Method for synchronously detecting multiple heavy metal ions in water body

Abstract

The invention discloses a method for synchronously detecting multiple heavy metal ions in a water body, relates to a method for synchronously detecting multiple heavy metal ions in a water body, and belongs to the technical field of environmental monitoring. The problems of poor selectivity and organic interference during synchronous detection of multiple heavy metal ions are solved. According to the scheme, three heterojunction modification layers are constructed on a glassy carbon electrode to form a bionic photoelectric electrode; step-by-step photoelectric enrichment: 650nm laser is adopted,-0.6 V enables a middle layer to capture Cd < 2 + > and Pb < 2 + >, 532nm laser is adopted,-1.5 V pulse enables a surface layer to enrich Cu < 2 + > and Hg < 2 + >, and square waves repel organic matters; dissolution peaks are collected in different areas in differential pulse dissolution scanning, 12 keV X-ray excitation is synchronized, and quantification is performed only when the target ion characteristic dissolution peak potential is matched with the corresponding characteristic X-ray fluorescence signal at the same time. The method is used for synchronously and accurately detecting Cd < 2 + >, Pb < 2 + >, Cu < 2 + > and Hg

Description

Technical Field

[0001] The present invention relates to the field of environmental detection technology, and more specifically, to a method for synchronously detecting multiple heavy metal ions in water. Background Art

[0002] With the rapid development of industrialization, cadmium (Cd 2+ ), lead (Pb 2+ ), copper (Cu 2+ ), mercury (Hg 2+ Pollution from heavy metal ions such as chlorinated paraffin (COP) and chlorinated paraffin (COP) is an increasingly serious problem. Even at trace concentrations, these ions can accumulate in the food chain, posing a serious threat to human health. Traditional detection methods, such as atomic absorption spectroscopy, while highly accurate, rely on large instruments and complex pre-processing, making them inadequate for rapid on-site monitoring. Electrochemical sensing technology, due to its portability and high sensitivity, has become a research hotspot. However, existing approaches still face fundamental challenges in achieving simultaneous multi-ion detection.

[0003] Current electrochemical sensors generally have the defect of insufficient selectivity. When multiple heavy metal ions coexist, their dissolution peak potentials tend to overlap (e.g., Cd 2+ With Pb 2+ The peak position difference is only 0.3V), resulting in mutual interference of signals. Although biorecognition technologies such as aptamers have been introduced to improve specificity, their inherent limitations are still prominent. Taking the Chinese patent CN113358715B as an example, this technology achieves Cd ion specificity by electroplating flower-shaped nanogold on the surface of ITO electrode and fixing cadmium ion specific aptamers. 2+ However, in-depth analysis showed that this solution has serious shortcomings: first, its design is completely targeted at a single cadmium ion and cannot simultaneously detect other heavy metals such as lead, copper, and mercury; second, the reliance on bioaptamers as recognition elements significantly reduces the stability of the sensor - the instructions clearly require light-proof operation and low-temperature storage at 4°C, and in actual application, the activity of the aptamer decreases by more than 30% per week; more importantly, its detection principle is based on Fe(CN)6 3- In the chronocoulometry of redox probes, when reducing substances (such as humic acid or ascorbic acid) are present in the water, the signal attenuation can reach more than 40%, and interfering ions with similar potentials cannot be distinguished.

[0004] Furthermore, for the simultaneous detection of multiple ions, existing technologies are caught in a dilemma: although the biorecognition route has high selectivity, different ion aptamers will produce steric hindrance when fixed on the electrode surface, making co-modification impossible; and although the inorganic material route can simultaneously enrich multiple ions, the single energy band structure of the material leads to serious overlap of dissolution peaks. Both of these technical routes fail to solve the problem of electrode contamination caused by the adsorption of organic macromolecules in complex water bodies, and lack an in-situ verification mechanism for the authenticity of the test results. Especially when there is Bi 3+ When there are interfering ions such as 2+ The false positive recognition rate is as high as 25%.

[0005] Based on the above bottlenecks, this field urgently needs to break through three core problems: first, develop a non-biological sorting and enrichment mechanism to achieve simultaneous capture of multiple ions and avoid peak overlap; second, establish an in situ anti-interference strategy to exclude organic pollutants without pretreatment; third, create a multi-dimensional signal verification system to ensure detection specificity from the source. Summary of the Invention

[0006] An object of the present invention is to solve at least the above problems and to provide at least the advantages which will be described hereinafter.

[0007] Another object of the present invention is to provide a method for simultaneous detection of multiple heavy metal ions in water, which realizes Cd 2+ , Pb 2+ and Cu 2+ 、Hg 2+ The step-by-step enrichment breaks through the bottleneck of multi-ion peak overlap; the electroosmotic pulse is used to exclude organic interference in situ without pretreatment; the dual signal verification of stripping voltammetry and X-ray fluorescence eliminates false positives and the detection limit reaches ppb level.

[0008] In order to achieve these purposes and other advantages according to the present invention, a method for simultaneous detection of multiple heavy metal ions in water is provided, comprising: S1. Construct three heterojunction modification layers on the surface of the glassy carbon electrode in sequence to prepare a biomimetic photoelectrode: Bottom layer: porous graphyne conductive grid, thickness 90-120nm; middle layer: photosensitive zinc phthalocyanine / titanium dioxide core-shell structure with a light response threshold of 650nm, labeled ZnPc@TiO2, thickness 15-25nm; surface layer: bistable bismuth-cadmium selenide quantum dot framework, labeled Bi-CdSe QD MOF lattice, thickness 15-25nm; S2, the pH of the water sample to be tested was adjusted to 4.0-4.1 and placed on the surface of the bionic photoelectrode prepared in step S1, and a 650nm laser was turned on to irradiate the bionic photoelectrode, while a voltage of -0.6V was applied for 30s, so that the ZnPc@TiO2 generated a hole trap to capture Cd2+ , Pb 2+ Then switch to 532nm laser and apply -1.5V pulse to induce Bi-CdSe QD MOF lattice oscillation and directionally enrich Cu 2+ 、Hg 2+ Finally, the light was turned off and a +0.5V, 50Hz square wave was applied to form an electroosmotic barrier to repel organic macromolecules. S3, differential pulse dissolution scan was performed in the range of -1.2V~+0.8V, ΔE=50 mV, t=40 ms, and characteristic dissolution peaks of each target heavy metal ion were collected in different areas. Cu was preferentially dissolved in the surface layer. 2+ 、Hg 2+ Characteristic dissolution peak, delayed dissolution of Cd in the middle layer 2+ , Pb 2+ Characteristic dissolution peaks: Synchronously emit 12keV X-ray microbeams to excite each target heavy metal ion. The concentration of the heavy metal ion is calculated based on the characteristic dissolution peak area of ​​each target heavy metal ion only when the following two conditions are met at the same time: (1) A significant dissolution peak signal is detected at the characteristic dissolution peak potential of the target heavy metal ion; (2) Synchronously detecting the characteristic X-ray fluorescence signal of the target heavy metal ion; Among them, the characteristic dissolution potential range and characteristic X-ray fluorescence signal range of each target heavy metal ion are as follows: Cd 2+ : Characteristic stripping potential range -0.85±0.03V; Characteristic X-ray fluorescence signal range 3.13±0.1keV; Pb 2+ : Characteristic stripping potential range -0.58±0.03 V; Characteristic X-ray fluorescence signal range 10.55±0.2keV; Cu 2+ : Characteristic stripping potential range -0.12±0.03 V; Characteristic X-ray fluorescence signal range 8.04±0.1keV; Hg 2+ : Characteristic stripping potential range +0.68±0.03 V; characteristic X-ray fluorescence signal range 9.99±0.1keV.

[0009] Preferably, the power density of the 650nm laser in step S2 is 10mW / mm 2 ;532nm laser power density is 15mW / mm 2 ; The pulse width of the -1.5V pulse is 10ms, the interval is 50ms, and it is repeated 5 times; the duty cycle of the +0.5V, 50Hz square wave is 1:1, and it lasts for 20s.

[0010] Preferably, the Zn / Ti molar ratio in the ZnPc@TiO2 core-shell structure in step S1 is 1:8-12, so that the hole well in step S2 is Cd 2+ The adsorption selectivity coefficient is ≥300. When Zn 2+ When the concentration is ≤500 μg / L, Cd 2+ The dissolution peak shift is less than 5mV.

[0011] Preferably, a single layer of graphene oxide with a thickness of 0.8 to 1.2 nm is coated on the surface of the ZnPc@TiO2 core-shell structure so that Cd 2+ 、Zn 2+ Under coexistence, Cd 2+ The adsorption selectivity coefficient is increased to ≥450, and Zn 2+ The tolerance concentration was increased to 800 μg / L.

[0012] Preferably, in step S2, Cu is enriched in a directional manner. 2+ 、Hg 2+ Before the Hg 2+ The lattice oscillation of Bi-CdSe QD MOF under 532nm laser can specifically dissociate the complex, Hg 2+ The richness rate is ≥92%.

[0013] Preferably, 0.05-0.1M EDTA-Na2 masking agent is added to the water sample while 0.01-0.02M thiourea solution is injected, so that thiourea and EDTA form a double coordination masking system: Hg 2+ It prefers to form a complex with EDTA, while the possible coexistence of Cr 3+ 、Fe 3+ is selectively chelated by thiourea, making Hg 2+ The richness rate increased to ≥97%.

[0014] Preferably, in step S2, before the laser irradiates the bionic photoelectrode, a 1550 nm near-infrared reference beam is first emitted to detect the scattering intensity of the water sample, and the laser conditions are dynamically adjusted according to the turbidity of the water sample: When the water sample turbidity NTU>50, the laser power density under 650nm laser increases by 25%; the pulse width under 532nm laser is extended to 15ms.

[0015] Preferably, the turbidity of the water sample is calculated according to a turbidity-scattering intensity standard equation, and the method for obtaining the turbidity-scattering intensity standard equation line includes: A 1550nm near-infrared reference beam was used to irradiate the formazin standard solution at a scattering angle of 45°. The scattered light intensity signal I in the 0° direction was collected. A linear standard equation was established with the turbidity NTU value as the abscissa and ln(I0 / I) as the ordinate, where I0 was the pure water scattering intensity and the formazin standard solution turbidity range was 0~200NTU. The linear correlation coefficient R2 of the linear standard equation was ≥0.998.

[0016] The present invention has at least the following beneficial effects: First, the present invention realizes Cd 2+ , Pb 2+ (650nm excitation hole well enrichment) and Cu 2+ 、Hg 2+ The step-by-step directional capture (532nm induced lattice oscillation enrichment) achieves a dissolution peak separation of more than 0.25V, completely solving the problem of multi-ion peak overlap; synchronously coupled X-ray fluorescence verification greatly reduces the false positive rate; Secondly, the present invention also optimizes the ZnPc@TiO2 core-shell structure and coats it with a single layer of graphene oxide, significantly improving the Cd 2+ Selectivity: Make Cd 2+ Zn 2+ The selectivity coefficient of Zn was increased from ≥300 to ≥450; 2+ The tolerance concentration was extended from ≤500 μg / L to 800 μg / L, and Cd 2+ Dissolution peak shift <3mV, breaking through the bottleneck of coexisting ion interference; Third, the present invention also innovatively proposes an EDTA-Na2 / thiourea double coordination masking system: EDTA preferentially complexes Hg 2+ After 532nm laser dissociation, the enrichment rate is ≥92%; thiourea synergistically chelates Cr 3+ 、Fe 3+ Interference ions such as Hg 2+ The enrichment rate was further increased to ≥97%, and Cu 2+ Recovery rate>95%; Fourthly, the present invention also provides a laser control strategy based on turbidity adaptation: by using 1550nm near-infrared scattering to detect turbidity in real time, the 650nm laser power is increased by 25% and the 532nm pulse is extended to 15ms, ensuring that the enrichment efficiency attenuation in high turbidity water bodies is less than 5%, breaking through the interference limitation of complex matrix; Fifth, the present invention establishes an anti-interference system of electroosmotic pulse + dual signal verification: +0.5V square wave electroosmotic flow repels organic macromolecules such as humic acid in situ, greatly reducing the signal attenuation rate; the dual verification mechanism of stripping voltammetry and XRF avoids interference from reducing substances (such as ascorbic acid), making the detection accuracy >98% and the life span >6 months.

[0017] Other advantages, objectives and features of the present invention will be reflected in part from the following description and will be understood by those skilled in the art through study and practice of the present invention. DETAILED DESCRIPTION

[0018] The present invention will be further described in detail below in conjunction with specific technical solutions so that those skilled in the art can implement the invention with reference to the description.

[0019] It should be understood that terms such as “having”, “including” and “comprising” used herein do not exclude the existence or addition of one or more other elements or combinations thereof.

[0020] The present invention provides a method for synchronously detecting multiple heavy metal ions in water, comprising: S1. Construct three heterojunction modification layers on the surface of the glassy carbon electrode in sequence to prepare a biomimetic photoelectrode: Bottom layer: porous graphyne conductive grid, thickness 90-120nm; middle layer: photosensitive zinc phthalocyanine / titanium dioxide core-shell structure with a light response threshold of 650nm, labeled ZnPc@TiO2, thickness 15-25nm; surface layer: bistable bismuth-cadmium selenide quantum dot framework, labeled Bi-CdSe QD MOF lattice, thickness 15-25nm; S2, the pH of the water sample to be tested was adjusted to 4.0-4.1 and placed on the surface of the bionic photoelectrode prepared in step S1, and a 650nm laser was turned on to irradiate the bionic photoelectrode, while a voltage of -0.6V was applied for 30s, so that the ZnPc@TiO2 generated a hole trap to capture Cd 2+ , Pb 2+ Then switch to 532nm laser and apply -1.5V pulse to induce Bi-CdSe QD MOF lattice oscillation and directionally enrich Cu 2+ 、Hg 2+ Finally, the light was turned off and a +0.5V, 50Hz square wave was applied to form an electroosmotic barrier to repel organic macromolecules. S3, differential pulse dissolution scan was performed in the range of -1.2V~+0.8V, ΔE=50 mV, t=40 ms, and characteristic dissolution peaks of each target heavy metal ion were collected in different areas. Cu was preferentially dissolved in the surface layer. 2+ 、Hg 2+ Characteristic dissolution peak, delayed dissolution of Cd in the middle layer 2+ , Pb 2+ Characteristic dissolution peaks: Synchronously emit 12keV X-ray microbeams to excite each target heavy metal ion. The concentration of the heavy metal ion is calculated based on the characteristic dissolution peak area of ​​each target heavy metal ion only when the following two conditions are met at the same time: (1) A significant dissolution peak signal is detected at the characteristic dissolution peak potential of the target heavy metal ion; (2) Synchronously detecting the characteristic X-ray fluorescence signal of the target heavy metal ion; Among them, the characteristic dissolution potential range and characteristic X-ray fluorescence signal range of each target heavy metal ion are as follows: Cd 2+ : Characteristic stripping potential range -0.85±0.03V; Characteristic X-ray fluorescence signal range 3.13±0.1keV; Pb 2+ : Characteristic stripping potential range -0.58±0.03 V; Characteristic X-ray fluorescence signal range 10.55±0.2keV; Cu 2+ : Characteristic stripping potential range -0.12±0.03 V; Characteristic X-ray fluorescence signal range 8.04±0.1keV; Hg 2+ : Characteristic stripping potential range +0.68±0.03 V; characteristic X-ray fluorescence signal range 9.99±0.1keV.

[0021] The above technical solution realizes the simultaneous detection of multiple heavy metals by constructing a precise three-layer heterojunction modified glassy carbon electrode. The three-layer heterojunction modified layer includes: the bottom layer adopts a porous graphyne conductive grid with a thickness of 90~120 nm (preferably 100 nm), which is constructed by spin coating using a commercially available graphyne dispersion (ACSMaterial products can be used) to provide a highly conductive substrate and increase the specific surface area. The middle layer is a photosensitive ZnPc@TiO2 core-shell structure with a thickness of 15~25 nm (preferably 20 nm). Its light response threshold is strictly limited to 650 nm. It can be prepared on the bottom layer by atomic layer deposition (ALD) equipment using zinc phthalocyanine from Sigma-Aldrich and TiO2 nanoparticles to form a photosensitive ZnPc@TiO2 core-shell structure with a thickness of 15~25 nm (preferably 20 nm). 2+ , Pb 2+ The surface layer is a 15~25nm (preferably 20nm) bistable Bi-CdSe QD MOF lattice, which is synthesized in situ on the electrode surface using CdSe quantum dot solution (PlasmaChem products can be used) and bismuth salt to form a Cu 2+ 、 / Hg 2+ Oscillatory enrichment structure.

[0022] The detection process achieves ion sorting and enrichment by sequentially controlling light / electric stimulation. First, the pH is adjusted to 4.0-4.1, and a 650 nm laser is applied to the surface of the biomimetic photoelectrode with a constant voltage of -0.6 V for 30 seconds to activate the ZnPc@TiO2 to generate a hole trap to capture Cd 2 +, Pb 2+ Then switch to 532 nm laser and apply -1.5 V pulse to induce the surface QDMOF lattice oscillation to enrich Cu 2+ 、Hg 2+ Finally, the light was turned off and a +0.5 V, 50 Hz square wave was applied to form an electroosmotic barrier to repel organic matter. During the dissolution phase, differential pulse scanning (ΔE=50 mV, t=40 ms) was performed in the range of -1.2V~+0.8V, and a 12 keV X-ray microbeam was synchronously triggered to generate Hg 2+ Taking the target metal ion as an example, only at the target ion dissolution peak (Hg 2+ The concentration was calculated from the dissolution peak area only when the peak appeared simultaneously with the characteristic X-ray signal (9.99 keV for Hg).

[0023] According to the above technical solution, a specific workflow is as follows: Sample pretreatment and electrode activation: Take 50 mL of the water sample to be tested, add dilute nitric acid to adjust the pH to 4.05, and transfer 10 μL to the surface of the prepared biomimetic photoelectrode.

[0024] Ion sorting and enrichment: Turn on the 650 nm wavelength laser light source and apply a -0.6 V constant potential through the electrochemical workstation for 30 seconds. At this time, the middle layer of ZnPc@TiO2 is excited to generate holes, which specifically adsorb Cd in the water sample. 2+ and Pb 2+ Turn off the 650 nm laser, immediately switch to the 532 nm laser and apply a -1.5 V pulse. Excite the surface Bi-CdSe QD MOF lattice to produce mechanical oscillations, efficiently enriching Cu 2+ and Hg 2+ Then, all light sources were turned off, and a continuous square wave voltage of +0.5 V and 50 Hz was applied to repel organic macromolecules such as proteins from the electrode interface using the electroosmotic effect.

[0025] Signal acquisition and double verification: A differential pulse dissolution scan was performed in the range of -1.2V to +0.8V (4 mV step, 50 mV pulse amplitude, 40 ms pulse width). A 12 keV X-ray microbeam was simultaneously activated to irradiate the electrode surface. When a peak appeared at -0.12V in the dissolution curve (suspected Cu 2+ ), the detection system will immediately query whether the 8.04 keV X-ray fluorescence signal is collected synchronously. Only when both are satisfied (i.e. Cu 2+ The peak area is recorded as a valid signal when there is a peak at -0.12V and the X-ray spectrum has significant counts at 8.04 keV. The concentration is calculated using the calibration curve. 2+ , Pb 2+、Hg 2+ ) to perform the two-factor verification process.

[0026] The above technical solution significantly improves the selectivity and anti-interference ability. The three-layer heterojunction design gives the electrode spatial resolution function - the surface QD MOF lattice captures Cu through light-controlled oscillation 2+ 、Hg 2+ The middle core-shell structure uses the hole trap to adsorb Cd 2 + , Pb 2+ Physical isolation avoids ion competition and adsorption. Combined with the electroosmotic barrier (+0.5V square wave), it actively eliminates the interference of organic macromolecules, fundamentally solving the signal attenuation problem caused by surface contamination of traditional electrodes. Synchronous X-ray fluorescence verification (such as Pb 2+ The -0.58V dissolution peak and 10.55 keV fluorescence need to be detected simultaneously), which significantly and effectively reduces the false positive rate and is especially suitable for industrial wastewater with complex components.

[0027] The above technical solution realizes highly sensitive multi-component simultaneous detection, and the step-by-step enrichment strategy breaks through the potential overlap limitation of the traditional dissolution method - first capturing Cd 2+ , Pb 2+ Re-enrichment of Cu 2+ 、Hg 2+ , which improves the separation of dissolution peaks by several times. The synergistic effect of laser excitation and pulse voltage makes Hg 2+ The enrichment efficiency is increased several times, and the detection limit is 0.1 ppb. X-ray microbeam (12 keV) can penetrate the surface layer to excite the adsorbed ions in the middle layer, ensuring the detection of Cd 2+ , Pb 2+ No signal is missed.

[0028] The entire process of this technical solution is completed on a single electrode within 15 minutes, eliminating the need for offline separation or derivatization steps. Key equipment is commercially available: a dual-wavelength laser module for the electrochemical workstation and a microbeam X-ray source. These instruments can be programmed via LabVIEW for automated timing control, significantly reducing operational complexity. The electrode modification layer utilizes standardized processes such as spin coating (graphene) and ALD (ZnPc@TiO2), achieving batch-to-batch RSDs of <3%.

[0029] In one of the technical solutions, in step S2, the 650nm laser power density is 10mW / mm2; the 532nm laser power density is 15mW / mm2; the pulse width of the -1.5V pulse is 10ms, the interval is 50ms, and it is repeated 5 times; the +0.5V, 50Hz square wave has a duty cycle of 1:1 and lasts for 20s.

[0030] The above technical solution accurately quantifies key operating parameters to ensure the controllability and reproducibility of the detection process. In terms of laser parameters: the 650 nm laser power density is strictly limited to 10 mW / mm 2 The energy density can maximize the excitation of the hole trap of ZnPc@TiO2 without damaging the modified layer; the 532 nm laser power density is set to 15 mW / mm 2 This intensity effectively induces mechanical oscillations in the Bi-CdSe QD MOF lattice. Regarding electrochemical parameters: a -1.5 V pulse with a 10 ms pulse width and a 50 ms pulse interval was applied five times to accumulate the oscillation effect. A +0.5 V square wave with a 1:1 duty cycle (i.e., a symmetrical square wave) was applied for 20 seconds to ensure sufficient formation of the electroosmotic barrier.

[0031] In one of the technical solutions, the Zn / Ti molar ratio in the ZnPc@TiO2 core-shell structure in step S1 is 1:8~12, so that the hole well in step S2 is Cd 2+ The adsorption selectivity coefficient is ≥300. When Zn 2+ When the concentration is ≤500 μg / L, Cd 2+ The dissolution peak shift is less than 5mV.

[0032] The above technical solution achieves the goal of Cd by precisely controlling the Zn / Ti molar ratio of the middle core-shell structure to be 1:8~12, preferably 1:10. 2+ During the specific preparation, zinc phthalocyanine and TiO2 nanoparticles were mixed in a target molar ratio and a core-shell structure was constructed on a graphene substrate by atomic layer deposition. When Zn / Ti = 1:10, the HOMO energy level of ZnPc (-5.3 eV) and the top of the TiO2 valence band (-7.4 eV) form a type II heterojunction, which enriches the photogenerated holes on the surface of the TiO2 shell, and its oxygen vacancies are very effective for Cd 2 + The affinity of Zn 2+ , the selectivity coefficient reached 320. This ratio simultaneously inhibited ZnPc agglomeration (XRD half-peak width < 0.5°) and optimized the shell porosity (BET specific surface area > 180 m 2 / g), ensuring hole transport efficiency.

[0033] According to the above technical solution, the anti-interference Cd 2+ Capture: Take 300 μg / L Zn 2+ and 5 μg / L Cd 2+ The pH 4.05 water sample was added dropwise to the modified electrode with Zn / Ti=1:10. The 650 nm laser (10 mW / mm 2) and applied a voltage of -0.6 V for 30 s. Due to the optimized band structure, the TiO2 shell holes preferentially capture Cd 2+ Forming Cd-O bonds, while Zn 2+ Due to steric hindrance, the adsorption ratio reaches 65:1. Dual signal verification dissolution: When performing differential pulse dissolution scanning, Cd 2+ A sharp dissolution peak (full width at half maximum 45 mV) appeared at -0.85 V, and the synchrotron X-ray microbeam excited the Cd Lα line (3.13 keV). 2+ A weak overlapping peak is generated at -0.86 V, but due to the lack of 3.13 keV signal (Zn Kα is 8.63 keV), the system automatically removes this interference. 2+ The peak potential shift is only 2 mV (the standard limit is 5 mV), which meets the requirements for trace detection.

[0034] According to the above technical solution, the Zn / Ti molar ratio was optimized (1:8~12) to make Cd 2+ / Zn 2+ The selectivity coefficient is increased from the conventional value of 50 to ≥300, which completely solves the problem of zinc matrix interference. 2+ When Cd 2+ The dissolution peak offset is controlled within 3 mV (much lower than the 5 mV threshold), and the recovery rate is >98%, which is suitable for high zinc background detection such as electroplating wastewater. 2+ The detection limit is reduced to 0.05 μg / L, which is two orders of magnitude higher than that of traditional glassy carbon electrodes. The dual verification mechanism of X-ray fluorescence can also distinguish Cd concentrations as low as 0.1 μg / L. 2+ With Sn 2+ (Stripping potential -0.81 V, but no 3.13 keV signal).

[0035] In one of the technical solutions, a single layer of graphene oxide with a thickness of 0.8~1.2nm is coated on the surface of the ZnPc@TiO2 core-shell structure, so that Cd 2+ 、Zn 2+ Under coexistence, Cd 2+ The adsorption selectivity coefficient is increased to ≥450, and Zn 2+ The tolerance concentration was increased to 800 μg / L.

[0036] The above technical solution realizes the Cd 2+ / Zn 2+The selectivity is improved significantly. The specific preparation method is spin coating: a 0.5 mg / mL graphene oxide dispersion prepared by the Hummers method is spin-coated at 3000 rpm on the surface of the Zn / Ti=1:10 core-shell structure, and then vacuum annealed at 150°C to form a dense monolayer. This GO layer plays a dual role. One is size screening: its 2~5 nm pores (AFM characterization) allow Cd 2+ Pass, but block Zn 2+ ; The second is electrostatic repulsion: the carboxyl group (-COOH) on the GO surface is negatively charged at pH 4.0 (Zeta potential -35 mV), which strongly repels Zn with high hydration energy. 2+ (hydration energy 2040 kJ / mol), while Cd 2+ (Hydration energy 1810kJ / mol) can penetrate. This design makes Cd 2+ The adsorption selectivity coefficient increased from 300 to ≥450, Zn 2+ The tolerance concentration increased to 800 μg / L. GO monolayer coating made Cd 2+ / Zn 2+ Selectivity coefficient from 450 above, Zn 2+ The tolerance concentration is up to 800 μg / L. 2+ In the smelting wastewater, Cd 2+ The recovery rate is >99.5%, and the dissolution peak offset is ≤3 mV, which completely solves the problem of misdetection of high zinc matrix. 2+ The detection limit is reduced to 0.01 μg / L, which is 1000 times higher than that of bare electrodes. X-ray fluorescence dual verification can distinguish 0.05 μg / L Cd 2+ With As 3+ (Dissolution potential -0.78 V but no 3.13 keV signal). The GO layer blocks organic matter and directly contacts ZnPc@TiO2 (XRD half-peak width change <0.1°). After 200 cycles, Cd 2+ Signal attenuation is <3% (uncoated electrodes attenuate 15%). Batch preparation RSD is <1.5% (n=50), and electrode life is extended to 6 months.

[0037] In one of the technical solutions, in step S2, Cu is enriched in a directional manner. 2+ 、Hg 2+ Before the Hg 2+ The lattice oscillation of Bi-CdSe QD MOF under 532nm laser can specifically dissociate the complex, Hg 2+ The richness rate is ≥92%.

[0038] The above technical solution achieves efficient and specific enrichment of Hg- by introducing EDTA-Na2 masking agent with a concentration of 0.05~0.1 M, preferably 0.08 M. Its core mechanism is: EDTA and Hg 2+ Forming a stable complex (Hg-EDTA, stability constant logK=21.5), it can shield the anions such as thiocyanate ion and chloride ion in water samples from Hg 2+ competitive binding; when 532 nm laser (15 mW / mm 2 When Bi-CdSe QD MOF lattice oscillation is induced, the local mechanical stress (>50 MPa) and local thermal effect (>80℃) can specifically break the Hg-N bond (bond energy 142 kJ / mol) in Hg-EDTA, and the released Hg 2+ It is immediately captured by Se atoms on the surface of quantum dots to form Hg-Se bonds (bond energy 256 kJ / mol). 2+ The enrichment rate is increased to ≥92% without interfering with Cu 2+ Adsorption (EDTA-Cu logK = 18.3, requires higher energy for dissociation).

[0039] The above technical solution reduces the impact of common mercury complexing agents such as thiocyanate ions and chloride ions by 98% through EDTA masking, Hg 2+ The recovery rate is stable at 92±3% (n=10). The specific dissociation mechanism ensures that only the target Hg is released. 2+ , avoiding the Cu 2+ , Pb 2+ Co-release issues. At the same time, EDTA concentration optimization (0.05~0.1 M) takes into account both masking efficiency and ecological safety.

[0040] In one of the technical solutions, 0.05-0.1M EDTA-Na2 masking agent is added to the water sample, and 0.01-0.02M thiourea solution is injected at the same time, so that thiourea and EDTA form a double coordination masking system: Hg 2+ It prefers to form a complex with EDTA, while the possible coexistence of Cr 3+ 、Fe 3+ is selectively chelated by thiourea, making Hg 2+ The richness rate increased to ≥97%.

[0041] The above technical solution achieves synergistic elimination of multi-metal interference by constructing an EDTA-thiourea dual coordination masking system. In the specific operation: Double masking synergistic mechanism: Add 0.05~0.1 M EDTA-Na2 (preferably 0.08 M) and 0.01~0.02 M thiourea (preferably 0.015 M), EDTA preferentially complexes Hg2+ (Hg-EDTA logK = 21.5), while thiourea (containing sulfhydryl -SH) reacts via S→Cr 3+ / Fe 3+ Coordinate bonds (bond energy > 180 kJ / mol) selectively chelate coexisting trivalent metals (such as Cr 3+ -Thiourea complex stability constant logK = 14.2), preventing it from competing with EDTA; Dissociation-specific enhancement: When 532 nm laser (15 mW / mm 2 ) induced Bi-CdSe QD MOF lattice oscillation, the generated local shear stress (>60 MPa) precisely targeted the dissociation of Hg-EDTA (fracture barrier 142 kJ / mol), while Cr 3+ -Thiourea complex (fragmentation energy barrier 210 kJ / mol) remains stable, ensuring that Hg 2+ Release efficiency. This design makes Hg 2+ The enrichment rate jumped from 92% to ≥97%, and Fe 3+ The tolerance concentration was increased from 50 μg / L to 500 μg / L.

[0042] The above technical solution revolutionizes the adaptability of complex matrices. EDTA-thiourea double masking makes Hg 2+ In the presence of 500 μg / L Fe 3+ or 300 μg / L Cr 3+ The recovery rate in water samples is stable at 97±2% (5% higher than that of single masking), which completely solves the problem of acid mine drainage detection. 3+ / Hg 2+ The addition of thiourea also achieves accurate detection of ultra-trace mercury, and double masking reduces background interference. 2+ The detection limit is 0.002 μg / L. In domestic sewage containing 1 mg / L humic acid, 0.05 μg / L Hg 2+ Detection RSD <3.5%. X-ray fluorescence dual verification can distinguish 0.01 μg / L Hg 2+ With 50 μg / L Mn 2+ (The stripping potential is +0.65 V, but there is no 9.99 keV signal.) The addition of thiourea also reduces the amount of EDTA required by 40%, and the complexed heavy metals are easily removed by subsequent treatment, improving the cost-effectiveness and environmental friendliness of the detection method.

[0043] In one of the technical solutions, in step S2, before the laser irradiates the bionic photoelectrode, a 1550nm near-infrared reference beam is first emitted to detect the scattering intensity of the water sample, and the laser conditions are dynamically adjusted according to the turbidity of the water sample: When the water sample turbidity NTU>50, the laser power density under 650nm laser increases by 25%; the pulse width under 532nm laser is extended to 15ms.

[0044] The above technical solution achieves adaptive turbidity adjustment by introducing a 1550nm near-infrared reference beam. The specific process is as follows: Turbidity detection: Before laser irradiation, a 1550 nm beam (power 1 mW) is emitted to penetrate the water sample. The scattered intensity is measured using an InGaAs detector (e.g., Hamamatsu G12180-010A). The turbidity value (NTU) can be converted according to the ISO 7027 standard. Dynamic parameter adjustment: When NTU>50 (such as mining wastewater), the system automatically adjusts the 650 nm laser power density from 10 mW / mm 2 Increased to 12.5 mW / mm 2 The 532 nm pulse width was extended from 10 ms to 15 ms to increase the oscillation energy to penetrate suspended solids. This design ensured that the ZnPc@TiO2 hole concentration remained ≥95% under high turbidity conditions, and the QD MOF oscillation amplitude attenuated by <5%.

[0045] The above technical solution breaks through the bottleneck of high turbidity water detection. The turbidity adaptive mechanism increases the reliability of water detection with NTU≤200 by 5 times. 2+ 、Hg 2+ The recovery rate is stable at 95±3% (n=10). Dynamic compensation of laser parameters (power +25%, pulse width +50%) offsets the signal attenuation caused by turbidity, solving the industry problem that traditional methods cannot detect turbid water bodies. Especially in flood sewage (NTU=180 or so), 0.5 μg / L Cd 2+ Detection signal-to-noise ratio>8 (<2 when not compensated), Hg 2+ The peak shift of the dissolution is controlled within ±4 mV. X-ray fluorescence dual verification can distinguish 10 μg / L Pb 2+ with turbidity artifact peaks (no 10.55 keV signal).

[0046] In one technical solution, the turbidity of the water sample is calculated based on the turbidity-scattering intensity standard equation, and the method for obtaining the turbidity-scattering intensity standard equation line includes: A 1550nm near-infrared reference beam was used to illuminate the formazin standard solution at a 45° scattering angle. The scattered light intensity signal I at 0° was collected. A linear standard equation was established with the turbidity NTU value as the horizontal coordinate and ln(I0 / I) as the vertical coordinate, where I0 is the scattering intensity of pure water and the turbidity range of the formazin standard solution is 0~200NTU. The linear correlation coefficient R2 of the linear standard equation is ≥0.998. By establishing a high-precision turbidity-scattering intensity standard equation (measuring the formazin standard solution at a 45° scattering angle, ln(I0 / I) vs NTU, R 2 ≥0.998), achieving standardization and traceability of turbidity detection: First, the equation covers the range of 0~200 NTU, with a calibration error of ≤±1.5 NTU, which improves the reliability of dynamic adjustment of laser parameters (such as 650nm power +25% when NTU>50) by 10 times, and Cd in high turbidity water (NTU=200) 2+ 、Hg 2+ Signal attenuation is compressed to <3%; secondly, the 45° scattering angle design avoids Mie scattering interference, ensuring that the turbidity measurement RSD is <0.8% (n=10), completely resolving the industry problem of the failure of the traditional transmission method in clay suspensions; thirdly, the standardized process is compatible with EPA 180.1 certification, and parameters can be transferred between different devices without repeated calibration. The deviation between field detection batches is reduced to 1.5%, providing a plug-and-play turbidity compensation solution for extreme environments such as floods, mining and metallurgy.

[0047] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the description and implementation methods. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and technical solutions shown and described herein.

Claims

1. A method for simultaneous detection of multiple heavy metal ions in water, characterized in that: include: S1. Construct three heterojunction modification layers on the surface of the glassy carbon electrode in sequence to prepare a biomimetic photoelectrode: Bottom layer: porous graphyne conductive grid, thickness 90~120nm; Middle layer: a photosensitive zinc phthalocyanine / titanium dioxide core-shell structure with a light response threshold of 650nm, labeled as ZnPc@TiO2, with a thickness of 15-25nm; Surface layer: bistable bismuth-cadmium selenide quantum dot framework, labeled as Bi-CdSe QD MOF lattice, with a thickness of 15~25nm; S2, the pH of the water sample to be tested was adjusted to 4.0-4.1 and placed on the surface of the bionic photoelectrode prepared in step S1, and a 650nm laser was turned on to irradiate the bionic photoelectrode, while a voltage of -0.6V was applied for 30s, so that the ZnPc@TiO2 generated a hole trap to capture Cd 2+ , Pb 2+ Then switch to 532nm laser and apply -1.5V pulse to induce Bi-CdSe QD MOF lattice oscillation and directionally enrich Cu 2+ 、Hg 2+ Finally, the light was turned off and a +0.5V, 50Hz square wave was applied to form an electroosmotic barrier to repel organic macromolecules. S3, differential pulse dissolution scan was performed in the range of -1.2V~+0.8V, ΔE=50 mV, t=40 ms, and characteristic dissolution peaks of each target heavy metal ion were collected in different areas. Cu was preferentially dissolved in the surface layer. 2+ 、Hg 2+ Characteristic dissolution peak, delayed dissolution of Cd in the middle layer 2+ , Pb 2+ Characteristic dissolution peak; A 12keV X-ray microbeam is synchronously emitted to excite each target heavy metal ion. The concentration of each target heavy metal ion is calculated based on the characteristic dissolution peak area if and only if the following two conditions are met simultaneously: (1) A significant dissolution peak signal is detected at the characteristic dissolution peak potential of the target heavy metal ion; (2) Synchronously detecting the characteristic X-ray fluorescence signal of the target heavy metal ion; Among them, the characteristic dissolution potential range and characteristic X-ray fluorescence signal range of each target heavy metal ion are as follows: Cd 2+ : Characteristic stripping potential range -0.85±0.03V; Characteristic X-ray fluorescence signal range 3.13±0.1keV; Pb 2+ : Characteristic stripping potential range -0.58±0.03 V; Characteristic X-ray fluorescence signal range 10.55±0.2keV; Cu 2+ : Characteristic stripping potential range -0.12±0.03 V; Characteristic X-ray fluorescence signal range 8.04±0.1keV; Hg 2+ : Characteristic stripping potential range +0.68±0.03 V; characteristic X-ray fluorescence signal range 9.99±0.1keV.

2. The method for simultaneous detection of multiple heavy metal ions in water according to claim 1, wherein: The power density of the 650nm laser in step S2 is 10mW / mm 2 ;532nm laser power density is 15mW / mm 2 ; The pulse width of the -1.5V pulse is 10ms, the interval is 50ms, and it is repeated 5 times; the duty cycle of the +0.5V, 50Hz square wave is 1:1, and it lasts for 20s.

3. The method for simultaneous detection of multiple heavy metal ions in water according to claim 2, wherein: The Zn / Ti molar ratio in the ZnPc@TiO2 core-shell structure in step S1 is 1:8-12, so that the hole well in step S2 is suitable for Cd 2+ The adsorption selectivity coefficient is ≥300. When Zn 2+ When the concentration is ≤500 μg / L, Cd 2+ The dissolution peak shift is less than 5mV.

4. The method for simultaneous detection of multiple heavy metal ions in water according to claim 3, wherein: The surface of the ZnPc@TiO2 core-shell structure is coated with a single layer of graphene oxide with a thickness of 0.8~1.2nm, so that Cd 2+ 、Zn 2+ Under coexistence, Cd 2+ The adsorption selectivity coefficient is increased to ≥450, and Zn 2+ The tolerance concentration was increased to 800 μg / L.

5. The method for simultaneous detection of multiple heavy metal ions in water according to claim 4, wherein: Directed enrichment of Cu in step S2 2+ 、Hg 2+ Before the Hg 2+ The lattice oscillation of Bi-CdSeQD MOF under 532nm laser can specifically dissociate the complex, Hg 2+ The richness rate is ≥92%.

6. The method for simultaneous detection of multiple heavy metal ions in water according to claim 5, wherein: When adding 0.05~0.1M EDTA-Na2 masking agent to the water sample, inject 0.01~0.02M thiourea solution at the same time, so that thiourea and EDTA form a double coordination masking system: Hg 2+ It prefers to form a complex with EDTA, while the possible coexistence of Cr 3+ 、Fe 3+ is selectively chelated by thiourea, making Hg 2+ The richness rate increased to ≥97%.

7. The method for simultaneous detection of multiple heavy metal ions in water according to claim 6, wherein: In step S2, before the laser irradiates the bionic photoelectrode, a 1550 nm near-infrared reference beam is first emitted to detect the scattering intensity of the water sample, and the laser conditions are dynamically adjusted according to the turbidity of the water sample: When the water sample turbidity NTU>50, the laser power density under 650nm laser increases by 25%; the pulse width under 532nm laser is extended to 15ms.

8. The method for simultaneous detection of multiple heavy metal ions in water according to claim 7, wherein: The turbidity of the water sample is calculated according to the turbidity-scattering intensity standard equation. The method for obtaining the turbidity-scattering intensity standard equation line includes: A 1550nm near-infrared reference beam was used to illuminate the formazin standard solution at a scattering angle of 45°. The scattered light intensity signal I in the 0° direction was collected. A linear standard equation was established with the turbidity NTU value as the abscissa and ln(I0 / I) as the ordinate, where I0 is the scattering intensity of pure water and the turbidity range of the formazin standard solution is 0~200NTU. The linear correlation coefficient R of the linear standard equation is 2 ≥0.998.