A method for preparing a green planting soil from a landfill humus by segmental selective strengthening water washing and products and applications thereof

Abstract

The application provides a method for preparing green planting soil from landfill humus by section selective strengthening water washing, and products and applications thereof. Pretreated humus is sequentially subjected to primary coarse washing, secondary strengthening washing and tertiary fine washing, and the humus and washing water are counter-flowed; the slurry obtained by the primary coarse washing is flocculated by a soil-friendly composite flocculant, and then subjected to solid-liquid separation, the first wet soil cake is washed by the tertiary fine washing effluent containing a chemical strengthening treatment system, the salt-rich washing liquid is subjected to separate treatment by ultrafiltration and nanofiltration, the recycled water is returned to the water washing process, the homologous organic matter concentrated components are returned to the humus after water washing, the salt-rich concentrated liquid is subjected to evaporation crystallization, the obtained crystalline salt is recovered as salt, the evaporation condensate water is recycled for water washing, and the high-salt mother liquor is returned to the salt-rich concentrated liquid; the humus after water washing is dehydrated and homogenized, and then used as green planting soil. The application realizes desalination, decontamination, water recycling, homologous organic matter recycling and salt recovery of humus.

Description

Technical Field

[0001] This invention belongs to the technical fields of landfill excavation and remediation, resource utilization of screening products, pollution control, and preparation of soil for greening and planting. Specifically, it relates to a method for preparing soil for greening and planting by selectively and intensively washing humus soil from landfills in stages, as well as its products and applications. Background Technology

[0002] As urban solid waste landfills in my country gradually enter the stages of closure and remediation, capacity reduction, excavation and treatment, and ecological restoration, the demand for safe disposal and resource utilization of existing landfill waste is becoming increasingly prominent. Solid waste landfills have long received municipal solid waste and undergone anaerobic degradation, humification, and mineralization stabilization processes, resulting in the accumulation of organic matter, mineral particles, soluble salts, heavy metals, and various organic pollutants within the landfill. Excavation and remediation of landfills can release capacity, reduce pollution risks, and promote land reuse. However, during excavation, temporary storage, screening, transfer, and the utilization and disposal of screening products, secondary environmental problems such as leachate spillage, pollutant migration, and groundwater risks may still occur.

[0003] During the excavation and screening process at landfills, a large amount of humus is generated as the undersize fine-grained product. This material has a certain amount of humified organic matter, mineral particles, and nutrient base, and has the potential to be used to prepare soil for greening, ecological restoration, and landfill cover improvement. However, landfill humus has a complex origin and fluctuates greatly in composition, often containing stones, plastics, glass, ceramics, metals, and other inert impurities. It also contains high levels of soluble salts, some reactive heavy metals, and organic micropollutants such as polycyclic aromatic hydrocarbons (PAHs), phthalates, phenols, surfactants, and antibiotics. Among these, persistent organic pollutants such as PAHs have carcinogenic, mutagenic, and teratogenic effects, and high-ring PAHs are difficult to remove using conventional physical methods. If used directly as soil without effective treatment, it can easily cause salt damage and inhibit plant growth, and lead to the migration and accumulation of pollutants in the soil-plant system, thereby causing long-term soil environmental risks and ecological security hazards.

[0004] Among existing technologies for the harmless treatment of humus, conventional water washing is a common method for removing soluble salts, but it still has the following significant shortcomings: First, conventional water washing mainly relies on dissolution and diffusion, and its ability to remove hydrophobic organic micropollutants such as polycyclic aromatic hydrocarbons is limited; second, if the intensity of the water washing is increased or the washing time is extended to improve the desalination effect, the consumption of fresh water and the amount of high-salinity washing liquid will increase significantly; in addition, the water washing process will also carry out some dissolved organic matter, humus colloids and fine particulate organic matter, reducing the water retention and fertilizer retention capacity of the humus after water washing; finally, salt, organic matter and pollutants coexist in the washing liquid, and if it is directly discharged or simply treated, it will significantly increase the difficulty and operating cost of subsequent wastewater treatment, and it is difficult to achieve the recycling of the washing liquid.

[0005] To overcome the limitations of water washing processes, several alternative technologies have been developed for the treatment of humus. Chinese patent CN109454091A discloses a method for treating humus from aged landfills using a combination of aerobic composting and leaching. By adjusting the carbon-to-nitrogen ratio and inoculating with aerobic acid-producing microorganisms for composting, followed by multiple leaching processes with organic acid solutions and water, the organic matter, salt content, and heavy metal content in the humus can be reduced simultaneously. Another Chinese patent CN114702296A discloses a method for using humus from aged landfills for brick making. The humus is crushed and screened, mixed with clay mineral additives and construction waste, and then aged, dried, and sintered at temperatures above 600℃ to produce bricks, effectively controlling salt content, organic matter, and heavy metals. Furthermore, Chinese patent CN107350275A uses a cement kiln to co-process humus and plastics from aged waste, utilizing the heat energy from plastic combustion for thermal desorption treatment of the humus. However, the above methods may have problems such as long processing cycles, high energy consumption, and large equipment investment, or they may focus on the fixation and removal of single pollutants, making it difficult to simultaneously achieve the synergistic effect of enhanced desalination, removal of organic micropollutants, and retention of beneficial organic matter.

[0006] Therefore, there is an urgent need to develop a segmented selective enhanced washing method for landfill humus, which can effectively remove salt while also enhancing the removal of organic micropollutants, retain the organic matter components in the humus to the maximum extent, and simultaneously achieve the classification and recycling of the washing solution, thereby realizing the safe and efficient resource utilization of landfill humus. Summary of the Invention

[0007] The purpose of this invention is to provide a method for preparing landscaping planting soil by staged selective enhanced water washing of humus soil from landfills, along with its products and applications. Specifically, through a combined strategy of humus soil pretreatment, staged selective enhanced water washing, solid-liquid separation, graded treatment of the washing liquid, reuse and salt recovery, and recovery and reprocessing of homologous organic matter, this method achieves efficient migration of soluble salts in landfill humus soil, synergistic reduction of organic micropollutants, recycling of the washing liquid, and recovery of homologous organic matter, thereby obtaining humus soil products that can be directly used for landscaping planting. This invention effectively solves the problems of high salt content, high risk of micropollutants, high water consumption in the washing process, heavy burden of washing liquid treatment, and loss of organic matter in humus soil after washing during the resource utilization of landfill humus soil in existing processes.

[0008] To achieve the above objectives, the present invention provides a method for preparing planting soil for landscaping by selectively and progressively washing humus from landfills, comprising the following steps:

[0009] (1) Humus pretreatment: Humus from landfills is removed by sieving, screening and magnetic separation to remove non-soil impurities and obtain pretreated humus.

[0010] In a preferred embodiment, the humus soil derived from the landfill specifically includes one or more of the following: undersize fine particles obtained during the excavation and remediation of municipal solid waste landfills, mineralized waste fine particles, humification screening products, and stabilized landfill fine particles.

[0011] In a preferred embodiment, the non-soil impurities include one or more of the following: stones, plastics, glass, ceramics, tree branches, ferromagnetic metals, and other mechanical impurities.

[0012] In a preferred embodiment, the screening is performed using a vibrating screen and / or a drum screen; the particle size of the humus after screening is less than 10 mm; preferably, the particle size is less than 5 mm; more preferably, the particle size is less than 2 mm.

[0013] In a preferred embodiment, the magnetic separation employs one or more of a drum magnetic separator, a belt magnetic separator, and a suspended magnetic separator; the magnetic field strength of the magnetic separation is 800-3000 Gs to remove ferromagnetic metal impurities.

[0014] (2) Segmented selective enhanced washing: The pretreated humus is sequentially fed into a primary coarse washing unit, a secondary enhanced washing unit, and a tertiary fine washing unit. The direction of feeding the humus is opposite to the direction of the washing water flow. Specifically, this includes:

[0015] In the primary coarse washing unit, after the pretreated humus soil is washed with secondary enhanced washing water, the resulting coarse washing slurry is transferred to the solid-liquid separation unit. After adding composite flocculant for flocculation and sedimentation, centrifugation or pressure filtration, the first wet soil cake and salt-rich washing liquid are obtained.

[0016] In the secondary enhanced washing unit, after washing the first wet soil cake with the tertiary fine washing effluent and chemical enhanced treatment system, the enhanced washing slurry obtained by sedimentation is used to obtain the second wet soil cake and the secondary enhanced washing effluent.

[0017] In the three-stage washing unit, after washing the second wet soil cake with fresh water or recycled water, the resulting washing slurry is separated to obtain the third wet soil cake and the third-stage washing effluent.

[0018] In this invention, the primary coarse washing unit is mainly used to remove soluble salts from the humus raw material, and the resulting brine washing solution contains high concentrations of salts and organic micro-pollutants removed by the secondary enhanced washing. The secondary enhanced washing unit is mainly used for chemically enhanced decontamination under a medium salinity background. The tertiary fine washing unit mainly uses fresh water or recycled water to further reduce the residual salt content of the humus.

[0019] By implementing the segmented design described above, the ineffective consumption of oxidants during the primary high-salt, high-impurity stage can be avoided. Furthermore, residual oxidants in the final washing water can prevent them from affecting the suitability of the washed humus soil for landscaping, effectively achieving a synergistic balance between desalination, decontamination, and product safety. In addition, by placing the chemical enhancement treatment system in the secondary enhanced washing unit, while maintaining the organic matter content of the humus soil, it can also oxidize and degrade or structurally destroy polycyclic aromatic hydrocarbons, phthalates, phenolic compounds, antibiotics, surfactants, petroleum hydrocarbons, and other oxidizable organic micropollutants, thereby reducing the environmental risks during the land use of humus soil.

[0020] In a preferred embodiment, in each washing unit, the solid-liquid mass ratio of single-stage humus to washing water is 1:(1-5), the single-stage washing time is 10-240 min, the washing temperature is 10-60℃, and the washing stirring speed is 50-500 rpm.

[0021] Preferably, the solid-liquid mass ratio of a single stage is 1:(2-3), the single-stage water washing time is 30-120 min, the water washing temperature is 20-40℃, and the water washing stirring speed is 100-300 rpm;

[0022] More preferably, the water washing method during the initial operation of the system of the present invention includes: washing the pretreated humus soil with fresh water in the primary coarse washing unit, then transferring the resulting coarse washing slurry to the solid-liquid separation unit, adding a composite flocculant for flocculation and sedimentation, centrifugation or pressure filtration, to obtain a first wet soil cake and a salt-rich washing liquid; sending the first wet soil cake to the secondary enhanced washing unit, washing it with fresh water and a chemical enhanced treatment system, settling the resulting enhanced washing slurry, to obtain a second wet soil cake and secondary enhanced washing effluent; sending the second wet soil cake to the tertiary fine washing unit, washing it with fresh water, separating the resulting fine washing slurry, to obtain a third wet soil cake and tertiary fine washing effluent; collecting the effluent from each stage allows for subsequent water washing steps where the direction of humus soil input is opposite to the direction of the washing water flow.

[0023] In a preferred embodiment, in the solid-liquid separation unit, the composite flocculant comprises chitosan, humate, and calcium-based mineral materials in a mass ratio of 1:(1-5):(5-20); the dosage of the composite flocculant is 0.05%-1% of the dry basis mass of the coarse washing slurry; and the flocculation and settling time is 10-60 min.

[0024] Preferably, the humate comprises sodium humate and / or potassium humate; the calcium-based mineral material comprises one or more of gypsum, calcium carbonate, dolomite powder, and calcium-magnesium mineral powder.

[0025] Preferably, the composite flocculant further includes one or more of the following: modified starch, guar gum, xanthan gum, alginate, bio-flocculator, lignin sulfonate, and low-residue monomeric anionic polyacrylamide.

[0026] Preferably, the centrifugation or filtration parameters after flocculation and sedimentation include: a centrifugation speed of 1000-5000 rpm and a centrifugation time of 5-30 min; and a filtration pressure of 0.2-1.0 MPa and a filtration time of 10-60 min.

[0027] In designing the composite flocculant, chitosan is used to promote the flocculation and sedimentation of colloids and fine organic matter in humic soil; humate is used to supplement humic components and improve the aggregate structure of humic soil after washing; and calcium-based mineral materials are used to promote particle aggregation and help mitigate the risk of exchangeable sodium. This invention, through the synergistic treatment of the above-mentioned composite flocculant, not only improves solid-liquid separation efficiency but also reduces the adverse effects of residual flocculants from traditional inorganic water treatment on the suitability of soil for landscaping.

[0028] In a preferred embodiment, in the secondary enhanced washing unit, the chemical enhanced treatment system includes one or more of the following: an alkaline activated hydrogen peroxide system, a Fenton system, and a potassium persulfate activation system;

[0029] Preferably, the alkaline-activated hydrogen peroxide system comprises hydrogen peroxide and an alkaline substance, wherein the alkaline substance comprises one or more of sodium carbonate, sodium bicarbonate, sodium hydroxide, potassium hydroxide, lime, or wood ash extract; more preferably, the method for adding the alkaline-activated hydrogen peroxide system comprises: first adding hydrogen peroxide to the tertiary washing effluent to make its mass percentage in the tertiary washing effluent 0.05%-2.0%, then adding an alkaline substance to adjust the pH of the system to 8.5-11.0; after washing, reducing the residual hydrogen peroxide to below 50 mg / L, and then performing sedimentation and separation;

[0030] Preferably, the Fenton system comprises hydrogen peroxide and ferrous sulfate; more preferably, the method of adding the Fenton system comprises: first adding an acidic substance to the tertiary washing effluent to adjust the pH of the system to 3.8-4.2, then adding hydrogen peroxide and ferrous sulfate, wherein the mass percentage of hydrogen peroxide in the tertiary washing effluent is 0.05%-5%, and the amount of ferrous sulfate added is 0.01%-2% of the mass of the first wet soil biscuit base; most preferably, after washing, an alkaline substance is added to adjust the pH of the system to 7.2-7.8, and then sedimentation and separation are performed;

[0031] Preferably, the potassium persulfate activation system comprises potassium persulfate and an activator; the amount of potassium persulfate added is 0.5-1.5% of the mass of the first wet soil biscuit base; the activator is one or more of the following: ferrous salt (such as ferrous sulfate, ferrous chloride), iron oxide (such as ferric oxide, ferric oxide), alkaline substance (such as sodium carbonate, sodium bicarbonate, sodium hydroxide, potassium hydroxide, lime, wood ash extract), thermal activation conditions, or ultraviolet activation conditions; more preferably, the amount of ferrous salt added is 0.01%-1.0% of the mass of the first wet soil biscuit base, and the amount of iron oxide added is 0.05%-2.0% of the mass of the first wet soil biscuit base; the amount of alkaline substance added for activation is to adjust the pH of the system to 8.0-10.5; when using thermal activation, the system temperature is 30-60℃; when using ultraviolet activation, the ultraviolet wavelength is 254-365 nm. nm; the most preferred method is to add an alkaline substance after washing to adjust the pH of the system to 7.2-7.8, and then carry out sedimentation and separation.

[0032] In a preferred embodiment, the settling time after washing in the secondary enhanced washing unit is 10-30 minutes.

[0033] In a preferred embodiment, in the three-stage washing unit, the recycled water includes the membrane permeate recycled water from step (3) or the evaporated condensate from step (3). Preferably, the separation method includes centrifugation or pressure filtration. More preferably, the centrifugation speed is 1000-5000 rpm and the centrifugation time is 5-30 min; the pressure filtration pressure is 0.2-1.0 MPa and the pressure filtration time is 10-60 min.

[0034] (3) Separation, reuse and salt recovery of rich brine washing solution: The rich brine washing solution is subjected to sedimentation, filtration, ultrafiltration, nanofiltration and evaporation crystallization in sequence;

[0035] In the ultrafiltration step, the obtained ultrafiltration retentate is used as a homologous organic matter concentration component for homologous organic matter recovery and recombination, and the ultrafiltration permeate is subjected to nanofiltration treatment.

[0036] In the nanofiltration step, the obtained nanofiltration permeate is used as membrane permeate recycled water in the tertiary washing unit, and the nanofiltration concentrate is used as a salt-rich concentrate for evaporation and crystallization.

[0037] In the evaporation and crystallization step, the obtained crystallized salt is recovered as salt, the evaporation condensate is reused in the three-stage fine washing unit, and the high-salt mother liquor is refluxed to the salt-rich concentrate for repeated evaporation and crystallization.

[0038] In a preferred embodiment, the ultrafiltration treatment uses an ultrafiltration membrane with a molecular weight cutoff of 1-100 kDa and an operating pressure of 0.1-0.3 MPa to retain humic acid-like substances, fulvic acid-like substances, humic colloids, and fine particulate organic matter in the washing solution.

[0039] In a preferred embodiment, the nanofiltration treatment uses a nanofiltration membrane with a molecular weight cutoff of 150-500 Da and an operating pressure of 0.5-2.0 MPa.

[0040] In a preferred embodiment, the method further includes: when any one of the following indicators of the high-salt mother liquor—conductivity, soluble chlorine, total dissolved solids, and chemical oxygen demand—exceeds a set threshold, the mother liquor is discharged through a salt discharge bypass; preferably, the set threshold includes: conductivity of 80-200 mS / cm, soluble chlorine of 30-100 g / L, total dissolved solids of 80-250 g / L, and chemical oxygen demand of 2000-20000 mg / L; more preferably, when the high-salt mother liquor meets any one of the following conditions: conductivity higher than 120 mS / cm, soluble chlorine higher than 50 g / L, total dissolved solids higher than 150 g / L, and chemical oxygen demand higher than 10000 mg / L, the salt discharge bypass is activated, a portion of the high-salt mother liquor is sent to the treatment and discharge unit, and the remaining high-salt mother liquor is returned to the salt-rich concentrate for further evaporation and crystallization.

[0041] In this invention, water, salt, and homologous organic matter in the washing liquid are separated and controlled through ultrafiltration and nanofiltration. The nanofiltration permeate is used as recycled water, achieving water resource recycling; the nanofiltration concentrate, as a salt-rich concentrate, enters the evaporation and crystallization unit, where the obtained crystalline salt is recovered, the evaporation condensate is reused, and the high-salt mother liquor is returned to the salt-rich concentrate. If necessary, it is discharged through a salt bypass treatment, thus achieving salt enrichment, crystallization recovery, and water resource recycling. Simultaneously, the ultrafiltration retentate serves as a concentrated component of homologous organic matter, providing a source for subsequent organic matter reprocessing. Through this separation and control, this invention minimizes wastewater discharge and fully realizes resource recycling.

[0042] (4) Homologous organic matter recovery and remixing: The homologous organic matter concentrate in step (3) is washed and dehydrated, and then remixed into the third wet soil cake in step (2) in proportion.

[0043] In a preferred embodiment, the washing uses a low-salt water with a conductivity not higher than 0.90 mS / cm; preferably, the low-salt water includes nanofiltration permeate, evaporated condensate, fresh water, or a combination thereof; more preferably, the low-salt water washes the homologous organic matter concentrate until its conductivity is not higher than 2.0 mS / cm.

[0044] In a preferred embodiment, the dehydration to a moisture content of 40%-70% can be carried out using conventional methods known to those skilled in the art, such as centrifugation, pressure filtration, or natural drainage.

[0045] In a preferred embodiment, the remixing ratio is: the dehydrated homologous organic matter concentrate is 5%-15% of the mass of the third wet soil biscuit base.

[0046] In this invention, the ultrafiltration retentate in step (3) mainly retains macromolecular substances in the washing liquid. In step (4), it is used as a homologous organic matter concentrate for reprocessing, which can compensate for dissolved organic matter, humic colloids, and fine particulate organic matter carried out during the washing process, thereby improving the organic matter retention rate, aggregate structure stability, and water and fertilizer retention capacity of the humus soil after washing. Compared with exogenous organic matter conditioning, homologous organic matter reprocessing has the advantages of consistent source, low environmental risk, and high degree of resource closure.

[0047] (5) Product acquisition: Dehydrate and mix the mixed humus obtained in step (4) to obtain soil products for greening and planting.

[0048] In a preferred embodiment, the obtained greening planting soil product has a soluble salt removal rate of over 60%, a polycyclic aromatic hydrocarbon removal rate of over 75%, and an organic matter retention rate of over 86% compared to humus raw materials.

[0049] In a preferred embodiment, the control indicators of the soil product for greening planting include pH, salinity or electrical conductivity, organic matter, soil infiltration rate, germination index, soluble chlorine, exchangeable sodium, sodium adsorption ratio, heavy metal concentration, and organic micropollutant content; wherein, pH, salinity or electrical conductivity, organic matter, soil infiltration rate, germination index, soluble chlorine, exchangeable sodium, sodium adsorption ratio, and heavy metal concentration meet the technical requirements of the corresponding application scenario in "Greening Planting Soil" (CJ / T 340—2016), and the organic micropollutant content is controlled according to the environmental safety requirements of the target application scenario.

[0050] The present invention also provides a soil product for greening and planting prepared by any of the methods described above.

[0051] The present invention also provides the application of the above-mentioned soil products for greening and planting in landscaping, road greening, slope ecological restoration, mine revegetation, site closure greening, site ecological restoration or seedling cultivation.

[0052] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0053] (1) In terms of processing technology, existing humus washing mainly adopts single-stage or ordinary multi-stage washing, which mainly relies on dissolution and diffusion to remove salts, making it difficult to simultaneously reduce micro-pollutants and retain organic matter. This invention adopts a segmented selective washing structure of primary coarse washing, secondary enhanced washing and tertiary fine washing, so that salt migration, micro-pollutant reduction and terminal fine washing are completed in different functional units, effectively reducing the consumption of fresh water and the amount of washing liquid generated.

[0054] (2) In terms of pollutant control, the present invention sets up a chemical enhancement treatment system in a secondary enhanced washing unit to oxidize and degrade organic micropollutants under a medium salinity background. This avoids the ineffective consumption of oxidants in the high-salt and high-impurity coarse washing stage and reduces the impact of residual oxidants in the final fine washing stage on the applicability of the finished soil.

[0055] (3) In terms of solid-liquid separation, the present invention uses chitosan, humic acid salt and calcium-based mineral materials to prepare a soil-friendly composite flocculant, which not only promotes solid-liquid separation of humic soil slurry, but also improves the aggregate structure of humic soil after water washing, alleviates the risk of exchangeable sodium, and improves its product quality as soil for greening and planting.

[0056] (4) Regarding the resource utilization of washing liquid, this invention achieves fractional treatment of washing liquid through ultrafiltration and nanofiltration, obtaining homologous organic matter concentrated components, membrane permeate recycled water, and salt-rich concentrated liquid respectively. Among them, the homologous organic matter concentrated components are recycled back to the humus soil after washing, the membrane permeate recycled water is returned to the tertiary fine washing unit, and the salt-rich concentrated liquid enters the evaporation and crystallization unit for salt recovery. The crystallized salt generated during the salt recovery process is recovered, the evaporation condensate is reused in the washing process, and the high-salt mother liquor is returned to the salt-rich concentrated liquid. If necessary, it is discharged through a salt bypass treatment. Through the above-mentioned diversion control, while realizing organic matter recycling, water circulation, and salt recovery, it can also reduce the external discharge of washing liquid and the burden of subsequent treatment, and the overall process is green and environmentally friendly.

[0057] (5) Regarding the products obtained, the humus obtained by this invention, after being washed and dehydrated and homogenized, can be safely used as a soil product for greening and planting. This reduces the risks of salt damage, pollutant migration and ecological risks caused by direct land use of humus, and improves the resource utilization level of landfill excavation and screening products, thus achieving synergistic effects of pollution control, resource recycling and land use. Attached Figure Description

[0058] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0059] Figure 1 A schematic diagram of the overall process flow for preparing planting soil for landfills using selectively enhanced water washing of humus soil. Detailed Implementation

[0060] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. However, it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0061] This invention provides a method for preparing landscaping planting soil from landfill humus through segmented selective enhanced water washing, along with its products and applications. Using this method, salts primarily enter the salt-rich liquid phase, while organic micropollutants are reduced in the enhanced washing unit. Humus components are separated by membrane separation and then returned to the washed humus soil. The washing water is recycled for the final fine washing stage. This reduces the land use risk of humus soil while minimizing water consumption and maintaining its organic matter content. The resulting washed humus soil, after dehydration and homogenization, can be safely used directly as landscaping planting soil. This effectively solves the problem in existing technologies where desalination, decontamination, water conservation, and organic matter retention of landfill humus soil are difficult to achieve simultaneously, realizing multiple benefits such as water resource recycling, salt crystallization recovery, and humus component recovery.

[0062] In this invention, "washing water" refers to fresh water entering the washing unit, membrane permeate recycled water, evaporation and condensation recycled water, or a combination thereof; "homogeneous organic matter concentrated component" refers to the component rich in dissolved organic matter, humic colloids, and fine particulate organic matter obtained from the humus washing liquid through sedimentation, filtration, and ultrafiltration; "homogeneous organic matter re-mixing" refers to re-mixing the above components into the washed humus after low-salt washing and dehydration.

[0063] In this invention, the weight parts can be weight units known in the art such as μg, mg, g, kg, or multiples thereof, such as 1 / 10, 1 / 100, 10 times, 100 times, etc.

[0064] Unless otherwise specified, the technical means used in this invention are conventional means well known to those skilled in the art. All raw materials, reagents, instruments, and equipment used in this invention can be purchased commercially or prepared using existing methods. Unless otherwise specified, all reagents used in this invention are of analytical grade.

[0065] Example 1

[0066] A method for preparing planting soil for landfill humus using an alkali-activated hydrogen peroxide system through segmented selective enhanced water washing includes the following steps:

[0067] 1. Humus pretreatment:

[0068] Humus soil obtained from the excavation and screening of a municipal solid waste landfill was first manually sorted to remove large pieces of plastic, glass, stones, ceramics, and branches and leaves. Then, it was screened by a vibrating screen. The screened material was then magnetically separated by a drum magnetic separator to remove ferromagnetic metal impurities, resulting in pretreated humus soil. The humus soil after screening was smaller than 5 mm, and the magnetic separation magnetic field strength was 1500 Gs.

[0069] The initial pH of the original humus soil used in this embodiment was 7.82, EC was 7.20 mS / cm, soluble chlorine was 520 mg / L, exchangeable sodium was 265 mg / kg, sodium adsorption ratio was 8.6, total polycyclic aromatic hydrocarbons were 450 μg / kg, organic matter was 26.5 g / kg, soil infiltration rate was 3.2 mm / h, and germination index was 38%.

[0070] 2. Segmented selective enhanced washing:

[0071] The system consists of a primary coarse washing unit, a secondary enhanced washing unit, and a tertiary fine washing unit. The humus soil sequentially passes through these three units; the washing water flows in opposite directions, specifically including:

[0072] The pretreated humus is sent to the primary coarse washing unit and washed with secondary enhanced washing water. The resulting coarse washing slurry is transferred to the solid-liquid separation unit, where a composite flocculant is added for flocculation, sedimentation, and pressure filtration to separate the first wet soil cake and the salt-rich washing liquid.

[0073] The rich saline washing solution is sent to the rich saline washing solution separation treatment unit; the first wet soil cake is sent to the second-level enhanced washing unit, where the wet soil cake is washed with the tertiary fine washing effluent and chemical enhanced treatment system, and the enhanced washing slurry obtained by sedimentation is used to obtain the second wet soil cake and the second-level enhanced washing effluent.

[0074] The secondary enhanced washing effluent is sent to the primary coarse washing unit; the second wet soil cake is sent to the tertiary fine washing unit, where the wet soil cake is washed with fresh water, and the resulting fine washing slurry is separated to obtain the third wet soil cake and the tertiary fine washing effluent.

[0075] The effluent from the third-stage fine washing is sent to the second-stage enhanced washing unit; the third-stage wet soil cake is sent to the homogeneous organic matter recovery and reprocessing unit.

[0076] 2.1 Washing conditions:

[0077] In each washing unit, the solid-liquid mass ratio of single-stage humus to washing water is 1:3, the washing temperature is 25℃, the single-stage stirring time is 60 min, and the stirring rate is 200 rpm.

[0078] 2.2 In the solid-liquid separation unit:

[0079] A soil-friendly composite flocculant composed of chitosan, sodium humate, and gypsum powder was added to the coarse washing slurry. The mass ratio of chitosan, sodium humate, and gypsum powder was 1:3:10, and the dosage was 0.2% of the dry weight of the coarse washing slurry. The flocculation time was 30 min. Then, the mixture was filtered at 0.5 MPa for 30 min to obtain the first wet soil cake and the salt-rich washing liquid.

[0080] 2.3 In the secondary enhanced washing unit:

[0081] The effluent from the tertiary rinsing is added to the secondary enhanced rinsing unit, and an alkaline-activated hydrogen peroxide system composed of hydrogen peroxide and sodium carbonate is added. Specifically, hydrogen peroxide is first added to the effluent from the tertiary rinsing to make its mass percentage in the effluent from the tertiary rinsing 0.6%, and then the pH of the system is adjusted to 10.0 with sodium carbonate.

[0082] The first wet soil cake is fed in and washed under the water washing conditions in 2.1 to cause some of the oxidizable organic micro-pollutants in the humus to undergo oxidative degradation, while promoting colloidal depolymerization and soluble salt migration.

[0083] After washing, the residual hydrogen peroxide was reduced to below 50 mg / L, and the mixture was allowed to settle for 20 min to separate the second wet soil cake and the secondary enhanced wash water.

[0084] 3. Separate treatment of saline wash solution:

[0085] After the primary coarse washing is flocculated and settled, the rich brine washing liquid obtained is settled again for 20 minutes. The liquid phase is collected and filtered to remove large suspended solids. The resulting filtrate enters the ultrafiltration unit.

[0086] The ultrafiltration membrane has a molecular weight cutoff of 10 kDa and an operating pressure of 0.20 MPa, producing ultrafiltration retentate and ultrafiltration permeate. The ultrafiltration retentate is used as a homologous organic matter concentration component for homologous organic matter recovery and reprocessing, while the ultrafiltration permeate enters the nanofiltration unit.

[0087] The nanofiltration membrane has a molecular weight cutoff of 200 Da, an operating pressure of 2.0 MPa, and a nanofiltration permeate recovery rate of 70%, yielding nanofiltration permeate and nanofiltration concentrate. The nanofiltration permeate with an EC value below 0.90 mS / cm is returned to the tertiary washing unit as recycled water, while the nanofiltration concentrate is used as a salt-rich concentrate and enters the evaporation and crystallization unit.

[0088] In the evaporation and crystallization unit, the evaporation temperature is designed to be 80℃ and the vacuum degree is -0.06 MPa. After the concentration is reduced to 20% of the original volume and obvious salt crystal precipitation occurs, the crystallization is continued for 30 min. Then, solid-liquid separation is performed to obtain evaporation condensate, crystallized salt and high-salt mother liquor. The evaporation condensate is returned to the three-stage fine washing unit or used for the preparation of chemical fortification agents. The crystallized salt is recovered as salt. The high-salt mother liquor is returned to the salt-rich concentrate. If necessary, it is discharged through the salt discharge bypass.

[0089] 4. Homologous organic matter recovery and reprocessing:

[0090] The ultrafiltration retentate was washed with low-salt water with a conductivity not higher than 0.90 mS / cm until the conductivity of the homologous organic matter concentrate was not higher than 2.0 mS / cm. It was then mechanically dehydrated to a water content of 50%, and then recombined into the third wet soil cake at 10% of the mass of the third wet soil cake base.

[0091] 5. Product Acquisition:

[0092] After the humus soil is washed and drained naturally until the moisture content is 30%, it is mixed evenly to obtain soil products for greening and planting.

[0093] This embodiment achieves segmented control of salt migration, pollutant reduction, and terminal fine washing through primary coarse washing, secondary enhanced washing, and tertiary fine washing; it achieves separation of homologous organic matter, recycled water, and salt-rich concentrate in the washing solution through ultrafiltration-nanofiltration; and it compensates for the humic components carried out during the washing process by re-mixing homologous organic matter, so that the washed humic soil can be directly used as a soil product for greening and planting.

[0094] Example 2

[0095] A method for preparing greening planting soil by selectively intensifying water washing of landfill humus using the Fenton system is different from Example 1 only in that step 2.3 is in the secondary intensified washing unit, while the rest of the method steps are exactly the same as in Example 1.

[0096] 2.3 In the secondary enhanced washing unit:

[0097] The effluent from the tertiary rinsing is added to the secondary enhanced rinsing unit, and the Fenton system is incorporated. Specifically, this involves first adding 0.1 mol / L dilute sulfuric acid to the tertiary rinsing effluent to adjust the pH of the system to 4.0, then adding hydrogen peroxide and ferrous sulfate, so that the mass percentage of hydrogen peroxide in the tertiary rinsing effluent is 0.5%, and the amount of ferrous sulfate added is 0.2% of the mass of the first wet soil biscuit base.

[0098] The first wet soil cake is fed in and washed under the water washing conditions in 2.1 to cause some of the oxidizable organic micro-pollutants in the humus to undergo oxidative degradation, while promoting colloidal depolymerization and soluble salt migration.

[0099] After the water washing is completed, calcium carbonate is added to adjust the pH of the system to 7.5, and the system is allowed to stand for 30 minutes to allow the residual oxidant to decay, and the second wet soil cake and the secondary enhanced wash water are separated.

[0100] The experimental results in Tables 1 and 2 show that the Fenton system can be used as a chemical enhancement treatment system for a secondary enhanced washing unit to improve the reduction efficiency of some organic micropollutants in humus.

[0101] Example 3

[0102] A method for preparing greening planting soil by selectively intensifying water washing of landfill humus soil using a potassium persulfate activation system is different from Example 1 only in that step 2.3 is in the secondary intensified washing unit, while the rest of the method steps are exactly the same as in Example 1.

[0103] 2.3 In the secondary enhanced washing unit:

[0104] The effluent from the tertiary rinsing is added to the secondary enhanced rinsing unit, and a potassium persulfate activation system is added. Specifically, this includes: first, adding potassium persulfate to the effluent from the tertiary rinsing at a dosage of 1.0% of the mass of the first wet soil biscuit base; then adding ferric oxide as an activator at a dosage of 0.5% of the mass of the first wet soil biscuit base; and finally adjusting the pH of the system to 8.5 with sodium carbonate.

[0105] The first wet soil cake is fed in and washed under the water washing conditions in 2.1 to cause some of the oxidizable organic micro-pollutants in the humus to undergo oxidative degradation, while promoting colloidal depolymerization and soluble salt migration.

[0106] After the water washing is completed, calcium carbonate is added to adjust the pH of the system to 7.2, and the system is allowed to stand for 30 minutes to allow the residual oxidant to decay, and the second wet soil cake and the secondary enhanced wash water are separated.

[0107] The experimental results in Tables 1 and 2 indicate that the potassium persulfate activation system can be used as an alternative enhancement system for the secondary enhanced washing unit to treat humus soil containing high levels of recalcitrant organic micropollutants.

[0108] Comparative Example 1

[0109] The difference between this comparative example and Example 1 is that only the landfill humus soil is screened, magnetically separated and impurity removed, and steps 2-5 are not performed. The pretreated humus soil is used directly as soil for greening and planting.

[0110] The experimental results in Tables 1 and 2 show that although mechanical impurities were removed in this comparative example, soluble salts, soluble chlorine, and exchangeable sodium in the humus soil were not effectively removed, which can easily lead to salt damage and germination inhibition in plants.

[0111] Comparative Example 2

[0112] The difference between this comparative example and Example 1 is that a single-stage ordinary water washing is used instead of a segmented selective enhanced water washing. Specifically, the pretreated humus soil and fresh water are ordinaryly washed at a solid-liquid mass ratio of 1:3. The washing temperature is 25°C, the stirring time is 60 min, and the stirring speed is 200 rpm. After washing, sedimentation and pressure filtration are performed, and the resulting wet soil cake is naturally drained until the moisture content is 30%, which is then used as soil for landscaping.

[0113] The experimental results in Tables 1 and 2 show that this comparative example can only remove some of the easily soluble salts. To further improve the desalination effect, the amount of fresh water used needs to be increased, which leads to an increase in wastewater production.

[0114] Comparative Example 3

[0115] The difference between this comparative example and Example 1 is that the wet soil cake is washed only with the effluent from the tertiary fine washing unit in the secondary enhanced washing unit, without the addition of any chemical enhancement treatment system; the rest of the method steps are exactly the same as in Example 1.

[0116] The experimental results in Tables 1 and 2 show that although this comparative sample can reduce some soluble salts, its reduction effect on organic micropollutants such as polycyclic aromatic hydrocarbons, phthalates, and phenols is limited, and it cannot achieve synergistic control of desalination and decontamination.

[0117] Comparative Example 4

[0118] The difference between this comparative example and Example 1 is that polyaluminum chloride is used as a conventional inorganic water treatment flocculant in the solid-liquid separation unit, and the dosage is still 0.2% of the dry basis mass of the coarse washing slurry; the other steps are the same as in Example 1.

[0119] The experimental results in Tables 1 and 2 show that although this comparative example promoted solid-liquid separation, the flocculant residue was not compatible with the soil suitability for greening and planting, and its promoting effect on improving aggregate structure and retaining homologous organic matter was insufficient.

[0120] Comparative Example 5

[0121] The difference between this comparative example and Example 1 is that the salt-rich washing liquid obtained after flocculation and sedimentation of the first-stage coarse washing is directly discharged into the external wastewater treatment system, without performing step 3, the salt-rich washing liquid separation treatment and step 4, the homologous organic matter recovery and remixing treatment. The third wet soil cake obtained from the third-stage fine washing unit is directly used as soil for greening and planting. The other steps are the same as in Example 1.

[0122] The experimental results in Tables 1 and 2 show that although this comparative example can reduce the risk of salinity and some organic micropollutants in humus soil by selectively enhancing water washing in stages, the humic colloids, dissolved organic matter, and fine particulate organic matter carried out during the water washing process are not recovered and reused, resulting in a decrease in the organic matter content of the humus soil after water washing. The direct discharge of the water washing waste liquid not only increases the pressure on subsequent wastewater treatment, but also fails to achieve water resource recycling and closed-loop reuse of homologous organic matter. At the same time, the process of evaporating and crystallizing the salt-rich concentrate and refluxing the high-salt mother liquor was not set up, and salt recovery was not achieved.

[0123] Soil index tests were performed on the products obtained in Examples 1-3 and Comparative Examples 1-5, and the specific results are shown in Tables 1 and 2.

[0124] Table 1. Effects of different treatment methods on desalination, decontamination, and organic matter retention of humus soil.

[0125] Handling method pH EC (mS / cm) Soluble chlorine (mg / L) Exchangeable sodium (mg / kg) SAR Total polycyclic aromatic hydrocarbons (μg / kg) Organic matter (g / kg) Soil infiltration rate (mm / h) GI (%) Fresh water consumption (m³ / t) Original humus soil 7.82 7.2 520 265 8.6 450 26.5 3.2 38 — Example 1 7.42 0.62 105 72 1.8 95 24.8 18.5 92 1.25 Example 2 7.35 0.68 112 78 2 82 23.6 17.8 90 1.3 Example 3 7.48 0.71 118 82 2.1 74 22.9 17.2 88 1.32 Comparative Example 1 7.78 6.85 495 248 8.1 430 25.8 3.6 42 0.1 Comparative Example 2 7.56 2.35 226 146 4.2 382 20.4 8.4 66 3.2 Comparative Example 3 7.50 1.08 168 108 2.9 356 18.6 10.6 76 1.85 Comparative Example 4 7.44 0.64 110 75 1.9 97 21.2 11.2 75 1.25 Comparative Example 5 7.46 0.66 112 76 1.9 102 16.7 15.8 84 1.25 Standard Limit 5.0~8.3 0.15～0.90 ＜180 ＜120 ＜3 — 12～80 ≥5 ＞80 —

[0126] * The standard limits are based on "Green Planting Soil" (CJ / T 340—2016). The total amount of polycyclic aromatic hydrocarbons and the amount of fresh water used are not directly specified in CJ / T 340—2016, but are used as evaluation indicators for the pollutant reduction and water-saving effects of this invention.

[0127] Table 2. Detection results of heavy metal concentration in humus products obtained by different treatment methods.

[0128] Handling method Total Cd (mg / kg) Total Hg (mg / kg) Total Pb (mg / kg) Total Cr (mg / kg) Total As (mg / kg) Total Ni (mg / kg) Total Cu (mg / kg) Total Zn (mg / kg) Original humus soil 0.32 0.18 62.5 78.6 18.8 32.4 36.8 142.5 Example 1 0.21 0.08 38.5 56.4 12.6 24.3 32.7 118.6 Example 2 0.23 0.09 40.2 58.8 13.1 25.1 34.5 124.2 Example 3 0.24 0.09 41.6 60.1 13.4 25.8 35.1 128.5 Comparative Example 1 0.31 0.17 60.8 76.4 18.1 31.6 36.2 140.8 Comparative Example 2 0.28 0.14 52.7 70.3 16.2 29.4 35.5 136.4 Comparative Example 3 0.26 0.12 47.6 65.8 14.8 27.5 34.1 130.2 Comparative Example 4 0.22 0.09 39.4 57.2 12.9 24.8 33.5 121.6 Comparative Example 5 0.23 0.1 40.1 58.3 13 25 33.8 122.8 Standard Limit ≤0.40 ≤0.40 ≤85 ≤100 ≤30 ≤40 ≤40 ≤150

[0129] * The heavy metal concentration standard limit refers to the Class I limit in "Green Planting Soil" (CJ / T 340—2016).

[0130] As shown in Table 2, the contents of total cadmium, total mercury, total lead, total chromium, total arsenic, total nickel, total copper, and total zinc in the greening planting soil products obtained in Examples 1-3 are all lower than the technical requirements for heavy metal content in Class I greening planting soil of "Greening Planting Soil" (CJ / T 340—2016). This indicates that the treatment process of the present invention did not cause an increase in the total amount of heavy metals, and the total amount of heavy metals in the obtained products meets the requirements for safe utilization of greening planting soil. Compared with the original humus soil, the heavy metal concentrations in Examples 1-3 were significantly reduced, which should be related to the processes of water washing migration, flocculation sedimentation, and fine particle separation. At the same time, the soil-friendly composite flocculant and the recombination of homologous organic matter did not cause an increase in heavy metal concentration, indicating that the process method of the present invention improves the organic matter retention rate of the product without increasing the risk of heavy metal concentration.

[0131] As shown in Tables 1 and 2, compared with the original humus soil, Examples 1-3 significantly reduced the electrical conductivity, soluble chlorine, exchangeable sodium, sodium adsorption ratio, and total polycyclic aromatic hydrocarbons (PAHs) of the humus soil, and significantly improved the germination index and soil infiltration rate. Specifically, Example 1 used an alkaline-activated hydrogen peroxide system, which maintained good desalination and decontamination effects while achieving a high organic matter retention rate; Example 2 used a Fenton system, which showed good PAH reduction effects; and Example 3 used a potassium persulfate activation system, which had a strong reduction capacity for organic micropollutants. In contrast, while Comparative Example 4 was close to Example 1 in terms of desalination and PAH reduction, its germination index was only 75%, lower than the requirement of >80% in CJ / T 340—2016. This indicates that although conventional inorganic water treatment flocculants can achieve solid-liquid separation, they are not suitable for the direct application of washed humus soil as planting soil. Although Comparative Example 5 was able to reduce the risk of salt and some organic micropollutants, the organic matter content of the humus after washing was only 16.7 g / kg because it did not undergo ultrafiltration-nanofiltration separation treatment and homologous organic matter re-mixing. This is significantly lower than the product effect of the Example, indicating that homologous organic matter re-mixing plays an important role in maintaining the organic matter base of humus.

[0132] In summary, the pH, conductivity, organic matter, soil infiltration rate, germination index, soluble chlorine, exchangeable sodium, sodium adsorption ratio, and total heavy metal content of the products obtained in Examples 1-3 all meet the relevant requirements of "Green Planting Soil" (CJ / T 340—2016). Moreover, the treatment process did not cause an increase in the total heavy metal content. This indicates that the present invention can achieve the synergistic effects of desalination, decontamination, water recycling, homologous organic matter re-mixing, and salt recovery of landfill humus soil, and can stably transform the treated humus soil into green planting soil products.

[0133] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A method for preparing planting soil for landscaping by selectively and progressively washing humus from landfills, characterized in that, Includes the following steps: (1) Humus pretreatment: Humus from landfills is cleaned, screened and magnetically separated to remove non-soil impurities and obtain pretreated humus. (2) Segmented selective enhanced washing: The pretreated humus is sequentially fed into a primary coarse washing unit, a secondary enhanced washing unit, and a tertiary fine washing unit. The direction of feeding the humus is opposite to the direction of the washing water flow. Specifically, this includes: In the primary coarse washing unit, after the pretreated humus soil is washed with secondary enhanced washing water, the resulting coarse washing slurry is transferred to the solid-liquid separation unit. After adding composite flocculant for flocculation and sedimentation, centrifugation or pressure filtration, the first wet soil cake and salt-rich washing liquid are obtained. In the secondary enhanced washing unit, after washing the first wet soil cake with the tertiary fine washing effluent and chemical enhanced treatment system, the enhanced washing slurry obtained by sedimentation is used to obtain the second wet soil cake and the secondary enhanced washing effluent. In the three-stage washing unit, after washing the second wet soil cake with fresh water or recycled water, the resulting washing slurry is separated to obtain the third wet soil cake and the third-stage washing effluent; (3) Separation, reuse and salt recovery of rich brine washing solution: The rich brine washing solution is subjected to sedimentation, filtration, ultrafiltration, nanofiltration and evaporation crystallization in sequence; In the ultrafiltration step, the obtained ultrafiltration retentate is used as a homologous organic matter concentration component for homologous organic matter recovery and recombination, and the ultrafiltration permeate is subjected to nanofiltration treatment. In the nanofiltration step, the obtained nanofiltration permeate is used as membrane permeate recycled water in the tertiary washing unit, and the nanofiltration concentrate is used as a salt-rich concentrate for evaporation and crystallization. In the evaporation and crystallization step, the obtained crystallized salt is recovered as salt, the evaporation condensate is reused in the three-stage fine washing unit, and the high-salt mother liquor is refluxed to the salt-rich concentrate for repeated evaporation and crystallization. (4) Homologous organic matter recovery and remixing: The homologous organic matter concentrate from step (3) is washed and dehydrated, and then remixed into the third wet soil cake from step (2) in proportion; (5) Product acquisition: Dehydrate and mix the mixed humus obtained in step (4) to obtain soil products for greening and planting.

2. The method as described in claim 1, characterized in that, In step (1), the humus soil derived from the landfill specifically includes one or more of the following: undersize fine particles obtained during the excavation and remediation of municipal solid waste landfills, mineralized waste fine particles, humification screening products, and stabilized landfill fine particles.

3. The method as described in claim 1, characterized in that, In step (2), in each washing unit, the solid-liquid mass ratio of single-stage humus to washing water is 1:(1-5), the single-stage washing time is 10-240 min, the washing temperature is 10-60℃, and the washing stirring speed is 50-500 rpm.

4. The method as described in claim 1, characterized in that, In step (2), in the solid-liquid separation unit, the composite flocculant includes chitosan, humate and calcium-based mineral materials, with a mass ratio of 1:(1-5):(5-20); the dosage of the composite flocculant is 0.05%-1% of the dry basis mass of the coarse washing slurry; the flocculation and settling time is 10-60 min.

5. The method as described in claim 1, characterized in that, In step (2), in the secondary enhanced washing unit, the chemical enhanced treatment system includes one or more of the following: alkaline activated hydrogen peroxide system, Fenton system, and potassium persulfate activation system.

6. The method as described in claim 5, characterized in that, The alkaline-activated hydrogen peroxide system includes hydrogen peroxide and an alkaline substance, wherein the alkaline substance includes one or more of sodium carbonate, sodium bicarbonate, sodium hydroxide, potassium hydroxide, lime, or wood ash extract. The Fenton system comprises hydrogen peroxide and ferrous salt; The potassium persulfate activation system includes potassium persulfate and an activator, wherein the activator is one or more of the following: ferrous salt, iron oxide, alkaline substance, thermal activation conditions, or ultraviolet activation conditions.

7. The method as described in claim 1, characterized in that, In step (3), the ultrafiltration treatment uses an ultrafiltration membrane with a molecular weight cutoff of 1-100 kDa and an operating pressure of 0.1-0.3 MPa; the nanofiltration treatment uses a nanofiltration membrane with a molecular weight cutoff of 150-500 Da and an operating pressure of 0.5-2.0 MPa. In step (4), the washing uses low-salt water with a conductivity of no more than 0.90 mS / cm, the dehydration is carried out to a water content of 40%-70%, and the remixing ratio is: the homologous organic matter concentrate after dehydration is 5%-15% of the mass of the third wet soil biscuit base.

8. The method as described in claim 1, characterized in that, In step (5), the greening soil product obtained has a soluble salt removal rate of over 60%, a polycyclic aromatic hydrocarbon removal rate of over 75%, and an organic matter retention rate of over 86% compared to the humus raw material.

9. The soil product for greening and planting prepared by the method according to any one of claims 1-8.

10. The application of the soil product for greening and planting prepared by the method according to any one of claims 1-8 in landscaping, road greening, slope ecological restoration, mine revegetation, site closure greening, site ecological restoration or seedling cultivation.

Images