CN115947442A

CN115947442A - Method for in-situ formation of dichlorine monoxide in high-chlorine water environment

Info

Publication number: CN115947442A
Application number: CN202211189766.XA
Authority: CN
Inventors: 凌力; 林川靖; 商启
Original assignee: Hong Kong University of Science and Technology HKUST
Current assignee: Hong Kong University of Science and Technology HKUST
Priority date: 2021-10-08
Filing date: 2022-09-28
Publication date: 2023-04-11

Abstract

The invention relates to a method for generating dichlorine monoxide in situ in a water environment and accurately controlling the concentration of the generated dichlorine monoxide, which comprises the following steps: 2 to 5mgCl into an aqueous environment ₂ Free chlorine is added at a dosage of/L, and HOCl and/or ClO are initiated in the water environment ^‑ Converting to dichlorine monoxide, wherein the aqueous environment has an initial chloride ion concentration of 0.1M or greater, wherein the free chlorine is selected from the group consisting of HOCl, clO ^‑ 、Cl ₂ 、Cl ₂ O and any combination thereof. The concentration of the generated dichlorine monoxide can be adjusted by adjusting the concentration of the free chlorineThe concentration of chloride ions, the pH value of the water environment, the type and concentration of non-chloride anions/cations contained in the water environment, wherein the pH value is 4.33-8.60, the non-chloride anions comprise carbonate, bicarbonate, phosphate, dihydrogen phosphate, monohydrogen phosphate, etc., and the cations comprise potassium ions, sodium ions, magnesium ions, etc.

Description

Method for in-situ formation of dichlorine monoxide in high-chlorine water environment

Technical Field

The invention relates to the field of preparation of dichlorine monoxide, in particular to a method for forming dichlorine monoxide in a high-chlorine water environment and accurately controlling the concentration of the generated dichlorine monoxide and application of the method to pollutant treatment.

Background

Free chlorine has been widely used as a disinfectant for drinking water treatment since the beginning of the 20 th century, but also as an oxidizing agent for municipal and industrial water treatment to remove color and degradable organic contaminants as well as taste and odor causing compounds. In the aqueous solution containing free chlorine, the free chlorine species is hypochlorous acid/hypochlorite (HOCl/ClO) ^- ) Molecular chlorine (Cl) ₂ ) And dichloro (Cl) ₂ O) is present. For drinking water, HOCl/ClO ^- Is the most abundant free chlorine species, and Cl ₂ And Cl ₂ O is a minor species. However, these two secondary species exhibit high reactivity to many organic contaminants, with a second order reaction rate constant that is higher than HOCl/ClO ^- The second order reaction rate constant of (2-7) orders of magnitude higher. Although Cl ₂ O is sometimes more reactive than Cl towards organic contaminants ₂ In the chlorination process, cl ₂ The contribution of O to contaminant degradation is often neglected.

Cl ₂ O gas was first discovered in 1834 and was identified as a pale orange-yellow gas that readily dissolves in and reacts with water. Cl ₂ O can react with saturated alkanes (e.g., 1-chlorobutane, 1-chloropropane, and n-butyronitrile) by free radical substitution to form chloroalkanes, can react with unsaturated alkenes (e.g., trichloroethylene) by addition reactions to produce carbonyl groups or ethers on the alkene, and can react with aromatics by side chain substitution or electrophilic substitution, depending on the functional group attached to the aromatic. Cl ₂ O is commonly used as an effective bleaching agent for wood pulp because it reacts with insoluble lignin in wood pulp through electrophilic chlorination, demethylation and oxidation processes.

High purity Cl ₂ O gas can be obtained by reacting Cl ₂ Gas is introduced into a heated inert solid support containing HgO, carbonate or phosphate (see equations 1-3 below):

2Cl ₂ +nHgO→HgCl ₂ ·Cl ₂ (n-1)HgO+Cl ₂ o reaction formula 1

2Cl ₂ +2Na ₂ CO ₃ +H ₂ O→Cl ₂ O+2NaHCO ₃ +2NaCl reaction scheme 2

2Cl ₂ +2Na ₃ PO ₄ +H ₂ O→Cl ₂ O+2Na ₂ HPO ₄ +2NaCl reaction scheme 3

Generated Cl ₂ Fast hydrolysis of O gas to HOCl, HOCl and Cl in water ₂ O forms an equilibrium relationship (see equation 4)

K ₁ ＝87M ^-1 Reaction formula 4

Thus, cl is formed in the field of water treatment ₂ One of the main strategies for O to degrade contaminants is to add high concentration of free chlorine in water (500-600. Mu.M at pH 4-9). The addition of such high concentrations of free chlorine in aqueous solution is not feasible in most cases because it adds significant chemical cost to the process and causes subsequent residual chlorine removal steps and potential safety issues during operation.

Cl has been reported in studies ₂ O pair degradation Ni (II) (CN) ₄ ^2- Contribution of (i.e. Cl) ₂ O formation) can be enhanced by increasing the chloride ion concentration from 1.3mM to 33mM in a solution buffered with acetic acid at a pH of about 5. Two other chlorine-containing reactive species, i.e. Cl ₂ And HOCl/ClO, on degradation of Ni (II) (CN) ₄ ^2- Is much less contributing due to the presence of Cl ₂ O compared with, they are on Ni (II) (CN) ₄ ^2- Much smaller reaction rate constants. Chlorine ion pair Cl ₂ The promotion of O formation cannot be used currently for Cl formation in water ₂ The knowledge of O explains that the equilibrium constant of equation 4 is used to calculate Cl in the presence of chloride ions ₂ The manner of O concentration needs to be re-evaluated. Nevertheless, based on reports, the inventors of the present application tried to form free chlorine at a high chloride ion concentration with a small concentration for fast reactionCl for fast degradation of organic pollutants ₂ And O. Through extensive research and experiments, the inventors propose a new mechanism of action to generate Cl in situ in a high-chlorine aqueous solution ₂ And O, the method can accurately control the concentration of generated dichloro oxide, thereby completing the invention.

Disclosure of Invention

In the mechanism proposed by the present invention, except for HOCl/ClO ^- In addition, chloride ion is an important reactant. This mechanism potentially opens up new ways of chlorination by adding a certain amount of free chlorine, which can be used to degrade organic contaminants in water containing high chloride ion concentrations of 0.1M or more, such as in sea water, brackish ground water, ballast water, landfill leachate and hydraulic fracturing wastewater. The mechanism proposed by the present invention may also exhibit Cl that is overlooked in the art ₂ The contribution of O to the degradation of contaminants. In addition, the method provided by the invention can also be used for Cl ₂ Any other field of O.

In one aspect of the present invention, there is provided a method for generating dichloro-carbon monoxide in situ in an aqueous environment, comprising: 2 to 5mgCl to the aqueous environment ₂ Free chlorine is added at a dosage of/L, and HOCl and/or ClO are initiated in the water environment ^- To generate dichlorine monoxide; wherein the aqueous environment has an initial chloride ion concentration of 0.1M or greater, and wherein the free chlorine is selected from the group consisting of HOCl, clO ^- 、Cl ₂ 、Cl ₂ O and any combination thereof.

In one embodiment, a chlorine-containing aqueous environment or a high chlorine-containing aqueous environment refers to water having a chloride ion concentration of 0.1M or greater. In preferred embodiments, the aqueous environment has an initial chloride ion concentration of 0.2-1.0M, for example, the initial chloride ion concentration can be 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, or 0.8M. In another embodiment, the free chlorine is an alkali metal hypochlorite or an alkaline earth metal hypochlorite, such as sodium hypochlorite and the like.

In one embodiment, the aqueous environment has a pH of 4 to 9, e.g., 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, or 9.0. If the initial pH of the aqueous environment does not meet the above-mentioned ranges, it can be adjusted with acids and/or hydroxides, for example before or at the same time as the addition of free chlorine. In this embodiment, the acid may be an acid commonly used in the art, such as hydrochloric acid, sulfuric acid, nitric acid, acetic acid, and the like, and the hydroxide may be an alkali metal hydroxide or an alkaline earth metal hydroxide, such as sodium hydroxide, potassium hydroxide, and the like. In further embodiments, the buffering may be performed with a solution comprising carbonate, bicarbonate, phosphate, dihydrogen phosphate, monohydrogen phosphate, and any combination thereof.

In one embodiment, the chloride ion concentration of the aqueous environment is adjusted to have a chloride ion concentration of 0.1M or greater prior to adding the free chlorine. For example, a salt containing chloride ions may be added to adjust the chloride ion concentration of the aqueous environment, such as ammonium chloride, sodium chloride, potassium chloride, magnesium chloride, and the like.

In one embodiment, the concentration of the generated dichlorine monoxide is determined by adjusting the concentration of free chlorine in the aqueous environment; the concentration of chloride ions, the pH of the aqueous environment, and the type and concentration of non-chloride anions and/or cations contained therein. In this embodiment, the chloride ion and pH may be in the ranges described above, for example, the chloride ion concentration may be from 0.2 to 1.0M, and the pH may be from 4 to 9, for example, from 4.33 to 8.60. In this embodiment, the non-chloride anion may comprise carbonate, bicarbonate, phosphate, dihydrogen phosphate, monohydrogen phosphate and at a concentration of 5mM or more, such as 10, 15, 20, 25 or 30mM, while the cation may comprise an alkali metal ion or an alkaline earth metal ion, such as potassium ion, sodium ion, magnesium ion, and at a concentration of 0.05-1M, such as 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1M.

In another aspect of the invention, there is provided a method of treating a pollutant in a chlorine-containing aqueous environment, comprising: 2 to 5mgCl to the aqueous environment ₂ Addition of free chlorine at a dosage of/L, initiation of HOCl and/or ClO in said aqueous environment ^- To generate dichlorine monoxide; reacting dichlorine monoxide with the contaminant, wherein the aqueous environment has an aqueous environment of greater than or equal toAn initial chloride ion concentration of 0.1M, and wherein the free chlorine is selected from HOCl, clO ^- 、Cl ₂ 、Cl ₂ O and any combination thereof

In another embodiment, the aqueous environment refers to water containing any chlorine-containing species, e.g., HOCl, clO ^- 、Cl ^- And the like. In a preferred embodiment, the chlorine-containing aqueous environment has an initial chloride ion concentration of 0.2-1.0M, for example, the initial chloride ion concentration may be 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, or 0.8M.

In one embodiment, the pH of the aqueous environment is between 4 and 9, e.g., 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, or 9.0. If the initial pH of the aqueous environment does not meet the above-mentioned ranges, it can be adjusted with acids and/or hydroxides, for example before or at the same time as the addition of free chlorine. In this embodiment, the acid may be an acid commonly used in the art, such as hydrochloric acid, sulfuric acid, nitric acid, acetic acid, and the like, and the hydroxide may be an alkali metal hydroxide or an alkaline earth metal hydroxide, such as sodium hydroxide, potassium hydroxide, and the like. In further embodiments, the buffering may be performed with a solution comprising carbonate, bicarbonate, phosphate, dihydrogen phosphate, monohydrogen phosphate, and any combination thereof.

In one embodiment, the concentration of the generated dichlorine monoxide is determined by adjusting the concentration of free chlorine in the aqueous environment; the aqueous environment can be controlled for chloride ion concentration, pH, type and concentration of non-chloride anions and/or cations contained therein. In this embodiment, the chloride ion and pH may be in the ranges described above, for example, the chloride ion concentration may be from 0.2 to 1.0M, and the pH may be from 4 to 9, for example, from 4.33 to 8.60. In this embodiment, the non-chloride anion may comprise carbonate, bicarbonate, phosphate, dihydrogen phosphate, monohydrogen phosphate and at a concentration of 5mM or more, such as 10, 15, 20, 25 or 30mM, and the cation may comprise an alkali metal ion or an alkaline earth metal ion, such as potassium ion, sodium ion, magnesium ion, and at a concentration of 0.05-1M, such as 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1M.

In one embodiment, the contaminant is an aromatic contaminant of the electron donating functional group. In further embodiments, the contaminant is an aromatic contaminant containing hydroxyl, amine, or methoxy groups. In yet another embodiment, the chlorine-containing aqueous environment is brackish groundwater, reverse osmosis brine, hydraulic fracturing wastewater, ballast water, or landfill leachate.

Drawings

The accompanying drawings, which are included to provide a further understanding and explanation of the inventive concepts, illustrate embodiments of the inventive concepts and together with the description serve to explain the principles of the inventive concepts. In the drawings:

FIG. 1 shows Cl formation from chloride ions and free chlorine in an aqueous solution containing chloride ions ₂ And the mechanism of O is shown schematically.

Fig. 2 shows the effect of chloride ion concentration on CBZ degradation, where (a) shows CBZ degradation kinetics as a function of chloride ion concentration; (b) Shows chlorine decay during CBZ chlorination at different chloride ion concentrations, conditions: [ free chlorine ]] ₀ ＝2mgCl ₂ /L,pH＝7.50，[CBZ] ₀ ＝5μM。

Figure 3 shows the kinetics of CBZ degradation at a sulfate concentration of 0.75M, conditions: [ free chlorine ]] ₀ ＝2mgCl ₂ /L,pH＝7.50，[CBZ] ₀ ＝5μM。

Figure 4 shows chlorine decay without CBZ, conditions: [ Cl ] ^- ]=1.00M, [ free chlorine ]] ₀ ＝2mgCl ₂ /L，pH＝7.50。

FIG. 5 shows the kinetics of CBZ degradation as a function of chloride ion concentration, with a free chlorine dose of 2 or 5mgCl ₂ L, condition: pH 7.50, [ CBZ] ₀ ＝5μM。

FIG. 6 shows (a) without additional chloride ion and at pH 4.40And CBZ degradation kinetics at 0.2M chloride ion and pH 7.50; (b) Chlorine decay during CBZ chlorination without additional chloride ion and at pH 4.40 and at 0.2M chloride ion and pH 7.50, conditions: [ free chlorine ]] ₀ ＝2mgCl ₂ /L，[CBZ] ₀ ＝5μM。

FIG. 7 shows the chlorine concentrations at 2 and 5mgCl ₂ At, [ Cl ] ^- ]And k _CBZ ' correlation between, conditions: [ CBZ] ₀ ＝5μM。

Figure 8 shows CBZ degradation at 0.10M sulfate concentration and pH 4.65, conditions: [ free chlorine ]] ₀ ＝2mgCl ₂ /L，[CBZ] ₀ ＝5μM。

Figure 9 shows CBZ degradation kinetics at different pH, conditions: [ Cl ] ^- ]=0.2M, [ free chlorine ]] ₀ ＝2mgCl ₂ /L，[CBZ] ₀ ＝5μM。

Figure 10 shows CBZ degradation kinetics under different buffer systems, conditions: [ Cl ] ^- ]=0.2M, [ free chlorine ]] ₀ ＝2mgCl ₂ /L，[CBZ] ₀ ＝5μM。

Figure 11 shows CBZ degradation kinetics when pH was adjusted using NaOH/HCl and phosphoric acid buffer systems, respectively, with the conditions: pH =7.50, [ Cl ^- ]=0.2M, [ free chlorine ]] ₀ ＝2mgCl ₂ /L，[CBZ] ₀ ＝5μM。

Figure 12 shows the degradation kinetics of CBZ under different cationic systems, conditions: [ Cl ] ^- ]=0.1M, [ free chlorine] ₀ ＝2mgCl ₂ /L，[CBZ] ₀ ＝5μM。

Fig. 13 shows (a) the kinetics of DMOB degradation as a function of chloride ion concentration, conditions: [ free chlorine ]] ₀ ＝2mgCl ₂ /L，pH＝7.50，[DMOB] ₀ =5 μ M; (b) BPA degradation kinetics without additional chloride ion at pH 7.50 and at 0.2M chloride ion at pH 7.50, conditions: [ free chlorine ]] ₀ ＝2mgCl ₂ /L，[BPA] ₀ =5 μ M; (c) BA degradation kinetics at 0.2M chloride and pH 7.50, conditions: [ free chlorine ]] ₀ ＝2mgCl ₂ /L，[BA] ₀ =5 μ M; (d) Kinetics of CBZ degradation in the Presence of 0.5, 1 and 2mgDOC/L NOMStudy, conditions: [ Cl ] ^- ]=1.0M, [ free chlorine ]] ₀ ＝5mgCl ₂ /L，[CBZ] ₀ ＝5μM。

Fig. 14 shows (a) chlorine decay in DMOB chlorination as a function of chloride ion concentration, conditions: [ free chlorine ]] ₀ ＝2mgCl ₂ /L，pH＝7.50，[DMOB] ₀ =5 μ M; (b) Chlorine decay in the chlorination of BPA without additional chloride ion and at pH 7.50 and at 0.2M chloride ion and pH 7.50, conditions: [ free chlorine ]] ₀ ＝2mgCl ₂ /L，[BPA] ₀ =5 μ M; (c) Chlorine decay in the chlorination of BA at 0.2M chloride ion and pH 7.50, conditions: [ free chlorine ]] ₀ ＝2mgCl ₂ /L，[BA] ₀ =5 μ M; (d) Chlorine decay in the chlorination of NOM in the absence of additional chloride ion or CBZ, at 1.00M chloride ion but no CBZ, and at 1.00M and 5 μ M chloride ion and CBZ, conditions: [ free chlorine ]] ₀ ＝5mgCl ₂ /L,pH＝7.50。

Figure 15 shows (a) DMOB degradation kinetics without additional chloride ion at pH 4.40 and at 0.75M chloride ion at pH 7.50, conditions: [ free chlorine ]] ₀ ＝5mgCl ₂ /L，[DMOB] ₀ =5 μ M; (b) Chlorine decay in DMOB chlorination without additional chloride ion and at pH 4.40 and at 0.75M chloride ion and pH 7.50, conditions: [ free chlorine ]] ₀ ＝5mgCl ₂ /L，[DMOB] ₀ =5 μ M; (c) degradation of DMOB in the presence of different HOBr concentrations, conditions: [ DMOB)] ₀ ＝5μM，pH＝7.50。

Figure 16 shows the morphology of phosphoric acid at different pH.

FIG. 17 shows the morphology of carbonic acid at different pH

Detailed Description

In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the various embodiments. However, various embodiments may be practiced without these specific details, or with one or more equivalent arrangements. Although the present invention has been described in further detail with reference to specific examples, the scope of the present invention is not limited thereto.

In the examples herein, free chlorine is added to a solution containing a high concentration of chloride ions to illustrate Cl ₂ Role of O in the degradation of micropollutants and chloride ion in Cl ₂ O forms a role in the mechanism. Carbamazepine (CBZ) was chosen as the model compound because it is a recalcitrant contaminant that is often detected in water sources. The following examples can be used to (1) study the effect of chloride ion concentration on the kinetics of CBZ degradation in chlorination reactions; (2) Differentiation of the contribution of different free chlorine species to CBZ degradation, thus confirming the new Cl ₂ The O formation mechanism; (3) Evaluation of Cl ₂ The ability of O to degrade CBZ at different pH values, different non-chloride anions, different cations and its reactivity towards different organic structures.

In this context, all processes, steps and operations are carried out at ambient temperature (22. + -. 2 ℃ C.) unless otherwise specified.

As used herein, the terms "high-chlorine water (environment)", "high-chlorine-containing water (environment)", and "high-chlorine-ion-containing water (environment)" refer to water (environment) having a chlorine ion concentration of 0.1M or more, and these terms are equally replaceable throughout.

In the examples herein, sodium hypochlorite (NaClO) solution (4.0-5.0%), sodium chloride (NaCl), sodium hydroxide (NaOH), sodium bromide (NaBr), sodium dihydrogen phosphate (Na) ₂ HPO ₄ ) Sodium hydrogen phosphate (NaH) ₂ PO ₄ ) Sodium carbonate (Na) ₂ CO ₃ ) Sodium bicarbonate (Na) ₂ HCO ₃ ) Sodium sulfate (Na) ₂ SO ₄ ) Carbamazepine (CBZ), 1,4-Dimethoxybenzene (DMOB), bisphenol A (BPA), benzoic Acid (BA), ascorbic acid (HC) ₆ H ₇ O ₆ ) Sulfuric acid (H) ₂ SO ₄ ) Phenylenediamine sulfate (DPD), ethylenediaminetetraacetic acid (EDTA) were purchased from Sigma-Aldrich, USA. Phosphoric acid (H) of HPLC grade ₃ PO ₄ ) And methanol were both purchased from Fisher Scientific, USA. All solutions were prepared by dissolving reagent grade chemicals in di-deionized water (DDI, 18.2 μm-cm) produced by a water purification system (Cascada, PALL Corporation). Suwannee River reverse osmosis Natural Organic Matter (NOM) isolate (Cat # 2R 101N) was purchased from IInternational Humic substructures Society. Stock solutions of NOM were prepared by adding the NOM isolate to DDI water, stirring overnight, then filtering through a 0.45 μm pore size fiber membrane (Whatman). A free chlorine stock solution was prepared by diluting NaClO solution (4.0-5.0%) with DDI water. Calibration of the concentration of free chlorine stock solution (2.60 gCl) ₂ L). All stock solutions prepared were stored at 4 ℃ in the dark and allowed to return to ambient temperature (22 ± 2 ℃) before use.

In the examples provided herein, the generalized operating steps are as follows. The degradation of the micropollutants was studied in a cylindrical glass reactor of 11cm diameter containing 250mL of aqueous solution. The reactor was placed on a magnetic plate. 250mL of aqueous solution was prepared by adding the indicated amounts of 1.00M NaCl and micropollutant stock solutions to DDI water to achieve different chloride ion concentrations of 0.05-1.00M and target micropollutant doses of 5 μ M, respectively. Passing 5mM phosphate buffer (by mixing different proportions of 0.20M Na) during CBZ chlorination ₂ HPO ₄ 0.20M NaH ₂ PO ₄ And 14.57M of H ₃ PO ₄ Preparation) the solution was buffered to pH 4.33, 5.50, 5.90, 6.44, 6.97 and 7.50. Then 2 or 5mgCl was achieved by adding the indicated volume of free chlorine stock solution to 250mL of aqueous solution ₂ Initial chlorine concentration,/L, was tested. Samples of 1.0mL were collected at predetermined time intervals, quenched with ascorbic acid at an ascorbic acid/initial chloride molar ratio of 1.5/1, and analyzed for residual micropollutant concentration. In parallel experiments, chlorine concentration was measured at predetermined time intervals.

Except that 5mM bicarbonate buffer (by mixing different ratios of 0.20M Na) was used separately ₂ CO ₃ And NaHCO ₃ Preparation) and dropwise addition of 200mM NaOH and 0.60M HCl (pH was continuously monitored by pH meter (ORION STAR Aiii) to buffer pH, the effect of carbonate and hydroxide on micropollutant degradation was examined in a similar manner as above. The effects of NOM and different organics with different structures (i.e. DMOB, BPA and BA) were also tested in a similar manner. All experiments were repeated at least once. All data figures represent the average of experimental data from duplicate test results. Use of Origin8.0 software statistical significance (p) was assessed by one-way analysis of variance (ANOVA)<0.05)。

The concentrations of CBZ, DMOB, BPA and BA were measured using high performance liquid chromatography (VP series, shimadzu) equipped with a Waters symmetry C18 column (4.6X 150mm,5 μm particle size). The wavelengths of the ultraviolet detectors were set to 224, 227, 225, and 230nm for CBZ, DMOB, BPA, and BA, respectively. The mobile phase used for the measurement of CBZ, DMOB, BPA and BA consisted of water (adjusted to pH2 by phosphoric acid)/methanol (60, v). The concentration of free chlorine was measured by DPD colorimetry using an ultraviolet-visible spectrophotometer (Shimadzu, multispec-1501). A calibration curve of chlorine concentration was established at high chloride ion concentrations.

Example 1: degradation of CBZ at different chloride ion concentrations

FIG. 2 (a) shows that the concentration of free chlorine at pH 7.50 is 2mgCl ₂ CBZ degradation kinetics as a function of chloride ion concentration at/L. As shown in fig. 2 (a), CBZ was not degraded during chlorination at chloride ion concentrations of 0.05 and 0.10M. This is consistent with previous studies that CBZ is resistant to chlorination at chloride concentrations of 1-10 mg/L. CBZ degradation during chlorination follows pseudo-first order degradation kinetics as chloride concentration increases to 0.20, 0.50 and 0.75M, with a rate constant (k) _CBZ ') 0.07, 0.66 and 1.80min, respectively ^-1 。

Further, at pH 7.50, at a sulfate concentration of 0.75M and 2mgCl ₂ The free chlorine dose/L was again tested and no CBZ degradation was observed within 15 minutes (see figure 3). This example shows that the increased CBZ degradation rate constant at high chloride ion concentrations is not caused by increased ion concentration.

Chlorine consumption increases with increasing chloride ion concentration, and k _CBZ ' have the same trend. Chlorine consumption during 15 minutes chlorination of CBZ reached 0.36, 0.66 and 0.74mgCl at chloride ion concentrations of 0.20, 0.50 and 0.75M, respectively ₂ L (see b of fig. 2). Consumption of chlorine relative to the corresponding k _CBZ Increased by ` indicating chlorine-containing reactivity at high chloride ion concentrationsThe material is responsible for the degradation of CBZ during chlorination. This is further confirmed by negligible CBZ degradation and chlorine decay at chloride ion concentrations of 0.05 and 0.10M (see fig. 2 a and b).

In the case of a chloride ion concentration of 0.75M, chlorine decay continued to occur even after degradation of all CBZ within 2 minutes, but chlorine did not self-decay even without CBZ at a chloride ion concentration of 1.00M (fig. 4). These results indicate that the chlorine-containing reactive species continuously react with the CBZ degradation products.

In addition, the CBZ degradation rate constant increases with increasing free chlorine concentration. As shown in FIG. 5, the amount of free chlorine was increased from 2 to 5mgCl ₂ L, k when the chloride ion concentration is 0.20, 0.50 and 0.75M, respectively _CBZ From 0.07, 0.66 and 1.80min ^-1 Increase to 0.19, 1.83 and 3.32min respectively ^-1 。

In the aqueous solution containing free chlorine, the three chlorine-containing reactive substances are respectively HOCl/ClO ^- 、Cl ₂ And Cl ₂ And O. As confirmed by the above test, cl ₂ O is identified as a chlorine-containing reactive species that rapidly degrades CBZ at high chlorine concentrations. FIG. 6 shows 2mgCl at pH 4.40 without additional chloride ion (28. Mu.M chloride ion), pH 4.40 ₂ Kinetics of degradation of CBZ and associated chlorine decay at free chlorine concentration/L, and 2mgCl at 0.20M chloride, pH 7.50 ₂ Degradation kinetics of CBZ at free chlorine concentration of/L and associated chlorine decay.

HOCl is the predominant chlorine species at pH 4.40 without additional chloride ions. No CBZ degradation or chlorine decay was observed, confirming HOCl/ClO ^- CBZ cannot be degraded. Whereas in the case of chloride ion at pH 7.50 and 0.20M, 65% of CBZ was degraded within 15 minutes with significant (0.36 mgCl) ₂ L) chlorine decay. In view of Cl ₂ The concentrations (equation 5) are similar under the two conditions in FIG. 6, and the difference between CBZ degradation also excludes Cl ₂ Is the predominant chlorine-containing reactive species, cl ₂ O is thus believed to achieve rapid degradation of CBZ.

K ₂ ＝5.25×10 ² M ^-2 Reaction formula 5

For this example, when no additional chloride ions were added to the solution, the chloride ions would be present at about the same molar concentration as the free chlorine added to the solution. For 2mgCl ₂ Initial free chlorine concentration/L, which will correspond to a chloride ion concentration of about 28. Mu.M. The pH-dependent balance is explained according to the following equation: k2 may be represented as follows

Thus, [ Cl ] can be calculated based on the following equation ₂ ]

[Cl ₂ ]＝K2[HOCl][H ⁺ ][Cl ^- ]Equation 2

When high concentration of NaCl is added, the coefficient γ influenced by the ionic strength (μ) may be considered based on the following equation _i

C _i Is the molar concentration of ion i (M, mol/L); z _i Is the charge number of ion i; parameter a depends on temperature T and standard conditions (25 ℃ water), yielding a =0.5085M ^-1/2 (ii) a The additional fitting parameter bi is a temperature dependent parameter.

If the effect of ionic strength (. Mu.) is considered, the pH dependent equilibrium constants K1' and [ Cl ] can be expressed using activity rather than molar concentration ₂ ]：

[Cl ₂ ]＝K2[HOCl]{H ⁺ }{Cl ^- Equation 7

At a free chlorine concentration of 2mgCl ₂ The effect of ionic strength was negligible when/L, pH was 4.40 and there was no additional chloride (28 μ M chloride). Since the chloride ion concentration was 28. Mu.M, which was the same as the free chlorine concentration, [ Cl ] was calculated by substituting all known values ₂ ]Is represented by [ Cl ₂ ] ₁ 。

[Cl ₂ ] ₁ ＝K2[HOCl][H ⁺ ][Cl ^- ]＝5.25×10 ² ×2.8×10 ^-5 ×1.0×10 ^-4.4 ×2.8×10 ^-5 ＝1.64×10 ^-11 M

At pH 7.50 and 0.20M chloride ion, the ionic strength μ is 0.2 (see equation 3), the activity coefficient γ _i Is 0.747 (see equation 4). K2' is 9.40X 10 ² Corrected to 0.2M ion intensity using the Davies equation. Calculating [ Cl ] according to equation 7 ₂ ]Is represented by [ Cl ₂ ] ₂ 。

[Cl ₂ ] ₂ ＝K2′[HOCl]{H ⁺ }{Cl ^- }＝9.40×10 ² ×2.8×10 ^-5 ×(0.747×1.0×10 ^-7.5 )×(0.747×0.2)＝9.3×10 ^-11 M

[Cl ₂ ] ₁ And [ Cl ₂ ] ₂ Almost the same, one is 1.64X 10 ^-11 M, and the other is 9.3X 10 ^-11 M。

The results of the above experiments and checking calculation show that Cl ₂ The formation of O requires only a low concentration of free chlorine (e.g., in an amount of a few ppm), and is well correlated with both chloride ion and free chlorine concentration. This is different from the prior art knowledge and further suggests Cl ₂ The formation of O may follow routes other than the conventional route (e.g., equation 4 above). In other words, at a high chloride ion content of not less than 0.20MCan exhibit a significantly high degradation rate constant for refractory contaminants (e.g., carbamazepine).

₂ Example 2: effect of chloride ion concentration on ClO formation

Pair of chlorine ions Cl ₂ The effect of O formation can be determined by k at a fixed free chlorine concentration _CBZ ' relative to chloride ion concentration ([ Cl ] ^- ]) The number of reaction stages.

Specifically, to quantify Cl ion pairs ₂ The influence of O formation was examined at 2 or 5mgCl ₂ K at fixed free chlorine concentration of/L _CBZ ' number of reaction stages relative to chloride ion concentration. The pseudo first order degradation kinetics k can be expressed as follows _obs ：

k _obs ＝a[Cl ^- ] ⁿ Equation 8

The logarithmic transformation of equation 8 yields equation 9

logk _obs ＝n log[Cl ^- ]+ loga equation 9

Wherein n represents [ Cl ^- ]The number of reaction stages of (a); a represents other influencing factors (e.g. [ HOCl ]]) The coefficient of (a).

As shown in FIG. 7, the concentration of free chlorine was 2 or 5mgCl ₂ at/L, by adding k _CBZ ' Natural logarithm of relative to [ Cl ^- ]Natural logarithm of (logk) _CBZ ' and log [ Cl ] ^- ]) Plotted, and their corresponding reaction orders were found to be 2.43 and 2.45. As shown in equation 5, high concentrations of chloride ions can result in HOCl/ClO ^- With Cl ₂ The equilibrium between them is shifted to form Cl with higher concentration ₂ (see equation 5), however k _CBZ ' reaction stages 2.43 and 2.45, which are still higher than that of HOCl/ClO due to participation of chloride ions alone ^- Formation of Cl ₂ A numerical value in the case of (2). Thus, chloride ions play two important roles, one is to promote HOCl/ClO ^- Conversion to Cl ₂ The other is with Cl ₂ Reaction to generate PVC monoanionic Cl _n ^- (n≥3)。

By adding 2mgCl at pH 4.40 and free chlorine and sodium sulfate concentrations, respectively ₂ Additional experiments were carried out under conditions of 0.10M and/L to verify chloride ion in Cl ₂ By formation of Cl _n ^- (n.gtoreq.3) to Cl ₂ Importance in the O process. This experiment provided almost the same Cl as the conditions for the pH 7.50 and 0.20M chloride ion ₂ Concentration and provides the same ionic strength, but using sulfate. No CBZ degradation was observed under this experimental condition (see fig. 8), however 65% of CBZ was degraded at pH 7.50 and 0.20M chloride, indicating that neither sulfate nor ionic strength promoted Cl ₂ To Cl ₂ And (4) converting O. Cl ^- And Cl ₂ By reaction of Cl ^- Lone pair electron generation charge transfer to Cl ₂ In (C) to result in Cl ₂ σ -anticodon orbital moiety in (1) to weaken Cl ₂ A chloro-chloro bond in (1). Cl _n ^- Thus easily reacted with HOCl/ClO ^- Electrophilic substitution reaction to form intermediate molecule [ ClOH … Cl … (Cl) _n -Cl] ^- Or [ ClO … Cl … (Cl) _n -Cl] ^2- In HOCl/ClO ^- A new oxygen-chlorine bond is formed between the oxygen atom of (a) and the chlorine atom of the weakened chlorine-chlorine bond. The intermediate molecules formed subsequently form Cl ₂ O and chloride ions. More active Cl with weaker chlorine-chlorine bond _n ^- Promote Cl ₂ Is coated with HOCl/ClO ^- Conversion to Cl ₂ O。

Based on the above experiment and the graph of FIG. 1, it can be seen that Cl is formed from chlorine ions and free chlorine in an aqueous solution containing chlorine ions at a concentration ₂ The pathway of O. The presence of high concentrations of chloride ions facilitates the conversion of HOCl to Cl ₂ (see reaction formula 5). The chloride ions are then reacted with Cl ₂ Reaction to form Cl _n ^- (see the following reaction scheme 6 ₃ ^- As a polyanion Cl _n ^- Examples of (d). Cl ₃ ^- With HOCl/ClO ^- React to formCl ₂ O and regeneration of Cl ^- (see reaction formulas 7 and 8). Generated Cl ₂ Rapid reaction or hydrolysis of O and CBZ to HOCl/ClO ^- . It can be seen that the present invention proposes the use of chloride ions in Cl ₂ Important roles in the O-forming pathway.

₂ Example 3: effect of pH on ClO formation

By adding at 0.20M and 2mgCl respectively ₂ Plot of chloride ion concentration and free chlorine concentration of/L _CBZ ' pH vs. Cl study with pH Change plot ₂ The effect of O formation. The different pH of the solution was controlled by phosphate buffer or NaOH/HCl. As shown in FIG. 9, k decreases as the pH decreases from 8.60 to 8.10, 7.50, 6.97, 6.44, 5.90 and 4.33 when the solution pH is controlled by NaOH/HCl _CBZ ' increased from 0.01 to 0.03, 0.1, 0.33, 0.85, 2.39, 3.49 and 6.65min, respectively ^-1 . Decrease of pH increases [ H ] ⁺ ]Moving the equilibrium of equation 5 towards more Cl production ₂ Is proceeding in the direction of (1), promoting Cl ₂ Formation of O, and thus k is increased _CBZ '. However, when the pH of the solution is maintained by NaOH/HCl, k _CBZ The' slope increasing from 6.44 to 4.33 is steeper than from 8.60 to 6.97. Two different slopes at different pH values indicate in addition to [ H ] ⁺ ]In addition to the other factors, k _CBZ '. In this regard, the inventors believe that, in addition to [ H ] ⁺ ]In addition, an increase in the concentration of HOCl also affects k _CBZ ', results in a steeper slope being observed at more acidic pH. As shown in reaction formula 8, due to Cl ₃ ^- And ClO ^- Electrostatic repulsion between, anionic reactant Cl ₃ ^- Reaction ratio with HOCl and its anionic analogue ClO ^- And faster. As the pH increased from 6.44 to 6.97, the ratio of HOCl to ClO-in the solution decreased from 6.5 to 1.9, as the pKa of HOCl/ClO-changed from 7.55 at low chloride concentration to 7.25 at high chloride concentration (at 25 ℃ conditions). ClO ^- The increase in concentration and decrease in HOCl concentration gradually changed the slope of kCBZ'.

₂ Example 4: effect of weakly acidic anions on ClO formation

By adding at 0.20M and 2mgCl respectively ₂ Measurement of CBZ degradation at chloride and free chlorine concentrations in the/L study of common weakly acidic anions, such as phosphate and carbonate ions, vs. Cl ₂ The effect of O formation, pH 7.50, was buffered by the addition of phosphate or bicarbonate or maintained by the addition of sodium hydroxide (as shown in figure 10). K of pH was maintained by addition of sodium hydroxide _CBZ ' is 0.10min ^-1 This is compared with the value buffered with bicarbonate (0.09 min) ^-1 ) And the value buffered with phosphate (0.07 min) ^-1 ) 1.11 and 1.43 times higher. Reduced k in the presence of phosphate or bicarbonate _CBZ ' mainly due to the presence of weakly acidic anions in solution, i.e. HPO ₄ ^2- /H ₂ PO ₄ ^- And CO ₃ ^2- /HCO ₃ ^- Will promote Cl ₂ Hydrolysis of O to HOCl/ClO ^- A similar pathway in the presence of acetic acid was followed as mentioned in the previous study. Cl ₂ O in HPO ₄ ^2- /H ₂ PO ₄ ^- Hydrolysis ratio in the presence of CO ₃ ^2- /HCO ₃ ^- Stronger in the presence of the catalyst due to nucleophilicity, i.e., overall ionic charge, HPO ₄ ^2- /H ₂ PO ₄ ^- And is stronger.

At pH 7.50, two forms of phosphate buffer (HPO) ₄ ^2- /H ₂ PO ₄ ^- ) Bicarbonate buffer (CO) in both forms ₃ ^2- /HCO ₃ ^- ) And two forms of HOCl/ClO ^- Are 16.95, 0.03 and 97.72, respectively. Specifically, for phosphoric acid, the ionic strength was negligible when no additional NaCl was present, and the phosphate dissociation constant (pK) _a1 ) Dissociation constant (pK) of dihydrogen phosphate _a2 ) And monohydrogen phosphate dissociation constant (pK) _a3 ) 2.15, 7.21 and 12.35 respectively. According to the Johansson study, pK 'when the salinity of the solution (S ‰) was increased to 11.7g/Kg (0.2 MNaCl)' _a1 、pK′ _a2 And pK' _a3 To 1.76, 6.27 and 9.36, respectively. pK 'using phosphate' _a1 、pK′ _a2 And pK' _a3 The morphology of phosphoric acid at different pH can be obtained (see fig. 16). At pH 7.50, dihydrogen phosphate (H) ₂ PO ₄ ^- ) And monohydrogen phosphate (HPO) ₄ ^2- ) The proportions in 5mM phosphate buffer solution were 5.5% and 93.2%, respectively.

For carbonic acid and bicarbonate, the carbonic acid dissociation constant (pK) when the ionic strength is neglected without addition of NaCl _a1 ) And bicarbonate dissociation constant (pK) _a2 ) 6.12 and 9.41 respectively. pK 'when the salinity of the solution (S ‰) increased to 11.7g/Kg (0.2M NaCl)' _a1 And pK' _a2 To 5.99 and 9.24, or 5.82 and 8.60, respectively. Similarly, pK 'of carbonic acid was used' _a1 And pK' _a2 The morphology of carbonic acid at different pH can be obtained (see fig. 16). At pH 7.50, bicarbonate (HCO) ₃ ^- ) And Carbonates (CO) ₃ ^2- ) The proportions in 5mM bicarbonate buffer were 95.3% and 2.9%, respectively.

Dissociation constant pK 'of hypochlorous acid (HOCl)' _a At 7.5 (μ =0, 25 ℃). When the salinity (S ‰) of the solution was increased to 11.7g/Kg (0.2M NaCl), pK' _a Down to 7.25.

Thus, the tendency of the total ionic charge is consistent with their nucleophilicity, i.e., phosphate buffer>Carbonate buffer>HOCl/ClO ^- 。

Furthermore, k at an environmentally relevant pH in the presence of phosphate or bicarbonate at high chloride ion concentrations _CBZ Is not greatly reduced, andstill lower than k at low chloride ion concentration _CBZ ' much higher (as shown in figure 11). K at pH 7.50 when buffered with bicarbonate buffer _CBZ ' higher than with phosphate buffer, but lower than with sodium hydroxide, thus k in the presence of bicarbonate at high chloride ion concentrations and environmentally relevant pH _CBZ ' should be between phosphate buffer and NaOH/HCl, while still well above the low chloride concentration k _CBZ ’。

₂ Example 5: effect of cation on ClO formation

FIG. 12 shows Mg at various cations, i.e., 0.05M ²⁺ 、0.1M Na ⁺ 、0.1M K ⁺ Degradation of CBZ in the presence of conditions. Mg can be seen ²⁺ 、Na ⁺ 、K ⁺ To k is paired with _CBZ The influence of' satisfies K ⁺ >Na ⁺ >Mg ²⁺ A trend of (c). At 0.05M K ⁺ In the presence of a chloride ion concentration of 0.1M, CBZ was totally degraded within 30 seconds. This indicates the presence of cations to Cl ₂ The formation of O has a significant influence, and the Cl produced can be controlled by controlling the kind and concentration of the cation ₂ The concentration of O.

Example 6: reactivity towards different organic structures

In this example, with respect to Cl ₂ Reactivity of O to CBZ with amine groups, cl was compared ₂ Reactivity of O towards aromatic contaminants containing methoxy, hydroxyl and carboxyl groups (represented by DMOB, BPA and BA, respectively). The degradation of DMOB during chlorination shows a similar trend to CBZ at different chloride ion concentrations (see a of figure 13). DMOB did not degrade at chloride concentrations of 0.10 and 0.20M, while k _DMOB ' at chloride concentrations of 0.50, 0.75 and 1.00M for 0.05, 0.13 and 0.25min respectively ^-1 Chlorine consumption during 15 minutes of chlorination was from 0.20, 0.45mgCl respectively ₂ the/L is increased to 0.54mgCl ₂ L (see fig. 14 a).

At 5mgCl without additional chloride ion and pH 4.40 ₂ No DMOB degradation at free chlorine concentration/L (see FIG. 15 fora) Or chlorine decay (see b of FIG. 15), which confirms HOCl/OCl ^- DMOB cannot be degraded. In the presence of 5mgCl at a pH of 7.50 and a chloride ion concentration of 0.75M ₂ DMOB degraded almost completely (100%) in 15 minutes at free chlorine/L with a marked chlorine decay (0.35 mgCl) ₂ L). Cl under the two conditions shown in a of FIG. 15 ₂ The concentrations are similar and differences in DMOB degradation exclude Cl ₂ As a chlorine-containing reactive substance, this confirmed Cl ₂ O is responsible for DMOB degradation. Furthermore, in the DMOB chlorination, the tests were performed at HOBr concentrations of 10, 20 and 50 μ M, respectively, and at pH 7.50. 10. 20 and 50. Mu.M HOBr contributed only about the same effect in chlorination, i.e., 5-6% of DMOB degradation (see c in FIG. 15), which excluded the effect of 0.5% bromide in NaCl on the rapid DMOB degradation in chlorination.

Thus, it was confirmed that Cl ₂ O (instead of HOCl/OCl) ^- 、Cl ₂ Or HOBr) for DMOB degradation (see fig. 15). However, at the same chloride ion concentration, k _DMOB ' less than k in Chlorination _CBZ ', indicates Cl ₂ O reacts more slowly with an aromatic compound attached to a methoxy group than with an aromatic compound attached to an amine.

FIG. 13 b shows 2mgCl without additional chloride ion (28. Mu.M chloride ion) and 0.20M chloride ion ₂ the/L free chlorine concentration and the kinetics of BPA degradation at pH 7.50. Pseudo-first order degradation Rate constant (k) for BPA in the absence of additional chloride ions and at a pH of 7.50 _BPA ') is 0.14min ^-1 This is due to BPA and HOCl/ClO ^- (see equation 9). When 0.20M chloride ion was added at pH 7.50, k _BPA ' increase to 0.30min ^-1 This is due to BPA and Cl ₂ Reaction between O (0.16 min) ^-1 ) And BPA with HOCl/ClO ^- In the middle (0.14 min) ^-1 ). Under the same conditions, cl ₂ Reaction Rate constant of O with BPA (0.16 min) ^-1 ) Comparison of the reaction Rate constant for CBZ (0.07 min) ^-1 ) Much higher, indicating Cl ₂ O reacts faster with the aromatic compound attached to the hydroxyl group than with the aromatic compound attached to the amine.This trend is further supported by the faster chlorine decay in the presence of BPA compared to CBZ (see fig. 14 b).

BPA + HOCl → product k = 3.10-6.62X 10 ⁴ M ^-1 S ^-1 Reaction formula 9

Unlike DMOB, CBZ and BPA, the concentrations of chloride ion and free chlorine are 0.20M and 2mgCl, respectively ₂ At pH 7.50,/L, BA did not degrade (see c in FIG. 13), with negligible chlorine decay (see c in FIG. 14). The results indicate that Cl is comparable to aromatic contaminants attached to methoxy, amine or hydroxyl groups ₂ O reacts much more slowly with aromatic contaminants attached to the carboxyl group. In other words, cl ₂ O reacts faster with aromatic contaminants having higher electron donating functional groups attached, i.e., hydroxyl groups>Amines as inhibitors of tyrosine kinase>Methoxy radical>>A carboxyl group. Due to Cl ₂ O undergoes predominantly electrophilic aromatic substitution, with functional groups having a higher electron donating ability rendering the aromatic contaminants more negatively charged, thus enhancing them towards Cl ₂ Reactivity of O.

FIG. 13 d shows the effect of NOM on CBZ degradation in chlorination reactions with chloride ion concentration of 1.00M. The presence of 0.50, 1.00 and 2.00mgDOC/L NOM reduced the degradation rate constant of CBZ by about 22%, 33% and 54%, respectively. Different concentrations of NOM vs k _CBZ The decrease in ` is mainly due to its Cl-ion ₂ O scavengers and HOCl/ClO ^- The effect of the quencher, as evidenced by chlorine decay under different conditions. 0.48mgCl in 15 min chlorination of NOM without additional chloride ion or CBZ ₂ Chlorine decay of/L (see d of FIG. 14) due to NOM and HOCl/ClO ^- Via oxidation and/or substitution. When 1.00M chloride ion was added but no CBZ was added, the chlorine decayed rapidly within 30 seconds (1.1 mgCl) ₂ /L) shows that NOM rapidly clears Cl ₂ And O. NOM vs Cl in 30 seconds ₂ The strong scavenging action of O is mainly due to the aromatic ring pair Cl in NOM linked to an electron withdrawing group such as a hydroxyl group ₂ O is reactive. After 30 seconds, there was a slow decay of chlorine (0.80 mgCl) ₂ /L) due to NOM and HOCl/ClO ^- (0.48 mgCl) ₂ /L) and NOM to Cl ₂ O removal (0.32 mgCl) ₂ /L), assuming initial Cl ₂ Changes in NOM structure by O attack do not affect NOM and HOCl/ClO ^- The reaction between them. NOM vs Cl after 30 seconds ₂ The poor clearance of O may be due to the fact that all of the reactive sites on the NOM are occupied by the original Cl ₂ The O-attack is consumed. When chloride and CBZ were added simultaneously, chlorine decay was increased by 0.56mgCl ₂ L, indicating the initial Cl ₂ The NOM structure before O-attack is more reactive than CBZ, but much less reactive thereafter. These results indicate that NOM is responsible for Cl in comparison to the scavenging mechanism for different free radicals ₂ O shows different scavenging mechanisms. NOM to Cl ₂ The strong scavenging action of O is only present at the beginning of the process, due to the neutralization of Cl in NOM ₂ The aromatic ring to which O is attached with a reactive electron withdrawing group is completely consumed within 30 seconds. Once these reactive moieties are consumed, NOM is towards Cl ₂ The O scavenging effect becomes much weaker.

In summary, according to the inventive concept, chloride ions can be generated by reacting HOCl/ClO ^- Conversion to Cl ₂ And form a polychloromonoanionic Cl _n ^- With HOCl/ClO ^- Further reaction to produce Cl ₂ And O. Lower pH promoted Cl ₂ Form and produce higher concentrations of Cl ₂ And O. Weak acid anions (phosphates and bicarbonates) are stronger nucleophiles and promote Cl ₂ And (4) hydrolyzing O. However, in the presence of phosphate or bicarbonate, at high chloride concentrations, the degradation rate constant of carbamazepine at environmentally relevant pH is still much higher than at low chloride concentrations. Cationic Mg ²⁺ 、Na ⁺ 、K ⁺ To Cl ₂ The influence of O generation satisfies K ⁺ >Na ⁺ >Mg ²⁺ The trend of (c). Cl formed ₂ O and a functional group attached to a higher electron donor (i.e., a hydroxyl group)>Amines as pesticides>Methoxy radical>>Carboxyl) react faster. In contrast, the usual free radical scavengers (natural organic substances) strongly scavenge Cl only at the beginning of the process ₂ O, but then has less effect.

Thus, the invention provides a novel chlorine-containing reactant (Cl) ₂ O) mechanism of formationGenerated Cl ₂ O can degrade refractory contaminants, particularly aromatic contaminants associated with electron donating functional groups. Cl of the invention ₂ The O formation mechanism suggests that only a low dose of free chlorine is required to form a significant amount of Cl in a high chlorine water environment ₂ O。

This opens up new opportunities for chlorination to control contaminants in seawater and high chloride containing wastewater (e.g., brackish ground water, reverse osmosis brine, hydraulic fracturing wastewater, ballast water, and landfill leachate). Use of Cl in contaminant degradation ₂ O as an oxidizing agent is less affected by water quality parameters (pH, alkalinity and NOM) than AOP technologies based on different free radicals. Cl ₂ O degrades recalcitrant micropollutants, such as CBZ, at a very rapid rate over a wide pH range of 4.33-8.60. Near neutral pH, its performance is hardly affected by bicarbonate, a radical scavenger common in AOP technology based on different radicals. The presence of NOM primarily scavenges Cl at the start of the process ₂ O, but then with less Cl ₂ O scavenging effect. Such Cl ₂ The O formation mechanism can also manifest its potential role in disrupting the active layer of RO membranes by oxidizing aromatic moiety-containing polyamide, polybenzimidazoline, and polyoxadiazole-based polymers in high salinity water in the presence of low concentrations of free chlorine.

Cl according to the invention ₂ The O formation mechanism, the different free chlorine species (i.e., HOCl/ClO) can be mapped by considering the concentration of chloride, free chlorine, phosphate/carbonate, cation ^- 、Cl ₂ And Cl ₂ O) new forms at different pH. In the new chlorine form, cl ₂ Concentration of O and Cl ₂ Will increase with decreasing pH. This change in chlorine morphology indicates Cl ₂ And Cl ₂ The reactivity of O to different contaminants and its contribution to contaminant degradation is different from what is known in the art.

Although a few embodiments have been described herein, other ways and modifications will be apparent from this specification. The inventive concept is therefore not limited to such embodiments, but is to be defined by the appended claims along with their full scope of various obvious modifications and equivalent arrangements, which may be apparent to those skilled in the art.

Claims

1. A method for generating dichlorine monoxide in situ in an aqueous environment comprising:

to the aqueous environment in an amount of 2 to 5mgCl ₂ Addition of free chlorine at a dosage of/L, initiation of HOCl and/or ClO in said aqueous environment ^- To generate dichlorine monoxide;

wherein the aqueous environment has an initial chloride ion concentration of 0.1M or greater, an

Wherein the free chlorine is selected from HOCl and ClO ^- 、Cl ₂ 、Cl ₂ O and any combination thereof.

2. The method of claim 1, wherein the aqueous environment has an initial chloride ion concentration of 0.2-1.0M.

3. The method of claim 1, wherein the free chlorine is an alkali metal hypochlorite or an alkaline earth metal hypochlorite.

4. The method of claim 1, wherein the aqueous environment has a pH of 4-9, such as 4.33-8.60.

5. The method of claim 1, wherein prior to or concurrent with the addition of the free chlorine, an acid and/or hydroxide is used to adjust the pH of the aqueous environment; or adjusting the chloride ion concentration of the aqueous environment to have a chloride ion concentration of greater than or equal to 0.1M prior to adding the free chlorine.

6. The method of claim 1, wherein the concentration of the generated dichloro-oxygen is controlled by adjusting: the concentration of the free chlorine in the aqueous environment; the concentration of chloride ions, the pH of the aqueous environment, the type and concentration of non-chloride anions and/or cations contained therein.

7. The method of claim 5, wherein the non-chloride anion comprises carbonate, bicarbonate, phosphate, dihydrogen phosphate, monohydrogen phosphate, and is present in a concentration of 5mM or greater; and the cation includes an alkali metal ion or an alkaline earth metal ion such as potassium ion, sodium ion, magnesium ion, and its concentration is 0.05-1M.

8. A method of treating a pollutant in an aqueous environment, comprising:

forming dichlorine monoxide in the aqueous environment by the method of any one of claims 1-7, wherein the aqueous environment has an initial chloride ion concentration of 0.1M or greater;

reacting the dichloro monoxide with the contaminant.

9. The method of claim 8, wherein the contaminants are aromatic contaminants having electron donating functional groups, such as aromatic contaminants containing hydroxyl, amine, or methoxy groups.

10. The method of claim 8, wherein the chlorine-containing aqueous environment is brackish groundwater, reverse osmosis brine, hydraulic fracturing wastewater, ballast water, or landfill leachate.