Method for degrading nitrobenzene pollutants by humus-synergistic enhanced Fenton system

Abstract

The invention relates to a method for degrading nitrobenzene pollutants by using a humus-synergistic enhanced Fenton system, which comprises the following steps: adding a peroxide oxidant, a Fe (III) catalyst and a water-soluble organic reducing agent with Fe (III) reducing capacity into soil containing nitrobenzene pollutants, uniformly mixing to form a Fenton system, adding humus, and uniformly mixing to form the nitrobenzene pollutants. Mixing and reacting to obtain the soil for degrading the nitrobenzene pollutants. Compared with the existing Fenton technology, the method has the advantages that the overall catalytic efficiency can be improved, the initial pH does not need to be adjusted, and the method is green, safe and environmentally friendly.

Description

Technical Field

[0001] The present invention relates to the technical field of contaminated soil remediation, and particularly to a method for degrading nitrobenzene pollutants by an enhanced Fenton system synergized with humus. Background Technique

[0002] In recent years, with the development of industries such as fine chemicals and explosive manufacturing, nitrobenzene compounds (such as nitrobenzene, nitrotoluene, and nitrochlorobenzene) are widely used in industrial activities. Their high toxicity, persistence, and environmental mobility make them typical site organic pollutants. These pollutants can migrate with water bodies and can also enter the human body through skin absorption, posing a serious threat to human health and have been listed as key regulatory targets in many countries.

[0003] Currently, the soil remediation methods for nitrobenzene pollutants mainly include soil vapor extraction, thermal desorption, bioremediation, and chemical oxidation. Among them, advanced oxidation technology can directly break the molecular structure of pollutants by generating strong oxidizing species such as hydroxyl radicals (·OH), which has significant advantages. The traditional H2O2 / Fe(II) Fenton system is highly efficient but only effective under strong acidic conditions, and Fe(III) is prone to precipitation and passivation. Therefore, a water-soluble organic reducing agent (such as ascorbic acid) is introduced to reduce Fe(III) to Fe(II), forming an Fe(III)-organic reducing agent-hydrogen peroxide system to enhance the reaction persistence and free radical yield. This type of Fenton system has good adaptability under a wide pH range, but its overall catalytic efficiency still needs to be improved.

[0004] Patent publication number CN103624074A discloses a method for deep degradation of high-concentration chloronitrobenzene pollutants in soil by combining the solubilization of a mixed surfactant and Fenton oxidation. The method of using a surfactant for solubilization can relatively economically remove high-concentration organic pollution, and the subsequent Fenton oxidation can further optimize the pollution removal effect. However, the amount of surfactant and hydrogen peroxide used is large, the cost is high; multiple steps are required to separate the solution, and the operation is cumbersome; it is only applicable to acidic conditions, and a large amount of acid solution needs to be used to adjust for alkaline environments. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for degrading nitrobenzene pollutants by an enhanced Fenton system synergized with humus to overcome the defect of low overall catalytic efficiency existing in the above-mentioned prior art, and to achieve the improvement of the overall catalytic efficiency.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] A method for degrading nitrobenzene pollutants by a humus-assisted enhanced Fenton system, comprising the following steps: adding a peroxide oxidant, an Fe(III) catalyst, and a water-soluble organic reducing agent with the ability to reduce Fe(III) to the soil containing nitrobenzene pollutants, mixing evenly to form a Fenton system, and then adding humus, mixing and stirring for reaction to obtain the soil with degraded nitrobenzene pollutants.

[0008] Further, the nitrobenzene pollutants include nitrobenzene (NB), p-nitrotoluene (p-NT), and p-nitrochlorobenzene (p-NCB).

[0009] Further, the concentration of nitrobenzene pollutants in the soil is 10-100 mg / kg, preferably 30-80 mg / kg.

[0010] Further, the peroxide oxidant includes hydrogen peroxide solution, potassium persulfate solution, sodium persulfate solution, or peracetic acid solution;

[0011] The concentration of the peroxide oxidant is 1-10 mmol / L, preferably 2.5-4.5 mmol / L.

[0012] Further, the Fe(III) catalyst is a soluble ferric salt solution, including ferric chloride solution, ferric nitrate solution, ferric sulfate solution, ferric perchlorate solution, ammonium ferric citrate solution, ferric citrate solution, and ammonium ferric oxalate solution;

[0013] The concentration of the soluble ferric salt solution is 0.1-5 mmol / L, preferably 1-3 mmol / L.

[0014] Further, the water-soluble organic reducing agent is a natural organic acid, including ascorbic acid, oxalic acid, tartaric acid, and citric acid, preferably ascorbic acid;

[0015] The concentration of the water-soluble organic reducing agent is 0.1-5 mmol / L, preferably 1-3 mmol / L.

[0016] Further, the humus includes humic acid (HA), biomass fulvic acid (FAS), or mineral fulvic acid (FAK).

[0017] Further, the concentration ratio of the peroxide oxidant, the Fe(III) catalyst, and the water-soluble organic reducing agent is 1-5:1:1-5;

[0018] The mass ratio of the sum of the peroxide oxidant, the Fe(III) catalyst, and the water-soluble organic reducing agent to the dry soil mass of the soil containing nitrobenzene pollutants is 0.5-10:1, preferably 1-5:1.

[0019] Further, the mass ratio of the humus to the soil containing nitrobenzene pollutants is 0.1 - 1:100, preferably 0.1 - 0.9:100. When the humus is in excess, the improvement of its pollutant removal efficiency is limited.

[0020] Further, the manner of the mixed reaction includes stirring or shaking, the rotation speed is 100 - 400 rpm, preferably 200 - 300 rpm; the time is 1 - 5 h, preferably 1 - 3 h.

[0021] Further, post-treatment is carried out on the soil for degrading nitrobenzene pollutants. The specific process is as follows: after the mixed reaction is completed, standing is carried out to achieve solid-liquid separation, obtaining the supernatant and the separated soil. The supernatant is discharged, and the pH of the separated soil is adjusted.

[0022] Furthermore, the soil particles and precipitates such as iron mud are naturally settled by standing to achieve solid-liquid separation.

[0023] Furthermore, the separated iron mud can be treated by the following methods: ① Adopt the neutralization precipitation method, add alkaline agents to adjust the pH to 8.0 - 10.0, so that the residual Fe 2+ / Fe 3+ generates hydroxide precipitation and then is separated by pressure filtration; ② Through high-temperature calcination (400 - 600 °C), an iron-based catalyst is prepared for recycling.

[0024] Furthermore, the supernatant is discharged by means of siphon or pumping, collected and detected for treatment to ensure up-to-standard discharge.

[0025] Furthermore, the pH of the separated soil is adjusted to the neutral range to meet the requirements of subsequent soil reuse or disposal.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] (1) The Fenton system constructed by the present invention significantly promotes the Fe(Ⅲ) / Fe(Ⅱ) cycle by introducing a water-soluble organic reducing agent (such as ascorbic acid) with the ability to reduce Fe(Ⅲ), can continuously generate hydroxyl radicals under neutral pH conditions, improve the utilization rate of free radicals, and achieve the efficient degradation of nitrobenzene pollutants.

[0028] (2) The present invention first introduces humus materials into the Fenton system as a synergistic intensifier, effectively improving the free radical generation rate and the system stability. The degradation rates of nitrobenzene, p-nitrotoluene and p-nitrochlorobenzene can be respectively increased to 90% - 100%, 80% - 96%, 78% - 91% in 120 minutes. Humus is a class of natural highly active organic macromolecules, rich in functional groups such as phenolic hydroxyl groups and quinone groups, with electron transfer and complexation functions. Its introduction helps to promote the Fe(Ⅲ) reduction cycle, improve the degradation rate and buffer the interference of the matrix in the soil.

[0029] (3) The water-soluble organic reducing agents selected in the present invention are all natural organic acids, including ascorbic acid, oxalic acid, tartaric acid, citric acid, etc. Compared with traditional chelating reducing agents such as EDTA, they do not produce toxic by-products and are green, safe and environmentally friendly reducing agents.

[0030] (4) The method provided by the invention has strong adaptability and can maintain a stable degradation effect under various conditions such as different water-soil ratios and coexisting anions, showing good engineering applicability and anti-interference ability.

[0031] (5) The mineralization rate of the method provided by the present invention reaches 45% - 47%, the toxicity of the degradation products is significantly reduced, and the overall treatment process is green, environmentally friendly, safe and controllable, suitable for in-situ soil remediation.

[0032] (6) The enhanced Fenton system synergized by humus in the present invention has significant advantages: humus has low cost and is naturally degradable, greatly reducing the reagent cost and environmental risk; the one-step method is simple to operate and does not require a complex separation process, making it more suitable for in-situ remediation; the reaction proceeds under neutral pH conditions without additional acid-base adjustment. Description of the Drawings

[0033] Figure 1 It is the effect diagram of the degradation of nitrobenzene compounds in soil for Examples 1 - 5, Comparative Examples 1 and 2;

[0034] Figure 2 It is the effect diagram of the degradation of nitrobenzene compounds in soil for Examples 6 - 10, Comparative Examples 1 and 3;

[0035] Figure 3 It is the effect diagram of the degradation of nitrobenzene compounds in soil for Examples 11 - 15, Comparative Examples 1 and 4. Detailed Embodiments

[0036] The present invention will be described in detail below with reference to the drawings and specific embodiments. These embodiments are implemented on the premise of the technical solution of the present invention, and detailed implementation manners and specific operation processes are given. However, the protection scope of the present invention is not limited to the following embodiments. Based on the given embodiments, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope protected by this application.

[0037] Unless otherwise specified, the reagents, methods, instruments and equipment used in the present invention are conventional reagents, methods, instruments and equipment in the art.

[0038] In the following examples, the soil used was uncontaminated garden soil collected from the farmland area around Lvgang Ecological Village in Chongming District; nitrobenzene (NB), p-nitrotoluene (p-NT), and p-nitrochlorobenzene (p-NCB) were all chemical reagents purchased from J&K Scientific Ltd., with an analytical purity grade; the Fe(III) catalyst and ascorbic acid were both anhydrous ferric chloride purchased from Sinopharm Chemical Reagent Co., Ltd., with an analytical purity grade; mineral fulvic acid and biomass fulvic acid were both purchased from Beijing Bowen Shennong Technology Co., Ltd., with purities of ≥85% and ≥95% respectively; the humic acid was an artificial humic acid chemical reagent purchased from Shanghai Macklin Biochemical Co., Ltd., with a purity of ≥90%.

[0039] A method for degrading nitrobenzene pollutants by a humus-assisted enhanced Fenton system, comprising the following steps: adding a peroxide oxidant, an Fe(III) catalyst, and a water-soluble organic reducing agent with Fe(III) reducing ability to soil containing nitrobenzene pollutants, mixing evenly to form a Fenton system, and then adding humus, mixing and stirring for reaction to obtain soil with degraded nitrobenzene pollutants.

[0040] In some specific embodiments, the nitrobenzene pollutants include NB, p-NT, and p-NCB.

[0041] In some specific embodiments, the concentration of nitrobenzene pollutants in the soil is 10 - 100 mg / kg, preferably 30 - 80 mg / kg.

[0042] In some specific embodiments, the peroxide oxidant includes hydrogen peroxide solution, potassium persulfate solution, sodium persulfate solution, or peracetic acid solution;

[0043] The concentration of the peroxide oxidant is 1 - 10 mmol / L, preferably 2.5 - 4.5 mmol / L.

[0044] In some specific embodiments, the Fe(III) catalyst is a soluble ferric salt solution, including ferric chloride solution, ferric nitrate solution, ferric sulfate solution, ferric perchlorate solution, ammonium ferric citrate solution, ferric citrate solution, ammonium ferric oxalate solution;

[0045] The concentration of the soluble ferric salt solution is 0.1 - 5 mmol / L, preferably 1 - 3 mmol / L.

[0046] In some specific embodiments, the water-soluble organic reducing agent is a natural organic acid, including ascorbic acid, oxalic acid, tartaric acid, citric acid, preferably ascorbic acid;

[0047] The concentration of the water-soluble organic reducing agent is 0.1 - 5 mmol / L, preferably 1 - 3 mmol / L.

[0048] In some specific embodiments, the humic substance comprises humic acid (HA), biomass fulvic acid (FAS) or mineral fulvic acid (FAK).

[0049] In some specific embodiments, the concentration ratio of the peroxide oxidant, the Fe(III) catalyst, and the water-soluble organic reducing agent is 1-5:1:1-5;

[0050] The ratio of the sum of the mass of the peroxide oxidant, the Fe(III) catalyst and the water-soluble organic reducing agent to the dry mass of the soil containing nitrobenzene pollutants is 0.5 to 10:1, preferably 1 to 5:1.

[0051] In some specific embodiments, the mass ratio of the humus to the soil containing nitrobenzene pollutants is 0.1 to 1:100, preferably 0.1 to 0.9:100. When the humus is excessive, the improvement in pollutant removal efficiency is limited.

[0052] In some specific embodiments, the mixing reaction comprises stirring or shaking at a rotation speed of 100 to 400 rpm, preferably 200 to 300 rpm; and for 1 to 5 hours, preferably 1 to 3 hours.

[0053] In some specific embodiments, the soil for degrading nitrobenzene pollutants is post-treated, and the specific process is as follows: after the mixing reaction is completed, the soil is allowed to stand to achieve solid-liquid separation to obtain a supernatant and separated soil, the supernatant is discharged, and the pH of the separated soil is adjusted.

[0054] In some specific embodiments, the solid-liquid separation is achieved by allowing the soil particles and sediments such as iron mud to settle naturally by standing still.

[0055] In some specific embodiments, the separated iron mud can be treated by the following methods: ① using the neutralization precipitation method, adding alkaline reagent to adjust the pH to 8.0-10.0, so that the residual Fe 2+ / Fe 3+ ② The generated hydroxide precipitate is separated by filtration; ② The iron-based catalyst is prepared by high-temperature calcination (400-600°C) for recycling.

[0056] In some specific embodiments, the supernatant is discharged by siphoning or pumping, and is collected, tested, and processed to ensure that it meets the discharge standards.

[0057] In some specific embodiments, the pH of the separated soil is adjusted to a neutral range to meet the requirements of subsequent soil reuse or disposal.

[0058] The above embodiments may be implemented individually or in groups of two or more.

[0059] The following is described in conjunction with specific embodiments.

[0060] Example 1

[0061] A method for degrading nitrobenzene pollutants in soil by a mineral fulvic acid synergistic Fe(Ⅲ)-ascorbic acid-hydrogen peroxide system (AA-Fenton system) includes the following steps:

[0062] Place 10 g of contaminated soil in a 50 mL centrifuge tube, where the concentrations of NB, p-NT, and p-NCB in the contaminated soil are 82.50 mg / kg, 67.88 mg / kg, and 67.88 mg / kg, respectively. Mix hydrogen peroxide solution, ferric chloride solution, and ascorbic acid to obtain 20 mL of a mixed reaction solution, where the hydrogen peroxide concentration is 3 mmol / L, the ferric chloride concentration is 1 mmol / L, and the ascorbic acid concentration is 3 mmol / L. Add the mixed reaction solution to the centrifuge tube to form an AA-Fenton system.

[0063] Add 10 mg of mineral fulvic acid to the centrifuge tube and mix well under the action of a reciprocating shaker. The reaction temperature is room temperature (about 25 °C), and the initial pH value of the reaction system is 6.45. After reacting for 120 minutes, add 4.0 mL of methanol to terminate the reaction, and then centrifuge at 8000 rpm for 10 minutes. After centrifugation, extract the pollutants in the soil sample by the accelerated solvent extraction method and the pollutants in the supernatant by the automatic solid-phase extraction method. Determine the concentration of pollutants in the total extract by gas chromatography-mass spectrometry, calculate the concentration of pollutants according to the pre-drawn standard curve, and calculate the removal rate of pollutants at each reaction time by comparing the concentration changes of pollutants before and after the reaction. The results are shown in Figure 1 and Table 1.

[0064] Example 2

[0065] Compared with Example 1, most of them are the same, except that the mass of the added mineral fulvic acid is adjusted to 30 mg, and the results of the pollutant removal rate are shown in Figure 1 and Table 1.

[0066] Example 3

[0067] Compared with Example 1, most of them are the same, except that the mass of the added mineral fulvic acid is adjusted to 50 mg, and the results of the pollutant removal rate are shown in Figure 1 and Table 1.

[0068] Example 4

[0069] Compared with Example 1, most of them are the same, except that the mass of the added mineral fulvic acid is adjusted to 70 mg, and the results of the pollutant removal rate are shown in Figure 1 and Table 1.

[0070] Example 5

[0071] Compared with Example 1, most of them are the same, except that the mass of the added mineral fulvic acid is adjusted to 90 mg, and the pollutant removal rate results are shown in Figure 1 and Table 1.

[0072] Example 6

[0073] A method for degrading nitrobenzene pollutants in soil by a biomass fulvic acid synergistic AA-Fenton system. Compared with Example 1, most of them are the same, except that the mineral fulvic acid is replaced by biomass fulvic acid, and the pollutant removal rate results are shown in Figure 2 and Table 1.

[0074] Example 7

[0075] A method for degrading nitrobenzene pollutants in soil by a biomass fulvic acid synergistic AA-Fenton system. Compared with Example 2, most of them are the same, except that the mineral fulvic acid is replaced by biomass fulvic acid, and the pollutant removal rate results are shown in Figure 2 and Table 1.

[0076] Example 8

[0077] A method for degrading nitrobenzene pollutants in soil by a biomass fulvic acid synergistic AA-Fenton system. Compared with Example 3, most of them are the same, except that the mineral fulvic acid is replaced by biomass fulvic acid, and the pollutant removal rate results are shown in Figure 2 and Table 1.

[0078] Example 9

[0079] A method for degrading nitrobenzene pollutants in soil by a biomass fulvic acid synergistic AA-Fenton system. Compared with Example 4, most of them are the same, except that the mineral fulvic acid is replaced by biomass fulvic acid, and the pollutant removal rate results are shown in Figure 2 and Table 1.

[0080] Example 10

[0081] A method for degrading nitrobenzene pollutants in soil by a biomass fulvic acid synergistic AA-Fenton system. Compared with Example 5, most of them are the same, except that the mineral fulvic acid is replaced by biomass fulvic acid, and the pollutant removal rate results are shown in Figure 2 and Table 1.

[0082] Example 11

[0083] A method for degrading nitrobenzene pollutants in soil by a humic acid synergistic AA-Fenton system is mostly the same as that in Example 1, except that the mineral fulvic acid is replaced by humic acid. The pollutant removal rate results are shown in Figure 3 and Table 1.

[0084] Example 12

[0085] A method for degrading nitrobenzene pollutants in soil by a humic acid synergistic AA-Fenton system is mostly the same as that in Example 2, except that the mineral fulvic acid is replaced by humic acid. The pollutant removal rate results are shown in Figure 3 and Table 1.

[0086] Example 13

[0087] A method for degrading nitrobenzene pollutants in soil by a humic acid synergistic AA-Fenton system is mostly the same as that in Example 3, except that the mineral fulvic acid is replaced by humic acid. The pollutant removal rate results are shown in Figure 3 and Table 1.

[0088] Example 14

[0089] A method for degrading nitrobenzene pollutants in soil by a humic acid synergistic AA-Fenton system is mostly the same as that in Example 4, except that the mineral fulvic acid is replaced by humic acid. The pollutant removal rate results are shown in Figure 3 and Table 1.

[0090] Example 15

[0091] A method for degrading nitrobenzene pollutants in soil by a humic acid synergistic AA-Fenton system is mostly the same as that in Example 5, except that the mineral fulvic acid is replaced by humic acid. The pollutant removal rate results are shown in Figure 3 and Table 1.

[0092] Comparative Example 1

[0093] Compared with Example 1, it is mostly the same, except that no mineral fulvic acid is added, and only the AA-Fenton system is used to degrade nitrobenzene pollutants in soil. Specifically:

[0094] In a 50 mL centrifuge tube, 10 g of contaminated soil was placed. The concentrations of NB, p-NT, and p-NCB in the contaminated soil were 82.50 mg / kg, 67.88 mg / kg, and 67.88 mg / kg, respectively. Hydrogen peroxide solution, ferric chloride solution, and ascorbic acid were mixed to obtain 20 mL of a mixed reaction solution, where the hydrogen peroxide concentration was 3 mmol / L, the ferric chloride concentration was 1 mmol / L, and the ascorbic acid concentration was 3 mmol / L. The mixed reaction solution was added to the centrifuge tube to form an AA-Fenton system. It was thoroughly mixed evenly under the action of a reciprocating shaker. The reaction temperature was room temperature (about 25 °C), and the initial pH value of the reaction system was 6.5. After reacting for 120 minutes, 4.0 mL of methanol was added to terminate the reaction, and then it was centrifuged at 8000 rpm for 10 minutes. After centrifugation, the pollutants in the soil sample were extracted by the accelerated solvent extraction method, the pollutants in the supernatant were extracted by the automatic solid-phase extraction method, the concentration of the pollutants in the total extract was determined by gas chromatography-mass spectrometry, the concentration of the pollutants was calculated according to the pre-drawn standard curve, and the removal rate of the pollutants at each reaction time was calculated by comparing the concentration changes of the pollutants before and after the reaction. The results are shown in Figures 1 - 3 and Table 1.

[0095] Comparative Example 2

[0096] Compared with Example 5, hydrogen peroxide solution, ferric chloride solution, and ascorbic acid were not added, and only mineral fulvic acid with the same concentration was added. Specifically:

[0097] In a 50 mL centrifuge tube, 10 g of contaminated soil was placed. The concentrations of NB, p-NT, and p-NCB in the contaminated soil were 82.50 mg / kg, 67.88 mg / kg, and 67.88 mg / kg, respectively. 10 mg of mineral fulvic acid was added to the centrifuge tube and thoroughly mixed evenly under the action of a reciprocating shaker. The reaction temperature was room temperature (about 25 °C), and the initial pH value of the reaction system was 6.75. After reacting for 120 minutes, 4.0 mL of methanol was added to terminate the reaction, and then it was centrifuged at 8000 rpm for 10 minutes. After centrifugation, the pollutants in the soil sample were extracted by the accelerated solvent extraction method, the pollutants in the supernatant were extracted by the automatic solid-phase extraction method, the concentration of the pollutants in the total extract was determined by gas chromatography-mass spectrometry, the concentration of the pollutants was calculated according to the pre-drawn standard curve, and the removal rate of the pollutants at each reaction time was calculated by comparing the concentration changes of the pollutants before and after the reaction. The results are shown in Figure 1 and Table 1.

[0098] Comparative Example 3

[0099] Compared with Comparative Example 2, most of them were the same, except that the mineral fulvic acid was replaced by biomass fulvic acid. The removal rate results are shown in Figure 2 and Table 1.

[0100] Comparative Example 4

[0101] Compared with Comparative Example 2, most of them are the same, except that the mineral fulvic acid is replaced by humic acid. The removal rate results are shown in Figure 3 and Table 1.

[0102] Table 1 shows the degradation rates of nitrobenzene compounds in the degraded soil of Examples 1 to 15 and Comparative Examples 1 to 4

[0103]

[0104] Figure 1 and Table 1 indicate that when only mineral fulvic acid is added, only slight degradation occurs for the three nitrobenzene pollutants. Considering that mineral fulvic acid itself has certain adsorption properties, it can have a slight adsorption effect on pollutants, but the adsorption amount is limited. After introducing mineral fulvic acid into the AA-Fenton system, the degradation rates of the three nitrobenzene pollutants are significantly increased. When the addition amount of mineral fulvic acid is 90 mg (0.9%), the degradation rates of NB, p-NT, and p-NCB can reach 98.13%, 90.67%, and 87.68% within 120 minutes. This result proves that adding mineral fulvic acid can effectively enhance the degradation of nitrobenzene in soil by the AA-Fenton system.

[0105] Figure 2 and Table 1 indicate that when only biomass fulvic acid is added, only slight degradation occurs for the three nitrobenzene pollutants. Considering that mineral fulvic acid itself has certain adsorption properties, it can have a slight adsorption effect on pollutants, but the adsorption amount is limited. After introducing biomass fulvic acid into the AA-Fenton system, the degradation rates of the three nitrobenzene pollutants are significantly increased; when the addition amount of biomass fulvic acid is 90 mg (0.9%), the degradation rates of NB, p-NT, and p-NCB can reach 99.42%, 94.14%, and 88.68% within 120 minutes. This result proves that adding biomass fulvic acid can effectively enhance the degradation of nitrobenzene in soil by the AA-Fenton system.

[0106] Figure 3 and Table 1 indicate that when only humic acid is added, only slight degradation occurs for the three nitrobenzene pollutants. Considering that commercial humic acid itself has certain adsorption properties, it can have a slight adsorption effect on pollutants, but the adsorption amount is limited. After introducing commercial humic acid into the AA-Fenton system, the degradation rates of the three nitrobenzene pollutants are significantly increased; when the addition amount of commercial humic acid is 90 mg (0.9%), the degradation rates of NB, p-NT, and p-NCB can reach 100%, 95.69%, and 90.17% within 120 minutes. This result proves that adding humic acid can effectively enhance the degradation of nitrobenzene in soil by the AA-Fenton system.

[0107] In summary, the present invention provides a method for degrading nitrobenzene pollutants by a humus-assisted enhanced Fenton system. Compared with the existing nitrobenzene pollutant removal technologies, this method is simple to operate, highly efficient in reaction, green and harmless, has a good degradation effect on nitrobenzene pollutants, and has a wide application range.

[0108] Although the present invention has been described in detail with general descriptions, specific embodiments and experiments in the above text, some modifications or improvements can be made based on the present invention, which are obvious to those skilled in the art. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection required by the present invention.

Claims

1. A method for degrading nitrobenzene pollutants by a humus-assisted enhanced Fenton system, characterized in that, It includes the following steps: Add peroxide oxidant, Fe(Ⅲ) catalyst and water-soluble organic reducing agent with Fe(Ⅲ) reducing ability into the soil containing nitrobenzene pollutants, mix evenly to form a Fenton system, and then add humus, and mix and react to obtain the soil with degraded nitrobenzene pollutants.

2. The method for degrading nitrobenzene pollutants by a humus-assisted enhanced Fenton system according to claim 1, characterized in that, The nitrobenzene pollutants described include nitrobenzene, p-nitrotoluene, and p-nitrochlorobenzene; The concentration of nitrobenzene pollutants in the soil is 10 - 100 mg / kg.

3. A method for degrading nitrobenzene pollutants by a humus-assisted enhanced Fenton system according to claim 1, characterized in that, The peroxide oxidant described includes hydrogen peroxide solution, potassium persulfate solution, sodium persulfate solution, or peracetic acid solution; The concentration of the peroxide oxidant is 1 - 10 mmol / L.

4. A method for degrading nitrobenzene pollutants by a humus-assisted enhanced Fenton system according to claim 1, characterized in that, The Fe(Ⅲ) catalyst is a soluble ferric salt solution, including ferric chloride solution, ferric nitrate solution, ferric sulfate solution, ferric perchlorate solution, ammonium ferric citrate solution, ferric citrate solution, ammonium ferric oxalate solution; The concentration of the soluble ferric salt solution is 0.1 - 5 mmol / L.

5. A method for degrading nitrobenzene pollutants by a humus-assisted enhanced Fenton system according to claim 1, characterized in that The water-soluble organic reducing agent is a natural organic acid, including ascorbic acid, oxalic acid, tartaric acid, citric acid; The concentration of the water-soluble organic reducing agent is 0.1 - 5 mmol / L.

6. A method for degrading nitrobenzene pollutants by a humus-assisted enhanced Fenton system according to claim 1, characterized in that, The humus includes humic acid, biomass fulvic acid, or mineral fulvic acid.

7. A method for degrading nitrobenzene pollutants in a humus-assisted enhanced Fenton system according to claim 1, characterized in that, The concentration ratio of the peroxide oxidant, Fe(Ⅲ) catalyst, and water-soluble organic reducing agent is 1 - 5:1:1 - 5; The mass ratio of the sum of the masses of the peroxide oxidant, Fe(Ⅲ) catalyst, and water-soluble organic reducing agent to the dry soil mass of the soil containing nitrobenzene pollutants is 0.5 - 10:

1.

8. A method for degrading nitrobenzene pollutants by a humus-assisted enhanced Fenton system according to claim 1, characterized in that, The mass ratio of the humus to the soil containing nitrobenzene pollutants is 0.1 - 1:

100.

9. A method for degrading nitrobenzene pollutants in a humus-assisted enhanced Fenton system according to claim 1, characterized in that, The mixing reaction method includes stirring or shaking.

10. A method for degrading nitrobenzene pollutants by a humus-assisted enhanced Fenton system according to claim 1, characterized in that, Perform post-treatment on the soil with degraded nitrobenzene pollutants. The specific process is as follows: after the mixing reaction is completed, stand still to achieve solid-liquid separation to obtain the supernatant and the separated soil, drain the supernatant, and adjust the pH of the separated soil.

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