CN109092455B

CN109092455B - Method for degrading endosulfan by mechanochemical method

Info

Publication number: CN109092455B
Application number: CN201810860381.9A
Authority: CN
Inventors: 乔维川; 葛秀秀
Original assignee: Nanjing Forestry University
Current assignee: Nanjing Forestry University
Priority date: 2018-07-31
Filing date: 2018-07-31
Publication date: 2020-10-16
Anticipated expiration: 2038-07-31
Also published as: CN109092455A

Abstract

The invention discloses a method for degrading endosulfan by adopting a mechanochemical method, which comprises the steps of adding endosulfan or a substance containing endosulfan and an abrasive into a ball mill, and carrying out ball milling for more than 15min to realize degradation of endosulfan; wherein the ball milling rotation speed is 400-600 rpm, the material ratio is 15-20: 1, the ball mill rotates 30min and then reversely rotates 30min, and the steps are repeated. The invention uses CaO and MgO separately, the degradation efficiency of the ball milling for half an hour to the endosulfan is as high as 96% and above; ball milling is carried out for 15min under the conditions of material ratio of 20: 1, ball material ratio of 20: 1 and rotation speed of 500rpm, the degradation rate reaches 70%, and the content of endosulfan in the soil is degraded from 3451.042mg/kg to 1043 mg/kg. After ball milling for 120min, the content of the endosulfan in the soil is degraded to 430.6mg/kg of soil, the degradation rate is 85.62%, and a good practical application effect is obtained.

Description

Method for degrading endosulfan by mechanochemical method

Technical Field

The invention relates to the technical field of endosulfan degradation, in particular to a method for degrading endosulfan by adopting a mechanochemical method.

Background

Endosulfan (C)₉H₆Cl₆O₃S) is 1, 4, 5, 6, 7, 7-hexachloro-9, 9, 10-trinitrogen-5-ene-2, 3-ylidene dimethylene, which is also known as thiodan and captan, has a relative molecular mass of 406.91, is sulfite and has two isomers, namely α -thiodan and β -thiodan respectively, the ratio of α -thiodan to β -thiodan is about 7: 3, and the structural formula is shown as follows:

endosulfan (Pollutants) is a novel Persistent Organic Pollutant (POPs) containing chlorine and sulfur elements, and causes Persistent harm and pollution to water, atmosphere and soil environment in the production and use processes of the Endosulfan. The endosulfan is stable in property and not easy to photolyze, and the half-life period of the endosulfan is 1-3 months. Furthermore, the degradation product of endosulfan, has a half-life of even several years to several decades, and is more toxic than endosulfan. Although the production and use of endosulfan are prohibited by united nations in 2012, endosulfan and derivatives thereof remaining in soil and water can still cause harm to human health for a long time.

At present, many scholars at home and abroad have quite mature researches on the biodegradation and mechanism of the endosulfan, but the biodegradation can realize the desulfurization effect but cannot achieve the aim of dechlorination from the existing research results, and the products of the biodegradation of the endosulfan are chlorine-containing organic compounds and still have harm to the environment.

The mechanochemical method is to mix dehalogenation and desulfurization agents and target pollutants in a certain proportion in a reactor, and when mechanical energy is applied, the form, crystal structure, physical and chemical properties and the like of a solid mixture are changed, and a physical and chemical reaction is induced, so that the pollutants are degraded. At present, many studies prove the high efficiency of degrading chlorine-containing organic matters by a mechanochemical method. In many studies, the researchers only ball mill the chlorine-containing refractory organic substances, but the study on the mechanochemical degradation of the chlorine-and sulfur-containing organic substances is still relatively rare.

Disclosure of Invention

The purpose of the invention is as follows: aiming at the defects in the prior art, the invention aims to provide a method for degrading endosulfan by adopting a mechanochemical method, develop a new process for degrading endosulfan and provide important theoretical guidance for subsequent engineering application.

The technical scheme is as follows: in order to achieve the purpose of the invention, the invention adopts the technical scheme that:

a method for degrading endosulfan by mechanochemical method comprises adding endosulfan or endosulfan-containing substance and abrasive into ball mill, ball milling for more than 15min, rotating the ball mill for 30min, then immediately rotating the ball mill reversely for 30min, repeating the above steps to realize endosulfan degradation; wherein the ball milling rotation speed is 400-600 rpm, the material ratio is 15-20: 1, and the ball material ratio is 15-20: 1; the grinding agent is CaO, MgO, a mixture of CaO and Fe, or a mixture of MgO and Fe.

The method for degrading endosulfan by adopting a mechanochemical method has the ball milling rotating speed of 500 rpm.

The method for degrading endosulfan by adopting a mechanochemical method has the material ratio of 20: 1.

The method for degrading endosulfan by adopting a mechanochemical method has the ball-material ratio of 20: 1.

The ball milling time is more than 30min by adopting the method for degrading endosulfan by adopting the mechanochemical method.

The method for degrading endosulfan by adopting the mechanochemical method is characterized in that iron balls used for ball milling consist of big balls and small balls, wherein the mass ratio of the big balls to the small balls is 1: 1, the diameter of the big balls is 10mm, and the diameter of the small balls is 5 mm.

The method for degrading endosulfan by adopting a mechanochemical method is characterized in that the endosulfan-containing substance is soil polluted by endosulfan.

The method for degrading endosulfan by adopting a mechanochemical method is characterized in that the grinding agent is CaO.

Has the advantages that: compared with the prior art, the invention adopts a mechanochemical method to degrade the endosulfan, and has the following advantages:

1) the CaO and MgO are used independently, the degradation efficiency of the ball milling for half an hour to the endosulfan is up to 96 percent or more, and the CaO is superior to the MgO along with the increase of the ball milling time.

2) The optimal ball milling process conditions are established, namely the material ratio is 20: 1, the ball-material ratio is 20: 1, the rotating speed is 500rpm, and the degradation rate of the ball milling for 1 hour on the endosulfan is close to 100 percent.

3) Ball milling is carried out for 15min at the material ratio (the mass ratio of CaO to endosulfan is 20: 1) and the ball-material ratio is 20: 1 at the rotating speed of 500rpm, the degradation rate reaches 70 percent, and the endosulfan content in the soil is degraded from 3451.042mg/kg to 1043 mg/kg. After ball milling for 120min, the content of the endosulfan in the soil is degraded to 430.6mg/kg of soil, the degradation rate is 85.62%, and a good practical application effect is obtained.

Drawings

FIG. 1 is a graph showing the results of the degradation rate of endosulfan over a period of 30min for various abrasives;

FIG. 2 is a graph of endosulfan degradation rate as a function of feed ratio;

FIG. 3 is a graph of endosulfan degradation rate as a function of pellet-to-feed ratio;

FIG. 4 is a graph of endosulfan degradation rate as a function of rotational speed;

FIG. 5 is a graph of endosulfan degradation rate in contaminated soil as a function of time.

Detailed Description

The present invention will be further described with reference to the following specific examples. The main detection and analysis methods used in the following examples are as follows:

and (3) detecting the residual amount of endosulfan: and (3) putting about 0.1000g of ball-milled product into a 10mL centrifuge tube, adding 8mL of acetone, fully mixing, putting into an ultrasonic cleaner for ultrasonic treatment for 20min, centrifuging at 6000rpm for 15min, pouring the supernatant into a test tube, and sealing. An additional 8mL of acetone was added to the solid residue and the two supernatants were combined after the same sonication centrifugation extraction procedure. 1mL of supernatant is taken and blown to be dry by nitrogen, and 5mL of normal hexane is added for constant volume. And filtering the solution with constant volume into a brown sample injection vial through an organic microporous filter membrane with the diameter of 0.22 mu m, and placing the sample injection vial into a gas chromatograph for detection. All assay samples were in triplicate. The model of the gas chromatograph is Agilent-7890B GC-ECD, the model of the chromatographic column is Agileng HP-1(30m multiplied by 0.32mm multiplied by 0.25 mu m), the programmed temperature rise conditions are that the detector temperature is 280 ℃, the injection port temperature is 240 ℃, the injection bottle is 1ul, the initial temperature of the column box is 110 ℃, the temperature is kept for 1min, the temperature is increased to 180 ℃ at 20 ℃/min, the temperature is kept for 2min, the temperature is increased to 250 ℃ at 10 ℃/min, and the temperature is kept for 5 min.

In the following examples, the technical-grade endosulfan starting material used was a product of endosulfan manufacturing company, Jiangsu, and the measurement results of the specific components are shown in Table 1.

TABLE 1 results of the determination of the content of technical endosulfan

In the following examples, the material ratio refers to the ratio of the mass of the added abrasive to the mass of endosulfan; the ball material ratio is as follows: the mass of the added grinding balls is in proportion to the total mass of the ball-milling grinding agent and the endosulfan; the ball milling tank is made of stainless steel, and the iron balls are composed of big balls and small balls, wherein the mass ratio of the big balls to the small balls is 1: 1, the diameter of the big balls is 10mm, and the diameter of the small balls is 5 mm. The formula for calculating the degradation rate of endosulfan is as follows: the endosulfan degradation rate is (initial endosulfan amount-residual endosulfan amount)/initial endosulfan amount.

Example 1

A method for degrading endosulfan by adopting a mechanochemical method is characterized in that the ball milling rotating speed is 520rpm, and the material ratio is 20: 1, ball materialThe ratio is 20: 1, the mass of the iron ball is 120g, the ball mill rotates for 30min and then immediately rotates reversely for 30min, and the steps are repeated; after the ball milling is finished, determining the degradation rate of endosulfan; wherein the abrasive is CaO, MgO, SiO₂CaO and Fe powder in a mass ratio of 1 to 1, MgO and Fe powder in a mass ratio of 1 to 1, and SiO₂And (3) mixing Fe powder in a mass ratio of 1: 1, and ball milling for 30 min.

FIG. 1 is a comparison of degradation efficiency of various abrasives and different combinations thereof for 30min of endosulfan ball milling, and it can be seen from FIG. 1 that the degradation rate of MgO and CaO to endosulfan is the highest when ball milling is performed for 30min, the combination of iron powder, MgO and CaO (mass ratio 1: 1) is the second time, other efficiency is not more than 50%, and especially when Fe powder is added alone, the degradation efficiency of 120min of ball milling is not 40%. In the embodiment, when the ball milling speed is 520rpm and the ball milling time is 30min, the degradation rate of CaO on endosulfan is as high as 96%, so CaO is selected as the optimal grinding agent.

Example 2

A method for degrading endosulfan by adopting a mechanochemical method, which is the same as the example 1, wherein the grinding agent is CaO. 1) Ball milling rotation speeds are respectively 100rpm, 200rpm, 300rpm, 400rpm and 500rpm, 2) ball milling time is selected from 15min, 30min, 60min, 90min and 120min, and 3) material ratio is selected from 2: 1, 5: 1, 10: 1, 15: 1 and 20: 1; 4) the ball material ratio is 2: 1, 5: 1, 10: 1, 15: 1, 20: 1.

FIG. 2, FIG. 3 and FIG. 4 show the effect of different ball milling conditions on the degradation rate of endosulfan in 30min ball milling. The test process adopts a controlled variable method. As can be seen from the figure, the material ratio, the ball-material ratio and the rotating speed have great influence on the degradation rate of the endosulfan. Along with the increase of the material ratio, the ball-material ratio and the rotating speed, the degradation rate of the endosulfan is increased and shows a continuous rising trend. This indicates to some extent that high material to material ratio, high pellet to material ratio and high rotational speed can promote the degradation of endosulfan. The higher the material ratio, i.e. the higher the ratio of calcium oxide to endosulfan, the more chance of calcium oxide to endosulfan contact is increased, making the reaction more complete. In the embodiment, CaO is selected as a ball-milling grinding agent, the material ratio is 20: 1, the ball-material ratio is 20: 1, the rotating speed is 500rpm, the degradation rate of alpha-endosulfan reaches 72.25% in 30min, the degradation rate of beta-endosulfan reaches 85.69%, and the degradation rate of ball milling is close to 100% in 60min, so the optimal ball-milling conditions are selected to be the material ratio of 20: 1, the ball-material ratio of 20: 1 and the rotating speed of 500 rpm.

Example 3 degradation of endosulfan-containing soil test

The soil was taken from the hind hill of Nanjing university of forestry. Drying, grinding, sterilizing and drying the soil, sieving the soil by a 40-mesh sieve, adding the endosulfan raw drug, and measuring the residual endosulfan and calculating the endosulfan removal efficiency after ball milling treatment.

The ratio of the soil to the endosulfan raw drug is 100: 1, 1.0000g of endosulfan is dissolved in 50mL of acetone solution to prepare endosulfan-acetone solution with the concentration of 20 g/L; 50mL of endosulfan-acetone solution is uniformly sprinkled in 100g of pretreated soil, so that the endosulfan solution and the soil are fully and uniformly mixed. The acetone is volatilized until the soil is dried again by appropriate heating and stirring, and random sampling is carried out to measure the total content of the final endosulfan in the soil. Five groups of 10g of soil containing endosulfan are respectively taken, added with about 0.7g of CaO (the mass ratio of calcium oxide to endosulfan is 20: 1), added with 15g of steel balls (the mass ratio of big balls to small balls is 1: 1), the ball-material ratio is 20: 1, ball-milled for 15min, 30min, 60min, 90min and 120min, and the control group is added with the same amount of calcium oxide but is not ball-milled. And detecting the residual quantity of the endosulfan and calculating the degradation rate of the endosulfan. In order to avoid the influence of the volatilization of endosulfan in the heating and drying process on the test results, the content of endosulfan in the soil is re-detected before the test is started, and the detection results are shown in table 2.

TABLE 2 content of endosulfan in contaminated soil

And (3) putting about 0.1000g of ball-milled product into a 10mL centrifuge tube, adding 8mL of acetone, fully mixing, putting into an ultrasonic cleaner for ultrasonic treatment for 20min, centrifuging at 6000rpm for 15min, pouring the supernatant into a test tube, and sealing. 1mL of supernatant is taken and blown to be dry by nitrogen, and 2mL of normal hexane is added for constant volume. And filtering the solution with constant volume into a brown sample injection vial through an organic microporous filter membrane with the diameter of 0.2 mu m, and placing the sample injection vial into a gas chromatograph for detection. The model of the gas chromatograph is Agilent-7890B GC-ECD, the model of the chromatographic column is Agileng HP-1(30m multiplied by 0.32mm multiplied by 0.25 mu m), the temperature programming condition is that the detector temperature is 280 ℃, the injection port temperature is 240 ℃, the injection bottle is 1 mu l, the initial temperature of the column box is 110 ℃, the temperature is kept for 1min, the temperature is increased to 180 ℃ at 20 ℃/min, the temperature is kept for 2min, the temperature is increased to 250 ℃ at 10 ℃/min, and the temperature is kept for 5 min.

In the process of ball milling contaminated soil, the appearance and the color of a ball milling mixture are gradually changed along with the change of time, the color of the mixture is changed from yellow to gray before and after ball milling, and soil particles become very fine from the particles which can be seen by naked eyes.

The relationship of the degradation rate of the soil polluted by the endosulfan by the mechanochemical method along with the ball milling time is shown in fig. 5, and the degradation curve shows that the most rapid endosulfan degradation is the first 15min, the degradation rate reaches 70 percent, and the residual amount of the endosulfan is 1043 mg/kg. The degradation rate of endosulfan is increased continuously with the ball milling until the degradation rate of endosulfan in the soil reaches 85.62% after 60min of ball milling, and the degradation rate is almost unchanged. After ball milling for 120min, the content of the endosulfan in the soil is degraded from the original 3451.042mg/kg soil to 430.6mg/kg soil. The document of ' soil pollution risk screening value (trial) of soil pollution risk standard construction land (solicited comment draft) ' of the document issued by the ministry of environmental protection of china ' as loop soil content [2017]1385 specifies that the soil pollution risk screening value of the first type of land (sensitive land) is 234mg/kg, and the soil risk screening value of the second type of land (non-sensitive land) is 1687 mg/kg. According to the regulation of the method, when the soil polluted by the high-concentration endosulfan is degraded by a CaO mechanochemical method, the screening value of the soil pollution risk of the second land can be achieved by ball milling for 15 min.

Claims

1. A method for degrading endosulfan by adopting a mechanochemical method is characterized in that endosulfan and grinding agents are added into a ball mill together, the ball mill is milled for more than 30min, the ball mill rotates for 30min and then immediately rotates reversely for 30min, and the steps are repeated to realize the degradation of endosulfan; wherein the ball milling speed is 500rpm, the material ratio is 20: 1, and the ball material ratio is 20: 1; the iron balls used for ball milling consist of big balls and small balls, wherein the mass ratio of the big balls to the small balls is 1: 1, the diameter of the big balls is 10mm, and the diameter of the small balls is 5 mm; the grinding agent is CaO; the material ratio refers to the ratio of the mass of the added grinding agent to the mass of endosulfan; the ball material ratio is as follows: the mass of the added grinding balls is in proportion to the total mass of the ball-milling grinding agent and the endosulfan.