An integrated method for detecting and removing Hg 2+ ​

Abstract

The present invention belongs to the technical field of sensing and adsorption removal, and particularly relates to a method for integrated detection and removal of Hg 2+ ; based on the introduction of the aggregation-induced fluorescence signal amplification strategy and the aggregation-induced fluorescence property of gold nanoclusters, the present invention confines their aggregation in the MOF framework to prepare a bifunctional material (Fe3O4-AuNCs@MOFs) with two functions of detection, adsorption and removal; it is used for Hg 2+ detection, with high sensitivity, and the detection limit is as low as 0.11 ppb. Without the aid of other detection methods, it can meet the feedback of the removal efficiency at trace concentration levels (ppb concentration level); Fe3O4-AuNCs@MOFs is used for Hg 2+ adsorption and removal. The adsorption process only takes 10 minutes to achieve rapid removal; at the same time, the removal efficiency can still reach 88.7% after 10 times of reuse; even when the pH of the solution is 2, the removal rate can still reach 68%.

Description

Technical Field

[0001] The present invention belongs to the technical field of sensing and adsorption removal, and particularly relates to a highly sensitive, dual-functional, integrated Hg 2+ detection and removal method. Background Art

[0002] Mercury ions (Hg 2+ ) are non-biodegradable and bioaccumulative. Even at trace concentrations, they can cause serious environmental pollution and irreversible damage to humans. Therefore, achieving sensitive detection and effective removal of Hg 2+ is particularly important for environmental remediation. Integrated detection and removal technologies, such as the combination of fluorescence detection and adsorption removal, have the following advantages: (i) avoiding multiple operations, improving cost-effectiveness and remediation efficiency; (ii) the detector can feedback the adsorption efficiency, and adsorption preconcentration can improve the sensing sensitivity. However, traditional fluorescent probes or adsorbents can only achieve their respective purposes and it is difficult to have both detection and removal functions at the same time.

[0003] Metal-organic frameworks (MOFs) are a new type of microporous crystalline material prepared by self-assembly of metal ions and organic ligands. A few dual-functional MOFs have achieved simultaneous detection and removal of Hg 2+ with good results. However, their detection limits are all at the ppm level. If the remaining amount of Hg 2+ after adsorption is lower than the detection limit, additional detection methods (such as inductively coupled plasma mass spectrometry, etc.) need to be used, which not only affects the timeliness of feedback on the adsorption effect, but also requires professional operators for operation. Summary of the Invention

[0004] Aiming at the problems existing in the prior art, the present invention aims to solve the problems of low detection sensitivity of integrated detection and removal of Hg 2+ and the need to rely on other detection methods (such as detection methods other than fluorescence analysis methods like inductively coupled plasma mass spectrometry) to feedback the adsorption effect.

[0005] Based on this, the present invention proposes a highly sensitive, dual-functional, integrated Hg 2+ detection and removal method, introducing an aggregation-induced fluorescence signal amplification strategy. Based on the aggregation-induced fluorescence property of gold nanoclusters, restricting their aggregation in the MOF framework to prepare a dual-functional material (Fe 3 O 4 -AuNCs@MOFs) with both detection and adsorption removal functions.

[0006] Fe 3 O 4-AuNCs@MOFs, as an adsorbent, has nitrogen-containing functional groups on its surface, and there is a d-d metallophilic interaction between the gold nanoclusters and the metal ions of MOFs and Hg. Therefore, FeO-AuNCs@MOFs can adsorb and bind Hg; in addition, FeO-AuNCs@MOFs is insoluble in water and has magnetism, and FeO-AuNCs@MOFs can be separated from water by magnetic separation or centrifugation. At the same time, the Hg adsorbed on FeO-AuNCs@MOFs will also be separated with it, so as to achieve the purpose of Hg removal. 2+ There is a 10 d-d 10 metallophilic interaction between them and Hg, so FeO-AuNCs@MOFs can adsorb and bind Hg; 3 O 4 in addition, FeO-AuNCs@MOFs is insoluble in water and has magnetism, and FeO-AuNCs@MOFs can be separated from water by magnetic separation or centrifugation. 2+ At the same time, the Hg adsorbed on FeO-AuNCs@MOFs will also be separated with it, so as to achieve the purpose of Hg removal. 3 O 4 -AuNCs@MOFs is insoluble in water and has magnetism, and FeO-AuNCs@MOFs can be separated from water by magnetic separation or centrifugation. 3 O 4 -AuNCs@MOFs from water, and at the same time, the Hg adsorbed on FeO-AuNCs@MOFs will also be separated with it, so as to achieve the purpose of Hg removal. 3 O 4 -AuNCs@MOFs will also be separated with it, so as to achieve the purpose of Hg removal. 2+ will also be separated with it, so as to achieve the purpose of Hg removal. 2+ To achieve the above purpose, the present invention adopts the following technical solutions;

[0007] Fe 3 O 4 -AuNCs@MOFs as a fluorescent probe has a strong fluorescent signal itself. When combined with Hg, there is a bonding force and electron transfer between the two. Therefore, the presence of Hg will cause the fluorescence of FeO-AuNCs@MOFs to be quenched, so as to achieve the purpose of Hg detection. 2+ When combined with Hg, there is a bonding force and electron transfer between the two. Therefore, the presence of Hg will cause the fluorescence of FeO-AuNCs@MOFs to be quenched, so as to achieve the purpose of Hg detection. 2+ The presence of Hg will cause the fluorescence of FeO-AuNCs@MOFs to be quenched, so as to achieve the purpose of Hg detection. 3 O 4 -AuNCs@MOFs fluorescence quenching, so as to achieve the purpose of Hg detection. 2+ To achieve the above purpose, the present invention adopts the following technical solutions;

[0008] To achieve the above purpose, the present invention adopts the following technical solutions;

[0009] A method for integrated detection and removal of Hg 2+ includes the following steps:

[0010] (1) Synthesize a FeO-AuNCs@MOFs solution; 3 O 4 -AuNCs@MOFs solution;

[0011] S1. Dissolve 6-aza-2-thiothymine (ATT) and sodium hydroxide in water, add chloroauric acid solution, stir in the dark to obtain a golden yellow solution; after dialysis with a dialysis bag, perform freeze-drying to obtain a golden yellow solid powder, which is ATT-AuNCs;

[0012] S2. Dissolve the ATT-AuNCs obtained in step S1 in water, add ethanol and mix evenly; after centrifugation, take the precipitate and disperse it in methanol to obtain dispersion liquid a;

[0013] S3. Dissolve ferric chloride and ferrous chloride in water, pass N to remove oxygen under stirring, then dropwise add ammonia water solution, and continue to stir and react for a period of time under certain temperature conditions; after the reaction, collect the precipitate by magnetic separation, wash it with water until neutral, and dry it to obtain black Fe 2 O solid powder; disperse the Fe 3 O 4 solid powder in water to obtain dispersion liquid b; 3 O 4

[0014] S4. Add zinc nitrate hexahydrate to methanol to obtain a zinc nitrate hexahydrate methanol solution; then mix the dispersion liquid a in step S2, the dispersion liquid b in step S3 and the zinc nitrate hexahydrate methanol solution and perform the first ultrasonic treatment to obtain a mixed liquid c;

[0015] Add 2-methylimidazole to methanol to obtain a 2-methylimidazole methanol solution; then add the 2-methylimidazole methanol solution to the mixed liquid c and perform the second ultrasonic treatment; after the ultrasonic treatment, perform centrifugation, collect the centrifuged precipitate and wash it by centrifugation with methanol and water respectively; after washing, separate the precipitate by magnet and wash it with water again; after washing, separate the precipitate and dry it to obtain Fe 3 O 4 -AuNCs@MOFs solid powder, disperse it in water to obtain Fe 3 O 4 -AuNCs@MOFs solution;

[0016] (2) Add Hg solutions with different gradient concentrations to the Fe 3 O 4 -AuNCs@MOFs solution in step (1) and mix them. One Fe 2+ O 3 -AuNCs@MOFs solution corresponds to one concentration of Hg 4 solution; obtain a mixed solution containing different concentrations of Hg 2+ ; then adjust the pH of the mixed solution with hydrochloric acid and sodium hydroxide solution and incubate it for a certain time under specific temperature conditions; then separate to obtain a solid precipitate, and this solid precipitate is the binding product of Hg 2+ and Fe 2+ O 3 -AuNCs@MOFs, that is, the removal of Hg 4 in the solution is achieved; 2 +

[0017] (3) Detect the fluorescence signals of the mixed solutions with different concentrations of Hg 2+ in step (2) at 540 nm. The fluorescence signal measured by the solution containing 0 ppb Hg 2+ is denoted as I​​0 , similarly for other Hg 2+ The fluorescence signals corresponding to the solutions with increasing gradient concentrations of Hg are sequentially denoted as I 1 , I 2 , … I n-1 , I n , where n is a positive integer greater than or equal to 3; I 0 and I 1 , I 2 , … I n-1 , I n First, calculate the differences, and then the ratios of these differences to I 0 are respectively denoted as y 1 , y 2 , … y n-1 , y n . Based on y 1 , y 2 , … y n-1 , y n and the logarithm of the corresponding Hg 2+ concentration, a standard curve is established; finally, by measuring the fluorescence signal of the unknown solution at 540 nm and substituting it into the standard curve, the detection of the Hg 2+ concentration in the unknown solution can be achieved.

[0018] Preferably, in S1 of step (1), the dosage relationship of ATT, sodium hydroxide, water, and chloroauric acid solution is 0.1718 g: 0.12 g: 15 mL: 15 mL; where the concentration of the chloroauric acid solution is 10 mg / mL -1 ; the time for light-shielded stirring is 1 h; the dialysis conditions are: 50 kDa dialysis bag, dialysis time is 24 h.

[0019] Preferably, in S2 of step (1), the dosage relationship of ATT-AuNCs, water, and ethanol is 6 mg: 1 mL: 6 mL. The centrifugation speed is 12000 rpm, and the time is 15 min; the concentration of dispersion liquid a is 8 mg / mL -1 .

[0020] Preferably, in S3 of step (1), the dosage relationship of ferric chloride, ferrous chloride, water, and ammonia water solution is 2.35 g: 0.86 g: 100 mL: 10 mL; where the volume concentration of the ammonia water solution is 25%; the certain temperature condition is 80 °C, the reaction time is 30 min; the drying temperature is 60 °C; the concentration of dispersion liquid b is 3 mg / mL -1 .

[0021] Preferably, in S4 of step (1), the concentration of the zinc nitrate hexahydrate methanol solution is 30 mM; the dosage relationship among the dispersion liquid a, the dispersion liquid b and the zinc nitrate hexahydrate methanol solution is 1 ml: 1 ml: 10 ml; the dosage relationship between the mixed liquid c and the 2-methylimidazole methanol solution is 10 - 12 ml: 10 ml; the concentration of the 2-methylimidazole methanol solution is 90 mM.

[0022] Preferably, in S4 of step (1), the frequency of the first ultrasonic wave is 40 KHz and the time is 5 min; the frequency of the second ultrasonic wave is 40 KHz and the time is 10 min; the rotation speed of the centrifugation is 8000 rpm and the time is 10 min;

[0023] The concentration of the Fe 3 O 4 -AuNCs@MOFs solution is 5 mg mL -1 .

[0024] Preferably, in step (2), the concentration of the Fe 3 O 4 -AuNCs@MOFs solution is 5 mg mL -1 ; the concentration of the Hg 2+ solution is 0 - 2000 ppb, and the mixing volume ratio of the Fe 3 O 4 -AuNCs@MOFs solution and the Hg 2+ solution is 2:5; the concentrations of the hydrochloric acid and the sodium hydroxide solution are 0.1 M, and the pH is adjusted to 2.0 - 6.0; the volume ratio of water to the mixed liquid during constant volume is 1 - 8:1; the incubation temperature is 25 °C and the incubation time is 20 - 70 min.

[0025] Advantages of the present invention:

[0026] (1) The present invention introduces an aggregation-induced fluorescence signal amplification strategy. Based on the aggregation-induced fluorescence property of gold nanoclusters, their aggregation is restricted in the MOFs framework, and the prepared composite material Fe 3 O 4 -AuNCs@MOFs has two functions of detection and adsorption removal.

[0027] (2) Fe 3 O 4 -AuNCs@MOFs is used for Hg 2+ detection, has high sensitivity, the detection limit is 0.11 ppb, the linear range is 5 - 1000 ppb, leading many reported fluorescence probes, and can meet the feedback of the removal efficiency at the trace concentration level (ppb concentration level) without relying on other detection methods (such as detection methods other than fluorescence analysis like inductively coupled plasma mass spectrometry, etc.).

[0028] (3) Fe 3 O 4 -AuNCs@MOFs for Hg 2+ adsorption and removal, using sodium sulfide solution as the eluent, the Fe 3 O 4 -AuNCs@MOFs surface of Hg 2+ is eluted, this is one cycle; after 10 cycles, the removal efficiency of Fe 3 O 4 -AuNCs@MOFs can still reach 88.7%.

[0029] (4) Fe 3 O 4 -AuNCs@MOFs for Hg 2+ adsorption and removal, even when the pH of the solution is 2, the removal rate can reach 68%;

[0030] (5) Fe 3 O 4 -AuNCs@MOFs for Hg 2+ adsorption and removal, Fe 3 O 4 -AuNCs@MOFs and Hg 2+ the action time only needs 10 min to achieve the purpose of rapid removal. Description of the Drawings

[0031] Figure 1 is the relationship diagram between the fluorescence change of Fe 3 O 4 -AuNCs@MOFs and the logarithm of Hg 2+ concentration.

[0032] Figure 2 is the removal efficiency diagram of Fe 3 O 4 -AuNCs@MOFs for Hg 2+ after 10 repeated uses.

[0033] Figure 3 is the relationship diagram between the removal efficiency and the solution pH.

[0034] Figure 4 is the relationship diagram between the adsorption capacity and the adsorption time. Detailed Embodiments

[0035] The following describes the embodiments of the present invention in detail with reference to the drawings: The embodiments are carried out on the premise of the technical solution of the present invention, and detailed implementation steps and specific operation processes are given, but the protection scope of the present invention is not limited to the following embodiments.

[0036] Example 1:

[0037] (1) Synthesis of Fe 3 O 4 -AuNCs@MOFs solution;

[0038] Dissolve 0.1718 g of ATT and 0.12 g of sodium hydroxide in 15 mL of water, add 15 mL of 10 mg mL -1 chloroauric acid solution, stir in the dark for 1 h to obtain a golden-yellow solution; dialyze with a 50 kDa dialysis bag for 24 h and then freeze-dry to obtain a golden-yellow gold nanocluster powder, which is stored in the dark at 4 °C for later use;

[0039] Dissolve 6 mg of ATT-AuNCs in 1 mL of water, add 6 mL of ethanol and mix well; centrifuge at 12000 rpm for 20 min and then take the precipitate and disperse it in 1 mL of methanol to obtain dispersion a;

[0040] Dissolve 2.35 g of ferric chloride and 0.86 g of ferrous chloride in 100 mL, and pass N 2 to remove oxygen for 30 min; dropwise add 10 mL of 25% ammonia water solution, and continue to stir at 80 °C for 30 min; magnetic separation for 5 min, and wash with water until neutral, dry at 60 °C under vacuum to obtain black Fe 3 O 4 solid powder, sealed and stored; disperse 3 mg of Fe 3 O 4 in 1 mL of water to obtain dispersion b;

[0041] Mix dispersion a and dispersion b with 10 mL of 30 mM zinc nitrate hexahydrate methanol solution, ultrasonicate at 40 KHz for 5 min to obtain mixture c; add 10 mL of 90 mM 2-methylimidazole methanol solution, ultrasonicate at 40 KHz for 10 min; wash by centrifugation with methanol and water; separate with a magnet and then wash with water again, separate the solid precipitate after washing, and dry to obtain the composite material Fe 3 O 4 -AuNCs@MOFs, disperse it in water to obtain Fe 3 O 4 -AuNCs@MOFs solution.

[0042] (2) Add 50 μL of Hg -1 Fe 3 O 4 -AuNCs@MOFs solution to 20 μL of a solution with a concentration of 5 mg mL 2+Mix the solutions, adjust the pH to 5.0 with 0.1 M hydrochloric acid and 0.1 M sodium hydroxide solution, quantitatively add water to 500 μL, and incubate at 25 °C for 20 min; after magnetic separation with a magnet for 5 min, separate the supernatant and the solid precipitate; the solid precipitate is Hg 2+ combined with Fe 3 O 4 -AuNCs@MOFs; achieve the removal of Hg in the original solution 2+ ;

[0043] (3) Detect the fluorescence signals of mixed solutions with different concentrations of Hg 2+ at 540 nm. Among them, the fluorescence signal measured by the 0 ppb Hg 2+ solution is denoted as I 0 , and the fluorescence signals at 540 nm when adding 5, 10, 50, 200, 1000 ppb Hg 2+ solutions are denoted as I 1 , I 2 , … I 5 ; The difference between I 0 and I 1 , I 2 , … I 5 is taken, and the ratio of the difference to I 0 is denoted as y 1 , y 2 … y 5 ; Based on y 1 , y 2 … y 5 and the logarithm (lg c 2+ ) of different Hg Hg2+ concentrations, establish a standard curve, as Figure 1 shown; The linear equation is: y i = 0.3868 lg c Hg2+ - 0.2249, the correlation coefficient R 2 = 0.9985, the linear range is 5 - 1000 ppb, and the detection limit is 0.11 ppb.

[0044] After Fe 3 O 4 -AuNCs@MOFs adsorbs Hg 2+ , using sodium sulfide solution as the eluent, elute the Hg 3 O 4 on the surface of Fe 2+ -AuNCs@MOFs, and then Fe 3 O 4 -AuNCs@MOFs can adsorb Hg 2+ again to enter the second cycle. As can be seen from Figure 2 , in the first cycle, Fe3 O 4 The removal efficiency of -AuNCs@MOFs is 96.9%; after 10 cycles, Fe 3 O 4 -AuNCs@MOFs can still reach a removal efficiency of 88.7%.

[0045] Example 2:

[0046] In steps (1) to (3), follow the steps (1) to (3) of Example 1, except that in step (2), the pH adjustment is replaced with 2.0, 3.0, 4.0, 6.0. The materials obtained under different pH conditions have the following removal efficiency for Hg 2+ removal efficiency as Figure 3 shown. The results show that with the increase of the solution pH, the removal efficiency increases significantly; when the solution pH is 4, the removal efficiency tends to be stable.

[0047] Example 3:

[0048] In steps (1) to (3), follow the steps (1) to (3) of Example 1, except that in step (2), the incubation time is replaced with 1, 2, 5, 8, 10, 30, 40, 70 min. The adsorption capacity of the materials obtained under different incubation times for Hg 2+ is as Figure 4 shown. The results show that in the early stage, the adsorption increases rapidly with the increase of time; when the incubation time is 10 min, the adsorption reaches saturation.

[0049] Note: The above examples are only used to illustrate the present invention and do not limit the technical solutions described in the present invention; therefore, although this specification has described the present invention in detail with reference to the above respective examples, those of ordinary skill in the art should understand that the present invention can still be modified or equivalently replaced; and all technical solutions and their improvements that do not depart from the spirit and scope of the present invention shall be covered within the scope of the claims of the present invention.

Claims

1. An integrated method for detecting and removing Hg 2+ ​ It is characterized in that It includes the following steps: (1) Synthesis of Fe 3 O 4 -AuNCs@MOFs solution; S1. Dissolve 6-aza-2-thiothymine and sodium hydroxide in water, add chloroauric acid solution, stir in the dark to obtain a golden solution; after dialysis with a dialysis bag, perform freeze-drying to obtain a golden solid powder, which is ATT-AuNCs; S2. Dissolve the ATT-AuNCs obtained in step S1 in water, add ethanol and mix evenly; after centrifugation, take the precipitate and disperse it in methanol to obtain dispersion a; S3. Dissolve ferric chloride and ferrous chloride in water, pass N 2 to remove oxygen under stirring, then dropwise add ammonia water solution, and continue to stir and react for a period of time under certain temperature conditions; 2 ​ After the reaction, the precipitate was collected by magnetic separation, washed with water until neutral, and dried to obtain black Fe 3 O 4 solid powder; The Fe 3 O 4 solid powder was dispersed in water to obtain dispersion liquid b; S4. Add zinc nitrate hexahydrate to methanol to obtain a zinc nitrate hexahydrate methanol solution; then mix the dispersion a in step S2, the dispersion b in step S3 and the zinc nitrate hexahydrate methanol solution and perform the first ultrasonic treatment to obtain a mixed solution c; 2-Methylimidazole was added to methanol to obtain a 2-methylimidazole methanol solution; then the 2-methylimidazole methanol solution was added to the mixed solution c for the second ultrasound; after the ultrasound treatment, centrifugation was carried out, and the centrifuged precipitate was collected and centrifugally washed with methanol and water respectively; after washing, the precipitate was separated by a magnet and collected and washed with water again; after washing, the precipitate was separated and dried to obtain Fe 3 O 4 -AuNCs@MOFs solid powder, which was dispersed in water to obtain Fe 3 O 4 -AuNCs@MOFs solution; (2) Add the Fe obtained in step (1) 3 O 4 -AuNCs@MOFs solution was added with different gradient concentrations of Hg 2+ Solution mixture, a Fe 3 O 4 -AuNCs@MOFs solution corresponding to a concentration of Hg 2+ Solutions containing different concentrations of Hg 2+ a mixed solution; then adjusting the pH of the mixed solution with hydrochloric acid and sodium hydroxide solution, and incubating for a certain period of time under specific temperature conditions; Then, a solid precipitate is separated, and this solid precipitate is Hg 2+ Combined with Fe 3 O 4 -AuNCs@MOFs binding product, that is, Hg in the solution is removed 2+ ; (3) Detect the fluorescence signals of the mixed solutions with different concentrations of Hg in step (2) at 540 nm 2+ The fluorescence signal of the solution containing 0 ppb Hg 2+ is denoted as I 0 Similarly, the fluorescence signals corresponding to other Hg 2+ concentrations in ascending order of gradient concentration are denoted as I 1 、I 2 、…I n-1 、I n respectively, where n is a positive integer greater than or equal to 3; The differences between I 0 and I 1 、I 2 、…I n-1 、I n are taken, and the ratios of the differences to I 0 are denoted as y 1 、y 2 、…y n-1 、y n respectively. Based on y 1 、y 2 、…y n-1 、y n and the logarithms of their corresponding Hg 2+ concentrations, a standard curve is established; Finally, by measuring the fluorescence signal of the unknown solution at 540 nm and substituting it into the standard curve, the detection of the Hg 2+ concentration in the unknown solution can be achieved.

2. A method for integrated detection and removal of Hg according to claim 1 2+ method It is characterized in that In step S1 of step (1), the dosage relationship of 6-aza-2-thiothymine, sodium hydroxide, water and chloroauric acid solution is 0.1718 g: 0.12 g: 15 mL: 15 mL; the concentration of the chloroauric acid solution is 10 mg / mL -1 .

3. A method for integrated detection and removal of Hg according to claim 1 2+ thereof It is characterized in that In S1 of step (1), the time of stirring in the dark is 1 h; the conditions of dialysis are: a 50 kDa dialysis bag and a dialysis time of 24 h.

4. A method for integrally detecting and removing Hg according to claim 1 2+ and It is characterized in that In step S2 of step (1), the dosage relationship of the ATT-AuNCs, water and ethanol is 6 mg: 1 mL: 6 mL; the centrifugation speed is 12,000 rpm and the time is 15 min; the concentration of dispersion liquid a is 8 mg / mL -1 .

5. A method for integrally detecting and removing Hg according to claim 1 2+ and It is characterized in that In S3 of step (1), the dosage relationship of ferric chloride, ferrous chloride, water, and ammonia water solution is 2.35 g: 0.86 g: 100 mL: 10 mL; Among them, the volume concentration of the ammonia water solution is 25%.

6. A method for integrated detection and removal of Hg according to claim 1 2+ and It is characterized in that In S3 of step (1), the certain temperature condition is 80 °C, the reaction time is 30 min; the drying temperature is 60 °C; the concentration of dispersion liquid b is 3 mg / mL -1 .

7. A method for integrally detecting and removing Hg according to claim 1 2+ and It is characterized in that In S4 of step (1), the concentration of the zinc nitrate hexahydrate methanol solution is 30 mM; the dosage relationship of the dispersion a, the dispersion b and the zinc nitrate hexahydrate methanol solution is 1 ml: 1 ml: 10 ml; the dosage relationship of the mixed solution c and the 2-methylimidazole methanol solution is 10 - 12 ml: 10 ml; the concentration of the 2-methylimidazole methanol solution is 90 mM.

8. A method for integrated detection and removal of Hg according to claim 1 2+ thereof It is characterized in that In S4 of step (1), the frequency of the first ultrasound is 40KHz and the time is 5min; the frequency of the second ultrasound is 40KHz and the time is 10min; the rotation speed of the centrifugation is 8000rpm and the time is 10min; the concentration of the Fe 3 O 4 -AuNCs@MOFs solution is 5mg / mL -1 .

9. A method for integrated detection and removal of Hg according to claim 1 2+ and It is characterized in that In step (2), the concentration of the Fe 3 O 4 -AuNCs@MOFs solution is 5 mg mL -1 ; the concentration of the Hg 2+ solution is 0 - 2000 ppb, and the mixing volume ratio of the Fe 3 O 4 -AuNCs@MOFs solution to the Hg 2+ solution is 2:

5.

10. A method for integrated detection and removal of Hg according to claim 1 2+ as described It is characterized in that In step (2), the concentrations of the hydrochloric acid and the sodium hydroxide solution are 0.1 M, and the pH is adjusted to 2.0 - 6.0; when making up the volume, the volume ratio of water to the mixed solution is 1 - 8: 1; the incubation temperature is 25 °C, and the incubation time is 20 - 70 min.

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