Co-treatment method for lithium smelting slag and tungsten smelting wastewater with high fluorine, phosphorus and arsenic content

Abstract

This invention belongs to the field of industrial wastewater treatment and industrial solid waste resource utilization technology, specifically a method for the co-treatment of lithium smelting slag and tungsten smelting wastewater with high fluoride, phosphorus, and arsenic content. The method includes the following steps: S1, mixing lithium smelting slag with dilute acid, followed by stirring, filtration, washing, drying, and grinding to obtain activated slag; S2, mixing the activated slag with dilute alkali, followed by hydrothermal reaction, filtration, washing, and drying to obtain modified slag; S3, adding the modified slag to the acid-adjusted tungsten smelting wastewater, followed by stirring and filtration to obtain fluoride, phosphorus, and arsenic-free wastewater. This invention innovatively transforms lithium smelting slag into a highly efficient adsorption-precipitation material through "acid activation-alkali modification," solving the environmental risks of lithium slag stockpiling and realizing the high-value utilization of lithium slag into environmentally friendly materials, while avoiding the secondary pollution problems caused by the use of chemical agents in traditional processes.

Description

Technical Field

[0001] This invention belongs to the field of industrial wastewater treatment and industrial solid waste resource utilization technology, specifically a method for the synergistic treatment of lithium smelting slag and tungsten smelting wastewater with high fluorine, phosphorus and arsenic content. Background Technology

[0002] Tungsten smelting is a crucial foundational industry within the tungsten sector, playing a key role in converting the effective components (Fe, Mn, Ca)WO4 in tungsten ore into (Na, NH4)2WO4 solution, thereby producing ammonium paratungstate (APT). However, with the continuous depletion of high-quality tungsten ore resources, complex tungsten ores such as high-fluorite (CaF2), apatite (Ca5(PO4)3(F, OH)), and arsenopyrite (FeAsS) have gradually become smelting raw materials in recent years, resulting in tungsten smelting wastewater with high levels of fluorine, phosphorus, and arsenic. According to incomplete statistics, the wastewater generated by smelting complex and difficult-to-treat tungsten ores using the current mainstream alkaline pressure leaching-ion exchange process reaches 120-150 m³ / h. 3 / tAPT.

[0003] Existing technologies disclose methods for treating tungsten smelting wastewater, including: (1) mixing tungsten smelting wastewater with a phosphorus and arsenic removal agent and filtering it to obtain phosphorus and arsenic removal wastewater; (2) mixing the phosphorus and arsenic removal wastewater with a defluorinating agent and a flocculant in sequence and filtering it to obtain defluorinated slag and defluorinated wastewater; (3) mixing the defluorinated slag with an acid solution and distilling it to obtain a gas containing HF and a residual liquid containing the defluorinating agent. This method can effectively remove phosphorus, arsenic, and fluorine from wastewater, but it has the problem of complex reagent usage, requiring the sequential use of multiple reagents such as phosphorus and arsenic removal agents (CaCl2 and Ca(OH)2), defluorinating agent LaCl3, and flocculant polyacrylamide (PAM). At the same time, the system pH value requirement is high; the pH value of the wastewater needs to be controlled at around 12 when removing phosphorus and arsenic, while the pH value of the wastewater needs to be around 7 when removing fluorine, and the arsenic removal effect is not mentioned in the examples. Therefore, this existing technology has problems such as complex process, inconvenient operation, and unclear arsenic removal effect.

[0004] Existing technologies also disclose methods for purifying tungsten smelting wastewater using alkali decomposition slag as raw material. The purification mechanism is "calcium-based precipitation (fluoride removal) + Fe / Mn single-component precipitation (phosphorus and arsenic removal)". This utilizes the calcium, iron, and manganese components in the slag, namely calcium hydroxyphosphate (Ca5(PO4)3OH) and Fe(OH)3 / MnO2, to react with F, P, and As(V) respectively for precipitation removal. However, this technology cannot treat As(III) in the wastewater (trivalent arsenic accounts for 30-60% in tungsten smelting wastewater), and is also affected by the Cl often present in the wastewater. - SO4 2-The current technology is highly susceptible to interference, resulting in unstable purification effects. Furthermore, it treats low-concentration acidic wastewater from tungsten smelting (pH 3.42, F concentration 73.88 ppm, P concentration 9.040 ppm, As concentration 7.729 ppm), while the actual production wastewater from current tungsten smelting enterprises is alkaline, and due to the influence of complex tungsten ore raw materials, the concentrations of F, P, and As in the wastewater are as high as 200 mg / L, 100 mg / L, and 50 mg / L, respectively. Therefore, the purification of alkaline wastewater from high-fluoride, phosphorus, arsenic, and tungsten smelting requires further in-depth research. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for the synergistic treatment of lithium smelting slag and tungsten smelting wastewater with high fluorine, phosphorus, and arsenic content, comprising the following steps:

[0006] S1. Lithium smelting slag is mixed with dilute acid, and then stirred, filtered, washed, dried and ground to obtain activated slag;

[0007] S2. The activated slag is mixed with dilute alkali, and the mixture is subjected to hydrothermal reaction, filtration, water washing, and drying to obtain the modified slag.

[0008] S3. Add the modified slag to the acidified tungsten smelting wastewater, and after stirring and filtration, obtain fluoride, phosphorus and arsenic-free wastewater.

[0009] Preferably, in step S1, the grinding specifically involves grinding until the particles are less than or equal to 100 mesh.

[0010] In step S1, the lithium smelting slag is the waste residue generated by the acid process for lithium extraction from spodumene ore, containing 21wt%~43wt% Al2O3, 32wt%~58wt% SiO2, 8wt%~14wt% CaO, and 5wt%~9wt% Fe2O3.

[0011] Specifically, step S1 involves mixing lithium smelting slag with dilute acid at a liquid-to-solid ratio of (20~50) mL:1g, wherein the hydrogen ion concentration of the dilute acid is 1.3~4.2 mol / L.

[0012] Preferably, lithium smelting slag and dilute acid are mixed at a liquid-to-solid ratio of (30~40) mL:1g, wherein the hydrogen ion concentration of the dilute acid is 1.6~2.8mol / L.

[0013] In step S1, the stirring time is 1 to 3.5 hours, the washing is repeated with deionized water until the pH of the washing water is 6 to 7, and the drying temperature is 60 to 80°C for 2 to 3 hours.

[0014] Preferably, the stirring time is 1.5 to 2.5 hours.

[0015] Specifically, step S2 involves mixing the activated residue with dilute alkali at a liquid-to-solid ratio of (25~55) mL:1g, wherein the hydroxide concentration of the dilute alkali is 0.5~3mol / L.

[0016] Preferably, the activated residue and dilute alkali are mixed at a liquid-to-solid ratio of (35~45) mL:1g, and the hydroxide concentration of the dilute alkali is 1~2mol / L.

[0017] In step S2, the stirring speed of the hydrothermal reaction is 100-200 rpm, the temperature is 120-180℃, and the time is 3-7 h. The water washing is repeated with deionized water until the pH of the washing water is 7-8. The drying temperature is 60-80℃ and the time is 4-6 h.

[0018] Preferably, the stirring speed of the hydrothermal reaction is 120~150 rpm, the temperature is 140~160℃, and the time is 4~5 h.

[0019] The tungsten smelting wastewater is an alkaline wastewater produced by alkaline decomposition ion exchange smelting process of wolframite, scheelite, or a mixture of wolframite and scheelite. Its pH value is 9-14, the concentration of fluorine is 10-200 mg / L, the concentration of phosphorus is 0.5-100 mg / L, and the concentration of arsenic is 0.5-50 mg / L.

[0020] In step S3, the acid-adjusted tungsten smelting wastewater is obtained by adjusting the pH of the tungsten smelting wastewater to 5-7 using hydrochloric acid, and the stirring time is 30-60 minutes.

[0021] The liquid-to-solid ratio of the acid-adjusted tungsten smelting wastewater to the modified slag is 1L:(10~40)g.

[0022] Preferably, the liquid-to-solid ratio of the acidified tungsten smelting wastewater to the modified slag is 1L:(20~30)g.

[0023] In step S3, the concentration of fluoride in the fluoride-removing, phosphorus-removing, and arsenic-removing wastewater is ≤10 mg / L, the concentration of phosphorus is ≤0.5 mg / L, and the concentration of arsenic is ≤0.5 mg / L.

[0024] This invention uses lithium smelting slag as the treatment material and employs a combined synergistic mechanism of "adsorption-precipitation-retention" to simultaneously and efficiently remove fluorine, phosphorus, and arsenic from tungsten smelting wastewater. Compared with existing processes, it has the following advantages:

[0025] By treating waste with waste and realizing the high-value utilization of industrial solid waste, this invention innovatively transforms lithium smelting slag into a highly efficient adsorption-precipitation material through "acid activation-alkali modification". This not only solves the environmental risks of lithium slag stockpiling, but also realizes the high-value utilization of lithium slag, while avoiding the secondary pollution problems caused by the use of chemical agents in traditional processes.

[0026] This invention utilizes the synergistic effect of Al-OH, Fe-OH, and Si-OH in modified lithium slag to simultaneously remove fluorine, phosphorus, and arsenic in the same reaction system, simplifying the treatment process from multiple independent units to a single process and greatly reducing equipment investment.

[0027] This invention features a composite "adsorption-precipitation-retention" mechanism: First, fluorine, phosphorus, and arsenic are fixed in the Al-F and Fe-P / As chemical bonds on the slag surface, preventing their re-release; second, the generated AlPO4, FeAsO4, and other sparingly soluble salts exhibit stability far exceeding that of traditional precipitation products; and third, the porous structure of the silica-alumina framework on the slag surface firmly fixes the precipitates and free pollutants within the pores through physical adsorption, preventing secondary pollution.

[0028] This invention adjusts the pH of tungsten smelting wastewater to 5-7 through pretreatment, allowing the modified slag to react efficiently within this range. This significantly improves the slag's tolerance to water quality fluctuations. Furthermore, the modified slag can be regenerated using NaOH solution after saturation, achieving a high regeneration rate and lower regeneration costs compared to traditional adsorbents. Considering the costs of reagents, energy consumption, and labor, the cost per ton of water treated is significantly lower than that of traditional stepwise treatment processes, resulting in substantial economic and environmental benefits. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0030] Figure 1 This is a schematic diagram of the process flow of the present invention;

[0031] Figure 2 This is a SEM image of lithium smelting slag after activation with dilute acid.

[0032] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0033] The technical solutions described below in conjunction with the embodiments will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] Please see Figure 1 , Figure 1 This is a schematic diagram of the process flow of the present invention; the present invention provides a method for the co-treatment of lithium smelting slag and tungsten smelting wastewater with high fluorine, phosphorus and arsenic content, comprising the following steps:

[0035] S1. Lithium smelting slag is mixed with dilute acid, and then stirred, filtered, washed, dried and ground to obtain activated slag;

[0036] This invention first activates lithium smelting slag, which is the waste residue produced after lithium extraction from spodumene ore. Its main components are aluminosilicates, including 21wt%~43wt% Al2O3, 32wt%~58wt% SiO2, 8wt%~14wt% CaO, and 5wt%~9wt% Fe2O3. After mixing with dilute acid, the active Al2O3, CaO, and Fe2O3 are dissolved and detached, leaving the original filled voids. However, the stable aluminosilicates and SiO2 remain, forming a continuous rigid framework that supports the pores created after dissolution. Therefore, after activation with dilute acid, a porous structure with a silica-alumina framework is formed on the surface of the lithium smelting slag, as shown in the following equation:

[0037] Al₂O₃ + 6H₂O + =2Al 3+ +3H2O

[0038] Fe2O3+6H + =2Fe 3+ +3H2O

[0039] CaO + 2H+ + =Ca 2+ +H2O

[0040] Please see Figure 2 , Figure 2 This is a SEM image of lithium smelting slag after activation with dilute acid.

[0041] S2. The activated slag is mixed with dilute alkali, and the mixture is subjected to hydrothermal reaction, filtration, water washing, and drying to obtain the modified slag.

[0042] In the lithium smelting slag activated with dilute acid, silicon, aluminum, and iron exist in an active state. They react with dilute alkali to generate corresponding aluminates, silicates, and ferrates, as shown in the following equations:

[0043] Al₂O₃ + 2NaOH = 2NaAlO₂ + H₂O

[0044] SiO₂ + 2NaOH = Na₂SiO₃ + H₂O

[0045] Fe₂O₃ + 2NaOH = 2NaFeO₂ + H₂O

[0046] Furthermore, aluminates, silicates, and ferrates undergo hydrolysis to produce aluminum hydroxide, silicic acid, and ferric hydroxide, as shown in the following equations:

[0047] NaAlO2 + 2H2O Al(OH)3↓+NaOH

[0048] Na₂SiO₃ + 2H₂O H₂SiO₃↓ + 2NaOH

[0049] NaFeO2 + 2H2O Fe(OH)3↓+NaOH

[0050] Under hydrothermal conditions, Al(OH)3 undergoes reconstruction on the surface of the silica-alumina framework of lithium smelting slag, and the adsorbed Al on its surface... 3+ It reacts with water molecules to eventually form stable Al-OH groups. Similarly, H2SiO3 attaches to the surface of the silicon-aluminum framework of lithium smelting slag through hydrogen bonds or chemical bonds, undergoes dehydration and reconstruction, and eventually forms stable Si-OH groups. Fe(OH)3 undergoes surface hydroxylation and reconstruction to form stable Fe-OH groups on the slag surface. The equations are as follows:

[0051]

[0052]

[0053]

[0054] S3. Add the modified slag to the acidified tungsten smelting wastewater, and after stirring and filtration, obtain fluoride, phosphorus and arsenic-free wastewater.

[0055] OH groups on the surface of aluminum hydroxyl groups (Al-OH) - Will with F - An exchange occurs, forming stable Al-F bonds, which bind to Na within the slag pores. + (From dilute alkali) further forms sparingly soluble salts, thereby removing fluoride from the wastewater. Simultaneously, aluminum hydroxyl groups (Al-OH) release Al... 3+ PO4 3- The phosphorus combines with the form of insoluble AlPO4 precipitate, thereby removing phosphorus from the wastewater. The equation is as follows:

[0056] Surface -Al-OH+F - →Surface-Al-F+OH -

[0057] Surface -Al-F+Na + →Na3AlF6↓+Surface-Al-OH

[0058] Surface -Al-OH+PO4 3- +2H + →AlPO4↓ + surface-OH + H2O

[0059] Ferrous hydroxyl radicals (Fe-OH) can catalytically oxidize As(III) (As(III) is the main form of arsenic in tungsten smelting wastewater, accounting for 30wt%~60wt%) to As(V), which then precipitates, thus successfully removing As(III) and As(V) from the wastewater; simultaneously, Fe-OH releases Fe... 3+ PO4 3- This combination forms a sparingly soluble FePO4 precipitate, which can also remove phosphorus from wastewater. The equation is as follows:

[0060] Surface-Fe(III)-OH + As(III) → Surface-Fe(II)-OH + As(V) + H +

[0061] Surface-Fe(Ⅲ)-OH+AsO4 3- →FeAsO4↓+surface-OH+H2O

[0062] Surface -Fe(Ⅲ)-OH+PO4 3- →FePO4↓ + surface-OH + H2O

[0063] Silyl hydroxyl groups (Si-OH) can capture free F through hydrogen bonding. - The equation is as follows:

[0064] Surface -Si-OH+F - Surface-Si-OH…F -

[0065] The simultaneous removal of fluoride, phosphorus, and arsenic from tungsten smelting wastewater by lithium smelting slag utilizes a complex synergistic mechanism of "adsorption-precipitation-retention": three hydroxyl groups (Al-OH, Si-OH, Fe-OH) initiate a reaction through chemisorption, then fix the pollutants through precipitation, and finally achieve retention by relying on the porous structure of the slag's silica-alumina framework, forming a closed loop of "reaction-fixation-separation"; among them, the removal of fluoride is primarily achieved through chemisorption (F... - The process primarily involves replacing the -OH ligand in Al-OH to form stable Al-F chemical bonds, with precipitation (Na3AlF6) as a secondary process, and adsorption of free F by Si-OH through hydrogen bonding.- The removal of phosphorus and arsenic is mainly achieved through precipitation (AlPO4, FeAsO4, FePO4), supplemented by adsorption (the precipitates adhere to the porous surface of the modified slag through physical adsorption) and retention (the silica-alumina skeleton of the slag has a strong retention capacity), which firmly fixes the precipitates in the pores, resulting in a stable removal effect.

[0066] Example 1

[0067] Lithium smelting slag was mixed with 2.8 mol / L dilute hydrochloric acid at a liquid-solid ratio of 30 mL: 1 g, stirred at room temperature for 2 h, filtered, and the filter residue was washed with deionized water until the pH of the wash water was 6.3. The washed filter residue was placed in a drying oven and dried at 80 °C for 2 h, and then ground to obtain activated slag.

[0068] The activated residue was mixed with 2 mol / L NaOH solution at a liquid-to-solid ratio of 40 mL: 1 g and subjected to a hydrothermal reaction at a temperature of 150 °C for 5 h with a stirring speed of 150 rpm. After the reaction was completed, the residue was filtered and washed with deionized water until the pH of the wash water was 7.8. The washed residue was then placed in an oven and dried at 70 °C for 6 h to obtain the modified residue.

[0069] 1L of tungsten smelting wastewater was obtained. The pH of the tungsten smelting wastewater was 12, the concentration of fluorine was 100mg / L, the concentration of phosphorus was 50mg / L, and the concentration of arsenic was 20mg / L. The pH of the tungsten smelting wastewater was adjusted to 6 using hydrochloric acid to obtain the acidified wastewater.

[0070] The acidified wastewater and modified slag were mixed at a liquid-to-solid ratio of 1L:25g and stirred at room temperature for 60 minutes. The mixture was then filtered to obtain fluoride, phosphorus and arsenic-removed wastewater. The concentration of fluoride, phosphorus and arsenic-removed wastewater was tested and found to be 5.74 mg / L, 0.34 mg / L, and 0.26 mg / L.

[0071] Example 2

[0072] Lithium smelting slag was mixed with 4.2 mol / L dilute hydrochloric acid at a liquid-solid ratio of 25 mL: 1 g, stirred at room temperature for 1.5 h, filtered, and the filter residue was washed with deionized water until the pH of the wash water was 6. The washed filter residue was placed in a drying oven and dried at 60 °C for 3 h, and then ground to obtain activated slag.

[0073] The activated residue was mixed with 1 mol / L NaOH solution at a liquid-to-solid ratio of 35 mL: 1 g and subjected to a hydrothermal reaction at a temperature of 140 °C for 4 h with a stirring speed of 180 rpm. After the reaction was completed, the residue was filtered and washed with deionized water until the pH of the wash water was 7.2. The washed residue was then placed in an oven and dried at 80 °C for 4 h to obtain the modified residue.

[0074] 1L of tungsten smelting wastewater was obtained. The pH of the tungsten smelting wastewater was 14, the concentration of fluorine was 120mg / L, the concentration of phosphorus was 80mg / L, and the concentration of arsenic was 30mg / L. The pH of the tungsten smelting wastewater was adjusted to 5 with hydrochloric acid to obtain the acidified wastewater.

[0075] The acidified wastewater and modified slag were mixed at a liquid-solid ratio of 1L:30g and stirred at room temperature for 30 minutes. The mixture was then filtered to obtain fluoride, phosphorus and arsenic-removed wastewater. The concentration of fluoride, phosphorus and arsenic-removed wastewater was tested and found to be 6.09 mg / L, 0.27 mg / L, and 0.40 mg / L.

[0076] Example 3

[0077] Lithium smelting slag was mixed with 1.3 mol / L dilute hydrochloric acid at a liquid-solid ratio of 40 mL: 1 g, stirred at room temperature for 2.5 h, filtered, and the filter residue was washed with deionized water until the pH of the wash water was 7. The washed filter residue was placed in a drying oven and dried at 70 °C for 2.5 h, and then ground to obtain activated slag.

[0078] The activated residue was mixed with 1.5 mol / L NaOH solution at a liquid-to-solid ratio of 45 mL: 1 g and subjected to a hydrothermal reaction at a temperature of 160 °C for 4 h with a stirring speed of 140 rpm. After the reaction was completed, the residue was filtered and washed with deionized water until the pH of the wash water was 7.6. The washed residue was then placed in an oven and dried at 70 °C for 5 h to obtain the modified residue.

[0079] 1L of tungsten smelting wastewater was obtained. The pH of the tungsten smelting wastewater was 10, the concentration of fluorine was 50mg / L, the concentration of phosphorus was 30mg / L, and the concentration of arsenic was 20mg / L. The pH of the tungsten smelting wastewater was adjusted to 7 using hydrochloric acid to obtain the acidified wastewater.

[0080] The acidified wastewater and modified slag were mixed at a liquid-to-solid ratio of 1L:20g and stirred at room temperature for 40 minutes. The mixture was then filtered to obtain fluoride, phosphorus and arsenic-removed wastewater. The concentration of fluoride, phosphorus and arsenic-removed wastewater was tested and found to be 7.33 mg / L, 0.39 mg / L, and 0.25 mg / L.

[0081] Example 4

[0082] Lithium smelting slag was mixed with 2.8 mol / L dilute hydrochloric acid at a liquid-solid ratio of 25 mL: 1 g, stirred at room temperature for 3.5 h, filtered, and the filter residue was washed with deionized water until the pH of the wash water was 6.1. The washed filter residue was placed in a drying oven and dried at 60 °C for 3 h, and then ground to obtain activated slag.

[0083] The activated residue was mixed with 0.5 mol / L NaOH solution at a liquid-solid ratio of 45 mL: 1 g and subjected to a hydrothermal reaction at a temperature of 160 °C for 6 h with a stirring speed of 150 rpm. After the reaction was completed, the residue was filtered and washed with deionized water until the pH of the wash water was 8. The washed residue was then placed in an oven and dried at 80 °C for 4 h to obtain the modified residue.

[0084] 1L of tungsten smelting wastewater was obtained. The pH of the tungsten smelting wastewater was 11, the concentration of fluorine was 160mg / L, the concentration of phosphorus was 60mg / L, and the concentration of arsenic was 50mg / L. The pH of the tungsten smelting wastewater was adjusted to 6.5 with hydrochloric acid to obtain the acidified wastewater.

[0085] The acidified wastewater and modified slag were mixed at a liquid-to-solid ratio of 1L:40g and stirred at room temperature for 50 minutes. The mixture was then filtered to obtain fluoride, phosphorus and arsenic-removed wastewater. The concentration of fluoride, phosphorus and arsenic-removed wastewater was tested and found to be 8.10 mg / L, 0.32 mg / L, and 0.26 mg / L.

[0086] Comparative Example 1

[0087] The difference from Example 1 is that the activated residue is not washed with deionized water;

[0088] The wastewater was tested for fluoride, phosphorus, and arsenic removal. The concentrations of fluoride, phosphorus, and arsenic were 34.59 mg / L, 7.88 mg / L, and 2.53 mg / L, respectively.

[0089] Comparative Example 2

[0090] The difference from Example 1 is that the modified residue is not washed with deionized water;

[0091] The wastewater was tested for fluoride, phosphorus, and arsenic removal. The concentrations of fluoride, phosphorus, and arsenic were 27.46 mg / L, phosphorus, and arsenic, respectively.

[0092] Comparative Example 3

[0093] The difference from Example 1 is that the tungsten smelting wastewater is not acidified;

[0094] The wastewater was tested for fluoride, phosphorus, and arsenic removal. The concentrations of fluoride, phosphorus, and arsenic were 50.41 mg / L, phosphorus, and arsenic, respectively.

[0095] Comparative Example 4

[0096] The difference from Example 1 is that the lithium smelting slag and dilute acid were mixed at a liquid-to-solid ratio of 60 mL: 1 g.

[0097] The wastewater was tested for fluoride, phosphorus, and arsenic removal. The concentration of fluoride was 44.10 mg / L, the concentration of phosphorus was 28.53 mg / L, and the concentration of arsenic was 7.28 mg / L.

[0098] Comparative Example 5

[0099] The difference from Example 1 is that lithium smelting slag and dilute hydrochloric acid were mixed at a liquid-to-solid ratio of 15 mL: 1 g.

[0100] The wastewater was tested for fluoride, phosphorus, and arsenic removal. The concentrations of fluoride, phosphorus, and arsenic were 31.09 mg / L, phosphorus, and arsenic, respectively.

[0101] Comparative Example 6

[0102] The difference from Example 1 is that the activation residue and NaOH solution were mixed at a liquid-to-solid ratio of 15 mL: 1 g.

[0103] The wastewater was tested for fluoride, phosphorus, and arsenic removal. The concentrations of fluoride, phosphorus, and arsenic were 35.12 mg / L, phosphorus, and arsenic, respectively.

[0104] Comparative Example 7

[0105] The difference from Example 1 is that the activation residue and NaOH solution were mixed at a liquid-to-solid ratio of 60 mL: 1 g;

[0106] The wastewater was tested for fluoride, phosphorus, and arsenic removal. The concentrations of fluoride, phosphorus, and arsenic were 47.13 mg / L, phosphorus, and arsenic, respectively.

[0107] Comparative Example 8

[0108] The difference from Example 1 is that the hydrothermal reaction temperature is 100°C;

[0109] The wastewater was tested for fluoride, phosphorus, and arsenic removal. The concentrations of fluoride, phosphorus, and arsenic were 31.07 mg / L, phosphorus, and arsenic, respectively.

[0110] Comparative Example 9

[0111] The difference from Example 1 is that the hydrothermal reaction temperature is 200°C;

[0112] The wastewater was tested for fluoride, phosphorus, and arsenic removal. The concentrations of fluoride, phosphorus, and arsenic were 45.31 mg / L, phosphorus, and arsenic, respectively.

[0113] Comparative Example 10

[0114] The difference from Example 1 is that the acidified wastewater and modified slag are mixed at a liquid-to-solid ratio of 1L:5g.

[0115] The wastewater was tested for fluoride, phosphorus, and arsenic removal. The concentration of fluoride was 40.33 mg / L, the concentration of phosphorus was 25.07 mg / L, and the concentration of arsenic was 6.90 mg / L.

[0116] Comparative Example 11

[0117] The difference from Example 1 is that the acidified wastewater and modified slag are mixed at a liquid-to-solid ratio of 1L:50g.

[0118] The wastewater was tested for fluoride, phosphorus, and arsenic removal. The concentrations of fluoride, phosphorus, and arsenic were 7.55 mg / L, 0.84 mg / L, and 0.63 mg / L, respectively.

[0119] In Examples 1-4, the concentrations of fluorine, phosphorus, and arsenic in the post-reaction tungsten smelting wastewater were all below 10 mg / L, below 0.5 mg / L, and below 0.5 mg / L, respectively. However, in Comparative Example 1, where the acidified slag was not washed, the concentrations of fluorine, phosphorus, and arsenic in the post-reaction wastewater were all higher than the wastewater discharge standards. This is because the unwashed activated slag contains soluble salts, which clog active sites, leading to a decrease in hydroxyl group formation. In Comparative Example 2, where the modified slag was not washed, the residual strongly alkaline environment caused Al-OH and Fe-OH to dissolve, resulting in a decrease in the removal efficiency of fluorine, phosphorus, and arsenic in the wastewater. The degradation was observed in Comparative Example 3, where the alkaline tungsten smelting wastewater was not acidified. Under alkaline conditions, the Al-OH in the modified slag was deactivated, the catalytic activity of Fe-OH decreased, and the hydrogen bonds of Si-OH were destroyed. At the same time, the porous silica-alumina framework collapsed due to the influence of excessive OH-, resulting in a reduced retention rate of precipitates. This demonstrates that the washing of activated slag, the washing of modified slag, and the acidification of tungsten smelting wastewater are crucial for the stable formation of Al-OH, Fe-OH, and Si-OH and their effectiveness in the "adsorption-precipitation-retention" composite mechanism, thereby directly determining the deep removal effect of fluorine, phosphorus, and arsenic in tungsten smelting wastewater.

[0120] This invention uses lithium smelting slag as the treatment material and employs a combined synergistic mechanism of "adsorption-precipitation-retention" to simultaneously and efficiently remove fluorine, phosphorus, and arsenic from tungsten smelting wastewater. Compared with existing processes, it has the following advantages:

[0121] By treating waste with waste and realizing the high-value utilization of industrial solid waste, this invention innovatively transforms lithium smelting slag into a highly efficient adsorption-precipitation material through "acid activation-alkali modification". This not only solves the environmental risks of lithium slag stockpiling, but also realizes the high-value utilization of lithium slag, while avoiding the secondary pollution problems caused by the use of chemical agents in traditional processes.

[0122] This invention utilizes the synergistic effect of Al-OH, Fe-OH, and Si-OH in modified lithium slag to simultaneously remove fluorine, phosphorus, and arsenic in the same reaction system, simplifying the treatment process from multiple independent units to a single process and greatly reducing equipment investment.

[0123] This invention features a composite "adsorption-precipitation-retention" mechanism: First, fluorine, phosphorus, and arsenic are fixed in the Al-F and Fe-P / As chemical bonds on the slag surface, preventing their re-release; second, the generated AlPO4, FeAsO4, and other sparingly soluble salts exhibit stability far exceeding that of traditional precipitation products; and third, the porous structure of the silica-alumina framework on the slag surface firmly fixes the precipitates and free pollutants within the pores through physical adsorption, preventing secondary pollution.

[0124] This invention adjusts the pH of tungsten smelting wastewater to 5-7 through pretreatment, allowing the modified slag to react efficiently within this range. This significantly improves the slag's tolerance to water quality fluctuations. Furthermore, the modified slag can be regenerated using NaOH solution after saturation, achieving a high regeneration rate and lower regeneration costs compared to traditional adsorbents. Considering the costs of reagents, energy consumption, and labor, the cost per ton of water treated is significantly lower than that of traditional stepwise treatment processes, resulting in substantial economic and environmental benefits.

[0125] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for the co-treatment of lithium smelting slag and tungsten smelting wastewater with high fluorine, phosphorus, and arsenic content, characterized in that, Includes the following steps: S1. Lithium smelting slag is mixed with dilute acid, and then stirred, filtered, washed, dried and ground to obtain activated slag; S2. The activated slag is mixed with dilute alkali, and then subjected to hydrothermal reaction, filtration, water washing, and drying to obtain modified slag; S3. Add the modified slag to the acidified tungsten smelting wastewater, and after stirring and filtration, obtain fluoride, phosphorus and arsenic-free wastewater; In step S1, the lithium smelting slag is the waste residue generated by the acid process for lithium extraction from spodumene ore, containing 21wt%~43wt% Al2O3, 32wt%~58wt% SiO2, 8wt%~14wt% CaO, and 5wt%~9wt% Fe2O3. Specifically, step S1 involves mixing lithium smelting slag with dilute acid at a liquid-to-solid ratio of (20~50) mL:1g, wherein the hydrogen ion concentration of the dilute acid is 1.3~4.2 mol / L. Specifically, step S2 involves mixing the activated residue with dilute alkali at a liquid-to-solid ratio of (25~55) mL:1g, wherein the hydroxide concentration of the dilute alkali is 0.5~3mol / L. In step S3, the acid-adjusted tungsten smelting wastewater is obtained by adjusting the pH of the tungsten smelting wastewater to 5-7 with hydrochloric acid, and the stirring time is 30-60 minutes.

2. The method for the synergistic treatment of lithium smelting slag and tungsten smelting wastewater with high fluorine, phosphorus, and arsenic content according to claim 1, characterized in that, In step S1, the stirring time is 1~3.5h, the water washing is repeated with deionized water until the pH of the washing water is 6~7, and the drying temperature is 60~80℃ for 2~3h.

3. The method for the synergistic treatment of lithium smelting slag and tungsten smelting wastewater with high fluorine, phosphorus, and arsenic content according to claim 1, characterized in that, In step S2, the stirring speed of the hydrothermal reaction is 100~200 rpm, the temperature is 120~180℃, and the time is 3~7h. The water washing is repeated with deionized water until the pH of the washing water is 7~8. The drying temperature is 60~80℃ and the time is 4~6h.

4. The method for the synergistic treatment of lithium smelting slag and tungsten smelting wastewater with high fluorine, phosphorus, and arsenic content according to claim 1, characterized in that, The tungsten smelting wastewater is an alkaline wastewater generated by alkaline decomposition ion exchange smelting process of wolframite, scheelite, or a mixture of wolframite and scheelite. Its pH value is 9-14, the concentration of fluorine is 10-200 mg / L, the concentration of phosphorus is 0.5-100 mg / L, and the concentration of arsenic is 0.5-50 mg / L.

5. The method for the synergistic treatment of lithium smelting slag and tungsten smelting wastewater with high fluorine, phosphorus, and arsenic content according to claim 1, characterized in that, The liquid-to-solid ratio of the acid-adjusted tungsten smelting wastewater to the modified slag is 1L:(10~40)g.

6. The method for the synergistic treatment of lithium smelting slag and tungsten smelting wastewater with high fluorine, phosphorus, and arsenic content according to claim 1, characterized in that, In step S3, the concentration of fluoride in the fluoride-removing, phosphorus-removing, and arsenic-removing wastewater is ≤10 mg / L, the concentration of phosphorus is ≤0.5 mg / L, and the concentration of arsenic is ≤0.5 mg / L.

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