Co-encapsulated steel slag-persulfate long-acting organic pollution repairing material and application thereof

Abstract

The invention discloses a co-encapsulated steel slag-persulfate long-acting repair material and application thereof, and belongs to the technical field of underground water organic pollution repair. The material comprises an activated core layer and a controlled release encapsulation layer, the activated core layer is composed of industrial solid waste steel slag (SS) and sodium persulfate (SPS), the SS provides an alkaline buffer component (Ca < 2 + > / OH <->) and an iron activator (Fe < 2 + > / Fe < 3 + >), and the SPS serves as a free radical precursor; the controlled-release encapsulation layer is selected from a polymer matrix such as ethyl cellulose, and the mass ratio of the controlled-release encapsulation layer to the core layer is (0.8: 1) to (1.2: 1). The preparation method comprises the following steps: dry-mixing SS and SPS, adding polymer powder for secondary mixing, dropwise adding an organic solvent (such as ethyl acetate) to induce phase separation to form viscoelastic blocks, shaping particles and drying at low temperature.

Description

Technical Field

[0001] The present invention relates to the technical field of groundwater pollution remediation materials, and in particular to a long-lasting remediation material for a permeable reactive barrier (PRB), in particular to a functional composite material that co-encapsulates industrial solid waste and an oxidant through a polymer matrix. Background Art

[0002] The field of groundwater organic pollution remediation has long faced the dual challenges of short lifespan of treatment materials and poor environmental adaptability. Organic pollutants pose a serious threat to groundwater resources due to their carcinogenicity and persistence, and traditional technologies (such as extraction treatment) have problems such as incomplete remediation and easy recurrence. Although permeable reaction barriers can achieve continuous in-situ remediation, it is difficult for existing reaction materials to achieve both long-term effectiveness and stability: persulfate (PS) is a highly efficient oxidant, but its water solubility leads to rapid release, and it needs to rely on encapsulation technology (such as ethyl cellulose) to delay dissolution, but the efficiency of a single oxidant is significantly reduced under low temperature or complex water conditions; although steel slag (SS) is rich in alkaline components (Ca 2+ / OH - ) and iron-based activators (Fe 2+ / Fe 3+ ) can activate PS and neutralize acidic by-products, but direct use can cause a sudden rise in pH (>11.6) and uncontrolled dissolution of the activator, resulting in free radical quenching (SO4 - +OH - →SO4 2- +·OH) and the reaction is interrupted.

[0003] In response to the above-mentioned defects, the present invention proposes a co-encapsulation synergistic regulation system: steel slag and sodium persulfate (SS+SPS) are simultaneously embedded in a polymer matrix material to form a self-buffered composite material ((SS+SPS) / EC). This design achieves a breakthrough triple synergistic mechanism: first, the matrix material controls the gradient release of the SPS oxidant and the SS activation component to ensure the continuous action of the water-soluble active component; second, the gradual dissolution of the alkaline component in SS dynamically adjusts the pH to a stable range, avoiding the inactivation of free radicals caused by extreme alkalinity. The pH fluctuation amplitude of this system is reduced by 28% compared with the unencapsulated system, which is the sulfate radical (SO4 - ·) Create an optimal survival environment: Finally, Fe²⁺ / Fe³⁺ continuously activates SPS (S2O8 2- +Fe 2+ →SO4 - +SO4 2- +Fe 3+ ) generates highly active free radicals, while the surface-bound Fe³⁺ directly participates in electron transfer to degrade pollutants. The petroleum hydrocarbon removal rate under dual-path driving reaches 66.3%.

[0004] The innovative value of this technology lies in the dual dimensions of waste resource utilization and environmental adaptability: it converts steel slag solid waste into a functional activator, significantly reducing material costs; in-situ structural optimization occurs during the service life of the material (BET surface area increases by 156%, pore volume increases by 476%), promoting mass transfer and fixing sulfate by-products (Na2SO2, Na3Fe(SO4)3); it maintains a high removal rate at low temperatures and is tolerant to Cl - / HCO3 - It can remove interfering ions such as ions (efficiency>55%), providing a universal solution for complex groundwater environments. Summary of the Invention

[0005] This invention provides a method for preparing a polymer-matrix co-encapsulated steel slag-persulfate composite material and its application in organic pollution remediation. This method uses industrial solid waste steel slag (SS) and sodium persulfate (SPS) as core active components. These components are embedded into a polymer matrix such as ethyl cellulose, polystyrene, polymethyl methacrylate, and ethylene-vinyl acetate copolymer via solvent-induced phase separation, forming a three-dimensional network structure with sustained-release properties. The preparation process begins with raw material pretreatment: the steel slag is ball-milled to a powder to eliminate encapsulation defects; the sodium persulfate is selected to be a high-purity powder with a purity exceeding 99% to prevent impurities from interfering with free radical pathways.

[0006] The core process consists of four continuous steps: SS and SPS powders are first mechanically stirred at 300 rpm in a wide-mouth flask for 10 minutes to achieve primary mixing. An equal amount of polymer powder is then added and mixed for a secondary period of 10 minutes to form a uniform dry material system. During the solvent-induced granulation stage, a good organic solvent for the polymer, such as ethyl acetate, dichloromethane, or chloroform, is added dropwise to dissolve the polymer and adhere to the insoluble SS and SPS powders, reorganizing them into viscoelastic agglomerates. The resulting agglomerates are then cut into shapes using a granulator, pelletizer, or other shaping machine, depending on the intended use, and finally dried to form the final product.

[0007] The product exhibits three key advantages: morphological stability, with a spherical particle breakage rate of less than 2%, and irregular surface protrusions that increase specific surface area; encapsulation uniformity, as demonstrated by elemental distribution, with initial SPS and SS crystals uniformly dispersed within the polymer matrix. This preparation method achieves high-value waste recovery (100% steel slag utilization), and the resulting material exhibits long-term controlled release within a permeable reaction barrier, environmental adaptability (high efficiency in low-temperature groundwater environments), and resistance to interference from coexisting ions, providing an industrially viable solution for the remediation of organic contamination.

[0008] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the following detailed description, they are used to explain the present invention but do not constitute a limitation of the present invention. In the accompanying drawings: Figure 1 This is a cross-sectional SEM-EDS surface scanning analysis diagram of the composite sustained-release material obtained in Example 1. DETAILED DESCRIPTION

[0010] The technical solutions of the present invention will be fully described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. In the following examples, unless otherwise specified, all are commercially available chemical reagents, and there is no particular limitation to this.

[0011] Material synthesis: Ball milled steel slag powder (SS, particle size d 50 =35μm, Fe2O3 content 18wt%, specific surface area 1.2m² / g) and sodium persulfate (SPS, purity 99%) were added into an agate mortar at a mass ratio of 10:7 and dry-ground for 5 minutes until the color was uniform (off-white base with light yellow SPS spots).

[0012] Column experiment: 10.0 g of the mixture was packed into a φ5 cm × 10 cm borosilicate glass column (packing density 1.8 g / cm³). Simulated groundwater (pH 7.2 ± 0.1) containing 10 mg / L petroleum hydrocarbon (n-decane) and 150 mg / L Cl⁻ was introduced at a flow rate of 0.5 mL / min at 25°C using a constant-flow pump (HRT = 4 h). Operational monitoring revealed a sudden rise in the effluent pH to 11.8 ± 0.2 within 2 hours, accompanied by the precipitation of a reddish-brown flocculent precipitate at the bottom of the column (XRD confirmed Fe(OH)₃). After 6 hours, the petroleum hydrocarbon removal efficiency was only 28.5% (GC-MS: decrease in characteristic peaks at m / z 57, 71, and 85). Inductively coupled plasma ionization (ICP-OES) analysis revealed a total iron concentration of 8.3 ± 0.4 mg / L in the effluent, indicating a significant activator leakage. Example 1

[0013] Material Synthesis: 10.0 g of SS powder and 7.0 g of SPS powder were dry-mixed in a conical blender (IKA RW 20digital, 300 rpm) for 10 minutes to obtain a grayish-yellow composite powder. 17.0 g of ethyl cellulose (EC, viscosity 100 cps) powder was added, and mixing continued for 15 minutes until a homogeneous dry material system was formed. Using a constant-pressure dropping funnel, 20.4 mL of anhydrous ethanol (1.2 times the mass of the core layer) was added dropwise at a rate of 8 mL / min. The system gradually transformed into a milky white, viscoelastic mass (viscosity >5000 cP). The mass was then press-cut into 8 mm spherical pellets using a pelletizer (Hanbo HBZ-201) and cured in a forced-air drying oven at 50°C for 12 hours.

[0014] Column experiment validation: 100g of particles were packed into a φ5cm×40cm stainless steel reaction column (filling height 32cm). A 10mg / L petroleum hydrocarbon pollutant simulated solution was introduced at a controlled flow rate of 1.67mL / min for 20 consecutive days. Results: The petroleum hydrocarbon removal rate remained stable at 60.5-63.8% (daily average 62.1%). The online pH sensor recorded effluent pH values ​​fluctuating between 9.2-9.7 (average 9.4±0.3). ICP-OES analysis showed that the iron ion concentration was stable at 0.8-1.1 mg / L, and the cumulative dissolution amount accounted for only 2.3% of the total iron content of the material; SEM-EDS surface scanning analysis showed that the sodium persulfate component was evenly dispersed in the matrix (see Appendix). Figure 1 ). Example 2

[0015] Material Synthesis: 10.0 g SS and 7.0 g SPS were dry-blended in a V-blender (SYC-2L, 200 rpm) for 15 minutes. 15.3 g polymethyl methacrylate (PMMA, Mw = 120,000) powder was added and mixed for 20 minutes to form a uniform powder. 17.3 mL of dichloromethane (1.0 times the mass of the core layer) was added dropwise at 6 mL / min via a peristaltic pump (BT100-2J). The material gradually agglomerated into a pale yellow viscous paste (viscosity > 8000 cP). 6 mm φ cylindrical granules were prepared using an extruder granulator (LZ-120) and vacuum-dried at 60°C for 10 hours (solvent residue < 20 ppm).

[0016] Column experiment verification: 100g of particles were filled into a φ5cm×40cm organic glass column (filling height 32cm) to treat 5mg / L toluene and 200mg / L HCO3 -The system was tested for contaminated groundwater (8 ± 1°C) at a controlled flow rate of 2.5 mL / min (HRT = 8 hours) for 20 days. Data showed an average toluene removal rate of 83.6% (HPLC: peak area decay at 7.3 minutes retention time), with a still-high removal rate of 80.2% on day 20. Sieving analysis determined a particle breakage rate of only 0.28%.

[0017] The encapsulation material achieves micro-region confinement of the active components (SS / SPS) through solvent-induced phase separation technology. The particles form a dense encapsulation structure and the three-dimensional network of the polymer matrix (EC or PMMA) is used to regulate the release kinetics to ensure the following during the operation of the dynamic column: Long-term supply of oxidant: SPS supply time to the removal system is significantly improved; Activation component synergy: iron-based activator in SS (Fe 2+ / Fe 3+ ) and alkaline components (OH⁻) are released in a gradient manner to maintain the system. The present invention provides a method for preparing a polymer matrix material co-encapsulated steel slag-persulfate composite material and its application in organic pollution remediation. This method uses industrial solid waste steel slag (SS) and sodium persulfate (SPS) as core active components, and embeds them into polymer matrices such as ethyl cellulose, polystyrene, polymethyl methacrylate, and ethylene-vinyl acetate copolymer through solvent-induced phase separation technology to form a three-dimensional network structure with sustained release function. The preparation process begins with raw material pretreatment: steel slag is ball-milled to powder to ensure the elimination of encapsulation defects; sodium persulfate is selected from a high-purity powder of >99% to avoid impurities interfering with the free radical pathway.

[0018] The preferred embodiments of the present invention are described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the scope of protection of the present invention.

[0019] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0020] In addition, the various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed in the present invention. Yield>80 μmol / h.

Claims

1. A co-encapsulated steel slag-persulfate long-term repair material, characterized in that: Include: Activation core layer: It is composed of industrial solid waste steel slag (SS) and sodium persulfate (SPS), in which SS provides alkaline buffer components (Ca 2+ / OH - ) and iron-based activators (Fe 2+ / Fe 3+ ), SPS is a free radical precursor; Controlled-release encapsulation layer: at least one polymer matrix selected from ethyl cellulose, polystyrene, polymethyl methacrylate or ethylene-vinyl acetate copolymer; The mass ratio of the SS to the SPS is (8:7) to (12:7), and the mass ratio of the polymer matrix to the active core layer is (0.8:1) to (1.2:1).

2. The material according to claim 1, wherein The steel slag (SS) is ball milled to d 50 ≤38μm, and the iron oxide (calculated as Fe2O3) content is ≥15wt%, and the purity of the sodium persulfate (SPS) is >80%.

3. A method for preparing the material according to any one of claims 1 to 3, comprising: (a) Dry mix SS powder and SPS powder according to the proportion; (b) adding polymer matrix powder and mixing again; (c) adding an organic solvent dropwise to induce phase separation to form a viscoelastic mass, wherein the organic solvent is a low-boiling-point good solvent for the polymer, including ethyl acetate, dichloromethane, chloroform, or anhydrous ethanol; (d) The agglomerate is shaped into granules and dried at 40-70°C for solidification.

4. The method according to claim 3, wherein: In step (c), the organic solvent droplet acceleration rate is 5-10 mL / min, and the total amount is 0.7-1.5 times the mass of the active core layer; in step (d), the particle diameter is 5-10 mm, and the drying time is 8-14 hours.

5. Use of the material according to any one of claims 1 to 3 in remediating groundwater contaminated by petroleum hydrocarbons, characterized in that: The material is filled in a permeable reaction barrier (PRB) to treat polluted water containing coexisting ions such as Cl⁻ at pH 8.0-10.5 and temperature 5-30°C to achieve continuous oxidative degradation of organic pollutants.

6. The use according to claim 5, characterized in that Organic pollutants in polluted water bodies include petroleum hydrocarbons, benzene series, polycyclic aromatic hydrocarbons, etc.

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