阅读说明：本技术 用于检测环境修复工程中残留药剂的方法 (Method for detecting residual medicament in environmental remediation engineering ) 是由 徐新 唐华晨 王殿二 高国龙 于 2019-12-04 设计创作，主要内容包括：本发明提供一种用于检测环境修复工程中残留药剂的方法。所述药剂包括过氧化氢和过硫酸盐,所述方法包括：步骤S1：获取待检测溶液；步骤S2：采用第一氧化剂标准溶液对待检测溶液进行滴定,获取在所述滴定过程中氧化还原电位值发生第一次突跃时消耗第一氧化剂标准溶液的体积V<Sub>1</Sub>；步骤S3：向待检测溶液中加入还原剂溶液,充分反应,以使待检测溶液的电位稳定在第一预定值以下；步骤S4：采用第二氧化剂标准溶液对待检测溶液进行滴定,获取在滴定过程中氧化还原电位发生第二次突跃时消耗第二氧化剂标准溶液的体积V；步骤S5：分别计算待检测溶液中的过氧化氢和过硫酸盐的摩尔浓度。根据本发明的方法,能够同时检测过氧化氢和过硫酸盐的浓度。(The invention provides a method for detecting residual medicaments in environmental remediation engineering. The agent comprises hydrogen peroxide and a persulfate salt, and the method comprises: step S1: obtaining a solution to be detected; step S2: titrating a solution to be detected by adopting a first oxidant standard solution to obtain a volume V of the first oxidant standard solution consumed when an oxidation-reduction potential value generates a first sudden change in the titration process 1 (ii) a Step S3: adding a reducing agent solution into the solution to be detected, and fully reacting to enable the potential of the solution to be detected to be stable below a first preset value; step S4: titrating the solution to be detected by adopting a second oxidant standard solution to obtain the volume V of the second oxidant standard solution consumed when the oxidation-reduction potential generates a second sudden change in the titration process; step S5: and respectively calculating the molar concentrations of the hydrogen peroxide and the persulfate in the solution to be detected. According to the method of the present invention, the concentrations of hydrogen peroxide and persulfate can be simultaneously detected.)

1. A method for detecting residual agents in environmental remediation projects, wherein the agents comprise hydrogen peroxide and persulfate, the method comprising:

step S1: obtaining a solution to be detected, wherein the volume of the solution to be detected is V;

step S2: carrying out the detection on the solution to be detected by adopting a first oxidant standard solutionTitrating, recording the oxidation-reduction potential of the solution to be detected in the titration process until the oxidation-reduction potential changes to be stable after the first sudden change of the oxidation-reduction potential, and obtaining the volume V of the first oxidant standard solution consumed when the first sudden change of the oxidation-reduction potential occurs₁Wherein the molar concentration of the first oxidant standard solution is C₁；

Step S3: adding a reducing agent solution into the solution to be detected, fully reacting to enable the potential of the solution to be detected to be stable below a first preset value, and recording the concentration C of the reducing agent solution₂And volume V₂；

Step S4: titrating the solution to be detected by adopting a second oxidant standard solution, recording the oxidation-reduction potential of the solution to be detected in the titration process until the oxidation-reduction potential is subjected to a second sudden change, wherein the change of the oxidation-reduction potential tends to be stable, and obtaining the volume V of the second oxidant standard solution consumed when the oxidation-reduction potential is subjected to the second sudden change₃Wherein the molar concentration of the second oxidant standard solution is C₃；

Step S5: and respectively calculating the molar concentrations of the hydrogen peroxide and the persulfate in the solution to be detected.

2. The method according to claim 1, characterized in that the molar concentration of hydrogen peroxide in the solution to be tested

the molar concentration of persulfate in the solution to be detected

3. The method of claim 1, wherein the first oxidant standard solution and the second oxidant standard solution are the same.

4. The method of claim 1, wherein the first and/or second oxidant standard solutions comprise: ceric sulfate solution.

5. The method according to claim 1, wherein in step 2, the volume V of the standard solution of the first oxidant consumed at the first jump in the redox potential value is obtained₁The method comprises the following steps:

step S21: during the titration of the solution to be detected with a first oxidant standard solution, drawing an E-V curve and/or a delta E/delta V-V curve relating to the redox potential;

step S22: obtaining a first fixed jump point from the E-V curve and/or the delta E/delta V-V curve related to the oxidation-reduction potential, wherein the first fixed jump point is the maximum point of the oxidation-reduction potential change rate or the highest point in the delta E/delta V-V curve, and the volume of the first oxidant standard solution corresponding to the first fixed jump point is the volume V of the first oxidant at the first jump of the oxidation-reduction potential₁。

6. The method according to claim 1, wherein in step 4, the volume V of the standard solution of the second oxidant consumed at the time when the redox potential is at the second jump is taken₃The method comprises the following steps:

step S41: during the titration of the solution to be detected with a second oxidant standard solution, drawing an E-V curve and/or a delta E/delta V-V curve relating to the redox potential;

step S42: obtaining a second titration jump point from the E-V curve and/or the delta E/delta V-V curve of the oxidation-reduction potential, wherein the second titration jump point is the maximum point of the change rate of the oxidation-reduction potential or the highest point in the delta E/delta V-V curve, and the volume of the second titration jump point is the volume V of the second oxidant standard solution when the change of the oxidation-reduction potential is the fastest₃。

7. The method according to claim 1, wherein in the step S2, during the titration of the solution to be detected with the first oxidant standard solution, an excess amount of the first oxidant standard solution is dropped.

8. The method according to claim 1, wherein in the step S4, an excess amount of the second oxidant standard solution is dropped during the titration of the solution to be detected with the second oxidant standard solution.

9. The method according to claim 1, wherein before the step S2, further performing: adding a free radical terminator and an acid solution into the solution to be detected so as to enable the pH value of the solution to be detected to be smaller than a first preset pH value.

10. The method according to claim 1, wherein the step S1 includes: obtaining a raw water sample to be detected, and diluting the raw water sample to obtain the solution to be detected.

Technical Field

The invention relates to the field of environmental protection, in particular to a method for detecting residual medicaments in environmental remediation engineering.

Background

In the restoration technology of the polluted site, chemical oxidation is the main treatment means for restoring organic polluted soil and underground water. Sodium persulfate is currently the most common peroxygen agent injected. The main activating means comprises heat activation, alkali activation, ferrous ion activation and hydrogen peroxide activation.

In the method of activating sodium persulfate by hydrogen peroxide, the concentrations of two oxidizing agents cannot be simply and respectively measured due to the use of the two oxidizing agents. Hydrogen peroxide activates persulfate, one important mechanism is hydrogen peroxide, hydroxyl free radical (OH) is generated through decomposition, and then the persulfate is activated by the free radical to generate sulfate free radical, and the specific reaction formula is as follows:

S₂O₈ ^2-+OH·→SO₄ ^2-+SO₄ ^·-+1/2O₂+H⁺。

however, since the activation time of hydrogen peroxide is short and a large amount of decomposition gas is often generated, it is generally necessary to inject hydrogen peroxide several times in order to maintain the hydrogen peroxide concentration. Therefore, the concentration of the residual hydrogen peroxide and persulfate in the water needs to be detected in the groundwater remediation construction process.

A method for detecting the concentration of hydrogen peroxide and persulfate is characterized in that the residual of a peroxide medicament is determined by adopting an indicator titration method, and because a water sample in a polluted site is always turbid and colored, the common volumetric indicator titration method is adopted, the endpoint is difficult to judge due to color interference, and in addition, an organic indicator can be oxidized and decomposed under the action of a strong oxidant and cannot be used.

Therefore, the present invention provides a method for detecting residual drugs in environmental remediation engineering to solve the problems of the prior art.

Disclosure of Invention

In this summary, concepts in a simplified form are introduced that are further described in the detailed description. This summary of the invention is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

In order to solve the problems in the prior art, the invention provides a method for detecting residual medicament in environmental remediation engineering, wherein the medicament comprises hydrogen peroxide, and the method comprises the following steps:

step S1: obtaining a solution to be detected, wherein the volume of the solution to be detected is V;

step S2: titrating the solution to be detected by adopting a first oxidant standard solution, recording the oxidation-reduction potential of the solution to be detected in the titration process until the oxidation-reduction potential is subjected to first sudden change, wherein the change of the oxidation-reduction potential tends to be stable, and obtaining the volume V of the first oxidant standard solution consumed when the oxidation-reduction potential value is subjected to the first sudden change₁Wherein the molar concentration of the first oxidant standard solution is C₁；

Step S3: adding a reducing agent solution into the solution to be detected, fully reacting to enable the potential of the solution to be detected to be stable at a first preset value, and recording the concentration C of the reducing agent solution₂And volume V₂；

Step S4: titrating the solution to be detected by adopting a second oxidant standard solution, recording the oxidation-reduction potential of the solution to be detected in the titration process until the oxidation-reduction potential is subjected to a second sudden change, wherein the change of the oxidation-reduction potential tends to be stable, and obtaining the volume V of the second oxidant standard solution consumed when the oxidation-reduction potential is subjected to the second sudden change₃Wherein the molar concentration of the second oxidant standard solution is C₃；

Step S5: and respectively calculating the molar concentrations of the hydrogen peroxide and the persulfate in the solution to be detected.

Illustratively, the molar concentration of hydrogen peroxide in the solution to be assayed

Wherein m is an equivalent coefficient representing the number of moles of hydrogen peroxide reacted with a unit number of moles of the reducing agent;

the molar concentration of persulfate in the solution to be detectedWherein l, n and w are equivalent coefficients representing the number of moles of the first oxidizing agent, the number of moles of the persulfate, and the number of moles of the second oxidizing agent, respectively, that react with a unit number of moles of the reducing agent.

Illustratively, the first oxidant standard solution and the second oxidant standard solution are the same.

Illustratively, the first and/or second oxidant standard solutions include: ceric sulfate solution.

Illustratively, in said step 2, a volume V of said first oxidant standard solution consumed at a first jump in said redox potential value is obtained₁The method comprises the following steps:

step S21: during the titration of the solution to be detected with a first oxidant standard solution, drawing an E-V curve and/or a delta E/delta V-V curve relating to the redox potential;

step S22: obtaining a first fixed jump point from the E-V curve and/or the delta E/delta V-V curve related to the oxidation-reduction potential, wherein the first fixed jump point is the maximum point of the change rate of the oxidation-reduction potential or the maximum point of a first differential curve, and the volume of the first oxidant standard solution corresponding to the first fixed jump point is the volume V of the first oxidant at the time of the jump of the oxidation-reduction potential value₁。

Illustratively, in said step 5, a volume V of said second oxidant standard solution consumed at said redox potential at the occurrence of said second jump is taken₃The method comprises the following steps:

step S41: during the titration of the solution to be detected with a second oxidant standard solution, drawing an E-V curve and/or a delta E/delta V-V curve relating to the redox potential;

step S42: obtaining a second titration jump point from the E-V curve and/or the Δ E/Δ V-V curve of the redox potential, wherein the second titration jump point is obtainedThe titration jump point is the maximum point of the change rate of the oxidation-reduction potential or the highest point of the Delta E/Delta V-V curve, and the volume of the second titration jump point is the volume V of the second oxidant standard solution at the time of the jump of the oxidation-reduction potential value₃。

Illustratively, in the step S2, during the process of titrating the solution to be detected with the first oxidant standard solution, an excess amount of the first oxidant standard solution is dropped.

Illustratively, in the step S4, during the titration of the solution to be detected with the second standard solution of the oxidizing agent, an excess amount of the second standard solution of the oxidizing agent is dropped.

Before the step S2, it is further exemplary to: adding a free radical terminator and an acid solution into the solution to be detected so as to enable the pH value of the solution to be detected to be smaller than a first preset pH value.

Exemplarily, the step S1 includes: obtaining a raw water sample to be detected, and diluting the raw water sample to obtain the solution to be detected.

According to the method for detecting the residual medicament in the environmental remediation engineering, hydrogen peroxide in the residual medicament is measured by adopting a potentiometric titration method, the hydrogen peroxide in the detection solution is titrated by the standard oxidizing agent solution, the change trend of the oxidation-reduction potential is obtained by establishing oxidation-reduction balance with the hydrogen peroxide, and the using amount of the standard oxidizing agent solution for reacting with the hydrogen peroxide is obtained by the sudden-crossing point of the oxidation-reduction potential, so that the content of the hydrogen peroxide in the detection solution is determined, and the using amount of the standard oxidizing agent solution can be accurately obtained by the oxidation-reduction potential, so that the content of the hydrogen peroxide in the solution can be accurately detected, and the detection process is simple and the result is accurate. Adding excessive reducing agent standard solution into the solution, enabling the reducing agent and persulfate in the solution to be detected to generate oxidation-reduction reaction, after full reaction, enabling the oxidation-reduction potential to be lower than a preset target value, dripping second oxidizing agent standard solution, determining the excessive amount of the reducing agent which performs oxidation-reduction reaction with the persulfate, and indirectly obtaining the amount of the persulfate which performs oxidation-reduction reaction with the reducing agent. Because redox balance is established between the second oxidant and the reducing agent, the dosage of the oxidant standard solution during the oxidation-reduction potential jump is obtained by recording the oxidation-reduction potential value of the system, and the dosage of the persulfate which has oxidation-reduction reaction with the reducing agent in the detection process can be calculated, so that the content of the persulfate in the solution to be detected is obtained. Compared with a direct potential method, the potentiometric titration does not need an accurate electrode potential value, is not influenced by temperature and liquid junction potential, and has better accuracy than the direct potential method; compared with an indicator titration method, the method is not influenced by turbidity and chromaticity of a detection solution, and potentiometric titration can be used for colored or turbid samples with small or unobvious titration jump, and has a wide application range.

Drawings

The following drawings of the invention are included to provide a further understanding of the invention. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

In the drawings:

FIG. 1 is a flow chart of a method for detecting residual agents in environmental remediation projects, according to one embodiment of the invention;

FIG. 2 is a schematic illustration of an E-V curve obtained in a method for detecting residual agents in environmental remediation projects, according to an embodiment of the present disclosure;

fig. 3 is a schematic diagram of a Δ E/Δ V-V curve obtained in a method for detecting residual agents in environmental remediation projects, according to an embodiment of the present invention.

Detailed Description

In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the present invention. It will be apparent, however, to one skilled in the art, that the present invention may be practiced without one or more of these specific details. In other instances, well-known features have not been described in order to avoid obscuring the invention.

In order to provide a thorough understanding of the present invention, a detailed description will be given in the following description to illustrate the method for detecting a residual agent in environmental remediation engineering according to the present invention. It is apparent that the practice of the invention is not limited to the specific details known to those skilled in the art of environmental protection. The following detailed description of the preferred embodiments of the invention, however, the invention is capable of other embodiments in addition to those detailed.

It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the invention. As used herein, the singular is intended to include the plural unless the context clearly dictates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

In order to solve the problems in the prior art, the invention provides a method for detecting residual medicament in environmental remediation engineering, which comprises the following steps:

step S1: obtaining a solution to be detected, wherein the volume of the solution to be detected is V;

step S2: titrating the solution to be detected by adopting a first oxidant standard solution, recording the oxidation-reduction potential of the solution to be detected in the titration process until the oxidation-reduction potential is subjected to first sudden change, wherein the change of the oxidation-reduction potential tends to be stable, and obtaining the volume V of the first oxidant standard solution consumed when the oxidation-reduction potential value is subjected to the first sudden change₁Wherein the molar concentration of the first oxidant standard solution is C₁；

Step S3: calculating the molar concentration of hydrogen peroxide in the solution to be detected, wherein,

the molar concentration of hydrogen peroxide in the solution to be testedWherein m isAn equivalent coefficient representing the number of moles of hydrogen peroxide reacted per mole of the reducing agent;

step S4: adding a reducing agent solution to the solution to be detected after the step S2 is performed, so that the potential of the solution to be detected is stabilized below a first preset value, and recording the concentration C of the reducing agent solution₂And volume V₂；

Step S5: titrating the solution to be detected by adopting a second oxidant standard solution, recording the oxidation-reduction potential of the solution to be detected in the titration process until the oxidation-reduction potential is subjected to a second sudden change, wherein the change of the oxidation-reduction potential tends to be stable, and obtaining the volume V of the second oxidant standard solution consumed when the oxidation-reduction potential is subjected to the second sudden change₃Wherein the molar concentration of the second oxidant standard solution is C₃；

Step S6: and calculating the molar concentrations of the hydrogen peroxide and the persulfate in the solution to be detected.

The method for detecting residual agents in environmental remediation projects of the present invention is schematically illustrated with reference to fig. 1-3, wherein fig. 1 is a flow chart of a method for detecting residual agents in environmental remediation projects according to an embodiment of the present invention; FIG. 2 is a schematic illustration of an E-V curve obtained in a method for detecting residual agents in environmental remediation projects, according to an embodiment of the present disclosure; fig. 3 is a schematic diagram of a Δ E/Δ V-V curve obtained in a method for detecting residual agents in environmental remediation projects, according to an embodiment of the present invention.

First, referring to fig. 1, step S1 is performed: obtaining a solution to be detected, wherein the volume of the solution to be detected is V.

In the remediation of a polluted site, when soil is subjected to ex-situ stirring and oxidation, the soil construction is non-uniform, and the concentration of local sodium persulfate does not reach the designed concentration, so that pollutants cannot be effectively oxidized and decomposed, and the construction is required to be monitored; in site in situ remediation, the injection concentration is often higher than 10%. However, due to different hydrogeology conditions, the concentrations of the sodium persulfate after being diffused into soil and underground water are different, the remediation effect is directly influenced, the sodium persulfate is easy to react and decompose in an activated state, and the concentration of an oxidant needs to be ensured for supplementary injection. In order to monitor the effect of engineering construction, optimize the dosage of the medicament and monitor the reaction condition of the medicament and pollutants, the amount of the residual medicament in the soil and underground water after remediation needs to be accurately measured.

In this embodiment, the solution to be detected is groundwater.

Illustratively, the solution to be detected is also diluted during the process of obtaining the solution to be detected. In the subsequent steps, the diluted solution to be detected is measured to obtain the medicament content, and the concentration of the medicament in the obtained solution to be detected can be obtained by multiplying the dilution times, namely the concentration of the medicament in the underground water to be detected. The process of diluting the obtained groundwater solution to be detected is to avoid the situation that a large amount of reducing agent needs to be added due to excessive oxidizing agent in the solution. It will be appreciated by those skilled in the art that the technical effects of the present invention can be achieved with or without dilution during actual operation.

In one example according to the present invention, 50mL of deionized water is sucked and placed in a 250mL conical flask, 1mL of groundwater to be detected is added and then shaken up to obtain the liquid to be detected in the step.

Next, with continued reference to fig. 1, step S2 is performed: titrating the solution to be detected by adopting a first oxidant standard solution, recording the oxidation-reduction potential of the solution to be detected in the titration process until the change value of the oxidation-reduction potential is stable, and obtaining the volume V of the first oxidant standard solution consumed in the sudden jump of the oxidation-reduction potential value₁Wherein the molar concentration of the first oxidant standard solution is C₁。

Measuring hydrogen peroxide in a residual medicament by adopting a potentiometric titration method, titrating the hydrogen peroxide in a detection solution by using an oxidant standard solution, obtaining the edge trend of an oxidation-reduction potential by establishing oxidation-reduction balance between the hydrogen peroxide and the hydrogen peroxide, and obtaining the using amount of the oxidant standard solution for reacting with the hydrogen peroxide by using a jump point of the oxidation-reduction potential so as to determine the content of the hydrogen peroxide in the detection solution, wherein the using amount of the oxidant standard solution can be accurately obtained by using the oxidation-reduction potential, so that the content of the hydrogen peroxide in the solution can be accurately detected, the detection process is simple, and the result is accurate. Compared with a direct potential method, the potentiometric titration does not need an accurate electrode potential value, is not influenced by temperature and liquid junction potential, and has better accuracy than the direct potential method; compared with an indicator titration method, the method is not influenced by turbidity and chromaticity of a detection solution, and potentiometric titration can be used for colored or turbid samples with small or unobvious titration jump, and has a wide application range.

Illustratively, before executing step S2, further executing: adding a free radical terminator and an acid solution into the solution to be detected so as to enable the pH value of the solution to be detected to be smaller than a first preset pH value.

Because the solution to be detected often contains persulfate which can generate sulfate radicals with strong oxidizing property, in order to avoid the influence on quantitative calculation caused by the reaction of the sulfate radicals in the solution and pollutants, a radical terminator and an acid solution are added into the detection solution, so that the pH value of the solution to be detected is smaller than a first preset pH value, and the oxidizing property of an oxidizing agent is enhanced.

Illustratively, the radical terminator includes ethanol, t-butanol, and the like.

Illustratively, the acid solution comprises dilute sulfuric acid or dilute hydrochloric acid.

Illustratively, the concentration of dilute sulfuric acid ranges from 1mol/L to 10 mol/L.

In one example according to the invention, a small amount of a radical terminator is added, illustratively, dilute sulfuric acid in an amount ranging from 0.01 to 0.05 g. And then dilute sulfuric acid is used for reducing the pH value of the solution to be detected to be less than 3. Illustratively, the amount of dilute sulfuric acid used is in the range of 1ml to 10 ml.

Illustratively, the first oxidant standard solution comprises ceric sulfate solution, the ceric sulfate has high oxidizing property, and Ce in the ceric sulfate solution⁴⁺|Ce³⁺In the subsequent measurement of the persulfate content in the solution to be tested, Ce⁴⁺|Ce³⁺With Fe³⁺|Fe²⁺All are reversible pairs, and can establish redox balance at the moment of reaction, thereby obtaining accurate measurement results.

Wherein the reaction of the following reaction formula (1) occurs after the ceric sulfate solution is dripped into the solution to be detected:

2Ce⁴⁺+H₂O₂＝2Ce³⁺+2H⁺+O₂↑ (1)

by measuring the variation curve of the oxidation-reduction potential value of the solution to be detected, the amount of the ceric sulfate reacted with the hydrogen peroxide in the solution to be detected can be determined, so that the amount of the hydrogen peroxide can be determined.

Illustratively, in said step 2, a volume V of said first oxidant standard solution at a first jump in said redox potential value is obtained₁The method comprises the following steps:

step S21: during the titration of the solution to be detected with a first oxidant standard solution, drawing an E-V curve and/or a delta E/delta V-V curve relating to the redox potential;

step S22: obtaining a first fixed jump point from the E-V curve and/or the delta E/delta V-V curve related to the oxidation-reduction potential, wherein the first fixed jump point is the maximum point of the oxidation-reduction potential change rate or the highest point in the first differential curve, and the volume of the first oxidant standard solution corresponding to the first fixed jump point is the volume V of the first oxidant at the time of the oxidation-reduction potential value jump₁。

Referring to fig. 2 and 3, schematic diagrams of an E-V curve and a Δ E/Δ V-V curve, respectively, obtained in one embodiment according to the present invention are shown. Wherein, in FIG. 2, the curve shown in section A1 represents that an E-V curve with respect to the oxidation-reduction potential is obtained in step S3, wherein the oxidation-reduction potential changes with the change in the volume of the oxidant standard solution dropped, wherein the point at which the slope of the change in the oxidation-reduction potential is the maximum is the titration jump point, and the volume V of the oxidant standard solution corresponding to the maximum point in the slope is the volume V of the oxidant standard solution₁The first at the time of sudden change of oxidation-reduction potential valueVolume V of standard solution of oxidizing agent₁. To further obtain an accurate titration jump point, as shown in FIG. 3, a Δ E/Δ V-V curve with respect to oxidation-reduction potential is made according to FIG. 2, wherein the section A2 shows a Δ E/Δ V-V curve corresponding to the section A1 in FIG. 2, which shows a change tendency of a slope of oxidation-reduction potential changing with a volume of dropping of the first oxidant standard solution, wherein the volume V1 of the first oxidant standard solution corresponding to the maximum value of the slope is the volume V of the first oxidant standard solution at the time of the jump in the value of oxidation-reduction potential₁。

Illustratively, in the step S2, during the process of titrating the solution to be detected with the first oxidant standard solution, an excess amount of the first oxidant standard solution is dripped. In order to completely react the hydrogen peroxide with the first oxidant standard solution, excessive oxidant standard solution is dripped, so that the obtained E-V curve and the obtained delta E/delta V-V curve have clear potential jump points, and accurate detection results can be obtained.

As shown in fig. 2 and 3, in one example according to the present invention, an excess amount of the first oxidant standard solution is dropped to V₁₁. Illustratively, a ceric sulfate standard solution, as a first oxidant standard solution, in which the concentration of the ceric sulfate standard solution is in the range of 0.01mol/L to 0.5mol/L, is dropped with an excess amount of the oxidant standard solution, and the amount of the oxidant standard solution dropped at this time is recorded as V₁₁。V₁₁-V₁In the range of 2ml to 5 ml.

It is to be understood that the above-mentioned ranges for the concentration of the ceric sulfate standard solution and the volume of the excess oxidant standard solution to be dropped are merely illustrative examples, and those skilled in the art can set them according to the specific operation during the actual detection operation.

Next, with continued reference to fig. 1, step S3 is performed: adding a reducing agent solution into the solution to be detected so as to enable the potential of the solution to be detected to be stable at a first preset value, and recording the concentration C of the reducing agent solution₂And volume V₂；

After step S2 is executed, an excessive amount of reducing agent is added to the solution to be detected, so that the reducing agent and the persulfate in the solution to be detected undergo redox reaction, and the potential drops to within a first predetermined value, illustratively 500mv, so that the whole solution to be detected is in a stable reduction state. The amount of the persulfate that undergoes the redox reaction with the persulfate is indirectly obtained by determining the excess amount of the reducing agent that undergoes the redox reaction with the persulfate by dropping the second standard solution of the oxidizing agent during the redox potential titration in the subsequent step S4. Because redox balance is established between the oxidant and the reducing agent, the dosage of the oxidant standard solution during the redox potential jump is obtained by recording the redox potential value of the system, and the dosage of the persulfate which has redox reaction with the reducing agent in the detection process can be calculated, so that the content of the persulfate in the solution to be detected is obtained, the detection process is simple, and the result is accurate. Compared with a direct potential method, the potentiometric titration does not need an accurate electrode potential value, is not influenced by temperature and liquid junction potential, and has better accuracy than the direct potential method; compared with an indicator titration method, the method is not influenced by turbidity and chromaticity of a detection solution, and potentiometric titration can be used for colored or turbid samples with small or unobvious titration jump, and has a wide application range.

Illustratively, the reducing agent solution includes: ammonium ferrous sulfate solution, and ferrous chloride solution. Using a salt containing ferrous ions as a reducing agent, during a subsequent redox titration, Fe³⁺|Fe²⁺Is a reversible point pair, and can establish oxidation reaction balance in the reaction moment, so that the detection result is more accurate.

In an example of using a salt containing a ferrous ion as the reducing agent, the reducing agent reacts with a persulfate as shown in the following reaction formula (2):

S₂0₈ ^2-+2Fe²⁺＝2SO₄ ^2-+2Fe³⁺(2)

in one example according to the present invention, a ferrous ammonium sulfate solution is used as the reducing agent, wherein the molar concentration of ferrous ammonium sulfate is in the range of 0.05-1 mol/L. The dosage of the ferrous ammonium sulfate solution is 5-20 ml.

After the reducing agent is added to react with the persulfate, the solution potential is guaranteed to be stable for a first predetermined value, illustratively below 500 mv.

Continuing to refer to fig. 1, step S4 is executed to titrate the solution to be detected with a second standard solution of an oxidant, and record the oxidation-reduction potential of the solution to be detected during the titration until the oxidation-reduction potential variation value is stable, and obtain a volume V of the second standard solution of the oxidant consumed during the sudden jump of the oxidation-reduction potential value₃Wherein the molar concentration of the second oxidant standard solution is C₃。

Illustratively, the second oxidant standard solution is the same as the first oxidant standard solution.

The second oxidant standard solution for titrating the persulfate is set to be the same as the first oxidant standard solution for titrating the hydrogen peroxide, so that the use variety of the oxidant is reduced, the influence factor of a reaction system is reduced, and the accuracy is improved.

It is to be understood that, in the present embodiment, it is only an example that the first oxidant standard solution and the second oxidant standard solution are set to be the same, and those skilled in the art will understand that the first oxidant standard solution and the second oxidant standard solution are set to be the same or different and are applicable to the present invention.

In one example according to the present invention, both the first and second oxidant standard solutions are set as ceric sulfate solutions.

In one example according to the present invention, the second oxidant standard solution includes: ceric sulfate and potassium permanganate solution.

The oxidant standard solution is a ceric sulfate solution, and in the example of using the ceric sulfate solution as the oxidant standard solution and using ammonium ferrous sulfate as the reducing agent, a reaction shown in the following reaction formula (3) occurs during potentiometric titration:

Ce⁴⁺+Fe²⁺＝Ce³⁺+Fe³⁺(3)

ceric sulfate has high stability, and Ce is added during titration⁴⁺|Ce³⁺And Fe³⁺|Fe²⁺All are reversible pairs, and can establish redox balance at the moment of reaction, thereby obtaining accurate measurement results.

It is to be understood that the present embodiment using the ceric sulfate solution as the standard solution of the oxidizing agent is merely exemplary, and those skilled in the art will understand that other oxidizing agents capable of achieving the technical effects of the present invention may also be used, for example, potassium permanganate may be used in the absence of the influence of the chelating agent.

Illustratively, in the step S4, the volume V of the second oxidant standard solution consumed when the redox potential is at the second jump is obtained₃The method comprises the following steps:

step S41: during the titration of the solution to be detected with a second oxidant standard solution, drawing an E-V curve and/or a delta E/delta V-V curve relating to the redox potential;

step S42: obtaining a second titration jump point from the E-V curve and/or the delta E/delta V-V curve of the oxidation-reduction potential, wherein the second titration jump point is the maximum point of the change rate of the oxidation-reduction potential or the highest point in the delta E/delta V-V curve, and the volume of the second titration jump point is the volume V of the second oxidant standard solution when the change of the oxidation-reduction potential is the fastest₃。

Referring to fig. 2 and 3, schematic diagrams of an E-V curve and a Δ E/Δ V-V curve, respectively, obtained in one embodiment according to the present invention are shown. Wherein, in FIG. 2, the curve shown in section B1 represents an E-V curve in which the oxidation-reduction potential is obtained in step S4, wherein the potential changes with the volume change of the oxidant standard solution dropped, wherein the point at which the slope of the change in potential is the maximum is the titration jump point, and the volume V of the oxidant standard solution corresponding to the maximum slope point is the volume V of the oxidant standard solution₃Volume V of standard solution of the oxidant at the time of sudden change of oxidation-reduction potential value₃. To further obtain an accurate titration jump point, a Δ E/Δ V-V curve is constructed according to FIG. 2, as shown in FIG. 3, where B₂Segment shows a diagram corresponding to B in FIG. 2₁A plot of Δ E/Δ V-V of the segment with respect to oxidation-reduction potential showing a trend of a slope of the potential change with the volume of dropping of the oxidizer standard solution, wherein the volume V of the oxidizer standard solution corresponding to the maximum value of the slope₃Volume V of standard solution of the oxidant at the time of sudden change of oxidation-reduction potential value₃。

Illustratively, in the step S4, during the titration of the solution to be detected with the second standard solution of the oxidizing agent, an excess amount of the second standard solution of the oxidizing agent is dropped. As in step S2, an excessive amount of the second oxidant standard solution is added to ensure that the second oxidant completely reacts with the reducing agent and persulfate ions in the detection solution, so that the obtained E-V curve and Δ E/Δ V-V curve have definite potential jump points, thereby obtaining an accurate detection result.

As shown in fig. 2 and 3, in one example according to the present invention, an excess amount of the second oxidant standard solution is dropped to V₃₁. Illustratively, as the second oxidant standard solution, a ceric sulfate standard solution in which the concentration of the ceric sulfate standard solution is in the range of 0.01mol/L to 0.5mol/L was dropped, an excess amount of the oxidant standard solution was dropped, and the amount of the oxidant standard solution dropped at this time was recorded as V₃₁。V₃₁-V₃In the range of 2ml to 5 ml.

Next, with continued reference to fig. 1, step S5 is performed: and respectively calculating the molar concentrations of the hydrogen peroxide and the persulfate in the solution to be detected.

Wherein the molar concentration of hydrogen peroxide in the solution to be detectedWherein m is an equivalent coefficient representing the number of moles of hydrogen peroxide reacted with a unit number of moles of the reducing agent.

The equivalent weight coefficient is determined according to the type of the oxidant.

In one example according to the present invention, a ceric sulfate solution is used as an oxidant standard solution and ammonium ferrous sulfate is used as a reducing agent, and the equivalent coefficient m is 2.

The molar concentration of persulfate in the solution to be detected

Wherein l, n and w are equivalent coefficients representing the number of moles of the first oxidizing agent, the number of moles of the persulfate, and the number of moles of the second oxidizing agent, respectively, that react with a unit number of moles of the reducing agent.

In one example according to the present invention, the first standard solution of oxidizer is the same as the second standard solution of oxidizer, i.e. C₁＝C₃，l＝w。

The equivalent weight coefficient is determined according to the kinds of the oxidizing agent and the reducing agent.

In one example according to the present invention, ceric sulfate solution is used as the first and second oxidant standard solution and ammonium ferrous sulfate is used as the reducing agent, the equivalent coefficient is 1-w, and the equivalent coefficient n is 2.

The above is an exemplary process diagram for testing soil as a sample to be tested according to one example of the present invention. It should be understood that the types, amounts and volumes of the reducing agent and the oxidizing agent are merely examples, and those skilled in the art may make other selections as needed in the specific implementation process, and are not limited herein.

According to one example of the inventive method, the inventive method is validated for checking the accuracy of the inventive method. Specifically, reagent grade hydrogen peroxide and sodium persulfate were taken and prepared as a solution of 82.5mmol/L hydrogen peroxide and 44.1mmol/L sodium persulfate, and the method described in the above examples was followed for verification.

Specifically, first, 50mL of deionized water was aspirated into a 250mL Erlenmeyer flask. Adding 1mL of liquid to be tested, shaking up, adding 2mL +/-0.5 mL of 6mol/L sulfuric acid solution, titrating with 0.0792mol/L ceric sulfate standard solution, recording the oxidation-reduction potential value of the system, and drawing an E-V curve or a delta E/delta V-V curve. A titration jump is obtained. Record the volume of titration jump V₁(2 mean of parallel samples)) It was 2.10 mL.

Then, 10ml of 0.1mol/L ferrous ammonium sulfate hexahydrate solution is added into the solution obtained in the step. The redox potential of the solution was stabilized at 437mv (≦ 500 mv). Then titrating by using a ceric sulfate standard solution with the concentration of 0.0792mol/L, recording the oxidation-reduction potential value of the system, and drawing an E-V curve or a delta E/delta V-V curve. Obtaining a titration jump point, the volume V of the ceric sulfate solution consumed by the titration jump point₃(mean of 2 parallel runs) was 13.65 mL. The measured concentrations of hydrogen peroxide and sodium persulfate obtained by the final calculation were compared with the theoretical concentrations obtained by the configuration as shown in the following table:

as can be seen from the table, the method of the invention can simultaneously and accurately detect the contents of hydrogen peroxide and sodium persulfate in the solution, and further proves that the method of the invention can simultaneously and accurately measure the contents of hydrogen peroxide and sodium persulfate in the underground water in the environmental remediation engineering.

The present invention has been illustrated by the above embodiments, but it should be understood that the above embodiments are for illustrative and descriptive purposes only and are not intended to limit the invention to the scope of the described embodiments. Furthermore, it will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, and that many variations and modifications may be made in accordance with the teachings of the present invention, which variations and modifications are within the scope of the present invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.