Ionic metal organic framework material for synchronously adsorbing and detecting lead ions in rice as well as preparation method and application of ionic metal organic framework material
By designing anionic metal-organic framework materials, high-capacity adsorption and high-sensitivity detection of Pb2+ were achieved, solving the problem of single function in existing technologies and realizing efficient removal and real-time monitoring of Pb2+ in rice.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- INST OF FOOD PROCESSING HEILONGJIANG ACAD OF AGRI SCI
- Filing Date
- 2026-01-23
- Publication Date
- 2026-05-19
AI Technical Summary
Existing materials and methods for treating and monitoring Pb2+ pollution often have limited functionality, insufficient adsorption capacity and detection sensitivity, and poor performance, especially in complex matrices such as rice, making it difficult to achieve efficient simultaneous removal and real-time monitoring.
An anionic metal-organic framework material was designed. Through a carefully designed anionic framework and counterions within the pores, it achieves high-capacity and high-selectivity adsorption of Pb2+. Furthermore, by utilizing its inherent fluorescence properties and the sensitive fluorescence quenching effect after binding with Pb2+, rapid and visual detection can be achieved.
It achieves efficient adsorption and highly sensitive detection of Pb2+, with an adsorption capacity of approximately 395 mg/g and a fluorescence detection limit as low as 10-4 M. It exhibits good selectivity and resistance to common ion interference, making it suitable for the simultaneous removal and real-time monitoring of Pb2+ in rice.
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Figure CN122060179A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of functional materials and environmental analysis technology, specifically relating to a transition metal-based metal-organic framework material with an anionic three-dimensional structure, and its application in rice Pb 2+ Applications in simultaneous adsorption and fluorescence detection. Background Technology
[0002] With the acceleration of industrialization and urbanization, the problem of heavy metal pollution in water and soil is becoming increasingly serious, especially lead ion (Pb). 2+ Due to its high toxicity, bioaccumulation, and persistent degradation, Pb poses a serious threat to the ecological environment and human health. As a major food crop, rice readily absorbs and accumulates Pb through irrigation water. 2+ It can then enter the human body through the food chain, and long-term intake can lead to damage to the nervous system, hematopoietic system and kidneys, especially causing irreversible effects on children's intellectual development.
[0003] Currently, regarding Pb 2+ The treatment and monitoring of [a specific type of pollutant] mainly rely on two types of technologies: adsorption removal materials and detection and analysis methods. Commonly used adsorption materials include activated carbon, ion exchange resins, and biochar. However, these materials generally have limited adsorption capacity, especially at low concentrations, and poor selectivity, making them susceptible to coexisting Ca2+. 2+ Mg 2+ Plasma interference is a significant challenge; most materials only possess adsorption capabilities, making real-time monitoring of pollutants impossible, leading to a lack of feedback and control in the processing. Regarding detection technologies, commonly used methods include instrumental analysis such as atomic absorption spectrometry (AAS) and inductively coupled plasma mass spectrometry (ICP-MS). While accurate, these methods suffer from drawbacks such as expensive equipment, complex sample pretreatment, the need for specialized personnel, and difficulty in achieving rapid on-site detection. In recent years, research has also reported detection methods based on fluorescent probes or enzyme-based biosensors; however, the former often exhibits poor resistance to interference in complex matrices, while the latter is limited by poor enzyme stability, stringent storage conditions, and susceptibility to environmental factors.
[0004] Metal-organic frameworks (MOFs) have shown great potential in adsorption and sensing due to their tunable structure, large specific surface area, and controllable pore environment. Among them, ionic metal-organic frameworks (iMOFs) have unique advantages in the recognition and capture of charged species due to the electrostatic field present in their framework. However, existing materials still have shortcomings in simultaneously possessing high adsorption capacity and high sensitivity detection performance, especially limiting their practical application in complex matrices (such as rice). Summary of the Invention
[0005] Addressing the limitations of existing technologies for processing and monitoring Pb2+ Traditional materials and methods for polluting lead ions often only adsorb or detect lead ions, resulting in limited functionality, poor performance in complex real-world matrices, and difficulty in balancing high adsorption capacity and high detection sensitivity. This invention aims to provide an ionic metal-organic framework material for the simultaneous adsorption and detection of lead ions in rice, along with its preparation method and applications.
[0006] The anionic metal-organic framework material of this invention achieves Pb retention through a carefully designed anionic framework and counterions within the pores. 2+ High capacity and high selectivity adsorption; at the same time, utilizing its inherent fluorescence properties and its affinity for Pb 2+ The sensitive fluorescence quenching effect after binding enables the control of Pb. 2+ Rapid and visual detection. This invention aims to provide a dual-functional material integrating efficient adsorption and sensitive detection, particularly suitable for the rapid and visual detection of Pb in rice. 2+ The simultaneous removal and real-time monitoring provide a novel and practical solution for agricultural product safety and environmental water body restoration.
[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:
[0008] A method for preparing an ionic metal-organic framework material for simultaneous adsorption and detection of lead ions in rice, the method comprising the following steps:
[0009] Step 1: Synthesis of ionic metal-organic framework materials: Mix divalent metal salt with 2-(3,5-dicarboxyphenyl)nicotinic acid (H3L), add to a mixed solvent of DMF and H2O, and stir magnetically until homogeneous;
[0010] Step 2: High-temperature reaction: Add nitric acid to the solution from Step 1 until the solution just becomes clear, put it into a 25 mL Teflon reaction vessel and heat it in a forced-air drying oven at 95~130℃ for 48~72 h, then slowly cool it down to room temperature;
[0011] Step 3: Washing and drying: Centrifuge the crystals obtained in Step 2 from the mother liquor, then wash them three times alternately with ethanol and DMF, and then dry them overnight in a vacuum drying oven at 55~65℃ to obtain an ionic metal-organic framework material with fluorescent properties.
[0012] Further, in step one, the metal salt is a zinc salt or a cadmium salt, preferably a nitrate; the molar ratio of the metal salt to H3L is 3~6:3, for example 1:1, 2:1, 4:3; the volume ratio of DMF to H2O is 1~5:1; and the ratio of solute (metal salt and H3L) to solvent (DMF and H2O) is 0.01~0.03mmol:0.5~4mL.
[0013] Furthermore, in step one, the mixture is stirred at 250-350 rpm / min for 25-35 minutes at 30-40°C.
[0014] Furthermore, in step two, the rate of slow cooling is 3~7℃ / min.
[0015] Furthermore, in step two, the volume ratio of the solution from step one to nitric acid is 2~5 mL: 5~150 μL.
[0016] An ionic metal-organic framework material prepared by the above preparation method for simultaneous adsorption and detection of lead ions in rice.
[0017] An application of the ionic metal-organic framework material prepared by the above preparation method for simultaneous adsorption and detection of lead ions in rice, wherein the application is:
[0018] Step 1: Prepare a Pb solution with a concentration of 30~1000 ppm using deionized water. 2+ Standard solution;
[0019] Step 2: Creating Pb 2+ A standard curve for the fluorescence quenching of titrated ionic metal-organic framework materials, which reflects the relationship between lead ion concentration and fluorescence intensity;
[0020] Step 3: Use the Pb from Step 1 2+ Rice was washed with a standard solution to obtain a rice washing solution with standard lead content;
[0021] Step 4: Stir the rice washing liquid with the ionic metal-organic framework material at room temperature for 2-4 hours to conduct an adsorption experiment. Detect the Pb content in the supernatant using ICP-MS. 2+ The content was determined and the adsorption amount was calculated. The fluorescence intensity of the rice washing liquid after adsorption was detected, and Pb was detected by fluorescence quenching degree according to the standard curve in step two. 2+ Calculate the content and spiked recovery rate.
[0022] Further, step two specifically involves: confirming the maximum excitation and emission wavelengths of the ionic metal-organic framework material; preparing 20 mL of a 0.2–1.0 mg / mL ionic metal-organic framework material suspension and sonicating it; testing the maximum emission wavelength and fluorescence intensity of the material in the aqueous solution; and then adding Pb dropwise. 2+ The standard solution was used, and the change in fluorescence intensity was measured until the fluorescence intensity no longer changed.
[0023] Furthermore, in step four, the ratio of rice washing liquid to ionic metal-organic framework material is 20 mL: 4~20 mg.
[0024] Furthermore, in step four, the formula for calculating the spiked recovery rate is: Spiked recovery rate = (Pb added) / (Pb added) 2+ Post-concentration - Original Pb in rice 2+ Concentration) / Added Pb 2+ Concentration × 100%; the pH range of the cleaning solution is 7~8, and it is obtained by adjusting with HCl or NaOH.
[0025] Compared with the prior art, the present invention has the following beneficial effects: The present invention is the first to achieve Pb on the same anionic material. 2+ Its dual functions of highly efficient adsorption removal and highly sensitive fluorescence detection simplify the processing and monitoring procedures. For Pb 2+ The maximum adsorption capacity reaches approximately 395 mg / g, which is superior to most reported MOFs and traditional adsorption materials. The fluorescence detection limit is as low as 10. -4 The order of M, and for Pb 2+ It exhibits good selectivity and strong resistance to common ion interference. The mechanism of this material is clear: adsorption and sensing originate from the same framework of ion exchange and coordination synergistic mechanism, and signal transduction is direct and reliable. The material is structurally stable in aqueous phases and complex matrices and can be reused. In real rice sample spiked experiments, it showed high recovery rates (91.0%~103.6%) and low relative standard deviations, verifying its practical application potential. This material framework not only has good selectivity for Pb... 2+ It is effective, and its fluorescence quenching effect also shows a sensitive response to electronically defective pollutants such as nitrobenzene, demonstrating its potential application value in monitoring a variety of pollutants. Attached Figure Description
[0026] Figure 1 (a) Schematic diagram of the pore environment of Zn-MOF in Example 1; (b) 3D network structure along the c-axis; (c) Topology diagram; (d) Schematic diagram of the 3D pore environment along the b-axis (excluding guest ions).
[0027] Figure 2 Here are (a) SEM images and (b) elemental mappings of Zn-MOF in Example 1;
[0028] Figure 3 The intrinsic fluorescence characteristics of Zn-MOF and its raw material H3L in Example 3 are shown in the diagram.
[0029] Figure 4 The relative fluorescence intensity and Pb in Example 3 2+ Concentration relationship graph. Illustration: With Pb 2+ Linear relationship graph of concentration;
[0030] Figure 5For Example 3, (a) the effect of adsorption time on adsorption performance; (b) Pb 2+ Adsorption isotherms on Zn-MOF; (c) Langmuir model fitting plot;
[0031] Figure 6 For example, in Example 3, the Pb content in rice and tap water was tested. 2+ The spiked experiment diagram;
[0032] Figure 7 For the effect of pH on Pb in Comparative Example 3 2+ The effect of adsorption performance is shown in the figure.
[0033] Figure 8 This is a diagram showing the intrinsic fluorescence characteristics of the Zn-MOF in Example 3;
[0034] Figure 9 This is a schematic diagram illustrating the simultaneous adsorption and detection of lead ions in rice using ionic metal-organic framework materials. Detailed Implementation
[0035] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Unless otherwise specified, the experimental methods described in the embodiments of the present invention are conventional methods, and the materials and reagents used in the following embodiments are commercially available unless otherwise specified.
[0036] Example 1:
[0037] A Zn-based ionic metal-organic framework material and its preparation method, comprising the following steps:
[0038] First, Zn(NO3)2·6H2O (5.9 mg, 0.02 mmol) was mixed with 2-(3,5-dicarboxyphenyl)nicotinic acid (H3L, 5.7 mg, 0.02 mmol) using DMF / H2O (2.5 mL v / v = 4 / 1) as solvent. The mixture was magnetically stirred at 300 rpm / min for 30 min at 35°C until homogeneous. Then, 50 μL of nitric acid was added dropwise, and the mixture was sonicated until the solution became clear and transparent. The solution was then transferred to a 25 mL Teflon reaction vessel and heated in a 120°C oven for 72 h, followed by slow cooling to room temperature at a rate of 5°C / min. The crystals were separated from the mother liquor by filtration, then washed three times alternately with ethanol and DMF, and finally dried overnight in a vacuum oven at 60°C to obtain the ionic metal-organic framework material {[(CH3)2NH2] + ]2[Zn2(L2)] 2− H2On (Zn-MOF).
[0039] like Figure 1 As shown, the crystal structure of Zn-MOF belongs to the orthorhombic crystal system, with space group 1. 21212. Its asymmetric unit contains two ligands and two Zn atoms. 2+ The ions and two free (CH3)2NH2 + Cations. For example... Figure 1 As shown in a, each Zn 2+ Ions reacted with four L atoms of different orientations. 3- Ligand coordination forms a three-dimensional network structure. Figure 1 b). This skeleton can be simplified to Topology, with point symbols [4] 2 ·6 3 ·8]( Figure 1 c). During the synthesis, DMF undergoes a decarboxylation reaction at high temperature to generate (CH3)2NH2. + Cations, which act as structural templates, guide the crystal along... The shaft forming dimensions are approximately 11.45 × 9.66 Å. 2 ion channels ( Figure 1 d). PLATON calculations show that the porosity of the synthesized Zn-MOF is only 5.2%; however, after removing the cationic template and solvent molecules, the porosity significantly increases to 30.8%. This result indicates that the anionic framework has excellent cation-carrying capacity, demonstrating its potential application in cationic heavy metal adsorption.
[0040] SEM and mapping were used to test the morphology of Zn-MOF before and after adsorption and the Pb content. 2+ The distribution of. For example... Figure 2 As shown in figure a, the morphology of this Zn-MOF was tested and found to be a square block shape. Furthermore, elemental mapping of the MOFs revealed the presence of Pb in the adsorbed structure. 2+ Metal ions ( Figure 2 b).
[0041] Example 2:
[0042] A Cd-based ionic metal-organic framework material and its preparation method, comprising the following steps:
[0043] First, Cd(NO3)2·4H2O (6.2 mg, 0.02 mmol) was mixed with 2-(3,5-dicarboxyphenyl)nicotinic acid (H3L, 11.4 mg, 0.01 mmol) using DMF / H2O (2.0 mL v / v = 1 / 1) as the solvent. The mixture was magnetically stirred at 300 rpm / min for 30 min at 35°C until homogeneous. Then, 10 μL of nitric acid was added dropwise, and the mixture was sonicated until the solution became clear and transparent. The solution was then transferred to a 25 mL Teflon reaction vessel and heated in a 105°C oven for 72 h, followed by slow cooling to room temperature at a rate of 5°C / min. The crystals were separated from the mother liquor by filtration, washed three times with DMF, and finally dried overnight in a vacuum oven at 60°C to obtain the ionic metal-organic framework material {[(CH3)2NH2] + [Cd(L)] - H2O n (Cd-MOF).
[0044] Example 3:
[0045] Performance verification of a transition metal-based ionic metal-organic framework material includes the following steps:
[0046] (1) Fluorescence properties
[0047] Taking the Zn-MOF obtained in Example 1 as an example, 10 mg of Zn-MOF sample was ground, and the wavelengths of the maximum excitation and emission peaks of Zn-MOF fluorescence were measured using a solid scaffold. Figure 3 As shown, uncoordinated H3L ligands exhibit weak photoluminescence at an excitation wavelength of 320 nm, with a maximum emission wavelength of 472 nm. A 20 mL suspension of 0.5 mg / mL Zn-MOF was prepared and sonicated. The maximum emission wavelength of this Zn-MOF at an excitation wavelength of 380 nm was measured to be 504 nm. 4 mM Pb was then gradually added to the suspension. 2+ An aqueous solution was used, and the change in fluorescence intensity was measured. The test results showed that with the addition of Pb... 2+ As the concentration of Pb increases, the fluorescence intensity of this Zn-MOF decreases significantly; when Pb... 2+ When the concentration increases to 1 mM, the fluorescence intensity is almost completely quenched. (Relative luminescence intensity) ) and Pb 2+ The relationship between concentration ([M]) and fitting is as follows: =0.0076×exp([M] / 0.1596)+1.2178( and Add Pb respectively 2+ The luminescence intensity before and after was calculated to obtain the Pb detection value of Zn-MOF. 2+ of The value is 1.28 × 10 3 M -1 ( Figure 4 ).
[0048] (2) Adsorption performance
[0049] 5 mg of Zn-MOF sample was added to 20 mL of Pb at different initial concentrations. 2+ In the solution, stir continuously for 3 hours. After adsorption equilibrium is reached, collect the supernatant and analyze it by ICP-MS. Figure 5 As shown in a~c, the Zn-MOF compound affects Pb 2+ The adsorption of ions reached saturation within 3 hours, with a removal rate of 91%. The effect of Zn-MOF on Pb was determined at pH 7. 2+ The adsorption isotherm of Zn-MOF was calculated. 2+ The maximum adsorption capacity was 395.33 mg / g, and the correlation coefficient (R0) of the Langmuir model was [missing value]. 2 The value is 0.9965, which proves that it is a monolayer adsorption.
[0050] Through analysis of Pb in rice and tap water 2+ Quantitative analysis was performed to evaluate the adsorption and detection of Pb by the Zn-MOF prepared in Example 1 in practical applications. 2+ The potential and feasibility of this study. Firstly, a certain amount of Pb is added to rice water washing solution or tap water. 2 + Concentrations of 500, 800, and 1000 mg / L were achieved. 10 mg of Zn-MOF was added to 20 mL of the test solution, mixed thoroughly, and stirred for 3 hours. The fluorescence intensity of Zn-MOF was then measured, and Pb was determined based on the standard curve. 2+ Concentration was determined and compared with ICP-MS data to determine recovery rate. Figure 6 As shown, the maximum adsorption capacity of Zn-MOF, determined by static adsorption, reached 395.33 mg / g, with recoveries ranging from 91.0% to 103.6% and a maximum relative standard deviation (RSD) of 3.35%. The synthesized Zn-MOF simultaneously adsorbed and detected Pb in real samples. 2+ Its reliability and practicality.
[0051] Comparative Example 1:
[0052] Ionic metal-organic framework materials were prepared using the method described in Example 1, with the only difference being the selection of cobalt nitrate as the metal ion source. The XRD results were consistent with those of Zn-MOF, but no fluorescence was observed.
[0053] Comparative Example 2:
[0054] Ionic metal-organic framework materials were prepared using the method described in Example 1, with the only difference being the selection of copper nitrate as the metal ion source. The peak positions in the X-ray powder diffraction pattern were inconsistent with those of Zn-MOF. Single-crystal X-ray diffraction and crystal analysis revealed that this MOF is a one-dimensional structure without pores, exhibiting no significant adsorption or fluorescence properties.
[0055] Comparative Example 3:
[0056] Zn-MOF was prepared using the method in Example 1 and used for Pb adsorption. 2+ The only difference is that the pH for adsorption is selected from 3 to 6 or 9, and the adsorption capacity is tested using ICP-MS. For example... Figure 7 As shown, within the acidic pH range, due to H3O + Ions and Pb 2+ Competitive adsorption occurs at the anion sites on the MOF surface, resulting in a decrease in adsorption efficiency. As pH increases, H3O... + The decrease in concentration enhanced the effect of Pb. 2+ The electrostatic interaction between the ions and the MOF anionic framework enhances the adsorption performance. Based on these results, pH 7 was selected as the optimal condition for subsequent adsorption experiments.
[0057] Comparative Example 4:
[0058] Zn-MOFs were prepared using the method described in Example 1, and their fluorescence properties were tested. The only difference was that the fluorescence properties of Zn-MOFs were tested. 2+ Ag + Fe 3+ K + Ca 2+ Ni 2+ And Al 3+ The fluorescence properties. For example... Figure 8 As shown, Zn-MOFs respond to the above ions to varying degrees, but only Pb responds. 2+ The fact that Zn-MOF can be almost completely quenched indicates that the ionic metal-organic framework material obtained by this method has Pb quenching properties. 2+ High selectivity and anti-interference ability.
[0059] In summary, by strictly following the steps of this invention, a method for simultaneously adsorbing and detecting Pb in rice can be prepared. 2+ Ionic metal-organic framework materials are readily obtained, while non-fluorescent MOFs materials, materials with low adsorption efficiency, or other products are easily obtained.
[0060] Table 1. Synthesis steps of MOF materials in Examples 1 & 2 and Comparative Examples 1-3, and simultaneous adsorption and detection of Pb. 2+ Effect
[0061]
[0062] Table 2. Examples 1 and current popular adsorbents for Pb 2+ Adsorption effect comparison
[0063]
[0064] Table 3 Crystal parameters of Zn-MOF in Example 1
[0065]
[0066] Table 4 Crystal parameters of Cd-MOF in Example 2
[0067]
Claims
1. A method for preparing an ionic metal-organic framework material for simultaneous adsorption and detection of lead ions in rice, characterized in that: The method includes the following steps: Step 1: Synthesis of ionic metal-organic framework materials: Mix divalent metal salt with 2-(3,5-dicarboxyphenyl)nicotinic acid (H3L), add to a mixed solvent of DMF and H2O, and stir magnetically until homogeneous; Step 2: High-temperature reaction: Add nitric acid to the solution from Step 1 until the solution just becomes clear, put it into a reaction vessel and heat it in a forced-air drying oven at 95~130℃ for 48~72 h, then slowly cool it down to room temperature; Step 3: Washing and drying: Centrifuge the crystals obtained in Step 2 from the mother liquor, then wash them alternately with ethanol and DMF, and then dry them overnight in a vacuum drying oven at 55~65℃ to obtain ionic metal-organic framework materials.
2. The method for preparing an ionic metal-organic framework material for simultaneous adsorption and detection of lead ions in rice according to claim 1, characterized in that: In step one, the metal salt is a zinc salt or a cadmium salt; the molar ratio of the metal salt to H3L is 3~6:3, the volume ratio of DMF to H2O is 1~5:1, and the ratio of solute (metal salt and H3L) to solvent (DMF and H2O) is 0.01~0.03mmol:0.5~4mL.
3. The method for preparing an ionic metal-organic framework material for simultaneous adsorption and detection of lead ions in rice according to claim 1, characterized in that: In step one, stir at 250-350 rpm / min at 30-40 ℃ for 25-35 minutes.
4. The method for preparing an ionic metal-organic framework material for simultaneous adsorption and detection of lead ions in rice according to claim 1, characterized in that: In step two, the cooling rate is 3~7℃ / min.
5. The method for preparing an ionic metal-organic framework material for simultaneous adsorption and detection of lead ions in rice according to claim 1, characterized in that: In step two, the volume ratio of the solution from step one to nitric acid is 2~5 mL: 5~150 μL.
6. An ionic metal-organic framework material for simultaneous adsorption and detection of lead ions in rice, prepared by the preparation method described in claims 1 to 5.
7. The application of an ionic metal-organic framework material prepared by the preparation method described in claims 1-5 for simultaneous adsorption and detection of lead ions in rice, characterized in that: The application is as follows: Step 1: Prepare Pb at a concentration of 30~1000 ppm 2+ Standard solution; Step 2: Creating Pb 2+ Standard curve for fluorescence quenching of ionic metal-organic framework materials; Step 3: Use the Pb from Step 1 2+ Rice was washed with a standard solution to obtain a rice washing solution with standard lead content; Step 4: The rice washing liquid and ionic metal-organic framework material were stirred at room temperature for 2-4 hours to conduct an adsorption experiment. The Pb content in the supernatant was detected by ICP-MS. 2+ The content was determined and the adsorption amount was calculated. The fluorescence intensity of the rice washing liquid after adsorption was detected, and Pb was detected by fluorescence quenching degree according to the standard curve in step two. 2+ Calculate the content and spiked recovery rate.
8. The application according to claim 7, characterized in that: Step two specifically involves: confirming the maximum excitation and emission wavelengths of the ionic metal-organic framework material; preparing 20 mL of a 0.2–1.0 mg / mL ionic metal-organic framework material suspension and sonicating it; testing the maximum emission wavelength and fluorescence intensity of the material in the aqueous solution; and then adding Pb dropwise. 2+ The standard solution was used, and the change in fluorescence intensity was measured until the fluorescence intensity no longer changed.
9. The application according to claim 7, characterized in that: In step four, the ratio of rice washing solution to ionic metal-organic framework material is 20 mL: 4~20 mg.
10. The application according to claim 7, characterized in that: In step four, the formula for calculating the spiked recovery rate is: Spiked recovery rate = (Added Pb) / (Added Pb) / (Added Pb) 2+ Post-concentration - Original Pb in rice 2+ Concentration) / Added Pb 2+ Concentration × 100%; the pH range of the cleaning solution is 7~8.