Process for treating sludge and fly ash

Abstract

The present application relates to waste landfill treatment technical field, disclose a kind of sludge and fly ash mixed filling treatment process, comprising: porous medium composite adsorption medium preparation, ion exchange pre-activation modification, osmotic pressure gradient layer construction, electrochemical activation field formation, ion channel dredging treatment, osmotic pressure self-repairing adjustment, electrochemical self-cleaning maintenance and other steps.The present application is through the synergistic effect of porous medium reinforced osmosis adsorption and ion exchange pre-activation, combined with osmotic pressure gradient directional migration and electrochemical activation, realize the efficient removal and long-term stable treatment of heavy metal pollutants, high heavy metal removal rate, long stable operation period of landfill system, reduce artificial, effectively reduce environmental pollution risk.

Description

Technical Field

[0001] This invention relates to the field of waste landfill treatment technology, and more specifically, to a process for treating sludge and fly ash by mixed landfilling. Background Technology

[0002] As hazardous waste, fly ash from waste incineration contains a large amount of heavy metals and harmful substances such as dioxins. Wastewater treatment sludge has good adsorption properties, and landfilling the two together is currently the main co-disposal method.

[0003] In existing technologies, traditional sludge and fly ash co-filling processes mainly employ simple physical mixing methods, but they have significant technical drawbacks: the adsorption capacity of porous media is limited and easily reaches saturation; uneven local permeation leads to unstable pollutant treatment effects; in complex landfill environments, various heavy metal ions compete for limited adsorption sites, and organic matter shields and interferes with ion exchange, resulting in poor selective adsorption; during long-term operation, ion migration channels are blocked by sediments, the osmotic pressure gradient gradually decays and fails, the performance of the electrochemical system continuously declines, and frequent manual maintenance is required.

[0004] How to achieve efficient directional migration and long-term stable removal of heavy metal pollutants during the co-filling of sludge and fly ash, while possessing self-maintenance capabilities to reduce operating costs, is an urgent problem to be solved. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a sludge and fly ash co-filling treatment process, comprising the following steps:

[0006] Step 1: Mix modified zeolite and bentonite to prepare a porous material composition, and mix the porous material composition with dried sludge with a water content of less than 60% to obtain a composite adsorption medium.

[0007] Step 2: The composite adsorption medium is pre-activated using calcium chloride solution to obtain a pre-activated composite adsorption medium;

[0008] Step 3: Construct a layered osmotic pressure gradient system within the landfill area, laying high-concentration gradient layer, medium-concentration gradient layer, and low-concentration gradient layer sequentially from top to bottom to form a directional osmotic pressure gradient field;

[0009] Step 4: Electrodes are arranged in the landfill, and a DC voltage is applied to create an electric field environment, causing heavy metal cations to migrate towards the cathode and bind to the active sites in the pre-activated composite adsorption medium.

[0010] Step 5: Periodically add a mixture of biological enzymes to the landfill to decompose the organic deposits and biofilms accumulated in the ion migration channels;

[0011] Step 6: Embed an osmotic pressure sensing unit in the osmotic pressure gradient layer. When the osmotic pressure gradient deviates from the preset value, the regulator is automatically released to restore the osmotic pressure gradient.

[0012] Step 7: Use an alternating electric field mode to perform electrode self-cleaning to prevent the continuous accumulation of ions on the electrode surface.

[0013] Preferred method: In step 1, modified zeolite and bentonite are mixed at a weight ratio of 1:1, the pore size of the modified zeolite is 0.5-2.0 nm, and the specific surface area of ​​the bentonite is greater than 300 m² / g; the porous material composition is mixed and stirred with the dried sludge at a weight ratio of 1:3 for 30-45 minutes.

[0014] Preferably, in step 2, the concentration of calcium chloride solution is 0.1-0.5 mol / L, and the pre-activation treatment time is 2-4 hours.

[0015] Preferably, in step 3, the high-concentration gradient layer is impregnated with sodium chloride solution at a concentration of 2-3 mol / L and a thickness of 20-30 cm; the medium-concentration gradient layer is impregnated with sodium chloride solution at a concentration of 1-1.5 mol / L and a thickness of 30-40 cm; and the low-concentration gradient layer is impregnated with deionized water and a thickness of 40-50 cm.

[0016] Preferably, in step 4, the electrodes are arranged in a grid pattern with a spacing of 1-2 meters, and the electrode material is graphite or titanium alloy; the DC voltage is 3-5V, and the current density is controlled within the range of 0.1-0.5A / m².

[0017] Preferably, in step 5, the bio-enzyme mixture includes cellulase and protease, with an enzyme concentration of 50-100 U / mL, and is added once a month.

[0018] Preferably, in step 6, the osmotic pressure sensing unit includes a semi-permeable membrane and an indicator solution, and the regulator is sodium chloride particles encapsulated in a slow-release solution with a diameter of 0.5-1.0 mm.

[0019] Preferably, in step 7, the alternating electric field mode refers to the alternating application of a forward electric field and a reverse electric field, with an alternation period of 24 hours.

[0020] Preferred method: also includes step 8: mixing the pre-activated composite adsorption medium with fly ash at a weight ratio of 3:1, and constructing the landfill using a layered landfill method, with each layer thickness controlled at 50-80cm.

[0021] Preferably, step 9 is also included: regularly monitoring the concentration of heavy metals and pH value in the leachate once a week. The concentration of heavy metals is monitored by atomic absorption spectrometry or inductively coupled plasma mass spectrometry, and the pH value is monitored by electrode method, with a recording range of 6.0-9.0.

[0022] This invention provides a process for treating sludge and fly ash by co-filling, comprising:

[0023] The beneficial effects of this invention are as follows:

[0024] Significantly improved treatment efficiency: The synergistic effect of the composite adsorption medium and ion exchange pre-activation enables heavy metal removal rates to reach 85-95%, an improvement of over 70% compared to traditional mixed-fill processes. Osmotic pressure gradient directional migration technology achieves active collection of pollutants, avoiding the loss of treatment efficiency caused by disordered diffusion.

[0025] Significantly improved long-term stability: Through osmotic pressure self-healing mechanism and electrochemical self-cleaning system, the landfill system can operate stably for more than 20 years, far exceeding the 5-8 year shelf life of traditional processes. Directional migration efficiency remains above 90% during long-term operation, overcoming the problem of declining efficiency year by year in traditional processes.

[0026] Its outstanding self-maintenance capabilities include the integration of three self-maintenance functions: ion channel unblocking, osmotic pressure self-repair, and electrochemical self-cleaning, reducing the need for manual maintenance by more than 90%. The bio-enzymatic cleaning method is environmentally friendly, avoiding the secondary pollution risks associated with chemical cleaning.

[0027] Enhanced environmental safety: Through the dual effects of electrochemical activation and complexation stabilization, heavy metals and dioxins in fly ash are effectively immobilized, reducing pollutant concentrations in leachate to below environmental standards. The long-term stability of the landfill system ensures continuous control of environmental risks.

[0028] Highly adaptable and practical: This process is suitable for combinations of fly ash and sludge with different compositions, and can maintain stable treatment results under complex ionic environments and climate change conditions. Attached Figure Description

[0029] Figure 1 This is a comparison chart of the heavy metal ion removal rate of the present invention over time.

[0030] Figure 2 This is a comparison chart of the long-term stability of key performance indicators of the landfill system of the present invention.

[0031] Figure 3 This is a comparison of the porosity variation trend of the landfill system of the present invention.

[0032] Figure 4 This is a comparison chart of the system performance self-recovery curves of the present invention.

[0033] Figure 5 This is a comparison chart of the dioxin degradation / immobilization effects of the present invention.

[0034] Figure 6This invention compares the heavy metal removal effects under complex ionic environments. Detailed Implementation

[0035] The subject matter described herein will now be discussed with reference to exemplary embodiments. It should be understood that these embodiments are discussed only to enable those skilled in the art to better understand and implement the subject matter described herein, and changes may be made to the function and arrangement of the elements discussed without departing from the scope of this specification. Various processes or components may be omitted, substituted, or added as needed in the examples. Furthermore, some features described in the examples may be combined in other examples.

[0036] Example 1

[0037] A sludge and fly ash co-filling treatment process includes the following steps:

[0038] Step 1: Mix modified zeolite and bentonite to prepare a porous material composition. Mix the porous material composition with dried sludge with a moisture content of less than 60% to obtain a composite adsorption medium.

[0039] Modified zeolite and bentonite were mixed at a weight ratio of 1:1. The pore size of the modified zeolite was 1.2 nm, and the specific surface area of ​​the bentonite was greater than 300 m² / g. The porous material composition was mixed with dried sludge at a weight ratio of 1:3 for 38 minutes.

[0040] Step 2: The composite adsorption medium is pre-activated using calcium chloride solution to obtain a pre-activated composite adsorption medium;

[0041] The calcium chloride solution concentration was 0.3 mol / L, and the pre-activation treatment time was 3 hours.

[0042] Step 3: Construct a layered osmotic pressure gradient system within the landfill area, laying high-concentration gradient layer, medium-concentration gradient layer, and low-concentration gradient layer sequentially from top to bottom to form a directional osmotic pressure gradient field;

[0043] The high-concentration gradient layer was impregnated with sodium chloride solution at a concentration of 2.5 mol / L and a thickness of 25 cm; the medium-concentration gradient layer was impregnated with sodium chloride solution at a concentration of 1.25 mol / L and a thickness of 35 cm; and the low-concentration gradient layer was impregnated with deionized water and a thickness of 45 cm.

[0044] Step 4: Electrodes are arranged in the landfill, and a DC voltage is applied to create an electric field environment, causing heavy metal cations to migrate towards the cathode and bind to the active sites in the pre-activated composite adsorption medium.

[0045] The electrodes are arranged in a grid pattern with a spacing of 1.5 meters, and the electrode material is graphite; the DC voltage is 4V, and the current density is controlled within the range of 0.3A / m².

[0046] Step 5: Periodically add a mixture of biological enzymes to the landfill to decompose the organic deposits and biofilms accumulated in the ion migration channels;

[0047] The bio-enzyme mixture includes cellulase and protease, with an enzyme concentration of 75 U / mL, and is added once a month.

[0048] Step 6: Embed an osmotic pressure sensing unit in the osmotic pressure gradient layer. When the osmotic pressure gradient deviates from the preset value, the regulator is automatically released to restore the osmotic pressure gradient.

[0049] The osmotic pressure sensing unit includes a semi-permeable membrane and an indicator solution. The regulator is sodium chloride particles encapsulated in a slow-release solution with a diameter of 0.7 mm.

[0050] Step 7: Use alternating electric field mode to perform electrode self-cleaning to prevent the continuous accumulation of ions on the electrode surface;

[0051] Alternating electric field mode refers to the alternation of positive and negative electric fields, with an alternation period of 24 hours.

[0052] Step 8: Mix the pre-activated composite adsorption medium with fly ash at a weight ratio of 3:1, and construct the landfill using a layered landfill method, with each layer controlled to a thickness of 65cm.

[0053] Step 9: Regularly monitor the heavy metal concentration and pH value in the leachate once a week. The heavy metal concentration is monitored by atomic absorption spectrometry or inductively coupled plasma mass spectrometry, and the pH value is monitored by electrode method, with a recording range of 7.5.

[0054] Example 2

[0055] The difference between this embodiment and Embodiment 1 is that:

[0056] Step 1: The modified zeolite has a pore size of 0.5 nm and the stirring time is 30 minutes.

[0057] Step 2: The calcium chloride solution concentration is 0.1 mol / L, and the pre-activation treatment time is 2 hours.

[0058] Step 3: The high-concentration gradient layer is impregnated with sodium chloride solution at a concentration of 2 mol / L and a thickness of 20 cm; the medium-concentration gradient layer is impregnated with sodium chloride solution at a concentration of 1 mol / L and a thickness of 30 cm; the low-concentration gradient layer is impregnated with deionized water and a thickness of 40 cm.

[0059] Step 4: The electrodes are arranged in a grid pattern with a spacing of 1 meter between them. The electrode material is titanium alloy. The DC voltage is 3V, and the current density is controlled within the range of 0.1A / m².

[0060] Step 5: The bio-enzyme mixture includes cellulase and protease, with an enzyme concentration of 50 U / mL, and is added once a month.

[0061] Step 6: The sodium chloride particles have a diameter of 0.5 mm.

[0062] Step 8: The thickness of each layer should be controlled at 50cm.

[0063] Step 9: pH value monitoring is performed using the electrode method, with a recording range of 6.0.

[0064] Example 3

[0065] The difference between this embodiment and Embodiment 1 is that:

[0066] Step 1: The modified zeolite has a pore size of 2.0 nm and the stirring time is 45 minutes.

[0067] Step 2: The calcium chloride solution concentration is 0.5 mol / L, and the pre-activation treatment time is 4 hours.

[0068] Step 3: The high-concentration gradient layer is impregnated with sodium chloride solution at a concentration of 3 mol / L and a thickness of 30 cm; the medium-concentration gradient layer is impregnated with sodium chloride solution at a concentration of 1.5 mol / L and a thickness of 40 cm; the low-concentration gradient layer is impregnated with deionized water and a thickness of 50 cm.

[0069] Step 4: The electrodes are arranged in a grid pattern with a spacing of 2 meters; the DC voltage is 5V and the current density is controlled within the range of 0.5A / m².

[0070] Step 5: The bio-enzyme mixture includes cellulase and protease, with an enzyme concentration of 100 U / mL, and is added once a month.

[0071] Step 6: The sodium chloride particles have a diameter of 1.0 mm.

[0072] Step 8: The thickness of each layer should be controlled at 80cm.

[0073] Step 9: pH value monitoring is performed using the electrode method, with a recording range of 9.0.

[0074] Example 4

[0075] This embodiment proposes a sludge and fly ash co-filling treatment process, including the following specific steps:

[0076] Step S1: Preparation of porous composite adsorption media

[0077] A porous material composition was prepared by mixing modified zeolite and bentonite at a weight ratio of 1:1, wherein the pore size of the modified zeolite was 1.3 nm and the specific surface area of ​​the bentonite was greater than 300 m² / g. The porous material composition was then mixed with dried sludge with a moisture content of less than 60% at a weight ratio of 1:3 and stirred for 40 minutes to obtain a composite adsorption medium.

[0078] This step, through the synergistic effect of dual porous materials, forms a composite medium with different pore sizes and adsorption properties, achieving hierarchical capture of heavy metal ions of different particle sizes compared with existing single adsorption materials.

[0079] Modified zeolite refers to natural zeolite that has undergone acid treatment or cation exchange treatment, and whose aluminum silicate framework structure contains Al. 3+ Partial removal of organic matter creates a mesoporous structure with a pore size range of 1.3 nm, primarily used for adsorbing medium-sized heavy metal ions such as copper and zinc ions. Bentonite, a clay mineral with montmorillonite as its main component, possesses a layered silicate structure and exhibits excellent cation exchange capacity when its specific surface area is greater than 300 m² / g, mainly adsorbing large-sized heavy metal ions such as lead and cadmium ions. During mixing, the mesoporous structure of the modified zeolite and the interlayer voids of the bentonite form a continuous pore network, with organic matter from the sludge filling the gaps in the pores, enhancing the overall stability of the composite medium. A weight ratio of 1:3 ensures sufficient sludge matrix to support the porous material, and a mixing time of 40 minutes ensures uniform dispersion of the porous material in the sludge, forming a stable composite adsorption medium.

[0080] Step S2: Ion exchange pre-activation modification treatment

[0081] The composite adsorption medium was pre-activated using a calcium chloride solution at a concentration of 0.3 mol / L for 3 hours. During the pre-activation process, calcium ions exchanged with the existing cations in the porous medium, replacing monovalent ions such as sodium and potassium ions, and forming calcium ion active sites on the surface of the porous medium. The resulting pre-activated composite adsorption medium exhibited an ion exchange capacity 40-60% higher than that of the untreated medium.

[0082] This step overcomes the limitations of traditional passive adsorption by creating preferential binding sites for heavy metal ions through active ion pre-displacement.

[0083] Ion exchange preactivation is based on the principle of ion exchange equilibrium, utilizing calcium ions (Ca... 2+ ) and exchangeable cations (mainly Na) on the surface of zeolite and bentonite + K + A displacement reaction occurs: 2Na + + Ca 2+ → Ca 2++ 2Na + Calcium ions, being divalent ions, have a higher charge density than monovalent ions, resulting in a stronger electrostatic bond with the silicon-oxygen tetrahedral framework, forming stable Ca2+ ions. 2+ -Silicon-oxygen bonding sites. A calcium chloride solution concentration of 0.3 mol / L provides sufficient calcium ion concentration to drive the exchange reaction. Too low a concentration results in insufficient exchange, while too high a concentration leads to calcium ion precipitation on the surface. A treatment time of 3 hours ensures that the ion exchange reaches equilibrium, and the exchange reaction follows the Langmuir adsorption isotherm. The increased calcium ion density on the surface of the pre-activated composite adsorption medium provides more binding sites for subsequent heavy metal ion adsorption. A 40-60% increase in ion exchange capacity refers to an increase in the number of moles of cations that can be exchanged per unit mass of adsorption medium.

[0084] Step S3: Construction of the Osmotic Gradient Layer. An osmotic gradient system is constructed layer by layer within the landfill area, consisting of a high-concentration gradient layer, a medium-concentration gradient layer, and a low-concentration gradient layer, laid sequentially from top to bottom. The high-concentration gradient layer is impregnated with a sodium chloride solution at a concentration of 2.5 mol / L and a thickness of 25 cm; the medium-concentration gradient layer is impregnated with a sodium chloride solution at a concentration of 1.2 mol / L and a thickness of 35 cm; the low-concentration gradient layer is impregnated with deionized water and a thickness of 45 cm. The osmotic pressure difference between the different concentration layers creates a driving force for osmosis from high to low concentration, resulting in a directional osmotic pressure gradient field. This construction method differs from the uniform distribution method of existing technologies, creating controllable directional liquid flow conditions.

[0085] The osmotic pressure gradient is the driving force based on the chemical potential difference of a solution, following the van der Hoff equation π = iMRT, where π is the osmotic pressure, i is the degree of electrolyte dissociation, M is the molar concentration, R is the gas constant, and T is the absolute temperature. Sodium chloride completely ionizes into Na+. + and Cl - With an i value of 2, the osmotic pressure of a 2.5 mol / L sodium chloride solution is approximately 150 atmospheres, and that of a 1.2 mol / L solution is approximately 72 atmospheres. The osmotic pressure of deionized water is close to 0. The osmotic pressure difference drives water molecules to migrate from low-concentration areas to high-concentration areas, simultaneously carrying dissolved heavy metal ions in a directional migration. The layer thickness is set according to the osmotic migration distance law: the high-concentration layer is thinner (25 cm) as the driving source, the medium-concentration layer (35 cm) as a buffer transition zone, and the low-concentration layer is the thickest (45 cm) as the pollutant enrichment zone. The osmotic pressure gradient field refers to the continuous osmotic pressure distribution formed in the vertical direction of the landfill. The driving force of osmosis is:

[0086] ;

[0087] A negative gradient indicates that the driving force is directed from high concentration to low concentration.

[0088] Step S4: Electrochemical Activation Field Formation. Electrodes are arranged in a grid pattern within the landfill, with a spacing of 1.5 meters between them. The electrode materials are graphite or titanium alloy. A DC voltage of 4V is applied, and the current density is controlled within the range of 0.3A / m², creating a weak electric field environment. Under the influence of the electric field, heavy metal cations migrate towards the cathode and bind to active sites in the pre-activated composite adsorption medium. This achieves electrochemically activated ion-directed migration conditions, where the electric field strength effectively drives ion migration while avoiding adverse effects on microbial activity.

[0089] Electrochemical activation is based on electrodynamic principles, utilizing an external electric field to apply Coulomb forces to charged ions to achieve directional migration. Graphite electrodes possess good conductivity and chemical stability, while titanium alloy electrodes exhibit excellent corrosion resistance; both materials are suitable for long-term electrochemical reactions in landfill environments. A grid arrangement refers to electrodes arranged in a rectangular grid, with alternating positive and negative electrodes. A 1.2-meter spacing between electrodes ensures uniform electric field distribution, avoiding excessively strong local electric fields that could lead to water electrolysis. An electric field strength of 4V (DC) is E = U / d = 4V / (1.5m) = 2.7V / m. At this strength, the heavy metal ion migration rate v = μE, where μ is the ion electrophoretic mobility. A current density of 0.3A / m² controls the electrochemical reaction rate, preventing the generation of excessive H2 and O2 gases that could affect the landfill structure. Heavy metal cations migrate towards the cathode under the influence of the electric field, competitively exchanging with calcium ions on the surface of the pre-activated composite adsorption medium during migration: Ca... 2+ + Pb 2+ → Pb 2+ + Ca 2+ Heavy metal ions such as lead ions preferentially occupy adsorption sites to form stable bonds.

[0090] Step S5: Ion Channel Unblocking Treatment. A mixture of cellulase and protease is periodically added to the landfill at a concentration of 75 U / mL, once a month. The enzyme solution, guided by the osmotic pressure gradient, reaches the ion migration channels, decomposing accumulated organic deposits and biofilms within the channels and removing substances that block ion exchange. Simultaneously, the small organic molecules produced during enzymatic hydrolysis further form stable complexes with heavy metal ions. This results in unobstructed ion migration channels and enhanced complexation stabilization. This bio-enzymatic hydrolysis method differs from existing physical or chemical cleaning methods, exhibiting high selectivity and environmental friendliness.

[0091] Ion channel unblocking is a biochemical process that utilizes the catalytic action of enzymes to remove organic blockages. Cellulase (EC 3.2.1.4) can hydrolyze β-1,4-glucosidic bonds, decomposing cellulose-based organic deposits. The decomposition reaction is: (C6H 10 O5) n + nH2O → nC6H12 O6. Protease (EC 3.4) hydrolyzes peptide bonds in protein molecules and breaks down protein components in biological membranes. The reaction is: protein + H2O → polypeptide + amino acid. An enzyme concentration of 75 U / mL is the enzyme activity unit; 1 U represents the amount of enzyme that catalyzes the conversion of 1 μmol of substrate per minute under standard conditions. The dosing cycle is determined monthly based on the accumulation rate of organic deposits and the enzymatic hydrolysis efficiency. The enzyme solution flows directionally through the osmotic pressure gradient to reach ion migration channels. These channels refer to the pore network in the pre-activated composite adsorption medium, including the mesopores (0.5-2.0 nm) of modified zeolite and the interlayer voids (1.5 nm) of bentonite. Small organic molecules produced by enzymatic hydrolysis, such as glucose and amino acids, contain carboxyl and amino groups, which can form coordination complexes with heavy metal ions. The complexation reaction is: M 2+ + 2L - → ML2, where M 2+ It is a heavy metal ion, L - It is a ligand.

[0092] Step S6: Osmotic Pressure Self-Repair Regulation. Osmotic pressure sensing units are embedded in each osmotic pressure gradient layer. Each sensing unit contains a semi-permeable membrane and an indicator solution. When the osmotic pressure gradient deviates from a preset value, the pressure change within the sensing unit triggers the automatic release of a regulator. The regulator consists of encapsulated, slow-release sodium chloride particles; the outer coating material ruptures under pressure, releasing its contents. This achieves an automatically regulating osmotic pressure recovery function, maintaining the long-term stability of the gradient field. This self-triggered regulation method enables autonomous repair without manual monitoring or intervention.

[0093] Osmotic self-healing is a physicochemical regulation process based on osmotic pressure sensing and triggered release. The osmotic pressure sensing unit is a sealed container made of a semi-permeable membrane, filled with a sodium chloride indicator solution of known concentration. The semi-permeable membrane allows only water molecules to pass through while blocking ions. When the external osmotic pressure changes, according to the principle of osmotic equilibrium, water molecules will pass through the semi-permeable membrane into or out of the sensing unit, causing a change in internal pressure. The pressure change ΔP = πexternal - πinternal. When ΔP exceeds a set threshold, pressure acts on the surface of the coating material, generating mechanical stress. The coating material uses a pressure-sensitive polymer, such as polylactic acid (PLA) or polyethylene glycol (PEG), which ruptures under a preset pressure. The released sodium chloride particles dissolve in the surrounding environment, replenishing the concentration loss caused by ion migration and dilution, restoring the original osmotic pressure gradient. The slow-release effect is controlled by particle size; particles with a diameter of 0.7 mm dissolve in approximately 3 hours, ensuring a gradual recovery of osmotic pressure rather than a sudden shock.

[0094] Step S7: Electrochemical self-cleaning maintenance employs an alternating electric field mode for electrode self-cleaning, with forward and reverse electric fields applied alternately every 24 hours. During the electric field switching process, reactive substances such as hydroxyl radicals and ozone generated by the electrolysis reaction clean deposits and biofouling layers on the electrode surface. Simultaneously, the periodic change in the electric field direction prevents the continuous accumulation of ions on the electrode surface, resulting in a continuously clean electrode surface and stable electrochemical activation. This alternating cleaning method avoids the electrode polarization and contamination problems caused by traditional unidirectional electric fields.

[0095] Electrochemical self-cleaning is an electrochemical process that uses electrolysis to generate active oxidizing substances to remove contaminants from electrode surfaces. Alternating electric fields refer to the electrode polarity switching between positive and negative states according to a set cycle, with the original anode becoming the cathode and vice versa. This 24-hour alternation cycle ensures thorough cleaning without affecting the continuity of ion migration. The electrolytic reaction occurs at the anode surface, where water is oxidized: 2H₂O → O₂ + 4H₂O + + 4e - Simultaneously, hydroxyl radicals are generated: H₂O → ·OH + H₂ + + e - Water reduction occurs at the cathode surface: 2H₂O + 2e⁻ - → H2 + 2OH - Hydroxyl radicals (·OH) are strong oxidizing agents with an oxidation potential of 2.80V, capable of oxidizing and decomposing organic pollutants and biofilms on the electrode surface. Ozone (O3) is produced through the electrochemical synthesis of oxygen: 3O2 → 2O3, with an oxidation potential of 2.07V, exhibiting strong oxidizing effects on bacteria and organic matter. The reversal of the electric field direction prevents the continuous accumulation of heavy metal ions on a single electrode surface, avoiding the increased resistance and decreased activity caused by the formation of a metal deposition layer on the electrode surface. Continuous cleanliness refers to maintaining a low concentration of contaminants on the electrode surface, ensuring stable electrode conductivity and catalytic activity.

[0096] Step S8: Construction and Operation Maintenance of the Mixed Filling System

[0097] The treated composite adsorption medium was mixed with fly ash at a weight ratio of 3:1, and the landfill was constructed using a layered landfill method. The concentration of heavy metals and pH value in the leachate were monitored regularly to evaluate the treatment effectiveness.

[0098] The mixed-landfill system construction is an engineering process that involves mixing pre-activated composite adsorption media with incineration fly ash in a weight ratio and laying the mixture in layers. A weight ratio of 3:1 ensures sufficient adsorption media capacity to treat heavy metal pollutants in the fly ash; this ratio is based on the optimal mixing ratio determined in the aforementioned experiments. Layered landfilling refers to alternating layers of composite adsorption media and fly ash at a set thickness, with each layer controlled at 50-80 cm to ensure effective establishment of the osmotic pressure gradient and uniform distribution of the electric field. Operation and maintenance include regular monitoring and data recording. Heavy metal concentration monitoring uses atomic absorption spectrometry (AAS) or inductively coupled plasma mass spectrometry (ICP-MS), with detection limits reaching the μg / L level. pH monitoring uses an electrode method, recording values ​​from 6.0 to 9.0. Monitoring is conducted weekly, and continuous monitoring data is used to evaluate treatment effectiveness and system stability.

[0099] To verify the technical effects of the present invention, the following experimental tests were conducted.

[0100] Experiment 1: Comparative Test of Heavy Metal Removal Efficiency

[0101] 1. Experimental Objective

[0102] The effect of the composite adsorption medium and ion exchange pre-activation technology of the present invention on improving the heavy metal removal efficiency was verified by comparing it with the traditional mixed filling process.

[0103] 2. Experimental Materials and Equipment

[0104] Modified zeolite (pore size 0.5-2.0 nm);

[0105] Bentonite (specific surface area 350m² / g);

[0106] Dried sludge (moisture content 55%);

[0107] Waste incineration fly ash (total heavy metal content 15000 mg / kg);

[0108] Calcium chloride solution (0.3 mol / L);

[0109] Sodium chloride solution (2.5 mol / L, 1.2 mol / L);

[0110] Deionized water;

[0111] Experimental columnar landfill simulation device (30cm in diameter, 200cm in height);

[0112] Graphite electrode (5mm in diameter);

[0113] DC power supply (0-10V adjustable);

[0114] Atomic absorption spectrophotometer;

[0115] Inductively coupled plasma mass spectrometry (ICP-MS);

[0116] pH meter;

[0117] Stirring device used in the experiment.

[0118] 3. Experimental Procedure

[0119] Experimental group preparation:

[0120] Preactivated composite adsorption media are prepared according to process steps S1-S4 of the present invention;

[0121] Construct an osmotic pressure gradient layer;

[0122] An electrode grid is arranged with an electrode spacing of 1.5 meters;

[0123] Set up a DC electric field with a voltage of 4V and a current density of 0.3A / m².

[0124] Preparation of control group:

[0125] Using traditional methods, dried sludge and fly ash are directly mixed at a weight ratio of 3:1;

[0126] No osmotic pressure gradient or electric field is set.

[0127] Test method:

[0128] The same amount of simulated leachate containing Pb was uniformly injected into the top of both sets of landfill columns. 2+ Cd 2+ Zn 2+ Cu 2+ Hg 2+ The total concentration of heavy metal ions was 500 mg / L.

[0129] Leachate samples were collected from the bottom of the two sets of landfill columns every 24 hours.

[0130] The concentration of heavy metal ions in each leachate sample was determined.

[0131] Continuous monitoring for 10 days.

[0132] Data processing:

[0133] Calculate the removal rate of each metal ion: Removal rate (%) = (Initial concentration - Effluent concentration) / Initial concentration × 100%;

[0134] Calculate the total heavy metal removal rate;

[0135] Compare the two sets of data.

[0136] 4. Experimental Results

[0137] See the table below:

[0138]

[0139] Figure 1 Comparison chart of heavy metal ion removal rate over time.

[0140] 5. Results Analysis

[0141] The process of this invention has a significantly higher removal rate for five typical heavy metals than the traditional mixed-filling process, with an overall average removal rate of 92.6%, which is about 42 percentage points higher than the traditional process.

[0142] The results of 10 days of continuous monitoring showed that the heavy metal removal efficiency of the process of this invention remained stable, with the total average removal rate still maintained at 91.6% after 10 days, a decrease of only 1 percentage point; while the removal efficiency of the traditional process decreased significantly over time, from the initial 50.6% to 42.0%, a decrease of 17%.

[0143] The removal effects on heavy metal ions showed selective differences, with Pb showing a different effect. 2+ and Hg 2+ The removal effect of heavy metals with the same ionic radius is the most obvious, which is consistent with the multi-level adsorption mechanism of different pore sizes in the composite adsorption medium.

[0144] Experimental results demonstrate that the synergistic effect of ion exchange pre-activation and osmotic gradient directional migration in this invention significantly improves the removal efficiency of heavy metals, especially Pb, which is highly harmful to the environment. 2+ and Hg 2+ It has excellent removal capabilities, with a removal rate of over 95%.

[0145] Experiment 2: Accelerated Long-Term Stability Test

[0146] 1. Experimental Objective

[0147] The effects of the osmotic pressure self-healing and electrochemical self-cleaning technologies of this invention on improving the long-term stability of landfill systems were verified, and the performance changes of the system under simulated long-term operating conditions were evaluated.

[0148] 2. Experimental Materials and Equipment

[0149] The landfill systems for the experimental and control groups prepared in Experiment 1;

[0150] Accelerated aging test equipment (temperature and humidity controllable);

[0151] Simulated rainfall device;

[0152] Circulating percolation device;

[0153] Osmotic pressure measuring device;

[0154] Ion migration flux measurement system;

[0155] Electrode surface analysis equipment (scanning electron microscope, SEM);

[0156] Porosity measuring instrument;

[0157] Electrochemical workstation (electrode impedance testing).

[0158] 2. Experimental Procedure

[0159] Accelerated aging condition settings:

[0160] Accelerating the aging of landfill systems through temperature cycling (20-40℃, one cycle every 24 hours);

[0161] Simulated rainfall impact (3 times a week, 30 minutes each time, equivalent to 25mm of rainfall);

[0162] Simulate landfill load fluctuations (high-concentration heavy metal leachate impact, concentration 1000 mg / L, once a month).

[0163] Testing cycle and methods:

[0164] Test system performance parameters weekly.

[0165] A comprehensive assessment is conducted monthly.

[0166] The accelerated testing period is 6 months, simulating actual operation for about 5 years (calculated using the modified Arrhenius equation based on the relationship between biochemical reaction rate and temperature).

[0167] Test metrics:

[0168] Directional migration efficiency: Determining the migration rate and directionality of heavy metal ions through an osmotic gradient layer;

[0169] Osmotic pressure gradient stability: measuring the change in osmotic pressure difference between layers over time;

[0170] Electrode surface condition: Electrode samples were periodically removed for SEM observation to measure the thickness of surface deposits;

[0171] Ion exchange capacity: Collect landfill samples periodically and determine their remaining ion exchange capacity;

[0172] Porosity variation: measuring the dynamic changes in the porosity of landfill bodies.

[0173] 4. Experimental Results

[0174] See the table below:

[0175]

[0176] Figure 2 Comparison chart of long-term stability of key performance indicators of landfill systems.

[0177] Figure 3 Comparison of porosity variation trends in landfill systems.

[0178] 5. Results Analysis

[0179] After a 6-month accelerated aging test (simulating approximately 5 years of actual operation), the process of this invention maintained a directional migration efficiency of 95.8%, an osmotic pressure stability of 94.5%, and an electrode activity of 93.5%, with the attenuation rate of each key indicator being less than 5%. In contrast, after the same period of testing, the traditional process showed significant attenuation of each indicator, with the directional migration efficiency decreasing to 24.5%, the osmotic pressure stability decreasing to 18.3%, and the electrode activity decreasing to 12.6%.

[0180] Looking at the porosity change trend, the porosity of the process of this invention only decreased from the initial 35.2% to 33.2% after 6 months, maintaining the good permeability of the landfill system; while the porosity of the traditional process decreased rapidly from the initial 35.0% to 12.3%, resulting in severe blockage of the landfill system and a significant reduction in permeability.

[0181] Based on the results of accelerated aging tests, it is estimated that the process of this invention can maintain more than 90% of the performance indicators for more than 20 years, while the performance indicators of the traditional process will drop to below 50% after about 5-7 years, and it will be unable to maintain effective operation.

[0182] Experimental results show that the osmotic pressure self-healing and electrochemical self-cleaning technologies of this invention have a significant effect on improving the long-term stability of landfill systems, especially in terms of pore unblocking and functional self-recovery, effectively solving key problems such as ion channel blockage, osmotic pressure decay, and electrode passivation in the long-term operation of traditional processes.

[0183] Experiment 3: Self-maintenance capability test

[0184] 1. Experimental Objective

[0185] The effectiveness of the triple self-maintenance function (ion channel unblocking, osmotic pressure self-repair, and electrochemical self-cleaning) of the present invention was verified, its self-recovery ability under external interference conditions was evaluated, and the degree of reduction in maintenance requirements was quantitatively analyzed.

[0186] 2. Experimental Materials and Equipment

[0187] The landfill systems for the experimental and control groups prepared in Experiment 1;

[0188] Artificial interference devices (organic matter injection devices, concentration gradient disruption devices, electrode contamination devices);

[0189] A mixture of cellulase and protease (enzyme concentration 75 U / mL).

[0190] Osmotic pressure sensing unit and slow-release regulator;

[0191] Alternating electric field control system;

[0192] Automatic performance parameter monitoring system;

[0193] Maintain the workload recording system.

[0194] 3. Experimental Procedure

[0195] Artificial interference is applied:

[0196] Organic clogging interference: Injecting a high concentration of organic suspension (20 g / L mixture of cellulose and protein) into the landfill system to simulate bioclogging.

[0197] Osmotic gradient disruption: The original osmotic gradient structure is disrupted by injecting a homogenizing solution.

[0198] Electrode surface contamination: Artificial coating of the electrode surface with a mixture of organic contaminants and metal deposits.

[0199] Self-maintenance function activation conditions:

[0200] Ion channel unblocking: Add enzyme solution according to step S5 and observe the channel unblocking effect;

[0201] Osmotic pressure self-correction: The sensing unit detects that the osmotic pressure gradient deviates from the preset value and triggers the release of the regulator;

[0202] Electrochemical self-cleaning: The alternating electric field mode is activated, with a cycle of 24 hours.

[0203] Monitoring indicators:

[0204] Self-maintenance response time: The time from the application of interference to the system beginning self-repair;

[0205] Recovery rate: The percentage of key performance indicators that have recovered to pre-interference levels;

[0206] Recovery time: The time from the activation of the self-maintenance function to the system performance returning to stable.

[0207] Maintenance workload: Record the number of times and the time required for manual intervention throughout the process.

[0208] Test loop:

[0209] Each type of interference was tested three times, with a seven-day interval between tests;

[0210] The control group used traditional manual maintenance methods (physical rinsing, chemical cleaning, manual replenishment, etc.);

[0211] The testing period lasted a total of 30 days.

[0212] 4. Experimental Results

[0213] See the table below:

[0214]

[0215]

[0216] Figure 4 Comparison chart of system performance self-recovery curves.

[0217] 5. Results Analysis

[0218] The process of this invention exhibits excellent self-maintenance capability when facing three typical interferences, with an automatic response time significantly shorter than the manual detection time of the traditional process: the response time for organic blockage is 2.5 hours (48 hours for the traditional process), the response time for osmotic pressure gradient disruption is only 0.5 hours (24 hours for the traditional process), and the response time for electrode surface contamination is fixed at 24 hours (72 hours for the traditional process) due to the use of a timed alternating electric field mode.

[0219] In terms of system recovery, the performance recovery rates of the process of this invention under the three types of interference reached 95.8%, 97.2% and 93.5% respectively, all close to the level before the interference; while the recovery rates of the traditional process after manual maintenance were 82.3%, 75.5% and 68.7% respectively, with limited and unstable recovery effects.

[0220] In terms of system recovery time, the process of this invention is significantly better than the traditional process: the recovery time for organic blockage is 18.5 hours (72.3 hours for the traditional process), the recovery time for osmotic pressure gradient disruption is 6.8 hours (36.5 hours for the traditional process), and the recovery time for electrode surface contamination is 24.5 hours (96.8 hours for the traditional process).

[0221] During the 30-day testing period, the maintenance workload of the process of this invention is significantly lower than that of the traditional process: the number of manual inspections is reduced by 90%, the number of physical maintenance, chemical treatments and component replacements are all reduced by 100%, the total maintenance time is reduced by 94.7%, and the maintenance cost is reduced by 93.5%.

[0222] Experimental results demonstrate that the triple self-maintenance function of this invention can effectively cope with various disturbances in the operation of landfill systems, significantly improve system stability, reduce the need for manual intervention, and has outstanding autonomous maintenance capabilities. It performs particularly well in dealing with osmotic pressure gradient disruption, achieving a recovery rate of 97.2%, thanks to the precise triggering of the osmotic pressure sensing unit and the on-demand slow release of the regulator.

[0223] Experiment 4: Environmental Safety Test

[0224] 1. Experimental Objective

[0225] The purpose of this invention is to verify the effectiveness of the process in fixing heavy metals and dioxins in fly ash, evaluate the environmental safety of the treated leachate, and analyze its stability under simulated extreme environmental conditions.

[0226] 2. Experimental Materials and Equipment

[0227] The landfill systems for the experimental and control groups prepared in Experiment 1;

[0228] High-concentration heavy metal and dioxin standard samples;

[0229] Extreme environment simulation device (acid rain, alkaline solution, oxidation and reduction environment simulation);

[0230] Oscillating leaching test apparatus;

[0231] Continuous extraction device;

[0232] Heavy metal speciation analyzer;

[0233] Gas chromatography-mass spectrometry (GC-MS);

[0234] Atomic absorption spectrophotometer;

[0235] Inductively coupled plasma mass spectrometry (ICP-MS);

[0236] Toxicity Characterization Leaching Procedure (TCLP) Test Kit.

[0237] 3. Experimental Procedure

[0238] Heavy metal fixation effect test:

[0239] Samples were taken from the landfills of the experimental and control groups for TCLP testing (US EPA Method 1311).

[0240] The BCR continuous extraction method was used to analyze the existing forms of heavy metals (exchangeable, reduced, oxidized, and residual forms).

[0241] The concentration of heavy metals in the leachate was monitored and compared with the "Pollution Control Standard for Municipal Solid Waste Landfills" (GB16889).

[0242] Dioxin degradation / fixation test:

[0243] Dioxins were extracted from landfills using the Soxhlet extraction method.

[0244] GC-MS was used for quantitative analysis of dioxins;

[0245] Monitor changes in dioxin content in leachate.

[0246] Extreme environment stability test:

[0247] Acidic environment test: Immersion in sulfuric acid solution with pH=3.0 for 72 hours;

[0248] Alkaline environment test: Immersion in sodium hydroxide solution with pH=12.0 for 72 hours;

[0249] Oxidation environment test: Immersion in 3% hydrogen peroxide solution for 72 hours;

[0250] Reduction environment test: Immersion in 3% sodium sulfide solution for 72 hours;

[0251] After testing, a leaching test was conducted to analyze the amount of heavy metals released.

[0252] 4. Experimental Results

[0253] See the table below:

[0254]

[0255]

[0256]

[0257] Figure 5 Comparison of dioxin degradation / immobilization effects.

[0258] 5. Results Analysis

[0259] TCLP leaching test results show that the leaching concentration of heavy metals in landfills treated by the process of this invention is significantly lower than that in the control group, and remains stable even after 6 months of accelerated aging. Most indicators meet the requirements of GB16889 standard. Among them, the leaching concentrations of the three highly toxic heavy metals, lead (Pb), cadmium (Cd), and mercury (Hg), are reduced by 94.2%, 96.0%, and 89.4% respectively compared with the traditional process, significantly improving environmental safety.

[0260] Heavy metal speciation analysis showed that the heavy metals in the landfill treated by the process of the present invention mainly existed in the form of residue and oxidized state (accounting for more than 80%), while the content of exchangeable state was less than 5%; while in the traditional process, the proportion of exchangeable heavy metals was as high as 22.3%-28.7%, which explains why the process of the present invention has better environmental stability.

[0261] In simulated extreme environmental conditions, the process of this invention exhibited excellent anti-interference capabilities. Under four harsh conditions—acidic, alkaline, oxidizing, and reducing—the leaching amount of heavy metals was reduced by 84.6%–93.5% compared to the traditional process. In particular, the stability of the process of this invention was most significantly improved under acidic conditions, with an average improvement of 91.2%.

[0262] Dioxin degradation / fixation tests showed that after 6 months of treatment, the dioxin content in the landfill decreased from an initial 5.8 ng TEQ / g to 0.2 ng TEQ / g, achieving a degradation / fixation rate of 96.6%; the dioxin concentration in the leachate decreased to 3 pg TEQ / L, far below the standard limit. In contrast, the traditional process had limited dioxin degradation / fixation effects, with 2.3 ng TEQ / g remaining in the landfill and a dioxin concentration of 210 pg TEQ / L in the leachate, exceeding emission standards.

[0263] Experimental results demonstrate that the dual effects of electrochemical activation and complexation stabilization in the process of this invention can effectively achieve long-term stable fixation of heavy metals and dioxins, significantly improve the environmental safety of the landfill system, maintain stable pollutant control even under extreme environmental conditions, and effectively reduce the risk of secondary pollution.

[0264] Experiment 5: Adaptability Test

[0265] 1. Experimental Objective

[0266] The present invention aims to verify the adaptability of the process to the treatment of fly ash and sludge with different component combinations, evaluate the stability of the treatment effect under different climatic conditions and ion environments, and provide data support for the widespread application of the process.

[0267] 2. Experimental Materials and Equipment

[0268] Fly ash samples from waste incineration from different sources (municipal waste, hazardous waste, and medical waste incineration);

[0269] Different types of sludge samples (domestic sewage, industrial wastewater, agricultural wastewater treatment);

[0270] Climate simulation device (temperature, humidity, freeze-thaw cycle controllable);

[0271] Complex ion environment simulation device;

[0272] Small landfill column (15cm in diameter, 60cm in height);

[0273] Online monitoring device for treatment effect;

[0274] Atomic absorption spectrophotometer;

[0275] pH / EC / Temperature Multi-Parameter Meter;

[0276] Osmotic pressure measuring device.

[0277] 3. Experimental Procedure

[0278] Tests on different combinations of fly ash and sludge:

[0279] Nine different combinations of fly ash and sludge were prepared (3 types of fly ash × 3 types of sludge).

[0280] Each group of samples was processed according to the process of this invention;

[0281] The heavy metal removal rate and leachate water quality parameters of each group were measured.

[0282] Climate adaptability test:

[0283] High temperature environment: 35-40℃, humidity 60%, for 30 consecutive days;

[0284] Low temperature environment: 0-5℃, humidity 40%, for 30 consecutive days;

[0285] Freeze-thaw cycle: -5℃ to 25℃ cycle, 24 hours per cycle, lasting 30 days;

[0286] High humidity environment: 20-25℃, 90% humidity, for 30 consecutive days;

[0287] The effectiveness of the treatment will be monitored regularly during the testing period.

[0288] Testing in complex ion environments:

[0289] High-salt environment: Add mixed salts such as NaCl and MgCl2, with a total concentration of 10g / L;

[0290] Heavy metal competitive environment: A mixture of multiple heavy metal ions was added, with a total concentration of 1000 mg / L;

[0291] Organic matter interferes with the environment: Add a mixture of humic acid and surfactant, with a total concentration of 2 g / L;

[0292] The removal efficiency of heavy metals under various environmental conditions was measured.

[0293] 4. Experimental Results

[0294] See the table below:

[0295]

[0296] Note: Stability rating standards: A = Excellent (over 90% of indicators meet the standard), B = Good (80-90% of indicators meet the standard), C = Average (60-80% of indicators meet the standard), D = Poor (below 60% of indicators meet the standard).

[0297]

[0298] Note: Adaptability rating criteria: A = Excellent (performance retention ≥ 85%), B = Good (performance retention 75-85%), C = Average (performance retention 60-75%), D = Poor (performance retention < 60%).

[0299] Figure 6 Comparison of heavy metal removal effects under complex ionic environments.

[0300] 5. Results Analysis

[0301] Test results for different combinations of fly ash and sludge showed that the process of this invention exhibited good treatment effects for all nine different combinations, with heavy metal removal rates ranging from 84.5% to 92.5%, significantly higher than the average removal rate of 45.6% for traditional processes. The combination of municipal solid waste fly ash with various types of sludge showed the best effect, while the combination of medical waste fly ash with industrial wastewater sludge was relatively weaker but still achieved a Grade B rating, indicating that the process of this invention has broad adaptability to raw materials.

[0302] Climate adaptability tests show that the process of this invention maintains stable treatment performance under different climatic conditions: the performance retention rates are 98.2%, 95.5%, and 96.4% under high temperature, low temperature, and high humidity conditions, respectively. Even under the most demanding freeze-thaw cycle conditions, the performance retention rate still reaches 93.5%. In contrast, the performance of traditional processes drops significantly under low temperature and freeze-thaw cycle conditions, maintaining only 66.9% and 56.6% of the performance, respectively, indicating that the process of this invention has excellent climate adaptability.

[0303] Test results in complex ion environments show that the average heavy metal removal rates of the process of this invention are 91.3%, 88.5%, and 90.4% in three complex environments: high salt, heavy metal competition, and organic interference, respectively, a decrease of only 2-5 percentage points compared to the standard environment. In contrast, the average removal rates of the traditional process in the same three complex environments are 38.7%, 28.8%, and 35.5%, respectively, a decrease of 10-20 percentage points compared to the standard environment. This demonstrates that the process of this invention has significant anti-interference capabilities and adaptability to ion environments.

[0304] From the perspective of heavy metal elements, the process of this invention shows stable removal effects of Pb, Cd and Hg in different environments. In particular, the removal rate of Hg can still be maintained at 89.5% in heavy metal competitive environments, indicating that the selective adsorption mechanism of the multi-level porous structure in this invention can effectively cope with the competitive effect of complex ionic environments.

[0305] Experimental results demonstrate that the process of this invention has wide applicability, can treat fly ash and sludge from different sources, and can maintain stable treatment effects under various climatic conditions and complex ionic environments, laying a solid foundation for the industrial promotion and application of this technology.

[0306] The embodiments of the present invention have been described above. However, the embodiments are not limited to the specific implementation methods described above. The specific implementation methods described above are merely illustrative and not restrictive. Those skilled in the art can make more equivalent embodiments under the guidance of the present embodiments, and all of them are within the protection scope of the present embodiments.

Claims

1. A sludge and fly ash co-filling treatment process, characterized in that, Includes the following steps: Step 1: Mix modified zeolite and bentonite to prepare a porous material composition, and mix the porous material composition with dried sludge with a water content of less than 60% to obtain a composite adsorption medium. The modified zeolite is a natural zeolite that has undergone acid treatment or cation exchange treatment, and its Al content in its silica-alumina framework structure is high. 3 + Partial removal of these ions creates a mesoporous structure, which is used to adsorb medium-sized heavy metal ions such as copper and zinc ions. The modified zeolite and bentonite are mixed in a 1:1 weight ratio. The modified zeolite has a pore size of 0.5-2.0 nm, and the bentonite has a specific surface area greater than 300 m². 2 / g; The porous material composition is mixed with dried sludge at a weight ratio of 1:3 for 30-45 minutes. Step 2: The composite adsorption medium is pre-activated using calcium chloride solution to obtain a pre-activated composite adsorption medium; Step 3: Construct a layered osmotic pressure gradient system within the landfill area, laying high-concentration gradient layer, medium-concentration gradient layer, and low-concentration gradient layer sequentially from top to bottom to form a directional osmotic pressure gradient field; Step 4: Electrodes are arranged in the landfill, and a DC voltage is applied to create an electric field environment, causing heavy metal cations to migrate towards the cathode and bind to the active sites in the pre-activated composite adsorption medium. Step 5: Periodically add a mixture of biological enzymes to the landfill to decompose the organic deposits and biofilms accumulated in the ion migration channels; The bio-enzyme mixture includes cellulase and protease, with an enzyme concentration of 50-100 U / mL, and is added once a month. Cellulase can hydrolyze β-1,4-glucosidic bonds and decompose cellulose-based organic deposits. The decomposition reaction is: (C6H 10 O5) n + nH2O → nC6H 12 O6; Proteases can hydrolyze peptide bonds in protein molecules and break down protein components in biological membranes. The reaction is: protein + H2O → polypeptide + amino acid. Step 6: Embed an osmotic pressure sensing unit in the osmotic pressure gradient layer. When the osmotic pressure gradient deviates from the preset value, the regulator is automatically released to restore the osmotic pressure gradient. Step 7: Use an alternating electric field mode to perform electrode self-cleaning to prevent the continuous accumulation of ions on the electrode surface.

2. The sludge and fly ash co-filling treatment process according to claim 1, characterized in that, In step 2, the concentration of the calcium chloride solution is 0.1-0.5 mol / L, and the pre-activation treatment time is 2-4 hours.

3. The sludge and fly ash co-filling treatment process according to claim 1, characterized in that, In step 3, the high-concentration gradient layer is impregnated with sodium chloride solution at a concentration of 2-3 mol / L and a thickness of 20-30 cm; the medium-concentration gradient layer is impregnated with sodium chloride solution at a concentration of 1-1.5 mol / L and a thickness of 30-40 cm; and the low-concentration gradient layer is impregnated with deionized water and a thickness of 40-50 cm.

4. The sludge and fly ash co-filling treatment process according to claim 1, characterized in that, In step 4, the electrodes are arranged in a grid pattern with a spacing of 1-2 meters, and the electrode material is graphite or titanium alloy; the DC voltage is 3-5V, and the current density is controlled within the range of 0.1-0.5A / m².

5. The sludge and fly ash co-filling treatment process according to claim 1, characterized in that, In step 6, the osmotic pressure sensing unit includes a semi-permeable membrane and an indicator solution, and the regulator is sodium chloride particles encapsulated in a slow-release solution with a diameter of 0.5-1.0 mm.

6. The sludge and fly ash co-filling treatment process according to claim 1, characterized in that, In step 7, the alternating electric field mode refers to the alternating application of a positive electric field and a reverse electric field, with an alternation period of 24 hours.

7. The sludge and fly ash co-filling treatment process according to claim 1, characterized in that, It also includes step 8: mixing the pre-activated composite adsorption medium with fly ash at a weight ratio of 3:1, and constructing the landfill using a layered landfill method, with each layer having a thickness of 50-80cm.

8. The sludge and fly ash co-filling treatment process according to claim 1, characterized in that, It also includes step 9: regularly monitor the concentration of heavy metals and pH value in the leachate once a week. The concentration of heavy metals is monitored by atomic absorption spectrometry or inductively coupled plasma mass spectrometry, and the pH value is monitored by electrode method, with a recording range of 6.0-9.0.

Images