Remediation method for high chlorinated organic matter contaminated soil based on Brij-35 thermal activation sodium persulfate system

Abstract

The invention discloses a remediation method for high chlorinated organic matter contaminated soil based on a Brij-35 thermal activation sodium persulfate system, and relates to the technical field of soil remediation. The invention aims to solve the problems of low remediation efficiency and incomplete degradation of high-chlorinated organic pollutants in polluted soil due to the characteristics of difficult oxidative degradation and easy reductive dechlorination of the traditional high-chlorinated organic pollutants. According to the thermal activation sodium persulfate system based on Brij-35, generation and conversion of free radicals are accurately regulated and controlled by utilizing the distribution state of soil oxygen under the natural background, and efficient remediation of DDT contaminated soil is achieved. The method not only improves the degradation efficiency of DDT, but also widens the technical path of remediation of the soil polluted by the high chlorinated organic compounds, and brings a new hope for the fields of environmental protection and soil pollution treatment. The remediation method for the high chlorinated organic matter contaminated soil based on the Brij-35 thermal activation sodium persulfate system can be obtained.

Description

Technical Field

[0001] The invention relates to the technical field of soil remediation, and in particular to a method for remediating soil contaminated with high-chlorinated organic matter based on a Brij-35 thermally activated sodium persulfate system. Background Art

[0002] Organochlorine pesticides (OCPs) are a class of persistent organic pollutants (POPs) with the characteristics of strong toxicity, difficulty in degradation, and easy bioaccumulation. After World War II, OCPs were widely used in agricultural production due to their low cost and high efficiency. While bringing huge economic benefits to mankind, they also inevitably released a large amount of toxic organic pollutants into the environment, seriously threatening human health and the ecological environment. DDT is a common OCP. Since 1940, DDT has been widely used worldwide to control agricultural pests and vector-borne diseases. However, previous studies have found that DDT and its metabolites can cause chronic effects on the nervous system, liver, kidneys, and immune system, and are also persistent, bioaccumulative, and have long-range migration. Therefore, many Western countries banned their use in 1970. However, due to the long half-life of DDT, DDT can still be detected in environmental media such as soil around the world.

[0003] The remediation of DDT-contaminated soil can be achieved through physical remediation technology (physical means such as adsorption, thermal desorption, and electrokinetics). This technology aims to separate and transfer DDT and cannot effectively reduce its biological toxicity. Chemical remediation technology (cleaning, oxidation, and reduction) gradually mineralizes the target organic pollutants into CO2, H2O, and inorganic matter. In addition, biological remediation technology (microbial remediation and phytoremediation) mainly performs in situ remediation of contaminated sites, but the remediation speed is slow and is not widely used.

[0004] In contrast, in-situ chemical oxidation (ISCO) based on sodium persulfate (PS) has gradually become a research hotspot in the field of remediation of chlorinated organic pollutants, and thermal activation is an ideal method for oxidizing soil organic matter. However, the current thermally activated PS (thermal / PS) technology mainly faces bottleneck problems such as slow degradation rate, low efficiency and narrow application range when degrading highly chlorinated organic pollutants. This is because the SO4 generated during the thermal activation of PS ·- and · Oxidative free radicals (OFRs) such as OH are electrophilic free radicals that tend to attack groups with high electron density. However, due to the electron-withdrawing effect of Cl atoms, the C-Cl bonds of highly chlorinated organic pollutants lack electrons and are easily attacked by reducing free radicals with nucleophilic effects. This makes it difficult for highly chlorinated organic pollutants to be effectively removed by thermally activated PS technology, which seriously limits the application of ISCO technology in the remediation of highly chlorinated organic pollutants in soil. Summary of the invention

[0005] The purpose of the present invention is to solve the problem of low remediation efficiency and incomplete degradation of highly chlorinated organic pollutants in contaminated soil due to the characteristics of traditional highly chlorinated organic pollutants that are difficult to oxidize and degrade but easy to reduce and dechlorinate, and to provide a remediation method for highly chlorinated organic pollutants contaminated soil based on a Brij-35 thermally activated sodium persulfate system.

[0006] A method for remediating soil contaminated with highly chlorinated organic matter based on a Brij-35 thermally activated sodium persulfate system is carried out in the following steps:

[0007] First, DDT-contaminated soil is added to a reaction container, and then purified deionized water, Brij-35 and sodium persulfate are added to obtain a mixture a, wherein the mass ratio of Brij-35 to sodium persulfate is (0.09-0.11) g: (149-151) mg; then the mixture a is placed on a constant temperature water bath shaker, and the mixture is shaken for reaction at a temperature of 49-51° C. for 11.9-12.1 hours to complete the remediation of the soil contaminated with high chlorinated organic matter based on the Brij-35 thermally activated sodium persulfate system;

[0008] The above specific reaction equation is as follows:

[0009]

[0010] C 11 H 23- CH2(OCH2CH2) 23- OH+ · OH→R · +H2O (7)

[0011]

[0012] R · +O2→ROO · (9)

[0013] ROO · +C 11 H 23- CH2(OCH2CH2) 23- OH→R · +RO2H (10)

[0014] 2ROO · →R-O4-R→products (11)

[0015] DDT+R · →DDD / DDE+Cl - (12)

[0016]

[0017] Beneficial effects of the present invention:

[0018] The present invention provides a system for generating reducing free radicals based on dodecyl polyglycol ether (Brij-35), which is used for effectively repairing soil contaminated by DDT. The heat-activated persulfate advanced oxidation system can generate oxidative free radicals (such as sulfate free radicals), which can attack the active hydrogen sites of Brij-35 to generate reducing free radicals. Under anaerobic conditions, in the initial stage of the reaction, when Brij-35 is present, the reducing free radicals dominate the reduction dechlorination process of DDT, generating intermediates such as DDD (dichlorodiphenylethylene) and DDE (dichlorodiphenylethylene). Then, as Brij-35 is consumed, the remaining oxidative free radicals in the system begin to dominate and act on these dechlorination intermediates, further converting them into harmless substances through oxidative degradation pathways, thereby achieving complete mineralization of DDT. In actual soil, deep soil lacks oxygen, and the role of reducing free radicals is fully exerted, effectively promoting the reduction dechlorination of DDT. At the same time, due to the presence of oxygen in the shallow soil, the reducing free radicals are quenched by oxygen and the reduction of DDT is inhibited, but this characteristic contributes to the accumulation of oxidative free radicals and enhances the further degradation and harmlessness of the dechlorination products of DDT.

[0019] The Brij-35-based heat-activated sodium persulfate system proposed in the present invention achieves efficient remediation of DDT-contaminated soil by precisely regulating the generation and conversion of free radicals by utilizing the distribution state of soil oxygen under natural background. This method not only improves the degradation efficiency of DDT, but also broadens the technical path for remediation of soil contaminated by highly chlorinated organic matter, bringing new hope to the fields of environmental protection and soil pollution control.

[0020] The invention can obtain a method for repairing soil contaminated by high-chlorinated organic matter based on a Brij-35 thermally activated sodium persulfate system. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The graph shows the effect of different concentrations of Brij-35 on the degradation of DDT in the heat / PS system as the reaction time changes. Indicates degraded DDT, represents DDT in the water phase, It indicates DDT in the earth phase;

[0022] Figure 2 The figure shows the effect of different concentrations of Cr(VI) on the degradation of DDT in the heat / PS / Brij-35 system under anaerobic conditions. ■ represents PS / Brij-35, ● represents PS / Brij-35 / Cr 6+ (1mM), ▲ indicates PS / Brij-35 / Cr6+ (5mM), ▼ indicates PS / Brij-35 / Cr 6+ (10mM), ◆ indicates PS / Brij-35 / Cr 6+ (50 mM);

[0023] Figure 3 It represents the effect of different concentrations of tert-butanol on the degradation of DDT in the heat / PS / Brij-35 system under anaerobic conditions, ■ represents PS / Brij-35, ● represents PS / Brij-35 / tert-butanol (100 mM), ▲ represents PS / Brij-35 / tert-butanol (200 mM), ▼ represents PS / Brij-35 / tert-butanol (500 mM), ◆ represents PS / Brij-35 / tert-butanol (1 M);

[0024] Figure 4 It represents the effect of different concentrations of phenol on the degradation of DDT in the heat / PS / Brij-35 system under anaerobic conditions, ■ represents PS / Brij-35, ● represents PS / Brij-35 / phenol (1mM), ▲ represents PS / Brij-35 / phenol (5mM), ▼ represents PS / Brij-35 / phenol (10mM), ◆ represents PS / Brij-35 / phenol (20mM);

[0025] Figure 5 It shows the effect of different concentrations of p-benzoquinone (PBQ) on the degradation of DDT in the heat / PS / Brij-35 anaerobic system under anaerobic conditions;

[0026] Figure 6 It represents the EPR spectra of free radical generation in the heat / PS system, heat / PS / Brij-35 / DDT and heat / PS / Brij-35 system under anaerobic conditions. a represents PS / Brij-35 / DDT, b represents PS / Brij-35, c represents PS, ★ represents DMPO-R, ◆ represents DMPO-OH, Indicates DMPO-

[0027] Figure 7 Indicates the heat / PS system, heat / PS / Brij-35 system and heat / PS / Brij-35 / DDT system under anaerobic conditions. 1 The EPR spectrum generated by O2, Indicates TEMP- 1 O2;

[0028] Figure 8It represents the decomposition effect of different concentrations of p-benzoquinone (PBQ) on PS under anaerobic conditions, ■ represents PS / Brij-35, ● represents PS / Brij-35 / PBQ (100mM), ▲ represents PS / Brij-35 / PBQ (200mM), ▼ represents PS / Brij-35 / PBQ (500mM);

[0029] Fig. 9 It represents the degradation effect of DDT under different oxygen conditions, ■ represents PS aerobic, ● represents PS anaerobic, ▲ represents PS / Brij-35 aerobic, ▼ represents PS / Brij-35 anaerobic;

[0030] Fig.10 The graph represents the change of solution pH value under aerobic and anaerobic conditions during the degradation of DDT. ■ represents PS aerobic, ● represents PS anaerobic, ▲ represents PS / Brij-35 aerobic, and ▼ represents PS / Brij-35 anaerobic;

[0031] Fig.11 It represents the trend of dissolved oxygen concentration change of heat / PS and Brij-35 / heat / PS system under aerobic and anaerobic conditions. ■ represents PS aerobic, ● represents PS anaerobic, ▲ represents PS / Brij-35 aerobic, ▼ represents PS / Brij-35 anaerobic;

[0032] Fig.12 It represents the decomposition diagram of Brij-35 in the Brij-35 / heat / PS system under aerobic and anaerobic conditions. ■ represents Brij-35 / DDT aerobic, ● represents Brij-35 / DDT anaerobic, ▲ represents Brij-35 / PS / DDT aerobic; ▼ represents Brij-35 / PS / DDT anaerobic, ◆ represents Brij-35 / PS anaerobic;

[0033] Fig.13 Process diagram showing the decomposition of Brij-35;

[0034] Fig.14 It represents the EPR spectra of representative substances of type D alcohol in the thermal / PS system, where ★ represents DMPO-R;

[0035] Fig.15 The EPR spectra of representative substances of type J alcohols in the thermal / PS system, where ★ represents DMPO-R;

[0036] Fig.16 Represents the chemical structural formulas of trichloroethylene, carbon tetrachloride, hexachloroethane and chlordane;

[0037] Fig.17 The degradation performance diagram of the heat / PS / Brij-35 system for trichloroethylene, carbon tetrachloride, hexachloroethane and chlordane is shown in Figure 2. Represents the oxidation process, represents the reduction-oxidation process, Indicates the restoration process;

[0038] Fig.18 represents the structural formula of 2-butoxyethanol (BE), diethylene glycol ethyl ether (DE), JFC-2 and Brij-35;

[0039] Fig.19 It represents the degradation performance of different surfactants on hexachloroethane (HCA) in heat / PS system, ■ represents HCA, ● represents PS / BE / HCA, ▲ represents PS / DE / HCA, ▼ represents PS / JFC-2 / HCA, ◆ represents PS / Bij-35 / HCA;

[0040] Fig. 20 Indicates k obs with [OE] 总数 Correlation fitting diagram of ;

[0041] Fig.21 Represents the EPR spectra of free radical generation of different surfactants in the heat / PS system, ★ represents DMPO-R. DETAILED DESCRIPTION

[0042] Specific implementation method 1: This implementation method is a method for remediating soil contaminated with high chlorinated organic matter based on a Brij-35 thermally activated sodium persulfate system, which is carried out in the following steps:

[0043] First, DDT-contaminated soil is added to a reaction container, and then purified deionized water, Brij-35 and sodium persulfate are added to obtain a mixture a, wherein the mass ratio of Brij-35 to sodium persulfate is (0.09-0.11) g: (149-151) mg; then the mixture a is placed on a constant temperature water bath shaker, and the mixture is shaken for reaction at a temperature of 49-51° C. for 11.9-12.1 hours to complete the remediation of the soil contaminated with high chlorinated organic matter based on the Brij-35 thermally activated sodium persulfate system;

[0044] The above specific reaction equation is as follows:

[0045]

[0046]

[0047] C 11 H 23- CH2(OCH2CH2) 23- OH+ · OH→R · +H2O (7)

[0048]

[0049] R · +O2→ROO · (9)

[0050] ROO · +C 11 H 23- CH2(OCH2CH2) 23- OH→R · +RO2H (10)

[0051] 2ROO · →R-O4-R→products (11)

[0052] DDT+R · →DDD / DDE+Cl - (12)

[0053]

[0054] Specific embodiment 2: The difference between this embodiment and specific embodiment 1 is that the ratio of the mass of the DDT-contaminated soil, the volume of the purified deionized water, the mass of Brij-35 and the mass of sodium persulfate is (0.49-0.51) g: (4.9-5.1) mL: (0.09-0.11) g: (149-151) mg.

[0055] The other steps are the same as those in the first specific implementation.

[0056] Specific implementation method three: The difference between this implementation method and specific implementation method one or two is that the mass of the DDT-contaminated soil, the volume of the purified deionized water, the mass of Brij-35 and the mass of sodium persulfate are 0.5g:5mL:0.1g:150mg.

[0057] The other steps are the same as those in the first or second embodiment.

[0058] Specific implementation method 4: The difference between this implementation method and specific implementation methods 1 to 3 is that the concentration of DDT in the DDT-contaminated soil is 9.99-10.01 mg / kg.

[0059] The other steps are the same as those in Specific Embodiments 1 to 3.

[0060] Specific implementation method five: This implementation method is different from specific implementation methods one to four in that the amount of the Brij-35 substance is 0.0829 to 0.0831 mmoL.

[0061] The other steps are the same as those in Specific Embodiments 1 to 4.

[0062] Specific implementation method six: The difference between this implementation method and specific implementation methods one to five is that the concentration of DDT in the DDT-contaminated soil is 10 mg / kg, and the amount of the Brij-35 substance is 0.083 mmoL.

[0063] The other steps are the same as those in Specific Embodiments 1 to 5.

[0064] Specific implementation method 7: The difference between this implementation method and specific implementation methods 1 to 6 is that the purified deionized water is obtained by purifying deionized water with nitrogen for 30 to 60 minutes.

[0065] The other steps are the same as those in Specific Embodiments 1 to 6.

[0066] Specific embodiment eight: This embodiment differs from specific embodiments one to seven in that: the reaction container is a centrifuge tube with a volume of 50 mL and a screw cap.

[0067] The other steps are the same as those in Specific Embodiments 1 to 7.

[0068] Specific embodiment 9: The difference between this embodiment and specific embodiments 1 to 8 is that the gas in the reaction container is nitrogen.

[0069] The other steps are the same as those in Specific Embodiments 1 to 8.

[0070] Specific embodiment 10: The difference between this embodiment and specific embodiments 1 to 9 is that the rotation speed of the constant temperature water bath shaker is 195-205 rpm.

[0071] The other steps are the same as those in Specific Embodiments 1 to 9.

[0072] The following examples are used to verify the beneficial effects of the present invention:

[0073] Example 1: Based on the mass distribution diagram of the Brij-35 / heat / PS system degrading DDT in contaminated soil, the changes in the phase state of DDT are observed and the solubilization and degradation effects of Brij-35 are further understood, including the following steps:

[0074] First, the DDT-contaminated soil was fully ground and passed through a 100-mesh sieve, and then collected for later use. Weigh 0.5g of DDT-contaminated soil sample and 150mg of PS in a 50mL screw-cap centrifuge tube, then add 5mL of Brij-35 aqueous solution of the corresponding concentration, and at the same time. The centrifuge tube was placed in a water bath constant temperature oscillator at 50℃ and 200rpm, taken out after 12h, immediately quenched in an ice bath, and then placed in a low-temperature high-speed centrifuge for centrifugation at 4℃, 8000rpm, and 5min. The DDT content in the supernatant and soil was then detected by gas chromatograph. For anaerobic environment, the deionized water used was purified by nitrogen for 30min before being added to the system. Anaerobic environment means that the deionized water used in the experiment is deoxygenated water after passing nitrogen for 30min, and the anaerobic experiment is performed in a vacuum glove box throughout the process.

[0075] Figure 1 The graph shows the effect of different concentrations of Brij-35 on the degradation of DDT in the heat / PS system as the reaction time changes. Indicates degraded DDT, represents DDT in the water phase, Indicates DDT in the soil phase; Figure 1 As shown, in the presence of 1.7 mmol / L of Brij-35, 55.70% of DDT was not dissolved and only 44.30% of DDT was degraded. The addition of Brij-35 significantly increased the water solubility of DDT, and the optimal concentration of Brij-35 was 16.6 mmol / L, and the degradation rate of DDT reached 91.97%.

[0076] Example 2: Potassium dichromate, tert-butyl alcohol (TBA) and phenol were selected as quenchers to explore the role of sulfate radicals in the generation of reducing free radicals, and the formation of reducing free radicals was identified using electron paramagnetic resonance (EPR). The specific operation includes the following steps:

[0077] A mixed solution of 10 mg / L DDT, 100 mmol / L PS and 8.3 mmol / L Brij-35 was prepared in a 40 mL brown bottle as the initial reaction system. Then, different concentrations of Cr 6+(1, 5, 10 and 50mmol / L), phenol (1, 5, 10 and 20mmol / L), tert-butyl alcohol (100, 200, 500mmol / L and 1mol / L), p-benzoquinone (100, 200 and 500mmol / L) were used to quench the active oxygen species in the Brij-35 / heat / PS system, and p-benzoquinone (100, 200, 500mmol / L) was used to decompose PS. The deionized water used in the experiment was deoxygenated water after nitrogen was blown for 30 minutes. At the same time, a system containing 10mg / LDDT and 100mmol / L PS was set as the control group, and the DDT degradation efficiency was compared with the system with 8.3mmol / LBrij-35 added. The two systems were set up in aerobic and anaerobic environments respectively. The difference in the specific operation was that the deionized water used in the anaerobic environment was deoxygenated water after nitrogen stripping for 30 minutes, and the experiment was carried out in a vacuum glove box throughout the process. The parameters of the water bath thermostat oscillator were set to a speed of 200 rpm and a reaction temperature of 50° C. Samples were taken at certain time intervals (0, 5, 15, 30, 60, 90, 120 min) and placed in 0° C ice water to stop the reaction. The concentration of DDT in the sample was determined by gas chromatography.

[0078] Figure 2 The figure shows the effect of different concentrations of Cr(VI) on the degradation of DDT in the heat / PS / Brij-35 system under anaerobic conditions. ■ represents PS / Brij-35, ● represents PS / Brij-35 / Cr 6+ (1mM), ▲ indicates PS / Brij-35 / Cr 6+ (5mM), ▼ indicates PS / Brij-35 / Cr 6+ (10mM), ◆ indicates PS / Brij-35 / Cr 6+ (50 mM); Figure 3 It represents the effect of different concentrations of tert-butanol on the degradation of DDT in the heat / PS / Brij-35 system under anaerobic conditions, ■ represents PS / Brij-35, ● represents PS / Brij-35 / tert-butanol (100 mM), ▲ represents PS / Brij-35 / tert-butanol (200 mM), ▼ represents PS / Brij-35 / tert-butanol (500 mM), ◆ represents PS / Brij-35 / tert-butanol (1 M); Figure 4 It represents the effect of different concentrations of phenol on the degradation of DDT in the heat / PS / Brij-35 system under anaerobic conditions, ■ represents PS / Brij-35, ● represents PS / Brij-35 / phenol (1mM), ▲ represents PS / Brij-35 / phenol (5mM), ▼ represents PS / Brij-35 / phenol (10mM), ◆ represents PS / Brij-35 / phenol (20mM); Figure 5The graph shows the effect of different concentrations of p-benzoquinone (PBQ) on the degradation of DDT in the heat / PS / Brij-35 anaerobic system; Figure 6 It represents the EPR spectra of free radical generation in the heat / PS system, heat / PS / Brij-35 / DDT and heat / PS / Brij-35 system under anaerobic conditions. a represents PS / Brij-35 / DDT, b represents PS / Brij-35, c represents PS, ★ represents DMPO-R, ◆ represents DMPO-OH, Indicates DMPO- Figure 7 Indicates the heat / PS system, heat / PS / Brij-35 system and heat / PS / Brij-35 / DDT system under anaerobic conditions. 1 The EPR spectrum generated by O2, Indicates TEMP- 1 O2; Figure 8 The figure shows the decomposition effect of different concentrations of p-benzoquinone (PBQ) on PS under anaerobic conditions. ■ represents PS / Brij-35, ● represents PS / Brij-35 / PBQ (100 mM), ▲ represents PS / Brij-35 / PBQ (200 mM), and ▼ represents PS / Brij-35 / PBQ (500 mM).

[0079] like Figure 2 As shown, the results show that when Cr is added to the Brij-35 / heat / PS system 6+ When the concentrations were 1, 5, 10 and 50 mM, the degradation rate of DDT decreased from 100% to 27.65%, 11.53%, 0.46% and 0.50%, respectively, which proved the generation of RFRs in the Brij-35 / heat / PS system. When the concentrations of phenol added were 1, 5, 10 and 20 mM, the degradation rate of DDT within 120 min decreased by 85.63%, 90.09%, 92.85% and 93.84%, respectively. In addition, when 100, 200, 500 mM and 1 M tert-butyl alcohol (TBA) were added to the system, the degradation rate of DDT decreased by 2.90%, 4.30%, 17.04% and 66.70%, respectively. The formation and types of reducing free radicals in the heat / PS / Brij-35 system were further identified using EPR technology (such as Figure 6 As shown), it was found that during the thermal activation of PS, DMPO- and DMPO- · The OH signal is dominant, while after adding Brij-35 to the system, DMPO- and DMPO- ·The OH signal disappears and is replaced by another signal peak with a characteristic intensity of 1:1:1:1:1:1. By comparing the hyperfine splitting constants of the signal peak (g = 2.00589, α N =15.01G,α H =23.48G), which was found to be within the range of alkyl radicals (α N 15-17G, α H 21-24G), it is inferred that the signal peak should be DMPO-R · When 100, 200, and 500 mM PBQ were added to the Brij-35 / heat / PS system (e.g. Figure 5 It was found that the degradation rate of DDT decreased significantly from 100% to 7.78%, 5.94%, and 0.70% within 120 minutes, which seems to indicate that It plays a big role in the degradation of DDT. Figure 6 No signal peak belonging to DMPO-OOH was observed in the EPR spectrum of The content in the Brij-35 / heat / PS system is extremely weak. In order to explore the reasons why the degradation of DDT is greatly inhibited after the addition of PBQ, this study discusses the effect of PBQ on the decomposition rate of PS (e.g. Figure 8 As the concentration of PBQ added to the system increased from 0 to 500 mM, the decomposition rate of PS gradually decreased from 29.49% to 10.11% within 120 min. This indicates that the inhibitory effect of PBQ on DDT is likely because PBQ inhibits the decomposition of PS, resulting in a decrease in the production of reactive oxygen species, which makes it impossible to effectively degrade DDT. The principle is that PBQ accepts The product of R · It also has reducing electrons, so PBQ may compete with DDT for R generated in the Brij-35 / heat / PS system. · , resulting in the inhibition of DDT degradation. Another possibility is that After being generated in the system, it may be transformed into 1 O2 (Formulas 2-1 to 2-5), so DMPO is not captured signal peak.

[0080]

[0081] Example 3: The effect of oxygen (O2) on the generation of free radicals in the heat / PS and Brij-35 / heat / PS systems was studied. The heat / PS (aerobic), heat / PS (anaerobic), Brij-35 / heat / PS (aerobic) and Brij-35 / heat / PS (anaerobic) systems were selected to explore the removal of DDT within 120 min to infer R · The operation steps are the same as those in the above embodiment 2.

[0082] Fig. 9 It represents the degradation effect of DDT under different oxygen conditions. ■ represents PS aerobic, ● represents PS anaerobic, ▲ represents PS / Brij-35 aerobic, ▼ represents PS / Brij-35 anaerobic; Fig. 9 As shown in the figure, the heat / PS (aerobic), heat / PS (anaerobic), Brij-35 / heat / PS (aerobic) and Brij-35 / heat / PS (anaerobic) systems degraded 48.52%, 56.81%, 59.88% and 100% of DDT within 120 min, respectively. This indicates that anaerobic conditions extend the life of RFRs, thus facilitating the reduction and degradation of DDT.

[0083] In the anaerobic system of heat-activated PS, in addition to and · OH, Too and · OH reacts with PS ions through a single electron transfer process to produce an important active substance. Under anaerobic conditions, the free radical chain reaction involved in PS is shown in formulas 1 to 4, resulting in the consumption of PS; however, when O2 is present, will be quenched by O2 (Formula 5), ​​resulting in the termination of the free radical chain reaction, thereby inhibiting the further decomposition of PS. Therefore, the heat / PS (anaerobic) system is more conducive to the heat / PS (aerobic) system. In the Brij-35 / heat / PS system, the heat-activated PS generates and · OH will react with Brij-35 to form R · , as shown in formulas 6 to 7. PS ions can be further · Decompose into (Formula 8), which triggers a series of free radical chain reactions. Through the cycle of these free radical chain reactions, PS is decomposed in large quantities. However, when in an O2 environment, R · It will react with O2 to generate peroxyalkyl free radicals (ROO · ), and ROO · Ability to further oxidize Brij-35 via hydrogen extraction to regenerate R· (Formulas 9 to 10). However, ROO · It is not stable by itself and will undergo self-quenching reaction to generate other products (Formula 11); and because ROO · The redox potential of (E0 = 2.5-3.1V) and · OH (E0 = 2.8 V) is low, resulting in a hydrogen abstraction reaction with Brij-35 to generate R · The reactivity of PS and its ability to oxidize and degrade pollutants are relatively weak, so in the Brij-35 / heat / PS system, the free radical chain reaction under aerobic conditions cannot effectively promote the decomposition of PS compared to that under anaerobic conditions.

[0084]

[0085] C 11 H 23- CH2(OCH2CH2) 23- OH+ · OH→R · +H2O (Formula 7)

[0086]

[0087] R · +O2→ROO · (Formula 9)

[0088] ROO · +C 11 H 23- CH2(OCH2CH2) 23- OH→R · +RO2H (Formula 10)

[0089] 2ROO · →R-O4-R→products (Formula 11);

[0090] In addition, this study also monitored the changes in solution pH under aerobic and anaerobic conditions during the reaction, because the free radical chain reaction will generate more H + . Fig.10 The graph shows the change of solution pH value under aerobic and anaerobic conditions during the degradation of DDT. ■ indicates PS aerobic, ● indicates PS anaerobic, ▲ indicates PS / Brij-35 aerobic, and ▼ indicates PS / Brij-35 anaerobic. Fig.10As shown in the figure, under aerobic and anaerobic conditions, the pH of the solutions of the heat / PS and Brij-35 / heat / PS systems decreased significantly, because the decomposition of PS usually reduces the pH of the reaction solution. Under aerobic conditions, the pH values ​​of the solutions of the heat / PS and Brij-35 / heat / PS systems changed by 0.37 and 0.43, respectively, after 120 minutes of reaction, which were lower than the ΔpH values ​​of the two systems under anaerobic conditions (0.86 and 1.44), respectively. This indicates that the free radical chain reaction under anaerobic conditions can better promote the decomposition of PS, and compared with the heat / PS system alone, the addition of Brij-35 will Hydrogen extraction occurs to produce more R that is beneficial to DDT degradation · .

[0091] At the same time, the dissolved oxygen concentrations of the heat / PS and Brij-35 / heat / PS systems under aerobic and anaerobic conditions were also measured. Fig.11 The figure shows the trend of dissolved oxygen concentration changes in the heat / PS and Brij-35 / heat / PS systems under aerobic and anaerobic conditions. ■ indicates PS aerobic, ● indicates PS anaerobic, ▲ indicates PS / Brij-35 aerobic, and ▼ indicates PS / Brij-35 anaerobic. The results are shown in Fig.11 As shown. In order to strictly control the anaerobic environment, the anaerobic experiment was conducted in a vacuum glove box throughout the experiment, and the initial dissolved oxygen concentration of the anaerobic system was controlled at about 0.02 mg / L. In the anaerobic environment, the dissolved oxygen concentration in both the heat / PS system and the Brij-35 / heat / PS system did not change significantly. However, in the aerobic environment, the dissolved oxygen concentration in the heat / PS system dropped from 6.66 to 4.20 mg / L after 120 minutes of reaction, which indicates that the system The dissolved oxygen is consumed, and 4 The molecule only consumes 1 molecule of O2 (Formula 5); while in the Brij 35 / heat / PS system, the dissolved oxygen concentration dropped significantly from 6.50 to 2.66 mg / L, indicating that R · is quenched by O2, and 1 molecule R · It can react with 1 molecule of O2 (Formula 9), which is why the Brij-35 / heat / PS (aerobic) system consumes more dissolved oxygen than the heat / PS (aerobic) system.

[0092] Moreover, the effect of O2 on the decomposition of Brij-35 in the Brij-35 / heat / PS system was also investigated. Fig.12The decomposition diagram of Brij-35 in the Brij-35 / heat / PS system under aerobic and anaerobic conditions is shown as follows: ■ indicates Brij-35 / DDT aerobic, ● indicates Brij-35 / DDT anaerobic, ▲ indicates Brij-35 / PS / DDT aerobic; ▼ indicates Brij-35 / PS / DDT anaerobic, ◆ indicates Brij-35 / PS anaerobic; Fig.12 As shown in the figure, under the reaction condition of 50℃, the Brij-35 / DDT system alone decomposed 7.63% and 6.14% of Brij-35 in aerobic and anaerobic environments, respectively. This is because Brij-35 decomposes under heat, but not into R · , but a necessary loss in a hot environment, and this loss is not affected by O2, but is affected by the properties of Brij-35 itself. However, when PS was added to the Brij-35 / DDT system, the decomposition rate of Brij-35 in an aerobic environment was 25.20% within 120 minutes, which indicates that Brij-35 and PS interacted to produce R; and Brij-35 in the anaerobic system decomposed to produce R · The phenomenon is more obvious. The decomposition rate of Brij-35 is 48.94% higher than that in aerobic environment, which reflects the effect of O2 on R · These conclusions are consistent with the previous experimental results. In addition, in order to explore the influence of DDT, this experiment set up a Brij-35 / PS (anaerobic) system without DDT as a control group. The results showed that the decomposition rates of Brij-35 in the Brij-35 / PS / DDT (anaerobic) system and the Brij-35 / PS (anaerobic) system were 74.14% and 74.99%, respectively, with a difference of only 0.85%. Therefore, it is believed that the presence of DDT is not the reason for the decomposition of Brij-35.

[0093] Example 4: The degradation and free radical transformation of alkyl OE ethers such as Brij-35 in the Brij-35 / heat / PS system were studied. The operation steps are as follows:

[0094] A mixed solution containing 20μM HCA, 100mM PS and 8.3mM alkyl OE ether (BE, DE, JFC-2 and Brij-35) was placed in a 40mL brown bottle. The deionized water used in the experiment was deoxygenated water after nitrogen was passed through for 30 minutes. The reaction was started in a water bath constant temperature oscillator, and the parameters were set to a speed of 200rpm and a reaction temperature of 50℃. Points were taken at certain time intervals (0, 5, 15, 30, 60, 90, 120min) and placed in ice water at 0℃ to stop the reaction. The concentration of HCA in the sample was determined by gas chromatograph, and GC-MS and EPR analysis were used for intermediate product and free radical identification.

[0095] LC-MS was used to gain a deeper understanding of the decomposition products of Brij-35 in the Brij-35 / heat / PS (anaerobic) system, and a total of 16 types of products were found, which are shown in Table 1. Where n represents the OE unit (-OCH2CH2-) and m represents the alkyl chain (-CH2CH2-). Fig.13 The process diagram of Brij-35 decomposition is shown; combined with the above Brij-35 products, its decomposition path in the Brij-35 / heat / PS (anaerobic) system is inferred, and the results are as follows Fig.13 As shown, it can be seen that the decomposition of Brij-35 is a process of loss of OE units. Brij-35 is composed of a dodecyl chain and 23 OE units, and the hydrogen atoms in the OE units are more unstable than the hydrogen atoms on the alkyl chain. and · OH is more likely to extract hydrogen atoms from the OE unit, and due to the different positions of the extracted hydrogen atoms, two configurations of R, A and B, are generated. · Among them, type A R · -OCH2CH · -structure, can produce C-type aldehydes (n is up to 16) and D-type alcohols (n is up to 13) with smaller OE chains through the cleavage of the CO bond, and then the aldehydes and alcohols undergo a condensation reaction to produce G-type polymers; and by attacking the CC bond on the alkyl chain of the G-type polymer and the CO bond in its OE unit to break it, and then through oxidation reaction and elimination reaction, type I aldehydes and type J alcohols are generated respectively, and the J-type alcohols have fewer OE units, with a maximum of only 10; the undecanal belonging to the I-type aldehyde can be oxidized to generate carboxylic acid (M), and the J-type alcohol can continue to undergo the alcohol elimination reaction and dehydrate to form the C=C double bond in the N-type substance.

[0096] Table 1: Intermediates of Brij-35 decomposition;

[0097]

[0098]

[0099] For type B R · For the reaction, it has -OCH · The CH2- structure can form E-type alcohols and F-type aldehydes through the cleavage of CO and CC bonds. The OE units in these two types of substances are relatively · The number of alcohols and aldehydes produced is even smaller, at most only 7 and 10 respectively; then the same polycondensation reaction occurs to produce H polymers, which are then and · The oxidation of OH produces K-type aldehydes and L-type substances, which are then gradually oxidized into O-type carboxylic acids and P-type substances.

[0100] Fig.14 It represents the EPR spectra of representative substances of type D alcohol in the thermal / PS system, where ★ represents DMPO-R; Fig.15 The EPR spectrum of representative substances of J-type alcohols in the heat / PS system, where ★ represents DMPO-R; Among the decomposition products of Brij-35 mentioned above, most of the products contain OE groups. This study uses EPR spectroscopy to verify whether such products can continue to react with Hydrogen abstraction reaction occurs to generate RFRs, and the results are as follows Figure 14-15 As shown. Fig.14 In the experiment, triethylene glycol (TEG) when n=3 and hexaethylene glycol (HEG) when n=6 in the D-type alcohol were added to the heat / PS system as typical representative products. DMPO was used to capture the free radicals after 10 minutes of reaction under anaerobic conditions. The results showed that the characteristic signal peaks belonging to were found, and the signal peak intensity increased with the increase of the number of OE units in the D-type alcohol. In addition, ethylene glycol monovinyl ether (VE) with 1 OE unit and diethylene glycol monovinyl ether (DVE) with 2 OE units were selected from the J-type alcohol and added to the heat / PS system ( Fig.15 ), it was found that the signal peak intensity in the DVE / PS system was greater than that in the VE / PS system. In summary, the OE group in the Brij-35 structure can be The hydrogen evolution reaction generates -OCH2CH · -or-OCH · CH2- two configurations of R · , its decomposition products with OE groups can still generate R · The ability and number of OE groups to generate R · There is a certain correlation between the strengths.

[0101] Example 5: Four common highly chlorinated compounds, such as trichloroethylene, carbon tetrachloride, hexachloroethane, and chlordane, were used as target pollutants to explore the universal applicability of the Brij-35 / heat / PS system in degrading different highly chlorinated compounds. The operating steps were the same as those in Example 2 above.

[0102] Fig.16 Represents the chemical structural formulas of trichloroethylene, carbon tetrachloride, hexachloroethane and chlordane; Fig.17 The degradation performance diagram of the heat / PS / Brij-35 system for trichloroethylene, carbon tetrachloride, hexachloroethane and chlordane is shown in Figure 2. Represents the oxidation process, represents the reduction-oxidation process, Indicates the restoration process; Figure 16-17As shown, the heat / PS (aerobic) system was used as the oxidation process. In this process, the degradation rates of trichloroethylene, carbon tetrachloride, hexachloroethane and chlordane in the soil within 12 hours were 36.11%, 19.13%, 22.98% and 37.23%, respectively, which indicates that the heat / PS (aerobic) system has limited degradation capacity for these highly chlorinated organics. When 16.6 mM Brij-35 was added to the heat / PS (anaerobic) system, a reduction-oxidation synergistic process was formed. After 12 hours of reaction in the system, trichloroethylene, carbon tetrachloride, hexachloroethane and chlordane in the soil were degraded by 97.99%, 92.60%, 67.74% and 79.81%, respectively, which indicates that R was generated in the system. · , and reduce and degrade these highly chlorinated organic compounds.

[0103] Example 6: To further determine the generation of R with oxyethylene (OE) groups in the heat / PS system · In this study, 2-butoxyethanol (BE) with 1 OE unit, diethylene glycol ethyl ether (DE) with 2 OE units, JFC-2 with 3.5 OE units, and Brij-35 with 23 OE units were used as alkyl OE ethers with different numbers of OE units. Their structural formulas are shown in Fig.18 The operation steps shown are the same as those in Example 2 above, except that quenching agents such as potassium dichromate and tert-butyl alcohol are not added. Fig.18 represents the structural formula of 2-butoxyethanol (BE), diethylene glycol ethyl ether (DE), JFC-2 and Brij-35;

[0104] In this study, these alkyl OE ethers were added to the heat / PS system at the same concentration (8.3 mM) to degrade HCA (20 uM). This is because HCA can act as a reducing free radical R · The same concentration can ensure that the molecular weight of each compound in the system is constant. The difference in the number of OE groups in the compound has a significant impact on the generation of R · The impact of quantity. Fig.19 It represents the degradation performance of different surfactants on hexachloroethane (HCA) in the heat / PS system, ■ represents HCA, ● represents PS / BE / HCA, ▲ represents PS / DE / HCA, ▼ represents PS / JFC-2 / HCA, ◆ represents PS / Bij-35 / HCA; the results are shown in Fig.19 As shown in Figure 2, after excluding the effect of HCA volatilization, BE / heat / PS, DE / heat / PS, JFC-2 / heat / PS and Brij-35 / heat / PS systems can degrade 14.74%, 44.14%, 84.03% and 99.32% of HCA within 120 min, respectively, and the corresponding k obs0.0019, 0.0051, 0.0215 and 0.0928 min respectively -1 (like Fig. 20 As shown in Figure 2.1, each OE unit has 4 unstable CH bonds, so the more OE units there are, the more alkyl OE ethers will be unstable. The higher the reactivity, the more hydrogen abstraction reaction occurs to form R · The potential is also greater. And The rate constant for the reaction with ethers generally increases with the number of unstable CH bonds near the oxygen atom, which explains the pseudo-first-order apparent rate constant ratio for the degradation of HCA in the alkyl OE ether / heat / PS system under the same conditions: Brij-35>JFC-2>DE>BE.

[0105] In addition, in order to accurately evaluate the number of OE groups in the generation of R · The role of OE groups in obs The relevance of the value. Fig. 20 Indicates k obs with [OE] 总数 The correlation fitting diagram of Fig. 20 As shown, the correlation coefficient R 2 The value is 0.9878, which is a significant positive correlation. At the same time, the above hypothesis is further verified by qualitatively and quantitatively analyzing the types and quantities of free radicals generated in the alkyl OE ether / heat / PS system through EPR spectroscopy. Fig.21 The EPR spectra of free radical generation of different surfactants in the heat / PS system, ★ represents DMPO-R; Fig.21 As shown in the figure, it can be found that the characteristic signal peaks belonging to DMPO-R appear in the BE / heat / PS, DE / heat / PS, JFC-2 / heat / PS and Brij-35 / heat / PS systems, and the intensity increases successively, indicating that R is generated in the above systems · The above experimental results all show that the OE group is the one that produces R · The active site mainly relies on the unstable CH bond near the oxygen atom in the group The more OE units in a single molecule, the more it can increase the generation of R · of production.

Claims

1. A method for remediating soil contaminated with highly chlorinated organic matter based on a Brij-35 thermally activated sodium persulfate system, characterized in that The repair method is carried out in the following steps: First, DDT-contaminated soil is added to a reaction container, and then purified deionized water, Brij-35 and sodium persulfate are added to obtain a mixture a, wherein the mass ratio of Brij-35 to sodium persulfate is (0.09-0.11) g: (149-151) mg; then the mixture a is placed on a constant temperature water bath shaker, and the mixture is shaken for reaction at a temperature of 49-51° C. for 11.9-12.1 hours to complete the remediation of the soil contaminated with high chlorinated organic matter based on the Brij-35 thermally activated sodium persulfate system; The above specific reaction equation is as follows: C 11 H 23- CH2(OCH2CH2) 23- OH+ · OH→R · +H2O (7) R · +O2→ROO · (9) ROO · +C 11 H 23- CH2(OCH2CH2) 23- OH→R · +RO2H (10) 2ROO · →R-O4-R→products (11) DDT+R · →DDD / DDE+Cl - (12) 2. The method for remediating soil contaminated with high chlorinated organic matter based on a Brij-35 thermally activated sodium persulfate system according to claim 1, characterized in that The ratio of the mass of the DDT-contaminated soil, the volume of the purified deionized water, the mass of Brij-35 and the mass of sodium persulfate is (0.49-0.51) g: (4.9-5.1) mL: (0.09-0.11) g: (149-151) mg.

3. A method for remediating soil contaminated with high chlorinated organic matter based on a Brij-35 thermally activated sodium persulfate system according to claim 1 or 2, characterized in that The ratio of the mass of the DDT-contaminated soil, the volume of the purified deionized water, the mass of Brij-35 and the mass of sodium persulfate is 0.5 g: 5 mL: 0.1 g: 150 mg.

4. A method for remediating soil contaminated with high chlorinated organic matter based on a Brij-35 thermally activated sodium persulfate system according to claim 2, characterized in that The concentration of DDT in the DDT-contaminated soil is 9.99-10.01 mg / kg.

5. The method for remediating soil contaminated with high chlorinated organic matter based on a Brij-35 thermally activated sodium persulfate system according to claim 2, characterized in that The amount of the Brij-35 substance is 0.0829-0.0831 mmoL.

6. A method for remediating soil contaminated with high chlorinated organic matter based on a Brij-35 thermally activated sodium persulfate system according to claim 4 or 5, characterized in that The concentration of DDT in the DDT-contaminated soil is 10 mg / kg, and the amount of the Brij-35 substance is 0.083 mmoL.

7. A method for remediating soil contaminated with high chlorinated organic matter based on a Brij-35 thermally activated sodium persulfate system according to claim 1 or 2, characterized in that The purified deionized water is obtained by purifying deionized water with nitrogen for 30 to 60 minutes.

8. The method for remediating soil contaminated with high chlorinated organic matter based on Brij-35 thermally activated sodium persulfate system according to claim 1, characterized in that The reaction container is a centrifuge tube with a volume of 50 mL and a screw cap.

9. A method for remediating soil contaminated with high chlorinated organic matter based on a Brij-35 thermally activated sodium persulfate system according to claim 8, characterized in that The gas in the reaction container is nitrogen.

10. The method for remediating soil contaminated with high chlorinated organic matter based on Brij-35 thermally activated sodium persulfate system according to claim 1, characterized in that The rotating speed of the constant temperature water bath shaker is 195-205 rpm.

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