Method for preparing heavy metal adsorption material from ionic rare earth tailings

Abstract

The invention discloses a method for preparing a heavy metal adsorption material from ionic rare earth tailings. The method comprises the steps of rare earth tailing sample pretreatment, rare earth tailing sample thermal activation treatment, rare earth tailing valuable element near-neutral elution treatment, near-neutral eluent pretreatment and heavy metal adsorption material preparation. The rare earth tailings are converted into the heavy metal adsorption material, so that the stockpiling requirement of the tailings can be remarkably reduced, and the land resource occupation of a tailings pond is reduced. The efficient heavy metal adsorption material is prepared through modification treatment by utilizing a porous mineral substrate and residual rare earth elements in the rare earth tailings, so that resource utilization of the tailings is realized, and the adsorption material can be directly applied to remediation of polluted water and soil around a mining area. The low-value rare earth tailings are converted into a high-added-value functional material, such as a heavy metal adsorbent, so that the resource value and the economic benefit of the tailings are remarkably improved.

Description

Technical Field

[0001] The present invention belongs to the fields of secondary utilization of solid waste and treatment of heavy metal water pollution, and particularly relates to a method for preparing a heavy metal adsorbent from ionic rare earth tailings. Background Art

[0002] As an important strategic resource in China, the exploitation of ionic rare earth ores in the south generates 1000 - 2000 tons of tailings for every 1 ton of rare earth oxide produced. Currently, these tailings are mainly stored in tailing ponds by building dams. However, due to relatively low early environmental protection standards, some design defects in tailing ponds, weak anti-seepage measures, and insufficient dam stability, the harmful components in the tailings have long threatened environmental safety. The residual rare earth ions, radioactive elements (such as thorium and uranium), and heavy metals such as lead, cadmium, and zinc in the tailings can be continuously released into the surrounding environment through rain leaching and seepage, causing groundwater and surface water pollution and endangering the farmland ecological system and the safety of residents' drinking water. At the same time, the radiation released by the decay of radioactive elements further increases the health risks, and the potential dam break hazard of the tailing pond may also trigger secondary disasters such as debris flows, exacerbating the ecological and public safety crises.

[0003] Currently, the disposal of tailings still mainly focuses on stacking combined with passive prevention and control, such as strengthening the dam body or building a cut-off drainage system. However, such methods only address the symptoms rather than the root causes. Although in recent years, attempts have been made to recover rare earth elements from tailings through technologies such as leaching and flotation, or to process them into building materials such as cement and ceramics, it is difficult to promote them on a large scale due to high technical costs and low recovery efficiency. In the field of ecological restoration, although means such as covering with soil and planting greenery, planting tolerant plants, or spraying chemical stabilizers are adopted, these methods generally face bottlenecks such as long restoration cycles, unstable effects, and high capital requirements. Traditional treatment methods are difficult to balance environmental risk control and resource value exploration, and there is an urgent need for more sustainable innovative solutions.

[0004] It is worth noting that the mineral characteristics of ionic rare earth tailings in the south provide a new direction for their resource utilization. The tailings are rich in clay minerals such as kaolin and montmorillonite and metal oxides. After modification treatments such as acid activation, functional group loading, or high-temperature calcination, their adsorption capacity for heavy metals such as lead, cadmium, and copper is significantly improved, and the adsorption capacity can reach 70% - 90% of that of traditional activated carbon, while the cost is only 1 / 5 - 1 / 3 of that of commercial adsorbents. More importantly, the residual rare earth elements (such as lanthanum and cerium) in the tailings can form catalytic active sites during the modification process, further strengthening the pollutant fixation effect. Therefore, by developing a new method for preparing heavy metal adsorbents from ionic rare earth tailings, the stockpile of tailings can be significantly reduced, the migration risks of heavy metals and radioactive substances can be lowered, and the common defects of high cost and long cycle of traditional treatment technologies can be made up for. At the same time, the generated adsorbent can be directly used to repair the polluted water bodies and soils around the mining areas, providing technical support for the green transformation of the rare earth industry. Summary of the Invention

[0005] The object of the present invention is to provide a method for preparing a heavy metal adsorbent material from ionic rare earth tailings, which effectively reduces the stockpile of tailings, reduces the migration risk of heavy metals and radioactive substances, and makes up for the disadvantages of high cost and long cycle of traditional treatment technologies.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] The present invention first discloses a method for preparing a heavy metal adsorbent material from ionic rare earth tailings, including:

[0008] S1. The rare earth tailings sample is subjected to ball milling, sieving, and drying to obtain a pretreated sample;

[0009] S2. The rare earth tailings sample is thermally activated. The purpose of the heat treatment is to further expand the porosity in the gangue minerals of the tailings and change its crystal form, which helps the subsequent functional metal loading process. After completion, it is cooled to room temperature and air-dried for storage;

[0010] S3. The air-dried sample is eluted with a complexing agent under near-neutral conditions to obtain an eluted sample and a near-neutral eluent;

[0011] S4. The near-neutral eluent is pretreated to obtain a metal-loaded stock solution and a porous substrate material;

[0012] S5. The porous substrate material is mixed with the metal-loaded stock solution and fully reacted in a water bath stirrer. Subsequently, a precipitating agent is added and the reaction is continued with stirring. The resulting solution is centrifuged and filtered, and the obtained precipitate is dried to obtain the heavy metal adsorbent material.

[0013] Further, the pretreated sample in step S1 is prepared by the following method:

[0014] The rare earth tailings sample is put into a ball mill for grinding, ball milled at a rotation speed of 200 - 1000 r / min for 0.5 - 6 h, then sieved through a 100 - 300 mesh sieve, and the sieved sample is dried at room temperature to 60 °C.

[0015] Further, the thermal activation treatment method in step S2 includes roasting treatment with a muffle furnace and a tube furnace for heating.

[0016] Further, the roasting treatment for heating includes: heating to 600 - 900 °C and roasting at this temperature for 1 - 4 h.

[0017] Further, the complexing agent in step S3 includes but is not limited to: amino carboxylic acid complexing agents, hydroxy carboxylic acid complexing agents, and alkanolamine complexing agents.

[0018] Further, the elution conditions in step S3 are as follows: the solid-liquid ratio of the air-dried sample to the complexing agent is 1:25 to 50, the leaching temperature of the elution reaction is 15 to 85 °C, and the elution time is 12 to 72 h. Among them, an increase in the solid-liquid ratio, an increase in temperature, or an extension of the leaching time may all improve the leaching effect.

[0019] Further, the amino carboxylic acid complexing agents include, but are not limited to: sodium nitrilotriacetate, ethylenediaminetetraacetate, diethylenetriaminepentaacetate; the hydroxy carboxylic acid complexing agents include, but are not limited to: tartrate, hepturonate, citrate, alginate; the alkanolamine complexing agents include, but are not limited to: monoethanolamine, diethanolamine, triethanolamine.

[0020] Further, the pretreatment of the near-neutral eluent in step S4 includes:

[0021] The near-neutral eluent is cooled to room temperature, and then centrifuged at high speed and frozen. The obtained supernatant is filtered to obtain an elution liquid containing lanthanum and cerium ions, which is stored as a metal-loading raw material. At the same time, the residual tailings residue in the centrifuge tube is rinsed 3 to 5 times with deionized water and then placed in an oven for drying to obtain a porous substrate material.

[0022] Further, the temperature of the oven is 50 to 80 °C.

[0023] Further, the mass-volume ratio of the porous substrate material to the metal-loading stock solution in step S5 is: 1 to 5 g: 10 to 50 mL; the reaction conditions of the water bath stirrer are: fully stirred at 25 to 80 °C and a rotation speed of 100 to 500 r / min for 1 to 12 h; the dosage of the precipitating agent is: 10 to 50 mL, and the continuous stirring time is 0.5 to 4 h; the drying temperature is 60 to 105 °C.

[0024] Further, the precipitating agents include, but are not limited to: oxalic acid, ammonia water, sodium hydroxide, lime water.

[0025] The present invention also discloses a heavy metal adsorbent material prepared by any of the above methods.

[0026] The present invention has at least the following technical effects:

[0027] (1) By converting rare earth tailings into heavy metal adsorbent materials, the storage requirements of tailings can be significantly reduced, thereby reducing the occupation of land resources by tailing ponds;

[0028] (2) By using the porous mineral substrate and residual rare earth elements in rare earth tailings, an efficient heavy metal adsorbent material is prepared through modification treatment, which can effectively realize the resource utilization of tailings;

[0029] (3) By converting low-value rare earth tailings into high-value-added functional materials, such as heavy metal adsorbents, the resource value and economic benefits of the tailings have been significantly improved. Description of the Drawings

[0030] Figure 1 Adsorption effect diagram of lead ions by the adsorption material prepared in Example 1 of the present invention;

[0031] Figure 2 Adsorption effect diagram of lead ions by the adsorption material prepared in Comparative Example 1 of the present invention. Detailed Embodiments

[0032] To make the technical objectives, technical solutions and technical effects of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Combining the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0033] The weights of the relevant components mentioned in the specification of the embodiments of the present invention not only can refer to the specific contents of each component, but also can represent the proportional relationship of the weights between each component. Therefore, as long as the contents of the relevant components in the specification of the embodiments of the present invention are enlarged or reduced in proportion, they are within the scope disclosed in the specification of the embodiments of the present invention. Specifically, the weights described in the specification of the embodiments of the present invention can be mass units well-known in the chemical industry such as μg, mg, g, kg, etc. The room temperature described in the specification of the embodiments of the present invention is 15 - 35°C.

[0034] Example 1:

[0035] First, the raw tailings were put into a planetary ball mill (QM-3SP4) and milled for 2 hours at a speed of 600 r / min. After screening through a 200-mesh sieve, the fine particles were collected and dried in a blast drying oven at 50 °C for 12 hours to obtain a homogenized pretreatment sample. Subsequently, 100 g of the pretreatment sample was spread flat in an alumina crucible and placed in a box-type muffle furnace (KSL-1700X). It was heated to 800 °C at a rate of 5 °C / min and calcined for 2 hours. After cooling to room temperature, thermally activated tailings were obtained. 20 g of the thermally activated tailings were mixed with 500 mL of 0.3 mol / L EDTA solution (pH = 7.0), and the reaction was carried out for 24 hours under the conditions of constant temperature magnetic stirring at 60 °C and 300 r / min to complete the near-neutral elution of rare earth ions. After the reaction, the suspension was cooled to 25 °C, centrifuged at 8000 r / min for 15 minutes, and the supernatant was filtered through a 0.45-μm filter membrane and stored refrigerated for later use; the centrifuged residue was washed 3 times with deionized water and dried at 60 °C for 6 hours to obtain a porous substrate material. 1.0 g of the porous substrate material was mixed with 20 mL of the filtrate containing lanthanum and cerium ions, and the loading reaction was carried out in a 60 °C water bath oscillator (200 r / min) for 6 hours. Subsequently, 0.5 mol / L NaOH solution was slowly added dropwise until pH = 9.0, and stirring was continued for 2 hours to precipitate rare earth hydroxides. The mixture was centrifuged at 8000 r / min for 15 minutes to collect the precipitate, which was washed 3 times with absolute ethanol and deionized water in turn, and finally dried at 80 °C for 12 hours to obtain a modified tailings material with heavy metal adsorption function. The adsorption effect of the modified ionic rare earth tailings material on heavy metal lead ions is as Figure 1 shown.

[0036] Example 2:

[0037] First, the raw tailings were put into a planetary ball mill (QM-3SP4) and milled for 1 hour at a speed of 1000 r / min. After screening through a 150-mesh sieve, the fine particles were collected and dried in a blast drying oven at 40 °C for 10 hours. Subsequently, the pretreatment sample was placed in a box-type muffle furnace and heated to 600 °C at a rate of 3 °C / min and calcined for 3 hours. After cooling, thermally activated tailings were obtained. 20 g of the thermally activated tailings were mixed with 500 mL of 0.5 mol / L sodium citrate solution (pH = 6.5), and the reaction was carried out at 50 °C and 300 r / min for 36 hours. The suspension was centrifuged at 6000 r / min for 20 minutes, and the supernatant was filtered through a 0.45-μm filter membrane and stored refrigerated for later use; the residue was washed and dried at 70 °C to obtain a porous substrate material. 1.0 g of the substrate material was loaded and reacted with 20 mL of the filtrate at 50 °C for 8 hours, and 0.2 mol / L Na 2 CO 3 solution was added until pH = 8.5, and stirring was continued for 3 hours. The precipitate was centrifuged, washed, and dried at 90 °C for 12 hours to obtain the adsorption material.

[0038] Example 3:

[0039] First, the raw tailings were ball-milled (400 r / min × 4 h), screened through a 250-mesh sieve, and then dried at 60 °C for 8 hours. Subsequently, the sample was heated to 900 °C at a rate of 10 °C / min and calcined for 1 hour, and then cooled for standby. 20 g of the thermally activated tailings were mixed with 500 mL of 0.1 mol / L DTPA solution (pH = 7.5), and the reaction was carried out at 70 °C and 300 r / min for 18 hours. The suspension was centrifuged at 10000 r / min for 10 minutes, and the filtrate was refrigerated; the residue was washed and dried at 50 °C to obtain the substrate material. 1.0 g of the substrate material was reacted with 20 mL of the filtrate at 70 °C for 4 hours, 1.0 mol / L NaOH solution was added dropwise until pH = 10.0, and stirred for 1 hour. The precipitate was centrifuged, washed, and dried at 105 °C to obtain the adsorbent material.

[0040] Example 4:

[0041] The ball-milling conditions were 800 r / min × 1.5 h, and after screening, it was dried at 55 °C for 14 hours. The thermal activation conditions were 750 °C × 2.5 h (heating rate 7 °C / min). The elution step used 0.4 mol / L triethanolamine solution (pH = 8.0), the solid-liquid ratio was 1:50 (20 g:1000 mL), and the reaction was carried out at 40 °C for 48 hours. The centrifugation conditions were 5000 r / min × 25 minutes, and the residue was washed and dried at 65 °C. In the loading reaction, the substrate material and the filtrate were reacted at 40 °C for 10 hours, 0.8 mol / L NH 3 ·H 2 O solution was added dropwise until pH = 9.5, and the precipitate was washed and dried at 75 °C to obtain the adsorbent material.

[0042] Example 5:

[0043] The ball-milling conditions were 300 r / min × 6 h, and after screening, it was dried at 45 °C for 16 hours. The thermal activation used gradient calcination: first heated to 500 °C at a rate of 5 °C / min and held for 1 h, then heated to 800 °C and held for 2 h. The elution used 0.6 mol / L sodium tartrate solution (pH = 7.2), the solid-liquid ratio was 1:30 (20 g:600 mL), and the reaction was carried out at 80 °C for 12 hours. The centrifugation conditions were 12000 r / min × 5 minutes, and the residue was washed and dried at 55 °C. In the loading reaction, the substrate material and the filtrate were reacted at 80 °C for 3 hours, 0.3 mol / L K 2 CO 3 solution was added dropwise until pH = 8.0, and the precipitate was washed and dried at 100 °C to obtain the adsorbent material.

[0044] Example 6:

[0045] The ball milling is carried out in two stages (500 r / min × 1 h + 800 r / min × 1 h). After screening, it is dried at 50 °C for 12 hours. The thermal activation conditions are 700 °C × 3 h (heating rate 6 °C / min). The elution is carried out using a 0.2 mol / L sodium alginate solution (pH = 7.8), with a solid-liquid ratio of 1:40 (20 g:800 mL), and the reaction is carried out at 30 °C for 72 hours. The centrifugation conditions are 9000 r / min × 12 minutes, and the residue is washed and dried at 60 °C. In the loading reaction, the substrate material and the filtrate react at 30 °C for 12 hours, and 0.4 mol / L Ca(OH) 2 suspension is added until the pH = 10.5. The precipitate is washed and then dried at 85 °C to obtain the adsorbent material.

[0046] Example 7:

[0047] The ball milling conditions are 1200 r / min × 0.5 h (the maximum rotation speed allowed by the equipment). After screening, it is dried at 70 °C for 6 hours. The thermal activation conditions are 850 °C × 1.5 h (heating rate 15 °C / min). The elution is carried out using a 0.7 mol / L NTA solution (pH = 6.8), with a solid-liquid ratio of 1:20 (20 g:400 mL), and the reaction is carried out at 85 °C for 6 hours. The centrifugation conditions are 15000 r / min × 8 minutes, and the residue is washed and dried at 75 °C. In the loading reaction, the substrate material and the filtrate react at 25 °C for 24 hours, and 0.6 mol / L Mg(OH) 2 suspension is added until the pH = 9.8. The precipitate is washed and then dried at 95 °C to obtain the adsorbent material.

[0048] Comparative Example 1

[0049] First, the chalcopyrite tailings were put into a planetary ball mill (QM-3SP4) and ball-milled at a speed of 600 r / min for 2 hours. After screening through a 200-mesh sieve, the fine particles were collected and placed in a blast drying oven at 50 °C for drying for 12 hours to obtain a homogenized pretreatment sample. Subsequently, 100 g of the pretreatment sample was spread out flat in an alumina crucible and placed in a box-type muffle furnace (KSL-1700X). It was heated to 800 °C at a rate of 5 °C / min and calcined for 2 hours. After cooling to room temperature, thermally activated tailings were obtained. 20 g of the thermally activated tailings were mixed with 500 mL of 0.3 mol / L EDTA solution (pH = 7.0), and the reaction was carried out for 24 hours under the conditions of constant temperature magnetic stirring at 60 °C and 300 r / min to complete the near-neutral elution of rare earth ions. After the reaction, the suspension was cooled to 25 °C, centrifuged at 8000 r / min for 15 minutes, and the supernatant was filtered through a 0.45-μm filter membrane and stored in the refrigerator for later use; the centrifuged residue was washed 3 times with deionized water and dried at 60 °C for 6 hours to obtain a porous substrate material. 1.0 g of the porous substrate material was mixed with 20 mL of the filtrate containing lanthanum and cerium ions, and the loading reaction was carried out in a 60 °C water bath oscillator (200 r / min) for 6 hours. Subsequently, 0.5 mol / L NaOH solution was slowly added dropwise until pH = 9.0, and stirring was continued for 2 hours to precipitate rare earth hydroxides. The mixture was centrifuged at 8000 r / min for 15 minutes to collect the precipitate, which was washed 3 times with anhydrous ethanol and deionized water in turn, and finally dried at 80 °C for 12 hours to obtain a modified tailings material with heavy metal adsorption function. The adsorption effect of the modified chalcopyrite tailings material on heavy metal lead ions is as Figure 2 shown.

[0050] Test Example 1

[0051] This test example aimed to explore the adsorption performance of the modified tailings materials in Example 1 and Comparative Example 1 for lead ions and determine their adsorption capacity. In the experiment, 1.0 g of activated carbon was reacted with 100 mL of a lead ion solution with a predetermined concentration (100 mg / L) in a constant temperature oscillator (25 °C, 800 min), and the pH value of the solution was adjusted to 5. After the reaction, the supernatant was taken for centrifugal separation, and the lead ion concentration was measured using ICP-OES, and the adsorption capacity q (mg / g) was calculated. The formula is q = (C 0 -C e ) * V / m, where C 0 is the initial concentration, C e is the equilibrium concentration, V is the solution volume, and m is the mass of the modified tailings material.

[0052] The test results are as Figure 1 and Figure 2 shown:

[0053] As Figure 1As shown, the modified ionic rare earth tailing adsorbent prepared in Example 1 has excellent adsorption performance for lead ions, reaching the adsorption saturation state within 800 min of adsorption time, and cumulatively adsorbing 121 mg of lead ions, with an equivalent adsorption capacity of 121 mg / g. As Figure 2 shown, the adsorption performance of the modified chalcopyrite tailing adsorbent prepared in Comparative Example 1 for lead ions is weaker than that of Example 1, and only 79 mg of lead ions are adsorbed within 800 min of adsorption time, with an equivalent adsorption capacity of 79 mg / g. Thus, it can be seen that the heavy metal adsorbent prepared based on ionic rare earth tailings has more excellent adsorption performance for lead ions than the adsorbents prepared by modifying other traditional tailings (such as chalcopyrite tailings).

[0054] The above describes the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing heavy metal adsorption materials from ionic rare earth tailings, comprising: S1. The rare earth tailings sample is ball-milled, sieved and dried to obtain a pre-treated sample; S2, thermal activation treatment of rare earth tailings samples, cooling to room temperature, and air-drying for storage; S3, using a complexing agent to perform near-neutral elution treatment on the air-dried sample to obtain an eluted sample and a near-neutral eluent; S4, pretreating the nearly neutral eluent to obtain a metal-loaded stock solution and a porous substrate material; S5. Mix the porous substrate material with the metal loading stock solution and fully react them in a water bath stirrer. Then, add a precipitant and continue stirring the reaction. The obtained solution is centrifuged and filtered, and the obtained precipitate is dried to obtain a heavy metal adsorption material.

2. The method according to claim 1, wherein: The pretreated sample in step S1 is prepared by the following method: The rare earth tailings sample is placed in a ball mill for grinding at a speed of 200 to 1000 r / min for 0.5 to 6 hours, and then passed through a 100 to 300 mesh sieve, the sieved sample is dried at room temperature to 60°C.

3. The method according to claim 1, wherein: The thermal activation treatment method in step S2 includes heating and calcining treatment in a muffle furnace or a tubular furnace.

4. The method according to claim 3, wherein: The temperature-raising calcination process comprises: Raise the temperature to 600-900°C and keep calcining at this temperature for 1-4 hours.

5. The method according to claim 1, wherein: The complexing agent in step S3 comprises: Aminocarboxylic acid complexing agents, hydroxycarboxylic acid complexing agents, alcoholamine complexing agents; The elution conditions are as follows: the solid-liquid ratio of the air-dried sample to the complexing agent is 1:25-50, the leaching temperature of the elution reaction is 15-85° C., and the elution time is 12-72 hours.

6. The method according to claim 5, wherein: The aminocarboxylic acid complexing agent includes sodium nitrilotriacetate, ethylenediaminetetraacetate, and diethylenetriaminepentacarboxylate; The hydroxycarboxylic acid complexing agent includes: tartrate, heptanoate, citrate, and alginate; The alcoholamine complexing agent includes: monoethanolamine, diethanolamine, and triethanolamine.

7. The method according to claim 1, wherein: The near-neutral eluent pretreatment in step S4 includes: The nearly neutral eluent is cooled to room temperature and then subjected to high-speed refrigerated centrifugation. The supernatant obtained is filtered to obtain an elution liquid containing lanthanum and cerium ions, which is stored as a metal loading raw material. At the same time, the remaining tailings residue in the centrifuge tube is rinsed with deionized water for 3 to 5 times and placed in an oven for drying to obtain a porous substrate material.

8. The method according to claim 7, wherein: The oven temperature is 50-80°C.

9. The method according to claim 1, wherein: The mass volume ratio of the porous substrate material to the metal loading stock solution in step S5 is: 1-5 g: 10-50 mL; The reaction conditions of the water bath agitator are: stirring for 1 to 12 hours at 25 to 80°C and a rotation speed of 100 to 500 r / min; The amount of the precipitant is: 10-50 mL, and the stirring time is 0.5-4 h; The drying temperature is 60-105°C.

10. A heavy metal adsorption material prepared according to the method according to any one of claims 1 to 9.

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