A method for enhancing micropollutant degradation during sludge composting through ferrocarrier-mediated biological-abiotic synergistic process.

Abstract

This invention provides a method for enhancing the degradation of micropollutants during sludge composting through a synergistic biological-abiotic process mediated by an iron carrier. First, an iron-based catalyst is prepared by mixing zero-valent iron powder with a deferroamine (DFO) solution. Then, dewatered sludge containing micropollutants is mixed uniformly with a conditioner in a specific ratio. The iron-based catalyst is added to the mixture, and the mixture is then subjected to aerobic composting. After composting, the removal rate of micropollutants in the compost is greater than 80%. This invention overcomes the shortcomings of existing technologies, such as low degradation efficiency, high cost, risk of secondary pollution, and separation of biological and abiotic processes. It effectively solves the key bottleneck of "microbial iron limitation" in existing composting systems, achieving a highly efficient synergistic biological-abiotic strategy, and possesses advantages such as high efficiency, economy, and environmental friendliness.

Description

Technical Field

[0001] This invention belongs to the field of sludge resource utilization and environmental pollutant control technology, specifically involving a method for enhancing the degradation of micropollutants during sludge composting through ferrocarrier-mediated biological-abiotic synergistic effects. Background Technology

[0002] Traditional sludge composting relies on the natural degradation capabilities of native microorganisms within the composting system, promoting the mineralization and stabilization of organic matter by controlling environmental parameters such as temperature, humidity, C / N ratio, and ventilation. However, this method has significant drawbacks when treating micropollutants such as antibiotics, hormones, and drug residues. On the one hand, due to the complex structure, high toxicity, and low concentration of these pollutants, microorganisms often lack efficient degradation enzyme systems or are easily inhibited, resulting in low degradation efficiency (typically <70%), long cycles, and unstable effects, and potentially promoting the generation and spread of resistance genes (ARGs). On the other hand, the sludge composting environment is neutral to alkaline (pH=6~8), where iron mainly exists as insoluble Fe. 3+ The presence of iron in oxide / hydroxide form results in bioavailable iron (dissolved Fe). 2+ Fe 3+ The severe deficiency of iron directly limits the activity of key iron-dependent microbial enzymes (such as peroxidase and oxygenase) and restricts the growth and metabolism of the microorganisms themselves, further weakening the system's ability to degrade pollutants. These deficiencies collectively limit the effective removal of micropollutants by traditional composting methods.

[0003] In existing technologies, enhancing the removal of micropollutants by directly adding specific additives to the composting system is a common strategy. These methods primarily rely on the abiotic effects of the additives, such as adding chemical oxidants like persulfates and Fenton's reagent, utilizing the free radicals they generate (e.g., SO42-). -(e.g., Cheng Boyi et al. applied for a method to enhance the anaerobic degradation of chlorinated organophosphates in sludge using thiosulfate, application number: CN202510430333.6, which accelerates the anaerobic reduction dechlorination process of chlorinated organophosphates in sludge through thiosulfate, increasing the degradation rate of chlorinated organophosphate pollutants by 61.1~123%); adding adsorption / catalytic materials such as biochar and iron minerals to remove pollutants using their adsorption performance or catalytic activity (e.g., Yu Runlan et al. applied for a method to promote the degradation of polycyclic aromatic hydrocarbons by sludge composting, application number: CN202311335404.1, which uses natural vermiculite powder (addition amount 1%), and uses its catalytic performance to increase the degradation rate of polycyclic aromatic hydrocarbons by 21.1%; Cheng Dengmiao et al. applied for a method to fix heavy metals and degrade antibiotics by sludge composting, patent number: CN202211222715.2, which uses biochar loaded with tin sulfide to adsorb and reduce heavy metals, while adsorbing antibiotics). However, this type of method based on the non-biological action of additives has significant drawbacks: on the one hand, the method that relies on chemical oxidants consumes a large amount of oxidants, resulting in high costs. Excessive oxidants or their reaction byproducts can inhibit or even destroy microbial activity and disrupt the ecological balance of composting. On the other hand, it is often difficult to achieve the complete mineralization and degradation of pollutants by fixing or partially transforming them through adsorption or limited catalysis.

[0004] Existing technologies include reports on the use of zero-valent iron (ZVI), iron salts, and iron ore to provide essential iron nutrients for sludge composting microorganisms and alleviate iron limitation. These microorganisms utilize the corrosive or redox properties of iron (such as the production of Fe by ZVI corrosion). 2+ This method involves initiating a Fenton-like reaction to degrade pollutants. However, it has significant drawbacks: firstly, the iron source has poor solubility and bioavailability—ZVI dissolves slowly, while Fe... 3+ Salts are easily oxidized or form insoluble precipitates (such as hydroxides) in composting environments (especially alkaline stages), making it difficult for microorganisms to efficiently absorb and utilize iron. Secondly, the expected abiotic oxidation efficiency is low and uncontrollable—the abundant organic matter in the composting system quenches free radicals, and the drastic fluctuations in pH and temperature result in low efficiency, short duration, and unpredictable reactive oxygen species (ROS) generated by reactions such as Fenton. Finally, the addition of iron sources and the microbial metabolic processes lack effective synergy, failing to form a mutually promoting degradation network, thus limiting overall efficiency. Summary of the Invention

[0005] To address the shortcomings of existing technologies, such as low degradation efficiency, high cost, risk of secondary pollution, and separation of biological and non-biological processes, this invention provides a method for enhancing the degradation of micropollutants in sludge composting through iron carrier-mediated biological-non-biological synergy. This method overcomes the above-mentioned shortcomings, effectively solves the key bottleneck of "microbial iron limitation" in existing composting systems, and realizes a strategy of efficient biological-non-biological synergy, which has the advantages of high efficiency, economy, and environmental friendliness.

[0006] The technical solution adopted to achieve the above-mentioned objectives of this invention is as follows:

[0007] A method for siderophore-mediated bio-abiotic synergistic enhancement of micropollutant degradation during sludge composting, wherein the micropollutants include antibiotics, hormones, and drug residues, includes the following steps:

[0008] (1) Zero-valent iron powder and deferroamine DFO solution are mixed evenly under nitrogen protection and reacted fully at room temperature so that the isohydroxamic acid group in deferroamine DFO is coordinated and bonded to the ≡Fe-OH site on the surface of zero-valent iron powder. After the reaction is completed, the solid is collected by centrifugation, washed and dried to obtain the iron-based catalyst.

[0009] (2) Mix the dewatered sludge containing micro-pollutants with the conditioner at a wet weight ratio of 3:1 to 5:1, adjust the initial moisture content of the stockpile to 55 to 65%, and adjust the C / N ratio to 25 to 30; then add the iron-based catalyst from step (1) to the mixture, with the added iron-based catalyst accounting for 0.5% to 2% of the dry weight of the mixture.

[0010] (3) The mixed materials are aerobic composted. During the composting process, the ambient temperature is controlled to be 3-5°C lower than the internal temperature of the pile. The bottom of the pile is aerated to maintain the oxygen content in the gas inside the pile >10%. The composting process goes through the heating period, high temperature period, cooling period and decomposition period. After the composting is completed, the removal rate of micro-pollutants in the pile is greater than 80%.

[0011] Furthermore, in step (1), the zero-valent iron powder is selected as 80~100 mesh industrial grade zero-valent iron powder, which is washed with oxygen-free water until neutral and then vacuum dried.

[0012] Furthermore, in step (1), the concentration of deferroamine DFO is 10 mM, the solid-liquid ratio of zero-valent iron powder to deferroamine DFO solution is 1 g: 100 mL, and the reaction is carried out by shaking at 25°C for 2 h.

[0013] Furthermore, the solid after centrifugation in step (1) was washed three times with anaerobic PBS buffer to remove physically adsorbed impurities, and then freeze-dried at -50℃ for 24 h to obtain the final product, iron-based catalyst.

[0014] Furthermore, in step (2), the conditioner is made from corn stalks.

[0015] Furthermore, in step (3), the compost is placed in a composting reactor for aerobic composting. The outer wall of the composting reactor is equipped with an auxiliary circulating water temperature control system. An aeration port is provided at the bottom of the composting reactor.

[0016] Furthermore, in step (3), the temperature, oxygen concentration, pH value, and volatile solids parameters of the compost pile are monitored during the composting process.

[0017] Furthermore, in step (3), fresh samples are periodically taken from the stockpile, and the changes in iron carrier concentration in the stockpile are monitored using the CAS detection method and HPLC-MS method. The Fe concentration in the stockpile is detected using the o-phenanthroline method. 2+ and Fe 3+ As concentration changes during composting, assess bioactivity and iron limitation status.

[0018] Furthermore, in step (3), high performance liquid chromatography (HPLC) was used to detect the change in the concentration of -OH generated during the composting cycle. The specific method was as follows: 5g of fresh compost sample was weighed and placed in a 50 mL Erlenmeyer flask, 20 mL of 10 mM sodium benzoate solution was added, and after mixing evenly, the mixture was placed in a constant temperature shaker and shaken in the dark for 30 min. The reaction temperature was set to the composting temperature at the time of sample collection. After the reaction was completed, 1 mL of the suspension was measured and chromatographed at 12000 rpm·min. -1 Centrifuge for 3 min, filter through a 0.22 µm organic filter membrane, and finally use HPLC to determine the concentration of p-hydroxybenzoic acid.

[0019] Furthermore, in step (3), changes in the concentration of micropollutants in the pile are monitored periodically to assess the degradation effect.

[0020] Compared with existing technologies, the method for enhancing the degradation of micropollutants in sludge composting through ferrocarrier-mediated biological-abiotic synergistic enhancement provided by this invention has the following advantages:

[0021] 1. This invention utilizes an iron carrier to efficiently chelate, dissolve, and transport iron (especially Fe). 3+1. This invention significantly improves the bioavailability of iron by composting microorganisms and activates their endogenous degradation enzyme system; 2. This invention constructs a biological-abiotic synergistic system, using iron carrier-iron complex (Fe-Siderophore) as a "molecular bridge" and "electron shuttle" to activate iron-based catalysts (abiotic components) in situ and continuously under the drive of microbial metabolism, generating highly active free radicals to oxidize recalcitrant pollutants or their stubborn intermediates; 3. This invention can achieve deep, efficient, and stable removal of micropollutants: through the above synergistic effect, it significantly improves the degradation rate and final removal rate (target >80%) of emerging micropollutants such as antibiotics, hormones, and drug residues in the sludge composting process. Attached Figure Description

[0022] Figure 1 Scanning electron microscope images of zero-valent iron (ZVI) and supported zero-valent iron (SRC@ZVI);

[0023] Figure 2 Elemental surface distribution diagram for loaded zero-valent iron SRC@ZVI;

[0024] Figure 3 Infrared spectra of zero-valent iron (ZVI) and supported zero-valent iron (SRC@ZVI);

[0025] Figure 4 This is a diagram illustrating the ferrocarrier-mediated synergistic mechanism in an embodiment of the present invention.

[0026] Figure 5 This is a graph showing the changes in iron content and speciation during sludge composting.

[0027] Figure 6 This is a graph showing the changes in ·OH content during sludge composting.

[0028] Figure 7 This is a graph showing the changes in the degradation rate of micropollutants during sludge composting. Detailed Implementation

[0029] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. However, the scope of protection of the present invention is not limited to the following embodiments.

[0030] (1) Preparation of iron-based catalysts

[0031] Zero-valent iron (80-100 mesh) with high specific surface area, good adsorption performance, and environmental compatibility was selected. A low-concentration, specifically structured iron support—deferroamine DFO—was introduced, partially modifying the catalyst surface or embedding it into the pores. This step is crucial, enabling it to exhibit "iron support responsiveness." The iron support is designated Sidephore-Responsive Catalyst (SRC), and the final iron-based catalyst is designated SRC@ZVI.

[0032] First, 80-100 mesh industrial-grade zero-valent iron powder (ZVI) was washed with oxygen-free water until neutral and then vacuum dried. Subsequently, under nitrogen protection, ZVI was mixed with a 1.0 mM deferroamine (DFO) solution at a ratio of 1 g:100 mL and reacted at 25°C with shaking for 2 h, allowing the isohydroxamic acid groups of DFO to coordinate and bond with the ≡Fe-OH sites on the ZVI surface. After the reaction, the solid was collected by centrifugation, washed three times with oxygen-free PBS buffer to remove physically adsorbed impurities, and then freeze-dried under vacuum (-50°C, 24 h) to obtain the final product SRC@ZVI. This catalyst exhibits "iron support responsiveness," meaning that the free DFO terminal can specifically chelate environmental Fe. 3+ And under the action of microbial reduction, the surface Fenton-like reaction is activated.

[0033] The iron-based catalyst SRC@ZVI and zero-valent iron powder (ZVI) prepared in this embodiment were characterized simultaneously, and their scanning electron microscope images are shown below. Figure 1 As shown, Figure 1 Medium scale: (a, d) 10 μm, (b, e) 2 μm, (c, f) 1 μm Figure 1 In the figure, abc represents zero-valent iron powder (ZVI), and def represents the iron-based catalyst SRC@ZVI prepared in this example. Figure 1 As can be seen from the image, compared to the original spherical ZVI particles (Fig. ac), the SRC@ZVI sample (Fig. df) loaded with DFO exhibits a distinct "flocculent" adhesion structure on and around its surface. This morphological change provides a direct morphological basis for the successful loading of DFO onto the ZVI surface.

[0034] The elemental surface distribution diagram of the iron-based catalyst SRC@ZVI prepared in this embodiment is as follows: Figure 2 As shown, Figure 2 (a) SEM image, (b) EDS full spectrum, (c) C, (d) O, (e) N, (f) Fe. Further elemental surface distribution analysis shows (see...) Figure 2 As shown in the figure, the aforementioned "flocculated" structural region is rich in C and N elements. Since N is unique to DFO molecules rather than ZVI itself, this result clearly identifies the flocculent material as loaded DFO, thus confirming its successful modification in terms of spatial elemental distribution.

[0035] The infrared spectra of the iron-based catalyst SRC@ZVI and zero-valent iron powder (ZVI) prepared in this embodiment are as follows: Figure 3 As shown, from Figure 3 It can be seen that the infrared spectrum of the original ZVI is almost entirely within the range of 1500–2500 cm⁻¹. -1 The region exhibits no significant absorption and lacks the characteristic absorption of organic functional groups. This characteristic is consistent with reported zero-valent iron and magnetite materials, indicating that the bare ZVI surface is inactive in the infrared, reflecting only the skeletal vibrations of a small amount of oxide layer. In contrast, the modified SRC@SRC samples show absorption in the 1000–1400 cm⁻¹ region. -1 and 2850–3000 cm -1 Multiple new peaks appeared in the region, and their intensity increased significantly. These peaks correspond to 1062 cm⁻¹, respectively. -1 (C–O / N–O stretching, hydroxyoxime characteristic), 1218 and 1255 cm -1 (C–N / C–O expansion / contraction), 1395 cm -1 (COO⁻ symmetrical stretching or CH2 bending), and 2904 and 2984 cm -1 (Aliphatic C–H stretching). These absorption bands are highly consistent with the characteristic peaks of the hydroxyoxime, amide, and aliphatic chains in the desferrioxamine B (DFO) structure. Meanwhile, the SRC@SRC spectrum at 3668 cm⁻¹... -1 The sharp –OH stretching peaks at the surface can be attributed to isolated or structured hydroxyl groups on the surface of goethite-type iron oxides, indicating that ordered surface –OH sites are involved in coordination.

[0036] (2) Sludge composting method based on ferrocarrier-mediated synergistic effect

[0037] (2.1) Sludge pretreatment and mixing

[0038] The dewatered sludge to be treated was mixed with a conditioning agent (corn stalks) in a suitable ratio (wet weight ratio 3:1~5:1) to adjust the initial moisture content (55~65%) and C / N ratio (25~30). A mixed standard aqueous solution of pollutants was added (in this embodiment, ofloxacin (OFL), fluoxetine (FLX), and carbamazepine (CBZ) were selected as micro-pollutant samples, and the concentration of each of the three was 10 mg / L) to make the amount of micro-pollutants added in the material reach 1.0 mg / kg (dry matter); and the prepared iron-based catalyst (SRC@ZVI) was uniformly incorporated into the mixture in a certain proportion (0.5%~2% w / w dry basis).

[0039] Three experimental groups and one blank control group were set up: zero-valent iron (ZVI), zero-valent iron-loaded (SRC@ZVI), and control group (RS, no addition). Each group was tested three times. The zero-valent iron group and the zero-valent iron-loaded group contained 1.0 mg / kg of OFL, FLX, and CBZ (dry matter).

[0040] (2.2) Establishment of sludge composting process

[0041] The mixed materials are placed in a composting reactor for aerobic composting. The reactor's outer wall has an auxiliary circulating water temperature control system, with the circulating water temperature set 3-5°C lower than the compost temperature. Aeration is performed at the bottom of the compost to maintain an oxygen content (>10%), meeting the needs of aerobic microorganisms and providing oxidants (O2) for abiotic oxidation. The entire composting process involves a heating phase (maintaining >55°C for several days to kill pathogens), a high-temperature phase (45-55°C, the main degradation phase), a cooling phase, and a maturation phase, totaling 35 days.

[0042] (2.3) Process monitoring and control

[0043] (2.3.1) Monitor conventional parameters such as reactor temperature, oxygen concentration, pH, and volatile solids (VS).

[0044] (2.3.2) Fresh samples of 10 g were taken periodically (0, 2, 5, 9, 14, 28, 35 days) to monitor the changes in iron carrier concentration in the stockpile using CAS detection and HPLC-MS methods, and Fe in the stockpile was detected using the o-phenanthroline method. 2+ and Fe 3+ As concentration changes during composting, assess bioactivity and iron limitation status.

[0045] (2.3.3) High-performance liquid chromatography (HPLC) was used to detect the changes in the concentration of ·OH generated during the composting cycle. 5g of fresh compost sample was weighed and placed in a 50 mL Erlenmeyer flask. 20 mL of 10 mM sodium benzoate solution was added, and the mixture was thoroughly mixed. The flask was then placed in a constant-temperature shaker and shaken in the dark for 30 min. The reaction temperature was set to the compost temperature at the time of sample collection. After the reaction, 1 mL of the suspension was measured and precipitated at 12000 rpm·min. -1 Centrifuge for 3 min, filter through a 0.22 µm organic filter membrane, and finally use HPLC to determine the concentration of p-hydroxybenzoic acid.

[0046] (2.3.4) Monitor changes in the concentration of target micropollutants (OFL, FLX and CBZ) and assess the degradation effect.

[0047] (3) Mechanism of action

[0048] (3.1) Core synergistic effect occurs (side carrier-mediated)

[0049] Reference Figure 4 Its mechanism of action can be roughly divided into the following four steps: Step A (Bio-initiation and iron dissolution and activation): In the early stage of composting, zero-valent iron (Fe) 0 It dissolves under the action of microbial activity, releasing Fe. 2+ These Fe 2+ Under aerobic conditions, it reacts with hydrogen peroxide (H2O2, mainly produced by aerobic microbial metabolism or formed by incomplete reduction of O2) or dissolved oxygen (O2) present in the composting environment (Fe(II) + O2 → Fe(III) + ·O2). - ), is oxidized to produce Fe 3+ This is accompanied by the generation of highly reactive oxygen free radicals (such as •OH, •O2). - At the same time, reduced humic substances (HS) red It is also oxidized in this process (HS). red +O2→HS ox + ·O2 - / H2O2), participates in free radical chain reactions and may generate environmentally persistent free radicals (EPFRs). The newly generated Fe 3+ It will rapidly and efficiently chelate with deferoxamine (DFO), the iron carrier added to the stockpile, to form soluble Fe. 3+ -Sid complex.

[0050] Step B (Bioutilization - Microbial Iron Uptake): Microorganisms recognize and take up Fe through specific receptors. 3+ -Sid, which is reduced to Fe within the cell. 2+ Later utilization. In addition, some free SiD or Fe... 3+ -Sid complexes diffuse and specifically bind to the surface of pre-modified iron-supported SRC catalysts. This binding has the following effects:

[0051] (i) Promotes the dissolution and recycling of iron on the SRC surface: Sid removes Fe from the passivation layer (such as Fe(III) oxide) on the catalyst surface. 3+ It dissolves to form Fe 3+ -Sid, which can then be reduced by microbial metabolism (such as HS). red The reducing components of the catalyst itself (such as quinones) or the reducing components (such as nZVI) are reduced to Fe. 2+ ;

[0052] (ii) In-situ initiation of highly efficient catalytic oxidation and continuous generation of free radicals: the generated Fe 2+It undergoes Fenton / Fenton-like reactions with H2O2 or dissolved oxygen (O2) present in the composting environment, continuously and efficiently generating highly reactive free radicals on and around the catalyst surface. Furthermore, the redox cycle of humic substances (HS) and possible surface reactions may also promote the generation of free radicals (such as •O2). - The generation of H2O2 and the formation of EPFRs further enhance the oxidation capacity.

[0053] Step C (Co-degradation of target pollutants): Highly reactive free radicals continuously generated on and around the catalyst surface oxidize and degrade micropollutants adsorbed on or around the SRC support in a nearby and efficient manner. These abiotic oxidation processes significantly reduce the toxic stress on microorganisms and remove the bottleneck of biodegradation.

[0054] Step D (Continuous Cycle and Self-Sustaining): The energy and reducing power generated by microbial degradation support its continuous secretion of Sid; Sid continuously dissolves iron (from the environment or regenerated by the catalyst) to supply the microorganisms and activate the catalyst; the free radicals generated by the catalyst efficiently remove recalcitrant substances, promoting overall degradation efficiency and microbial activity. This forms the process of "microbial secretion of Sid → Sid dissolving Fe". 3+ → Microorganisms utilize Fe to enhance degradation capacity / Sid activates catalysts → Catalysts generate reactive oxygen species (ROS) to degrade recalcitrant substances → Reduce toxicity and promote microbial growth → A positive feedback loop of "more Sid secretion".

[0055] (4) Technical effects

[0056] (4.1) Characteristics of iron content changes

[0057] Throughout the entire treatment cycle, the iron form exhibited a significant transformation pattern. See also... Figure 5 , Figure 5 Medium (a) ZVI Fe 2+ (b) ZVI Fe 3+ (c) SRC@ZVI Fe 2+ (d)SRC@ZVI Fe 3+ .from Figure 5 As can be seen, the content of ferric iron (Fe(III)) in all treatment groups increased rapidly and continuously from 0 to 21 days (slope Δ[Fe]). 3+ [ / Δt> 0.38 g / kg·d), which is mainly driven by the iron cycle process dominated by aerobic microbial oxidation (Fe 2+ + H2O2→·OH + Fe 3+ Meanwhile, the content of divalent iron (Fe(II)) exhibits dynamic fluctuations: in the early stage (0-9 days), Fe(II) shows a brief increase (the maximum increase Δ[Fe...]). 2+max ≈ 2.05 g / kg, Figure 2 a) This stems from the fact that reducing substances produced by the decomposition of organic matter (such as quinones and organic acids) promote the reduction of Fe(III) (reaction: Fe... 3+ +e - →Fe 2+ In the later stages (>15 days), the oxidation rate of Fe(II) slowed significantly (Δ[Fe)). 2+ [ / Δt < 0.5 g / kg·d], this is because the decrease in water content leads to enhanced oxygen diffusion, but the decline in microbial activity makes the natural oxidation process dominant, and the reaction kinetics slow down. Figure 5 Data from d SRC@ZVI_FLX corroborates this, showing that the Fe(II) peak appears on day 2 and is synchronized with the free radical peak, confirming that the Fe(III) reduction driven by the reducing substances in the early stage is the key process.

[0058] There are fundamental differences in iron cycling performance between the zero-valent iron (ZVI) group and the loaded zero-valent iron (SRC@ZVI) group. Comparing the ZVI and SRC@ZVI groups, in terms of Fe(II) supply capacity, the Fe(II) content in the ZVI group peaks on day 1 (16.67 g / kg) and then rapidly declines (decreasing by 76.69% by day 21), while the SRC@ZVI group not only has a higher peak (33.68 g / kg) but also maintains a content of 12.06 g / kg until day 5. This difference stems from the passivation layer formed on the ZVI surface, which hinders the continuous dissolution of iron, while the deferoxamine (DFO) layer modified on the SRC@ZVI surface promotes Fe(II) supply. 3+ Chelation-reduction cycle (microbial secretion of reducing substances → Fe) 3+ -DFO→Fe 2+ -DFO regeneration). Furthermore, different types of pollutants exhibit different regulatory effects on the iron cycle. Degradation intermediates (such as quinones) of pollutants containing benzene ring structures (e.g., FLX, OFL) can act as electron shuttles, significantly promoting Fe(III) reduction (increasing the Fe(II) peak by 20.41% in the SRC@ZVI group). Even without the addition of exogenous iron, the Fe(III) content in the control group (RS) still increased significantly by 8.3% (p<0.05). This result indicates that the native iron inherent in the sludge can spontaneously participate in the Fenton reaction, but its efficiency is limited, as reflected in the relatively low average free radical production at the peak (day two) (896.20 μmol / kg).

[0059] (4.2) Changes in free radical content

[0060] Regarding free radical production, see Figure 6 As shown, Figure 6In (a) ZVI; (b) SRC@ZVI. from Figure 6 As can be seen, the second day saw the peak of free radical production. Taking FLX as an example, the SRC@ZVI group showed a significant increase of 71.16% compared to the RS group (p<0.01), which was higher than the increase of 60.13% in the ZVI group compared to the CK group. This is attributed to the electron shuttle effect of DFO, which enhances Fe production. 2+ / Fe 3+ The improved turnover efficiency increased the amount of reactive oxygen species (ROS) generated per unit iron atom by 11.02%. Taking OFL as an example, the SRC@ZVI group showed a significant improvement of 61.87% compared to the RS group (p<0.01), which was higher than the improvement of the ZVI group compared to the CK group (52.30%), and the amount of ROS generated per unit iron atom increased by 9.57%. Taking CBZ as an example, the SRC@ZVI group showed a significant improvement of 61.54% compared to the RS group (p<0.01), which was higher than the improvement of the ZVI group compared to the CK group (34.77%), and the amount of ROS generated per unit iron atom increased by 26.77%.

[0061] (4.3) Degradation of micro-pollutants

[0062] Changes in the degradation rate of micropollutants, such as Figure 7 As shown in the figure, (a) ZVI; (b) SRC@ZVI. From Figure 7 The results show that the efficient degradation of various micropollutants mainly occurs during the warming and high-temperature phases of the composting process (degradation rate >40%), which highly coincides with the active conversion window of iron forms. Notably, the degradation cycle of the SRC@ZVI group is significantly extended. Its core advantage lies in the "microorganism-iron support-catalyst" ternary interface constructed through DFO, which breaks through the surface passivation bottleneck of traditional ZVI (extended Fe(II) activity cycle). This optimization of iron cycling directly drives the deep degradation of pollutants. The degradation rate of FLX is the most significant (+22.27%), attributed to its degradation intermediate (quinone compounds) acting as an electron shuttle, synergistically promoting the Fe(III) / Fe(II) cycle (Fe(II) peak ↑ 20.41%) with the DFO layer of SRC@ZVI, thereby enhancing the continuous generation capacity of ·OH. In addition, the degradation rate of CBZ and ofloxacin (OFX) increased by 18.51%.

[0063] The degradation advantage of the SRC@ZVI group is reflected in the following over time:

[0064] Early stage (0-2 days): Utilizing the reducing substances produced by the decomposition of organic matter to rapidly initiate the Fenton reaction, simultaneously degrading easily oxidizable pollutants; Mid-stage (2-14 days): Through DFO-mediated Fe... 3+ - Chelation reduction cycle (microbial secretion of reducing substances → Fe)3 + -DFO→Fe 2+ -DFO regeneration), maintaining a high Fe(II) concentration plateau period, continuously degrading stubborn pollutants (such as those containing benzene rings / heterocyclic structures); later stage (>14 days): steric hindrance effect slows down Fe 2+ Oxidation prolongs the tail-end degradation window of pollutants.

[0065] In summary, the SRC@ZVI technology provided by this invention transforms the pollutant degradation kinetics from an "early-stage pulse-like" to a "full-cycle continuous" one through long-term regulation of the iron cycle (Fe(II) slow release + Fe(III) efficient reduction). In particular, it improves the removal efficiency of benzene ring-containing pollutants (FLX / CBZ) and polar drugs (OFX) by 18.5% to 22.3%, providing a new paradigm for the targeted reduction of emerging pollutants in organic solid waste.

Claims

1. A method for iron carrier mediated biotic-abiotic synergistic enhancement of degradation of micro pollutants including antibiotics, hormones, pharmaceutical residues in sludge composting process, characterized in that The method comprises the following steps: (1) uniformly mixing zero-valent iron powder and deferoxamine DFO solution under nitrogen protection, and fully reacting at room temperature to make the hydroxamic acid group in the deferoxamine DFO and the surface ≡Fe-OH site of the zero-valent iron powder coordinately bond, then collecting the solid by centrifugation after the reaction, and washing and drying to obtain the iron-based catalyst; (2) uniformly mixing the dewatered sludge containing micro-pollutants and the conditioner at a wet weight ratio of 3:1 to 5:1, adjusting the initial pile moisture content to 55% to 65%, and adjusting the C / N ratio to 25 to 30; the conditioner is corn straw; then adding the iron-based catalyst in step (1) to the mixed material, and the mass percentage of the added iron-based catalyst in the dry weight of the mixed material is 0.5% to 2%; (3) performing aerobic composting on the mixed material, controlling the environmental temperature to be 3 to 5°C lower than the internal temperature of the pile during the composting process, causing the bottom of the pile to blow air, maintaining the oxygen content in the gas in the pile to be greater than 10%, and after the entire composting process goes through the temperature rising period, the high temperature period, the temperature decreasing period and the maturation period, the composting is completed, and the removal rate of the micro-pollutants in the pile after the composting is completed is greater than 80%.

2. The process for degradation of micro pollutants in iron-chelator mediated bio- abio synergistic sludge composting process as claimed in claim 1, wherein: In step (1), the zero-valent iron powder is an industrial-grade zero-valent iron powder with a mesh size of 80 to 100, which is washed to neutral with oxygen-free water and then vacuum dried.

3. The method of claim 1, wherein the process is characterized in that: In step (1), the concentration of the deferoxamine DFO is 10 mM, the solid-liquid ratio of the zero-valent iron powder and the deferoxamine DFO solution is 1 g:100 mL, and the oscillation reaction is performed at 25°C for 2 h.

4. The method of claim 1, wherein the process is characterized in that: In step (1), the solid after centrifugation is washed with oxygen-free PBS buffer for 3 times to remove physical adsorption impurities, and then vacuum freeze-dried at-50°C for 24 h to obtain the final product iron-based catalyst.

5. The method of claim 1, wherein the process is characterized in that: In step (3), the pile is placed in a composting reactor for aerobic composting, and the composting reactor has an auxiliary circulating water temperature control system on the outer wall; an aeration port is arranged at the bottom of the composting reactor.

6. The method of claim 1, wherein the process is characterized in that: In step (3), the temperature, oxygen concentration, pH value and volatile solid parameters of the pile are monitored during the composting process.

7. The method of claim 1, wherein the process is characterized in that: In step (3), fresh samples were periodically taken from the heap and the concentration of siderophores in the heap was monitored using the CAS assay and HPLC-MS method, and the concentration of Fe 2+ and Fe 3+ was monitored using the o-phenanthroline method. Changes in concentration with composting progress were evaluated, as well as biological activity and iron limitation status.

8. The method of claim 1, wherein the process is characterized in that: In step (3), the concentration change of -OH in the composting cycle is detected by high performance liquid chromatography. Specifically, 5 g of fresh compost sample is weighed into a 50 mL conical flask, 20 mL of 10 mM sodium benzoate solution is added, and after mixing evenly, it is placed in a constant temperature oscillator for reaction for 30 min in the dark. The reaction temperature is set to the compost temperature at the time of sample collection. After the reaction is completed, 1 mL of the suspension is taken and centrifuged at 12000 rpm·min -1 for 3 min, filtered through a 0.22 µm organic filter membrane, and finally the concentration of p-hydroxybenzoic acid is detected by HPLC.

9. The method of claim 1, wherein the process is characterized in that: In step (3), the change of the micro-pollutant concentration in the pile is monitored regularly to evaluate the degradation effect.

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