Lithium slag-based soil remediation agent and method for synergistically solidifying heavy metals by using same

Abstract

The invention discloses a lithium slag-based soil remediation agent and a method for synergistically solidifying heavy metals by using the same. The lithium slag-based soil remediation agent comprises the following raw materials in parts by weight: 60-80 parts of lithium slag, 10-20 parts of an alkaline activator, 5-10 parts of a crystallization aid and 10-30 parts of deionized water. The soil remediation agent has the advantage of being environmentally friendly, and the problems that in the using process of an existing soil remediation agent, lithium slag is not convenient to recycle, the material cost in the preparation process is high, and the remediation cost of contaminated soil is increased are solved.

Description

Technical Field

[0001] This invention relates to the field of soil remediation technology, specifically to lithium slag-based soil remediation agents and methods for synergistically solidifying heavy metals. Background Technology

[0002] Lithium slag-based soil remediation agents are novel environmentally friendly materials developed using lithium slag as a base material, combined with other functional materials, for the remediation of soil contaminated with heavy metals. Their core objective is to solidify or stabilize free heavy metal ions in the soil through mechanisms such as physical adsorption, chemical precipitation, and complexation reactions, thereby reducing their mobility and bioavailability, and minimizing harm to the environment and ecosystems. Existing lithium slag-based soil remediation agents utilize a two-step alkali-fusion-crystallization method to transform lithium slag into molecular sieve materials, leveraging their porous structure to adsorb and solidify heavy metal ions. Alternatively, they employ a combination of chemical binders, coagulants, and hardening materials to achieve synergistic stabilization of heavy metals.

[0003] Existing soil remediation agents are not easy to recycle during use, resulting in high material costs in the preparation process and increasing the cost of remediating contaminated soil. Summary of the Invention

[0004] The purpose of this invention is to provide a lithium slag-based soil remediation agent and a method for synergistically solidifying heavy metals. This method has the advantage of being environmentally friendly and solves the problem that existing soil remediation agents are not easy to recycle during use, resulting in high material costs in the preparation process and increasing the cost of remediating contaminated soil.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a lithium slag-based soil remediation agent, comprising the following raw materials in parts by weight:

[0006] 60-80 parts lithium slag, 10-20 parts alkaline activator, 5-10 parts crystallization aid, and 10-30 parts deionized water.

[0007] A method for synergistically solidifying heavy metals with lithium slag-based soil remediation agents includes the following steps:

[0008] S1. Lithium slag treatment: Use a jaw crusher or ball mill to crush the lithium slag. After crushing, use a vibrating screen to screen the lithium slag particles. The lithium slag particles that do not meet the screening requirements are sent back to the jaw crusher or ball mill for secondary crushing.

[0009] S2. Alkaline activator is mixed. The screened lithium slag particles and alkaline activator are put into a planetary ball mill for wet mixing and grinding. After grinding, the wet material is taken out and subjected to calcination and water immersion treatment to obtain a sol containing silicon and aluminum.

[0010] S3. Adjust the molecular sieve structure. Adjust the silicon-aluminum ratio of the sol according to the type of molecular sieve. Add silicon dioxide or aluminum oxide to the sol during the adjustment process.

[0011] S4. Crystallization reaction: Pour the adjusted silica-alumina sol and crystallization aid into the stirring equipment and mix them evenly. Then, transport the mixture to the high-pressure reactor. The high-pressure reactor heats the sol under high pressure and high temperature to synthesize molecular sieve crystals with regular pore structure.

[0012] S5. Washing treatment: Wash the molecular sieve crystals 3-5 times with deionized water and washing equipment until the pH of the washing solution is 7-8 to remove residual alkaline substances and stabilize the molecular sieve structure.

[0013] S6. Molding process: The cleaned molecular sieve crystals and binder are stirred and mixed, and then fed into the molding equipment for molding. After molding, a firing process is carried out to improve mechanical strength, and finally lithium slag-based soil remediation agent is prepared.

[0014] In a preferred embodiment of the method for co-solidifying heavy metals with lithium slag-based soil remediation agent of the present invention, the diameter of the crushed lithium slag particles in S1 is 0.1-0.5 mm, the vibrating screen is equipped with a screen with a screening diameter of 0.1-0.25 mm, and the qualified lithium slag particles are dried after screening. The water content of the dried lithium slag particles is 5-10%. During drying, a microwave drying device is used to heat and dry the lithium slag particles with microwave.

[0015] As a preferred method for the co-solidification of heavy metals with lithium slag-based soil remediation agent of the present invention, in S2, when the planetary ball mill is used for wet mixing and grinding, the ball-to-material ratio is 3:1, the rotation speed is 250-350 rpm, and the time is 0.5-1.5 hours. During the calcination treatment, the wet material is put into the calcination furnace, and the calcination furnace is heated to 750-900℃ at 10℃ / min. After reaching the set temperature, the heating is stopped and the temperature is maintained for 1-2 hours. After the temperature maintenance is completed, the material is naturally cooled to room temperature to obtain a grayish-white powder containing oligomeric aluminosilicates. During the water immersion treatment, the calcined powder and deionized water are poured into a stirring device and stirred for 30-60 minutes to obtain a sol. Then, the particulate matter in the sol is filtered using a filtration device.

[0016] In a preferred embodiment of the method for co-solidifying heavy metals with lithium slag-based soil remediation agent of the present invention, before adjusting the silicon-aluminum ratio of the sol in step S3, a silicon-aluminum ratio range is set according to the molecular sieve type. Then, a certain amount of silicon dioxide or aluminum oxide is added according to the set silicon-aluminum ratio range and mixed evenly. After mixing, the pH value of the sol is adjusted.

[0017] As a preferred method for the co-solidification of heavy metals with lithium slag-based soil remediation agent of the present invention, the high-pressure reactor in S4 is made of stainless steel with a volume of 5-20L, a heating temperature of 140-200℃, and a time of 24-72 hours. During the generation of molecular sieve crystals, samples are taken every 12 hours, and the growth of molecular sieve crystals is analyzed by XRD. Crystallization terminates when obvious molecular sieve characteristic peaks appear in the XRD pattern.

[0018] In a preferred embodiment of the method for co-solidifying heavy metals with lithium slag-based soil remediation agent of the present invention, after cleaning in step S5, the molecular sieve crystals are poured into a centrifuge. The centrifuge rotates at 3000 rpm for 10 minutes to separate solids and liquids. After centrifugation, the molecular sieve crystals are placed in a vacuum drying oven. The heating temperature of the vacuum drying oven is 80-120°C, and the heating time is 5-10 hours.

[0019] In the preferred method of co-solidifying heavy metals with lithium slag-based soil remediation agent of the present invention, the binder in S6 is bentonite or silica sol. A high-speed mixer is used for stirring and mixing, with a mixing time of 5-15 minutes. The moisture content of the mixed material is 10-15%. The molding equipment is a screw extruder with a screw speed of 10-40 rpm and a molding temperature of 30-60°C. The discharge end of the screw extruder is equipped with a molding die with several molding holes of 1-3 mm in diameter. During the firing process, a continuous rotary kiln is used for high-temperature heating at a temperature of 500-600°C and a heating rate of 5-10°C / min.

[0020] As a preferred method for the co-solidification of heavy metals by lithium slag-based soil remediation agent of the present invention, after the lithium slag-based soil remediation agent is prepared, the quality of the lithium slag-based soil remediation agent is verified. When verifying the quality, characterization detection is first performed, including X-ray diffraction detection, specific surface area and pore size distribution analysis detection and scanning electron microscopy detection. Then, performance testing is performed, including adsorption capacity testing and stability testing.

[0021] As a preferred method for the synergistic solidification of heavy metals by lithium slag-based soil remediation agent of the present invention, a qualified lithium slag-based soil remediation agent is added to the soil to adsorb and solidify the heavy metals inside the soil.

[0022] Before adding lithium slag-based soil remediation agent, the initial concentration of heavy metals in the soil is determined by XRF or ICP-OES, and the pH value of the soil is also determined. Based on the pH value, the pH value of the soil is adjusted to 5-6. After the determination is completed, the contaminated soil is crushed using a jaw crusher. The particle size of the crushed soil particles is less than 5 cm to increase the specific surface area. The addition ratio of lithium slag-based soil remediation agent is determined based on the soil pollution test results.

[0023] When adding lithium slag-based soil remediation agent, use a rotary tiller or scraper to thoroughly mix the agent with the soil to a depth of 30-50cm. After mixing, the agent should be evenly distributed in the soil without agglomeration. Allow the mixture to stand for 7-14 days to ensure that the agent reacts fully with the heavy metals and maintain a soil moisture content of 20-30%. After the curing period, use TCLP or BCR continuous extraction method to determine the leaching capacity of heavy metals in the soil.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] 1. This invention solves the problems of high material costs and low efficiency in traditional heavy metal pollution control by transforming lithium slag into a soil remediation agent. Through precise control of the lithium slag processing technology, the adsorption performance and mechanical strength of the remediation agent are significantly improved. The regular pore structure and ion exchange capacity of the molecular sieve crystals increase the adsorption capacity of the remediation agent for heavy metals. By adjusting the silicon-aluminum ratio, the type of crystallization aid, and the calcination temperature, different types of molecular sieves can be flexibly synthesized to meet diverse soil remediation needs. Using bentonite or silica sol as a binder, combined with screw extrusion molding and continuous rotary kiln firing, the mechanical strength of the remediation agent particles is improved, meeting the physical stability requirements under complex terrain.

[0026] 2. This invention realizes the high-value utilization of lithium slag waste, promotes the deep integration of circular economy and green development, transforms the highly polluting lithium slag generated by the lithium battery industry into functional soil remediation materials, reduces the land occupation and secondary pollution risks of stockpiling, and reduces the cost of remediation agent raw materials. The remediation agent has passed the TCLP toxicity leaching test, and the preparation process uses low-energy equipment, reducing carbon emissions compared to the traditional cement solidification method. The remediation agent is mixed with a rotary tiller for construction and is suitable for the remediation of large areas of farmland, industrial sites and riverbed sediment. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the method flow of the present invention. Detailed Implementation

[0028] Example 1

[0029] Lithium slag-based soil remediation agent comprises the following raw materials in parts by weight:

[0030] 60-80 parts lithium slag, 10-20 parts alkaline activator, 5-10 parts crystallization aid, and 10-30 parts deionized water.

[0031] By transforming lithium slag into a high-value-added soil remediation agent, the dual goals of efficient utilization of industrial solid waste and heavy metal pollution control are achieved. Using lithium slag as raw material, the silicon-aluminum ratio is controlled by alkaline activators and the crystal structure is optimized by crystallization aids to synthesize molecular sieve materials with regular channels. This solves the environmental pollution problem caused by lithium slag stockpiling. The remediation agent has a high adsorption capacity for heavy metals, significantly reducing the leaching of heavy metals in the soil. The unit treatment cost of the remediation agent is lower than that of the traditional cement solidification method, and the formed particles have high mechanical strength, making it suitable for complex scenarios such as farmland and industrial sites.

[0032] Example 2

[0033] Please see Figure 1 A method for synergistically solidifying heavy metals with lithium slag-based soil remediation agents includes the following steps:

[0034] S1. Lithium slag treatment: Use a jaw crusher or ball mill to crush the lithium slag. After crushing, use a vibrating screen to screen the lithium slag particles. The lithium slag particles that do not meet the screening requirements are sent back to the jaw crusher or ball mill for secondary crushing.

[0035] S2. Alkaline activator is mixed. The screened lithium slag particles and alkaline activator are put into a planetary ball mill for wet mixing and grinding. After grinding, the wet material is taken out and subjected to calcination and water immersion treatment to obtain a sol containing silicon and aluminum.

[0036] S3. Adjust the molecular sieve structure. Adjust the silicon-aluminum ratio of the sol according to the type of molecular sieve. Add silicon dioxide or aluminum oxide to the sol during the adjustment process.

[0037] S4. Crystallization reaction: Pour the adjusted silica-alumina sol and crystallization aid into the stirring equipment and mix them evenly. Then, transport the mixture to the high-pressure reactor. The high-pressure reactor heats the sol under high pressure and high temperature to synthesize molecular sieve crystals with regular pore structure.

[0038] S5. Washing treatment: Wash the molecular sieve crystals 3-5 times with deionized water and washing equipment until the pH of the washing solution is 7-8 to remove residual alkaline substances and stabilize the molecular sieve structure.

[0039] S6. Molding process: The cleaned molecular sieve crystals and binder are stirred and mixed, and then fed into the molding equipment for molding. After molding, a firing process is carried out to improve mechanical strength, and finally lithium slag-based soil remediation agent is prepared.

[0040] The diameter of the crushed lithium slag particles in S1 is 0.1-0.5mm. The vibrating screen is equipped with a screen with a screening diameter of 0.1-0.25mm. After screening, the qualified lithium slag particles are dried. The water content of the dried lithium slag particles is 5-10%. During the drying process, a microwave drying device is used to heat and dry the lithium slag particles with microwaves.

[0041] When performing wet mixing and grinding in the S2 planetary ball mill, the ball-to-material ratio is 3:1, the rotation speed is 250-350 rpm, and the time is 0.5-1.5 hours. During the calcination process, the wet material is placed in the calcination furnace, which is heated to 750-900℃ at a rate of 10℃ / min. After reaching the set temperature, heating is stopped, and the temperature is maintained for 1-2 hours. After the temperature maintenance is completed, the material is allowed to cool naturally to room temperature, resulting in a grayish-white powder containing oligomeric aluminosilicates. During the water immersion process, the calcined powder and deionized water are poured into a stirring device and stirred for 30-60 minutes to obtain a sol. Then, a filtration device is used to filter the particulate matter in the sol.

[0042] Before adjusting the silica-alumina ratio of the sol in S3, the silica-alumina ratio range is set according to the molecular sieve type. Then, a certain amount of silica or alumina is added according to the set silica-alumina ratio range and mixed evenly. After mixing, the pH value of the sol is adjusted.

[0043] The high-pressure reactor in S4 is made of stainless steel with a volume of 5-20L. The heating temperature is 140-200℃ and the time is 24-72 hours. During the formation of molecular sieve crystals, samples are taken every 12 hours, and the growth of molecular sieve crystals is analyzed by XRD. Crystallization terminates when obvious characteristic peaks of molecular sieves appear in the XRD pattern.

[0044] After cleaning in S5, the molecular sieve crystals are poured into a centrifuge. The centrifuge speed is 3000 rpm and the centrifugation time is 10 minutes to separate the solid and liquid. After centrifugation, the molecular sieve crystals are placed in a vacuum drying oven. The heating temperature of the vacuum drying oven is 80-120℃ and the heating time is 5-10 hours.

[0045] The binder in S6 is bentonite or silica sol. A high-speed mixer is used for mixing, with a mixing time of 5-15 minutes. The moisture content of the mixed material is 10-15%. The molding equipment is a screw extruder with a screw speed of 10-40 rpm and a molding temperature of 30-60℃. The discharge end of the screw extruder is equipped with a molding die with several molding holes of 1-3 mm in diameter. During the firing process, a continuous rotary kiln is used for high-temperature heating at 500-600℃ at a heating rate of 5-10℃ / min.

[0046] After the lithium slag-based soil remediation agent is prepared, its quality is verified. The quality verification process begins with characterization testing, which includes X-ray diffraction, specific surface area and pore size distribution analysis, and scanning electron microscopy. Then, performance testing is conducted, including adsorption capacity testing and stability testing.

[0047] Add qualified lithium slag-based soil remediation agent to the soil to adsorb and solidify heavy metals inside the soil.

[0048] Before adding lithium slag-based soil remediation agent, the initial concentration of heavy metals in the soil is determined by XRF or ICP-OES, and the pH value of the soil is also determined. Based on the pH value, the pH value of the soil is adjusted to 5-6. After the determination is completed, the contaminated soil is crushed using a jaw crusher. The particle size of the crushed soil particles is less than 5 cm to increase the specific surface area. The addition ratio of lithium slag-based soil remediation agent is determined based on the soil pollution test results.

[0049] When adding lithium slag-based soil remediation agent, use a rotary tiller or scraper to thoroughly mix the agent with the soil to a depth of 30-50cm. After mixing, the agent should be evenly distributed in the soil without agglomeration. Allow the mixture to stand for 7-14 days to ensure that the agent reacts fully with the heavy metals and maintain a soil moisture content of 20-30%. After the curing period, use TCLP or BCR continuous extraction method to determine the leaching capacity of heavy metals in the soil.

[0050] By transforming lithium slag into a high-value-added soil remediation agent, the dual goals of efficient utilization of industrial solid waste and heavy metal pollution control are achieved. Using lithium slag as raw material, the silicon-aluminum ratio is controlled by alkaline activators, and the crystal structure is optimized by crystallization aids to synthesize molecular sieve materials with regular channels. This solves the environmental pollution problem caused by lithium slag stockpiling. At the same time, industrial solid waste is transformed into functional materials, which is in line with the concept of circular economy. By precisely controlling the crushing particle size, calcination temperature and crystallization time, the high crystallinity and pore uniformity of the molecular sieve crystals are ensured. Combined with low-energy-consumption processes such as microwave drying and vacuum drying, production efficiency is improved. The unit treatment cost of the remediation agent is lower than that of the traditional cement solidification method. At the same time, it reduces the land occupation and ecological risks caused by lithium slag stockpiling and promotes the coordinated development of new energy industry and soil remediation technology.

[0051] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A lithium residue-based soil remediation agent, characterized by, The raw materials include the following by weight: 60-80 parts of lithium residue, 10-20 parts of alkaline activator, 5-10 parts of crystallization aid, and 10-30 parts of deionized water.

2. A method for remediation of soil with lithium residue-based soil remediation agent in cooperation with solidification of heavy metals, characterized by, The method includes the following steps: S1, lithium residue treatment, using a jaw crusher or ball mill to crush the lithium residue, and using a vibrating screen to screen the lithium residue particles after crushing, unqualified lithium residue particles are returned to the jaw crusher or ball mill for secondary crushing; S2, alkaline activator mixing, putting the screened lithium residue particles and alkaline activator into a planetary ball mill for wet mixing and grinding, taking out the wet material after grinding, and performing calcination treatment and water immersion treatment to obtain a sol containing silicon and aluminum; S3, regulating the molecular sieve structure, adjusting the silicon-aluminum ratio of the sol according to the type of molecular sieve, and adding silica or alumina to the sol during the adjustment process; S4, crystallization reaction, pouring the adjusted silicon-aluminum sol and crystallization aid into a stirring device for uniform mixing, and then conveying the mixture to a high-pressure reaction kettle, which performs high-pressure and high-temperature heating on the sol to synthesize molecular sieve crystals with regular pore structure; S5, washing treatment, using deionized water and cleaning equipment to wash the molecular sieve crystals 3-5 times until the pH of the washing liquid is 7-8 to remove residual alkaline substances and stabilize the molecular sieve structure; S6, shaping treatment, stirring and mixing the cleaned molecular sieve crystals and binder, then feeding into the shaping equipment for shaping, and then performing sintering treatment to improve the mechanical strength, finally preparing a lithium residue-based soil remediation agent.

3. The method of claim 2, wherein the lithium slag-based soil remediation agent cooperatively solidifies heavy metals. In S1, the crushed lithium residue particles have a diameter of 0.1-0.5mm, the vibrating screen has a screen mesh with a screening diameter of 0.1-0.25mm, and the qualified lithium residue particles are dried after screening, the water content of the dried lithium residue particles is 5-10%, and the lithium residue particles are heated and dried using a microwave drying device during drying.

4. The method of claim 3, wherein the lithium slag-based soil remediation agent cooperatively solidifies heavy metals. In S2, the planetary ball mill performs wet mixing and grinding with a ball-to-material ratio of 3:1, a rotation speed of 250-350rpm, and a time of 0.5-1.5 hours, the wet material is placed in a calcination furnace during calcination treatment, the calcination furnace is heated to 750-900℃ at a rate of 10℃ / min, heating is stopped after reaching the set temperature, and the temperature is maintained for 1-2 hours, then naturally cooled to room temperature to obtain a grayish white powder containing oligomeric silicate, and the powder and deionized water are poured into a stirring device during water immersion treatment, stirred for 30-60min to obtain a sol, and then the particulate matter in the sol is filtered using a filtering device.

5. The method of claim 4, wherein the lithium slag-based soil remediation agent synergistically solidifies heavy metals. In S3, before adjusting the silicon-aluminum ratio of the sol, the silicon-aluminum ratio range is set according to the type of molecular sieve, then a certain amount of silica or alumina is added according to the set silicon-aluminum ratio range and uniformly mixed, and the pH value of the sol is adjusted after mixing.

6. The method of claim 5, wherein the lithium slag-based soil remediation agent synergistically solidifies heavy metals. The high-pressure reactor material in S4 is stainless steel, the volume is 5-20L, the heating temperature is 140-200℃, the time is 24-72 hours, during the process of generating molecular sieve crystals, sampling every 12 hours, through XRD analysis of the growth of molecular sieve crystals, when the XRD pattern appears obvious molecular sieve characteristic peak, the crystallization stops.

7. The method of claim 6, wherein the lithium slag-based soil remediation agent synergistically solidifies heavy metals. After cleaning in S5, the molecular sieve crystals are poured into a centrifugal device, the rotation speed of the centrifugal device is 3000rpm, the centrifugal time is 10min, to separate the solid and liquid, after centrifugation, the molecular sieve crystals are put into a vacuum drying oven, the heating temperature of the vacuum drying oven is 80-120℃, the heating time is 5-10 hours.

8. The method of claim 7, wherein the lithium slag-based soil remediation agent synergistically solidifies heavy metals. The binder in S6 is bentonite or silica sol, a high-speed mixer is used during stirring and mixing, the mixing time is 5-15min, the water content of the mixed material is 10-15%, the forming equipment is a screw extruder, the screw rotation speed of the screw extruder is 10-40rpm, the forming temperature is 30-60℃, the discharge end of the screw extruder is provided with a forming die, a plurality of forming holes are formed on the forming die, the diameter of the forming holes is 1-3mm, during the sintering process, a continuous rotary kiln is used for high-temperature heating, the heating temperature is 500-600℃, the heating rate is 5-10℃ / min.

9. The method of claim 8, wherein the lithium slag-based soil remediation agent synergistically solidifies heavy metals. After the preparation of the lithium residue-based soil remediation agent, the quality of the lithium residue-based soil remediation agent is verified, during the quality verification, characterization detection is performed, the characterization detection methods include X-ray diffraction detection, specific surface area and pore size distribution analysis detection and scanning electron microscope detection, then performance testing is performed, the performance testing includes adsorption capacity testing and stability testing.

10. The method of claim 9, wherein the lithium slag-based soil remediation agent synergistically solidifies heavy metals. The qualified lithium residue-based soil remediation agent is added to the soil to adsorb and solidify the heavy metals in the soil; Before adding the lithium residue-based soil remediation agent, the initial concentration of heavy metals in the soil is determined by XRF or ICP-OES, and the pH value of the soil is determined, and according to the detected pH value, the pH value of the soil is adjusted to 5-6, after the determination, the contaminated soil is crushed by a jaw crusher, the particle size of the crushed soil particles is less than 5cm, to increase the specific surface area, and according to the soil pollution detection results, the addition ratio of the lithium residue-based soil remediation agent is determined; When adding the lithium residue-based soil remediation agent, a rotary tiller or a scraper is used to mix the lithium residue-based soil remediation agent with the soil, the mixing depth is 30-50cm, the lithium residue-based soil remediation agent is uniformly distributed in the soil after mixing, without agglomeration, after mixing, the mixture is left to cure for 7-14 days to ensure that the remediation agent and the heavy metals fully react, the soil moisture content is maintained at 20-30%, after curing, the TCLP or BCR continuous extraction method is used to determine the leachability of heavy metals in the soil.

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