Novel method for rapidly enriching heavy metal ions in water by using confined water

Abstract

The invention discloses a novel method for rapidly enriching heavy metal ions in water by using confined water, and belongs to the technical field of separation and analysis detection, the method comprises the following steps: S1, preparing carbon nanofiber / carbon fiber; s2, loading the carbon nanofiber / carbon fiber obtained in the step S1, and preparing a needle tip device; s3, heavy metal ions in the solution are extracted through the needle point device liquid phase sodium obtained in the S2. According to the novel method for rapidly enriching the heavy metal ions in the water through the confined water, carbon nanofibers / carbon fibers are prepared through a vapor deposition method, the water is confined in a nanometer space, the heavy metal ions in the water are extracted through the confined water, desorption is conducted through the complexing effect of the heavy metal ions and EDTA, and the heavy metal ions are enriched in the water. Green, non-toxic, simple and convenient to operate, rapid and efficient heavy metal ion extraction and enrichment are realized.

Description

Technical Field

[0001] The present invention relates to the technical field of separation and analysis detection, and in particular to a new method for rapidly enriching heavy metal ions in water by "confined water". Background Art

[0002] The monitoring of heavy metal ions in water is not only related to the health of the people, but also related to the national development strategy, and even more related to China's international status. At present, the development of single water detection instruments at home and abroad is relatively mature, but the instruments for online simultaneous detection of various pollutants in water are almost invisible. It is urgent to develop from conventional laboratory offline detection to online on-site detection. In recent years, the emerging sensing technology has made the analysis of heavy metal ions develop in the direction of portability, lightness and simplification, but it also faces the bottleneck of current technology and needs to make a substantial breakthrough. The low content, variety and serious matrix interference of heavy metal elements in water have a great impact on the detection accuracy. How to achieve green and efficient enrichment and rapid detection of trace heavy metal ions is the key.

[0003] Common enrichment techniques for heavy metal ions in water, such as solid-phase microextraction, solid-phase extraction, liquid-liquid extraction, etc., have obvious deficiencies in trace heavy metal analysis, especially in-situ, online and real-time analysis due to their low mass transfer efficiency and extraction capacity. Summary of the Invention

[0004] The purpose of the present invention is to provide a new method for rapidly enriching heavy metal ions in water by "confined water", realizing stable and controllable droplet manipulation of liquid-phase extraction technology, maximizing the contact probability between the target substance and the extraction phase, and realizing rapid, high-throughput and high-enrichment microextraction of heavy metals in water.

[0005] To achieve the above purpose, the present invention provides a new method for rapidly enriching heavy metal ions in water by "confined water", comprising the following steps:

[0006] S1. Prepare carbon nanofiber / carbon fiber;

[0007] S2. Load the carbon nanofiber / carbon fiber obtained in S1 to prepare a tip device;

[0008] S3. Use the tip device obtained in S2 to liquid-phase nano-extract heavy metal ions in the solution.

[0009] Preferably, S1 comprises the following steps:

[0010] S11. Pretreat the carbon fiber to obtain acidified carbon fiber;

[0011] S12. Immerse the acidified carbon fiber in the catalyst solution for 10 - 14 h to obtain the second carbon fiber. Connect a pump, a suction flask, and a Buchner funnel. Place a filter membrane on the Buchner funnel. Cut the second carbon fiber into pieces 3 - 4 cm long to obtain the third carbon fiber, and then place it on the filter membrane. Rinse the third carbon fiber with the catalyst solution. After the third carbon fiber is completely dispersed, filter it until it is nearly dry, take it out and dry it at room temperature to obtain the deposited carbon fiber;

[0012] S13. Prepare carbon nanofiber / carbon fiber from the deposited carbon fiber by chemical vapor deposition.

[0013] Preferably, the specific steps of S11 are as follows:

[0014] S111. Wind the carbon fiber around a self-made stainless steel frame, put it into a quartz boat, and calcine it at a high temperature using a tube furnace or a muffle furnace. The heating rate of the high-temperature calcination is 3 - 10 °C / min, the temperature is 450 - 500 °C, and the time is 30 - 60 min to obtain the first carbon fiber;

[0015] S112. Immerse the first carbon fiber in a concentrated nitric acid / sulfuric acid solution at normal temperature and pressure for 10 - 14 h, and then repeatedly extract it with ultrapure water until the surface is neutral. Then place it in an oven to dry. The drying temperature is 40 - 60 °C, and the drying time is 1 - 3 h to obtain the acidified carbon fiber;

[0016] Among them, the volume ratio of concentrated nitric acid to concentrated sulfuric acid in the concentrated nitric acid / sulfuric acid solution is 1:3.

[0017] Preferably, in S12, the specific operation for preparing the catalyst solution is as follows: Add tetraethyl orthosilicate, P123, H 2 O, ethanol, hydrochloric acid, and nickel nitrate successively according to the molar ratio of 1:(0.01 - 0.011):(9.2 - 9.4):(20 - 22):(0.01 - 0.1):(0.1 - 1). After adding, stir at a speed of 400 - 450 rpm / min at room temperature for 10 - 12 h.

[0018] Preferably, the specific steps of S13 are as follows:

[0019] S131. Place the deposited carbon fiber horizontally on a quartz boat, and calcine it at a high temperature using a tube furnace or a muffle furnace. The temperature of the high-temperature calcination is 450 - 500 °C, the heating rate is 3 - 10 °C / min, and the time is 30 - 60 min to obtain the fourth carbon fiber;

[0020] S132. Place the fourth carbon fiber horizontally on the quartz boat, put it in a tube furnace, use nitrogen as the protective gas, heat it to 550 - 650 °C at a rate of 3 - 10 °C / min, first introduce hydrogen for high-temperature calcination, then introduce acetylene gas for high-temperature calcination, the total time of high-temperature calcination is 1 - 3 h, and after the reaction is completed, cool it to room temperature to obtain carbon nanofiber / carbon fiber.

[0021] Preferably, S2 includes the following steps:

[0022] S21. Immerse the carbon nanofiber / carbon fiber obtained in S1 in methanol and ultrasonicate it. After ultrasonication, pick up the ultrasonated carbon nanofiber / carbon fiber with tweezers, and rinse it with a methanol wash bottle, then place it in an oven and dry it at 70 °C for 5 min to obtain the first carbon nanofiber / carbon fiber;

[0023] S22. Weigh the original weight of the first carbon nanofiber / carbon fiber as A mg using a ten-thousandth balance. Using tweezers and scissors, strip 50 - 60 carbon nanofibers / first carbon fibers, weigh the remaining fibers as B mg, and calculate the weight of the stripped fibers as C mg, where C is 0.6 - 1.0 mg;

[0024] S23. Infiltrate the stripped first carbon nanofiber / carbon fiber with methanol to make it aggregate into clusters, pick it up with tweezers and slowly insert it into the tip of the needle for loading. After loading, screw the tip back onto the microsyringe to obtain the tip device.

[0025] Preferably, S3 includes the following steps:

[0026] S31. Push ultrapure water out of the tip of the tip device prepared in S2 for confinement;

[0027] S32. Use a micro peristaltic pump to push the heavy metal ion solution through the tip to extract heavy metal ions;

[0028] S33. Use a micro peristaltic pump to push the EDTA desorption solution through the tip to complete desorption.

[0029] Preferably, in S32 and S33, the extraction time and desorption time are both 5 s - 5 min.

[0030] Preferably, in S32, the heavy metal ion in the heavy metal ion solution is one of Cu 2+ 、Cd 2+ 、Pb 2+ 、Zn 2+ 、Fe 3+ 、Fe 2+ and its concentration is 50 - 2500 ng / mL.

[0031] Preferably, in S33, the concentration of the EDTA desorption solution is 0.1 - 0.2 mM.

[0032] Therefore, the present invention adopts the above-mentioned new method for rapidly enriching heavy metal ions in water by "confined water". With the help of chemical vapor deposition, carbon nanofibers / carbon fibers are prepared, and water is successfully confined in the nano-space. The heavy metal ions in water are extracted by the confined water and desorbed by the complexation of heavy metal ions with EDTA, realizing the extraction and enrichment of heavy metal ions that are green, non-toxic, simple to operate, fast and efficient.

[0033] The technical solution of the present invention will be further described in detail below with reference to the drawings and embodiments. Description of the Drawings

[0034] Figure 1 It is the confined water extraction of Cu by the tip device in the embodiment of the new method for rapidly enriching heavy metal ions in water by "confined water" of the present invention 2+ Graph of the recovery rate varying with the sample concentration. Detailed Embodiments

[0035] The technical solution of the present invention will be further described below with reference to the drawings and embodiments.

[0036] Unless otherwise defined, the technical terms or scientific terms used in the present invention shall have the ordinary meanings understood by those of ordinary skill in the field to which the present invention belongs.

[0037] Example 1

[0038] A new method for rapidly enriching heavy metal ions in water by "confined water" includes the following steps:

[0039] S1. Prepare carbon nanofibers / carbon fibers, specifically including the following steps:

[0040] S11. Pretreat carbon fibers to obtain acidified carbon fibers, specifically including the following steps:

[0041] S111. Wind 60 cm of carbon fibers around a self-made stainless steel frame, place them in a quartz boat, and calcine them at a high temperature in a muffle furnace. Raise the temperature to 450 °C at a rate of 5 °C / min and hold for 30 min to obtain the first carbon fibers.

[0042] S112. Immerse the first carbon fibers in a concentrated nitric acid / sulfuric acid solution at normal temperature and pressure for 12 h, then repeatedly extract with ultrapure water until the surface is neutral, and then dry in an oven at 40 °C for 2 h to obtain acidified carbon fibers;

[0043] Among them, the volume ratio of concentrated nitric acid to concentrated sulfuric acid in the concentrated nitric acid / sulfuric acid solution is 1:3.

[0044] S12. Immerse the acidified carbon fiber in the catalyst solution for 12 h to obtain the second carbon fiber. Connect a pump, a suction flask, and a Buchner funnel. Place a filter membrane on the Buchner funnel. Cut the second carbon fiber into 3 cm to obtain the third carbon fiber, and then place it on the filter membrane. Rinse the third carbon fiber with the catalyst solution. After the third carbon fiber is completely dispersed, filter it until it is nearly dry, take it out and dry it at room temperature to obtain the deposited carbon fiber;

[0045] The specific operation for preparing the catalyst solution is as follows: Add tetraethyl orthosilicate, P123, H 2 O, ethanol, hydrochloric acid, and nickel nitrate successively in a molar ratio of 1:(0.0103):(9.36):(21.4):(0.04):(0.4). After adding, stir at a speed of 400 rpm / min at room temperature for 12 h.

[0046] S13. Prepare carbon nanofiber / carbon fiber by chemical vapor deposition, which specifically includes the following steps:

[0047] S131. Place the deposited carbon fiber horizontally on a quartz boat and calcine it at a high temperature in a muffle furnace. Heat it to 450 °C at a heating rate of 5 °C / min and hold for 30 min to obtain the fourth carbon fiber.

[0048] S132. Place the fourth carbon fiber horizontally on a quartz boat and place it in the center of a tube furnace. Pass 155 cc / min of nitrogen as a protective gas. After heating to 600 °C at a rate of 5 °C / min, first pass 25 cc / min of hydrogen and calcine at a high temperature for 30 min, then pass acetylene gas and calcine at a high temperature for 30 min. After the reaction is completed, cool it to room temperature to obtain carbon nanofiber / carbon fiber.

[0049] S2. Load the carbon nanofiber / carbon fiber obtained in S1 and prepare a tip device, which specifically includes the following steps:

[0050] S21. Immerse the carbon nanofiber / carbon fiber obtained in S1 in methanol and ultrasonicate it at the lowest energy for 5 min. Pick up the ultrasonically treated carbon nanofiber / carbon fiber with tweezers, rinse it with a methanol wash bottle, and then dry it in an oven at 70 °C for 5 min to obtain the first carbon nanofiber / carbon fiber.

[0051] S22. Weigh the original weight of the first carbon nanofiber / carbon fiber with an analytical balance of one ten-thousandth as 2.0 mg. Use tweezers and scissors to peel off 50 first carbon nanofibers / carbon fibers, weigh the remaining fibers as 1.2 mg, and calculate the weight of the peeled-off fibers as 0.8 mg.

[0052] S23. Infiltrate the peeled-off carbon nanofiber / first carbon fiber with methanol to make it aggregate into clusters. Pick it up with tweezers and slowly insert it into the tip for loading. After loading is completed, screw the tip back onto the microsyringe to obtain the tip device.

[0053] S3. Use the needle tip device obtained in S2 to liquid-phase extract heavy metal ions from the solution, which specifically includes the following steps:

[0054] S31. Push out 100 μL of ultrapure water from the needle tip of the needle tip device prepared in S2 for confinement;

[0055] S32. Use a micro peristaltic pump to push a 500 ng / mL Cu 2+ solution through the needle tip to extract Cu 2+ , and the extraction time is 30 s;

[0056] S33. Use a micro peristaltic pump to push a 0.1 mM EDTA desorption solution through the needle tip to complete desorption, and the desorption time is 30 s.

[0057] Example 2

[0058] The difference between Example 2 and Example 1 is that the concentration of the Cu 2+ solution is 50 ng / mL.

[0059] Example 3

[0060] The difference between Example 3 and Example 1 is that the concentration of the Cu 2+ solution is 100 ng / mL.

[0061] Example 4

[0062] The difference between Example 4 and Example 1 is that the concentration of the Cu 2+ solution is 250 ng / mL.

[0063] Example 5

[0064] The difference between Example 5 and Example 1 is that the concentration of the Cu 2+ solution is 1000 ng / mL.

[0065] Example 6

[0066] The difference between Example 6 and Example 1 is that the concentration of the Cu 2+ solution is 1500 ng / mL.

[0067] Example 7

[0068] The difference between Example 7 and Example 1 is that the concentration of the Cu 2+ solution is 2000 ng / mL.

[0069] Example 8

[0070] The difference between Example 8 and Example 1 is that the concentration of the Cu 2+The solution concentration is 2500 ng / mL.

[0071] Example Nine

[0072] The difference between Example Nine and Example One is that the extraction time is 20 s.

[0073] Example Ten

[0074] The difference between Example Ten and Example One is that the heavy metal ion solution is Cd 2+ solution, and the extraction time is 20 s.

[0075] Example Eleven

[0076] The difference between Example Eleven and Example One is that the heavy metal ion solution is Pb 2+ solution, and the extraction time is 20 s.

[0077] Example Twelve

[0078] The difference between Example Twelve and Example One is that the heavy metal ion solution is Zn 2+ solution, and the extraction time is 20 s.

[0079] Example Thirteen

[0080] The difference between Example Thirteen and Example One is that the heavy metal ion solution is Fe 3+ solution, and the extraction time is 20 s.

[0081] Example Fourteen

[0082] The difference between Example Fourteen and Example One is that the heavy metal ion solution is Fe 2+ solution, and the extraction time is 20 s.

[0083] The content of heavy metal ions in the desorbing solution was analyzed by HPLC-MS / MS, and the recovery rate was calculated according to the following formula:

[0084] R = C / C 0 × 100%;

[0085] where R is the recovery rate, %; C is the content of heavy metal ions in the desorbing solution, ng / mL; C 0 is the initial content of heavy metal ions, ng / mL.

[0086] Compare the Cu 2+ recovery rates of the tip device-confined water extraction of Cu 2+ under different initial concentrations in Examples One to Eight. The results are as Figure 1 shown. It can be seen from Figure 1 that Cu 2+When the concentration is 50 - 2500 ng / mL, the recovery rate can reach over 83%, and the RSD < 15%. The upper limit of the linear range of this method is 2500 ng / mL, so the maximum concentration of heavy metal ions is 2500 ng / mL.

[0087] Compare the extraction effects of different heavy metal ions in Examples 9 to 14. When the extraction time is 20 s, for Cu 2+ , Cd 2+ , Pb 2+ , Zn 2+ , Fe 3+ , Fe 2+ , the recovery rates are 43.93 - 98.27%, and the RSD < 8%. Among them, the tip device has the best extraction effect on Zn 2+ , with a recovery rate of 98.27%, and the worst extraction effect on Fe 2+ , with a recovery rate of 43.93%. This shows that the tip device liquid-phase nanoextraction method has good extraction effects on Cu 2+ , Cd 2+ , Pb 2+ , Zn 2+ , Fe 3+ , Fe 2+ and can be widely used in the detection of heavy metal ions.

[0088] Therefore, the present invention adopts the above-mentioned new method for rapidly enriching heavy metal ions in water by "confined water", realizes the stable and controllable manipulation of liquid droplets in liquid-phase extraction technology, maximizes the contact probability between the target substance and the extraction phase, and realizes the rapid, high-throughput, and high-enrichment microextraction of heavy metals in water.

[0089] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions of the present invention or make equivalent replacements, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A new method for rapid enrichment of heavy metal ions in water by "confined water", characterized in that: The following steps are involved: S1. preparing carbon nanofibers / carbon fibers; S2, loading the carbon nanofiber / carbon fiber obtained in S1 to prepare a needle tip device; S3. Use the needle tip device obtained in S2 to extract heavy metal ions in the solution using liquid phase nano-extraction.

2. The method according to claim 1, characterized in that S1 includes the following steps: S11, pretreating carbon fiber to obtain acidified carbon fiber; S12, immersing the acidified carbon fiber in the catalyst solution for 10-14h to obtain a second carbon fiber, connecting a pump, a suction filtration bottle and a Buchner funnel, placing a filter membrane on the Buchner funnel, cutting the second carbon fiber into 3-4cm to obtain a third carbon fiber, and then placing it on the filter membrane, eluting the third carbon fiber with the catalyst solution, and after the third carbon fiber is completely dispersed, filtering it to a nearly dry state, taking it out and drying it at room temperature to obtain a deposited carbon fiber; S13. Prepare carbon nanofibers / carbon fibers by depositing carbon fibers through chemical vapor deposition.

3. The method according to claim 2, characterized in that S11 specific steps are as follows: S111, winding the carbon fiber on a self-made stainless steel frame, putting it into a quartz boat, and calcining it at high temperature in a tube furnace or a muffle furnace, wherein the heating rate of the high temperature calcination is 3-10°C / min, the temperature is 450-500°C, and the time is 30-60min, to obtain a first carbon fiber; S112, at room temperature and pressure, immersing the first carbon fiber in a concentrated nitric acid / sulfuric acid solution for 10-14 hours, then repeatedly leaching with ultrapure water until the surface is neutral, and drying in an oven at a drying temperature of 40-60° C. for a drying time of 1-3 hours to obtain an acidified carbon fiber; Wherein, the volume ratio of concentrated nitric acid to concentrated sulfuric acid in the concentrated nitric acid / sulfuric acid solution is 1:

3.

4. The method according to claim 2, characterized in that: In S12, the specific operation of preparing the catalyst solution is: add tetraethyl orthosilicate, P123, H2O, ethanol, hydrochloric acid, and nickel nitrate in a molar ratio of 1:(0.01-0.011):(9.2-9.4):(20-22):(0.01-0.1):(0.1-1) successively, and after adding, stir at room temperature at a speed of 400-450 rpm / min for 10-12 hours.

5. The method according to claim 2, characterized in that: The specific steps of S13 are as follows: S131, placing the deposited carbon fiber horizontally on a quartz boat, and calcining it at high temperature in a tube furnace or a muffle furnace, wherein the high temperature calcination temperature is 450-500° C., the heating rate is 3-10° C. / min, and the time is 30-60 min, to obtain a fourth carbon fiber; S132. Place the fourth carbon fiber horizontally on a quartz boat, place it in a tubular furnace, use nitrogen as a protective gas, heat it to 550-650°C at a rate of 3-10°C / min, first introduce hydrogen for high-temperature calcination, then introduce acetylene gas for high-temperature calcination. The total high-temperature calcination time is 1-3h. After the reaction is completed, cool it to room temperature to obtain carbon nanofibers / carbon fibers.

6. The method according to claim 1, characterized in that S2 includes the following steps: S21, immersing the carbon nanofiber / carbon fiber obtained in S1 in methanol and ultrasonicating it. After the ultrasonication, the carbon nanofiber / carbon fiber after ultrasonication is picked up with tweezers, rinsed with a methanol washing bottle, and then dried in an oven at 70° C. for 5 min to obtain a first carbon nanofiber / carbon fiber; S22, using a 1 / 10,000 balance to weigh the original weight of the first carbon nanofiber / carbon fiber as A mg, using tweezers and scissors to peel off 50-60 carbon nanofibers / first carbon fibers, weighing the remaining fibers as B mg, and calculating the weight of the peeled fibers as C mg, where C is 0.6-1.0 mg; S23. Soak the peeled first carbon nanofiber / carbon fiber with methanol to aggregate it into clusters, pick it up with tweezers and slowly insert it into the needle tip for loading. After loading, screw the needle tip back onto the micro-syringe to obtain a needle tip device.

7. The method according to claim 1, characterized in that S3 includes the following steps: S31, pushing ultrapure water out from the needle tip of the needle tip device prepared in S2 for confinement; S32, using a micro peristaltic pump to push the heavy metal ion solution through the needle tip to extract the heavy metal ions; S33. Use a micro peristaltic pump to push the EDTA desorption solution through the needle tip to complete the desorption.

8. The method according to claim 7, characterized in that In S32 and S33, the extraction time and desorption time are both 5s-5min.

9. The method according to claim 7, characterized in that: In S32, the heavy metal ion in the heavy metal ion solution is Cu 2 + 、Cd 2+ , Pb 2+ 、Zn 2+ , Fe 3+ , Fe 2+ One of the above, with a concentration of 50-2500ng / mL.

10. The method according to claim 7, characterized in that In S33, the concentration of EDTA desorption solution is 0.1-0.2 mM.

Images