and reacting for 0.5 to 1.5 hours, the mixture is allowed to stand for 3 to 5 hours. The Ca concentration in the supernatant is then detected. ① If the Ca concentration is <200 mg / L, the mixture is allowed to proceed to the pressure filtration step. ② If the Ca concentration is ≥200 mg / L, the calcium precipitation step is repeated until the Ca concentration is <200 mg / L.

[0011] Preferably, in step S3-1, the precipitation reaction time is 20-40 min; the stirring and mixing time is 3-8 min; the secondary stirring time is 1-5 min; and the standing time is 1.5-2.5 h.

[0012] Preferably, in step S3-1, the concentration of polyferric sulfate added to the wastewater is 1~3 g / L; the mass concentration of the polyacrylamide aqueous solution is 0.5~1.5%, and the volume ratio of the polyacrylamide aqueous solution added to the wastewater is 0.5~1 L / m³. 3 .

[0013] Preferably, in steps S2-2 and S3-2, the obtained sludge is subjected to plate and frame filtration, heavy metal ions are recovered from the filter residue, and the filtrate is returned to the wastewater containing antimony, gallium, and indium in step S1.

[0014] Preferably, in steps S2-2 and S3-2, the wastewater from which heavy metals have been removed is discharged directly.

[0015] Compared with the prior art, one or more of the above technical solutions can achieve at least one of the following beneficial effects: This invention proposes a comprehensive process for treating high-concentration wastewater containing antimony, gallium, and indium (Sb≥50 mg / L; total Ga+In≥10 mg / L), which includes graded treatment, precise process parameter control, and optimized reagent dosing. This process achieves efficient removal of heavy metals and resource recovery, while significantly reducing treatment costs and reagent consumption. Attached Figure Description

[0016] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0017] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0018] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0019] As mentioned above, the present invention provides a graded treatment method for wastewater containing antimony, gallium, and indium heavy metals, comprising the following steps: S1: Antimony, gallium and indium in heavy metal wastewater containing antimony, gallium and indium are detected. When the Sb content in the wastewater containing antimony, gallium and indium is >50mg / L and / or the total content of Ga and In is >10mg / L, it enters the first gradient treatment process. S2: The first gradient processing technology is: S2-1: Add Ca(OH)2 to the wastewater containing antimony, gallium and indium heavy metals, control the pH of the wastewater to 7.0~8.0, stir to carry out precipitation reaction, after the reaction is completed, add polyferric sulfate (PFS), stir to mix well, then add polyacrylamide (PAM) aqueous solution, stir a second time, and let stand; S2-2: Take the supernatant after settling and test it: ① When Sb < 0.3 mg / L and the total content of Ga and In < 1 mg / L in the supernatant, add sodium carbonate to the wastewater for calcium precipitation. After calcium precipitation, the wastewater is filtered to obtain sludge and wastewater with heavy metals removed; ② When the content of Sb in the supernatant is 0.3 mg / L ≤ 50 mg / L and / or the total content of Ga and In is 1 mg / L ≤ 10 mg / L, filter to obtain sludge and wastewater. The wastewater enters the second-gradient treatment process; ③ When the content of Sb in the supernatant is > 50 mg / L and / or the total content of Ga and In is > 10 mg / L, repeat step S2-1 until it meets ① or ②, and proceed to the next step accordingly; S3: The second gradient processing technology is: S3-1: Add NaOH or hydrochloric acid to the wastewater to control the pH of the wastewater to 8-9, stir to carry out the precipitation reaction, after the reaction is completed, add polyferric sulfate (PFS), stir to mix well, then add polyacrylamide (PAM) aqueous solution, stir again, and let stand. S3-2: Take the supernatant after settling and test it: ① When the Sb content in the supernatant is <0.3mg / L and the total content of Ga and In is <1mg / L, filter it to obtain sludge and wastewater with heavy metals removed; ② When the Sb content in the supernatant is ≥0.3mg / L and / or the total content of Ga and In is ≥1mg / L, repeat step S3-1 until it meets ①, and proceed to the next step.

[0020] This invention proposes a comprehensive process for treating high-concentration wastewater containing antimony, gallium, and indium (Sb≥50 mg / L; total Ga+In≥10 mg / L), which includes graded treatment, precise process parameter control, and optimized reagent dosing. This process achieves efficient removal of heavy metals and resource recovery, while significantly reducing treatment costs and reagent consumption.

[0021] Firstly, this invention employs a unique dosing sequence for high-concentration wastewater treatment: first adjusting pH with Ca(OH)2, then adding PFS to enhance flocculation. Combined with a precise pH control window of 7.0-8.0, this fundamentally solves the industry pain point of Sb's easy re-dissolution in traditional treatment processes, ensuring stable and compliant Sb removal. It also significantly improves the precipitation efficiency of two high-value metals, Ga and In, achieving a removal rate of over 99%. Simultaneously, this process design greatly increases the enrichment of Ga and In in the precipitated sludge, making the sludge a high-quality raw material for the resource recovery of high-value metals. This achieves synergistic progress in "treatment compliance" and "resource recovery," enhancing the added value of wastewater treatment.

[0022] Secondly, this invention optimizes the reagent ratio based on wastewater concentration differences. In the high-concentration wastewater stage, which is the main stage for reagent consumption, Ca(OH)2, which costs only 1 / 3 of NaOH, is selected as the main alkali agent. This significantly reduces reagent consumption costs in the high-concentration stage while ensuring efficient precipitation of Sb, Ga, and In. In the low-concentration wastewater stage, only a small amount of NaOH is needed to adjust the pH, eliminating the need for additional reagent input. Overall, this achieves optimized control of reagent costs. Compared to traditional single-alkali agent treatment processes, the comprehensive reagent cost is significantly reduced, improving the process's economic efficiency and market applicability.

[0023] Third, this invention uses the concentration thresholds of Sb (50 mg / L) and Ga / In (10 mg / L) as clear boundaries to construct a differentiated treatment process for high and low concentrations, significantly improving the system's adaptability to fluctuations in water quality. The high-concentration stage incorporates a cyclic treatment mechanism, repeatedly executing sedimentation, flocculation, and settling processes until the wastewater meets standards before proceeding to the next stage. The low-concentration stage employs a simplified process design, achieving stable compliance without complex operations. This tiered design significantly enhances the system's resistance to shock loads, ensuring stable removal of heavy metals regardless of initial wastewater concentration fluctuations (final compliance: Sb < 0.3 mg / L, total Ga and In content < 1 mg / L), improving the stability and reliability of process operation, and making it suitable for treating various high-concentration wastewater containing antimony, gallium, and indium.

[0024] Fourth, the core advantages of this invention lie in "precise grading, optimized parameters, and rationalized operation": It clearly defines the optimal precipitation pH window of 7.0-8.0 in the high-concentration range, providing a crucial guarantee for the simultaneous and efficient precipitation of the three metals; the specific order of "Ca(OH)2 added first" in the high-concentration range is the core design for achieving high-value enrichment and recovery of Ga and In; and the selection of NaOH to replace Ca(OH)2 in the low-concentration range is a key measure to avoid scaling and save on operation and maintenance costs. The entire process flow is seamless and easy to operate, requiring no complex equipment upgrades. It not only meets the requirements for heavy metal emission compliance but also achieves resource recovery and cost savings, possessing strong practical application value and promising prospects for promotion.

[0025] In some embodiments, in step S1, when the Sb content in the wastewater containing antimony, gallium, and indium heavy metals is ≤50mg / L and the total Ga and In content is ≤10mg / L, the wastewater enters the second gradient treatment process.

[0026] In this invention, low-concentration wastewater uses NaOH as the alkali source, eliminating the need to introduce calcium ions and preventing pipe scaling at its source. This significantly reduces system cleaning frequency and equipment wear, extends equipment lifespan, and saves on long-term operation and maintenance costs. Furthermore, the staged treatment mode enhances the process's adaptability to different water qualities; high-concentration sections can be treated through recirculation until standards are met, effectively improving the system's resistance to shock loads and ensuring overall operational flexibility and stability.

[0027] In some embodiments, in step S2-1, the precipitation reaction time is 15-30 min, including but not limited to: 15 min, 18 min, 20 min, 22 min, 25 min, 30 min, etc.; the stirring and mixing time is 3-8 min, including but not limited to: 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, etc.; the secondary stirring time is 1-5 min, including but not limited to: 1 min, 2 min, 3 min, 4 min, 5 min, etc.; and the standing time is 1.5-2.5 h, including but not limited to: 1.5, 1.75 h, 2 h, 2.25 h, 2.5 h, etc.

[0028] In some embodiments, in step S2-1, the concentration of polyferric sulfate added to the wastewater is 3~3.5 g / L, including but not limited to: 3 g / L, 3.1 g / L, 3.2 g / L, 3.3 g / L, 3.4 g / L, 3.5 g / L, etc.; the mass concentration of the polyacrylamide aqueous solution is 0.5~1.5%, including but not limited to: 0.5%, 0.8%, 1.0%, 1.2%, 1.5%, etc.; the ratio of the volume of polyacrylamide aqueous solution added to the volume of wastewater is 0.5~1 L / m³. 3 Including but not limited to: 0.5L / m 3 0.6L / m 3 0.7L / m 3 0.8L / m 3 0.9L / m 3 1.0L / m 3 wait.

[0029] In some embodiments, the specific steps for adding sodium carbonate to the wastewater for calcium precipitation in step S2-2 are as follows: Based on the Ca concentration in the supernatant, sodium carbonate is added at a mass concentration 2 to 4 times (including but not limited to: 2 times, 3 times, 4 times, etc.) of the Ca mass concentration. After stirring and reacting for 0.5 to 1.5 hours (including but not limited to: 0.5 hours, 0.75 hours, 1 hour, 1.25 hours, 1.5 hours, etc.), the mixture is allowed to stand for 3 to 5 hours (including but not limited to: 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, etc.). The Ca concentration in the supernatant is then detected. ① If the Ca concentration is <200 mg / L, the pressure filtration step is initiated. ② If the Ca concentration is ≥200 mg / L, the calcium precipitation step is repeated until the Ca concentration is <200 mg / L.

[0030] In some embodiments, in step S3-1, the precipitation reaction time is 20-40 min, including but not limited to: 20 min, 22 min, 25 min, 28 min, 30 min, 32 min, 35 min, 38 min, 40 min, etc.; the stirring and mixing time is 3-8 min, including but not limited to: 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, etc.; the secondary stirring time is 1-5 min, including but not limited to: 1 min, 2 min, 3 min, 4 min, 5 min, etc.; and the standing time is 1.5-2.5 h, including but not limited to: 1.5, 1.75 h, 2 h, 2.25 h, 2.5 h, etc.

[0031] In some embodiments, in step S2-1, the concentration of polyferric sulfate added to the wastewater is 1~3 g / L, including but not limited to: 1 g / L, 1.5 g / L, 2 g / L, 2.5 g / L, 3 g / L, etc.; the mass concentration of the polyacrylamide aqueous solution is 0.5~1.5%, including but not limited to: 0.5%, 0.8%, 1.0%, 1.2%, 1.5%, etc.; the ratio of the volume of polyacrylamide aqueous solution added to the volume of wastewater is 0.5~1 L / m³. 3 Including but not limited to: 0.5L / m 3 0.6L / m 3 0.7L / m 3 0.8L / m 3 0.9L / m 3 1.0L / m 3 wait.

[0032] In some embodiments, in steps S2-2 and S3-2, the obtained sludge is subjected to plate and frame filtration, heavy metal ions are recovered from the filter residue, and the filtrate is returned to the wastewater containing antimony, gallium, and indium in step S1.

[0033] In some embodiments, in steps S2-2 and S3-2, the wastewater from which heavy metals have been removed is discharged directly.

[0034] The process flow diagram of this invention can be seen. Figure 1 For details, please refer to the embodiments.

[0035] Example 1 In this embodiment, the concentrations of Sb in the high-concentration wastewater are 100 mg / L, Ga is 12 mg / L, and In is 6 mg / L. The concentrations of Sb in the low-concentration wastewater are 30 mg / L, Ga is 3 mg / L, and In is 1.5 mg / L.

[0036] High-concentration wastewater treatment tank A: 1-1: High-concentration wastewater was introduced into tank A. Under stirring, Ca(OH)₂ was slowly added to adjust the pH of the wastewater to 7.5. After the addition was complete, the precipitation reaction was allowed to proceed for 20 minutes. Then, PFS (3 g / L concentration in the wastewater) was added and stirred for 5 minutes. Finally, 1 wt% PAM solution was added (the volume ratio of PAM solution to high-concentration wastewater was 0.8 L / m³). 3 Stir slowly for 3 minutes, then let stand for 2 hours.

[0037] 1-2: The supernatant after settling in step 1-1 was tested, and the concentrations of Sb, Ga, and In were measured to be 25 mg / L, 0.5 mg / L, and 0.4 mg / L, respectively. The wastewater after settling was then filtered to obtain sludge enriched with heavy metals and pre-treated wastewater.

[0038] Low-concentration wastewater treatment tank B: 2-1: The pre-treated wastewater and low-concentration wastewater were fed together into tank B (at this point, the Sb concentration in the wastewater was 27.5 mg / L). Under stirring, NaOH was slowly added to adjust the pH of the wastewater to 8.5. After the addition was complete, the precipitation reaction was allowed to proceed for 30 minutes. Then, PFS (PFS concentration in the wastewater was 3 g / L) was added, and after stirring for 5 minutes, 1 wt% PAM solution was added (the volume ratio of PAM solution to high-concentration wastewater was 0.5 L / m³). 3 Stir slowly for 3 minutes, then let stand for 2 hours.

[0039] 2-2: The supernatant after settling in step 1-1 was tested. The concentrations of Sb, Ga, In, and Ca in the supernatant were measured to be 0.2 mg / L, <0.2 mg / L, and 37 mg / L, respectively. The supernatant met the standards. After filtration, sludge enriched with heavy metals and wastewater that met the standards were obtained.

[0040] Metal recovery is performed on the sludge enriched with heavy metals in steps 1-2 and 2-2.

[0041] The qualified wastewater from step 2-2 can be discharged directly.

[0042] Following the procedure in Example 1, 15m³ of high-concentration wastewater was continuously treated. 3 and 15m of low-concentration wastewater 3 Afterwards, the scaling condition of pool A was observed, and the metal recovery rate and treatment cost were calculated. The results are shown in Table 1.

[0043] Example 2 In this embodiment, the concentration of Sb in the high-concentration wastewater is 120 mg / L, the concentration of Ga is 10 mg / L, and the concentration of In is 5 mg / L.

[0044] High-concentration wastewater treatment tank A: 1-1: High-concentration wastewater was introduced into tank A. Under stirring, Ca(OH)₂ was slowly added to adjust the pH of the wastewater to 7.8. After the addition was complete, the precipitation reaction was allowed to proceed for 25 minutes. Then, PFS (PFS concentration in the wastewater was 3.2 g / L) was added, and after stirring for 6 minutes, 1.2 wt% PAM solution was added (the volume ratio of PAM solution to high-concentration wastewater was 0.7 L / m³). 3 Stir slowly for 4 minutes, then let stand for 2 hours.

[0045] 1-2: The supernatant after settling in step 1-1 was tested, and the concentrations of Sb, Ga, and In were measured to be 32 mg / L, 1.5 mg / L, and 0.8 mg / L, respectively. The wastewater after settling was then filtered to obtain sludge enriched with heavy metals and pre-treated wastewater.

[0046] Low-concentration wastewater treatment tank B: 2-1: The pre-treated wastewater is introduced into tank B. Under stirring, NaOH is slowly added to adjust the pH of the wastewater to 8.5. After the addition is complete, the precipitation reaction is allowed to proceed for 25 minutes. Then, PFS (3 g / L concentration in the wastewater) is added and stirred for 5 minutes. Finally, 1 wt% PAM solution is added (the volume ratio of PAM solution to high-concentration wastewater is 0.5 L / m³). 3 Stir slowly for 3 minutes, then let stand for 2 hours.

[0047] 2-2: The supernatant after settling in step 1-1 was tested. The concentrations of Sb, Ga, In, and Ca in the supernatant were measured to be 0.18 mg / L, <0.2 mg / L, and 43 mg / L, respectively. The supernatant met the standards. After filtration, sludge enriched with heavy metals and wastewater that met the standards were obtained.

[0048] The sludge enriched with heavy metals in steps 1-2 and 2-2 will undergo metal recovery. The qualified wastewater in step 2-2 can be directly discharged.

[0049] Following the procedure in Example 2, 30m³ of high-concentration wastewater was continuously treated. 3 Afterwards, the scaling condition of pool A was observed, and the metal recovery rate and treatment cost were calculated. The results are shown in Table 1.

[0050] Comparative Example 1 In this comparative example, the concentration of Sb in the high-concentration wastewater was 120 mg / L, the concentration of Ga was 10 mg / L, and the concentration of In was 5 mg / L.

[0051] High-concentration wastewater treatment tank A: 1-1: High-concentration wastewater was introduced into tank A. Under stirring, Ca(OH)₂ was slowly added to adjust the pH of the wastewater to 7.8. After the addition was complete, the precipitation reaction was allowed to proceed for 25 minutes. Then, PFS (PFS concentration in the wastewater was 3.2 g / L) was added, and after stirring for 6 minutes, 1.2 wt% PAM solution was added (the volume ratio of PAM solution to high-concentration wastewater was 0.7 L / m³). 3 Stir slowly for 4 minutes, then let stand for 2 hours.

[0052] 1-2: The supernatant after settling in step 1-1 was tested. The concentrations of Sb, Ga, and In were measured to be 32 mg / L, 1.5 mg / L, and 0.8 mg / L, respectively. The wastewater was then filtered to obtain sludge enriched with heavy metals and pre-treated wastewater. Since the pre-treated wastewater did not meet the discharge standards, step 1-1 was repeated. The concentrations of Sb, Ga, and In in the supernatant were measured to be 0.21 mg / L, <0.2 mg / L, <0.2 mg / L, and 1536 mg / L, respectively. After filtration, sludge enriched with heavy metals and secondary treated wastewater were obtained. Sodium carbonate (3 times the mass concentration of Ca) was added to the secondary treated wastewater for calcium precipitation. After stirring for 1 hour and settling for 4 hours, the Ca concentration in the supernatant was measured to be 156 mg / L, meeting the discharge standards. Filtration was then performed to obtain precipitated sludge and compliant wastewater.

[0053] The sludge enriched with heavy metals in steps 1-2 undergoes heavy metal recovery, and the qualified wastewater can be directly discharged.

[0054] Following the process of Comparative Example 1, 30m³ of high-concentration wastewater was continuously treated. 3 Afterwards, the scaling condition of pool A was observed, and the metal recovery rate and treatment cost were calculated. The results are shown in Table 1.

[0055] Comparative Example 2 In this comparative example, the concentration of Sb in the high-concentration wastewater was 120 mg / L, the concentration of Ga was 10 mg / L, and the concentration of In was 5 mg / L.

[0056] Wastewater Treatment Pool A: 1-1: High-concentration wastewater was introduced into tank B. Under stirring, NaOH was slowly added to adjust the pH of the wastewater to 8.5. After the addition was complete, the precipitation reaction was allowed to proceed for 25 minutes. Then, PFS (3 g / L concentration in the wastewater) was added, and after stirring for 5 minutes, 1 wt% PAM solution was added (the volume ratio of PAM solution to high-concentration wastewater was 0.5 L / m³). 3 Stir slowly for 3 minutes, then let stand for 2 hours.

[0057] 1-2: The supernatant after settling in step 1-1 was tested. The concentrations of Sb, Ga, and In in the supernatant were measured to be 34 mg / L, 0.9 mg / L, and 0.5 mg / L. After filtration, sludge enriched with heavy metals and pre-treated wastewater were obtained. The pre-treated wastewater did not meet the discharge standards, so step 1-1 was repeated (during the repetition of step 1-1, the pH needed to be adjusted to 8.5 with hydrochloric acid solution). The concentrations of Sb, Ga, and In in the supernatant were measured to be 0.16 mg / L, <0.2 mg / L, and <0.2 mg / L. After filtration, sludge enriched with heavy metals and compliant wastewater were obtained.

[0058] The sludge enriched with heavy metals in steps 1-2 undergoes heavy metal recovery, and the qualified wastewater can be directly discharged.

[0059] Following the process of Comparative Example 2, 30m³ of high-concentration wastewater was continuously treated. 3 The conditions in pool A were observed, and the metal recovery rate and processing cost were calculated. The results are shown in Table 1.

[0060] Example 3 In this embodiment, the concentration of Sb in the high-concentration wastewater is 98 mg / L, the concentration of Ga is 3 mg / L, and the concentration of In is 4 mg / L.

[0061] High-concentration wastewater treatment tank A: 1-1: High-concentration wastewater was introduced into tank A. Under stirring, Ca(OH)₂ was slowly added to adjust the pH of the wastewater to 7.6. After the addition was complete, the precipitation reaction was allowed to proceed for 30 minutes. Then, PFS (PFS concentration in the wastewater was 3.3 g / L) was added, and after stirring for 8 minutes, 1.5 wt% PAM solution was added (the volume ratio of PAM solution to high-concentration wastewater was 0.6 L / m³). 3 Stir slowly for 5 minutes, then let stand for 2.5 hours.

[0062] 1-2: The supernatant after settling in step 1-1 was tested. The concentration of Sb in the supernatant was measured to be 0.28 mg / L, the concentration of Ga was <0.2 mg / L, the concentration of In was <0.2 mg / L, and the concentration of Ca was 1358 mg / L. Sodium carbonate (the concentration of sodium carbonate was 3 times the concentration of Ca) was added to the wastewater and stirred for 1 hour. After settling for 5 hours, the concentration of Ca in the supernatant was measured to be 150 mg / L. After pressure filtration, sludge enriched with heavy metals and wastewater meeting the standards were obtained.

[0063] The sludge enriched with heavy metals in steps 1-2 undergoes heavy metal recovery, and the qualified wastewater can be directly discharged.

[0064] Following the procedure in Example 2, 30m³ of high-concentration wastewater was continuously treated. 3 Then, observe the scaling condition in tank A.

[0065] Example 4 In this embodiment, the concentration of Sb in the high-concentration wastewater is 105 mg / L, the concentration of Ga is 9 mg / L, and the concentration of In is 7 mg / L.

[0066] High-concentration wastewater treatment tank A: 1-1: High-concentration wastewater was introduced into tank A. Under stirring, Ca(OH)₂ was slowly added to adjust the pH of the wastewater to 7.8. After the addition was complete, the precipitation reaction was allowed to proceed for 20 minutes. Then, PFS (PFS concentration in the wastewater was 3 g / L) was added, and after stirring for 3 minutes, 1.0 wt% PAM solution was added (the volume ratio of PAM solution to high-concentration wastewater was 0.9 L / m³). 3 Stir slowly for 5 minutes, then let stand for 1.5 hours.

[0067] 1-2: The supernatant after settling in step 1-1 was tested, and the concentrations of Sb, Ga, and In were measured to be 9 mg / L, 0.8 mg / L, and 0.8 mg / L, respectively. The wastewater after settling was then filtered by pressure to obtain sludge enriched with heavy metals and pre-treated wastewater.

[0068] Low-concentration wastewater treatment tank B: 2-1: The pre-treated wastewater is introduced into tank B. Under stirring, NaOH is slowly added to adjust the pH of the wastewater to 8. After the addition is complete, the precipitation reaction is allowed to proceed for 40 minutes. Then, PFS (1 g / L concentration in the wastewater) is added and stirred for 5 minutes. Finally, 1 wt% PAM solution is added (the volume ratio of PAM solution to high-concentration wastewater is 0.8 L / m³). 3 Stir slowly for 1 minute, then let stand for 2.5 hours.

[0069] 2-2: The supernatant after settling in step 1-1 was tested. The concentrations of Sb, Ga, In, and Ca in the supernatant were measured to be 0.1 mg / L, <0.2 mg / L, <0.2 mg / L, and 25 mg / L, respectively. The supernatant met the standards. After filtration, sludge enriched with heavy metals and wastewater that met the standards were obtained.

[0070] The sludge enriched with heavy metals in steps 1-2 and 2-2 will undergo metal recovery. The qualified wastewater in step 2-2 can be directly discharged.

[0071] Following the procedure in Example 2, 30m³ of high-concentration wastewater was continuously treated. 3 Afterwards, the scaling condition of pool A was observed, and the metal recovery rate and treatment cost were calculated. The results are shown in Table 1.

[0072] Example 5 In this embodiment, the concentration of Sb in the high-concentration wastewater is 65 mg / L, the concentration of Ga is 3 mg / L, and the concentration of In is 2 mg / L.

[0073] High-concentration wastewater treatment tank A: 1-1: High-concentration wastewater was introduced into tank A. Under stirring, Ca(OH)₂ was slowly added to adjust the pH of the wastewater to 7.0. After the addition was complete, the precipitation reaction was allowed to proceed for 30 minutes. Then, PFS (3 g / L concentration in the wastewater) was added and stirred for 3 minutes. Finally, 1.5 wt% PAM solution was added (the volume ratio of PAM solution to high-concentration wastewater was 0.5 L / m³). 3 Stir slowly for 1 minute, then let stand for 2 hours.

[0074] 1-2: The supernatant after settling in step 1-1 was tested, and the concentrations of Sb, Ga, and In were measured to be 14 mg / L, 0.5 mg / L, and 0.6 mg / L, respectively. The wastewater after settling was then filtered by pressure to obtain sludge enriched with heavy metals and pre-treated wastewater.

[0075] Low-concentration wastewater treatment tank B: 2-1: The pre-treated wastewater is introduced into tank B. Under stirring, NaOH is slowly added to adjust the pH of the wastewater to 9. After the addition is complete, the precipitation reaction is allowed to proceed for 20 minutes. Then, PFS (PFS concentration in the wastewater is 2 g / L) is added, and after stirring for 5 minutes, 1.5 wt% PAM solution is added (the volume ratio of PAM solution to high-concentration wastewater is 0.8 L / m³). 3 Stir slowly for 5 minutes, then let stand for 1.5 hours.

[0076] 2-2: The supernatant after settling in step 1-1 was tested. The concentrations of Sb, Ga, In, and Ca in the supernatant were measured to be 0.15 mg / L, <0.2 mg / L, and 36 mg / L, respectively. The supernatant met the standards. After filtration, sludge enriched with heavy metals and wastewater that met the standards were obtained.

[0077] The sludge enriched with heavy metals in steps 1-2 and 2-2 will undergo metal recovery. The qualified wastewater in step 2-2 can be directly discharged.

[0078] Following the procedure in Example 2, 30m³ of high-concentration wastewater was continuously treated. 3 Afterwards, the scaling condition of pool A was observed, and the metal recovery rate and treatment cost were calculated. The results are shown in Table 1.

[0079] Table 1 As can be seen from the data in Table 1, when treating wastewater of the same concentration, Example 2 exhibits a significantly higher metal recovery rate than Comparative Examples 1 and 2. Although the wastewater treatment cost in Example 2 is slightly higher than that in Comparative Example 1, it does not result in severe scaling or clogging and is significantly lower than the cost in Comparative Example 1. Example 1 can treat wastewater of different concentrations simultaneously, offering greater flexibility and lower costs. In Examples 3-5, process parameters were adjusted based on the differences in metal concentration in the wastewater, resulting in consistently high metal recovery rates, minimal scaling, and lower costs.

[0080] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for graded treatment of wastewater containing heavy metals such as antimony, gallium, and indium, characterized in that, Includes the following steps: S1: Antimony, gallium and indium in heavy metal wastewater containing antimony, gallium and indium are detected. When the Sb content in the wastewater containing antimony, gallium and indium is >50mg / L and / or the total content of Ga and In is >10mg / L, it enters the first gradient treatment process. S2: The first gradient processing technology is: S2-1: Add Ca(OH)2 to the wastewater containing antimony, gallium and indium heavy metals, control the pH of the wastewater to 7.0~8.0, stir to carry out precipitation reaction, after the reaction is completed, add polyferric sulfate, stir to mix well, then add polyacrylamide aqueous solution, stir a second time, and let stand. S2-2: Take the supernatant after settling and test it: ① When Sb < 0.3 mg / L and the total content of Ga and In < 1 mg / L in the supernatant, add sodium carbonate to the wastewater for calcium precipitation. After calcium precipitation, the wastewater is filtered by pressure to obtain sludge and wastewater with heavy metals removed; ② When the content of Sb in the supernatant is 0.3 mg / L ≤ 50 mg / L and / or the total content of Ga and In is 1 mg / L ≤ 10 mg / L, filter to obtain sludge and wastewater. The wastewater enters the second gradient treatment process; ③ When the content of Sb in the supernatant is > 50 mg / L and / or the total content of Ga and In is > 10 mg / L, repeat step S2-1 until it meets ① or ②, and proceed to the next step accordingly; S3: The second gradient processing technology is: S3-1: Add NaOH or HCl to the wastewater to control the pH of the wastewater to 8-9, stir to carry out the precipitation reaction, after the reaction is completed, add polyferric sulfate, stir to mix well, then add polyacrylamide aqueous solution, stir a second time, and let stand. S3-2: Take the supernatant after settling and test it: ① When Sb in the supernatant is <0.3mg / L and the total content of Ga and In is <1mg / L, filter it to obtain sludge and wastewater with heavy metals removed; ② When Sb in the supernatant is ≥0.3mg / L and / or the total content of Ga and In is ≥1mg / L, repeat step S3-1 until it meets ①, and proceed to the next step.

2. The method for graded treatment of wastewater containing antimony, gallium, and indium heavy metals according to claim 1, characterized in that, In step S1, when the Sb content in the wastewater containing antimony, gallium, and indium is ≤50mg / L and the total Ga and In content is ≤10mg / L, it enters the second gradient treatment process.

3. The method for graded treatment of wastewater containing antimony, gallium, and indium heavy metals according to claim 1, characterized in that, In step S2-1, the precipitation reaction time is 15-30 min; the stirring and mixing time is 3-8 min; the secondary stirring time is 1-5 min; and the standing time is 1.5-2.5 h.

4. The method for graded treatment of wastewater containing antimony, gallium, and indium heavy metals according to claim 1 or 3, characterized in that, In step S2-1, the concentration of polyferric sulfate added to the wastewater is 3~3.5 g / L.

5. The graded treatment method for wastewater containing antimony, gallium, and indium heavy metals according to claim 1 or 3, characterized in that, In step S2-1, the mass concentration of the polyacrylamide aqueous solution is 0.5~1.5%, and the volume ratio of the added polyacrylamide aqueous solution to the wastewater is 0.5~1 L / m³. 3 .

6. The method for graded treatment of wastewater containing antimony, gallium, and indium heavy metals according to claim 1, characterized in that, In step S2-2, the specific steps for adding sodium carbonate to the wastewater for calcium precipitation are as follows: Based on the Ca concentration in the supernatant, sodium carbonate is added at a mass concentration of 2 to 4 times that of Ca. After stirring and reacting for 0.5 to 1.5 hours, the mixture is allowed to stand for 3 to 5 hours. The Ca concentration in the supernatant is then measured. ① If the Ca concentration is <200 mg / L, the process proceeds to the pressure filtration step. ② If the Ca concentration is ≥200 mg / L, the calcium precipitation step is repeated until the Ca concentration is <200 mg / L.

7. The method for graded treatment of wastewater containing antimony, gallium, and indium heavy metals according to claim 1, characterized in that, In step S3-1, the precipitation reaction time is 20-40 min; the stirring and mixing time is 3-8 min; the secondary stirring time is 1-5 min; and the standing time is 1.5-2.5 h.

8. The method for graded treatment of wastewater containing antimony, gallium, and indium heavy metals according to claim 1 or 7, characterized in that, In step S3-1, the concentration of polyferric sulfate added to the wastewater is 1~3 g / L; the mass concentration of the polyacrylamide aqueous solution is 0.5~1.5%, and the volume ratio of the polyacrylamide aqueous solution added to the wastewater is 0.5~1 L / m³. 3 .

9. The method for graded treatment of wastewater containing antimony, gallium, and indium heavy metals according to claim 1, characterized in that, In steps S2-2 and S3-2, the obtained sludge is subjected to plate and frame filtration, heavy metal ions are recovered from the filter residue, and the filtrate is returned to the wastewater containing antimony, gallium, and indium in step S1.

10. The method for graded treatment of wastewater containing antimony, gallium, and indium heavy metals according to claim 1 or 9, characterized in that, In steps S2-2 and S3-2, the wastewater from which heavy metals have been removed is discharged directly.

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