Wet magnetic separation repair process for heavy metal residue soil mixture

Abstract

The invention relates to the technical field of soil remediation processes, and provides a heavy metal muck mixture wet magnetic separation remediation process, which comprises the following steps: ectopic soil sampling: carrying out three-dimensional deep soil sampling on a marked land parcel and ectopic storage; pretreatment is conducted, specifically, the soil stored in different positions is subjected to crushing treatment; pulping: adding water into the crushed ex-situ soil, and stirring to obtain slurry; local dilution and magnetic suction impurity removal are conducted, specifically, the slurry penetrates through a magnetic suction area in a flowing mode, local dilution is conducted on the magnetic suction area, and adsorbed impurities in the magnetic suction area are removed; performing dehydration detection, namely dehydrating the mud subjected to magnetic suction impurity removal, performing heavy metal detection, and judging whether detection is qualified or not; and backfilling is conducted, specifically, the soil is backfilled after detection is qualified. By means of the technical scheme, the problem that in the prior art, the traditional ex-situ leaching remediation effect of the soil polluted by the heavy metal muck mixture is poor is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of soil remediation processes, and specifically, to a wet magnetic separation remediation process for heavy metal slag and soil mixtures. Background Art

[0002] Soil washing technology is divided into in-situ washing and ex-situ washing according to different treatment methods. The in-situ washing method is to directly inject the washing agent into the soil, extract the washing liquid from the soil surface downstream, and then treat the washing liquid, and so on until the soil environmental quality reaches relevant standards. Ex-situ washing is to excavate the contaminated soil, use the washing liquid to wash and remove or transfer and concentrate the pollutants in the soil, and finally treat the washing liquid containing pollutants or the concentrated mud cake after reduction. This technology can be used for the remediation of heavy metal contaminated soil and persistent organic contaminated soil such as polycyclic aromatic hydrocarbons, polychlorinated biphenyls, and organochlorine pesticides.

[0003] However, in the existing technology for the process of using ex-situ washing to remediate soil, heavy metal pollutants in the soil often exist in the soil in the form of ions, but there are also some heavy metal pollutants existing in the soil in the form of alloy waste slag and soil mixtures. The traditional washing remediation process cannot effectively remediate them. Therefore, a new remediation process is needed to remediate the soil. Summary of the Invention

[0004] The present invention provides a wet magnetic separation remediation process for heavy metal slag and soil mixtures, which solves the problem of poor remediation effect of traditional ex-situ washing for heavy metal slag and soil mixture contaminated soil in the existing technology.

[0005] The technical solution of the present invention is as follows: A wet magnetic separation remediation process for heavy metal slag and soil mixtures, the remediation process comprising the following steps: Ex-situ soil sampling, taking soil from the marked plot in a three-dimensional depth and storing it ex-situ; Pretreatment, crushing the soil stored ex-situ; Slurry preparation, adding water to the crushed ex-situ soil and stirring to obtain slurry; Local dilution and magnetic impurity removal, passing the slurry through the magnetic adsorption area in a flowing form and locally diluting the magnetic adsorption area, and removing the adsorbed impurities in the magnetic adsorption area; Dehydration and detection, dehydrating the slurry after magnetic impurity removal and performing heavy metal detection to determine whether the detection is qualified; Backfilling, backfilling the soil after the detection is qualified.

[0006] In a specific embodiment of the above wet magnetic separation remediation process, there is also a slurry flow pit, the slurry flow pit including a flow part and a dilution part, the dilution part being in the middle part of the flow part, wherein the depth of the dilution part is greater than the depth of the flow part; The step of "passing the slurry through the magnetic adsorption area in a flowing form and locally diluting the magnetic adsorption area" is specifically as follows: The slurry passes through the flow part, the dilution part and the flow part in sequence in the slurry flow pit in a flowing form, and the dilution part is set as the magnetic adsorption area.

[0007] In a specific embodiment of the above wet magnetic separation and repair process, it further includes a plurality of magnetic adsorption rollers. The plurality of magnetic adsorption rollers are arranged in sequence along the direction of slurry flow in the dilution part to form a magnetic adsorption area, and the depths of the plurality of magnetic adsorption rollers in the dilution part decrease in sequence.

[0008] In a specific embodiment of the above wet magnetic separation and repair process, it further includes a dilution water channel arranged at the bottom of the dilution part. The dilution water channel is arranged between adjacent magnetic adsorption rollers, and the water outlet point of the dilution water channel faces the gap between the magnetic adsorption rollers.

[0009] In a specific embodiment of the above wet magnetic separation and repair process, the slurry flow pit includes a first flow pit and a second flow pit. The step of "passing the slurry through the magnetic adsorption area in a flowing form and locally diluting the magnetic adsorption area, and removing impurities adsorbed in the magnetic adsorption area" is further as follows: The slurry passes through the flow part, the dilution part and the flow part in sequence in the first flow pit in a flowing form. The dilution part is set as the magnetic adsorption area to remove impurities from the magnetic adsorption rollers in the first flow pit; The slurry passes through the flow part, the dilution part and the flow part in sequence in the second flow pit in a flowing form. The dilution part is set as the magnetic adsorption area to remove impurities from the magnetic adsorption rollers in the second flow pit.

[0010] In a specific embodiment of the above wet magnetic separation and repair process, the slurry flow rate in the first flow pit is lower than that in the second flow pit, and the depth of the dilution part in the first flow pit is greater than that in the second flow pit.

[0011] In a specific embodiment of the above wet magnetic separation and repair process, the step of "dehydrating the slurry after magnetic impurity removal and performing heavy metal detection to determine whether the detection is qualified" is specifically as follows: The slurry after magnetic impurity removal is dehydrated to form a mud cake, and samples are taken from multiple places on the mud cake for heavy metal detection to determine whether the detection is qualified.

[0012] In a specific embodiment of the above wet magnetic separation and repair process, the following steps are further included between the step of "dehydration detection" and the step of "backfilling": Water recycling and reuse, dewatering of the slurry after magnetic impurity removal, purifying the sewage and then using it for pulp making.

[0013] The working principle and beneficial effects of the present invention are as follows: The present invention discloses a wet magnetic separation repair process for heavy metal slag mixtures, which is used for in-situ repair of the soil in the contaminated area of heavy metal slag mixtures. The existing leaching process cannot be applied. Traditional in-situ soil leaching repair often uses a leaching solution to wash heavy metal ions in the soil, reacts the metal ions with the leaching solution and then washes them out of the soil together with the leaching solution. However, the metals in the heavy metal slag mixture do not exist in the form of ions in the soil of the contaminated area, but in the form of solid particulate waste residues, forming a slag mixture with the soil. Therefore, the traditional leaching process cannot wash the heavy metals out of the soil. In the wet magnetic separation repair process of the present application, after the soil is removed in-situ and pretreated, it is slurried, and then the heavy metal solid particulate waste residues in the slurry are magnetically attracted by wet magnetic separation, and a local dilution process method is used in the magnetic attraction area to make the heavy metal solid particle waste residues in the slurry be magnetically attracted and removed as much as possible. Then, the slurry is dewatered and the heavy metal index is detected. After passing the test, it is backfilled. Through the above solution, the soil in the heavy metal slag contaminated area is repaired with a new idea, improving the repair efficiency and effect of the soil. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The present invention will be further described in detail below with reference to the drawings and specific embodiments.

[0015] Figure 1 is the main process flow chart of the wet magnetic separation repair process in the present invention; Figure 2 is the specific process flow chart of a possible embodiment of the wet magnetic separation repair process in the present invention; Figure 3 is the structural layout diagram of the partial magnetic separation and dilution of the slurry flow pit in the present invention; In the figure: 1. First flow pit, 2. Second flow pit, 3. Magnetic attraction roller, 4. Dilution water channel. SPECIFIC EMBODIMENTS

[0016] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of the present invention.

[0017] Such as Figure 1As shown, the present application proposes a wet magnetic separation repair process for heavy metal muck mixtures, and this repair process includes the following steps: S100: Off-site soil sampling, taking three-dimensional deep soil samples from the marked plot and storing them off-site; S200: Pretreatment, crushing the off-site stored soil; S300: Pulp making, adding water to the crushed off-site soil and stirring to obtain slurry; S400: Local dilution magnetic separation for impurity removal, passing the slurry through the magnetic separation area in a flowing form and locally diluting the magnetic separation area, and removing the adsorbed impurities in the magnetic separation area; S500: Dewatering and detection, dewatering the slurry after magnetic separation for impurity removal and then conducting heavy metal detection to determine whether the detection is qualified; S600: Backfilling, backfilling the soil after the detection is qualified.

[0018] In this embodiment, based on the technical concept of the present application, for the soil pollution of heavy metal slag mixtures, for example, heavy metal pollutants such as arsenic, cadmium, copper, nickel, manganese, vanadium, etc., for the pollution in the state of waste residue, the main form of heavy metal pollution is the corresponding alloy residue state. The above are impurities in the polluted soil and generally difficult to become free state; the residue itself is generally steel slag and iron slag. The ex-situ wet magnetic separation repair process is adopted. First, multi-point sampling of the three-dimensional distribution is carried out on the polluted plot to analyze the pollution area, depth, etc., and the polluted plot is marked. Soil is taken from the marked plot in three-dimensional depth, and the polluted soil is dug out and stored ex-situ. The storage needs to be isolated to avoid ex-situ pollution; the polluted soil stored ex-situ is pretreated. Since the soil conditions at different positions and depths of the soil are different, unified crushing treatment is carried out to make the particle size suitable for the subsequent steps to make slurry. The crushed polluted soil is added with water and stirred to make slurry. The slurry can be continuously made from the actual applied soil to avoid slurry precipitation and affect the repair effect; next, magnetic separation and impurity removal are carried out. In this step, local dilution is required for magnetic separation and impurity removal. Since in the application process of magnetic separation of waste residue, various factors such as the uniformity of the waste residue, the ease of magnetic separation of the waste residue, and the reduction of magnetic separation efficiency caused by the accumulation of waste residue during magnetic separation can all affect the impurity removal effect, local dilution is optimized to cooperate with magnetic separation and impurity removal in the step of magnetic separation of waste residue. Specifically, the slurry is driven by a slurry pump, and the slurry passes through the magnetic separation area in a flowing form, and local dilution is carried out in the magnetic separation area. On the one hand, the slurry is made more dilute, so that magnetic separation can more easily attract heavy metal solid waste residue. On the other hand, through local dilution, the waste residue is relatively more uniform in the slurry, and more thorough impurity removal can be carried out. In addition, on the magnetic separation surface, the accumulation of waste residue is relatively uniform. Therefore, the influence on magnetism is relatively close, and it will not cause excessive decline in local magnetic separation ability and affect the impurity removal effect; further, the use of local dilution can also greatly save water resources, improve quality and increase efficiency. The waste residue separated by magnetic separation needs to be separately purified. The slurry after impurity removal needs to be dehydrated, and then the dehydrated slurry will be subjected to multi-point heavy metal detection to judge whether the detection is qualified. Only when it is qualified can it be backfilled to the marked plot, and thus the soil repair is completed.

[0019] On the basis of the above embodiments, the wet magnetic separation repair process is further optimized. By setting up mud flow pits as carriers for mud flow, the mud flow pits are sequentially arranged as a flow part, a dilution part, and a flow part along the direction of mud flow. The depth of the dilution part is deeper than that of the flow parts on both sides. A plurality of magnetic attraction rollers are arranged inside the dilution part, sequentially arranged along the flow direction, and the depth of the magnetic attraction rollers in the dilution part decreases in sequence. When the mud carrying heavy metal waste residues passes through the dilution part in sequence, whether the waste residues are in the deep layer or the upper layer of the mud can be magnetically attracted, improving the repair efficiency of the soil. It should be noted that the magnetic attraction rollers can be realized in various forms to magnetically attract heavy metal waste residues, and after magnetic attraction is completed, demagnetization or other forms of impurity removal are carried out. After demagnetization, it needs to be remagnetized and then put into the dilution part. Exemplarily, the magnetic attraction rollers adopting the structural form of a permanent magnetic core sleeved with a sleeve can also realize the above scheme; further, two mud flow pits are set, namely a first flow pit and a second flow pit, and based on the amount of waste residues after magnetic separation, the mud flow speed in the first flow pit is less than that in the second flow pit. There are more waste residues in the first mud pit and they pass through relatively slowly. The waste residues in the second mud pit decrease and the waste residue particles decrease, and the speed is relatively increased, and they can also be magnetically attracted cleanly, further improving the magnetic attraction impurity removal rate and the repair effect; local dilution is carried out by setting up dilution water channels in the lower layer area of the rollers in the dilution part. The dilution water channels are provided with a plurality of water outlet points, and the water outlet points face the gaps between adjacent magnetic attraction rollers. When the mud flows through, the water discharged from the dilution water channels dilutes the mud near the magnetic attraction rollers on the one hand, making it easier for heavy metal impurities to be attracted by the magnetic attraction rollers, and on the other hand, it also disturbs the mud flow, making the distribution of heavy metal waste residues more uniform. The water flows in from the gaps between the magnetic attraction rollers and diverges when spraying out from the gaps between the magnetic attraction rollers, further evenly magnetizing the range.

[0020] As Figure 2 and Figure 3 shown, based on the above optimization scheme, the wet magnetic separation repair process in this embodiment includes the following steps: S100: Excavate soil in different locations, take soil from the marked plot in three-dimensional depth and store it in different locations; S200: Pretreatment, crush the soil stored in different locations; S300: Pulp making, add water to the crushed soil in different locations and stir to make pulp; S410: Local dilution and magnetic impurity removal. The mud sequentially passes through the flow part, the dilution part, and the flow part in the first flow pit in a flowing form. The dilution part is set as a magnetic attraction area to remove impurities from the magnetic attraction rollers in the first flow pit; S420: The mud sequentially passes through the flow part, the dilution part, and the flow part in the second flow pit in a flowing form. The dilution part is set as a magnetic attraction area to remove impurities from the magnetic attraction rollers in the second flow pit; S500: Dehydrate the slurry after magnetic impurity removal to form mud cakes, take samples from multiple locations on the mud cakes for heavy metal detection, and determine whether the detection is qualified. S600: Recycle and reuse water. Dehydrate the slurry after magnetic impurity removal, purify the sewage, and then use it for pulp making. S700: Backfill. After passing the detection, backfill the soil.

[0021] In this embodiment, during the local dilution magnetic impurity removal process, it is further refined to perform magnetic impurity removal step by step in the first flow pit and the second flow pit respectively. After impurity removal and dehydration, mud cakes are made for multiple sampling detections until the detection is qualified. It should be noted that this process also purifies the sewage after slurry dehydration and then uses it for pulp making to achieve water cycle utilization. Therefore, this process is relatively water-saving both in terms of local dilution wet magnetic separation repair and water cycle reuse, and is more environmentally friendly while repairing the soil. When the soil passes the detection, break up and backfill the marked plot. After the heavy metal impurities are recovered, they are recycled for resource utilization to achieve waste-free repair.

[0022] It should be noted that the above specific implementation process is one possible implementation manner under the premise of the technical concept of this application. During actual application, the number of slurry flow pits, depth, number of magnetic rollers, dilution degree, etc. can be increased or decreased according to the actual pollution situation. Of course, the above parameters that can be changed according to actual application are only examples. It should be understood that under the premise of the technical concept of this application, there should be more specific step implementation manners, and just making simple parameter changes should fall within the protection scope of this application.

[0023] Exemplarily, taking one of the possible contaminated target plots as an example for elaboration, the heavy metal pollutants manganese and vanadium in this target plot exceed the standard. The original pollution concentrations of manganese and vanadium are 5000 mg / kg and 250 mg / kg respectively, and the remediation targets for manganese and vanadium are 2930 mg / kg and 165 mg / kg respectively. The soil pollution situation after traditional leaching remediation is as follows. After screening the soil according to different particle sizes and detecting, in the soil with a particle size ≥ 2 mm, the pollution concentrations of manganese and vanadium are 4500 mg / kg and 225 mg / kg respectively; in the soil with a particle size of 0.075 - 2 mm, the pollution concentrations of manganese and vanadium are 6000 mg / kg and 300 mg / kg respectively; in the soil with a particle size < 0.075 mm, the pollution concentrations of manganese and vanadium are 3900 mg / kg and 190 mg / kg respectively. For the soil pollution situation after the wet magnetic separation remediation process of this application, it is still detected after screening the soil according to different particle sizes. In the soil with a particle size ≥ 2 mm, the pollution concentrations of manganese and vanadium are 1500 mg / kg and 35 mg / kg respectively, and for the waste residue magnetically separated under the corresponding particle size, the pollution concentrations of manganese and vanadium are 6900 mg / kg and 377 mg / kg respectively; in the soil with a particle size of 0.075 - 2 mm, the pollution concentrations of manganese and vanadium are 1900 mg / kg and 75 mg / kg respectively, and for the waste residue magnetically separated under the corresponding particle size, the pollution concentrations of manganese and vanadium are 8460 mg / kg and 435 mg / kg respectively; in the soil with a particle size < 0.075 mm, the pollution concentrations of manganese and vanadium are 1950 mg / kg and 93 mg / kg respectively, and for the waste residue magnetically separated under the corresponding particle size, the pollution concentrations of manganese and vanadium are 4875 mg / kg and 237 mg / kg respectively. It can be seen that the traditional leaching remediation process can basically not effectively remove the pollutants in the heavy metal soil mixture, and the pollutants in the soil mixture mainly exist in its alloy waste residue. Through the remediation process of this application, the heavy metal pollutants in the soil can be reduced to below the remediation target value and the reduction degree is significant, which also precisely proves that for the plots with the main pollution type of heavy metal - contaminated soil being the soil mixture, their pollution sources are also concentrated in the waste residue, and the remediation process of this application can effectively repair it.

[0024] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A heavy metal slag mixture wet magnetic separation repair process, characterized in that: The repair process comprises the following steps: Ex situ soil sampling: soil is sampled from the marked plots in three dimensions and stored in an ex situ manner; Pretreatment: crushing of soil stored ex situ; Pulping, adding water to the crushed ex situ soil and stirring it to make mud; Local dilution magnetic absorption and impurity removal: the mud is passed through the magnetic absorption area in a flowing form and the magnetic absorption area is locally diluted to remove the impurities adsorbed in the magnetic absorption area; Dehydration test: dehydrate the mud after magnetic impurity removal and then conduct heavy metal test to determine whether it is qualified; Backfill: backfill the soil after passing the inspection.

2. The heavy metal slag mixture wet magnetic separation repair process according to claim 1, characterized in that: Also included is a mud flow pit, the mud flow pit includes a flow portion and a dilution portion, the dilution portion is in the middle of the flow portion, wherein the depth of the dilution portion is greater than the depth of the flow portion; The step of "flowing the slurry through the magnetic attraction area and locally diluting the magnetic attraction area" is specifically as follows: The mud in the mud flow pit sequentially passes through the flow part, the dilution part and the flow part in the form of flow, and the dilution part is provided with a magnetic attraction area.

3. The heavy metal slag mixture wet magnetic separation repair process according to claim 2 is characterized in that: It also includes a plurality of magnetic rollers, which are sequentially arranged in the dilution section along the direction of slurry flow to form a magnetic attraction area, and the depths of the plurality of magnetic rollers in the dilution section decrease sequentially.

4. The heavy metal slag mixture wet magnetic separation repair process according to claim 3 is characterized in that: It also includes a dilution water channel arranged at the bottom of the dilution part, wherein the dilution water channel is arranged between adjacent magnetic suction rollers, and a water outlet point of the dilution water channel faces the gap between the magnetic suction rollers.

5. The heavy metal slag mixture wet magnetic separation repair process according to claim 4, characterized in that: The mud flow pit includes a first flow pit and a second flow pit, and the step of "flowing the mud through the magnetic attraction area and partially diluting the magnetic attraction area, and removing impurities adsorbed in the magnetic attraction area" is further: The slurry flows in the first flow pit in the form of a flow through the flow part, the dilution part and the flow part in the first flow pit in sequence, and the dilution part is provided with a magnetic attraction area to remove impurities from the magnetic attraction roller in the first flow pit; The mud flows in the second flow pit in the form of flow through the flow part, the dilution part and the flow part in the second flow pit in sequence. The dilution part is set as a magnetic attraction area to remove impurities from the magnetic attraction roller in the second flow pit.

6. The heavy metal slag mixture wet magnetic separation repair process according to claim 5, characterized in that: The mud flow velocity in the first flow pit is lower than the mud flow velocity in the second flow pit, and the depth of the dilution portion in the first flow pit is greater than the depth of the dilution portion in the second flow pit.

7. The heavy metal slag mixture wet magnetic separation repair process according to claim 6, characterized in that: The step of "dehydrating the mud after magnetic impurity removal and then conducting heavy metal detection to determine whether the detection is qualified" is specifically as follows: The mud after magnetic decontamination is dehydrated to make mud cakes, and samples are taken from multiple locations on the mud cakes for heavy metal testing to determine whether they are qualified.

8. The heavy metal slag mixture wet magnetic separation repair process according to claim 1 or 7, characterized in that: The following steps are also included between the step "dehydration detection" and the step "backfilling": Water is recycled and reused, the mud is dehydrated after magnetic dewatering, and the sewage is purified before being used for pulping.

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