Method for degrading organic halogenated pollutants by in-situ generation of feox / mnox from fe / mn in groundwater based on prb

Abstract

A method for in-situ generation of FeOx / MnOx from groundwater based on PRB for the degradation of organohalogenated pollutants, relating to the fields of groundwater remediation and advanced oxidation technologies. The purpose of this invention is to address the problems of high energy consumption, low efficiency, and cumbersome processes in existing short-chain chlorinated paraffin groundwater remediation technologies. Method: A mixture of prepared simulated groundwater and an oxidant is pumped into a PRB simulation column to degrade short-chain chlorinated paraffins; the concentration of short-chain chlorinated paraffins in the PRB simulation column is monitored, and the degradation efficiency is maintained at 90-100%. This invention provides a method for in-situ generation of FeOx / MnOx from groundwater based on PRB for the degradation of organohalogenated pollutants.

Description

Technical Field

[0001] This invention relates to the field of groundwater pollution remediation and advanced oxidation technology, specifically to an oxidation method based on a permeable reactive barrier (PRB) for the in-situ conversion of Fe / Mn in groundwater into iron / manganese oxides (FeOx / MnOx) to degrade organic halogenated pollutants. Background Technology

[0002] Short-chain chlorinated paraffins (SCCPs) are a class of carbon chain C 10 ~C 13 Mixtures of straight-chain chlorinated hydrocarbons with a chlorine content of 40%–70% are classified as controlled persistent organic pollutants (POPs) due to their persistence, bioaccumulation, and high toxicity. Widely used in metal processing, plastics, and coatings, they are highly susceptible to leakage into groundwater during production, use, and disposal. Because of their stable chemical properties, high chlorine content, and poor biodegradability, groundwater contamination is extremely difficult to treat and poses a long-term threat to drinking water safety and ecosystems.

[0003] Currently, remediation methods for SCCP contamination in groundwater mainly include: pump-and-treatment methods, which require pumping groundwater to the surface for treatment, resulting in high energy consumption and significant tailing effects; microbial remediation methods, which suffer from extremely low degradation rates due to the high chlorination and poor bioavailability of SCCPs; and permeable reactive barrier (PRB) technology, which requires no above-ground facilities and has low energy consumption, but traditional PRB media suffer from slow reduction and dechlorination, easy generation of toxic intermediate products, and reliance on physical adsorption. Existing iron-manganese oxide catalysts are mostly exogenous nanomaterials, which suffer from problems such as aggregation, restricted migration, and difficulty in recycling, and their preparation and application processes are cumbersome, making them unsuitable for complex groundwater environments. Many groundwater bodies are naturally rich in Fe. 2+ and Mn 2+ Ions, which are considered impurities to be removed in traditional water treatment, have not been effectively utilized as potential precursors for the in-situ construction of highly efficient oxidation catalysts.

[0004] Therefore, there is an urgent need to develop a method that can utilize the inherent conditions of groundwater or trace amounts of externally added iron / manganese sources to convert them in situ into highly active FeOx / MnOx within a PRB column, and then degrade SCCPs in a long-term and efficient manner through advanced oxidation pathways, thereby achieving low-cost and low-secondary-pollution in-situ remediation to overcome the shortcomings of existing technologies. Summary of the Invention

[0005] The purpose of this invention is to address the problems of high energy consumption, low efficiency, and cumbersome processes in existing short-chain chlorinated paraffin groundwater remediation technologies, and to provide a method for the in-situ generation of FeOx / MnOx from groundwater Fe / Mn based on PRB to degrade organic halogenated pollutants.

[0006] A method for in-situ generation of FeOx / MnOx from groundwater Fe / Mn based on PRB for the degradation of organic halogenated pollutants is carried out according to the following steps:

[0007] Step S1:

[0008] A PRB simulation column is constructed. The PRB simulation column is a cylindrical reaction column. The reaction column is filled from bottom to top with a bottom layer of quartz sand packing, an activated carbon-zeolite mixed packing layer and a top layer of quartz sand packing. The reaction column adopts a bottom-in, top-out upflow water inlet method.

[0009] Step S2:

[0010] Prepare simulated groundwater, wherein the simulated groundwater contains Fe 2+ Ions, Mn 2+ Ionic and short-chain chlorinated paraffins;

[0011] Step S3:

[0012] After mixing the simulated groundwater prepared in step S2 with the oxidant, the mixture is pumped into the PRB simulation column constructed in step S1 to simulate Fe in the groundwater. 2+ Ions and Mn 2+ Under the induction of an oxidant, ions generate an in-situ FeOx / MnOx composite catalytic layer on the surface of an activated carbon-zeolite mixed packing material, and the FeOx / MnOx composite catalytic layer degrades short-chain chlorinated paraffins;

[0013] Step S4:

[0014] The concentration of short-chain chlorinated paraffins at each sampling port and outlet of the PRB simulation column was monitored, and the concentration was adjusted by changing the hydraulic retention time, oxidant dosage, or Fe. 2+ Ions and Mn 2+ The ion ratio is adjusted to maintain a degradation efficiency of 90-100%.

[0015] The principle of this invention:

[0016] The in-situ generation principle of the FeOx / MnOx catalyst in this invention is: to generate FeOx in situ... 2+ / Mn 2+ Simulated groundwater mixed with persulfate was introduced into an upflow PRB simulation column. As the water flowed through the activated carbon and zeolite mixed packing material, Fe... 2+ / Mn 2+An electron transfer reaction occurs under the oxidation-induced effect of persulfate, generating an in-situ, predominantly amorphous FeOx / MnOx complex, which is uniformly loaded onto the packing surface, forming a reaction interface with long-lasting catalytic activity. The high specific surface area of ​​activated carbon and the porous structure of zeolite provide ample sites for catalyst nucleation and immobilization. This process requires no additional modification to the packing, directly utilizing the natural Fe / Mn components in groundwater, making it simple to operate and cost-effective.

[0017] The principle of PRB-simulated column-coupled FeOx / MnOx catalytic degradation of SCCPs in this invention is based on an adsorption-advanced oxidation synergistic mechanism: the activated carbon and zeolite mixed packing material rapidly adsorbs and enriches hydrophobic SCCPs, shortening the free radical diffusion distance; the FeOx / MnOx generated in situ contains multiple Fe and Mn valence states, which efficiently activate the oxidant through valence state cycling and internal electron transfer, continuously generating sulfate free radicals. or hydroxyl radicals Highly reactive free radicals preferentially attack the carbon-chlorine bonds in SCCP molecules, initiating stepwise dechlorination and carbon chain breakage, ultimately mineralizing SCCPs completely into CO2, H2O, and Cl. - The entire process is dominated by in-situ catalytic oxidation, with no secondary pollution, achieving efficient and green remediation of groundwater SCCPs.

[0018] The beneficial effects of this invention are:

[0019] (1) The core beneficial effect of the system of this invention lies in its synergistic, long-lasting, and safe degradation mechanism. Specifically, through the structural advantages of the PRB simulated column and the in-situ generation of FeOx / MnOx catalyst, the system can continuously provide highly active oxide species ( and This invention achieves precise and efficient bond breaking of the C-Cl bonds in short-chain chlorinated paraffins, fundamentally completing dechlorination, oxidation, and mineralization degradation. The in-situ catalysis coupled with PRB design overcomes the shortcomings of traditional technologies, such as easy catalyst loss, short reaction time, and unstable degradation efficiency, achieving sustained and efficient remediation. Simultaneously, the in-situ heterogeneous catalytic oxidation pathway significantly reduces iron sludge formation and avoids water ion imbalance caused by the addition of high concentrations of metal salts, aligning with the development needs of green remediation.

[0020] (3) The system of this invention is highly adaptable to complex groundwater environments. The free radicals generated by catalyst activation can fully contact and degrade SCCPs dissolved in groundwater, and it has good environmental compatibility with minimal disturbance to the aquifer ecosystem. The activated carbon / zeolite packings used in the system are all environmentally friendly materials, requiring no complex equipment debugging or forced pH control, and can operate stably under neutral to weakly alkaline conditions. This invention provides an economical, efficient, and green reliable solution for the in-situ remediation of SCCP-contaminated groundwater, and can directly provide technical reference for on-site permeable reactive barrier (PRB) projects.

[0021] This invention provides a method for in-situ generation of FeOx / MnOx from groundwater based on PRB to degrade organic halogenated pollutants. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the in-situ advanced oxidation treatment device for the PRB simulation column in this invention.

[0023] Figure 2 This chart shows a comparison of the removal rates of short-chain chlorinated paraffins in groundwater using three modes: pure filter media adsorption, pre-loaded iron and manganese oxides, and simultaneous in-situ conversion with influent.

[0024] Figure 3 The diagram shows a comparison of the in-situ oxidation and capture effects of ozone or potassium persulfate on iron and manganese ions in groundwater when using ozone or potassium persulfate as different oxidants.

[0025] Figure 4 The graph shows the degradation effect of the PRB simulation column on short-chain chlorinated paraffins in groundwater under different Fe / Mn molar ratios according to the present invention.

[0026] Figure 5 The graph shows a comparison of the effects of three systems—pure filter media adsorption, hydrogen peroxide oxidation, and persulfate oxidation—on the removal rate of short-chain chlorinated paraffins under different hydraulic retention times (HRT) conditions according to the present invention. Detailed Implementation

[0027] Specific Implementation Method 1: This implementation method is based on the in-situ generation of FeOx / MnOx from groundwater Fe / Mn using PRB to degrade organic halogenated pollutants, and is carried out according to the following steps:

[0028] Step S1:

[0029] A PRB simulation column is constructed. The PRB simulation column is a cylindrical reaction column. The reaction column is filled from bottom to top with a bottom layer of quartz sand packing, an activated carbon-zeolite mixed packing layer and a top layer of quartz sand packing. The reaction column adopts a bottom-in, top-out upflow water inlet method.

[0030] Step S2:

[0031] Prepare simulated groundwater, wherein the simulated groundwater contains Fe 2+ Ions, Mn 2+ Ionic and short-chain chlorinated paraffins;

[0032] Step S3:

[0033] After mixing the simulated groundwater prepared in step S2 with the oxidant, the mixture is pumped into the PRB simulation column constructed in step S1 to simulate Fe in the groundwater. 2+ Ions and Mn 2+ Under the induction of oxidant, FeOx / MnOx composite catalytic layer is generated in situ on the surface of activated carbon-zeolite mixed filler. The FeOx / MnOx composite catalytic layer continuously activates the oxidant to generate sulfate radicals or hydroxyl radicals, which attack the C-Cl bonds in short-chain chlorinated paraffin molecules, thereby achieving dechlorination, chain breaking and mineralization degradation.

[0034] Co-influent: Oxidizing agents (such as potassium persulfate, H2O2, etc.) are added to the water containing SCCPs and Fe at a specific excess coefficient (1.05~10). 2+ and Mn 2+ The groundwater was mixed online; the mixture was pumped into the PRB simulation column using a peristaltic pump;

[0035] The dosage of the oxidant is based on the Fe in the influent. 2+ and Mn 2+ The concentration is determined by calculation, and the calculation formula is: n 总 = k( n 理论Fe + n 理论Mn ); where n 理论Fe and n 理论Mn Fe in the influent 2+ Oxidation to Fe(III) and oxidation of Mn 2+ The theoretical stoichiometric molar amount of oxidant required to oxidize to Mn(IV), where k is the excess oxidant coefficient;

[0036] In-situ generation and dynamic loading of FeOx / MnOx catalysts: When Fe in step S2 2+ Mn 2+ After contact and mixing with the oxidant, it is rapidly oxidized and flows into the PRB column with water in the form of amorphous FeOx / MnOx, where it is deposited in situ in the pores and surface of the porous medium, thus constructing a highly active heterogeneous catalytic interface.

[0037] Activated carbon adsorbs and enriches SCCPs in groundwater onto the surface of the packing material, facilitating free radical reactions. The FeOx / MnOx generated in step S3 catalyzes and activates the oxidant, producing free radicals (…). or Free radicals attack the C-Cl bonds of SCCPs, mineralizing and degrading them, and the treated water is discharged from the outlet.

[0038] Step S4:

[0039] The concentration of short-chain chlorinated paraffins at each sampling port and outlet of the PRB simulation column was monitored, and the concentration was adjusted by changing the hydraulic retention time, oxidant dosage, or Fe. 2+ Ions and Mn 2+ The ion ratio is adjusted to maintain a degradation efficiency of 90-100%.

[0040] Specific Implementation Method Two: The difference between this implementation method and Specific Implementation Method One is that the height of the PRB simulation column in step S1 is 50~100 cm and the inner diameter is 2~10 cm; a sampling port is set every 10~15 cm on the side wall of the PRB simulation column.

[0041] The other steps are the same as in Specific Implementation Method 1.

[0042] Specific Implementation Method 3: The difference between this implementation method and Specific Implementation Method 1 or 2 is that: the thickness of the bottom quartz sand filler layer and the top quartz sand filler layer in step S1 is 5~10 cm, and the particle size of the quartz sand is 1~2 mm; the thickness of the activated carbon-zeolite mixed filler layer is 40~80 cm, the mass ratio of activated carbon to zeolite is (1~3):1, the particle size of activated carbon is 20~40 mesh, and the particle size of zeolite is 3~4 mm.

[0043] The other steps are the same as in specific implementation method one or two.

[0044] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that: the Fe in the simulated groundwater described in step S2... 2+ The mass concentration of ions is 2~4 mg / L, Mn 2+ The mass concentration of the ions was 2–4 mg / L, and the initial mass concentration of the short-chain chlorinated paraffins was 150–500 μg / L.

[0045] Fe 2+ With Mn 2+ The concentration ratios are 1:0 (2 mg / L : 0 mg / L), 1:1 (2 mg / L : 2 mg / L), 1:2 (2 mg / L : 4 mg / L), 2:1 (4 mg / L : 2 mg / L), or 0:1 (0 mg / L : 2 mg / L).

[0046] The other steps are the same as those in Specific Implementation Methods One to Three.

[0047] Specific Implementation Method Five: The difference between this implementation method and Specific Implementation Methods One to Four is that the Fe... 2+ Ions and Mn 2+ The molar ratio of the ions is (1~5):(1~5).

[0048] The other steps are the same as those in Specific Implementation Methods One through Four.

[0049] Specific Implementation Method Six: The difference between this implementation method and Specific Implementation Methods One to Five is that the oxidant mentioned in step S3 is one or more of potassium persulfate, sodium persulfate, hydrogen peroxide, potassium persulfate monohydrogen phosphate, potassium permanganate, and ozone.

[0050] The excess oxidant coefficient k ranged from 1.05 to 10.0. The degradation efficiency was optimized by adjusting the excess coefficient k, which was set to 1.05, 1.1, 1.2, 1.5, 2.0, 5.0, and 10.0 respectively.

[0051] When k = 1.0, the amount of oxidant added is just enough to reduce Fe 2+ and Mn 2+ In-situ conversion to FeOx / MnOx;

[0052] When k > 1.0, the excess oxidant generates strong oxidizing free radicals under the catalytic action of FeOx / MnOx generated in situ, which are used to degrade SCCPs.

[0053] When k is too large, the excess oxidant will produce a self-quenching reaction, and the degradation efficiency will tend to level off or decrease slightly.

[0054] The other steps are the same as those in Specific Implementation Methods 1 to 5.

[0055] Specific Implementation Method Seven: The difference between this implementation method and Specific Implementation Methods One to Six is ​​that the hydraulic residence time of the simulated groundwater in the PRB simulation column in step S3 is 1 to 2 hours.

[0056] The other steps are the same as those in Specific Implementation Methods 1 to 6.

[0057] Specific Implementation Method Eight: The difference between this implementation method and Specific Implementation Methods One to Seven is that the pH value of the simulated groundwater in step S3 is 6.0~8.0 and the temperature is 10~20℃.

[0058] The other steps are the same as those in Specific Implementation Methods 1 to 7.

[0059] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One through Eight in that the simulated groundwater described in step S3 also contains coexisting interfering ions, namely Cl... - HCO3- and NO3 - At least one of them.

[0060] The other steps are the same as those in Specific Implementation Methods 1 to 8.

[0061] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Methods One to Nine in that the concentration of Cl⁻ is 0.05~0.2 mmol / L (approximately 1.8~7.1 mg / L), and the concentration of HCO₃⁻ is... - The concentration of NO3 was 1–6 mmol / L (approximately 61–366 mg / L). - The concentration is 0.05~0.15 mmol / L (approximately 3.1~9.3 mg / L).

[0062] The other steps are the same as those in Specific Implementation Methods 1 to 9.

[0063] The beneficial effects of the present invention are verified using the following embodiments:

[0064] Example 1: A method for in-situ generation of FeOx / MnOx from groundwater based on PRB to degrade organic halogenated pollutants, comprising the following steps:

[0065] Step S1:

[0066] An organic glass column with an inner diameter of 10 cm and a height of 50 cm was used, with sampling ports every 10 cm on the side wall; an upflow operation mode with bottom water inlet and top water outlet was adopted; the column was filled from bottom to top with a support layer (5 cm quartz sand), a core reaction layer (40 cm activated carbon and zeolite mixed packing material) and a filter layer (5 cm quartz sand) to obtain the PRB reaction column.

[0067] Step S2:

[0068] Using Wahaha purified water as a base instead of deionized water, 1 mL of a 750 mg / L short-chain chlorinated paraffin stock solution was added, along with 4 mg / L Fe. 2+ 2 mg / L Mn 2+ Ions were used as catalyst precursors to prepare 5L of groundwater containing 150 ug / L of SCCPs; potassium persulfate was mixed online with the simulated groundwater at an excess coefficient of 1.05; the groundwater containing SCCPs was continuously introduced using a peristaltic pump with a LongerPump 25# hose in the inlet pipe and the pump speed was adjusted to 5 rpm to make the hydraulic residence time (HRT) of the simulated groundwater in the PRB column 2 h;

[0069] The dosage of the oxidant is based on the Fe in the influent. 2+ and Mn 2+ The concentration is determined by calculation, and the calculation formula is: n总 = k( n 理论Fe + n 理论Mn ); where n 理论Fe and n 理论Mn Fe in the influent 2+ Oxidation to Fe(III) and oxidation of Mn 2+ The theoretical stoichiometric molar amount of oxidant required to oxidize to Mn(IV), where k is the excess oxidant coefficient;

[0070] The 750 mg / L short-chain chlorinated paraffin stock solution: 7.5 mL of the standard solution of short-chain chlorinated paraffin was blown to near dryness at 50 °C, and acetone was added to make up to 1 mL to obtain a 750 mg / L short-chain chlorinated paraffin stock solution.

[0071] The standard solution of the short-chain chlorinated paraffin has a carbon chain length of C. 10 -C 13 Chlorine content 55%, concentration 100mg / L, CAS number 85535-84-8;

[0072] Step S3:

[0073] When Fe in step S2 2+ Mn 2+ After contact and mixing with the oxidant, it is rapidly oxidized and flows into the PRB column with water in the form of amorphous FeOx / MnOx, where it is deposited in situ in the pores and surface of the porous medium, thus constructing a highly active heterogeneous catalytic interface.

[0074] Step S4:

[0075] Activated carbon adsorbs and enriches SCCPs in groundwater onto the surface of the packing material, facilitating free radical reactions. The FeOx / MnOx generated in step S3 catalyzes and activates the oxidant, producing free radicals (…). or Free radicals attack the C-Cl bonds of SCCPs, mineralizing and degrading them, and the treated water is discharged from the outlet.

[0076] Using the method of this embodiment, the degradation rate of short-chain chlorinated paraffins in groundwater is 97.95%.

[0077] Example 2: The difference between this example and Example 1 is that no oxidant is added in step S2; the other steps and parameters are the same as in Example 1.

[0078] In Example 2, the degradation rate of short-chain chlorinated paraffins in groundwater was 65.8%.

[0079] Figure 1This diagram illustrates the structure of the in-situ advanced oxidation treatment device using a PRB simulated column in this invention. The device mainly consists of a simulated groundwater bottle, an oxidant storage bottle, a peristaltic pump, a three-way online mixing connector, and the PRB simulated column. The PRB simulated column is made of plexiglass (10 cm inner diameter, 50 cm height), and its interior is filled from bottom to top with a 5 cm quartz sand support layer, a 40 cm activated carbon / zeolite mixed packing (core reaction layer), and a 5 cm quartz sand filter layer. During the experiment, simulated groundwater and oxidant are pumped into the three-way connector at a constant flow rate via the peristaltic pump for instantaneous mixing, and then enter the simulated column from the bottom.

[0080] Figure 2 The diagram shows a comparison of the removal rates of short-chain chlorinated paraffins in groundwater using three modes: pure filter media adsorption, pre-loaded iron and manganese oxides, and simultaneous in-situ conversion with influent. By evaluating the degradation performance of the three different operating strategies, the technical advantages of the core process of this invention are clarified.

[0081] Pure filter media adsorption mode (control group): In this mode, the PRB simulation column is filled only with a mixture of activated carbon and zeolite, without the addition of catalyst precursors. Initially, the well-developed pore structure of activated carbon produces a certain adsorption and removal effect, but as the adsorption sites are gradually occupied by pollutants, the removal rate shows a rapid decline trend, proving that simple adsorption cannot achieve long-term purification of SCCPs.

[0082] Pre-loaded iron-manganese oxide mode (control group): This mode employs a strategy of first loading an active coating of FeOx / MnOx onto the packing surface, followed by the introduction of groundwater containing oxidant. Due to sufficient initial active sites, the system exhibits high degradation efficiency in the early stages of operation; however, as the reaction continues, the generated intermediate products gradually cover or block the catalytic active sites, and due to the lack of subsequent precursor ion supply, the catalytic interface becomes passivated, leading to a significant decrease in degradation performance over extended operating time.

[0083] Synchronous online in-situ conversion mode (Example 1): This mode utilizes precursor ions Fe 2+ Mn 2+ The precursor reacts instantaneously with the oxidant in the online reaction before entering the core reaction layer, generating an amorphous FeOx / MnOx composite oxide with extremely high specific surface area and catalytic activity. More importantly, because the precursor is continuously injected with the water flow and dynamically loaded into the pores of the packing material, in-situ dynamic compensation of the catalytic sites is achieved.

[0084] Depend on Figure 2The comparison results show that the synchronous water inlet mode described in this invention effectively solves the technical bottleneck of easy deactivation and difficult regeneration of traditional heterogeneous catalytic systems through this dynamic regeneration mechanism. Its SCCP removal rate shows significant superiority and long-term stability compared with the other two modes, and the removal rate can be stably maintained at over 83%~90%.

[0085] Figure 3 This invention presents a comparative diagram showing the in-situ oxidation and capture effects of iron and manganese ions in groundwater when using ozone or potassium persulfate as different oxidants. It also compares the conversion efficiency of gaseous oxidants (ozone) and liquid oxidants (persulfate) on catalyst precursor ions. Experimental results show that the capture efficiency is not ideal when using ozone; however, with persulfate, due to the absence of gas-liquid mass transfer resistance, dissolved iron and manganese ions can be more thoroughly converted into solid oxides and "captured" on the surface of the PRB packing, thereby constructing a higher-load catalytic interface and effectively reducing the risk of heavy metal loss.

[0086] Figure 4 This diagram illustrates the degradation effect of a PRB simulation column on short-chain chlorinated paraffins (SCCPs) in groundwater under different Fe / Mn molar ratios. Five molar ratios (0:1, 1:2, 1:1, 2:1, and 1:0) were selected for the experiment, with persulfate as the oxidant. The results show that at 0.5 h, the Fe:Mn=2:1 system exhibited the fastest reaction kinetics, achieving a removal rate of 83.95%, significantly higher than the single manganese system (46.14%) or the single iron system (50.44%). When the reaction proceeded to 1.5 h, the removal rate at the 2:1 ratio further increased to 97.1%. This indicates a significant synergistic effect between the iron-manganese composite oxides. The manganese oxide, acting as an electron transfer mediator, accelerated the redox cycle of iron ions, thereby generating more sulfate radicals to attack the C-Cl bonds of SCCPs.

[0087] Figure 5This diagram shows a comparison of the effects of three systems—pure filter media adsorption (Example 2), hydrogen peroxide oxidation, and persulfate oxidation (Example 1)—on the removal rate of short-chain chlorinated paraffins under different hydraulic retention times (HRT). The HRT was controlled within the range of 0.5 h to 2.0 h. With increasing retention time, the removal rate of each system increased. At an HRT of only 0.5 h, the removal rates of both the persulfate and hydrogen peroxide systems exceeded 80%, exhibiting extremely rapid reaction kinetics. The persulfate system showed a higher removal rate than the hydrogen peroxide system at most time points, especially in the 1.0 h to 2.0 h range. This demonstrates that under FeOx / MnOx catalysis, the sulfate radicals generated by persulfate have stronger stability and oxidative selectivity against SCCPs in the complex groundwater environment of PRB than the hydroxyl radicals generated by hydrogen peroxide. Considering both treatment efficiency and economic cost, the removal rate of the persulfate system approached saturation (97%) when the HRT reached 1.5 h. Therefore, in practical engineering applications, 1.5 h - 2.0 h is preferred as the optimal hydraulic retention time to ensure that the effluent fully meets the standards.

Claims

1. A method for in-situ generation of FeOx / MnOx from groundwater based on PRB to degrade organic halogenated pollutants, characterized in that, The oxidation method is carried out according to the following steps: Step S1: A PRB simulation column is constructed. The PRB simulation column is a cylindrical reaction column. The reaction column is filled from bottom to top with a bottom layer of quartz sand packing, an activated carbon-zeolite mixed packing layer and a top layer of quartz sand packing. The reaction column adopts a bottom-in, top-out upflow water inlet method. Step S2: Prepare simulated groundwater, wherein the simulated groundwater contains Fe 2+ Ions, Mn 2+ Ionic and short-chain chlorinated paraffins; Step S3: After mixing the simulated groundwater prepared in step S2 with the oxidant, the mixture is pumped into the PRB simulation column constructed in step S1 to simulate Fe in the groundwater. 2+ Ions and Mn 2+ Under the induction of an oxidant, ions generate an in-situ FeOx / MnOx composite catalytic layer on the surface of an activated carbon-zeolite mixed packing material, and the FeOx / MnOx composite catalytic layer degrades short-chain chlorinated paraffins; Step S4: The concentration of short-chain chlorinated paraffins at each sampling port and outlet of the PRB simulation column was monitored, and the concentration was adjusted by changing the hydraulic retention time, oxidant dosage, or Fe. 2+ Ions and Mn 2+ The ion ratio is adjusted to maintain a degradation efficiency of 90-100%.

2. The method for in-situ generation of FeOx / MnOx from groundwater based on PRB to degrade organic halogenated pollutants, as described in claim 1, is characterized in that... The height of the PRB simulation column mentioned in step S1 is 50~100 cm and the inner diameter is 2~10 cm; a sampling port is set on the side wall of the PRB simulation column every 10~15 cm.

3. The method for in-situ generation of FeOx / MnOx from groundwater based on PRB to degrade organic halogenated pollutants, as described in claim 1, is characterized in that... The thickness of the bottom and top quartz sand filler layers in step S1 is 5-10 cm, and the particle size of the quartz sand is 1-2 mm. The thickness of the activated carbon-zeolite mixed filler layer is 40-80 cm, the mass ratio of activated carbon to zeolite is (1-3):1, the particle size of activated carbon is 20-40 mesh, and the particle size of zeolite is 3-4 mm.

4. The method for in-situ generation of FeOx / MnOx from groundwater based on PRB to degrade organic halogenated pollutants, as described in claim 1, is characterized in that... Fe in simulated groundwater described in step S2 2+ The mass concentration of ions is 2~4 mg / L, Mn 2+ The mass concentration of the ions was 2–4 mg / L, and the initial mass concentration of the short-chain chlorinated paraffins was 150–500 μg / L.

5. The method for in-situ generation of FeOx / MnOx from groundwater based on PRB to degrade organic halogenated pollutants, as described in claim 1 or 4, is characterized in that... The Fe 2+ Ions and Mn 2+ The molar ratio of the ions is (1~5):(1~5).

6. The method for in-situ generation of FeOx / MnOx from groundwater based on PRB to degrade organic halogenated pollutants, as described in claim 1, is characterized in that... The oxidant mentioned in step S3 is one or more of potassium persulfate, sodium persulfate, hydrogen peroxide, potassium persulfate monohydrogen phosphate, potassium permanganate, and ozone.

7. The method for in-situ generation of FeOx / MnOx from groundwater based on PRB to degrade organic halogenated pollutants, as described in claim 1, is characterized in that... The hydraulic residence time of the simulated groundwater in the PRB simulation column mentioned in step S3 is 1~2 hours.

8. The method for in-situ generation of FeOx / MnOx from groundwater based on PRB to degrade organic halogenated pollutants, as described in claim 1, is characterized in that... The simulated groundwater described in step S3 has a pH value of 6.0~8.0 and a temperature of 10~20℃.

9. The method for in-situ generation of FeOx / MnOx from groundwater based on PRB to degrade organic halogenated pollutants, as described in claim 1, is characterized in that... The simulated groundwater mentioned in step S3 also contains coexisting interfering ions, namely Cl. - HCO3 - and NO3 - At least one of them.

10. The method for in-situ generation of FeOx / MnOx from groundwater based on PRB to degrade organic halogenated pollutants, as described in claim 9, is characterized in that... The concentration of Cl⁻ is 0.05~0.2 mmol / L, the concentration of HCO₃⁻ is 1~6 mmol / L, and the concentration of NO₃⁻ is 0.05~0.15 mmol / L.

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