Preparation method and application of zero-valent iron loaded phosphorus modified biochar

Abstract

This invention relates to the field of wastewater treatment technology, specifically providing a method for preparing and applying zero-valent iron-loaded phosphorus-modified biochar. The method includes pretreating biomass, impregnating biomass powder in an H3PO4 solution, and subjecting the impregnated mixture to oxygen-limited pyrolysis to obtain phosphorus-modified biochar. The phosphorus-modified biochar, soluble iron salt, and deionized water are mixed and subjected to oxygen-limited pyrolysis to obtain zero-valent iron-loaded phosphorus-modified biochar. The phosphorus-modified biochar possesses both excellent adsorption properties and microbial carrier functions, effectively inhibiting zero-valent iron aggregation and passivation, and enhancing the adsorption and chemical reduction effects of hexavalent chromium. This invention adds chromium-reducing bacteria and zero-valent iron-loaded phosphorus-modified biochar to polluted water and soil containing hexavalent chromium. Microbacterium YT1 enhances bioreduction, and the synergistic effect of both significantly improves the remediation efficiency and stability of Cr(VI)-contaminated wastewater and soil, overcoming the shortcomings of single remediation technologies.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to a method for preparing and applying zero-valent iron-supported phosphorus-modified biochar. Background Technology

[0002] Chromium (Cr) is an important raw material in industries such as leather making, electroplating, and pigments. Its large-scale application has led to increasingly prominent environmental Cr pollution problems. Among the various chemical forms of Cr, hexavalent chromium (Cr(VI)) is a highly toxic, easily migrating, and potent carcinogen, and its environmental remediation is a global challenge.

[0003] Traditional physicochemical remediation methods, such as chemical precipitation and ion exchange, while providing rapid results, are costly and prone to causing secondary pollution. More importantly, these methods typically only reduce Cr(VI) to trivalent chromium (Cr(III)), which is easily re-oxidized under changing environmental conditions, leading to pollution rebound and unsustainable remediation effects. Bioremediation, using chromium-reducing bacteria as its core, converts Cr(VI) into less toxic Cr(III), offering advantages such as environmental friendliness and low cost. However, it has significant drawbacks: bacterial growth is easily inhibited by environmental factors such as pH, salinity, and Cr(VI) concentration, resulting in a sharp drop in remediation efficiency under high pollution or extreme conditions; and the remediation cycle is relatively long.

[0004] To overcome the limitations of single remediation technologies, composite remediation technologies (especially bio-chemical composite remediation technologies) have become a research hotspot in the field of chromium pollution remediation. Biochar, as a porous carbonaceous material, possesses characteristics such as large specific surface area, strong adsorption capacity, and good chemical stability. Furthermore, phosphorus modification can further enhance its adsorption capacity and selectivity for heavy metal ions, while simultaneously providing a carrier for microbial growth and improving the survival environment of microorganisms in polluted media. Loading zero-valent iron onto the surface of phosphorus-modified biochar can inhibit the aggregation of zero-valent iron through the dispersing effect of biochar, prolonging its reaction activity cycle, and simultaneously achieving a synergistic adsorption-reduction effect, thereby improving the removal efficiency of Cr(VI).

[0005] Although existing research has attempted to combine biochar-based materials with chromium-reducing functional bacteria for chromium pollution remediation, current technologies still have several shortcomings: First, the compatibility between functional bacteria and biochar-based materials needs optimization, and there is a lack of specifically screened highly chromium-tolerant and broadly adaptable chromium-reducing strains, resulting in insufficient remediation stability of the composite system in complex pollution environments; second, the preparation process parameters of zero-valent iron-supported phosphorus-modified biochar have not yet been optimized, and there is still room for improvement in its Cr(VI) reduction efficiency and material stability; third, existing composite remediation technologies can mostly only reduce Cr(VI) to Cr(III), and have not yet achieved the conversion of Cr(VI) to elemental chromium (Cr... 0The deep transformation of chromium into elemental chromium not only completely eliminates the toxicity of chromium, but also enables the recycling of chromium resources, further enhancing the environmental and economic benefits of remediation technology; fourth, the lack of systematic optimization of remediation process parameters for different polluted media (water bodies, soil) leads to poor adaptability of the technology to practical applications.

[0006] Therefore, developing a synergistic remediation method that combines specific high-efficiency chromium-reducing bacteria with high-performance iron-based biochar materials has significant application value and prospects. Summary of the Invention

[0007] To overcome the problems existing in related technologies, the purpose of this invention is to provide a method for preparing and applying zero-valent iron-supported phosphorus-modified biochar. This method can overcome the technical defects of existing chromium pollution remediation technologies, such as low efficiency, poor stability, incomplete chromium conversion, and weak adaptability. It can efficiently and deeply remediate water bodies and soil contaminated with hexavalent chromium, and at the same time realize the conversion of hexavalent chromium to elemental chromium in water media remediation, thus having both environmental benefits and resource recovery value.

[0008] A method for preparing zero-valent iron-supported phosphorus-modified biochar includes: Biomass is pretreated to obtain biomass powder; The biomass powder was impregnated in an H3PO4 solution to obtain an impregnation mixture; The impregnation mixture was subjected to oxygen-limited pyrolysis at 300-500 °C to obtain phosphorus-modified biochar; The phosphorus-modified biochar, soluble iron salt, and deionized water were mixed at a mass-volume ratio of 1:2:100 to obtain a mixed solution. The mixture was post-treated by reducing pyrolysis at 500-700 °C under a nitrogen atmosphere, and after natural cooling, zero-valent iron-supported phosphorus-modified biochar was obtained.

[0009] In a preferred embodiment of the present invention, the pretreatment of biomass to obtain biomass powder includes: Wash the biomass repeatedly with deionized water three times. The cleaned biomass was dried in a 105℃ forced-air drying oven until constant weight. The dried biomass is crushed using a pulverizer; The crushed biomass is passed through a 60-mesh sieve to obtain biomass powder; the biomass is any one or any combination of tea leaves, straw and rice husks.

[0010] In a preferred embodiment of the present invention, the step of impregnating the biomass powder in an H3PO4 solution to obtain an impregnation mixture includes: The biomass powder and H3PO4 solution were mixed at a mass ratio of 4 to 1:1 to obtain the mixed biomass; the concentration of the H3PO4 solution was 1-3 mol / L. The mixed biomass was placed in a constant temperature shaking chamber and impregnated at room temperature for 24 h at a rotation speed of 150 r / min to obtain the impregnated mixture.

[0011] In a preferred embodiment of the present invention, the step of subjecting the impregnated mixture to oxygen-limited pyrolysis to obtain phosphorus-modified biochar comprises: The impregnation mixture was dried in a 105°C forced-air drying oven to constant weight, then transferred to a muffle furnace, sealed with aluminum foil, and heated to 300-500°C at a rate of 5-15°C / min. The mixture was then pyrolyzed at a constant temperature for 0.5-2 h, washed, dried, and ground through a 65-100 mesh sieve to obtain phosphorus-modified biochar.

[0012] In a preferred embodiment of the present invention, the step of mixing the phosphorus-modified biochar, soluble iron salt, and deionized water at a mass-to-volume ratio of 1:2:100 to obtain a mixed solution comprises: Mix 5 g of phosphorus-modified biochar, 10 g of soluble iron salt and 500 mL of deionized water and stir until homogeneous to obtain a mixture; the soluble iron salt is any one or any combination of ferric nitrate nonahydrate, ferrous sulfate heptahydrate and ferric chloride hexahydrate.

[0013] In a preferred embodiment of the present invention, the post-treatment of the mixture involves reduction pyrolysis at 500-700 °C under a nitrogen atmosphere, followed by natural cooling to obtain zero-valent iron-supported phosphorus-modified biochar, comprising: The mixture was placed in an oven and dried at 105 °C to obtain the precursor. After drying, the precursor was placed in a tube furnace and heated to 500-700 °C at a programmed heating rate of 5-15 °C / min under a nitrogen atmosphere. It was then pyrolyzed at a constant temperature for 0.5-2 h. After natural cooling, it was ground through a 65-100 mesh sieve to obtain zero-valent iron-supported phosphorus-modified biochar.

[0014] This invention also provides an application of zero-valent iron-loaded phosphorus-modified biochar in the remediation of hexavalent chromium-contaminated water. The zero-valent iron-loaded phosphorus-modified biochar prepared by the method described in any one of claims 1-6 is added to the polluted water containing hexavalent chromium, converting the hexavalent chromium in the polluted water into elemental chromium. The chromium-reducing bacteria is Microbacterium YT1, with accession number GDMCC NO.67734.

[0015] In a preferred embodiment of the present invention, before adding the chromium-reducing functional bacteria and the zero-valent iron-loaded phosphorus-modified biochar prepared by the method to the polluted water containing hexavalent chromium, the method further includes culturing 100 μL of *Microbacterium YT1* bacterial suspension from a preserved glycerol tube to obtain a single colony; using the single colony to prepare a seed culture, inoculating the seed culture into fresh sterile LB liquid medium at an inoculation rate of 1-5%, and culturing it in a constant temperature shaker at 30°C and 150 r / min for 24 h; measuring the absorbance of the bacterial suspension at a wavelength of 600 nm using a UV-Vis spectrophotometer; and adjusting the OD of the bacterial suspension by dilution with sterile LB liquid medium. 600 The value was increased to 2, and microbacterium YT1 was obtained.

[0016] In a preferred embodiment of the present invention, the addition of chromium-reducing functional bacteria and the zero-valent iron-supported phosphorus-modified biochar prepared by the method to polluted water containing hexavalent chromium includes: A simulated chromium-containing wastewater with an initial concentration of 100 mg / L of hexavalent chromium was prepared using potassium dichromate. An appropriate amount of the chromium-containing wastewater was placed in a sterile reaction bottle. The zero-valent iron-loaded phosphorus-modified biochar was added to the sterilized reaction flask and stirred until it was evenly dispersed in the water. The dosage of the zero-valent iron-loaded phosphorus-modified biochar was 1 g / L. Microbacterium YT1 is added to the sterilization reaction bottle, and the amount of Microbacterium YT1 added is 1-5% of the system volume; The sterilized reaction bottle was placed in a constant temperature shaker at 30℃ and 150 r / min for repair, with a total repair time of 36 hours. During the repair process, multiple samples were taken, and the concentration of hexavalent chromium in the water was detected by diphenylcarbazide spectrophotometry, and the removal rate of hexavalent chromium was calculated.

[0017] This invention also provides an application of zero-valent iron-loaded phosphorus-modified biochar in the remediation of hexavalent chromium-contaminated soil. Chromium-reducing functional bacteria and the zero-valent iron-loaded phosphorus-modified biochar prepared by the method are added to hexavalent chromium-contaminated soil to convert the hexavalent chromium in the contaminated soil into elemental chromium. The chromium-reducing functional bacteria is Microbacterium YT1, with accession number GDMCC NO.67734.

[0018] The beneficial effects of this invention are as follows: The preparation method and application of zero-valent iron-supported phosphorus-modified biochar provided by this invention have the following advantages: (1) Phosphorus-modified biochar was obtained by phosphorus modification. Phosphorus-modified biochar has both excellent adsorption performance and microbial carrier function, which can effectively inhibit the agglomeration and passivation of zero-valent iron and enhance the adsorption and chemical reduction effect of hexavalent chromium.

[0019] (2) Zero-valent iron-loaded phosphorus-modified biochar adsorbs hexavalent chromium and provides chemical reduction power, while microbacterium YT1 achieves enhanced biological reduction. The synergistic effect of the two greatly improves the remediation efficiency and stability of chromium-polluted wastewater and soil, solving the defects of single remediation technology.

[0020] (3) The selected microbacterium YT1 has strong chromium resistance and wide environmental adaptability, and can stably perform its functions under complex pollution conditions, thus broadening the application scenarios of the technology.

[0021] (4) In water media remediation, the deep conversion of Cr(VI) into elemental chromium is realized, the toxicity of chromium is completely eliminated, and the potential for chromium resource recovery is also realized, thereby improving the overall technical benefits.

[0022] (5) The preparation process and remediation parameters are clear and highly repeatable. The raw materials are cheap and readily available, the remediation cost is low, and it is suitable for both water and soil pollutants, making it easy to promote and apply in industrial applications. Attached Figure Description

[0023] Figure 1 The XRD patterns of the zero-valent iron-supported phosphorus-modified biochar material prepared in Example 2, and the iron carbide-based biochar and ferrous sulfide-based biochar materials prepared in Comparative Examples 3 and 4 are shown. Figure 2 The curves showing the change of Cr(VI) removal rate in Cr(VI)-containing water bodies by different remediation systems over remediation time; Figure 3 Fine X-ray photoelectron spectroscopy (XPS) spectra of Cr 2p in water after treatment with different remediation systems; Figure 4 YT1+Fe 0 - The curves showing the change in Cr(VI) removal rate with remediation time in wastewater with different initial Cr(VI) concentrations using the PBC synergistic remediation system; Figure 5 For different repair temperatures, YT1+Fe 0 - The curve showing the change in Cr(VI) removal rate of Cr(VI) in Cr(VI)-containing wastewater by the PBC synergistic remediation system over remediation time; Figure 6 For different Fe 0 -PBC dosage, YT1+Fe 0 - The curve showing the change in Cr(VI) removal rate of Cr(VI) in Cr(VI)-containing wastewater by the PBC synergistic remediation system over remediation time; Figure 7 The curves show the changes in the removal rate of Cr(VI) in Cr-contaminated soil by different remediation systems over remediation time. Detailed Implementation

[0024] Preferred embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While preferred embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0025] Example 1: Preparation of phosphorus-modified biochar The steps for preparing phosphorus-modified biochar in this embodiment are as follows: S1: Biomass pretreatment. Biomass can be one or more of tea leaves, straw, and rice husks. In this embodiment, rice straw is selected as raw material. It is washed three times with deionized water to remove surface impurities, dried in a 105°C forced-air drying oven to constant weight, crushed by a high-speed pulverizer, and passed through a 60-mesh standard screen to obtain biomass powder, which is then sealed for later use.

[0026] S2: Phosphoric acid impregnation. Prepare a 2 mol / L H3PO4 solution. Mix the biomass powder with the H3PO4 solution at a mass ratio of 4:1 (H3PO4 solution to biomass dry weight) and place the mixture in a constant temperature shaking oven at 150 r / min for 24 h at room temperature.

[0027] S3: Oxygen-limited pyrolysis. After impregnation, the mixture is dried in a 105℃ forced-air drying oven to constant weight, then transferred to a muffle furnace, sealed with aluminum foil, and heated to 300℃ at a heating rate of 5-10℃ / min, and pyrolyzed at a constant temperature for 2 hours.

[0028] S4: Post-processing. After pyrolysis, nitrogen gas is continuously introduced into the muffle furnace until the system cools naturally to room temperature. The pyrolysis product is then removed, ground, and passed through an 80-mesh standard sieve to obtain phosphorus-modified biochar, denoted as PBC. It is then sealed and stored in a dry environment for later use.

[0029] Biochar is a carbon-rich material produced by the pyrolysis of biomass under oxygen-limited conditions. Phosphorus modification of biochar refers to introducing phosphorus into the structure of biochar through chemical or physical methods to enhance its adsorption capacity for heavy metals or organic pollutants.

[0030] Example 2 Preparation of phosphorus-modified biochar supported by zero-valent iron Zero-valent iron-supported phosphorus-modified biochar is recorded as Fe 0 -PBC, preparation of Fe 0 The specific steps for PBC are as follows: (1) Raw material mixing: Weigh 5 g of the phosphorus-modified biochar prepared in Example 1, weigh 10 g of ferric nitrate nonahydrate as a soluble iron salt, add 500 mL of deionized water, and mix according to the ratio of dry weight of phosphorus-modified biochar: dry weight of iron salt: volume of deionized water = 1:2:100 (w / w / v) and stir evenly to obtain a mixed solution. The soluble iron salt is one or more of ferric nitrate nonahydrate, ferrous sulfate heptahydrate, and ferric chloride hexahydrate, and the purity of the iron salt is ≥98%.

[0031] (2) Loading and impregnation: The above mixture is placed on a magnetic stirrer and stirred continuously at a speed of 200 r / min at room temperature for 24 h to ensure that iron ions are fully loaded into the pores and surface of the phosphorus-modified biochar. Magnetic stirrers are used to drive the stir bar to rotate in a closed container using a magnetic field to achieve uniform mixing of liquids. They are commonly used in chemical reactions and solution preparation.

[0032] (3) Reduction pyrolysis: After stirring, the mixture is placed in a 105℃ forced-air drying oven and dried to constant weight. It is then transferred to a tube furnace and high-purity nitrogen is continuously introduced as an inert atmosphere. The nitrogen flow rate is controlled within the range of 20-50 mL / min. In this example, 30 mL / min is used as an example. The temperature is increased to 700℃ at a heating rate of 5-10℃ / min and pyrolyzed at a constant temperature for 2 h.

[0033] (4) Continuously purge with nitrogen and cool: After pyrolysis, continuously purge with nitrogen until the system cools naturally to room temperature, and then remove the product to obtain Fe. 0 -PBC, sealed and vacuum stored for later use, to prevent zero-valent iron from oxidizing and deactivating upon contact with air.

[0034] Example 3 Preparation of Microbacterium YT1 bacterial culture The microbacteria used in this embodiment ( Microbacterium sp.) YT1 was deposited at the Guangdong Provincial Microbial Culture Collection Center on January 22, 2026, with accession number GDMCC NO.67734. The steps for preparing the microbial culture of YT1 in this embodiment are as follows: (1) Activation of bacterial strain: Under the aseptic environment of the ultra-clean workbench, 100 μL of microbacterium YT1 bacterial suspension was taken from the preserved glycerol tube, streaked onto LB solid medium plates, and incubated upside down in a 30℃ constant temperature incubator for 24 h to obtain single colonies with uniform morphology.

[0035] (2) Seed culture preparation: Select a single colony with good growth on the plate and inoculate it into an Erlenmeyer flask containing 100 mL of sterile LB liquid medium. Place it in a constant temperature shaker at 30℃ and 150 r / min for 18 h to obtain the seed culture.

[0036] (3) Preparation of bacterial culture: The seed culture was inoculated into fresh sterile LB liquid medium at an inoculation rate of 2%, and cultured in a constant temperature shaker at 30℃ and 150 r / min for 24 h. The absorbance of the bacterial culture at 600 nm was measured using a UV-Vis spectrophotometer. The OD of the bacterial culture was adjusted by diluting it with sterile LB liquid medium. 600 The concentration was increased to 2 to obtain the co-repair microbacterium YT1 bacterial culture, which was then refrigerated at 4°C for later use. Sterilized LB liquid medium, composed of tryptone, yeast extract, and sodium chloride, was used to culture the bacterial strain.

[0037] The physiological characteristics of Microbes YT1 are as follows: the optimal growth pH is 6-12, the optimal growth salinity is 0-4% (w / v, calculated as NaCl), the optimal growth temperature is 30 ℃, the colony diameter is 1-2 mm after 24 h of culture in LB medium, and the maximum tolerance concentration to hexavalent chromium, i.e., Cr(VI), is 600 mg / L.

[0038] Example 4: Synergistic remediation of simulated wastewater containing Cr(VI) Cr(VI) represents hexavalent chromium. The steps for preparing Cr(VI) simulated wastewater in this embodiment are as follows: Preparation of simulated wastewater: Potassium dichromate was used to prepare simulated Cr-containing wastewater with an initial Cr(VI) concentration of 100 mg / L. An appropriate amount of wastewater was placed in a sterilized glass reaction flask.

[0039] Construction of the repair system: Fe prepared in Example 2 was added to the reaction flask. 0 -PBC, with an addition amount of 1 g / L, was stirred thoroughly to ensure uniform dispersion of the material in the water; then, the microbacterium YT1 bacterial solution prepared in Example 3 was added at an addition amount of 3% (v / v) of the system volume, and stirred again to mix evenly.

[0040] Co-remediation: Sterilized glass reaction flasks were placed in a constant-temperature shaker at 30℃ and 150 r / min for remediation, with a total remediation time of 36 h. During the remediation process, samples were taken at 0, 6, 12, 18, 24, 30, and 36 h, and the Cr(VI) concentration in the water was determined by diphenylcarbazide spectrophotometry to calculate the Cr(VI) removal rate.

[0041] Comparative Example 1: Single Fe 0 -PBC material for the remediation of Cr(VI)-containing simulated wastewater Except for adding only the Fe prepared in Example 2 to the reaction flask 0 Except for PBC, the other repair conditions, sampling time and detection methods are the same as in Example 4, and the repair time is 36 hours.

[0042] Comparative Example 2: Remediation of Cr(VI)-containing simulated wastewater using a single Microbacterium YT1 inoculum Except for adding only the microbacterium YT1 bacterial solution prepared in Example 3 to the reaction flask, the other remediation conditions, sampling time and detection methods were the same as in Example 4, and the remediation time was 36 h.

[0043] Comparative Example 3: Remediation of Cr(VI)-containing simulated wastewater using iron carbide-based biochar composite material (Fe3C-BC) This comparative example provides a combination of Example 2 and Example 3, namely Fe 0 A comparison of the effects of the -PBC+YT1 coupled system and the Fe3C-BC+YT1 coupled system on the remediation of Cr(VI)-containing simulated wastewater. The preparation method of Fe3C-BC is as follows: 0.4 g of the PBC prepared in Example 1 was mixed with 40 mL of a 17.5 g / L Fe(NO3)3·9H2O solution and shaken for 12 h. The mixture was then dried in an oven at 105 °C. The mixture was then pyrolyzed in a tube furnace under a nitrogen atmosphere for 2 h at 800 °C at a heating rate of 10 °C / min. After natural cooling, the mixture was ground through a 100-mesh sieve to obtain Fe3C-BC.

[0044] The remaining remediation conditions, sampling time, and detection methods for the remediation of Cr(VI)-containing simulated wastewater in this comparative example are the same as those in Example 4.

[0045] Comparative Example 4: Remediation of Cr(VI)-containing simulated wastewater using ferrous sulfide-based biochar composite material (FeS-BC) This comparative example provides Fe 0 A comparison of the remediation effects of the PBC+YT1 coupled system and the FeS-BC+YT1 coupled system on simulated wastewater containing Cr(VI). The preparation method of FeS-BC is as follows: Expired tea leaves were pulverized, dried, and sieved. They were then ball-milled with thiourea and anhydrous ferrous sulfate at a mass ratio of 1:1:1.8 for 10 minutes at 300 rpm, with a ball-to-material ratio of 30:1. The ball-milled product was placed in a covered corundum quartz boat and placed in a high-temperature tube furnace. Pyrolysis was performed for 120 minutes under oxygen-limited conditions (no gas flow) at a temperature of 800 °C and a heating rate of 10 °C / min. After natural cooling to room temperature, the mixture was ground through a 100-mesh sieve to obtain FeS-BC. When using FeS-BC to remediate simulated wastewater containing Cr(VI), the remaining remediation conditions, sampling time, and detection methods were the same as in Example 4.

[0046] The phase composition of the materials prepared in Example 2, Comparative Example 3, and Comparative Example 4 was analyzed using X-ray diffraction (XRD), and the results are as follows: Figure 1 As shown. By Figure 1 It can be seen that the phase of the material prepared in Example 2 is Fe. 0The phase composition of the material prepared in Comparative Example 3 is mainly Fe3C, while the phase composition of the material prepared in Comparative Example 4 is mainly FeS.

[0047] The detection results of this embodiment and Comparative Examples 1-4 correspond to Figure 2 YT1+Fe 0 After 36 hours of remediation using the PBC synergistic remediation system, the removal rate of Cr(VI) in the water reached 99.9%, and the removal rate of YT1+Fe was also reduced. 0 - The PBC synergistic remediation system refers to a system that involves the application of phosphorus-modified biochar loaded with zero-valent iron and Microbacterium YT1 bacterial culture. In Comparative Example 1, after 36 hours of remediation with YT1 alone, the Cr(VI) removal rate was only 83.1%. In Comparative Example 2, with single Fe... 0 After 36 h of remediation with PBC material, the Cr(VI) removal rate was 29.9%. The overall Cr(VI) removal rates of the combination of Fe3C-BC and Microbacterium YT1 in Comparative Example 3, and the combination of FeS-BC and Microbacterium YT1 in Comparative Example 4, were lower than those of YT1+Fe3C-BC after 12-36 h. 0 -PBC Collaborative Repair System.

[0048] X-ray photoelectron spectroscopy (XPS) was used to characterize and analyze the valence state of Cr in the systems after the reaction in Example 4 and Comparative Example 2. The results are as follows: Figure 3 As shown, in the synergistic repair system of Example 4, Cr 0 The composition was 15.9%, Cr(III) accounted for 65.2%, and unreduced Cr(VI) accounted for only 18.9%. Elemental chromium was detected, achieving deep reduction of Cr(VI). However, in the single YT1 system, 28.9% of Cr(VI) remained unreduced.

[0049] Example 5: Verification of water remediation effects under different initial Cr(VI) concentrations This embodiment verifies the water remediation effect of the method of the present invention at different Cr(VI) concentrations, and the test results correspond to... Figure 4 The specific steps are as follows: Simulated Cr-containing wastewater with initial Cr(VI) concentrations of 50, 100, 150, and 200 mg / L were prepared, and appropriate amounts of each were placed in sterilized glass reaction flasks. Fe prepared in Example 2 was added to each reaction flask. 0 -PBC (dosage 0.5-2 g / L, 1 g / L is used as an example in this example) and the Microbacterium YT1 bacterial solution prepared in Example 3 (dosage 1-5% v / v, 3% v / v is used as an example in this example), the OD of Microbacterium YT1 bacterial solution 600 The value was 1.8-2.5. The other repair conditions, sampling time and detection methods were the same as in Example 4, and the repair time was 36 hours.

[0050] The remediation was carried out at 30 °C. After 36 h of remediation, the removal rates of Cr(VI) in simulated wastewater with initial concentrations of 50, 100 and 150 mg / L were 99.9%, 99.4% and 68.0%, respectively, demonstrating that the method of the present invention has excellent remediation effect in the Cr(VI) concentration range of 50~150 mg / L and strong environmental adaptability.

[0051] Example 6: Verification of water remediation effects under different temperature conditions This embodiment verifies the water remediation effect of the method of the present invention at different temperatures, and the test results correspond to... Figure 5 The specific steps are as follows: Simulated Cr-containing wastewater with an initial Cr(VI) concentration of 100 mg / L was prepared, and appropriate amounts were placed in sterilized glass reaction flasks. Fe2+ prepared in Example 2 was added to each sterilized glass reaction flask. 0 -PBC (dosage 1 g / L) and the Microbacterium YT1 bacterial suspension prepared in Example 3 (dosage 3% v / v). Each sterilized glass reaction bottle was placed in a constant temperature shaker at 10℃, 20℃, 30℃, and 40℃ (speed 150 r / min) for repair, with a total repair time of 36 h; the remaining sampling time and detection methods were the same as in Example 4.

[0052] Water remediation results are as follows Figure 5 As shown, at 30℃ (the optimal growth temperature for Microbacterium YT1), the Cr(VI) removal rate reached 99.9% after 36 h of remediation, representing the optimal remediation effect. At 20℃, the Cr(VI) removal rate was 71.5%. At 40℃, the Cr(VI) removal rate was 85.2%. At a low temperature of 10℃, the Cr(VI) removal rate was 37.1%. These results indicate that the method of this invention still has good remediation effects within the temperature range of 20–40℃. Low temperatures significantly inhibit bacterial activity and material reaction efficiency. In practical applications, the remediation time can be appropriately adjusted according to the ambient temperature.

[0053] Example 7 Different Fe 0 -Verification of water remediation effects under PBC dosage This embodiment verifies the method of the present invention in different Fe... 0 -Water remediation effect at PBC dosage, corresponding test results Figure 6 The specific steps are as follows: Simulated Cr-containing wastewater with an initial Cr(VI) concentration of 100 mg / L was prepared, and appropriate amounts were placed in sterilized glass reaction flasks. Microbacterium YT1 bacterial suspension prepared in Example 3 (3% v / v) was added to each sterilized glass reaction flask, and Fe2+ prepared in Example 2 was added to each flask. 0-PBC was added at concentrations of 0, 0.5, 1 and 2 g / L respectively; each reaction flask was placed in a constant temperature shaker at 30°C and 150 r / min for repair, with a total repair time of 36 h. The sampling time and detection method were the same as in Example 4.

[0054] like Figure 6 As shown, when Fe 0 - With a PBC dosage of 0 g / L, the removal rate of Cr(VI) was 79.5% after 36 h. When Fe 0 - PBC dosages of 0.5, 1.0, and 2.0 g / L resulted in Cr(VI) removal rates of 91.1%, 99.9%, and 99.9% after 36 h, respectively. These results indicate that Fe... 0 The addition of PBC can significantly improve remediation efficiency. 1.0 g / L is the optimal dosage. Further increases in dosage will have limited improvement in remediation efficiency. In practical applications, the dosage of 0.5~2.0 g / L can be selected according to the Cr(VI) concentration in the water.

[0055] Example 8: Synergistic Remediation of Cr-Contaminated Soil This embodiment verifies the synergistic remediation effect of zero-valent iron-loaded phosphorus-modified biochar and Microbacterium YT1 bacterial solution on Cr-contaminated soil. The test results correspond to... Figure 7 The specific steps are as follows: Pretreatment of test soil: Uncontaminated farmland soil was collected, and impurities such as gravel and plant residues were removed from the soil. A certain concentration of Cr(VI) solution was added to the soil, and the soil was aged for 30 days and then air-dried naturally. The soil was then ground through a 2 mm standard sieve, and the initial concentration of Cr(VI) in the soil was found to be 190 mg / kg. The soil was then sealed for later use.

[0056] Construction of the remediation system: Weigh 50 g of the pretreated Cr-contaminated soil and place it in a sterile beaker; add the Microbacterium YT1 bacterial solution prepared in Example 3 to the soil (the dosage range is 0.05-0.2 mL per gram of dry soil; this example uses a dosage of 0.1 mL per gram of dry soil as an example). The OD of the Microbacterium YT1 bacterial solution... 600 (Value 1.8-2.5), and Fe prepared in Example 2 was added simultaneously. 0 -PBC (addition amount is 0.3% w / w of soil dry weight).

[0057] Synergistic remediation: Add sterile deionized water to a beaker to adjust the soil moisture content to 40% of field capacity, and stir thoroughly to ensure the bacterial solution and Fe are properly mixed. 0 - Mix PBC evenly with soil; cover the beaker with a vent hole and place it in a 30℃ constant temperature incubator for static incubation and repair, with a total repair time of 10 days; supplement with sterile deionized water daily during the repair process to maintain stable soil moisture content.

[0058] After remediation, the Cr(VI) content in the soil was determined by the alkaline digestion-diphenylcarbazide spectrophotometric method as specified in the "Soil Environmental Quality Standard for Construction Land Soil Pollution Risk Control" (GB 36600-2018) or the "Soil Environmental Quality Standard for Agricultural Land Soil Pollution Risk Control" (GB 15618-2018).

[0059] After 10 days of repair, YT1+Fe 0 The Cr(VI) content in the soil treated by the PBC synergistic remediation system decreased to 0.14 mg / kg, far below the Cr(VI) screening value of 3.0 mg / kg for Class I land use in GB 36600-2018, meeting the requirements of the national soil environmental quality standards. (Single YT1 inoculant and single Fe...) 0 The remediation system using PBC material showed a significantly lower removal rate of Cr(VI) in the soil compared to the synergistic system. After remediation, the Cr(VI) content in the soil was 22.0 and 80.7 mg / kg, respectively, which did not meet the relevant national standards.

[0060] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, apparatus, article, or method that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, apparatus, article, or method. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, apparatus, article, or method that includes that element.

[0061] The above description is only a preferred embodiment of this application and does not limit the patent scope of this application. Any equivalent structural or procedural changes made based on the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A method for preparing zero-valent iron-supported phosphorus-modified biochar, characterized in that, include: Biomass is pretreated to obtain biomass powder; The biomass powder was impregnated in an H3PO4 solution to obtain an impregnation mixture; The impregnation mixture was subjected to oxygen-limited pyrolysis at 300-500 °C to obtain phosphorus-modified biochar; The phosphorus-modified biochar, soluble iron salt, and deionized water were mixed at a mass-volume ratio of 1:2:100 to obtain a mixed solution. The mixture was post-treated by reducing pyrolysis at 500-700 °C under a nitrogen atmosphere, and after natural cooling, zero-valent iron-supported phosphorus-modified biochar was obtained.

2. The method for preparing zero-valent iron-supported phosphorus-modified biochar according to claim 1, characterized in that, The pretreatment of biomass to obtain biomass powder includes: Wash the biomass repeatedly with deionized water three times. The cleaned biomass was dried in a 105℃ forced-air drying oven until constant weight. The dried biomass is crushed using a pulverizer; The crushed biomass is passed through a 60-mesh sieve to obtain biomass powder; the biomass is any one or any combination of tea leaves, straw and rice husks.

3. The method for preparing zero-valent iron-supported phosphorus-modified biochar according to claim 1, characterized in that, The biomass powder is impregnated in an H3PO4 solution to obtain an impregnation mixture, comprising: The biomass powder and H3PO4 solution were mixed at a mass ratio of 4 to 1:1 to obtain the mixed biomass; the concentration of the H3PO4 solution was 1-3 mol / L. The mixed biomass was placed in a constant temperature shaking chamber and impregnated at room temperature for 24 h at a rotation speed of 150 r / min to obtain the impregnated mixture.

4. The method for preparing zero-valent iron-supported phosphorus-modified biochar according to claim 1, characterized in that, The impregnation mixture is subjected to oxygen-limited pyrolysis to obtain phosphorus-modified biochar, comprising: The impregnation mixture was dried in a 105°C forced-air drying oven to constant weight, then transferred to a muffle furnace, sealed with aluminum foil, and heated to 300-500°C at a rate of 5-15°C / min. The mixture was then pyrolyzed at a constant temperature for 0.5-2 h, washed, dried, and ground through a 65-100 mesh sieve to obtain phosphorus-modified biochar.

5. The method for preparing zero-valent iron-supported phosphorus-modified biochar according to claim 1, characterized in that, The process involves mixing the phosphorus-modified biochar, soluble iron salt, and deionized water at a mass-to-volume ratio of 1:2:100 to obtain a mixed solution comprising: Mix 5 g of phosphorus-modified biochar, 10 g of soluble iron salt and 500 mL of deionized water and stir until homogeneous to obtain a mixture; the soluble iron salt is any one or any combination of ferric nitrate nonahydrate, ferrous sulfate heptahydrate and ferric chloride hexahydrate.

6. The method for preparing zero-valent iron-supported phosphorus-modified biochar according to claim 1, characterized in that, The mixture is post-treated by reduction pyrolysis at 500-700 °C under a nitrogen atmosphere, followed by natural cooling to obtain zero-valent iron-supported phosphorus-modified biochar, comprising: The mixture was placed in an oven and dried at 105 °C to obtain the precursor. After drying, the precursor was placed in a tube furnace and heated to 500-700 °C at a programmed heating rate of 5-15 °C / min under a nitrogen atmosphere. It was then pyrolyzed at a constant temperature for 0.5-2 h. After natural cooling, it was ground through a 65-100 mesh sieve to obtain zero-valent iron-supported phosphorus-modified biochar.

7. The application of zero-valent iron-supported phosphorus-modified biochar in the remediation of hexavalent chromium-contaminated water, characterized in that, The zero-valent iron-loaded phosphorus-modified biochar prepared by the method according to any one of claims 1-6 is added to polluted water containing hexavalent chromium to convert the hexavalent chromium in the polluted water into elemental chromium. The chromium-reducing bacteria is Microbacterium YT1, with accession number GDMCC NO.67734.

8. The application of zero-valent iron-supported phosphorus-modified biochar according to claim 7 in the remediation of hexavalent chromium-contaminated water, characterized in that, Before adding the zero-valent iron-loaded phosphorus-modified biochar prepared by the method according to any one of claims 1-6 to the polluted water containing hexavalent chromium, the procedure further includes culturing 100 μL of *Microbacterium YT1* bacterial suspension from a preserved glycerol tube to obtain a single colony; using the single colony to prepare a seed culture, inoculating the seed culture into fresh sterile LB liquid medium at an inoculation rate of 1-5%, and culturing it in a constant temperature shaker at 30℃ and 150 r / min for 24 h; detecting the absorbance of the bacterial suspension at a wavelength of 600 nm using a UV-Vis spectrophotometer; and adjusting the OD of the bacterial suspension by dilution with sterile LB liquid medium. 600 The value was increased to 2, and microbacterium YT1 was obtained.

9. The application of zero-valent iron-supported phosphorus-modified biochar according to claim 7 in the remediation of hexavalent chromium-contaminated water, characterized in that, The step of adding zero-valent iron-loaded phosphorus-modified biochar prepared by the method according to any one of claims 1-6 to polluted water containing hexavalent chromium includes: A simulated chromium-containing wastewater with an initial concentration of 100 mg / L of hexavalent chromium was prepared using potassium dichromate. An appropriate amount of the chromium-containing wastewater was placed in a sterile reaction bottle. The zero-valent iron-loaded phosphorus-modified biochar was added to the sterilized reaction flask and stirred until it was evenly dispersed in the water. The dosage of the zero-valent iron-loaded phosphorus-modified biochar was 1 g / L. Microbacterium YT1 is added to the sterilization reaction bottle, and the amount of Microbacterium YT1 added is 1-5% of the system volume; The sterilized reaction bottle was placed in a constant temperature shaker at 30℃ and 150 r / min for repair, with a total repair time of 36 h. During the repair process, multiple samples were taken, and the concentration of hexavalent chromium in the water was detected by diphenylcarbazide spectrophotometry, and the removal rate of hexavalent chromium was calculated.

10. The application of zero-valent iron-supported phosphorus-modified biochar in the remediation of hexavalent chromium-contaminated soil, characterized in that, The zero-valent iron-loaded phosphorus-modified biochar prepared by the method according to any one of claims 1-6 is added to the contaminated soil containing hexavalent chromium to convert the hexavalent chromium in the contaminated soil into elemental chromium. The chromium-reducing bacteria is Microbacterium YT1, with the accession number GDMCC NO.67734.

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