Modified iron heterojunction biomass slow-release material, preparation method thereof and application of coupling electric field in remediation of groundwater organic pollutants

Abstract

This invention belongs to the field of functional catalytic materials and water treatment technology for groundwater pollution remediation, specifically relating to a modified iron heterojunction biomass slow-release material, its preparation method, and the application of a coupled electric field in the remediation of organic pollutants in groundwater. This invention utilizes shiitake mushroom biochar as a carrier to load modified zero-valent iron, effectively alleviating the problem of iron agglomeration. The modified zero-valent iron grows in situ within the three-dimensional pores of the biochar, enabling the slow release of active iron components and improving the utilization efficiency of the oxidant. The built-in electric field of the iron-carbon structure-reinforced material helps solve the problem of slow mass transfer in groundwater media, improving the surface accessibility of the oxidant and pollutants. This material can reduce the localized Fe... 2+ Excessive concentration of oxidant leads to ineffective consumption, but the electrons can be driven by an electric field to migrate in a specific direction, achieving spatiotemporal matching and dynamic control of the electron transfer rate and the iron supply rate, forming a closed-loop system for in-situ regeneration, which has good application prospects in groundwater remediation.

Description

Technical Field

[0001] This invention belongs to the field of functional catalytic materials and water treatment technology for groundwater pollution remediation, specifically relating to a modified iron heterojunction biomass slow-release material and its preparation method, as well as the application of coupled electric field in the remediation of organic pollutants in groundwater. Background Technology

[0002] Zero-valent iron (ZVI) is a preferred groundwater remediation material due to its abundant sources, low cost, and strong reducing power. However, during the preparation of ZVI using the liquid-phase reduction method, Fe... 0 After nucleation, the surface is easily oxidized to form a dense iron oxide layer, hindering the directional transfer of internal electrons, thus facing a trade-off between reactivity, selectivity, and stability. Furthermore, in traditional groundwater remediation processes, due to limited mass transfer in the groundwater environment, at low permeability coefficients (10⁻⁶), it is less effective. -4 ~10 -5 In formations with a surface energy of 1000 cm / s, the one-time addition of ZVI, which has high surface energy and magnetic properties, often results in excessive local contact between active iron and oxidants such as persulfate, causing rapid depletion of the active iron and making it difficult to form a continuous reaction zone, while also causing ineffective consumption of the oxidant.

[0003] In recent years, electric field-assisted remediation technology has shown significant advantages in low-permeability formations by enhancing mass transfer between pollutants and remediation agents through electroosmosis and electromigration. However, achieving precise remediation often requires high voltage, leading to severe electrode corrosion and hindering long-term operation. Therefore, a new system with low voltage and intelligent control is urgently needed. Regarding ZVI modification, biochar (BC) obtained from the pyrolysis of waste biomass is effective in alleviating nanoparticle aggregation and improving dispersibility and stability due to its porous structure, rich functional groups, and low cost. Furthermore, strategies such as controlling the doping of non-metallic p-block elements (such as N, P, and S) can significantly optimize the electronic structure of materials. In particular, the formation of "iron heterojunctions" to construct an internal electric field significantly promotes the stepwise transformation of iron from zero to divalent and then to trivalent valence, potentially achieving coupling with weak electric fields for efficient remediation of organic pollutants in groundwater. However, systematic research is still lacking in finding suitable pore structures, constructing stable slow-release biomass substrates, and preparing iron heterojunction biomass slow-release materials. In particular, existing technologies mostly focus on single surface modification strategies or lattice engineering, lacking research on the synergistic modification mechanism of lattice electronic structure and interface shell, as well as a systematic comparison of their electric field remediation efficacy for organic pollutants in groundwater.

[0004] Therefore, it is essential to develop a ZVI-based slow-release material that is suitable for low-permeability formations, highly efficient, stable, and green and economical, and to provide an integrated "material-device" solution with low energy consumption and low maintenance costs. Summary of the Invention

[0005] The technical problem to be solved by this invention is to overcome the shortcomings and deficiencies of existing modified zero-valent iron composite materials, which still have poor catalytic effects and need to be improved. The primary objective is to provide a modified iron heterojunction biomass slow-release material.

[0006] A second objective of this invention is to provide an electrode material.

[0007] A third objective of this invention is to provide an electrolytic cell.

[0008] A fourth objective of this invention is to provide the application of the modified iron heterojunction biomass slow-release material, the electrode material, or the electrolytic cell in the treatment of organic pollutants.

[0009] The fifth objective of this invention is to provide a wastewater treatment system.

[0010] The above-mentioned objective of this invention is achieved through the following technical solution:

[0011] This invention comprises a modified iron heterojunction biomass slow-release material, which is prepared by the following steps:

[0012] S1. Under a protective gas atmosphere, biochar and iron salt are thoroughly mixed in solvent conditions, and a mixed solution containing NaBH4 and phosphorus source is added to it. After the mixture is fully reacted, it is filtered, the solid part is washed and dispersed in water to obtain a suspension.

[0013] S2. Under a protective gas atmosphere, the sulfur source solution is added to the suspension obtained in step S1, the mixture is allowed to react fully, filtered, the solid portion is washed and dried to obtain the modified iron heterojunction biomass slow-release material.

[0014] The iron salts include ferric salts and / or ferrous salts;

[0015] The biochar was prepared from shiitake mushrooms as a biomass raw material;

[0016] The mass ratio of iron in the biochar and iron salt is (5~20):1.

[0017] The modified iron heterojunction biomass slow-release material prepared in this invention uses inexpensive or discarded shiitake mushroom biomass to prepare biochar as a dispersion carrier for ZVI, effectively solving the problem of ZVI agglomeration. Furthermore, shiitake mushroom biomass, due to its large specific surface area, can effectively promote the adsorption of organic pollutants and oxidants, improving reaction accessibility; simultaneously, its surface rich in electron-rich functional groups and persistent free radicals can act as a Fe... 3+ With F e2+ The electron library of the cyclic conversion further enhances the stability of the resulting modified iron heterostructure biomass slow-release material.

[0018] It is worth noting that oxidants such as persulfate can be activated to produce SO4. - Active free radicals. However, Fe released from ZVI 2+ With SO4 - Free radicals have extremely fast reaction rates, therefore excess Fe... 2+ Free radical quenching reduces the overall degradation efficiency of pollutants and leads to oxidant consumption. The ZVI prepared in this invention is grown in situ within the three-dimensional porous structure of biochar, which macroscopically facilitates the slow release of the core active iron component of ZVI, avoiding the Fe2+ degradation caused by excessive ZVI addition at one time. 2+ The active center effectively consumes the oxidant, improves the utilization rate of the oxidant for pollutant degradation, and enhances the recycling stability of the modified iron heterojunction biomass slow-release material.

[0019] Furthermore, the ZVI prepared by this invention based on an improved liquid-phase reduction method theoretically possesses a significant core-shell structure. The electronic structure is precisely modulated by introducing specific p-block heteroatoms in the two key steps of ZVI nucleation and shell formation, achieving synergistic surface sulfidation with lattice phosphating. Notably, phosphorus (P) and sulfur (S), two typical p-block elements, are preferred. Compared to existing nitrogen (N) doping, P can stably occupy metal sites, while N has lower solid solubility in the lattice; the formation of a loose FeS shell helps suppress Fe... 0 Excessive corrosion of ZVI enhances the strength of the built-in electric field by forming a heterostructure, thereby improving the selectivity of electron directional transfer. Specifically, P participates in the nucleation process of ZVI and participates in Fe in lattice form. 0 The interstitial lattice structures cause lattice expansion and increase the Fe-Fe bond length, further leading to stronger outward diffusion and accelerating electron transfer from Fe. 0 The release and transfer from the core to the shell; while S mainly forms a highly conductive sulfide shell on the surface, inhibiting the oxidation or dissociation of P species and Fe. 0 The faster corrosion and post-sulfidation etching approach help form a more porous FeS layer than traditional oxide layers, suppressing ineffective electron consumption and resulting in weaker inward diffusion. Therefore, the modified iron heterostructure biomass slow-release material prepared in this invention can significantly enhance electron diffusion from Fe... 0 The directional transfer of organic pollutants from the core to the shell, and then to the oxidant and pollutant, enables the rapid transformation of organic pollutants in groundwater.

[0020] This invention does not limit the source or type of shiitake mushrooms.

[0021] Furthermore, the shiitake mushrooms can be commercially available dried shiitake mushrooms (without additives) or waste shiitake mushroom residue.

[0022] Furthermore, the mass ratio of iron in the biochar and iron salt is (5~15):1, more preferably (12~15):1, and even more preferably (14~15):1.

[0023] Furthermore, the molar ratio of phosphorus in the phosphorus source to iron in the iron salt is (0.03~0.08):1, more preferably (0.04~0.06):1, and most preferably 0.05:1.

[0024] Furthermore, the molar ratio of sulfur in the sulfur source to phosphorus in the phosphorus source is (0.01~0.05):1, more preferably (0.03~0.04):1, and most preferably 0.03:1.

[0025] Furthermore, the biochar is prepared by the following steps: under a protective gas atmosphere, biomass powder is fully pyrolyzed at 400~600 °C, followed by post-treatment to obtain biochar.

[0026] Preferably, the temperature for complete pyrolysis is 450~550 ℃, more preferably 480~520 ℃.

[0027] Preferably, the time for complete pyrolysis is 1 to 3 hours, more preferably 1.5 to 2.5 hours.

[0028] Preferably, the heating rate for complete pyrolysis is 3~8 °C, more preferably 4~6 °C.

[0029] Furthermore, the post-processing includes cooling, grinding, and sieving.

[0030] Furthermore, the mesh size of the sieve is 150-250 mesh, preferably 180-220 mesh.

[0031] Furthermore, the biomass powder is obtained through pretreatment.

[0032] Furthermore, the pretreatment includes washing (to remove impurities), drying, and grinding, specifically including the following steps: washing the biomass raw material several times (generally 3 to 5 times), drying it, and grinding it into powder to obtain biomass powder.

[0033] Furthermore, the preparation of the modified iron heterojunction biomass slow-release material includes one or more of (1) to (4):

[0034] (1) The iron salt includes at least one of ferric chloride or its hydrate, ferrous sulfate or its hydrate, and ferric nitrate or its hydrate;

[0035] (2) The sulfur source includes at least one of Na2S2O4 and Na2S;

[0036] (3) The phosphorus source includes at least one of KH2PO4, K2HPO4, and Na2HPO4;

[0037] (4) The solvent is an aqueous solution of ethanol.

[0038] As an optional implementation, the water in the ethanol-water solution is deoxygenated water.

[0039] Preferably, the volume ratio of water to ethanol in the ethanol-water solution is (6~8):3, more preferably (6.5~7.5):3, and most preferably 7:3.

[0040] Further, in step S1, when the iron salt is a ferrous salt (Fe2+), the molar ratio of NaBH4 to iron in the iron salt is ≥2:1; when the iron salt is a ferric salt (Fe3+), the molar ratio of NaBH4 to iron in the iron salt is ≥3:1. When the iron salt is a ferrous salt, the theoretical molar ratio of NaBH4 reducing agent to iron in the iron salt is 2:1 (or 3:1 if it is a ferric salt). To ensure that the iron salt is reduced as completely as possible, the actual amount of reducing agent added will be slightly greater than the theoretical molar ratio.

[0041] Furthermore, as an optional implementation, when the iron salt is a divalent iron salt, the molar ratio of the NaBH4 reducing agent to the iron element in the iron salt is (2.05~2.2):1, preferably (2.1~2.2):1.

[0042] Furthermore, in step S1, the solvent for the mixed solution containing NaBH4 and the phosphorus source is water.

[0043] Furthermore, in step S1, the mixed solution containing NaBH4 and a phosphorus source is added dropwise.

[0044] Furthermore, in step S1, the method of achieving thorough mixing is stirring.

[0045] Furthermore, the stirring time is 15-45 min, more preferably 25-35 min.

[0046] Further, in step S1, the washing involves alternating between water and ethanol for 2 to 5 times (preferably 3 to 4 times).

[0047] Preferably, in step S1, the time for the full reaction is 0.5 to 2 hours, more preferably 0.8 to 1.5 hours.

[0048] Preferably, in step S2, the complete reaction is performed by ultrasonic treatment under sealed conditions.

[0049] Furthermore, the ultrasonic treatment conditions have a power of 100~120 W and a frequency of 30~50 kHz.

[0050] Preferably, the ultrasonic treatment conditions have a power of 105~115 W and a frequency of 35~45 kHz.

[0051] Furthermore, in step S2, the time for the full reaction is 0.5 to 2 hours, more preferably 0.8 to 1.5 hours.

[0052] Furthermore, in step S2, the drying is vacuum freeze drying.

[0053] Furthermore, the protective gas is selected from at least one of nitrogen, argon, neon, and helium.

[0054] This invention protects an electrode material comprising a substrate and a modification layer attached to the surface of the substrate, wherein the modification layer contains the modified iron heterojunction biomass slow-release material.

[0055] Furthermore, as an optional implementation, the substrate is selected from carbon felt.

[0056] This invention protects an electrolytic cell, comprising an anode, a cathode, and an electrolyte, wherein the cathode is the electrode material.

[0057] This invention protects the application of the modified iron heterojunction biomass slow-release material, the electrode material, or the electrolytic cell in the treatment of organic pollutants.

[0058] Furthermore, as an optional implementation, the organic pollutant is an organic pollutant in groundwater.

[0059] Furthermore, the modified iron heterojunction biomass slow-release material can treat organic pollutants under both no-electric-field and applied-electric-field conditions. Under applied-electric-field conditions, it exhibits better pollutant treatment capabilities.

[0060] Furthermore, the voltage range of the applied electric field is -0.1 to -1 V, preferably -0.5 to -0.7 V.

[0061] Furthermore, the organic pollutant is at least one of chlorinated hydrocarbons, phenols, and petroleum hydrocarbons.

[0062] Furthermore, the chlorinated hydrocarbons include trichloroethylene.

[0063] Furthermore, the phenols include phenol.

[0064] Furthermore, the treatment of organic pollutants also requires the addition of an oxidant.

[0065] Preferably, the oxidant comprises persulfate.

[0066] Furthermore, the persulfate includes permonosulfate.

[0067] Furthermore, the persulfate includes potassium persulfate.

[0068] Furthermore, the initial concentration of the oxidant in the reaction system is ≥0.01 mM.

[0069] Furthermore, the initial concentration of the oxidant in the reaction system is ≥0.5 mM.

[0070] Preferably, the initial concentration of the oxidant in the reaction system is 0.1~5 mM, more preferably 0.5~2 mM.

[0071] This invention also protects a wastewater treatment system, including a power supply unit and a treatment unit disposed on a wastewater flow channel;

[0072] The processing unit includes at least one set of electrode pairs arranged in series along the water flow direction and a packing module filled between the electrode pairs;

[0073] The electrode pair includes anodes and cathodes arranged in parallel, the anodes and cathodes being arranged perpendicular to the water flow direction and having a gap between them;

[0074] The filler module includes at least one filler layer, which is formed by filling with at least one of the modified iron heterojunction biomass slow-release materials;

[0075] The power supply unit is electrically connected to the electrode pair and is configured to provide electrical energy to the electrode pair.

[0076] Furthermore, the power supply unit adopts a pulse power supply system.

[0077] Furthermore, the wastewater treatment system also includes a control unit.

[0078] Furthermore, the control unit includes:

[0079] A first controller, connected to the power supply unit, is used to control the magnitude and direction of the voltage applied to the electrode pair;

[0080] A sensing probe is installed on the outlet side of the packing module to detect the oxidation-reduction potential or pH value in the outlet water.

[0081] The second controller is connected to the sensor probe and configured to adjust the amount of oxidant added to the packing module in real time according to the data detected by the sensor probe and a preset algorithm.

[0082] Preferably, the oxidant comprises persulfate.

[0083] Furthermore, the persulfate includes permonosulfate.

[0084] Furthermore, the persulfate includes potassium persulfate.

[0085] Furthermore, the sensing probe includes a redox potential probe or a pH probe.

[0086] Compared with the prior art, the present invention has the following beneficial effects:

[0087] (1) The core difference between the modified iron heterostructure biomass slow-release material provided by the present invention, which is phosphated first and then sulfidated, and the previously reported one-step co-doping of non-metallic p-block elements (i.e., without distinguishing the doping order), lies in the fact that, firstly, the lattice P element successfully participates in the nucleation process of ZVI and grows in situ in the three-dimensional porous structure of biomass. The strain in the iron core causes lattice expansion to accelerate the release and transfer of electrons from the iron core to the shell. Subsequently, sulfidation mainly forms a thin and highly conductive FeS shell on the surface as a bridge for electron transfer, allowing electrons to quickly penetrate the shell and be released outward. This approach achieves continuous activation of the oxidant from three angles: firstly, by reducing ZVI agglomeration and achieving macroscopic slow release through specific biochar loading; secondly, by increasing the number of available electrons in ZVI through lattice doping; and finally, by enhancing the directional transfer of available electrons through surface modification. The three work synergistically, thus compensating for the trade-off between "reactivity-selectivity-stability" in conventional synchronous doping modification of ZVI.

[0088] (2) This invention uses shiitake mushrooms as biomass raw materials. After simple pyrolysis pretreatment, a slow-release carrier of ZVI is obtained. The operation is simple and the cost is low. Compared with traditional biomass such as straw and water hyacinth leaves, shiitake mushrooms have better pollutant degradation effect and excellent cycle stability due to their more suitable surface functional groups and pore structure.

[0089] (3) The modified iron heterojunction biomass slow-release material provided by this invention has advanced technology for the remediation of organic pollution in groundwater. The formation of iron heterojunctions in this modified iron heterojunction biomass slow-release material can significantly enhance the built-in electric field of the material itself, providing the possibility for the introduction of weak electric fields, which is expected to solve the problem of slow mass transfer of oxidants and pollutants in groundwater media and improve their accessibility on the surface of the filler; based on the excellent iron slow-release properties of this modified iron heterojunction biomass slow-release material, it can significantly reduce the local Fe 2+The ineffective consumption of oxidant caused by excessive concentration can be further driven by the applied electric field to drive the directional movement of electrons released from the ZVI core-shell. Its overall advantage lies in making the "electron transfer rate" and "iron supply rate" a closed-loop system that is spatiotemporally matched, dynamically adjustable, and regenerated in situ, thereby improving the utilization efficiency of the oxidant. Attached Figure Description

[0090] Figure 1 The images shown are SEM images of the final materials obtained in Comparative Example 1 and Example 3, where (a) is the SEM image of the final material obtained in Comparative Example 1, (b) is the SEM image of the final material obtained in Example 3, and (c) is a partial enlarged view of (b).

[0091] Figure 2 The X-ray diffraction (XRD) patterns (20~70°) of the final materials obtained in Comparative Examples 1, 4, 5 and 3 are shown.

[0092] Figure 3 The images show partial XRD patterns (40-50°) of the final materials obtained from Comparative Examples 1, 4, 5 and 3.

[0093] Figure 4 The images show the Raman spectra of the final materials obtained in Comparative Examples 1, 5, and 3.

[0094] Figure 5 The graphs show the degradation effect of the final materials obtained in Example 3 and Comparative Examples 1 to 3 on trichloroethylene after the first use (1st) and two cycles of use (2nd, 3rd).

[0095] Figure 6 The graph shows the effect of the final material obtained in Example 3 on the removal of phenol under different applied power supply voltages.

[0096] Figure 7 This is a schematic diagram of the wastewater treatment system using intelligent electric field coupling modified iron heterojunction shiitake mushroom-based biomass slow-release material in Test Example 5. Detailed Implementation

[0097] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in this technical field.

[0098] Unless otherwise specified, all reagents and materials used in the following examples are commercially available.

[0099] These are shiitake mushroom fragments, made without any additives. They are dried shiitake mushrooms (or simply dried shiitake mushrooms), sourced from Taobao and the original GuGu Food Store.

[0100] Water hyacinth leaves sourced from Taobao and the Guangdong Provincial Nursery, Turf and Aquatic Plant Base.

[0101] Sources of corn stalks: Taobao, rural specialty industry bases.

[0102] Example 1: Modified iron-based heterojunction shiitake mushroom-based biomass slow-release material P / S post -1-ZVI@BC-15

[0103] (1) Wash the shiitake mushroom fragments 4 times, dry and grind them into powder, fill them into a boat and place them in a tube furnace. Under nitrogen (N2) protection, set the heating rate to 5 ℃ / min and heat to 500 ℃, maintain for 2.0 h, collect the product after natural cooling, grind and sieve (200 mesh) to obtain biochar (BC).

[0104] (2) Under N2 environment, 0.0108 mol FeSO4·7H2O and 9.0 g BC were dissolved in 100 mL of a mixed solution of deoxygenated water and ethanol (volume ratio of deoxygenated water and ethanol was 7:3), stirred for 30 min, and then 100 mL of a mixed aqueous solution containing NaBH4 (0.0227 mol) and KH2PO4 (keeping P / Fe=5%) was added dropwise and reacted fully for 1.0 h. After filtration, the obtained solid material was washed three times alternately with deoxygenated water and anhydrous ethanol and then filtered. The solid was dispersed in 150 mL of water to obtain a suspension.

[0105] (3) Under N2 environment, 50 mL of aqueous solution containing Na2S (keeping S / P=1%) was added to the suspension obtained in step (2), sealed and ultrasonically treated (110 W, 40 kHz) for 1.0 h, filtered, and the obtained solid material was washed three times alternately with deoxygenated water and anhydrous ethanol and then freeze-dried overnight under vacuum to obtain modified iron heterostructured shiitake mushroom-based biomass slow-release material P / S post -1-ZVI@BC-15.

[0106] In step (2) above, the mass ratio of BC and Fe (i.e., BC / Fe) is 15:1, and the molar ratio of P and Fe (i.e., P / Fe) is 0.05:1 (i.e. 5%). In step (3), the molar ratio of S in the added Na2S and P in KH2PO4 in step (2) (i.e., S / P) is 0.01:1 (i.e. 1%).

[0107] Example 2 Modified iron-based heterogeneous shiitake mushroom-based biomass slow-release material P / S post -2-ZVI@BC-15

[0108] The difference between this embodiment and embodiment 1 is that the concentration of the Na2S solution added in step (3) is kept at S / P=2% with that of the KH2PO4 solution in step (2). That is, the molar ratio (i.e. S / P) of the S element in the added Na2S and the P element in the KH2PO4 in step (2) is 0.02:1 (i.e. 2%).

[0109] The other steps and conditions are the same as in Example 1.

[0110] Example 3 Modified iron-based heterojunction shiitake mushroom-based biomass slow-release material P / S post -3-ZVI@BC-15

[0111] The difference between this embodiment and embodiment 1 is that the concentration of the Na2S solution added in step (3) is kept at S / P=3% with that of the KH2PO4 solution in step (2). That is, the molar ratio (i.e. S / P) of the S element in the added Na2S and the P element in the KH2PO4 in step (2) is 0.03:1 (i.e. 3%).

[0112] The other steps and conditions are the same as in Example 1.

[0113] Example 4 Modified iron-based heterojunction shiitake mushroom-based biomass slow-release material P / S post -4-ZVI@BC-15

[0114] The difference between this embodiment and embodiment 1 is that the concentration of the Na2S solution added in step (3) is kept at S / P=4% with that of the KH2PO4 solution in step (2). That is, the molar ratio (i.e. S / P) of the S element in the added Na2S and the P element in the KH2PO4 in step (2) is 0.04:1 (i.e. 4%).

[0115] The other steps and conditions are the same as in Example 1.

[0116] Example 5 Modified iron-based heterogeneous shiitake mushroom-based biomass slow-release material P / S post -5-ZVI@BC-15

[0117] The difference between this embodiment and embodiment 1 is that the concentration of the Na2S solution added in step (3) is kept at S / P=5% with that of the KH2PO4 solution in step (2). That is, the molar ratio (i.e. S / P) of the S element in the added Na2S and the P element in the KH2PO4 in step (2) is 0.05:1 (i.e. 5%).

[0118] The other steps and conditions are the same as in Example 1.

[0119] Example 6 Modified iron-based heterojunction shiitake mushroom-based slow-release material P / S post -3-ZVI@BC-5

[0120] The difference between this embodiment and embodiment 3 is that the mass of BC in step (2) is 3.0 g, that is, the mass ratio of BC to Fe element (i.e. BC / Fe) in step (2) is 5:1.

[0121] The other steps and conditions are the same as in Example 3.

[0122] Example 7 Modified iron-based heterojunction shiitake mushroom-based slow-release material P / S post -3-ZVI@BC-25

[0123] The difference between this embodiment and embodiment 3 is that the mass of BC in step (2) is 15.0 g, that is, the mass ratio of BC to Fe (i.e. BC / Fe) in step (2) is 25:1.

[0124] The other steps and conditions are the same as in Example 3.

[0125] Comparative Example 1: Zero-valent iron material ZVI

[0126] The difference between this comparative example and Example 3 is that BC, KH2PO4 and Na2S are not added, thus obtaining the unmodified zero-valent iron material ZVI.

[0127] The specific preparation of zero-valent iron (ZVI) material includes the following steps:

[0128] 0.0108 mol FeSO4·7H2O was dissolved in 100 mL of a mixed solution of deoxygenated water and ethanol (volume ratio of deoxygenated water to ethanol was 7:3), and stirred for 30 min. Then, 100 mL of an aqueous solution containing 0.0227 mol NaBH4 was added dropwise and the mixture was allowed to react completely for 1.0 h. After filtration, the obtained solid material was washed three times alternately with deoxygenated water and anhydrous ethanol and then freeze-dried under vacuum overnight to obtain zero-valent iron material ZVI.

[0129] Comparative Example 2: Modified zero-valent iron material P / S post -ZVI

[0130] The difference between this comparative example and Example 3 is that BC is not added.

[0131] The other steps and conditions are the same as in Example 3.

[0132] Comparative Example 3: Modified zero-valent iron material P / S-ZVI@BC

[0133] The difference between this comparative example and Example 3 is that step (3) is incorporated into step (2), that is, Na2S, NaBH4 and KH2PO4 solutions are mixed together to obtain modified zero-valent iron material P / S-ZVI@BC without distinguishing the order.

[0134] The specific preparation of the modified zero-valent iron material P / S-ZVI@BC includes the following steps:

[0135] (1) Wash the shiitake mushroom fragments 4 times, dry and grind them into powder, fill them into a boat and place them in a tube furnace. Under nitrogen protection, set the heating rate to 5 ℃ / min and heat to 500 ℃, maintain for 2.0 h, collect the product after natural cooling, grind and sieve (200 mesh) to obtain BC;

[0136] (2) Dissolve 0.0108 mol FeSO4·7H2O and 9.0 g BC in a mixed solution of 100 mL deoxygenated water and ethanol (volume ratio of deoxygenated water and ethanol is 7:3), stir for 30 min, then add 100 mL of a mixed aqueous solution containing NaBH4 (0.0227 mol) and KH2PO4, Na2S (keeping P / Fe=5%, S / P=3%) dropwise and react fully for 1.0 h. The resulting solid material is washed three times alternately with deoxygenated water and anhydrous ethanol and then freeze-dried overnight under vacuum to obtain the modified zero-valent iron material P / S-ZVI@BC.

[0137] Comparative Example 4: Modified zero-valent iron material S post -ZVI@BC

[0138] The difference between this comparative example and Example 3 is that KH2PO4 is not added in step (2).

[0139] Modified zero-valent iron material S post The specific preparation of ZVI@BC includes the following steps:

[0140] (1) Wash the shiitake mushroom fragments 4 times, dry and grind them into powder, fill them into a boat and place them in a tube furnace. Under nitrogen protection, set the heating rate to 5 ℃ / min and heat to 500 ℃, maintain for 2.0 h, collect the product after natural cooling, grind and sieve (200 mesh) to obtain BC;

[0141] (2) Dissolve 0.0108 mol FeSO4·7H2O and 9.0 g BC in a mixed solution of 100 mL deoxygenated water and ethanol (volume ratio of deoxygenated water and ethanol is 7:3), stir for 30 min, then add 100 mL of aqueous solution containing 0.0227 mol NaBH4 dropwise and react for 1.0 h. Wash with deoxygenated water and anhydrous ethanol three times alternately, filter the solid obtained and disperse it in 150 mL of water to obtain a suspension.

[0142] (3) Under N2 environment, 50 mL containing Na2S (1.62 × 10⁻⁶) was added. -5A mol) aqueous solution was added to the suspension obtained in step (2), sealed, and ultrasonically treated (110 W, 40 kHz) for 1.0 h. After filtration, the obtained solid material was washed three times alternately with deoxygenated water and anhydrous ethanol, and then freeze-dried under vacuum overnight to obtain the modified zero-valent iron material S. post -ZVI@BC.

[0143] Comparative Example 5: Modified zero-valent iron material P-ZVI@BC

[0144] The difference between this comparative example and Example 3 is that step (3) is omitted.

[0145] The specific preparation of the modified zero-valent iron material P-ZVI@BC includes the following steps:

[0146] (1) Wash the shiitake mushroom fragments 4 times, dry and grind them into powder, fill them into a boat and place them in a tube furnace. Under nitrogen protection, set the heating rate to 5 ℃ / min and heat to 500 ℃, maintain for 2.0 h, collect the product after natural cooling, grind and sieve (200 mesh) to obtain BC;

[0147] (2) Dissolve 0.0108 mol FeSO4·7H2O and 9.0 g BC in a mixed solution of 100 mL deoxygenated water and ethanol (volume ratio of deoxygenated water and ethanol is 7:3), stir for 30 min, then add 100 mL of a mixed aqueous solution containing NaBH4 (0.0227 mol) and KH2PO4 (keeping P / Fe=5%) dropwise and react fully for 1.0 h, filter, wash the obtained solid material with deoxygenated water and anhydrous ethanol alternately 3 times, and freeze-dry under vacuum overnight to obtain modified zero-valent iron material P-ZVI@BC.

[0148] Comparative Example 6: Modified Iron Heterojunction Corn Stalk-Based Biomass Slow-Release Material

[0149] The difference between this comparative example and Example 3 is that the shiitake mushroom fragments in step (1) are replaced with corn stalks.

[0150] The other steps and conditions are the same as in Example 3.

[0151] Comparative Example 7: Modified Iron-Iron Heterogeneous Water-Gel-Based Cycas revoluta Leaf-Based Biomass Slow-Release Material

[0152] The difference between this comparative example and Example 3 is that the shiitake mushroom fragments in step (1) are replaced with water hyacinth leaves.

[0153] The other steps and conditions are the same as in Example 3.

[0154] Test Example 1

[0155] Experimental materials: Comparative Examples 1, 4, and 5, and the final materials prepared in Example 3.

[0156] Scanning electron microscopy was performed on the final materials obtained in Comparative Example 1 and Example 3, and the results are as follows: Figure 1 As shown, the ZVI prepared by liquid-phase reduction in Comparative Example 1 exhibits distinct spherical particles. These spherical particles are highly aggregated, presenting as non-dispersed chains or blocks. Figure 1 (Figure (a) in the text), while the P / S prepared in Example 3 post -3-ZVI@BC-15 exhibits a loose, porous, three-dimensional flower-like spatial structure. Figure 1 As shown in Figures (b) to (c), thanks to the pleated carrier effect of shiitake mushroom biomass, ZVI can achieve extremely small particle loading during liquid-phase reduction and nucleation, which is beneficial for the ultra-high dispersion and exposure of active sites, and further enables precise modulation of the ZVI shell structure post-sulfurization. Compared with the zero-valent iron material ZVI in Comparative Example 1, the P / S ratio of Example 3 is significantly lower. post The significantly increased specific surface area of ​​-3-ZVI@BC-15 facilitates the adsorption of pollutants and oxidants, improving the accessibility of subsequent reactions.

[0157] The zero-valent iron material ZVI from Comparative Example 1 and the sulfurized S from Comparative Example 4 were used. post -ZVI@BC, five phosphated P-ZVI@BC comparative examples, and P / S pre-phosphated and then sulfurized P / S in Example 3 post XRD tests were performed on -3-ZVI@BC-15, and the results are as follows: Figures 2-3 As shown, all samples exhibit a distinct diffraction peak at 2θ ≈ 44.8°, corresponding to Fe. 0 (110) crystal plane ( Figure 2 No other diffraction peaks were found in the XRD pattern, proving that Fe... 0 The dominant phase is P, and P and S elements may be combined in a disordered manner. It is noteworthy that, compared to the zero-valent iron material ZVI in Comparative Example 1 and S in Comparative Example 4... post Compared to P-ZVI@BC in Comparative Example 5, P-ZVI@BC in Example 3 is comparable to P / S in Example 3. post -3-ZVI@BC-15 of Fe 0 The diffraction peaks show a significant shift to lower angles. Figure 3 This indicates that strong lattice expansion occurred in the ZVI, providing evidence for P-involved ZVI nucleation and S-involved surface shell processes.

[0158] Further Raman spectroscopy was performed on the final materials obtained from Comparative Example 1, Comparative Example 5, and Example 3, and the results are as follows: Figure 4 As shown. By Figure 4 It can be seen that in the range of 200~500cm -1Within the specified range, the zero-valent iron material in Comparative Example 1 did not show a significant characteristic peak for ZVI; the P-ZVI@BC material in Comparative Example 5 showed a peak at 225 cm⁻¹. -1 299cm -1 The presence of a weak α-Fe₂O₃ characteristic peak indicates that a weak oxidation occurs on the ZVI surface after lattice phosphorus doping; while the P / S ratio in Example 3... post -3-ZVI@BC-15 at 212cm -1 275cm -1 A distinct Fe-S bond characteristic peak was detected at the site, further demonstrating that post-sulfidation facilitates the deposition of FeS on the ZVI surface to form a heterostructure.

[0159] Test Example 2

[0160] Experimental materials: final materials prepared in Examples 1 to 7 and Comparative Examples 1 to 7.

[0161] Experimental Methods: The final materials obtained from Examples 1-7 and Comparative Examples 1-7 were added to 100 mL of 0.5 mM phenol solution at a dosage of 0.2 g / L. After pre-adsorption for 30 min, potassium persulfate (PMS) was added to initiate the reaction, bringing the initial concentration in the reaction system to 2.0 mM. The reaction system was then placed in a shaker and reacted at 300 rpm. The reactive oxygen species generated after PMS activation degraded the phenol, and the reaction time was 3 h. After the reaction, 1.0 mL of the reaction solution was filtered through a 0.22 μm filter and then added to 0.5 mL of methanol to terminate the reaction. The mixture was analyzed by high-performance liquid chromatography (HPLC), with the mobile phase being an aqueous methanol-water solution (methanol to water volume ratio of 7:3). Phenol was determined using a UV detector at a wavelength of 275 nm. The degradation effect of different materials was evaluated by measuring the pollutant concentration before and after the reaction. The specific calculation formula is as follows: Removal rate (%) = ( C 0- C t ) / C0×100%; where, C 0: Initial concentration of pollutants (concentration at t=0 before the reaction begins). C t : The concentration of the pollutant at time t; the closer the value is to 100%, the better the degradation effect of the material on the pollutant. The removal rate of pollutants in other test examples is calculated in the same way.

[0162] Table 1. Removal rate of phenol by different materials

[0163]

[0164] Experimental Results: The removal rates of phenol by different materials obtained under the above experimental conditions are shown in Table 1. It can be seen that the modified iron-based heterojunction shiitake mushroom-based slow-release materials prepared in Examples 1-6 of this invention have significantly higher phenol removal rates than the final materials of Comparative Examples 1-5. This further proves the feasibility of the proposed approach, as detailed below:

[0165] The difference between Examples 1 to 5 lies in the different S / P ratios in the phosphating and sulfidation steps. As the S / P ratio increases from 1% to 5%, the degradation effect of phenol shows a volcanic distribution trend. When S / P = 3%, the modified iron heterostructured shiitake mushroom-based biomass slow-release material has the best degradation effect.

[0166] Example 3 was compared with Comparative Examples 3-5 to clearly distinguish the roles of lattice phosphating and surface sulfidation. Compared with the zero-valent iron material ZVI in Comparative Example 1, the lattice modulation (P element doping) of the ZVI core-shell structure in Comparative Example 5 and the surface modulation (S element doping) in Comparative Example 4 both contributed to improving the reactivity of ZVI, but the improvement effect was limited. Compared with the P / S-ZVI@BC obtained by the one-pot reaction in Comparative Example 3, the P / S obtained in Example 3... post The removal rate of -3-ZVI@BC-15 was close to 100%, indicating that pre-phosphating controlled the Fe... 0 The idea of ​​regulating shell composition through sulfidation after nucleus growth has led to an increase in electron transfer rate and selectivity, which has a significant effect on the degradation of organic pollutants by activated PMS.

[0167] Example 3 was compared with Comparative Examples 6 and 7 to compare the effects of common biomass as a slow-release substrate. Comparative Example 6 used common corn stalks as the biomass raw material, and the modified zero-valent iron material obtained using this biomass as a substrate achieved a phenol removal rate of 90%. Comparative Example 7 used widely available water hyacinth leaves as the biomass raw material, which can generate a large amount of volatiles during pyrolysis to form biochar with a predominantly mesoporous structure, making it a good ZVI growth substrate. However, its lignin content is relatively low, resulting in a low char yield. Furthermore, its low ash content and high oxygen content lead to a low calorific value, usually requiring doping or modification to obtain a carbon substrate with high conductivity. Therefore, the modified zero-valent iron material obtained using this biomass as a raw material achieved a phenol removal rate of 87%, with limited degradation effect. In contrast, the shiitake mushroom biochar selected in this invention can serve as an excellent dispersion carrier and slow-release substrate for subsequent ZVI growth, helping to form an Fe-C interface with a built-in electric field and improving the material's pollutant removal rate. Compared with the final materials obtained in Comparative Examples 6-7, the P / S ratio of Example 3 was significantly lower. post -4-ZVI@BC-15 showed significantly better phenol removal rates than corn stalks (Comparative Example 6) and water hyacinth leaves (Comparative Example 7) in the tests.

[0168] Test Example 3

[0169] Catalytic material: The final material prepared in Example 3 and Comparative Examples 1-3.

[0170] Experimental Method: The final materials obtained in Example 3 and Comparative Examples 1-3 were added at a dosage of 1.0 g / L to multiple headspace vials containing 10 ppm trichloroethylene (TCE). Potassium persulfate (PMS) was then added to the system to a final concentration of 1.0 mM to initiate the reaction. The headspace vials were placed in a shaker at 200 rpm for 4 hours, and the residual concentration of TCE was determined by gas chromatography at preset time points. The relative concentration of the pollutants (TCE) was then analyzed. C t The degradation effect was evaluated by the change in CO), where, C 0: Initial concentration of pollutants (concentration at t=0 before the reaction begins). C t : The concentration of pollutants at time t.

[0171] After the reaction was completed, the above-mentioned catalytic materials were recovered by filtration and drying, and the cycle reaction was restarted to determine the stability and application potential of the above-mentioned catalytic materials in the actual remediation process. The number of cycles in this test case was 3.

[0172] Experimental results: The results are as follows Figure 5 As shown, the P / S prepared in Example 3 of this application post -3-ZVI@BC-15 exhibits good activity in degrading TCE; the catalytic activity only slightly decreased during the three cycles, indicating that this modified iron-heteromorphic shiitake mushroom-based biomass slow-release material can achieve the slow release of active iron components, avoiding the one-time or rapid depletion of active iron, thus endowing the material with excellent recyclability; the removal rate of the final material obtained in Comparative Example 1 in the second cycle (removal rate = 1- C t The removal rate of ZVI (Zygote-Vitamin C0) was only 30%, attributed to the blockage of active centers and loss of electron transfer selectivity due to shell passivation. The final materials obtained in Comparative Examples 2 and 3 showed decreased removal rates in the second and third cycles, presumably due to material agglomeration caused by the lack of BC loading in Comparative Example 2, and a trade-off between reactivity, selectivity, and stability caused by the inaccurate construction of the core-shell structure in Comparative Example 3. This further verifies the importance of the core concept proposed in this invention. The above results demonstrate that the modified iron heterostructured shiitake mushroom-based biomass slow-release material of this invention, prepared by phosphating followed by sulfidation, exhibits high stability in the degradation of organic pollutants in groundwater, representing a significant technological advancement.

[0173] Test Example 4

[0174] This test case provides an application example of slow-release materials coupled with electrochemical remediation of typical organic pollutants in groundwater.

[0175] Experimental materials: The final materials prepared in Example 3.

[0176] Experimental method: Preparation of carbon felt-supported P / S obtained in Example 3 post The -3-ZVI@BC-15 electrode sheet was used as the working electrode. A platinum sheet electrode was used as the counter electrode, and Ag / AgCl was used as the reference electrode to form a three-electrode system for pollutant degradation testing. The working electrode had a surface area of ​​1 cm². 2 The electrode spacing was approximately 1 cm, and the reaction system consisted of 50 mL of electrolyte. 0.5 M Na₂SO₄ was used as the electrolyte to maintain solution conductivity. Before the experiment, the target pollutants phenol and PMS were added to the electrolyte at a concentration of 0.5 mM each, without additional pH adjustment. After 3 hours of reaction, the residual phenol concentration was determined using high-performance liquid chromatography (HPLC), and the phenol removal rate was obtained using the calculation method described in Test Example 2. To evaluate the coupled electrochemical remediation performance of the material, the experiment was conducted by applying different voltage gradients (-0.1 V, -0.3 V, -0.5 V, -0.7 V, and -1.0 V).

[0177] Experimental Results: Compared to Test Example 2, this test example further emphasizes the effect of the electric field by reducing the concentration of PMS. The results are as follows: Figure 6 As shown, when a power supply voltage of -0.1 V was applied, the phenol removal rate was 82%. Further increasing the initial voltage to -0.3 V resulted in a removal rate of 94%, confirming that a weak electric field can drive and accelerate the directional migration of electrons from the slow-release material to the PMS, reducing Fe. 0 Excessive corrosion and free radical quenching enhance the degradation of pollutants. In this test example, complete removal of phenol was achieved at -0.5 V, representing the optimal efficiency equilibrium point. Increasing the voltage to -1.0 V resulted in a decrease in removal rate, due to the intensified hydrogen evolution side reaction, which competes for electrons with the PMS activation reaction, leading to reduced current efficiency. These results indicate that the introduction of an electric field can significantly reduce the PMS dosage (compared to Test Example 2), achieving efficient mass transfer and directional electron migration within a suitable low voltage range. In particular, the release rate of Fe by the slow-release material effectively matches the mass transfer rate controlled by the electric field, greatly improving the utilization rate of PMS and demonstrating excellent pollutant degradation performance.

[0178] Test Example 5

[0179] This test case provides a method for testing low permeability coefficients (typically around 10). -4 ~10 -5The wastewater treatment system based on the modified iron heterostructured shiitake mushroom-based biomass slow-release material obtained in Examples 1-6 of the intelligent electric field coupling of groundwater (cm / s). Figure 7 As shown, the wastewater treatment system embeds a pollutant plume along the water flow direction and mainly consists of a cathode, anode, a packing module, a controller, a sensor probe, and a pulse power supply system as the power supply unit. The electrodes are arranged parallel to the water flow direction, with no contact between the anode and cathode and a gap between them; the anode is an iridium-plated titanium mesh (Ti / IrO2 mesh), and the cathode is a flexible graphite felt. Any one or more of the modified iron heterojunction mushroom-based biomass slow-release materials obtained in Examples 1-6 are used as the filling medium to fill and form a packing layer that forms a permeable reactive wall; several layers of the packing layer are arranged in series between the cathode and anode to obtain the packing module. The pulse power supply system uses a solar panel or a small battery. The first controller controls the magnitude and direction of the applied voltage. An oxidation-reduction potential (ORP) probe or pH probe is installed at the outlet of the packing module to detect effluent indicators and feed the signal back to the second controller. The controller reads data in real time according to a preset algorithm and adjusts the dosage of oxidant (such as PMS) in the packing module. The system operates for 12 hours. In stage 1, after polluted water flows into the wastewater treatment system, the first controller applies voltage. Under the influence of the electric field, the migration rate of pollutants increases significantly, and they are quickly adsorbed into the packing module to form a reaction zone. At this time, a quantitative oxidant is added into the packing module. Under the influence of the electric field, it migrates towards the anode to the surface of the packing layer in the packing module. The active iron in the packing layer is slowly released and migrates against the PMS within the packing layer, thereby activating the PMS to generate active oxygen species, achieving efficient degradation of pollutants. At the same time, coexisting anions and cations in the water migrate towards the anode and cathode respectively under the influence of the electric field and leave the reaction zone, greatly reducing their competition for reaction with active species. In stage 2, an ORP probe or pH probe is used to detect the effluent after the packing module has been repaired at 1-hour intervals to determine the current free radical activity and Fe in the packing module. 2+ Whether the concentration is suitable is determined by setting high or low ORP or pH ranges based on experience. For example, an ORP range of 150-350 mV or a pH range of 6.0-8.2 can be set as a safe zone. Otherwise, the oxidant addition is adjusted through the second controller. In stage 3, after the operating cycle ends, the reverse pulse is switched through the first controller to remove Fe from the packing area. 3+ Reduced to Fe 2+ This process renews the active sites of the modified iron-rich heterostructured shiitake mushroom-based slow-release material in the packing module. The wastewater treatment system should periodically update the packing module during operation to reduce the weakening of the remediation effect caused by the consumption of active sites.

[0180] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A modified iron heterojunction biomass slow-release material, characterized in that, The preparation process includes the following steps: S1. Under a protective gas atmosphere, biochar and iron salt are thoroughly mixed in solvent conditions, and a mixed solution containing NaBH4 and phosphorus source is added to it. After the mixture is fully reacted, it is filtered, the solid part is washed and dispersed in water to obtain a suspension. S2. Under a protective gas atmosphere, the sulfur source solution is added to the suspension obtained in step S1, the reaction is complete, the mixture is filtered, the solid part is washed and dried to obtain the modified iron heterojunction biomass slow-release material. The iron salts include ferric salts and / or ferrous salts; The biochar was prepared from shiitake mushrooms as a biomass raw material; The mass ratio of iron in the biochar and iron salt is (5~20):1; The molar ratio of phosphorus in the phosphorus source to iron in the iron salt is (0.03~0.08):1; The molar ratio of sulfur in the sulfur source to phosphorus in the phosphorus source is (0.01~0.05):

1.

2. The modified iron heterojunction biomass slow-release material according to claim 1, characterized in that, The biochar is prepared by the following steps: under a protective gas atmosphere, biomass powder is fully pyrolyzed at 400~600 °C, followed by post-treatment to obtain biochar.

3. The modified iron heterojunction biomass slow-release material according to claim 1, characterized in that, The preparation of the modified iron heterojunction biomass slow-release material includes one or more of (1) to (4): (1) The iron salt includes at least one of ferric chloride or its hydrate, ferrous sulfate or its hydrate, and ferric nitrate or its hydrate; (2) The sulfur source includes at least one of Na2S2O4 and Na2S; (3) The phosphorus source includes at least one of KH2PO4, K2HPO4, and Na2HPO4; (4) The solvent is an aqueous solution of ethanol.

4. An electrode material, characterized in that, It includes a substrate and a modification layer attached to the surface of the substrate, wherein the modification layer contains the modified iron heterojunction biomass slow-release material according to any one of claims 1 to 3.

5. An electrolytic cell, comprising an anode, a cathode, and an electrolyte, characterized in that, The cathode is the electrode material described in claim 4.

6. The application of the modified iron heterojunction biomass slow-release material according to any one of claims 1 to 3, the electrode material according to claim 4, or the electrolytic cell according to claim 5 in the treatment of organic pollutants.

7. The application according to claim 6, characterized in that, The organic pollutant is at least one of chlorinated hydrocarbons, phenols, and petroleum hydrocarbons.

8. A wastewater treatment system, characterized in that, Includes a power supply unit and a treatment unit installed on the wastewater flow channel; The processing unit includes at least one set of electrode pairs arranged in series along the water flow direction and a packing module filled between the electrode pairs; The electrode pair includes anodes and cathodes arranged in parallel, the anodes and cathodes being arranged perpendicular to the water flow direction and having a gap between them; The filler module includes at least one filler layer, which is formed by filling with at least one of the modified iron heterojunction biomass slow-release materials according to any one of claims 1 to 3; The power supply unit is electrically connected to the electrode pair.

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