A Hg 2+ and Cd 2+ differential detection and adsorption removal method

Abstract

The application discloses a Hg 2+ and Cd 2+ differential detection and adsorption removal method, and a zinc-based metal organic framework loaded with silver nanoparticles (ZIF-AgNPs) is prepared by an in-situ reduction method, has oxidase-like activity, and can catalyze color development of 3,3',5,5'-tetramethylbenzidine (TMB). 2+ or Cd 2+ can destroy the ZIF structure and inhibit the activity, and makes the system fade. By utilizing the differential response of the two ions to pH, a multi-channel colorimetric array is constructed, and machine learning is combined to realize classification identification and quantitative detection of the two ions. Meanwhile, the material can efficiently adsorb and remove heavy metal ions in water through coordination, integrates visual detection, intelligent identification and adsorption, and can be widely applied to the fields of environmental monitoring, food safety detection and heavy metal pollution treatment.

Description

Technical Field

[0001] This invention belongs to the field of food safety and testing, and environmental analysis and monitoring technology, specifically relating to an Hg-based colorimetric sensor array based on ZIF-AgNPs. 2+ and Cd 2+ Differentiate between detection and adsorption removal methods. Background Technology

[0002] Aquatic products easily accumulate heavy metal pollutants from the environment during their growth, making them a significant source of heavy metal exposure for humans. Among these, mercury ions (Hg) are particularly problematic. 2+ ) and cadmium ions (Cd) 2+ Both Hg and other substances are highly toxic and can damage the nervous system and the function of various enzyme proteins. In real aquatic product samples, Hg... 2+ and Cd 2+ Hg typically coexists at low concentrations and readily complexes or competes for adsorption with proteins, amino acids, and various inorganic salts, leading to problems such as strong background interference, complex speciation, and signal drift in the detection system. Therefore, it is necessary to construct a method that can realize Hg in complex matrices. 2+ Cd 2+ Rapid, sensitive, and distinguishable analytical strategies are of great significance for the safety monitoring and risk warning of aquatic products.

[0003] Currently, advanced instrumentation techniques such as high-performance liquid chromatography (HPLC), atomic absorption spectrometry (AAS), and inductively coupled plasma mass spectrometry (ICP-MS) are widely used for heavy metal detection. Although these methods offer high sensitivity and accuracy, they generally suffer from limitations such as cumbersome detection procedures, long analysis cycles, high costs, and complex operations. In contrast, colorimetric analysis offers advantages such as visual readout, ease of operation, and lower cost, demonstrating promising potential for on-site detection. However, most existing colorimetric sensing systems are primarily designed for single analytes, making it difficult to detect Hg in complex sample matrices. 2+ and Cd 2+ Distinguishing between them remains quite difficult. For example, the previously granted patent CN120761369B discloses a data-enhanced colorimetric detection scheme based on silver-based nanozymes and machine learning. This scheme utilizes a covalent organic framework to load silver nanoparticles to construct nanozymes for detecting mercury ions (Hg). 2+ This technology utilizes colorimetric detection of silver-based nanozymes, combined with absorbance and RGB color information for data analysis, to improve detection sensitivity and expand the detection range. This approach provides a valuable framework for heavy metal ion detection using silver-based nanozymes combined with data analysis, but its technical focus is primarily on Hg. 2+ Rapid detection of a single target, expanded detection range, and optimized detection performance for Hg in complex matrices. 2+ with cd 2+There is currently no specific technical approach for distinguishing between these two types of heavy metal ions. Furthermore, existing research and technical solutions focus more on improving detection capabilities, with relatively less attention paid to the adsorption and removal of target heavy metal ions. It should be noted that the technical problem to be solved and the technical implementation route of this application are different from those of the authorized patent CN120761369B. The technical focus of CN120761369B is on constructing nanozymes using silver nanoparticles loaded with a covalent organic framework, combining absorbance and RGB color information with machine learning algorithms to achieve the adsorption and removal of mercury ions (Hg... 2+ This application focuses on rapid detection of a single target and expansion of the detection range; however, it does not aim at the quantitative enhancement detection of a single heavy metal ion, but rather at Hg in complex sample matrices. 2+ with cd 2+ In low-concentration coexistence scenarios, the focus is on addressing the differentiation and identification of two heavy metal ions. This application employs a ZIF-L composite material system loaded with Ag nanoparticles and introduces multiple pH sensing units to construct a differentiated response array to obtain Hg... 2+ and Cd 2+ The application provides multidimensional colorimetric response information under different conditions. In terms of data processing, its purpose is to distinguish different ion categories, rather than simply expanding the detection range and sensitivity of a single target ion. Furthermore, this application also considers the adsorption and removal function of the material for target heavy metal ions, thus differing significantly from CN120761369B in terms of material carrier, detection object, signal construction method, data processing purpose, and technical effect.

[0004] In recent years, array detection strategies have been gradually introduced into the field of colorimetric analysis. By constructing multiple sensing units with different response characteristics, the ability to distinguish and identify analytes with similar structures or properties can be improved. To further enhance the sensitivity and discrimination ability of array detection systems, the rational design and selection of sensing elements are crucial. Metal-organic frameworks (MOFs), due to their high specific surface area, tunable pore structure, and designable coordination environment, provide an excellent platform for the selective enrichment of metal ions and the regulation of interfacial microenvironments. Especially those composed of Zn... 2+ ZIF-based metal-organic frameworks constructed with imidazole ligands exhibit good stability and functionalizability in aqueous systems, making them suitable for the adsorption and enrichment of target ions in complex samples. On the other hand, Ag-based nanomaterials possess excellent enzyme-like catalytic activity, capable of catalyzing the oxidation of chromogenic substrates under mild conditions, thereby achieving rapid and significant signal amplification. Therefore, combining the ion enrichment capabilities of ZIF-based materials with the catalytic amplification capabilities of Ag nanomaterials holds promise for constructing a detection system that combines target ion enrichment with colorimetric signal enhancement.

[0005] Furthermore, pH, as an important external regulatory parameter, not only affects Hg2+ and Cd 2+ The presence, complexation behavior, and interfacial interaction modes of Hg in the aqueous phase can also alter the surface state and colorimetric response characteristics of the sensing system, thus providing conditions for constructing multidimensional response information. 2+ and Cd 2+ Differences exist in their coordination preferences, hydrolysis behavior, and interactions with material interfaces, thus potentially leading to different response modes under varying pH conditions. Therefore, there is an urgent need for a method suitable for complex sample matrices that can achieve Hg... 2+ and Cd 2+ A detection method that distinguishes and identifies heavy metal ions while also having adsorption and removal functions is needed to meet the requirements for rapid detection and risk warning of heavy metal ions in aquatic products and related environmental samples. Summary of the Invention

[0006] For Hg in complex samples in the background technology 2+ and Cd 2+ The present invention addresses the challenges of achieving rapid, sensitive, and distinguishable detection while simultaneously addressing adsorption and removal issues. The aim of this invention is to design a Hg detection method based on a ZIF-AgNPs colorimetric sensor array. 2+ and Cd 2+ This method distinguishes between detection and adsorption removal methods, and achieves Hg removal by constructing a ZIF-AgNPs composite material. 2+ and Cd 2+ The adsorption enrichment and colorimetric detection of Hg were further studied; a colorimetric sensor array was constructed by setting sensing units under different pH conditions, and combined with linear discriminant analysis, to achieve the detection of Hg. 2+ and Cd 2+ Distinguishing and identifying Hg; simultaneously utilizing the composite material to distinguish Hg 2+ and Cd 2+ Adsorption and removal are carried out.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A colorimetric Hg sensor based on ZIF-AgNPs array 2+ and Cd 2+ To differentiate the detection methods, a colorimetric sensor array was constructed using five sensing units operating under different pH conditions. Each sensing unit included a ZIF-AgNPs composite material, TMB, and an acetate buffer solution at the corresponding pH. Different concentrations of Hg were added to each sensing unit. 2+ or Cd 2+ The standard solution was reacted at 25 °C for 30 min, and the absorbance response at 652 nm was recorded. Linear discriminant analysis was performed on the obtained multidimensional response data to achieve the determination of Hg. 2+ and Cd 2+The method for distinguishing and identifying is as follows:

[0009] S1: Construct a colorimetric sensor array consisting of sensing units under five different pH conditions. Each sensing unit includes a ZIF-AgNPs composite material, TMB, and an acetate buffer solution at the corresponding pH. The sensing unit includes:

[0010] Sensing Unit 1: ZIF-AgNPs composite material, TMB, and acetate buffer solution at pH 3.5;

[0011] Sensing unit 2: ZIF-AgNPs composite material, TMB, and acetate buffer solution at pH 4.0;

[0012] Sensing unit 3: ZIF-AgNPs composite material, TMB, and acetate buffer solution at pH 4.5;

[0013] Sensing unit 4: ZIF-AgNPs composite material, TMB, and acetate buffer solution at pH 5.0;

[0014] Sensing unit 5: ZIF-AgNPs composite material, TMB, and acetate buffer solution at pH 6.0;

[0015] S2: Add 100 μL of Hg at different concentrations to each sensing unit. 2+ Standard solution or 100 μL of Cd at different concentrations 2+ After reacting the standard solution at 25 °C for 30 min, the absorbance response value of each sensing unit at 652 nm was recorded, and the absorbance response value was used as the distinguishing factor for Hg. 2+ and Cd 2+ Characteristic variables;

[0016] S3: Perform 6 parallel experiments on the experiment in step S2 to obtain a sensor array response dataset containing 2 types of ions, 5 sensing units and 6 parallel experimental results, which will be used for subsequent discriminant analysis.

[0017] S4: The response values ​​of each sensing unit at 652 nm obtained in step S3 are used to form a feature vector, and linear discriminant analysis is performed on the feature vector to achieve Hg... 2+ and Cd 2+ Distinguishing and recognizing.

[0018] Furthermore, the ZIF-AgNPs composite material comprises a ZIF-L support and silver nanoparticles (AgNPs) loaded on the surface of the ZIF-L support. The ZIF-L support is formed by the reaction of 2-methylimidazolium and zinc nitrate hexahydrate. The composite material uses polyvinylpyrrolidone to stabilize the silver nanoparticles loaded on the ZIF-L support surface. The ZIF-AgNPs composite material exhibits oxidase-like activity, capable of catalyzing the color development of 3,3',5,5'-tetramethylbenzidine (TMB), and capable of adsorbing and removing mercury ions (Hg) from water through coordination. 2+ and cadmium ions Cd 2+ .

[0019] Further, 2-methylimidazole (2 mL) and zinc nitrate hexahydrate (Zn(NO3)2·6H2O) were first dissolved separately in deionized water (50 mL). After stirring until homogeneous, the two solutions were rapidly mixed and stirred for another 10 min. The mixture was then allowed to stand at room temperature for 24 h. The resulting precipitate was washed with deionized water and anhydrous ethanol, and then dried overnight in a vacuum oven at 60 °C. The dried solid was ground to obtain ZIF-L powder. The obtained ZIF-L was then dispersed in anhydrous ethanol at a mass-to-volume ratio of 1 g:1 mL. Polyvinylpyrrolidone (PVP) equivalent to 5 times the mass of ZIF-L was added as a stabilizer. Subsequently, 2.5 mL of 0.1 mol / L silver nitrate solution, 2.5 mL of 0.1 mol / L sodium citrate solution, and 2.5 mL of 0.1 mol / L glucose solution were added sequentially. The reaction was carried out under ultrasonic-assisted stirring for 15 h to load silver nanoparticles (AgNPs) onto the surface of ZIF-L. Finally, the obtained composite was collected by centrifugation, washed with pure water and ethanol, and then vacuum dried to obtain the ZIF-AgNPs composite material.

[0020] Furthermore, different concentrations of Hg were established. 2+ or Cd 2+ A linear calibration curve was obtained between the absorbance difference ΔA at 652 nm and the absorbance difference of the standard solution to be tested. Hg was calculated based on the absorbance difference of the standard solution to be tested. 2+ or Cd 2+ The concentration.

[0021] A colorimetric Hg sensor based on ZIF-AgNPs array 2+ and Cd 2+ Adsorption removal method, preparing Hg with different initial concentrations respectively. 2+ and Cd 2+ Standard solutions were prepared by adding a certain amount of ZIF-AgNPs composite material to each solution for adsorption; the Hg concentration in the supernatant was measured at different adsorption times. 2+ or Cd 2+The residual concentration was determined and the adsorption capacity was calculated. After adsorption equilibrium was reached, the equilibrium concentration was measured and the equilibrium adsorption capacity was calculated. Then, an adsorption kinetic model and an isothermal adsorption model were established. The method is as follows:

[0022] S1: Prepare Hg solutions with volumes of 30 mL and concentrations of 0.1, 1, 10, 50, 100, 200, 300, and 400 mg / L respectively. 2+ Standard solutions, and Cd solutions in volumes of 30 mL with concentrations of 0.1, 1, 10, 50, 100, 150, and 200 mg / L. 2+ Standard solution;

[0023] S2: To each Hg 2+ Standard solutions and Cd 2+ 30 mg of ZIF-AgNPs composite material was added to the standard solution to obtain the adsorption system;

[0024] S3: Adsorb each adsorption system at 25℃ for 5 min, 10 min, 30 min, 60 min, 180 min, 360 min and 720 min respectively;

[0025] S4: After adsorption is complete, perform solid-liquid separation on the adsorption system and determine the Hg in the supernatant. 2+ or Cd 2+ The residual concentration at different adsorption times was determined, and the corresponding adsorption amount was calculated.

[0026] S5: After adsorption equilibrium is reached, measure the Hg in the supernatant. 2+ or Cd 2+ The equilibrium concentration was determined, and the equilibrium adsorption capacity was calculated.

[0027] S6: Fit the adsorption kinetic model based on the adsorption amount at different adsorption times, and fit the isothermal adsorption model based on the equilibrium adsorption amount at different initial concentrations.

[0028] Furthermore, the adsorption removal was carried out at a pH of 5.

[0029] The above technical solution can achieve the following beneficial effects:

[0030] Utilizing the adsorption and enrichment capabilities of ZIF-L and the signal amplification capabilities of Ag nanozymes, Hg was achieved. 2+ and Cd 2+ The detection and adsorption removal of Hg were improved by constructing a colorimetric sensor array with multiple pH sensing units and combining it with linear discriminant analysis. 2+ and Cd 2+ With its superior ability to distinguish and identify Hg, the method of this invention has a low detection limit and a wide linear range, making it suitable for low concentrations of Hg.2+ and Cd 2+ The method of this invention is relatively simple to operate and can be used for the detection of Hg in food samples and environmental samples. 2+ and Cd 2+ Detection and analysis. Attached Figure Description

[0031] Figure 1 The construction of ZIF-AgNPs nanozymes and their application in Hg 2+ and Cd 2+ A schematic diagram of the colorimetric sensing mechanism for detection;

[0032] Figure 2 (A) Different Hg 2+ (a) UV-Vis absorption spectrum at a concentration of [specific concentration] (Illustration: colorimetric reaction photograph); (b) ELISA reader detection of Hg 2+ Linear calibration curves; (C) Different Cd 2+ (d) UV-Vis absorption spectra at various concentrations (illustrated: colorimetric reaction photograph); (d) ELISA reader detection of Cd 2+ The linear calibration curve.

[0033] Figure 3 Medium (A) ZIF-AgNPs, ZIF-AgNPs+Hg 2+ and ZIF-AgNPs+Cd 2+ The UV-Vis absorption spectrum of the system; (B) ZIF-AgNPs+Hg 2+ The absorption spectrum changes of the system under different pH conditions (3.6–6.0); (C)ZIF-AgNPs+Cd 2 + The absorption spectrum changes of the system under different pH conditions (3.6–6.0); (D) ZIF-AgNPs and ZIF-AgNPs+Hg under different pH conditions. 2+ and ZIF-AgNPs+Cd 2+ A statistical histogram of the absorption intensity of the system at approximately 650 nm.

[0034] Figure 4 For Hg 2+ with cd 2+ Discriminant analysis of LDA in different concentrations and mixed systems. (A–E)Hg 2+ with cd 2+ LDA plots at different concentrations: (A) 0.01 μmol / L, (B) 0.1 μmol / L, (C) 1 μmol / L, (D) 10 μmol / L, and (E) 50 μmol / L. (F) Hg 2+ with cd 2+LDA plots of binary mixtures under different molar ratios. (G) Confusion matrix of the binary mixture. (H) Hg 2+ Cd 2+ LDA diagrams of ternary mixed systems composed of interfering ions. (I) Confusion matrix of ternary mixed systems.

[0035] Figure 5 For Hg 2+ with cd 2+ LDA discriminant analysis and corresponding confusion matrices at different concentrations. (A)Hg 2+ LDA plots at different concentrations (0.01–100 μmol / L); (B) Hg 2+ The confusion matrix; (C)Cd 2+ LDA plots at different concentrations (0.01–50 μmol / L); (D)Cd 2+ The confusion matrix.

[0036] Figure 6 (A) Common metal cations and anions in Hg 2+ (B) Effects of common metal cations and anions on the absorbance response; 2+ A photograph of a colorimetric reaction.

[0037] Figure 7 For Hg 2+ and Cd 2+ The adsorption kinetics model was fitted. (A) Hg 2+ The pseudo-first-order kinetic fitting curve of the adsorption process; (B) Hg 2+ The pseudo-second-order kinetic fitting curve of the adsorption process; (C)Cd 2+ The pseudo-first-order kinetic fitting curve of the adsorption process; (D) Cd 2+ The pseudo-second-order kinetic fitting curve of the adsorption process.

[0038] Figure 8 For Hg 2+ and Cd 2+ The adsorption isotherm model was fitted. (A)Hg 2+ The Langmuir and Freundlich isotherm fitting curves for the adsorption process. (B)Cd 2+ Fitting curves of Langmuir and Freundlich isotherm models for the adsorption process. Detailed Implementation

[0039] The following is in conjunction with the appendix Figure 1-8 The present invention will be further illustrated by the following examples:

[0040] Zinc-based metal-organic framework-supported silver nanoparticles (ZIF-AgNPs) were prepared via in-situ reduction. These nanoparticles exhibited oxidase-like activity and could catalyze the color development of 3,3′,5,5′-tetramethylbenzidine (TMB). 2+ or Cd 2+ It can disrupt the ZIF structure and inhibit its activity, causing the system to decolorize. A multi-channel colorimetric array is constructed by utilizing the differential response of the two ions controlled by pH, and machine learning is combined to achieve classification, identification, and quantitative detection of the two ions. Simultaneously, this material can efficiently adsorb and remove heavy metal ions from water through coordination, integrating visual detection, intelligent identification, and adsorption. It can be widely used in environmental monitoring, food safety testing, and heavy metal pollution control.

[0041] like Figure 1 As shown, a ZIF-AgNPs composite material is provided, in which Ag nanoparticles are loaded onto the surface of a ZIF-L support. The ZIF-L support is formed by the reaction of 2-methylimidazole and zinc nitrate hexahydrate. The composite material is further supported on the surface of the ZIF-L support by silver nanoparticles stabilized by polyvinylpyrrolidone.

[0042] The preparation method is as follows: First, 2-methylimidazole (2-ML) and zinc nitrate hexahydrate (Zn(NO3)2·6H2O) were dissolved separately in deionized water (50 mL), with the amounts of 2-methylimidazole (2-ML) and Zn(NO3)2·6H2O being 20 mmol and 2.6 mmol, respectively. After stirring until homogeneous, the two solutions were rapidly mixed and stirred for another 10 min. The mixture was then allowed to stand at room temperature for 24 h. The resulting precipitate was washed with deionized water and anhydrous ethanol, and then dried overnight in a vacuum oven at 60 °C. The dried solid was ground to obtain ZIF-L powder. The obtained ZIF-L was then dispersed in anhydrous ethanol at a mass-to-volume ratio of 1 g:1 mL. Polyvinylpyrrolidone (PVP) equivalent to 5 times the mass of ZIF-L was added as a stabilizer. Subsequently, 2.5 mL of 0.1 mol / L silver nitrate solution, 2.5 mL of 0.1 mol / L sodium citrate solution, and 2.5 mL of 0.1 mol / L glucose solution were added sequentially. The reaction was carried out under ultrasonic-assisted stirring for 15 h to load silver nanoparticles (AgNPs) onto the surface of ZIF-L. Finally, the obtained composite was collected by centrifugation, washed with pure water and ethanol, and then vacuum dried to obtain the ZIF-AgNPs composite material.

[0043] mercury ions (Hg) 2+ ), cadmium ions (Cd) 2+ ) Detection and analysis results

[0044] Mercury ions (Hg) 2+Preparation of standard solution: Prepare mercury ion (Hg) solutions according to the national standard GB / T602-2002 "Preparation of standard solutions for the determination of impurities in chemical reagents". 2+ To prepare a standard solution of mercuric nitrate, weigh 0.162 g of mercuric nitrate, dissolve it in 10 mL of nitric acid solution, transfer the solution to a 1000 mL volumetric flask, and dilute to the mark with deionized water.

[0045] Cadmium ions (Cd) 2+ Preparation of standard solutions: Prepare cadmium ion (Cd) solutions according to the national standard GB / T602-2002 "Preparation of Standard Solutions for the Determination of Impurities in Chemical Reagents". 2+ A standard solution of cadmium chloride. Weigh 0.203 g of cadmium chloride, dissolve it in water, transfer it to a 1000 mL volumetric flask, and dilute to the mark.

[0046] Detection procedure: ZIF-AgNPs solution, acetate buffer, and chromogenic substrate 3,3',5,5'-tetramethylbenzidine are mixed at a volume ratio of 1:10:2, and then mercury ions (Hg) of different concentrations are added. 2+ ), cadmium ions (Cd) 2+ The standard solution was used to obtain the test sample solution; after reacting at 30℃ for 5 minutes, the absorbance value of the sample at 652nm was measured.

[0047] Constructing a linear model: Constructing different Hg 2+ The relationship between concentration and the intensity of the characteristic peak at 500-800 nm in the UV absorption spectrum is shown in the curve. Figure 2 As shown in Figure A. Linear fitting was performed, within the concentration range of 0.05–20 μmol / L, ΔA652 and c(Hg) 2+ The two molecules exhibit a good linear relationship, with the linear regression equation being Y = 0.05189c(Hg). 2+ )+0.18383, (R 2 =0.9963)( Figure 2 As shown in B), the limit of detection (LOD) calculated according to the 3σ criterion is 0.085 μmol / L. Figure 2 As shown in C, different Cd 2+ The relationship between concentration and the intensity of the characteristic peak at 500-800 nm in the UV absorption spectrum; through linear fitting, within the range of 0.01–5 μmol / L, ΔA652 and c(Cd) 2+ ) shows a good linear relationship, such as Figure 2 As shown in D, the linear regression equation is Y = 0.30582 c(Cd). 2+ )+0.22472, (R 2=0.9925). Based on the 3σ criterion, the calculated limit of detection (LOD) is 0.0195 μmol / L. Compared with other similar sensors, this sensor exhibits a wider linear range and a lower limit of detection (see Tables 1 and 2).

[0048] Table 1. ZIF-Ag NPs and other reported nanomaterials in Hg 2+ Comparison in detection

[0049]

[0050] Table 2. ZIF-Ag NPs and other reported nanomaterials in Cd 2+ Comparison in detection

[0051]

[0052] Machine learning for Hg 2+ Cd 2+ Classification effect

[0053] Five pH values ​​were selected as array dimensions to construct a multi-channel colorimetric sensor array, with each pH channel corresponding to an independent detection unit. The absorbance signals of each detection unit in the presence of the target ion were collected using a microplate reader to form a characteristic response "fingerprint". Figure 3 As shown). Due to Hg 2+ with cd 2+ Significant differences in absorbance responses were observed in different pH channels. Combining principal component analysis (PCA) pattern recognition methods, effective differentiation between two heavy metal ions with similar properties can be achieved in a multidimensional feature space, ultimately enabling the identification of Hg. 2+ and Cd 2+ Qualitative identification and preliminary quantitative analysis were performed. To evaluate the detection performance of this sensor array, its detection of different concentrations of Hg was investigated. 2+ and Cd 2+ An analysis was conducted. For example... Figure 4 As shown in A–E, Hg at concentrations of 0.01, 0.1, 1, 10, and 50 μmol / L... 2+ with cd 2+ The response signals all formed clearly separated clusters, indicating that the colorimetric sensor array can effectively distinguish between the two heavy metal ions over a wide concentration range and exhibits good recognition ability. To further evaluate the array's ability to distinguish between mixtures of multiple antibiotics, Hg was recorded while maintaining a total concentration of 10 μmol / L. 2+ and Cd 2+ Responses under different molar ratio combinations (7 groups of Hg with different proportions) 2+ Cd 2+Binary mixtures with molar ratios of 10:0, 9:1, 7:3, 5:5, 4:6, 2:8, and 0:10, with the total concentration of both maintained at 10 μmol / L. Figure 4 F shows Hg 2+ with cd 2+ The LDA discrimination results of binary mixtures formed under different molar ratios show that each mixture sample forms independent and clear clusters in the two-dimensional discrimination space, indicating that the array can effectively distinguish binary mixtures with different composition ratios. Figure 4 As shown in H, in Hg 2+ Cd 2+ And in the ternary mixed system composed of interfering ions (the designed Hg) 2+ Cd 2+ The ratios of other ionic mixtures were 10:0:50, 9:1:50, 7:3:50, 5:5:50, 4:6:50, 2:8:50, and 0:10:50, respectively. These other ionic mixtures consisted of Ca... 2+ Pb 2+ Mg 2+ Cr 3+ and K + The composition was the same, and the concentration of each ion was 10 μmol / L. Even with different ratios, samples still formed clearly separated clusters. Figure 4 H) indicates that the multi-channel colorimetric sensor array still possesses excellent discrimination ability and stable recognition performance in complex systems. Figure 4 G and Figure 4 I represents the corresponding confusion matrix. The predicted category of the sample closely matches the actual category, demonstrating the high recognition accuracy of the array.

[0054] Machine learning for different concentrations of Hg 2+ Cd 2+ Classification effect

[0055] Simultaneously, the quantitative analysis performance of the array was systematically evaluated. For example... Figure 5 The LDA plot and confusion matrix plot show that different concentrations of Hg 2+ Cd 2+ It exhibits a unique response pattern, further demonstrating that different concentrations of Hg 2+ Cd 2+ They can be effectively distinguished. For Hg 2+ ( Figure 5(A) Samples of different concentrations (0.01–100 μmol / L) formed multiple relatively independent clusters in the two-dimensional discriminant space. Low-concentration samples (0.01, 0.1, 0.5, and 1 μmol / L) were mainly distributed in the left-hand region of the figure, with some degree of proximity or partial overlap between them, while higher-concentration samples (20, 50, and 100 μmol / L) were clearly separated to the right, forming independent clusters. This indicates that as the concentration increases, the distribution differences of samples in the discriminant space gradually increase. Figure 5 B) is Hg 2+ The confusion matrix shows that the prediction results are almost entirely concentrated on the diagonal, indicating that the model is incompatible with different Hg concentrations. 2+ The classification accuracy is relatively high. Figure 5 C shows Cd 2+ The LDA distribution under different concentrations (0.01–50 μmol / L) shows that low-concentration samples (0.01, 0.1, 0.5, and 1 μmol / L) are also distributed in the left region of the figure and are somewhat close to each other. However, medium- and high-concentration samples (10, 20, and 50 μmol / L) are significantly shifted to the right and form independent clusters, especially the 50 μmol / L sample, which is significantly distant from other concentrations. Figure 5 D is Cd 2+ The confusion matrix also shows a high degree of consistency between the predicted and true categories, with diagonal elements dominating, indicating that the sensor array combined with the LDA model can achieve accurate prediction of Cd. 2+ Accurate classification of samples at different concentrations. Although some samples are close together or slightly overlap in the low concentration region, the separation of different samples in the discrimination space is significantly enhanced as the concentration increases. Simultaneously, the confusion matrix results show a high classification accuracy, indicating that this sensor array is effective in Hg... 2+ and Cd 2+ It has good distinguishing ability and potential quantitative analysis capability in terms of concentration identification.

[0056] Interference test

[0057] High selectivity for mercury ions (Hg) in actual samples 2+ ), cadmium ions (Cd) 2+ The detection of mercury ions (Hg) is crucial and is an important indicator of whether a method can be applied in actual sample testing. Because seafood still contains some metal ions after digestion, it may affect the detection of mercury ions (Hg). 2+ ), cadmium ions (Cd) 2+ The selectivity of ) has an impact, therefore, the selection of common metal ions and anions (metal cations Ni) in seafood is important. 2+ Na + K + Ca2+ Mg 2+ Mn 2+ Cr 3+ Zn 2+ Cu 2+ Pb 2+ Al 3+ and anion SO4 2- NO3 - PO4 3- The concentration of metal ions is mercury ions (Hg). 2+ ), cadmium ions (Cd) 2+ The concentration of mercury ions (Hg) is 5 times that of mercury ions, and the concentration of anions is also 5 times that of mercury ions (Hg). 2+ ), cadmium ions (Cd) 2+ Selectivity tests were conducted at 5 times the concentration of mercury ions (Hg). 2+ ), cadmium ions (Cd) 2+ Under optimal detection conditions, different metal ions were added to the same system, and the absorbance at 652 nm was measured using a microplate reader. Figure 6 It can be seen that, except for mercury ions (Hg) 2+ ), cadmium ions (Cd) 2+ Apart from mercury ions, other ions showed little response to this colorimetric detection method, indicating that the method is ineffective against mercury ions (Hg). 2+ The detection of ions has high specificity and is not affected by other ions.

[0058] Actual sample testing

[0059] To demonstrate the feasibility of this method in analytical applications, three seafood products—clams, shrimp, and crucian carp—were selected as representative samples to evaluate the analytical performance of the proposed method. The seafood samples required prior digestion. The specific steps were as follows: 0.5 g of each of the three seafood products were weighed and placed in separate Erlenmeyer flasks. 15 mL of HNO3 and 2.5 mL of H2SO4 were added sequentially, and the resulting mixed solutions were digested overnight at room temperature. Then, the mixture in the five Erlenmeyer flasks was heated to boiling until a large amount of white fumes were produced and the solution became clear. After cooling to room temperature, the pH of the resulting clear solution was adjusted to 5.0 with 1 mol / L NaOH solution, and then diluted to 100 mL with deionized water. Under optimal detection conditions, different concentrations of mercury ions (Hg) were added to the different seafood sample solutions. 2+ ), cadmium ions (Cd) 2+ Spiking recovery experiments were performed on the standard solutions, and the absorbance at 652 nm was measured using an ELISA reader. The spiked recovery rate was calculated based on the established standard curve. All experiments were repeated three times. As shown in Table 3, Hg... 2+ The spiked recoveries ranged from 90.6% to 101.1% for Cd. 2+The recoveries of the spiked samples ranged from 92.9% to 105.5%, with relative standard deviations (RSDs) ranging from 2.9% to 10.12%. These results demonstrate that the constructed ZIF-AgNPs nanozyme sensor exhibits good accuracy and repeatability in real samples, and is effective for Hg. 2+ and Cd 2+ The detection results are reliable and less affected by complex matrices, enabling effective quantitative analysis of target ions. Furthermore, the low relative standard deviation (RSD) indicates good stability and precision, further validating its application potential in practical food sample testing.

[0060] Table 3 Actual Sample Testing Table

[0061]

[0062] Adsorption kinetics model verification

[0063] The interaction between ZIF-AgNPs and Hg was investigated under optimal adsorbent dosage and pH conditions. 2+ Cd 2+ The intrinsic relationship between adsorption behaviors was investigated using Hg. 2+ Cd 2+ Adsorption kinetics and isothermal adsorption experiments were conducted. An initial concentration of 100 mg / L Hg was selected for this experiment. 2+ and 50 mg / L Cd 2+ To investigate the changes in adsorption kinetics over time. To elucidate the effect of ZIF-AgNPs on Hg... 2+ with cd 2+ The adsorption rate control process was investigated, and the experimental data were fitted using pseudo-first-order and pseudo-second-order kinetic models, respectively. The results are as follows: Figure 7 As shown in Table 4, for Hg 2+ ( Figure 7 A, Figure 7 B) The correlation coefficients of the pseudo-first-order kinetic model and the pseudo-second-order kinetic model were 0.4795 and 0.9999, respectively, indicating that Hg 2+ The adsorption process of Cd is more consistent with pseudo-second-order kinetics. 2+ ( Figure 7 C Figure 7 D) The correlation coefficients of the pseudo-first-order kinetic model and the pseudo-second-order kinetic model were 0.798 and 0.9952, respectively, indicating that Cd 2+ Adsorption on ZIF-AgNPs also primarily follows a pseudo-second-order kinetic model. Overall, Hg... 2+ with cd 2+The adsorption is more consistent with pseudo-second-order kinetics, which means that the adsorption rate is more likely to be dominated by chemisorption rather than simply controlled by physical diffusion. At the same time, the good fit of the pseudo-second-order model to the experimental data also shows that the adsorption system has a relatively stable rate law, providing a kinetic basis for subsequent intraparticle diffusion analysis and isothermal adsorption mechanism discussion.

[0064] Table 4. ZIF-AgNPs on Hg 2+ Cd 2+ Adsorption kinetics fitting parameter table

[0065]

[0066] Isothermal adsorption model validation

[0067] Isothermal adsorption line analysis can be used to study the adsorption capacity and adsorption type of adsorbent materials. To better evaluate the adsorption capacity of ZIF-AgNPs for Hg... 2+ Cd 2+ The adsorption capacity and type of ZIF-AgNPs were analyzed using two isothermal adsorption models, Langmuir and Freundlich, at different Hg levels. 2+ Cd 2+ The adsorption results at the initial concentration were fitted. For example... Figure 8 As shown, both ions exhibit a rapid increase in adsorption capacity Qe with increasing equilibrium concentration Ce, followed by a gradual plateau, indicating that adsorption sites on the material surface are gradually occupied and eventually reach saturation. Table 5 shows that the fitting results indicate that the Langmuir model provides a better description of the two ions: Hg... 2+ The correlation coefficient R of the Langmuir fit 2 =0.986, corresponding to the maximum monolayer adsorption capacity q max =462.13 mg / g, Langmuir constant K L =0.2353 L / mg; Cd 2+ The Langmuir fit is more ideal (R 2 =0.996), its q max =68.03 mg / g, K L =0.3647 L / mg. In contrast, the Freundlich model for Hg... 2+ It can still provide a certain fit (R) 2 =0.9643, K F =125.977(mg / g) (L / mg) 1 / n However, for Cd 2+ The fit is poor (R) 2 =0.7158, K F=40.569(mg / g)(L / mg) 1 / n This indicates that Cd²⁺ adsorption is less consistent with the heterogeneous multilayer adsorption assumption. Overall, the higher goodness of fit of Langmuir suggests that Hg... 2+ Cd 2+ The adsorption process on ZIF-AgNPs is mainly monolayer adsorption at a uniform locating site; meanwhile, Hg 2+ Significantly higher q max This indicates that the material is sensitive to Hg. 2+ It has better adsorption capacity.

[0068] Table 5. ZIF-AgNPs on Hg 2+ Cd 2+ Isothermal adsorption model fitting parameter table

[0069]

[0070] The above descriptions are all preferred embodiments of the present invention. For those skilled in the art, any modifications to the present invention in various equivalent forms without departing from the principle of the present invention shall fall within the protection scope of the appended claims.

[0071] To further illustrate the differences between this application and the technical solution of authorized patent CN120761369B, this application sets up a comparative experiment and compares them in terms of material system, detection object, detection purpose, signal mode, purpose of data processing, adsorption and removal function, and application focus. As shown in Table 6, CN120761369B uses COF-AgNPs as the material system and mainly targets Hg. 2+ Single target detection, combining absorbance and RGB information to achieve Hg 2+ With its expanded detection range and improved sensitivity, its main application is in the detection of Hg in food and environmental samples. 2+ Rapid detection. This application utilizes ZIF-AgNPs composite materials, targeting Hg... 2+ and Cd 2+ The system distinguishes between different ions by using multi-condition and multi-unit response data to form differentiated response patterns and achieves the identification of different ion categories through data processing. At the same time, it also takes into account the adsorption and removal function of target heavy metal ions. The application focuses on the synergy of detection and adsorption removal.

[0072] Table 6 Comparison of the technical solutions of this application and CN120761369B

[0073]

[0074] In summary, CN120761369B primarily addresses the issue of Hg. 2+The application addresses the issue of enhancing single-target detection performance, and this application primarily focuses on improving the performance of Hg detection within the same ZIF-AgNPs material system. 2+ and Cd 2+ The two methods differ substantially in terms of material system, detection object, data processing purpose, and functional boundaries.

Claims

1. A Hg-based colorimetric sensor array based on ZIF-AgNPs 2+ and Cd 2+ The distinguishing detection method is characterized by: A colorimetric sensor array for Hg was constructed by combining ZIF-AgNPs composite material with five pH-controlled sensing units. 2+ Cd 2+ The detection method is as follows: S1: Construct a colorimetric sensor array consisting of five sensing units under five different pH conditions. Each sensing unit includes a ZIF-AgNPs composite material, TMB, and an acetate buffer solution of the corresponding pH. The pH values ​​of the five sensing units are 3.5, 4.0, 4.5, 5.0, and 6.0, respectively. S2: Add Hg to each sensing unit respectively 2+ or Cd 2+ After the standard solution to be tested was reacted at 25 °C for 30 min, the absorbance response value of each sensing unit at 652 nm was recorded, and the absorbance response value was used as the distinguishing factor for Hg. 2+ and Cd 2+ Characteristic variables; S3: Perform 6 parallel experiments on the experiment in step S2 to obtain a sensor array response dataset containing 2 types of ions, 5 sensing units and 6 parallel experimental results, which will be used for subsequent discriminant analysis. S4: The response values ​​of each sensing unit at 652 nm obtained in step S3 are used to form a feature vector, and linear discriminant analysis is performed on the feature vector to distinguish and identify Hg. 2+ and Cd 2+ .

2. The Hg based on ZIF-AgNPs colorimetric sensor array according to claim 1 2+ and Cd 2+ The distinguishing detection method is characterized by: The ZIF-AgNPs composite material comprises a ZIF-L support and silver nanoparticles (AgNPs) loaded on the surface of the ZIF-L support. The ZIF-L support is formed by the reaction of 2-methylimidazolium and zinc nitrate hexahydrate. The composite material uses polyvinylpyrrolidone to stabilize the silver nanoparticles loaded on the ZIF-L support surface. The ZIF-AgNPs composite material exhibits oxidase-like activity, capable of catalyzing the color development of 3,3',5,5'-tetramethylbenzidine (TMB) and adsorbing and removing mercury ions (Hg) from water through coordination. 2+ and cadmium ions Cd 2+ .

3. The Hg based on ZIF-AgNPs colorimetric sensor array as described in claim 1 2+ and Cd 2+ The distinguishing detection method is characterized by: ZIF-L powder was dispersed in anhydrous ethanol at a mass-volume ratio of 1 g: 1 mL. Polyvinylpyrrolidone was added as a stabilizer, followed by silver nitrate solution, sodium citrate solution, and glucose solution. The mixture was reacted for 15 h under ultrasonic-assisted stirring to load silver nanoparticles onto the ZIF-L surface. After centrifugation, washing, and vacuum drying, ZIF-AgNPs composite material was obtained.

4. The Hg based on ZIF-AgNPs colorimetric sensor array according to claim 1 2+ and Cd 2+ The distinguishing detection method is characterized by: Establish different concentrations of Hg 2+ or Cd 2+ A linear calibration curve between the absorbance difference ΔA at 652 nm and the absorbance difference of the standard solution to be tested was obtained, and Hg was calculated based on the absorbance difference of the standard solution to be tested. 2+ or Cd 2+ The concentration.

5. A Hg based on ZIF-AgNPs colorimetric sensor array 2+ and Cd 2+ The adsorption removal method is characterized by: The method is as follows: S1: Prepare Hg solutions with volumes of 30 mL and concentrations of 0.1, 1, 10, 50, 100, 200, 300, and 400 mg / L respectively. 2+ Standard solutions, and Cd solutions in volumes of 30 mL with concentrations of 0.1, 1, 10, 50, 100, 150, and 200 mg / L. 2+ Standard solution; S2: To each Hg 2+ Standard solutions and Cd 2+ 30 mg of ZIF-AgNPs composite material was added to the standard solution to obtain the adsorption system; S3: Adsorb each adsorption system at 25℃ for 5 min, 10 min, 30 min, 60 min, 180 min, 360 min and 720 min respectively; S4: After adsorption is complete, perform solid-liquid separation on the adsorption system and determine the Hg in the supernatant. 2+ or Cd 2+ The residual concentration at different adsorption times was determined, and the corresponding adsorption amount was calculated. S5: After adsorption equilibrium is reached, measure the Hg in the supernatant. 2+ or Cd 2+ Determine the equilibrium concentration and calculate the equilibrium adsorption capacity; S6: Fit the adsorption kinetic model based on the adsorption amount at different adsorption times, and fit the isothermal adsorption model based on the equilibrium adsorption amount at different initial concentrations.

6. The Hg based on a ZIF-AgNPs colorimetric sensor array as described in claim 5 2+ and Cd 2+ The adsorption removal method is characterized by: Adsorption removal was carried out at a pH of 5.

7. The Hg based on a ZIF-AgNPs colorimetric sensor array as described in claim 5 2+ and Cd 2+ The adsorption removal method is characterized by: The Langmuir or Freundlich isothermal adsorption model was used for the isothermal adsorption model, and the pseudo-first-order kinetic model and pseudo-second-order kinetic model were used for the adsorption kinetic model.

Images