Garbage incineration fly ash geopolymer composite material and preparation method thereof

Abstract

The invention relates to the technical field of solid waste treatment and recycling, and discloses a waste incineration fly ash geopolymer composite material and a preparation method thereof, and the composite material is prepared from waste incineration fly ash, apatite minerals, zero-valent iron powder, persulfate and an alkali activator. The preparation method comprises the following steps: mixing the waste incineration fly ash, apatite minerals, zero-valent iron powder and persulfate to obtain composite powder; performing frequency conversion mechanochemical synergistic activation on the composite powder, wherein the activation process comprises a low-temperature activation stage and a high-energy pulse activation stage; and finally, mixing the activated powder with an alkali activator, pouring, molding and curing. According to the method, the reduction reaction and the oxidation reaction are driven step by step in the same system by regulating and controlling the mechanical energy input time sequence, the compatibility problem of a reducing agent and an oxidizing agent is solved, different types of persistent organic pollutants are synergistically degraded, meanwhile, heavy metal is stabilized, and the treatment effect is good. And the fly ash is recycled to prepare a geopolymer material with mechanical properties.

Description

Technical Field

[0001] This invention relates to the field of solid waste treatment and resource utilization technology, and in particular to a polymer composite material of waste incineration fly ash and its preparation method. Background Technology

[0002] Waste incineration is one of the main technical means for reducing and harmlessly treating modern urban household waste, but the fly ash produced is classified as hazardous waste. Waste incineration fly ash is enriched with heavy metals such as lead and cadmium, and also adsorbs persistent organic pollutants such as dioxins (PCDD / Fs) and polychlorinated aromatic hydrocarbons (PAHs). These pollutants are chemically stable, highly toxic, and bioaccumulate; improper disposal can pose a long-term threat to the ecological environment and human health.

[0003] Currently, the mainstream method for disposing of fly ash from waste incineration is safe landfill after cement-based solidification / stabilization. This method mainly reduces the leaching toxicity of heavy metals through physical encapsulation and the adsorption of cement hydration products, but its chemical degradation effect on polychlorinated organic pollutants such as dioxins is limited.

[0004] Chemical methods have been employed to degrade organic pollutants in fly ash. For example, strong oxidants such as persulfate generate free radicals, which can effectively oxidize and decompose polycyclic aromatic hydrocarbons (PAHs); while reducing agents such as zero-valent iron can achieve the reductive dechlorination degradation of dioxins. However, the degradation of dioxins and PAHs requires opposing redox environments. Directly adding oxidants and reducing agents to the same system will result in preferential reactions and mutual consumption, leading to low degradation efficiency for the target pollutants and making it difficult to simultaneously treat multiple organic pollutants in a single process. Therefore, developing a technology that can simultaneously and efficiently degrade multiple persistent organic pollutants, stabilize heavy metals, and achieve fly ash resource utilization in an integrated process is a pressing technical problem to be solved in this field. Summary of the Invention

[0005] The technical problem addressed by this invention is that existing waste incineration fly ash treatment technologies struggle to simultaneously degrade persistent organic pollutants with different chemical properties, stabilize heavy metals, and achieve product resource recovery in a single process. In particular, the dechlorination degradation of dioxins and the oxidative degradation of polycyclic aromatic hydrocarbons require different chemical environments; reducing agents and oxidizing agents are prone to ineffective reactions in the same system, leading to low treatment efficiency.

[0006] To address the above problems, the present invention provides the following technical solution:

[0007] In a first aspect, the present invention provides a polymer composite material for waste incineration fly ash.

[0008] The composite material is made from the following raw materials in parts by weight: 100 parts of waste incineration fly ash; 3-10 parts of apatite group minerals; 1-5 parts of zero-valent iron powder; 1-5 parts of persulfate; and an alkaline activator made by mixing 30-50 parts of sodium silicate solution and 10-25 parts of sodium hydroxide solution.

[0009] The waste incineration fly ash, apatite group minerals, zero-valent iron powder, and persulfate undergo a variable frequency mechanical-chemical synergistic activation treatment, including a low-temperature activation stage and a high-energy pulse activation stage, before being mixed with the alkaline activator.

[0010] By employing the above-mentioned technical solution, this solution achieves the degradation of organic pollutants, stabilization of heavy metals, and geological polymerization of the material matrix in a single process through a specific combination of raw materials and preparation technology. The technical principle of this solution lies in the time-sharing control of different chemical reactions in the system via a variable frequency mechanochemical program.

[0011] 1. Low-temperature activation stage: The relatively low mechanical energy input is mainly used to break up agglomerates, increase the specific surface area of ​​reactants, and renew the surface of zero-valent iron, exposing its active sites. This energy level is conducive to the reductive dechlorination reaction of dioxin-like chlorinated organic compounds by zero-valent iron, while being insufficient to trigger the large-scale decomposition of persulfate, thus avoiding premature consumption between the reducing agent and the oxidizing agent.

[0012] 2. High-energy pulse activation stage: The instantaneous input of high energy generates localized high temperatures at the particle collision point, effectively triggering the decomposition of persulfate to produce active sulfate free radicals (SO4•-). - This free radical can oxidize and decompose chemically stable polycyclic aromatic hydrocarbons.

[0013] The aforementioned timing control of energy input enables stepwise driving of reduction and oxidation reactions within the same reactor, resolving the compatibility issue between reducing agents and oxidizing agents, and synergistically degrading persistent organic pollutants of different properties.

[0014] Meanwhile, the apatite group minerals in the system release phosphate ions during mechanochemical activation and subsequent hydration. These ions react in situ with heavy metal ions such as lead and cadmium in fly ash to generate a chemically stable apatite-like mineral phase, thus achieving the chemical fixation of heavy metals.

[0015] Furthermore, this mechanochemical process activates the pozzolanic activity of fly ash. The activated powder undergoes a geopolymerization reaction under the action of an alkaline activator, forming a dense, high-strength three-dimensional aluminosilicate network structure. This structure endows the final product with mechanical properties, allowing it to be used as a building material. Its dense physical structure also physically encapsulates chemically fixed heavy metals, reducing the risk of pollutant leaching.

[0016] Preferably, the apatite group mineral is phosphate rock powder or hydroxyapatite. Phosphate rock powder is widely available and inexpensive, while hydroxyapatite has higher reactivity; both can effectively provide phosphate ions required for the stabilization of heavy metals.

[0017] Preferably, when the apatite group mineral is hydroxyapatite, it is prepared by a wet chemical precipitation method, specifically including:

[0018] (1) Under the condition of pH value of 10-11, diammonium hydrogen phosphate solution is added dropwise to calcium nitrate solution to carry out the reaction and obtain a suspension;

[0019] (2) The suspension is aged, filtered, washed and dried to obtain the hydroxyapatite.

[0020] Preferably, the concentration of the sodium hydroxide solution in the alkali activator is 8–14 mol / L, and the modulus of the sodium silicate solution is 2.5–3.0. Within this parameter range, the alkali activator can provide suitable alkalinity and soluble silicon source for the geopolymerization reaction, promoting the formation of a high-strength geopolymer matrix.

[0021] Secondly, the present invention provides a method for preparing a polymer composite material from waste incineration fly ash, employing the following technical solution:

[0022] The preparation method includes the following steps:

[0023] (a) A composite powder is obtained by mixing waste incineration fly ash, apatite group minerals, zero-valent iron powder and persulfate;

[0024] (b) The composite powder is subjected to frequency conversion mechanical and chemical synergistic activation to obtain activated composite powder. The activation process includes a low-temperature activation stage and a subsequent high-energy pulse activation stage.

[0025] (c) The activated composite powder from step (b) is mixed with an alkaline activator to obtain a slurry;

[0026] (d) The slurry is poured into shape and cured.

[0027] By adopting the above technical solution, the preparation method of the present invention achieves comprehensive treatment of fly ash from waste incineration through an integrated process flow. Its core lies in the variable frequency mechanochemical synergistic activation process in step (b), which, through the temporal control of mechanical energy input, allows different types of chemical reactions within the system to occur stepwise under their respective suitable conditions.

[0028] During the low-temperature activation stage, the lower energy input preferentially promotes the reductive dechlorination reaction of zero-valent iron; subsequently, during the high-energy pulse activation stage, the instantaneous high energy input is concentrated on triggering the oxidation reaction of persulfate.

[0029] This step-by-step approach effectively avoids direct reaction and loss of reducing agents and oxidizing agents in a mixed state, allowing them to work synergistically within the same system to degrade different types of organic pollutants. Simultaneously, the entire activation process enhances the reactivity of fly ash, which is beneficial for subsequent geopolymerization reactions.

[0030] Preferably, the synergistic activation in step (b) is carried out in a planetary ball mill, and the ball-to-material mass ratio is (15-25):1. Further, the rotation speed of the low-temperature activation stage is 250-350 rpm, and the duration is 75-150 min; the high-energy pulse activation stage includes running at a rotation speed of 500-700 rpm, then pausing, and repeating the running and pausing process.

[0031] By adopting the above technical solution, the specific process parameters are the concrete way to realize the aforementioned step-by-step driving strategy. In the planetary ball mill, the set ball-to-particle ratio and rotational speed can provide sufficient energy for particle grinding, dispersion, and surface renewal of zero-valent iron in the low-temperature stage, but not enough to trigger persulfate decomposition; while in the high-energy pulse stage, the higher rotational speed can provide the instantaneous energy required to trigger the oxidation reaction. The alternating operation and pause mode is beneficial for controlling the system temperature and avoiding overheating.

[0032] Preferably, in the high-energy pulse activation phase, the pulse is run at 500-700 rpm for 3-5 minutes, paused for 1-2 minutes, and the process is repeated 4-6 times.

[0033] By adopting the above technical solution, the operation-pause cycle of the high-energy pulse stage can be quantified, which can realize the control of the total input energy, which is beneficial to the effective activation of persulfate, while avoiding energy waste and making the entire activation process stable and controllable.

[0034] Preferably, the curing temperature in step (d) is 20–70°C and the curing time is 6–24 hours.

[0035] By adopting the above technical solution and curing under the specified temperature and humidity conditions, the geological polymerization reaction can be fully carried out, thereby forming a dense matrix with mechanical properties and low permeability, which effectively encapsulates heavy metals.

[0036] In summary, the present invention has at least one of the following beneficial technical effects:

[0037] 1. This invention achieves efficient synergistic degradation of different types of organic pollutants in the same system by employing a variable frequency mechanochemical activation process. This method preferentially drives the reduction and dechlorination reaction of zero-valent iron in a low-rate activation phase, followed by triggering the oxidation reaction of persulfate through a high-energy pulse phase. This avoids the ineffective consumption of reducing and oxidizing agents, thus improving the overall removal efficiency for persistent organic pollutants.

[0038] 2. This invention achieves dual stabilization of heavy metals through chemical fixation and physical encapsulation, significantly reducing the environmental leaching risk of pollutants. The apatite group minerals in the system react in situ with heavy metals such as lead and cadmium to form stable mineral phases, achieving chemical fixation. The subsequently formed high-strength, dense polymer matrix physically encapsulates the solidified heavy metal products, further enhancing the long-term reliability of the solidification / stabilization effect.

[0039] 3. This invention transforms waste incineration fly ash into geopolymer composite materials with mechanical properties, realizing the resource utilization of hazardous waste. Mechanochemical activation enhances the pozzolanic activity of the fly ash, enabling it to participate in geopolymerization reactions as a primary raw material. The resulting composite material can be used as a building material. This method replaces traditional landfill disposal, reducing land occupation and environmental pollution, and offering both economic and environmental benefits. Attached Figure Description

[0040] Figure 1 Figure 1 shows a comparison of the degradation effects of organic pollutants; Figure 2 shows a comparison of the degradation effects of dioxins (PCDD / Fs) in different samples; Figure 3 shows a comparison of the degradation effects of polycyclic aromatic hydrocarbons (PAHs) in different samples.

[0041] Figure 2 This is a graph showing the heavy metal leaching toxicity test results of the final product in Example 1;

[0042] Figure 3 A comparison chart of the mechanical property test results of each sample at 28 days of age;

[0043] Figure 4 The figures show the comparison results of heavy metal leaching toxicity tests for each sample; Figure a) shows the comparison of lead (Pb) leaching concentration, Figure b) shows the comparison of cadmium (Cd) leaching concentration, Figure c) shows the comparison of zinc (Zn) leaching concentration, and Figure d) shows the comparison of chromium (Cr) leaching concentration.

[0044] Figure 5 This is a line graph showing the compressive strength of some samples as a function of age. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0046] The main raw materials and reagents used in the following examples and comparative examples have the following sources and specifications. Reagents not specifically mentioned are all commercially available analytical grade or higher grade products.

[0047] The fly ash from waste incineration is raw fly ash collected by bag filters from municipal solid waste incineration power plants without any pretreatment.

[0048] Phosphate rock powder is made by grinding natural apatite minerals. Its main component is fluorapatite (CAS No.: 1306-05-4), with a particle size of less than 75μm.

[0049] Hydroxyapatite (HAP), the preparation method of which is described in Preparation Example 1.

[0050] Zero-valent iron powder (ZVI) is an industrial-grade reduced iron powder with an average particle size of 45 μm.

[0051] Sodium silicate solution is an industrial-grade liquid with a molar ratio (modulus) of 2.5 or 3.0 between silicon dioxide and sodium oxide.

[0052] Preparation Example 1:

[0053] This preparation example provides a method for preparing hydroxyapatite, including the following steps:

[0054] A 0.5 mol / L calcium nitrate (Ca(NO3)2) solution and a 0.3 mol / L diammonium hydrogen phosphate ((NH4)2HPO4) solution were prepared separately. Under vigorous stirring, the diammonium hydrogen phosphate solution was slowly added dropwise to the calcium nitrate solution at a rate of approximately 5 mL / min, while continuously adjusting the pH of the mixed solution with ammonia water to stabilize it between 10 and 11. After the addition was complete, the reaction was continued at room temperature for 2 hours to allow for sufficient aging. Stirring was stopped, and the mixture was allowed to stand for 12 hours before filtering the resulting white suspension. The filter cake was washed multiple times with deionized water until the pH of the filtrate was close to neutral. The washed filter cake was then dried in an oven at 105°C for 12 hours. Finally, the dried lumps were ground and passed through a 200-mesh sieve to obtain the product with the chemical formula Ca2+. 10 Hydroxyapatite powder of (PO4)6(OH)2, sealed and stored for later use.

[0055] Example 1:

[0056] This embodiment provides a method for preparing a polymer composite material from waste incineration fly ash, comprising the following steps:

[0057] (1) By mass, 100 parts of waste incineration fly ash, 3 parts of phosphate rock powder, 1 part of zero-valent iron powder and 1 part of potassium persulfate are added to the planetary ball mill, and the ball-to-material mass ratio is set to 15:1.

[0058] (2) Start the variable frequency mechanochemical program and set the total time to 90 min. The program includes: first, low-temperature activation at 250 rpm for 75 min; then, high-energy pulse activation at 500 rpm for 3 min, pause for 2 min, and repeat this high-energy pulse process a total of 5 times.

[0059] (3) Prepare an alkaline activator by mixing an 8 mol / L sodium hydroxide solution with a sodium silicate solution of modulus 3.0, wherein the sodium silicate solution is 50 parts and the sodium hydroxide solution is 10 parts. After mixing, cool to room temperature.

[0060] (4) Add the composite powder obtained in step (2) to the alkali activator prepared in step (3), stir in a mechanical stirrer for 15 minutes, and then cast into shape.

[0061] (5) After placing the mold with slurry in an environment with a temperature of 20°C and a relative humidity of not less than 95% for 24 hours, demold the mold to obtain the sample.

[0062] Example 2:

[0063] This embodiment provides a method for preparing a polymer composite material from waste incineration fly ash, comprising the following steps:

[0064] (1) By mass, 100 parts of waste incineration fly ash, 6 parts of hydroxyapatite prepared in Preparation Example 1, 3 parts of zero-valent iron powder and 3 parts of sodium persulfate were added to a planetary ball mill, and the ball-to-material mass ratio was set to 20:1.

[0065] (2) Start the variable frequency mechanochemical program and set the total time to 120 min. The program includes: first, low-temperature activation at 300 rpm for 100 min; then, high-energy pulse activation is performed at 600 rpm for 5 min, paused for 2 min, and this high-energy pulse process is repeated 4 times.

[0066] (3) Prepare an alkaline activator by mixing a 12 mol / L sodium hydroxide solution with a sodium silicate solution of modulus 2.5, wherein the sodium silicate solution is 40 parts and the sodium hydroxide solution is 18 parts. After mixing, cool to room temperature.

[0067] (4) Add the composite powder obtained in step (2) to the alkali activator prepared in step (3), stir in a mechanical stirrer for 10 minutes, and then cast into shape.

[0068] (5) After placing the mold with slurry in an environment with a temperature of 60℃ and a relative humidity of not less than 95% for 12 hours, demold the mold to obtain the sample.

[0069] Example 3:

[0070] This embodiment provides a method for preparing a polymer composite material from waste incineration fly ash, comprising the following steps:

[0071] (1) By mass, 100 parts of waste incineration fly ash, 10 parts of phosphate rock powder, 5 parts of zero-valent iron powder and 5 parts of potassium persulfate are added to the planetary ball mill, and the ball-to-material mass ratio is set to 25:1.

[0072] (2) Start the variable frequency mechanochemical program and set the total time to 180 min. The program includes: first, low-temperature activation at 350 rpm for 150 min; then, high-energy pulse activation at 700 rpm for 5 min, pause for 1 min, and repeat this high-energy pulse process a total of 6 times.

[0073] (3) Prepare an alkaline activator by mixing a 14 mol / L sodium hydroxide solution with a sodium silicate solution of modulus 2.5, wherein the sodium silicate solution is 30 parts and the sodium hydroxide solution is 25 parts. After mixing, cool to room temperature.

[0074] (4) Add the composite powder obtained in step (2) to the alkali activator prepared in step (3), stir in a mechanical stirrer for 5 minutes, and then cast into shape.

[0075] (5) After placing the mold with slurry in an environment with a temperature of 70℃ and a relative humidity of not less than 95% for 6 hours, demold the mold to obtain the sample.

[0076] Comparative Example 1:

[0077] Compared with Example 1, the difference is that the waste incineration fly ash, phosphate rock powder, zero-valent iron powder and potassium persulfate are simply dry-mixed in a mixer without the variable frequency mechanical-chemical synergistic activation step, and the rest are the same.

[0078] Comparative Example 2:

[0079] Compared with Example 1, the difference is that step (2) does not use a frequency conversion program, but runs continuously at a constant high speed of 600 rpm for 20 minutes, while the rest are the same.

[0080] Comparative Example 3:

[0081] The difference from Example 1 is that potassium persulfate is not added to the composite functional additive, but everything else is the same.

[0082] Comparative Example 4:

[0083] The difference from Example 1 is that zero-valent iron powder is not added to the composite functional additive, but everything else is the same.

[0084] Comparative Example 5:

[0085] Unlike the technical solution of Example 1, this comparative example uses a traditional water washing method for pretreatment: the fly ash is washed, filtered and dried, and then only the washed fly ash is used as raw material without adding any composite functional additives. The same alkali activator and subsequent steps as in Example 1 are used to prepare the sample.

[0086] Test Example 1:

[0087] The experimental steps are as follows:

[0088] (1) Take about 10g of the original waste incineration fly ash, the composite powder from step (2) of Example 1, and the composite powder from step (2) of Comparative Example 2, and dry them in an oven at 105℃ until constant weight.

[0089] (2) Weigh the dried sample and add to it. 13 C 12 Labeled PCDD / Fs mixed internal standards and deuterated PAHs mixed internal standards were used, and then the samples were placed in a Soxhlet extractor and continuously thermally extracted with toluene as solvent for 24 h.

[0090] (3) The extract was concentrated by rotary evaporation to about 2 mL and purified by passing it through a multilayer composite silica column. The purification column was filled with neutral silica, alkaline silica, neutral silica, acidic silica, neutral silica and anhydrous sodium sulfate in sequence from bottom to top.

[0091] (4) First, rinse the purification column with n-hexane and discard the eluent. Then, elute with a mixed solvent of n-hexane and dichloromethane and collect the target components of PCDD / Fs and PAHs respectively.

[0092] (5) Evaporate each collected eluent component to near dryness using a rotary evaporator, and add... 13 C 12 The labeled injection standard is diluted to volume with n-nonane or toluene for instrumental analysis.

[0093] (6) According to HJ 77.4-2008, the content of PCDD / Fs was analyzed and the total toxicity equivalent (I-TEQ) was calculated using isotope dilution-high resolution gas chromatography / high resolution mass spectrometry (HRGC / HRMS); according to GB / T 36197-2018, the total content of PAHs was analyzed using gas chromatography-mass spectrometry (GC-MS).

[0094] The experimental results are shown in Table 1 and Figure 1 As shown.

[0095] Table 1. Test results of organic pollutant content in each sample:

[0096] Test object PCDD / Fs content (ng I-TEQ / kg) Total PAH content (mg / kg) Original waste incineration fly ash 850.3 155.7 Example 1 Composite Powder 47.9 16.4 Comparative Example 2 Composite Powder 286.5 78.2

[0097] Test results show that the frequency conversion mechanochemical method in Example 1 can effectively degrade persistent organic pollutants in fly ash.

[0098] The original waste incineration fly ash contained high concentrations of PCDD / Fs (850.3 ng I-TEQ / kg) and PAHs (155.7 mg / kg). After the variable frequency mechanical-chemical synergistic treatment employed in Example 1, the contents of PCDD / Fs and PAHs in the powder were significantly reduced to 47.9 ng I-TEQ / kg and 16.4 mg / kg, respectively, with corresponding degradation rates of 94.4% and 89.5%. This result confirms that the combination of the composition and process of the present invention can effectively destroy and remove these two types of organic pollutants with very different chemical properties.

[0099] Comparative Example 2, employing constant high-speed ball milling, also achieved some degradation of pollutants (PCDD / Fs degradation rate of 66.3%, PAHs degradation rate of 49.8%), but its effect was far inferior to that of Example 1. The underlying reason is that under continuous high-energy mechanical force input, the reducing agent zero-valent iron and the oxidizing agent persulfate are simultaneously and indiscriminately activated. These two opposing active substances undergo a direct, non-selective reaction in the system, leading to mutual consumption and thus reducing their respective effective concentrations for degrading the target pollutants (zero-valent iron for PCDD / Fs degradation, and persulfate for PAHs degradation).

[0100] The frequency conversion program of this invention controls energy input through timing, comprising two stages: low-temperature activation and high-energy pulse. The energy input in the low-temperature activation stage is primarily used to renew the zero-valent iron surface and promote its reduction function; this energy level is insufficient to trigger a large-scale decomposition of persulfate. In the subsequent high-energy pulse stage, the instantaneous high energy input generates localized high temperatures, triggering the decomposition of persulfate to produce active species that degrade PAHs. This temporal differentiation of energy input suppresses ineffective reactions between the reducing agent and the oxidizing agent, forming the technical basis for achieving the synergistic degradation of both pollutants.

[0101] Test Example 2:

[0102] The experimental steps are as follows:

[0103] (1) Take the final solidified sample prepared in Example 1, crush it using a jaw crusher, and pass it through a sieve with a pore size of 5 mm.

[0104] (2) Weigh 100g of the treated sample and operate according to HJ 557-2010. Use sulfuric acid / nitric acid as the leaching agent. Adjust the amount of acid during the shaking process so that the pH of the liquid at the end of the leaching is 5.0±0.05 and the liquid-solid ratio is maintained at 10L / kg.

[0105] (3) Place the sample on a horizontal oscillator and oscillate continuously for 8 hours at a speed of 110 r / min at a temperature of (23±2)℃.

[0106] (4) After the shaking is finished, let it stand for 16 hours, and then use a 0.45μm microporous filter membrane to filter the leachate under pressure.

[0107] (5) Take a portion of the filtrate and use inductively coupled plasma mass spectrometry (ICP-MS) to detect the concentrations of lead (Pb), cadmium (Cd), zinc (Zn) and chromium (Cr) in the leachate according to HJ 700-2014.

[0108] The experimental results are shown in Table 2 and Figure 2 As shown.

[0109] Table 2. Heavy metal concentrations in the final product leachate:

[0110] Heavy metals to be tested Example 1: Leachate concentration (mg / L) GB16889-2008 Limits (mg / L) Lead (Pb) 0.038 0.25 Cadmium (Cd) 0.0016 0.015 Zinc (Zn) 0.17 2 Chromium (Cr) 0.065 1.5

[0111] The leaching toxicity test results showed that the solidified product prepared in Example 1 had an effective stabilizing effect on heavy metals. The concentrations of Pb, Cd, Zn, and Cr in the leachate were 0.038 mg / L, 0.0016 mg / L, 0.17 mg / L, and 0.065 mg / L, respectively, all significantly lower than the limits specified in the "Standard for Pollution Control of Municipal Solid Waste Landfills" (GB 16889-2008).

[0112] The low leaching concentration of heavy metals in the product is attributed to a dual mechanism of chemical fixation and physical encapsulation. At the chemical fixation level, the phosphate rock powder in the composite powder releases phosphate ions (PO42-) during mechanical activation and subsequent hydration reactions. 3- This ion reacts with lead ions (Pb) present in fly ash. 2+ ) and chloride ions (Cl -The reaction produces chlorapatite lead ore (Pb5(PO4)3Cl) in situ, which has an extremely stable structure. Other divalent metal ions such as cadmium and zinc can also enter the apatite lattice through isomorphic substitution, thereby being chemically fixed.

[0113] At the physical encapsulation level, fly ash undergoes a geopolymerization reaction under the action of an alkaline activator, forming a dense three-dimensional aluminosilicate network structure. This process encapsulates the chemically fixed heavy metal mineral phases and a small amount of unreacted heavy metal ions within the gel network. This dense matrix structure constitutes a physical barrier preventing the migration of heavy metals into the external environment. It is this synergistic mechanism, primarily chemical fixation supplemented by physical encapsulation, that ensures the long-term stability of heavy metals within the solidified body, effectively controlling their environmental risks.

[0114] Test Example 3:

[0115] The experimental steps are as follows:

[0116] (1) The components prepared in Examples 1-3 and Comparative Examples 1-5 were prepared into sample prisms of 40mm×40mm×160mm according to the requirements of GB / T 17671, and three were prepared for each group.

[0117] (2) After molding, the sample is placed in a standard curing box for 24 hours and then demolded. Then, it is cured in an environment with a temperature of (20±1)℃ and a relative humidity of not less than 95% until 28 days of age.

[0118] (3) After curing, remove the specimen. First, test the flexural strength on the flexural testing machine and record the load at fracture.

[0119] (4) The two broken pieces formed after the flexural test are used as the specimens for the compressive strength test. The test is carried out on the compressive strength testing machine, and the maximum pressure when the specimen fails is recorded.

[0120] (5) Calculate the flexural strength and compressive strength of each group of samples according to the standard formula, and take the arithmetic mean of the three samples.

[0121] The experimental results are shown in Table 3 and Figure 3 As shown.

[0122] Table 3. Results of mechanical property tests for each sample after 28 days:

[0123] Test object Compressive strength (MPa) Flexural strength (MPa) Example 1 38.7 6.9 Example 2 43.1 7.8 Example 3 41.5 7.5 Comparative Example 1 5.4 1.2 Comparative Example 2 25.8 4.6 Comparative Example 3 35.2 6.3 Comparative Example 4 36.1 6.5 Comparative Example 5 19.3 3.7

[0124] Mechanical property test data show that the cured bodies prepared in Examples 1-3 have high compressive strength and flexural strength. The 28-day compressive strength of Examples 1-3 all exceeds 38 MPa, and the flexural strength is close to 7 MPa, demonstrating the application potential of this material as a building material.

[0125] Comparative Example 1, without mechanochemical activation, exhibited a 28-day compressive strength of only 5.4 MPa, indicating that the original activity of the fly ash raw material was extremely low and could not support an effective geological polymerization reaction. This confirms that mechanochemical activation is a necessary step in activating the activity of fly ash and pozzolanic ash. Its role is to disrupt the inert glassy structure on the surface of fly ash particles, increase the specific surface area, and provide more active sites for subsequent reactions.

[0126] Comparative Example 2, activated at a constant high speed, showed a significant improvement in strength compared to Comparative Example 1, but it was still significantly lower than Examples 1-3. This indicates that the variable frequency mechanochemical process used in this invention, through the regulation of energy input, can more effectively optimize the particle morphology and gradation of the composite powder, avoiding problems such as particle agglomeration or reduced amorphization caused by excessive grinding, and is conducive to forming a harder structure with denser filling and fewer defects.

[0127] Comparative Example 5 used a traditional water washing method to pretreat fly ash. Although the mechanical properties were better than those of the unactivated Comparative Example 1 by removing inhibitory salts, the strength was still lower than that of the embodiments of the present invention. At the same time, the water washing method generates waste liquid containing high concentrations of chloride salts and heavy metals, which constitutes secondary pollution, increases the complexity of the process and environmental costs, and does not conform to the principle of efficient and low-carbon resource utilization of solid waste.

[0128] In summary, the technical solution of this invention, through the synergistic effect of frequency conversion mechanical chemical activation process and composite additives, not only achieves in-situ, one-step treatment of pollutants, but also effectively enhances the material properties of fly ash. The activated highly active powder, under alkaline activation conditions, can undergo a full geopolymerization reaction, forming a more dense and uniform aluminosilicate geopolymer network structure.

[0129] Test Example 4:

[0130] The experimental steps are as follows:

[0131] (1) Take the final cured samples (cured for 28 days) prepared in Examples 1-3 and Comparative Examples 1-5 respectively, crush them with a jaw crusher and pass them through a 5mm sieve.

[0132] (2) Weigh 100g of each group of samples and perform horizontal shaking leaching according to HJ 557-2010. Use sulfuric acid / nitric acid as leaching agent, and adjust the amount of acid during shaking so that the pH of the liquid at the end of leaching is 5.0±0.05 and the liquid-to-solid ratio is 10L / kg.

[0133] (3) The sample was continuously oscillated at 110 r / min for 8 h at (23±2) ℃ and then left to stand for 16 h.

[0134] (4) Use a 0.45μm microporous membrane to pressurize and filter the leachate.

[0135] (5) Take the filtrate and, in accordance with HJ 700-2014, use inductively coupled plasma mass spectrometry (ICP-MS) to detect the concentrations of lead (Pb), cadmium (Cd), zinc (Zn), and chromium (Cr) in the leachate.

[0136] The experimental results are shown in Table 4 and Figure 4 As shown.

[0137] Table 4. Heavy metal concentrations (mg / L) in leachates of each sample:

[0138] Test object Lead (Pb) Cadmium (Cd) Zinc (Zn) Chromium (Cr) Example 1 0.038 0.0016 0.17 0.065 Example 2 0.031 0.0013 0.15 0.058 Example 3 0.045 0.0021 0.23 0.071 Comparative Example 1 15.6 0.95 38.4 4.3 Comparative Example 2 0.19 0.008 0.88 0.45 Comparative Example 3 0.041 0.0017 0.19 0.069 Comparative Example 4 0.043 0.0019 0.2 0.066 Comparative Example 5 1.15 0.032 4.7 1.8

[0139] Test results show that the leaching concentrations of Pb, Cd, Zn, and Cr in samples of Examples 1-3 are all far below the limits of GB 16889-2008, indicating that the technical solution of the present invention can achieve stable curing of heavy metals under different parameter combinations.

[0140] Comparative Example 1, without mechanical activation, had an extremely high concentration of heavy metal leaching, proving that direct mixing of fly ash raw materials cannot form an effective solidified matrix. Mechanochemical activation is a prerequisite for forming a dense polymer structure to achieve physical encapsulation.

[0141] Comparative Example 2 used a constant high rotation speed, and although its leaching concentration was lower than the standard, it was still significantly higher than that of the Example. This shows that the frequency conversion program of the present invention helps to form a higher quality and denser geopolymer matrix, thereby improving the effect of physical encapsulation.

[0142] Comparative Examples 3 and 4 lacked oxidants and reducing agents, respectively, yet their heavy metal leaching concentrations were close to those of the examples. This phenomenon indicates that zero-valent iron and persulfate are mainly used for the degradation of organic pollutants in this technical solution, and do not play a decisive role in the solidification of heavy metals. The solidification of heavy metals mainly depends on other components in the system.

[0143] Comparative Example 5, using a traditional water washing method, showed a significantly higher leaching concentration than the example. This indicates that water washing can only remove some water-soluble heavy metals, while this invention achieves in-situ chemical fixation of heavy metals by introducing apatite group minerals into the system. During the reaction, phosphate ions react with lead ions to form chemically stable mineral phases such as chlorapatite and pyrite. This chemical fixation mechanism fundamentally reduces the activity and migration ability of heavy metals, and its effect is far superior to simple physical water washing.

[0144] Therefore, the test results confirm that the present invention achieves efficient and stable solidification of heavy metals by combining the chemical fixation of apatite group minerals with the physical encapsulation of geopolymers induced by mechanochemical activation.

[0145] Test Example 5:

[0146] The experimental steps are as follows:

[0147] (1) Samples from Example 1, Comparative Example 1, and Comparative Example 2 were selected for testing. Comparative Example 1 represents the unactivated baseline, Comparative Example 2 represents the conventional mechanochemical method, and Example 1 represents the present invention.

[0148] (2) Prepare multi-component sample prisms with a molding size of 40mm×40mm×160mm using each component according to GB / T 17671.

[0149] (3) After curing all samples in a standard curing chamber (temperature (20±1)℃, relative humidity ≥95%) for 24 hours, they were demolded and continued to be cured under the same conditions.

[0150] (4) When the age reaches 3 days, 7 days, 14 days and 28 days respectively, three samples are taken from each group and their compressive strength is tested according to GB / T17671.

[0151] (5) Record the average compressive strength at each age.

[0152] The experimental results are shown in Table 5 and Figure 5 As shown.

[0153] Table 5. Compressive strength (MPa) of each sample at different ages:

[0154] Maintenance period (days) Example 1 Comparative Example 1 Comparative Example 2 3 18.2 1.1 10.5 7 29.5 2.6 18.3 14 35.1 3.9 22.9 28 38.7 5.4 25.8

[0155] Compressive strength test data at different ages show that the sample in Example 1 exhibited high strength (18.2 MPa) in the early stage (3 days), and the strength had developed to 29.5 MPa by 7 days, approaching 75% of its final strength. This indicates that the variable frequency mechanochemical process of the present invention generates a large number of highly reactive aluminosilicate precursors through effective activation of the composite powder. These precursors can rapidly undergo geopolymerization reactions under alkali activation, quickly forming a load-bearing gel network structure, thus resulting in rapid strength development of the material.

[0156] The strength development of the sample in Comparative Example 1 was extremely slow, with a strength of only 5.4 MPa after 28 days. This confirms that fly ash raw materials that have not undergone mechanochemical activation treatment have extremely low pozzolanic activity, and the degree and rate of geological polymerization reaction are severely insufficient, making it impossible to form effective structural strength.

[0157] Comparative Example 2, treated with a constant high rotation speed, showed a strength development rate and final strength between those of Example 1 and Comparative Example 1. Although conventional high-energy ball milling can also activate some fly ash, its strength development process is significantly slower than that of Example 1. This may be because while continuous high-energy input can break down particles, it can also lead to over-grinding or agglomeration, resulting in a suboptimal particle size distribution that affects the filling efficiency and microstructure density of the subsequent geopolymer gel. The variable frequency program of this invention, through the combination of low-temperature activation and high-energy pulses, can more precisely control the particle grinding and activation process, producing precursors with a more reasonable particle size distribution and higher surface activity, thereby making the geopolymerization reaction more efficient and thorough.

[0158] Based on the results of tests 1 to 5, this technical solution achieves the harmlessness and resource utilization of waste incineration fly ash simultaneously through an integrated processing flow.

[0159] Data from Test Example 1 demonstrates the effective degradation of organic pollutants using the variable frequency mechanochemical method. By controlling the energy input in a time-series manner, this method promotes the reductive dechlorination of PCDD / Fs by zero-valent iron during the low-temperature activation stage, followed by triggering the oxidative decomposition of PAHs by persulfate during the high-energy pulse stage. This mechanism solves the problem of mutual consumption between oxidants and reductants in a constant high-energy field, resulting in degradation rates of 94.4% for PCDD / Fs and 89.5% for PAHs, significantly superior to the effect of constant rotation speed treatment.

[0160] Test Examples 2 and 4 systematically verified the environmental safety of the products. The heavy metal leaching concentrations of the products in all examples were far below the limits specified in GB 16889-2008. Analysis of the comparative examples showed that the stable solidification of heavy metals did not depend on the organic matter degradation system, but rather on the chemical fixation induced by apatite group minerals, combined with the physical encapsulation barrier formed by the geological polymerization reaction. This chemical fixation mechanism transforms heavy metals in situ into stable mineral-like phases, with effects far superior to the traditional water washing pretreatment method in Comparative Example 5.

[0161] Test Examples 3 and 5 demonstrate the material value of the products from both the final performance and development process perspectives. The 28-day compressive strength of the cured bodies in both examples exceeded 38 MPa, providing a mechanical basis for use as building materials. The strength development curve (Test Example 5) shows that the sample exhibited rapid strength growth in the early stages of the reaction. This indicates that the variable frequency mechanochemical process not only activated the fly ash but also optimized the particle size distribution and reactivity of the powder, promoting a faster and more complete geopolymerization reaction, ultimately forming a denser microstructure. This explains why its mechanical properties are superior to those of unactivated (Comparative Example 1) or samples activated using a constant rotation speed (Comparative Example 2).

[0162] In summary, the core of this invention lies in the variable frequency mechanochemical process. This process, through precise control of reaction energy, synergistically drives chemical reactions with different mechanisms in a single process step, degrading persistent organic pollutants while activating the inorganic substrate. The subsequent geopolymerization reaction not only endows the product with high mechanical strength, but the resulting dense matrix also acts as a second barrier to stabilize heavy metals, ultimately transforming highly polluting waste incineration fly ash into environmentally safe and usable materials.

[0163] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A polymer composite material for waste incineration fly ash, characterized in that, Made from raw materials comprising the following parts by weight: Waste incineration fly ash: 100 portions; Apatite group minerals: 3-10 parts; Zero-cost iron powder: 1-5 parts; Persulfate: 1-5 parts; An alkaline activator, wherein the alkaline activator is composed of 30-50 parts of sodium silicate solution and 10-25 parts of sodium hydroxide solution; The waste incineration fly ash, apatite group minerals, zero-valent iron powder, and persulfate are pre-treated with a variable frequency mechanical-chemical synergistic activation process, which includes a low-temperature activation stage and a high-energy pulse activation stage, before being mixed with the alkaline activator.

2. The waste incineration fly ash-polymer composite material according to claim 1, characterized in that, The apatite group minerals are phosphate rock powder or hydroxyapatite.

3. The waste incineration fly ash-polymer composite material according to claim 2, characterized in that, When the apatite group mineral is hydroxyapatite, it is prepared by the following steps: (1) Under the condition of pH value of 10-11, diammonium hydrogen phosphate solution is added dropwise to calcium nitrate solution to carry out the reaction and obtain a suspension; (2) The suspension is aged, filtered, washed and dried to obtain the hydroxyapatite.

4. The waste incineration fly ash-polymer composite material according to claim 1, characterized in that, The concentration of the sodium hydroxide solution is 8–14 mol / L; and / or the modulus of the sodium silicate solution is 2.5–3.

0.

5. A method for preparing a polymer composite material from waste incineration fly ash according to any one of claims 1-4, characterized in that, Includes the following steps: (a) A composite powder is obtained by mixing waste incineration fly ash, apatite group minerals, zero-valent iron powder and persulfate; (b) The composite powder is subjected to frequency conversion mechanical and chemical synergistic activation to obtain activated composite powder. The activation process includes a low-temperature activation stage and a subsequent high-energy pulse activation stage. (c) The activated composite powder from step (b) is mixed with an alkaline activator to obtain a slurry; (d) The slurry is poured into shape and cured.

6. The preparation method according to claim 5, characterized in that, The synergistic activation described in step (b) is carried out in a planetary ball mill with a ball-to-material mass ratio of (15-25):

1.

7. The preparation method according to claim 6, characterized in that, The rotation speed during the low-temperature activation stage is 250–350 rpm, and the duration is 75–150 min.

8. The preparation method according to claim 7, characterized in that, The high-energy pulse activation phase includes running at a speed of 500-700 rpm, then pausing, and repeating this running and pausing process.

9. The preparation method according to claim 8, characterized in that, During the high-energy pulse activation phase, the pulse is run at 500-700 rpm for 3-5 minutes, paused for 1-2 minutes, and the process is repeated 4-6 times.

10. The preparation method according to claim 5, characterized in that, The curing temperature in step (d) is 20–70°C, and the curing time is 6–24 hours.

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