Method for efficiently separating mercuric sulfide nanoparticles and mercury ions

Abstract

The invention discloses a method for efficiently separating mercuric sulfide nanoparticles and mercury ions, and belongs to the technical field of adsorption materials. The method comprises the following steps: injecting aqueous dispersion mixed with mercuric sulfide nanoparticles (HgS NPs) and mercury ions (Hg < 2 + >) into a filter head, and filtering through a microporous filter membrane; enabling the HgS NPs to be intercepted on the filter membrane; the Hg < 2 + > passes through the microfiltration membrane to realize filtration; wherein the average particle size of the HgS NPs is less than 10nm; the microporous filter membrane is a nylon microporous filter membrane with the pore diameter of 0.22-0.45 [mu] m, and / or the microporous filter membrane is a nylon microporous filter membrane; the microporous filter membrane is a microporous filter membrane made of a polyvinylidene fluoride material, and the pore diameter of the microporous filter membrane is 0.22-0.45 mu m. According to the invention, efficient separation of HgS NPs and Hg < 2 + > can be realized, and especially separation of mercuric sulfide nanoparticles with a particle size of less than 10nm and mercury ions can be realized.

Description

Technical Field

[0001] The invention belongs to the technical field of adsorption materials, and more particularly relates to a method for efficiently separating mercury sulfide nanoparticles and mercury ions. Background Art

[0002] Mercury (Hg) is a global pollutant that poses a serious threat to the environment and human health due to its high toxicity, persistence and bioaccumulation. In the biogeochemical cycle of mercury, mercury exists in various forms, including ionic mercury (Hg 2+ ), methylmercury (MeHg) and mercury sulfide (HgS), among which HgS is traditionally considered to be an important form of mercury stored in the environment for a long time due to its low solubility and low mobility. However, the rapid development of nanotechnology in recent years has provided a new perspective for the study of the environmental behavior of mercury. The latest research results show that mercury sulfide nanoparticles (HgS NPs) can be methylated by microorganisms, and their methylation potential is similar to that of Hg 2+ HgS NPs in the environment may be directly methylated by microorganisms or release Hg 2+ Indirectly methylated by microorganisms. Effectively separate HgS NPs and Hg 2+ , which helps to clarify the microbial methylation mechanism of HgS NPs in different environments. More importantly, the dissolution, migration and transformation behavior of HgS NPs in the environment are closely related to their unique nano-properties. 2+ It is more helpful to study its environmental fate in depth. Therefore, it is possible to effectively separate and quantify HgS NPs and Hg 2+ It has important scientific significance.

[0003] Due to the nano-size characteristics of HgS NPs and Hg 2+ The strong adsorption of HgSNPs and Hg is difficult to be achieved by conventional filtration methods. 2+ Separation of HgS NPs and Hg 2+ The methods are mainly based on size exclusion chromatography (SEC) and ultrafiltration technology. Although SEC can separate according to particle size, it relies on expensive chromatographic equipment, the separation process is time-consuming, and the sample pretreatment requirements are high, which limits its application in large-scale environmental sample analysis. Although ultrafiltration technology is relatively simple to operate, the ultrafiltration membrane is prone to adsorb HgS NPs or Hg 2+ , resulting in reduced recovery and affecting the accuracy of quantitative results. These separation methods are complex and costly. Therefore, establishing a low-cost and efficient separation and quantification method is of great significance for promoting the study of the environmental behavior of HgS NPs. Summary of the Invention

[0004] 1. Problem to be solved

[0005] In view of the problem that existing mercury sulfide nanoparticles and mercury ions are difficult to separate efficiently, the present invention provides a method for efficiently separating mercury sulfide nanoparticles and mercury ions, which can achieve efficient separation of mercury sulfide nanoparticles and mercury ions.

[0006] 2. Technical solution

[0007] In order to solve the above problems, the technical solutions adopted by the present invention are as follows:

[0008] The present invention provides a method for efficiently separating mercuric sulfide nanoparticles and mercury ions, comprising the following steps:

[0009] The mixture of mercury sulfide nanoparticles (HgS NPs) and mercury ions (Hg 2+ ) is injected into the filter head and filtered through a microporous membrane;

[0010] Such that the HgS NPs are retained on the filter membrane;

[0011] The Hg 2+ Filtration is achieved through a microporous membrane;

[0012] wherein the HgS NPs have an average particle size of <10 nm;

[0013] The microporous filter membrane is a nylon microporous filter membrane with a pore size of 0.22 to 0.45 μm, and / or;

[0014] The microporous filter membrane is a polyvinylidene fluoride microporous filter membrane with a pore size of 0.22 to 0.45 μm.

[0015] According to any embodiment of the present invention, the HgS NPs are spherical particles having an average particle size of less than 10 nm, preferably, the average particle size of the spherical particles is 6 to 10 nm, and more preferably, the average particle size of the spherical particles is 6 to 8 mm.

[0016] According to any embodiment of the present invention, the nylon microporous filter membrane is composed of polyamide fiber, is hydrophilic, has a pore size range of 0.22 to 0.45 μm, and a porosity of 70% to 85%.

[0017] The retention rate of the HgS NPs on the microporous filter membrane is higher than 80% as measured by cold vapor atomic fluorescence spectroscopy;

[0018] The Hg 2+ Filtration is achieved through a microporous filter membrane, with a transmittance greater than 80% as measured by cold vapor atomic fluorescence spectroscopy.

[0019] Preferably, the nylon material can be nylon 6, or nylon 66, and more preferably nylon 6. Preferably, the pore size of the nylon microporous filter membrane is 0.22 μm, 0.45 μm, or any pore size between 0.22 μm and 0.45 μm, such as 0.25 μm, 0.3 μm, 0.35 μm, or 0.4 μm.

[0020] Preferably, the pore size of the nylon microporous filter membrane is 0.22 μm.

[0021] The retention rate of the HgS NPs on the microporous filter membrane is higher than 80% as measured by cold vapor atomic fluorescence spectroscopy;

[0022] The Hg 2+ Filtration is achieved by passing through a microporous filter membrane, and the transmittance is higher than 100% as measured by cold vapor atomic fluorescence spectroscopy.

[0023] Preferably, the pore size of the nylon microporous filter membrane is 0.45 μm.

[0024] The retention rate of the HgS NPs on the microporous filter membrane is higher than 90% as measured by cold vapor atomic fluorescence spectroscopy;

[0025] The Hg 2+ Filtration is achieved through a microporous filter membrane, with a transmittance greater than 80% as measured by cold vapor atomic fluorescence spectroscopy.

[0026] According to any embodiment of the present invention, the polyvinylidene fluoride microporous filter membrane is composed of polyvinylidene fluoride, is hydrophilic, has a pore size of 0.22 to 0.45 μm, and a porosity of 70% to 85%.

[0027] The retention rate of the HgSNPs on the microporous filter membrane is higher than 90% as measured by cold vapor atomic fluorescence spectroscopy;

[0028] The Hg 2+ Filtration is achieved by passing through a microporous filter membrane, and the transmittance is higher than 100% as measured by cold vapor atomic fluorescence spectroscopy.

[0029] Preferably, the pore size of the polyvinylidene fluoride microporous filter membrane is 0.45 μm, and the porosity is 70% to 85%.

[0030] The retention rate of the HgS NPs on the microporous filter membrane is higher than 90% as measured by cold vapor atomic fluorescence spectroscopy;

[0031] The Hg 2+ Filtration is achieved by passing through a microporous filter membrane, and the transmittance is higher than 100% as measured by cold vapor atomic fluorescence spectroscopy.

[0032] Preferably, the pore size of the polyvinylidene fluoride microporous filter membrane is 0.22 μm, and the porosity is 70% to 85%.

[0033] The retention rate of the HgS NPs on the microporous filter membrane is higher than 90% as measured by cold vapor atomic fluorescence spectroscopy;

[0034] The Hg 2+ Filtration is achieved by passing through a microporous filter membrane, and the transmittance is higher than 100% as measured by cold vapor atomic fluorescence spectroscopy.

[0035] According to any embodiment of the present invention, the mixture of HgS NPs and Hg 2+ The pH of the aqueous dispersion of ions is 5-9, for example, pH 5, 6, 7, 8, 9, or any value therebetween, for example, 5.5, 6.5, 7.5, 8.5.

[0036] According to any embodiment of the present invention, the aqueous dispersion further comprises anions, which are preferably NO3 - 、Cl - .

[0037] According to any embodiment of the present invention, the ratio of the diameter of the HgS NPs to the pore size of the microporous membrane is 0.013-0.045, preferably 0.013-0.036, preferably 0.027-0.045, and further preferably 0.027-0.036.

[0038] According to any embodiment of the present invention, Hg and Hg in the HgS NPs in the aqueous dispersion 2+ The concentration ratio of Hg in the ions is (4:1)-(9:1), for example, it can be 2:8(4:1), 3:7, 4:6(2:3), 5:5(1:1), 6:4(3:2), 2:1, 7:3, 8:2(4:1), 9:1, preferably, it is (2:1)-(9:1), and more preferably, it is 9:1.

[0039] According to any embodiment of the present invention, the concentration of HgS NPs is 1 μg / L to 1 mg / L, for example, 1 μg / L, 10 μg / L, 50 μg / L, 100 μg / L, 500 μg / L, or 1 mg / L.

[0040] According to any embodiment of the present invention, the Hg 2+ The concentration of the solution is 1 μg / L to 1 mg / L, for example, 1 μg / L, 10 μg / L, 50 μg / L, 100 μg / L, 500 μg / L, or 1 mg / L.

[0041] Generally speaking, the filtration method is to screen by size. Particles larger than 220nm can generally be removed by ordinary filtration, while nanoparticles below 220nm are filtered by ultrafiltration membrane. The smaller the particle size, the easier it is to pass through the membrane. At the same time, the ultrafiltration membrane is more likely to adsorb particles due to its smaller pore size. The existing technology has not disclosed the efficient separation of metal nanoparticles below 10nm, especially HgS NPs. This application is aimed at HgS NPs and Hg with more negative adsorption energy and smaller size. 2+ Different from other metal sulfides such as nano silver sulfide, HgS NPs have higher surface energy and reactivity, and can react with a variety of substances (organic matter such as nylon, polyvinylidene fluoride, ions such as Hg 2+ etc.) undergoes a strong adsorption effect. Studies have shown that HgS NPs has a strong adsorption effect on Hg 2 + has a strong adsorption capacity, and the adsorption energy is usually negative, while other metal sulfides such as nano silver sulfide have weak adsorption capacity for Ag+ or other metal ions, and the adsorption energy is usually high. 2+ The separation of metal sulfides is more difficult than that of other metal sulfides.

[0042] The above HgS NPs have a great impact on Hg 2+ The strong adsorption of Hg during filtration has the following effects: 2+ Most of them are preferentially adsorbed on the surface of HgS NPs, and the rest are adsorbed by the filter membrane, which leads to the separation of HgS NPs and Hg 2+ To solve this problem, the existing technology generally uses ultrafiltration membrane separation to separate Hg 2+ However, it should be noted that ultrafiltration technology has high requirements for sample pretreatment. The reasons include the characteristics that complex media are easily blocked when passing through ultrafiltration membranes. In addition, the pore size of ultrafiltration membranes is usually 1-100 nm, and the molecular weight cut-off is usually between 1000 and 500000 Dalton. Small pores are easy to adsorb HgS NPs or Hg 2+ , which resulted in the HgS NPs and Hg 2+ The quantitative accuracy decreases.

[0043] Therefore, this application starts from the raw materials and pore size of the microporous membrane to further control the pH and coexisting ions and thus control the HgSNPs and Hg 2+ The molecular form when passing through the filter membrane, thereby achieving HgS and Hg 2+ Efficient separation.

[0044] As described herein, the raw materials and pore size of the microporous membranes currently available on the market include nitrocellulose membrane (NC membrane), cellulose acetate membrane (CA membrane), mixed cellulose ester microporous membrane (MCE membrane), polyethersulfone membrane (PES membrane), nylon membrane (NYLON membrane), polytetrafluoroethylene membrane (PTFE membrane), polyvinylidene fluoride membrane (PVDF membrane), and surfactant-free cellulose acetate membrane (SFCA membrane). However, for example, PTFE membrane has no surface active sites and has weak adsorption capacity for HgS NPs, resulting in small particle size or sol-state HgS NPs being unable to be retained by the large-pore microporous membrane when passing through the microporous membrane. HgS NPs directly enter the filtrate with the liquid, resulting in the HgS NPs and Hg 2+ The resulting deviation is large. In addition, HgS NPs have high surface energy and high surface activity, which makes them prone to agglomeration, leading to clogging of the ultrafiltration membrane. Therefore, this application first selects nylon membrane (NYLON membrane) or polyvinylidene fluoride membrane (PVDF membrane) with active sites. Among them, PVDF membrane is a hydrophilic membrane modified with ethanol or isopropanol, etc., and uses the hydroxyl groups on the hydrophilic membrane surface to adsorb HgS NPs.

[0045] As described herein, HgS NPs and Hg 2+ The morphology of HgS NPs after passing through the membrane is affected by the pH of the solution and the coexisting ions. When the pH is less than 5, HgS NPs are easily dissolved and converted into Hg 2+ , which results in an error in accuracy; when pH>9, Hg 2+ It is easy to hydrate and exists mainly in the form of Hg(OH)2. The radius of Hg compounds in this form is larger, which affects the passage through the filter membrane. The pH value of natural water is usually between 6.5 and 8.5. This method can be directly applied to HgS NPs and Hg in natural water. 2+ The separation of organic matter and coexisting ions does not require pretreatment to remove organic matter and coexisting ions, and the pore size of the microporous filter membrane is large, and it is not easy to cause pore blockage. In addition, preferably, the coexisting ions include Cl - or NO3 - , the anion reacts with Hg in the solution before filtration 2+ Forming a stable complex, Hg 2+ The molecular form of the complex does not change and enters the filtrate directly, and the Hg adsorbed on the surface of HgS NPs 2+ When passing through the microporous membrane, the active sites of HgS NPs are occupied and electron transfer occurs, and the surface Hg 2+ Desorption occurs, thereby achieving the separation of HgS NPs and Hg 2+ Efficient separation.

[0046] The surface active sites of the microporous membrane described herein affect the interaction of HgS NPs with Hg 2+The separation efficiency is high. During the separation process, the microporous membrane is used to occupy the surface active sites of HgS NPs. On the one hand, HgS NPs and Hg 2+ The adsorption sites of HgS NPs are reduced, which makes the Hg adsorbed on the surface of HgS NPs 2+ Desorption occurs, and at the same time, free Hg in the solution 2+ When passing through HgS NPs, no adsorption occurs and it directly enters the filtrate. On the other hand, HgS has a strong adsorption effect with organic matter (such as nylon and polyvinylidene fluoride), and HgS NPs are adsorbed in the channels of the microporous filter membrane, occupying the channels of the microporous filter membrane, thereby reducing Hg 2+ The probability of being adsorbed when passing through the filter membrane is thus increased. This not only improves the retention rate of HgS NPs, preventing small-sized or sol-state HgS NPs from passing through the microporous filter membrane and directly entering the filtrate, but also increases the Hg 2+ transmittance, preventing Hg 2+ adsorbed on HgS NPs, effectively improving the HgS NPs and Hg 2+ separation efficiency.

[0047] This application is applied to mercury sulfide nanoparticles (HgS NPs) and mercury ions (Hg 2+ ), especially the separation of mercury sulfide nanoparticles below 10 nm and mercury ions.

[0048] It should be noted that, since the HgS NPs of the present application have a particle size of less than 10 nm in diameter, and the size of the microporous filter membrane channel is 0.22-0.45 μm, generally speaking, the pore size of the microporous filter membrane is much larger than that of HgS NPs, then HgS NPs can easily pass through the pores of the microporous filter membrane and cannot be retained by HgS NPs. However, it is surprising to find that the retention rate of HgS NPs is high using a microporous filter membrane of this size and material. The reason is presumably that the binding force between HgS NPs and the microporous filter membrane channel is more dependent on the bonding effect between HgS NPs and the microporous filter membrane channel. For example, polar groups such as amide and hydroxyl groups on the nylon surface, and polar groups such as hydroxyl and carboxyl groups generated after the hydrophilicity of the polyvinylidene fluoride surface are strongly interacted with the surface of HgS NPs, thereby achieving adsorption of HgS NPs. At the same time, the electron cloud on the surface of HgS NPs migrates to the surface of the filter membrane, the electron cloud density decreases, and Hg 2+ The adsorption of HgSNPs weakened and the adsorption of anions in the solution, such as Cl - 、NO3 - Forming a more stable structure, at room temperature, HgCl2 exists mainly in the form of molecules in the solution, realizing Hg 2+ of desorption.

[0049] This application is aimed at the transformation research of HgS NPs in the environment. The latest research results show that mercury sulfide nanoparticles (HgS NPs) can be methylated by microorganisms. HgS NPs in the environment may be directly methylated by microorganisms or release Hg 2+ Therefore, HgS NPs and Hg 2+ , which helps to clarify the microbial methylation mechanism of HgS NPs in different environments. It should be noted that during the microbial methylation process, HgS and Hg 2+ It exists in a complex environment, where pH, coexisting substances such as organic ligands (such as EDTA) or competing ions (such as Ca 2+ ) may affect Hg 2+ adsorption, thereby affecting the adsorption of HgS NPs and Hg 2+ The separation of the organic ligands or competitive ions will lead to a large deviation in the evaluation results. Therefore, the use of ultrafiltration technology requires the pretreatment of the above-mentioned organic ligands or competitive ions to prevent clogging. The present invention does not require the pretreatment step of the organic ligands or competitive ions and is applicable to the separation of environmental samples.

[0050] 3. Beneficial effects

[0051] Compared with the prior art, the present invention has the following beneficial effects:

[0052] (1) The method of the present invention achieves adsorption of HgS NPs by selecting a reasonable pore size and material of the microporous filter membrane to generate a strong interaction with the surface of HgS NPs. At the same time, the electron cloud on the surface of HgS NPs migrates to the surface of the filter membrane, and the electron cloud density decreases, so that Hg 2+ The adsorption of HgS NPs weakened and the adsorption of anions in the solution, such as Cl - 、NO3 - Forming a more stable structure, suitable for HgS NPs and Hg with an average particle size of less than 10 nm 2+ The efficient separation between them effectively improves the retention rate of HgS NPs on the filter membrane and the 2+ Transmission rate on the filter membrane;

[0053] (2) The method of the present invention is to use HgS NPs and Hg 2+ The efficient separation between HgS NPs and Hg 2+ quantitative accuracy;

[0054] (3) Compared with ultrafiltration technology, the method of this application does not require pretreatment to remove organic ligands or competitive ions, and can be directly applied to Hg in natural water bodies. 2+For separation of HgS NPs, there is no need to elute the adsorbed nanoparticles after filtration, but direct digestion. The operation is simple, fast and efficient, and uses low-cost materials and reagents, which greatly reduces the analysis cost and has broad application prospects.

[0055] (4) The method of this application can achieve HgS NPs and Hg with an average particle size of less than 10 nm 2+ The efficient separation between them is suitable for the separation of environmental samples and helps to clarify the microbial methylation mechanism of HgS NPs in different environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] The technical solutions of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. However, it should be understood that these drawings are designed for illustrative purposes only and are not intended to limit the scope of the present invention. Furthermore, unless otherwise specified, these drawings are intended only to conceptually illustrate the structures described herein and are not necessarily drawn to scale.

[0057] Figure 1 10 μg / L Hg in Comparative Examples 1-4 2+ Filtration effect of the solution;

[0058] Figure 2 The filtration effect of 10 μg / L HgS NPs aqueous dispersion in Comparative Examples 5-8;

[0059] Figure 3 For HgS NPs and Hg in Examples 1-4 2+ The concentration ratio of Hg in HgS NPs and Hg is 9:1 2+ Filtration effect of aqueous dispersion;

[0060] Figure 4 For HgS NPs and Hg in Examples 5-8 2+ The concentration ratio of Hg in HgS NPs and Hg is 2:1 2+ Filtration effect of aqueous dispersion;

[0061] Figure 5 For the HgS NPs and Hg in Comparative Examples 9-12 2+ The concentration ratio of Hg in HgS NPs and Hg was 1:9. 2+ Filtration effect of aqueous dispersion;

[0062] Figure 6 is the chemical structural formula of nylon 6 in this application;

[0063] Figure 7 is the chemical structural formula of polyvinylidene fluoride of this application;

[0064] Figure 8This is a flow chart of the method for efficiently separating mercury sulfide nanoparticles and mercury ions in this application. DETAILED DESCRIPTION

[0065] The following detailed description of exemplary embodiments of the present invention refers to the accompanying drawings, which form a part of the description, and in which exemplary embodiments of the present invention that can be implemented are shown as examples. Although these exemplary embodiments are described in sufficient detail to enable those skilled in the art to implement the present invention, it should be understood that other embodiments can be implemented and various changes can be made to the present invention without departing from the spirit and scope of the present invention. The following more detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but is merely for illustration and does not limit the description of the features and characteristics of the present invention, so as to propose the best way to perform the present invention and be sufficient to enable those skilled in the art to implement the present invention. Therefore, the scope of the present invention is limited only by the appended claims.

[0066] A method for efficiently separating mercury sulfide nanoparticles and mercury ions, such as Figure 8 As shown, the following steps are included:

[0067] The mixture of mercury sulfide nanoparticles (HgS NPs) and mercury ions (Hg 2+ ) is injected into the filter head and filtered through a microporous membrane;

[0068] Such that the HgS NPs are retained on the filter membrane;

[0069] The Hg 2+ Filtration is achieved through a microporous membrane;

[0070] wherein the HgS NPs have an average particle size of ≥6 nm;

[0071] The microporous filter membrane is a nylon microporous filter membrane with a pore size of 0.22 to 0.45 μm, and / or;

[0072] The microporous filter membrane is a polyvinylidene fluoride microporous filter membrane with a pore size of 0.45 μm.

[0073] 【1】HgS NPs

[0074] The synthesis process of HgS NPs is as follows, including the following steps: adjusting the pH of the buffer solution of 0.01M NaNO3 and 4mM sodium 4-(2-hydroxyethyl)piperazine-1-ethanesulfonate (HEPES) to 7.2, adding 50μM Hg(NO3)2 and 50μM Na2S, and after precipitation for 1 day, removing Hg using a 1kDa dialysis bag in ultrapure water. 2+ .

[0075] The synthesized HgS NPs are spherical particles having an average particle size of less than 10 nm. Preferably, the average particle size of the spherical particles is 6 to 10 nm. More preferably, the average particle size of the spherical particles is 6 to 8 mm.

[0076] 【2】Hg 2+ solution

[0077] Hg 2+ The solution was prepared as follows, including the steps of: diluting to 10 μg / L with standard solution;

[0078] The standard solution can be HgCl2, and the HgCl2 standard solution can be HgCl2 standard solution with concentrations such as 0.1μg / L, 1μg / L, 5μg / L, and 10μg / L, and is diluted with pure water or 1-3% nitric acid.

[0079] The standard solution may also be HgNO3, and the HgNO3 standard solution may have a concentration of 0.1 μg / L, 1 μg / L, 5 μg / L, 10 μg / L, etc., and may be diluted with pure water or 1-3% nitric acid.

[0080] In the examples, a 10 μg / L HgCl2 solution diluted with pure water was used.

[0081] 【3】Mixed with HgS NPs and Hg 2+ Aqueous dispersion of ions

[0082] The preparation process is as follows: HgS NPs and HgCl2 solution are prepared according to the 2+ The concentration ratio of Hg in the mixture was configured to obtain a mixture of HgS NPs and Hg 2+ Aqueous dispersion of ions.

[0083]

Microporous membrane

[0084] The component of the nylon material microporous filter membrane is polyamide fiber. In the embodiment of the present application, nylon 6 is used, which is hydrophilic, has a pore size range of 0.22 to 0.45 μm, a porosity of 70% to 85%, is manufactured by Jinteng, and has a diameter of 25 mm.

[0085] As described herein, the material and pore structure of the nylon microporous membrane affect the retention rate of HgS NPs and the Hg 2+ The principle is that the polar groups such as amide and hydroxyl groups on the surface of nylon and the high porosity affect the adsorption behavior of HgS NPs. The structural formula of nylon 6 is as follows: Figure 6 As shown, the polar groups (amide bonds) promote hydrophilicity and uniform pore formation.

[0086] The polyvinylidene fluoride microporous filter membrane is composed of polyvinylidene fluoride, is hydrophilic, has a pore size of 0.45 μm, a porosity of 70% to 85%, is manufactured by Jinteng, and has a diameter of 25 mm.

[0087] The material and pore structure of the microporous membrane of polyvinylidene fluoride material as described herein affect the retention rate of HgS NPs and Hg 2+ The transmittance of HgS NPs is higher than that of PVDF. The principle is that the polar groups such as hydroxyl and carboxyl groups and high porosity generated by the hydrophilicity modification of the PVDF surface affect the adsorption behavior of HgS NPs. The structural formula of PVDF is as follows: Figure 7 shown.

[0088] The ratio of the HgS NPs diameter to the pore size of the microporous filter membrane is 0.013 to 0.045, preferably 0.013 to 0.036, preferably 0.027 to 0.045, and further preferably 0.027 to 0.036.

[0089] As described herein, the ratio of HgS NPs diameter to the pore size of the microporous membrane affects the HgS retention rate and Hg 2+ The transmittance of HgS NPs and Hg 2+ The retention of HgS in the microporous membrane needs to take into account the pore structure of the microporous membrane. When the porosity and active sites are saturated, Hg 2+ Particles with a diameter much smaller than the inner pore diameter will still pass through the membrane. The pore structure of a microporous membrane consists of open and closed channels, and their channel sizes cannot be completely uniform. Therefore, the retention of HgSNPs relies on both the closed channels or small channels in the microporous membrane and, more importantly, on the interaction between the HgSNPs and the microporous membrane, which allows them to adsorb on active sites. If the ratio of the HgSNP diameter to the pore size of the microporous membrane is too large, more small-sized HgSNPs will be retained in the closed channels or small channels in the microporous membrane. If the ratio of the HgSNP diameter to the pore size of the microporous membrane is too small, that is, the pore size of the microporous membrane is too large, even if there is interaction between the HgSNPs and the microporous membrane, a large number of HgSNPs will not contact the active sites on the microporous membrane and will directly enter the filtrate.

[0090] Hg and Hg in HgS NPs in the aqueous dispersion 2+ The concentration ratio of Hg in the ions is (4:1)-(9:1), preferably, (2:1)-(9:1), and more preferably, 9:1.

[0091] As mentioned above, HgS NPs and Hg 2+ The ratio of HgS NPs and Hg 2+Generally speaking, HgS NPs are first adsorbed on the active sites of the microporous membrane, and the remaining sites will adsorb Hg 2+ Therefore, for the unit area of ​​microporous membrane, the more HgS NPs there are, the more Hg adsorbed on the microporous membrane 2+ The less Hg 2+ The higher the permeability, the higher the permeability. However, it should be considered that if there are too many HgS NPs, HgS NPs cannot be adsorbed and directly enter the filtrate, resulting in a lower retention rate of HgS NPs; if there are too few HgS NPs, a large number of active sites of the microporous filter membrane will be exposed, making it easy to adsorb Hg 2+ , resulting in Hg 2+ The lower the transmittance.

[0092] In addition, since HgS NPs are nanosized, when HgS NPs and Hg 2+ When the aqueous dispersion passes through the filter membrane, the HgS NPs are easily retained on the filter membrane surface or in the pores due to the large water tension.

[0093] According to any embodiment of the present invention, the concentration of the HgS NPs is 1 μg / L to 1 mg / L.

[0094] According to any embodiment of the present invention, the Hg 2+ The concentration of the solution is 1 μg / L to 1 mg / L.

[0095] According to any embodiment of the present invention, the Hg 2+ The solution also contains anions, which are preferably NO3 - or Cl - .

[0096]

Test method

[0097] As described above, the method for efficiently separating and quantifying mercury sulfide nanoparticles and mercury ions uses a filter with a detachable polytetrafluoroethylene (PTFE) filter head with a diameter of 25 mm and a microporous filter membrane with a pore size of 0.22 to 0.45 μm. During assembly, ensure the sealing of the front and back surfaces of the microporous filter membrane and the filter head.

[0098] Will contain mercury ions (Hg 2+ ) and an aqueous dispersion of mercury sulfide nanoparticles (HgS NPs) with an average particle size of 6 to 8 nm are filtered through a filter to obtain a separated filtrate and a filter membrane.

[0099] The filtrate and filter membrane after separation were digested with aqua regia respectively.

[0100] Among them, 1 mL of the filtrate was taken out and added to 2 mL of freshly prepared aqua regia;

[0101] Soak the filter membrane in 1 mL of ultrapure water and then add 2 mL of freshly prepared aqua regia.

[0102] The filtrate and filter membrane were pre-digested by standing overnight, then digested in a water bath at 95°C for 30 min. After being taken out, the temperature was cooled to room temperature, diluted, and mercury was reduced with 20% stannous chloride solution. The solution was quantified by a cold atomic fluorescence spectrometer.

[0103] The cold vapor atomic fluorescence spectrometer used in this patent is a Brooks-Rand Model III, which mainly consists of three parts: a purge and trap, thermal desorption in a gold sand tube, and an atomic fluorescence spectrometry detection module. The test refers to the U.S. Environmental Protection Agency Standard Method 1631, "Method 1631, Revision E: Mercury in Water by Oxidation, Purge and Trap, and Cold Vapor Atomic Fluorescence Spectrometry". Using this method, the mercury recovery rate measured was greater than 100%, which is within the acceptable range.

[0104] (1) Purge and capture module:

[0105] Nitrogen is used as the purge gas, and the purge inlet flow rate is controlled at 350 mL / min by a flow meter with a range of 0-600 mL / min. The cold vapor generator uses a 200 mL borosilicate glass bubbler bottle with a height of 15.0 cm and a diameter of 5.0 cm. It has a frosted bottle mouth with a standard taper of 24 / 40 and is equipped with a glass tube with a sand core, which extends to within 0.2 cm of the bottom of the bubbler bottle for blowing. A borosilicate glass tube filled with soda lime particles is connected to the gas outlet of the bubbler bottle to dry the mercury vapor and prevent water vapor from interfering with the detection. A gold sand tube is connected to the end of the drying tube to capture the cold vapor. The mercury in the vapor reacts with gold to form amalgam, achieving the purpose of capture. The gold sand tube that has captured mercury is placed on a thermal cracking device to release the mercury again.

[0106] (2) Thermal cracking module:

[0107] Using argon as the carrier gas, the re-released mercury vapor is carried into an atomic fluorescence spectrometer for detection. The specific process involves placing the mercury-trapping gold sand tube into a heating coil, controlling the voltage across the tube to 13.5V, and heating for one minute to a temperature of 500-550°C. The carrier gas flow is controlled at 50mL / min by a 0-100mL / min flowmeter. The argon gas carries the mercury vapor cracked from the gold sand tube into the detector.

[0108] (3) Atomic fluorescence spectroscopy detection module:

[0109] The module primarily consists of a fluorescence chamber, a mercury vapor lamp, and a photomultiplier tube. Argon gas carries mercury vapor into the fluorescence cell, which is a rectangular quartz chamber measuring 12mm x 12mm x 45mm. The mercury vapor lamp has a power of 4W and requires a 30-minute preheating period to ensure sufficient and stable light output during operation. The negative high voltage of the photomultiplier tube needs to be adjusted according to the instrument status and the use of the mercury vapor lamp. A black alumina optical block is used to cover the quartz fluorescence cell, photomultiplier tube, and mercury vapor lamp, maintaining a vertical angle.

[0110] according to:

[0111]

[0112] The retention rate of HgS NPs was calculated, where the mass of HgS NPs in the mixed liquid = the total amount of mercury in the mixed liquid × the mass proportion of HgS NPs in the mixed liquid, that is:

[0113]

[0114] Calculated Hg 2+ The transmittance of Hg 2+ The transmittance of the mixed liquid Hg 2+ Mass = total mercury content in mixed liquid × Hg in mixed liquid 2+ Mass ratio, that is:

[0115]

[0116] Comparative Example 1

[0117] 5 mL of a solution containing 10 μg / L mercury ions (Hg 2+ ) is filtered through a filter, wherein the microporous filter membrane is a nylon microporous filter membrane with a pore size of 0.45 μm, to obtain a separated filtrate and a filter membrane.

[0118] Take out 1 mL of the filtrate and add 2 mL of freshly prepared aqua regia;

[0119] Soak the filter membrane in 1 mL of ultrapure water and then add 2 mL of freshly prepared aqua regia.

[0120] After pre-digestion overnight, digest in a water bath at 95°C for 30 minutes. Take out and cool to room temperature, dilute, reduce mercury with 20% stannous chloride solution, and quantify on a cold atomic fluorescence spectrometer. The results are as follows Figure 1 shown.

[0121] Comparative Example 2

[0122] The filtration method and test method of this comparative example are the same as those of comparative example 1, except that the microporous filter membrane is a 0.22 μm nylon microporous filter membrane. Figure 1 shown.

[0123] Comparative Example 3

[0124] The filtration method and test method of this comparative example are the same as those of comparative example 1, except that the microporous filter membrane is a 0.45 μm PVDF microporous filter membrane. Figure 1 shown.

[0125] Comparative Example 4

[0126] The filtration method and test method of this comparative example are the same as those of comparative example 1, except that the microporous filter membrane is a 0.22 μm PVDF microporous filter membrane. Figure 1 shown.

[0127] Nylon microporous membranes with a pore size of 0.45 μm, PVDF microporous membranes with a pore size of 0.45 μm, and nylon microporous membranes with a pore size of 0.22 μm can filter Hg 2+ , and finally Hg 2+ The Hg retained in the filtrate, where the 0.45 μm pore size nylon 2+ The transmittance of Hg in PVDF with a pore size of 0.45 μm is 83.90 ± 9.23%. 2+ The transmittance of Hg in nylon with a pore size of 0.22 μm is 95.66±2.59%. 2+ The transmittance of Hg in PVDF with a pore size of 0.22 μm is 88.25 ± 3.57%. 2+ The transmittance of nylon membrane with 0.45μm pore size, PVDF membrane with 0.45μm pore size and PVDF membrane with 0.22μm pore size is 25.25±0.90%. 2+ The recovery rate is >80%. Since the filter membrane is in a wet state, there are active adsorption sites on its surface and inside, which leads to the recovery of some Hg 2+ Retained on the filter membrane; PVDF filter membrane with a pore size of 0.22μm can retain Hg 2+ The reason is that although the pore size of 0.22 μm is much larger than that of Hg 2+ The diameter of the hydrated ion is about 0.2-0.3 nm, but the retention effect of the filter membrane does not only rely on physical screening, but also involves other mechanisms. This application uses the hydrophilic segment of PVDF to adsorb Hg through electrostatic interaction, coordination or van der Waals force or the presence of active adsorption sites. 2+ , and the relatively small pore size improves its adsorption capacity, resulting in some Hg 2+ of detention.

[0128] Among them, it should be noted that the original PVDF is a hydrophobic material. In order to improve the hydrophilicity of PVDF, modified hydrophilic PVDF is generally used, such as introducing hydroxyl groups on the surface of PVDF. However, the introduction of hydroxyl groups changes the pore structure of the microporous filter membrane to a certain extent. When water passes through the filter membrane, the high surface tension causes the droplets to agglomerate, and the resistance of the droplets passing through the filter membrane increases, resulting in a large amount of liquid residue on the filter membrane, which in turn leads to the Hg content of the filter membrane with a specific pore size. 2+ The passing rate is reduced, and nylon is basically a hydrophilic segment and does not need to be modified. When it contains HgS NPs and Hg 2+ When the aqueous phase passes through the filter membrane, the high surface tension causes the droplets to agglomerate, the resistance of the droplets passing through the filter membrane increases, and the amount of liquid remaining on the filter membrane is large, which leads to Hg 2+ The pass rate has decreased.

[0129] Comparative Example 5

[0130] 5 mL of an aqueous dispersion of mercury sulfide nanoparticles (HgS NPs) with an average particle size of 6 to 8 nm and a concentration of 10 μg / L (Hg mass concentration) was filtered through a filter having a nylon microporous filter membrane with a pore size of 0.45 μm to obtain a separated filtrate and a filter membrane.

[0131] Take out 1 mL of the filtrate and add 2 mL of freshly prepared aqua regia;

[0132] Soak the filter membrane in 1 mL of ultrapure water and then add 2 mL of freshly prepared aqua regia.

[0133] After pre-digestion overnight, digest in a water bath at 95°C for 30 min.

[0134] After taking out, cool to room temperature, dilute, reduce mercury with 20% stannous chloride solution, and quantify on a cold atomic fluorescence spectrometer. Figure 2 shown.

[0135] Comparative Example 6

[0136] The filtration method and test method of this comparative example are the same as those of comparative example 5, the only difference being that the microporous filter membrane is a 0.22 μm nylon microporous filter membrane. Figure 2 shown.

[0137] Comparative Example 7

[0138] The filtration method and test method of this comparative example are the same as those of comparative example 5, the only difference being that the microporous filter membrane is a 0.45 μm PVDF microporous filter membrane. Figure 2 shown.

[0139] Comparative Example 8

[0140] The filtration method and test method of this comparative example are the same as those of comparative example 5, the only difference being that the microporous filter membrane is a 0.22 μm PVDF microporous filter membrane. Figure 2 shown.

[0141] like Figure 2 As shown, nylon and PVDF microporous membranes with a pore size of 0.45 μm were able to retain some HgSNPs, allowing them to pass through the membranes. Approximately 9% of the HgSNPs passed through the membranes. The retention rates for HgSNPs on nylon with a pore size of 0.45 μm were 90.87 ± 1.06%, on PVDF with a pore size of 0.45 μm, 90.99 ± 0.74%, on nylon with a pore size of 0.22 μm, 98.02 ± 1.81%, and on PVDF with a pore size of 0.22 μm, 97.11 ± 0.85%. The particle size of HgSNPs is significantly smaller than the pore size of the microporous membranes, allowing the membranes to retain some HgSNPs in the liquid due to their inherent adsorption properties.

[0142] Example 1

[0143] Take 5mL of HgS NPs and Hg with a total mercury concentration of 10μg / L 2+ The aqueous dispersion was filtered through a filter to obtain a separated filtrate and a filter membrane, wherein Hg and Hg in HgS NPs 2+ The concentration (mass concentration) ratio of Hg in the solution is 9:1.

[0144] Take out 1 mL of the filtrate and add 2 mL of freshly prepared aqua regia;

[0145] Soak the filter membrane in 1 mL of ultrapure water and then add 2 mL of freshly prepared aqua regia.

[0146] After pre-digestion overnight, digest in a water bath at 95°C for 30 minutes. Take out and cool to room temperature, dilute, reduce mercury with 20% stannous chloride solution, and quantify on a cold atomic fluorescence spectrometer. The results are as follows. Figure 3 shown.

[0147] Example 2

[0148] The filtration method and test method of this embodiment are the same as those of embodiment 1, except that the microporous filter membrane is a 0.22 μm nylon microporous filter membrane. Figure 3 shown.

[0149] Example 3

[0150] The filtration method and test method of this embodiment are the same as those of embodiment 1, except that the microporous filter membrane is a 0.45 μm PVDF microporous filter membrane. Figure 3 shown.

[0151] Example 4

[0152] The filtration method and test method of this embodiment are the same as those of embodiment 1, except that the microporous filter membrane is a 0.22 μm PVDF microporous filter membrane. Figure 3 shown.

[0153] like Figure 3 As shown, when Hg and Hg 2+ When the concentration ratio of Hg in ions was 9:1, after filtration, the total mercury accounted for 83.56±1.43% of the total mercury in the nylon membrane with a pore size of 0.45μm, and the total mercury accounted for 8.62±0.33% of the total mercury in the filtrate; the total mercury accounted for 88.47±1.88% of the total mercury in the PVDF membrane with a pore size of 0.45μm, and the total mercury accounted for 10.72±2.15% of the total mercury in the filtrate; the total mercury accounted for 79.57±1.63% of the total mercury in the nylon membrane with a pore size of 0.22μm, and the total mercury accounted for 10.03±1.32% of the total mercury in the filtrate; the total mercury accounted for 85.55±2.40% of the total mercury in the PVDF membrane with a pore size of 0.22μm, and the total mercury accounted for 11.16±0.93% of the total mercury in the filtrate;

[0154] according to:

[0155]

[0156] The results show that the retention rate of HgS NPs on nylon with a pore size of 0.45 μm is 92.84 ± 1.58%, and the retention rate of Hg 2+ The transmittance of HgS NPs was 86.16±3.26%, the rejection rate of HgS NPs of PVDF with a pore size of 0.45 μm was 98.30±2.09%, and the 2+ The transmittance of HgS NPs was 107.18±21.5%; the retention rate of HgS NPs in nylon with a pore size of 0.22 μm was 88.41±1.81%, and the Hg 2+ The transmittance of HgS NPs was 100.3±13.18%, the retention rate of HgS NPs of PVDF with a pore size of 0.22 μm was 95.06±2.67%, and the Hg 2+ The transmittance is 111.60±9.29%.

[0157] Compared with Comparative Examples 1-4 and Comparative Examples 5-8, the retention rates of HgS NPs in Examples 1-4 and Hg 2+ During the separation process, HgS NPs first adsorbed on the active sites of the microporous membrane, and the remaining sites would adsorb Hg 2+ On the one hand, HgS NPs and Hg 2+The adsorption sites of HgS NPs are reduced, which makes the Hg adsorbed on the surface of HgS NPs 2+ Desorption occurs, and at the same time, free Hg in the solution 2+ When passing through HgS NPs, no adsorption occurs and it directly enters the filtrate. On the other hand, HgSNPs have a strong adsorption effect on the filter membrane, occupying the channel of the microporous filter membrane, thereby reducing Hg 2+ The probability of being adsorbed when passing through the filter membrane, thereby effectively increasing the separation of HgS NPs and Hg 2+ separation efficiency.

[0158] Example 5

[0159] The method of this embodiment is basically the same as that of embodiment 1, except that the Hg and Hg 2+ The concentration (mass concentration) ratio of Hg in the ions is 2:1.

[0160] Example 6

[0161] The filtration method and test method of this embodiment are the same as those of embodiment 5, the only difference being that the microporous filter membrane is a 0.22 μm nylon microporous filter membrane. Figure 4 shown.

[0162] Example 7

[0163] The filtration method and test method of this embodiment are the same as those of embodiment 5, the only difference being that the microporous filter membrane is a 0.45 μm PVDF microporous filter membrane. Figure 4 shown.

[0164] Example 8

[0165] The filtration method and test method of this embodiment are the same as those of embodiment 5, the only difference being that the microporous filter membrane is a 0.22 μm PVDF microporous filter membrane. Figure 4 shown.

[0166] like Figure 4 As shown, the total mercury proportion of the nylon filter membrane with a pore size of 0.45μm was 58.34±0.52%, and the total mercury proportion of the filtrate was 35.80±0.40%; the total mercury proportion of the PVDF filter membrane with a pore size of 0.45μm was 70.15±1.22%, and the total mercury proportion of the filtrate was 30.54±1.03%; the total mercury proportion of the nylon filter membrane with a pore size of 0.22μm was 57.64±1.29%, and the total mercury proportion of the filtrate was 31.99±0.24%; the total mercury proportion of the PVDF filter membrane with a pore size of 0.22μm was 66.03±0.60%, and the total mercury proportion of the filtrate was 31.58±1.22%.

[0167] according to:

[0168]

[0169] The results show that the retention rate of HgS NPs on nylon with a pore size of 0.45 μm is 97.43 ± 0.87%, and the Hg 2+ The transmittance of HgS NPs was 119.33±1.33%, the retention rate of HgS NPs of PVDF with a pore size of 0.45 μm was 117.15±2.04%, and the Hg 2+ The transmittance of HgS NPs was 101.80±3.43%; the retention rate of HgS NPs in nylon with a pore size of 0.22 μm was 96.26±2.15%, and the Hg 2+ The transmittance of HgS NPs was 106.63±0.80%, the retention rate of HgS NPs of PVDF with a pore size of 0.22 μm was 110.27±1.00%, and the Hg 2+ The transmittance is 105.27±4.07%.

[0170] Compared with Comparative Examples 1-4 and Comparative Examples 5-8, the retention rate of HgS NPs in Examples 5-8 and Hg 2+ The transmittance has been improved.

[0171] Comparative Example 9

[0172] The method of this embodiment is basically the same as that of embodiment 1, except that the Hg and Hg 2+ The concentration ratio (mass concentration) of Hg in the ions is 1:9.

[0173] Comparative Example 10

[0174] The filtration method and test method of this embodiment are the same as those of embodiment 9, the only difference being that the microporous filter membrane is a 0.22 μm nylon microporous filter membrane. Figure 5 shown.

[0175] Comparative Example 11

[0176] The filtration method and test method of this embodiment are the same as those of embodiment 9, the only difference being that the microporous filter membrane is a 0.45 μm PVDF microporous filter membrane. Figure 5 shown.

[0177] Comparative Example 12

[0178] The filtration method and test method of this embodiment are the same as those of embodiment 9, the only difference being that the microporous filter membrane is a 0.22 μm PVDF microporous filter membrane. Figure 5 shown.

[0179] like Figure 5As shown, the total mercury proportion of the nylon filter membrane with a pore size of 0.45μm was 18.31±2.31%, and the total mercury proportion of the filtrate was 83.44±2.31%; the total mercury proportion of the PVDF filter membrane with a pore size of 0.45μm was 22.43±0.58%, and the total mercury proportion of the filtrate was 73.52±1.00%; the total mercury proportion of the nylon filter membrane with a pore size of 0.22μm was 19.15±1.36%, and the total mercury proportion of the filtrate was 79.88±1.71%; the total mercury proportion of the PVDF filter membrane with a pore size of 0.22μm was 29.53±2.00%, and the total mercury proportion of the filtrate was 43.57±6.18%.

[0180] according to:

[0181]

[0182] The results show that the retention rate of HgS NPs on nylon with a pore size of 0.45 μm is 183.06 ± 13.12%, and the Hg 2+ The transmittance of HgS NPs was 92.71±2.57%, the rejection rate of HgS NPs of PVDF with a pore size of 0.45 μm was 224.29±5.80%, and the Hg 2+ The permeability of HgS NPs was 81.69±1.11%; the retention rate of HgS NPs in nylon with a pore size of 0.22 μm was 191.50±13.61%, and the Hg 2+ The transmittance of HgS NPs was 88.76±1.90%, the retention rate of HgS NPs of PVDF with a pore size of 0.22 μm was 295.29±20.00%, and the 2+ The transmittance is 48.41±6.87%.

[0183] like Figures 3-5 As shown in the figure, nylon and PVDF microporous membranes with pore sizes of 0.22 to 0.45 μm can achieve the separation of HgSNPs and Hg in aqueous dispersions. 2+ According to the total mercury ratio of the filter membrane and the filtrate, Hg and Hg in HgS NPs in the aqueous dispersion 2+ After filtration of the aqueous dispersion with a Hg concentration ratio of 9:1, about 83-90% of the total mercury was on the filter membrane, and about 9-11% of the total mercury was in the filtrate, corresponding to 83-90% of HgS NPs and 9-11% of Hg in the aqueous dispersion. 2+ Components. HgS NPs and Hg 2+ After filtration of the aqueous dispersion with a Hg concentration ratio of 2:1, about 58-70% of the total mercury remained on the filter membrane and about 29-36% of the total mercury remained in the filtrate, corresponding to 67% of HgS NPs and 33% of Hg in the aqueous dispersion. 2+ Components. Hg and Hg in HgS NPs 2+After filtration of the aqueous dispersion with a concentration ratio of Hg to ions of 1:9, about 18-22% of the total mercury remained on the filter membrane, and about 73-85% of the total mercury remained in the filtrate. This is because there are fewer particles in the aqueous dispersion and they do not completely occupy the binding sites on the membrane, so some of the ionic mercury is also adsorbed on the membrane, or Hg 2+ adsorbed on HgS NPs and were co-entrapped.

[0184] This method effectively intercepted HgS NPs in aqueous dispersions while ensuring that Hg 2+ The two substances enter the filtrate through the filter membrane, successfully achieving efficient separation and quantification.

[0185] It should be noted that this application is applicable to HgS and Hg in liquid state. 2+ Separation of HgS and Hg in the gas phase system 2+ There are obvious differences. First, in a liquid environment, divalent mercury mainly exists in the form of dissolved ions or complexes, has low diffusivity, and is mainly affected by solution concentration, temperature, and ionic strength, which is significantly different from a gas environment.

[0186] In the gas phase, divalent mercury is adsorbed on the modified nylon membrane, while zero-valent mercury passes directly through it. This is because the nylon surface incorporates Cl-, whose polar groups can form coordination bonds or ion-dipole interactions with gaseous divalent mercury. However, zero-valent mercury is a neutral elemental molecule lacking active sites for coordination or electrostatic interactions with the nylon membrane surface. It passes directly through the membrane pores solely by physical diffusion. This mechanism is fundamentally different from that of the present application.

[0187] In liquid environments, Hg 2 + preferentially forms a stable mercury complex with Cl- in a Cl-containing solution, but this step occurs before passing through the membrane, that is, the form change of mercury in the target liquid has reached thermodynamic equilibrium before separation. The separation behavior itself will not affect the change of mercury form, but the separation effect is achieved through polar adsorption rather than direct conversion of mercury form by the membrane material.

[0188] The average particle size of HgS NPs used in the example is 6 to 8 nm, and this method can achieve efficient separation. Therefore, the present invention is practical and effective, easy to operate, and has low analysis cost. The above description is only a preferred embodiment of the present application and an explanation of the technical principles used. Those skilled in the art should understand that the scope involved in this application is not limited to the technical solutions formed by the specific combination of the above technical features, but also should cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept, such as the technical solutions formed by replacing the above features with (but not limited to) technical features with similar functions disclosed in this application.

[0189] Except for the technical features described in the specification, the remaining technical features are known technologies to those skilled in the art. In order to highlight the innovative features of the present invention, the remaining technical features will not be described here in detail.

Claims

1. Provide a method for efficiently separating mercury sulfide nanoparticles and mercury ions, characterized in that: The steps include: The mixture of HgS NPs and Hg 2+ The aqueous dispersion of ions is filtered through a microporous membrane; Such that the HgS NPs are retained on the microporous filter membrane; The Hg 2+ Filtration is achieved through a microporous membrane; wherein the HgS NPs have an average particle size of <10 nm; The microporous filter membrane is a nylon microporous filter membrane with a pore size of 0.22 to 0.45 μm, and / or; The microporous filter membrane is a polyvinylidene fluoride microporous filter membrane with a pore size of 0.22 to 0.45 μm.

2. The method according to claim 1, characterized in that The HgS NPs are spherical particles, and the average particle size D of the spherical particles satisfies 6 nm ≤ D < 10 nm.

3. The method according to claim 1, characterized in that The microporous filter membrane is a nylon microporous filter membrane with a pore size of 0.22 to 0.45 μm; The main component of the nylon microporous filter membrane is polyamide fiber, and the porosity is 70% to 85%; The retention rate of the HgS NPs on the microporous filter membrane is higher than 80% as measured by cold vapor atomic fluorescence spectroscopy; The Hg 2+ Filtration is achieved through a microporous filter membrane, with a transmittance greater than 80% as measured by cold vapor atomic fluorescence spectroscopy.

4. The method according to claim 1, wherein The microporous filter membrane is a polyvinylidene fluoride microporous filter membrane with a pore size of 0.22 to 0.45 μm; The polyvinylidene fluoride microporous filter membrane is composed of polyvinylidene fluoride and has a porosity of 70% to 85%; The retention rate of the HgS NPs on the microporous filter membrane is higher than 90% as measured by cold vapor atomic fluorescence spectroscopy; The Hg 2+ Filtration is achieved by passing through a microporous filter membrane, and the transmittance is higher than 100% as measured by cold vapor atomic fluorescence spectroscopy.

5. The method according to claim 4, characterized in that The microporous filter membrane is a polyvinylidene fluoride microporous filter membrane with a pore size of 0.45 μm; The polyvinylidene fluoride microporous filter membrane is composed of polyvinylidene fluoride and has a porosity of 70% to 85%; The retention rate of the HgS NPs on the microporous filter membrane is higher than 90% as measured by cold vapor atomic fluorescence spectroscopy; The Hg 2+ Filtration is achieved by passing through a microporous filter membrane, and the transmittance is higher than 100% as measured by cold vapor atomic fluorescence spectroscopy.

6. The method according to claim 5, characterized in that The polyvinylidene fluoride microporous filter membrane is a hydrophilic membrane.

7. The method according to claim 6, characterized in that The mixture of HgS NPs and Hg 2+ The pH of the aqueous dispersion of the ions is 5-9.

8. The method according to claim 7, characterized in that The aqueous dispersion also contains anions, which are NO3 - or Cl - .

9. The method according to claim 8, characterized in that Hg and Hg in HgS NPs in the aqueous dispersion 2+ The concentration ratio of Hg in the ions is (4:1)-(9:1).

10. The method according to claim 9, characterized in that The ratio of the diameter of the HgS NPs to the pore size of the microporous filter membrane is 0.013 to 0.045.

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