Method and system for detecting seawater lithium ion concentration based on multispectral fusion

Abstract

The application provides a seawater lithium ion concentration detection method and system based on multispectral fusion, and belongs to the technical field of water quality detection. The application collects water samples of original seawater, reverse osmosis concentrated brine, pretreatment liquid before lithium extraction and tail liquid after lithium extraction in the same water production cycle. Each type of water sample is divided into two, the second detection liquid adds a detection reagent that can cause color and fluorescence changes with lithium ions, and an alternating current signal is applied until the impedance value tends to be stable and then stopped. Ultraviolet, visible and fluorescence spectrum determination is performed on the two groups of detection liquids to obtain first and second spectra. The third spectrum is generated by the absorbance difference and fluorescence intensity difference of the two. By comparing the third spectra of the pretreatment liquid and the tail liquid, the absorption peak and fluorescence peak positions of lithium ions are determined. Combined with the pre-calibrated concentration and spectrum corresponding relationship, the lithium ion concentration of each node water sample is output. The application realizes accurate quantitative detection of lithium ion concentration at each processing stage of the whole seawater lithium extraction process.

Description

Technical Field

[0001] This application belongs to the field of water quality testing technology, and in particular relates to a method and system for detecting seawater lithium ion concentration based on multispectral fusion. Background Technology

[0002] Seawater contains over 230 billion tons of untapped lithium resources, far exceeding the total lithium resources on land. Extracting lithium from seawater holds great promise for resolving the growing conflict between the increasingly severe lithium shortage and the ever-increasing demand for lithium supply. With the large-scale development of the seawater desalination industry, introducing reverse osmosis brine into the combined process of concentrated seawater resource utilization and lithium extraction has become an important technological approach that balances freshwater supply and lithium recovery. Accurate detection of lithium ion concentration in the water at each treatment stage is a crucial prerequisite for achieving refined control of the lithium extraction process.

[0003] Existing methods for detecting lithium ion concentration in seawater and brine mainly include atomic emission spectrometry (AES) such as ICP-OES, spectrophotometry, and fluorescence probe methods. Spectrophotometry quantifies concentration by introducing a colorimetric reagent that complexes with lithium ions and observing changes in absorbance. Fluorescence probe methods utilize fluorescent ligands that selectively respond to lithium ions, detecting concentration through changes in fluorescence intensity. Additionally, some studies have combined ultraviolet absorption spectroscopy with chemometric models for predicting lithium concentration in water bodies with multiple coexisting ions. However, most of these methods are designed for water samples under specific matrix conditions or at a single detection point, and do not fully consider the significant differences in the matrix composition of water samples at different stages of the lithium extraction process.

[0004] Because the lithium-ion concentration in seawater is extremely low and contains a large number of interfering ions, and the ion composition, conductivity, and background interference vary significantly across different treatment stages, existing detection methods struggle to accurately distinguish lithium-ion signals from matrix interference signals when applied across multiple nodes, resulting in insufficient reliability of the detection results. Furthermore, existing methods lack an effective mechanism for determining the completion status of reagent reactions, making them susceptible to errors due to incomplete reaction equilibrium. They also lack the ability to dynamically confirm the position of lithium-ion characteristic peaks within the same water production cycle, making it difficult to address peak shifts caused by water quality fluctuations. Therefore, existing technologies suffer from poor accuracy and reliability in lithium-ion concentration detection under complex water quality conditions at multiple nodes in seawater lithium extraction co-production processes. Summary of the Invention

[0005] The purpose of this application is to provide a method and system for detecting lithium-ion concentration in seawater based on multispectral fusion, so as to solve the problems of poor accuracy and insufficient reliability of lithium-ion concentration detection in the existing technology under the complex water quality conditions of multiple nodes in the seawater lithium extraction and co-production process.

[0006] To address the aforementioned technical problems, in a first aspect, this application provides a method for detecting seawater lithium-ion concentration based on multispectral fusion, comprising: Water samples were collected from the original seawater, reverse osmosis brine, pretreated liquid before lithium extraction, and tailings liquid after lithium extraction within the same water production cycle. Each water sample is divided into a first detection solution and a second detection solution. A detection reagent that reacts with lithium ions to produce color and fluorescence changes is added to the second detection solution. An AC signal is applied to the second detection solution of each water sample until the impedance value changes measured multiple times are within the preset allowable range. For each water sample, the first and second test solutions were subjected to ultraviolet absorption spectroscopy, visible absorption spectroscopy, and fluorescence spectroscopy to obtain the first and second spectra of each water sample. Based on the differences in absorbance and fluorescence intensity between the first and second spectra of the same water sample, a third spectrum is generated for each water sample. Based on the third spectrum of the pretreated liquid and the third spectrum of the tail liquid, the absorption peak and fluorescence peak corresponding to lithium ions within the water production cycle are determined. Based on the absorption peak and fluorescence peak, the corresponding changes in absorbance and fluorescence intensity are determined from the third spectrum of each water sample. Based on the changes in absorbance and fluorescence intensity, the lithium ion concentration of each water sample is determined using the pre-calibrated correspondence between the lithium ion concentration and the changes in absorbance and fluorescence intensity.

[0007] Optionally, ultraviolet absorption spectroscopy, visible absorption spectroscopy, and fluorescence spectroscopy are performed on the first and second test solutions of each water sample to obtain the first and second spectra of each water sample, including: When measuring the first and second detection solutions of each water sample, the first and second detection solutions are irradiated by an ultraviolet light source, a visible light source, and a fluorescent excitation light source, respectively, to obtain a first light intensity record corresponding to the first detection solution and a second light intensity record corresponding to the second detection solution. The on and off frequencies of the ultraviolet light source, the visible light source, and the fluorescent excitation light source are different from each other. The first and second light intensity records include the light intensity values ​​that change with the measurement time at each measurement wavelength. According to the on / off frequency, the corresponding ultraviolet transmitted light intensity value, visible transmitted light intensity value, and fluorescence emitted light intensity value are separated from the first light intensity record and the second light intensity record, respectively. The ultraviolet absorbance is obtained based on the ultraviolet transmitted light intensity value and the corresponding ultraviolet incident light intensity value. The visible absorbance is obtained based on the visible transmitted light intensity value and the corresponding visible incident light intensity value. The fluorescence intensity is taken as the fluorescence intensity value. The ultraviolet absorbance, visible absorbance and fluorescence intensity corresponding to the first light intensity are recorded as the first spectrum. The ultraviolet absorbance, visible absorbance and fluorescence intensity corresponding to the second light intensity are recorded as the second spectrum.

[0008] Optionally, an ultraviolet light source, a visible light source, and a fluorescence excitation light source are used to irradiate the first detection liquid and the second detection liquid, respectively, to obtain a first light intensity record corresponding to the first detection liquid and a second light intensity record corresponding to the second detection liquid, including: When measuring the first test solution, the ultraviolet light source, visible light source and fluorescent excitation light source are irradiated with the first test solution at their respective on and off frequencies during the same measurement time period. The photodetector receives the ultraviolet transmitted light formed by the first detection liquid under ultraviolet light source irradiation, the visible transmitted light formed under visible light source irradiation, and the fluorescent emitted light formed under fluorescent excitation light source irradiation, and records the corresponding light intensity values ​​according to the measurement time and measurement wavelength to form the first light intensity record. When measuring the second detection solution, the ultraviolet light source, visible light source, and fluorescent excitation light source are irradiated with the second detection solution at their respective on / off frequencies within the same measurement time period. The photodetector receives the ultraviolet transmitted light formed by the second detection liquid under ultraviolet light source irradiation, the visible transmitted light formed under visible light source irradiation, and the fluorescent emitted light formed under fluorescent excitation light source irradiation, and records the corresponding light intensity values ​​according to the measurement time and measurement wavelength to form a second light intensity record.

[0009] Optionally, an alternating current signal is applied to the second detection solution of each water sample until the impedance value changes from multiple measurements are within a preset allowable range, including: Impedance measurements were performed on the second detection liquid of each water sample after an AC signal was applied at preset time intervals to obtain multiple impedance values ​​within a continuous measurement time. Calculate the absolute value of the difference between the impedance values ​​corresponding to two adjacent measurement times to obtain the change in impedance between adjacent measurements; When the consecutive preset number of adjacent impedance changes are all within the preset allowable range, stop applying the AC signal to the second detection liquid.

[0010] Optionally, based on the differences in absorbance and fluorescence intensity between the first and second spectra of the same water sample, a third spectrum is generated for each water sample, including: At each measurement wavelength, the difference in absorbance and the difference in fluorescence intensity between the second and first spectra of the same water sample are calculated to obtain the absorbance difference and fluorescence intensity difference. The absorbance difference and fluorescence intensity difference corresponding to each measurement wavelength are arranged in order from shortest wavelength to longest wavelength to generate the third spectrum of each water sample.

[0011] Optionally, based on the third spectrum of the pretreated water sample and the third spectrum of the tailings water sample, the absorption peak and fluorescence peak corresponding to lithium ions during the water production cycle are determined, including: The wavelength in the third spectrum of the pretreated water sample with an absorbance difference greater than the absorbance difference between the previous and subsequent measurement wavelengths is determined as the candidate absorption wavelength. The fluorescence intensity difference in the third spectrum of the pretreated water sample that is greater than the fluorescence intensity difference between the previous and subsequent measurement wavelengths is determined as the candidate fluorescence wavelength. Peaks formed at candidate absorption wavelengths with absorbance differences greater than those at the same measurement wavelength in the third spectrum of the tail liquid were identified as the absorption peaks corresponding to lithium ions. Peaks formed at candidate fluorescence wavelengths with fluorescence intensity differences greater than those at the same measurement wavelength in the third spectrum of the tailings water sample were identified as the fluorescence peaks corresponding to lithium ions.

[0012] Optionally, before determining the lithium ion concentration of each water sample based on the changes in absorbance and fluorescence intensity using a pre-calibrated correspondence between the lithium ion concentration and the changes in absorbance and fluorescence intensity, the method further includes: Salt solutions with the same conductivity were prepared for the raw seawater, reverse osmosis concentrated brine, pretreatment liquid before lithium extraction, and tailings liquid after lithium extraction. Each salt solution was divided into multiple portions and then different preset amounts of lithium ion solutions of known concentration were added to each portion to obtain multiple lithium standard solutions with different lithium ion concentrations. Calculate the changes in absorbance and fluorescence intensity for each lithium standard solution; Based on the changes in lithium ion concentration, absorbance, and fluorescence intensity of each lithium standard solution, a corresponding relationship is established with the corresponding water sample.

[0013] Optionally, the water samples of raw seawater, reverse osmosis brine, pre-treated liquid before lithium extraction, and tailings after lithium extraction are all taken from the same batch of seawater entering the reverse osmosis unit at different treatment stages. The raw seawater sample is collected before the seawater enters the reverse osmosis unit. The reverse osmosis brine sample is collected after the raw seawater has been concentrated in the reverse osmosis unit. The pretreatment solution sample is collected after the reverse osmosis brine has been pretreated and before it enters the lithium extraction unit. The tailings sample is collected during the normal effluent stage after the pretreatment solution has been treated in the lithium extraction unit. The tailings sample does not include eluent, regenerated solution, or rinsing solution.

[0014] Secondly, this application provides a seawater lithium-ion concentration detection system based on multispectral fusion, comprising: The data acquisition module is used to collect water samples of raw seawater, reverse osmosis brine, pretreatment solution before lithium extraction, and tailings solution after lithium extraction within the same water production cycle. The dividing module is used to divide each water sample into a first detection solution and a second detection solution, and to add a detection reagent to the second detection solution that reacts with lithium ions to produce color and fluorescence changes. An AC signal is applied to the second detection solution of each water sample until the impedance value changes measured multiple times are within the preset allowable range and then the process stops. The measurement module is used to perform ultraviolet absorption spectroscopy, visible absorption spectroscopy and fluorescence spectroscopy on the first and second test solutions of each water sample to obtain the first and second spectra of each water sample. The generation module is used to generate a third spectrum for each water sample based on the difference in absorbance and fluorescence intensity between the first and second spectra of the same water sample. Based on the third spectrum of the pretreated water sample and the third spectrum of the tailings water sample, the absorption peak and fluorescence peak corresponding to lithium ions in the water production cycle are determined. The generation module is also used to determine the corresponding changes in absorbance and fluorescence intensity from the third spectrum of each water sample according to the absorption peak and fluorescence peak. Based on the changes in absorbance and fluorescence intensity, the lithium ion concentration of each water sample is determined by using the pre-calibrated correspondence between the lithium ion concentration and the changes in absorbance and fluorescence intensity.

[0015] Thirdly, this application provides an electronic device, comprising: Memory, used to store computer programs; A processor is configured to execute the computer program to implement the steps of the seawater lithium-ion concentration detection method based on multispectral fusion as described in the first aspect above.

[0016] Fourthly, this application provides a computer-readable storage medium storing a computer program that, when executed by a processor, can implement the steps of the seawater lithium-ion concentration detection method based on multispectral fusion as described in the first aspect above.

[0017] The seawater lithium-ion concentration detection method based on multispectral fusion provided in this application addresses the problem of complex water sample matrices and easy interference of lithium-ion signals in the seawater lithium extraction co-production process. This application ensures the consistency of the source of the detected objects in the time dimension by simultaneously collecting four types of water samples—raw seawater, reverse osmosis concentrated brine, pretreatment liquid, and tailings liquid—within the same water production cycle, thereby eliminating systematic errors introduced by batch fluctuations in water quality.

[0018] In each water sample, the first detection solution without reagents and the second detection solution with reagents were subjected to UV, Visible, and Fluorescence spectral measurements, respectively. A third spectrum, reflecting only the contribution of the reagent-lithium ion reaction, was generated through difference calculations, effectively eliminating interference from the water sample background matrix. This application utilizes the comparison of the third spectra of the pre-treatment solution before lithium extraction and the tailings solution after lithium extraction within the same production cycle to dynamically determine the true absorption and fluorescence peak positions of lithium ions within that cycle, avoiding the characteristic peak shift problem caused by water quality fluctuations. Furthermore, concentration quantification is achieved by combining the standard curves matching the conductivity of water samples at each node. In summary, the method proposed in this application significantly improves the accuracy and reliability of lithium ion concentration detection under complex water quality conditions at multiple nodes in the seawater lithium extraction co-production process.

[0019] Furthermore, this application simultaneously irradiates the same detection liquid with ultraviolet light, visible light, and fluorescence excitation light at different on / off frequencies within the same measurement time period. The light intensity record collected by the photodetector simultaneously superimposes the response signals of the three types of light sources, thus acquiring all three types of spectral information while completing one measurement.

[0020] Subsequently, the mixed light intensity records were separated and demodulated according to the on / off frequencies of each light source, and ultraviolet transmission, visible transmission, and fluorescence emission signals were extracted separately. These signals were then converted into absorbance and fluorescence intensity based on their respective incident light intensity reference values, thus constructing complete first and second spectra. This mechanism achieves simultaneous acquisition and efficient separation of multiple spectral information without increasing measurement time, avoiding the impact of liquid state changes caused by time-sharing measurements on spectral consistency, and further improving the signal reliability and measurement efficiency of multispectral fusion detection in complex water quality scenarios. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 A schematic flowchart illustrating a method for detecting lithium-ion concentration in seawater based on multispectral fusion, provided in an embodiment of this application; Figure 2 A schematic diagram of a controlled impedance measurement process provided in an embodiment of this application; Figure 3 A schematic diagram of a process for generating a first spectrum and a second spectrum is provided for an embodiment of this application; Figure 4This is a schematic diagram of a seawater lithium-ion concentration detection system based on multispectral fusion, provided as an embodiment of this application. Detailed Implementation

[0023] In the seawater lithium extraction co-production process, the water bodies at different treatment nodes—raw seawater, reverse osmosis brine, pretreatment liquid, and lithium extraction tailings—exhibit significant differences in ionic composition, conductivity, and background interference. The lithium-ion concentration is extremely low and overlaps with a large number of coexisting ions, making signal identification extremely difficult. Existing detection methods, such as spectrophotometry and fluorescence probe methods, are mostly established for single water matrices and struggle to effectively distinguish lithium-ion characteristic signals from complex background interference components when applied across multiple nodes, resulting in insufficient detection reliability.

[0024] Meanwhile, existing methods generally lack means to determine the completion status of the reaction between the detection reagent and the target ion. Spectral acquisition is often carried out before the reaction reaches equilibrium, further reducing the accuracy of the results. In addition, periodic fluctuations in water quality can cause shifts in the position of lithium ion characteristic peaks. Existing methods lack the ability to dynamically calibrate peak positions within the same water production cycle, making them unable to adapt to dynamic changes in water quality in actual production environments. This results in technical problems of poor accuracy and insufficient reliability in lithium ion concentration detection under the complex water quality conditions of multiple nodes in the seawater lithium extraction co-production process.

[0025] To address the aforementioned issues, this application proposes a multispectral fusion-based method for detecting lithium-ion concentration in seawater. The core idea is to simultaneously collect water samples from each treatment node within the same water production cycle, dividing each sample in half. By applying an AC signal and continuously monitoring impedance changes, spectral measurements are performed only after confirming that the reaction between the detection reagent and lithium ions has reached equilibrium, thus eliminating errors introduced by incomplete reactions. Ultraviolet, visible, and fluorescence spectra are measured for both the stock solution and the reagent-added solution, and a difference spectrum reflecting only the lithium-ion response contribution is constructed through difference calculations, effectively isolating background interference from complex water quality matrices.

[0026] Further utilizing the lateral comparison of the spectral differences between water samples from two different nodes before and after lithium extraction within the same production cycle, the true characteristic peak position of lithium ions within the current cycle is dynamically identified, adaptively addressing peak position drift caused by water quality fluctuations. Finally, by combining the calibration relationship of matrix matching for water samples at each node, accurate quantitative output of concentration is achieved. This method organically combines reaction state monitoring, multispectral difference fusion, and dynamic peak position identification, working synergistically from three dimensions: reagent reaction reliability, signal anti-interference, and peak position adaptability. It effectively solves the technical problems of poor accuracy and insufficient reliability of lithium ion concentration detection in complex water quality scenarios with multiple nodes in seawater lithium extraction and co-production.

[0027] To enable those skilled in the art to better understand the present application, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are merely some embodiments of the present application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0028] To address the problems of existing technologies, this application provides a method, apparatus, device, computer storage medium, and computer program product for detecting seawater lithium-ion concentration based on multispectral fusion. The method for detecting seawater lithium-ion concentration based on multispectral fusion provided in this application will be described below.

[0029] Figure 1 A schematic flowchart of a seawater lithium-ion concentration detection method based on multispectral fusion according to an embodiment of this application is shown. Figure 1 As shown, the method includes: S101. Collect water samples of raw seawater, reverse osmosis brine, pretreatment solution before lithium extraction, and tailings solution after lithium extraction within the same water production cycle.

[0030] Optionally, in step S101, the water samples of the original seawater, reverse osmosis concentrated brine, pre-treated liquid before lithium extraction, and tailings after lithium extraction are all taken from the same batch of seawater entering the reverse osmosis unit and formed at different treatment stages.

[0031] The raw seawater sample is collected before the seawater enters the reverse osmosis unit. The reverse osmosis brine sample is collected after the raw seawater has been concentrated in the reverse osmosis unit. The pretreatment solution sample is collected after the reverse osmosis brine has been pretreated and before it enters the lithium extraction unit. The tailings sample is collected during the normal effluent stage after the pretreatment solution has been treated in the lithium extraction unit. The tailings sample does not include eluent, regenerated solution, or rinsing solution.

[0032] The water production cycle refers to the complete treatment process of a batch of seawater, from its entry into the reverse osmosis unit, through concentration, pretreatment, lithium extraction, and other stages, ultimately outputting the tailings. Raw seawater refers to natural seawater that has not yet entered the reverse osmosis unit, and its lithium-ion concentration represents the baseline level for this batch of incoming water. Reverse osmosis concentrated brine refers to the high-salinity brine formed after the raw seawater has been concentrated in the reverse osmosis unit, and its lithium-ion concentration is higher than that of the raw seawater.

[0033] The pretreatment solution before lithium extraction refers to the water body that enters the lithium extraction unit after being treated by the reverse osmosis brine through a pretreatment process. The pretreatment process may include operations such as impurity removal, pH adjustment, and filtration. The matrix composition of the pretreatment solution is relatively stable and the lithium ion concentration is at the highest level before the lithium extraction operation.

[0034] The tail liquid after lithium extraction refers to the water produced during the normal effluent stage after the pretreatment liquid before lithium extraction is treated by the lithium extraction unit. It can be the normal effluent after the lithium extraction unit has completed adsorption and entered the breakthrough or saturation stage. The tail liquid after lithium extraction does not include eluent, regeneration liquid and rinsing liquid, which means that the non-representative liquid discharged by the lithium extraction unit during the desorption, regeneration and rinsing operation stages is excluded to ensure that the collected water sample can truly reflect the lithium ion removal effect during the lithium extraction process.

[0035] During a water production cycle, water samples are collected sequentially at four fixed sampling points. All four types of water samples are taken from the same batch of seawater entering the reverse osmosis unit and formed into water bodies at different treatment stages, thereby ensuring the consistency of the source of each water sample and making the comparison of lithium ion concentration at each subsequent node traceable.

[0036] First, before the seawater enters the reverse osmosis unit, a raw seawater sample is collected at the inlet pipe to obtain background concentration data of lithium ions in this batch of natural seawater. Next, the first hydraulic retention time is calculated based on the pipeline volume and real-time flow rate between the raw seawater and the reverse osmosis concentrate outlet. After the first hydraulic retention time is delayed, a reverse osmosis brine sample is collected at the concentrate outlet to obtain data on the increased lithium ion concentration in the same batch of water after concentration treatment.

[0037] Then, the second hydraulic residence time is calculated based on the flow path and flow rate of the reverse osmosis brine through the pretreatment process. After the second hydraulic residence time is delayed and before entering the lithium extraction unit, a pretreatment solution sample is collected at the pretreatment outlet to obtain the initial lithium ion concentration data for the same batch before the lithium extraction operation. Finally, the third hydraulic residence time is calculated based on the hydraulic displacement reaction time of the lithium extraction unit. After the third hydraulic residence time is delayed and after the lithium extraction unit enters the normal effluent stage, a tailings sample is collected at the lithium extraction unit outlet to obtain the residual lithium ion concentration data for the same batch after the lithium extraction operation. The sampling time is strictly limited to the normal effluent stage to rule out concentration anomalies caused by the mixing of eluent, regenerated solution, and rinsing solution.

[0038] S102. Divide each water sample into a first detection solution and a second detection solution, and add a detection reagent that reacts with lithium ions to produce color and fluorescence changes. Apply an AC signal to the second detection solution of each water sample until the impedance value changes measured multiple times are within the preset allowable range, and then stop.

[0039] The first detection solution refers to a portion of the liquid separated from each water sample without the addition of any detection reagents, used to determine the spectral characteristics of the original background of the water sample. The second detection solution refers to another portion of the liquid separated from each water sample with the addition of detection reagents, used to determine the spectral characteristics of lithium ions in the water sample after reaction with the reagents. The detection reagents are chemical reagents capable of selectively reacting with lithium ions and producing color and fluorescence changes. They may include crown ether lithium ion complexing agents or lithium ion selective ligands containing chromophores and fluorophores. Specifically, a composite ligand reagent prepared by mixing 1-(2-pyridinium azo)-2-naphthol (PAN) and 12-crown-4 ether in a molar ratio of 1:1 can be used. When the detection reagent complexes with lithium ions, it will produce an absorption peak change in the visible light band and a fluorescence emission intensity change at a specific excitation wavelength.

[0040] The alternating current signal refers to the alternating electric field signal applied to the second detection liquid. It can be a sinusoidal or square wave signal with a frequency in the range of 100Hz to 10kHz, and its function is to accelerate the diffusion and mixing process of the detection reagent and lithium ions and promote the complexation reaction to reach an equilibrium state. The impedance value refers to the electrical impedance characteristics exhibited by the second detection liquid under the action of the alternating current signal, and it can be calculated by measuring the amplitude and phase difference of the current and voltage. The magnitude of the impedance value reflects the ion concentration and the progress of the complexation reaction in the liquid, and the impedance value tends to stabilize when the complexation reaction reaches equilibrium.

[0041] The preset allowable range refers to the permissible threshold for the difference between two adjacent impedance measurements. It can be that the absolute value of the impedance change is less than 0.5% to 2% of the initial impedance value, and the reaction is considered to have reached equilibrium when the impedance change measured in multiple consecutive measurements is within this range. The initial impedance value is defined as the impedance value first collected at the moment when an AC signal is applied to the second detection liquid.

[0042] For the four types of water samples collected in step S101, the preparation of detection solutions and the determination of reaction equilibrium are performed sequentially to ensure that the reaction between the detection reagent and lithium ions has reached a stable state during subsequent spectral measurements. First, each water sample is evenly divided into two parts. One part is used as the first detection solution and remains unchanged without adding any reagents. The other part is used as the second detection solution to be added with the detection reagent. The volume ratio of the two liquids can be 1:1, and the volume of a single part can be 25 mL to 100 mL, thus obtaining a total of eight detection solutions, namely the first and second detection solutions corresponding to the original seawater, reverse osmosis concentrated brine, pretreatment solution, and tailings.

[0043] Next, a predetermined amount of detection reagent is added to each second detection solution. The amount of detection reagent added is determined according to the expected lithium ion concentration range in the water sample. This ensures the molar ratio of reagent to lithium ions is maintained between 5:1 and 20:1, guaranteeing reagent excess and sufficient complexation with lithium ions. After adding the reagent, gently shake to initially disperse it in the liquid. Then, each second detection solution is placed in a reaction vessel equipped with electrodes. An alternating current (AC) signal is applied to the liquid through the electrodes. The frequency of the AC signal can be 1 kHz, and the amplitude can be between 1 V and 5 V. During the application of the AC signal, impedance measurements are performed on the liquid at preset time intervals, which can be between 30 and 120 seconds. The AC signal is stopped when the adjacent impedance changes measured consecutively for a preset number of times are all within a preset allowable range. The preset number of times can be between 3 and 5.

[0044] This embodiment, by designing each water sample into a first and second detection solution for comparison, lays the foundation for subsequent background matrix interference removal through difference calculation. By applying an AC signal to the second detection solution and monitoring the impedance value change in real time, it dynamically determines whether the complexation reaction between the detection reagent and lithium ions has reached equilibrium, effectively solving the problems of lacking a reaction completion judgment mechanism and easily introducing systematic errors due to incomplete reaction equilibrium in existing technologies. The application of the AC signal accelerates the diffusion and mixing process of the reagent and ions, while continuous impedance value monitoring provides an objective criterion for the reaction endpoint, ensuring that the reaction is in a stable state before spectral acquisition, thereby significantly improving the reliability and accuracy of subsequent spectroscopic measurement results.

[0045] Optionally, the process of applying an AC signal to the second detection liquid of each water sample in step S102 until the impedance value changes after multiple measurements are within a preset allowable range can specifically include: Figure 2 A schematic flowchart of a controlled impedance measurement process according to an embodiment of this application is shown. Figure 2 As shown, the method includes: S1021. The impedance of the second detection liquid of each water sample after the AC signal is applied is measured at a preset time interval to obtain multiple impedance values ​​within a continuous measurement time.

[0046] The preset time interval refers to the fixed time interval used when continuously measuring the impedance of the second detection liquid. It can be a specific value between 30 seconds and 120 seconds, and this interval is used to control the time resolution of impedance data acquisition. The continuous measurement time refers to the entire time interval during which impedance measurement is continuously performed from the start of applying the AC signal, and can be a cumulative period spanning multiple preset time intervals. Multiple impedance values ​​refer to a series of impedance data measured sequentially according to the preset time intervals during the continuous measurement time, and can be a sequence of impedance values ​​arranged in chronological order.

[0047] For the second test solution of each water sample, after the AC signal is applied, periodic impedance measurements are performed at preset time intervals to obtain dynamic data on the impedance value changing over time during the reaction. First, the specific value of the preset time interval is determined, which can be 60 seconds, and this interval is used as the time reference for impedance acquisition.

[0048] Next, while applying an alternating current signal to the second detection liquid through the electrodes, the impedance measuring device records the impedance value at the end of each preset time interval. The impedance value can be calculated by measuring the current and voltage amplitude and phase difference across the electrodes using a known impedance calculation method. Then, as the alternating current signal application time continues to extend, the impedance values ​​corresponding to the first, second, and up to the Nth measurement are obtained sequentially. These impedance values ​​are arranged in chronological order of measurement time to form multiple impedance values ​​within a continuous measurement period.

[0049] S1022. Calculate the absolute value of the difference between the impedance values ​​corresponding to two adjacent measurement times to obtain the change in impedance between adjacent measurements.

[0050] The change in impedance between adjacent measurements refers to the absolute value of the difference between two adjacent impedance values ​​in the impedance value sequence. It can be a value that reflects the amplitude of impedance fluctuation between two adjacent measurement times, and the smaller the value, the more stable the change trend of the reaction system is during that period.

[0051] Based on the impedance value sequence obtained in step S1021, the difference between the impedance values ​​corresponding to each two adjacent measurement times in the sequence is calculated to quantify the trend of impedance change over time during the reaction process. First, two adjacent impedance values ​​are sequentially taken from the impedance value sequence, i.e., the first two values ​​are the first two values. The measured value and the first The measured values ​​are then analyzed. Next, the difference between the two values ​​is calculated and its absolute value is taken to obtain the corresponding change in adjacent impedance. This calculation can be expressed as follows: ,in For the first The impedance value measured in this study. For the first The impedance value measured in this study. For the first Next and first The change in impedance between adjacent measurements. It is a positive integer greater than 1. Then, the absolute value of the difference between all adjacent measurements in the impedance value sequence is calculated in the above manner, and finally the adjacent impedance change sequence corresponding to the impedance value sequence is obtained.

[0052] S1023. Determine whether the changes in a preset number of consecutive adjacent impedances are all within the preset allowable range.

[0053] S1024. If so, stop applying the AC signal to the second detection liquid.

[0054] The preset quantity refers to the number of adjacent impedance changes that must continuously meet the preset allowable range conditions to determine whether the reaction has reached equilibrium. It can be a certain value between 3 and 5 times, and this quantity is set to avoid misjudgment caused by random fluctuations and improve the stability of the equilibrium determination result.

[0055] Based on the sequence of adjacent impedance changes obtained in step S1022, the values ​​in this sequence are compared sequentially with a preset allowable range to determine whether the reaction system has reached a stable equilibrium state. First, the specific values ​​of the preset quantity and preset allowable range are determined according to the background conductivity of the water sample and the complexation reaction kinetics of the detection reagent. Specifically, for high-salinity, low-initial-impedance water samples such as reverse osmosis concentrated brine, the preset allowable range is set to 0.5% of the initial impedance value to sensitively capture minute relative impedance changes. For relatively low-salinity water samples such as raw seawater, this is relaxed to 1.5% to 2% of the initial impedance value. Simultaneously, the preset quantity needs to be determined based on the degree of interference from the water matrix. For nodes with more complex matrices and greater electrochemical noise, such as pretreatment solutions, the preset quantity is increased to 5 times; for conventional water samples, 3 times are taken.

[0056] Next, starting from the beginning of the sequence of adjacent impedance changes, it is determined whether each adjacent impedance change is within a preset allowable range. If an adjacent impedance change exceeds the preset allowable range, the counting restarts from the next adjacent impedance change. Then, when the number of consecutive adjacent impedance changes reaches a preset number and all are within the preset allowable range, it is determined that the complexation reaction between the detection reagent and lithium ions has reached equilibrium. At this point, the control device stops applying an AC signal to the second detection liquid.

[0057] This embodiment obtains a continuous data sequence of impedance value changes over time during the reaction process by periodically measuring the impedance of the second detection liquid at preset time intervals. By calculating the absolute value of the difference between adjacent measured values, the dynamic change of impedance is transformed into a quantifiable and comparable index of adjacent impedance changes. Then, by using the condition that the changes are within a preset allowable range for a preset number of consecutive times, the moment when the complexation reaction between the detection reagent and lithium ions reaches equilibrium is accurately identified and the application of the AC signal is stopped in a timely manner.

[0058] This process combines multiple continuous measurements with dual-condition judgment to avoid misjudgments caused by single or accidental fluctuations. It ensures that the electrical signal is only applied after the reaction system has stabilized. This effectively solves the problems of lack of reaction completion judgment mechanism and easy introduction of systematic errors due to the reaction not reaching equilibrium in the existing technology, and significantly improves the accuracy and repeatability of lithium ion concentration detection results.

[0059] S103. Perform ultraviolet absorption spectroscopy, visible absorption spectroscopy and fluorescence spectroscopy on the first and second test solutions of each water sample to obtain the first and second spectra of each water sample.

[0060] Optionally, step S103, which involves performing ultraviolet absorption spectroscopy, visible absorption spectroscopy, and fluorescence spectroscopy on the first and second detection solutions of each water sample to obtain the first and second spectra of each water sample, may specifically include: Figure 3 A schematic diagram illustrating the process of generating a first spectrum and a second spectrum according to an embodiment of this application is shown. Figure 3 As shown, the method includes: S1031. When measuring the first and second detection solutions of each water sample, an ultraviolet light source, a visible light source, and a fluorescent excitation light source are used to irradiate the first and second detection solutions respectively, so as to obtain a first light intensity record corresponding to the first detection solution and a second light intensity record corresponding to the second detection solution. The on and off frequencies of the ultraviolet light source, the visible light source, and the fluorescent excitation light source are different from each other. The first and second light intensity records include the light intensity values ​​that change with the measurement time at each measurement wavelength.

[0061] An ultraviolet (UV) light source is a device that emits UV light to excite a detection solution and produce a UV absorption response; it can be a light source with an emission wavelength range of 200 nm to 400 nm. A visible light source is a device that emits visible light to excite a detection solution and produce a visible absorption response; it can be a light source with an emission wavelength range of 400 nm to 760 nm. A fluorescence excitation light source is a device that emits light of a specific wavelength to excite fluorophores in a detection solution and produce fluorescence emission; it can be a monochromatic light source with an emission wavelength matching the excitation wavelength of the fluorophores in the detection reagent.

[0062] The on / off frequency refers to the frequency corresponding to the periodic on and off states of each light source during the irradiation process, and can be set to different frequency values ​​for ultraviolet light sources, visible light sources, and fluorescence excitation light sources. The first light intensity record refers to the set of light intensity data recorded during the measurement of the first detection liquid, and can include the light intensity values ​​changing with measurement time at each measurement wavelength. The second light intensity record refers to the set of light intensity data recorded during the measurement of the second detection liquid, and can include the light intensity values ​​changing with measurement time at each measurement wavelength; the recording method is the same as the first light intensity record.

[0063] For each water sample, the first and second test solutions are simultaneously irradiated with ultraviolet light, visible light, and fluorescence excitation light, and light intensity records are collected sequentially to obtain multiple types of spectral information in a single measurement. First, for the first test solution, steps S10311 and S10312 complete the simultaneous irradiation and light intensity recording of the ultraviolet, visible, and fluorescence excitation light sources. Then, for the second test solution, steps S10313 and S10314 complete the same irradiation and light intensity recording.

[0064] During illumination, the three types of light sources are periodically turned on and off at distinct on / off frequencies. The specific values ​​of these on / off frequencies can be determined based on the sampling rate of the photodetector. For example, the on / off frequency of the ultraviolet light source can be 50Hz, the visible light source can be 70Hz, and the fluorescence excitation source can be 90Hz. These values ​​are distinct and non-integer multiples of each other to avoid signal separation difficulties caused by frequency aliasing. Then, during the measurement process, the photodetector continuously receives the mixed light signal formed by the detection liquid under the combined illumination of the three light sources and records the corresponding light intensity values ​​according to the measurement time and wavelength, thus forming a light intensity record that includes contributions from multiple light sources.

[0065] Optionally, step S1031, which involves irradiating the first detection liquid and the second detection liquid with an ultraviolet light source, a visible light source, and a fluorescence excitation light source, respectively, to obtain a first light intensity record corresponding to the first detection liquid and a second light intensity record corresponding to the second detection liquid, may specifically include: S10311. When measuring the first detection solution, the ultraviolet light source, the visible light source, and the fluorescent excitation light source are irradiated with the first detection solution at their respective on / off frequencies within the same measurement time period.

[0066] The first detection solution is placed in the measurement cell, and three types of light sources are activated within the same measurement time period, periodically turning on and off according to preset on / off frequencies. Specifically, the ultraviolet light source is turned on and off at a frequency of 50 Hz, the visible light source at a frequency of 70 Hz, and the fluorescence excitation light source at a frequency of 90 Hz. The irradiation periods of the three types of light sources completely overlap, and all continuously act on the first detection solution within the same measurement time period, thus allowing the first detection solution to be modulated and irradiated by the three types of light sources simultaneously within the same time period.

[0067] S10312. The photodetector receives the ultraviolet transmitted light formed by the first detection liquid under ultraviolet light source irradiation, the visible transmitted light formed under visible light source irradiation, and the fluorescent emitted light formed under fluorescent excitation light source irradiation, and records the corresponding light intensity values ​​according to the measurement time and measurement wavelength to form the first light intensity record.

[0068] Ultraviolet transmitted light refers to the light that passes through the first detection solution after being irradiated by an ultraviolet light source, and its intensity carries information about the degree of ultraviolet light absorption by the detection solution. Visible transmitted light refers to the light that passes through the first detection solution after being irradiated by a visible light source, and its intensity carries information about the degree of visible light absorption by the detection solution. Fluorescent emitted light refers to the emitted light produced when the fluorescent substance in the first detection solution is excited by a fluorescent excitation source, and its intensity carries information about the fluorescence response of the detection solution.

[0069] The photodetector is positioned opposite the first detection liquid or at a specific angle, continuously receiving ultraviolet transmitted light, visible transmitted light, and fluorescent emitted light from three types of light sources. Because these three light sources alternate at different on / off frequencies, the photodetector actually receives a mixed light intensity signal formed by the superposition of these three light signals. The photodetector scans point-by-point within a preset measurement wavelength range and continuously records the light intensity value at each measurement wavelength at a fixed sampling interval. The sampling frequency must satisfy the Nyquist theorem, the sampling interval can be 0.001 seconds, and the recording duration covers the entire measurement period. The light intensity values ​​at each measurement wavelength that change over time are organized according to both measurement time and measurement wavelength to form the first light intensity record. .

[0070] S10313. When measuring the second detection solution, the ultraviolet light source, visible light source and fluorescent excitation light source are respectively irradiated with the second detection solution at their corresponding on / off frequencies during the same measurement time period.

[0071] After completing the measurement of the first detection solution, the second detection solution is placed in the measurement cell. Using the same method as in step S10311, the second detection solution is irradiated with ultraviolet light, visible light, and fluorescence excitation light at on / off frequencies of 50Hz, 70Hz, and 90Hz, respectively, within the same measurement time period. Since the detection reagent has been added to the second detection solution and has undergone a complexation reaction with lithium ions, its response characteristics to the three types of light sources have changed compared to the first detection solution. This change will be reflected in the subsequent light intensity recording and will serve as the basis for distinguishing between the background matrix signal and the lithium ion reaction signal.

[0072] S10314. The photodetector receives the ultraviolet transmitted light formed by the second detection liquid under ultraviolet light source irradiation, the visible transmitted light formed under visible light source irradiation, and the fluorescent emitted light formed under fluorescent excitation light source irradiation, and records the corresponding light intensity values ​​according to the measurement time and measurement wavelength to form a second light intensity record.

[0073] Using the same method as in step S10312, a photodetector continuously receives the mixed light intensity signal generated by the second detection liquid under the illumination of three types of light sources, and records the corresponding light intensity values ​​according to the measurement time and measurement wavelength to form a second light intensity record. .

[0074] S1032. Separate the ultraviolet transmitted light intensity value, visible transmitted light intensity value, and fluorescence emitted light intensity value from the first light intensity record according to the on / off frequency.

[0075] S1033. Separate the ultraviolet transmitted light intensity value, visible transmitted light intensity value, and fluorescence emitted light intensity value from the second light intensity record according to the on / off frequency.

[0076] Ultraviolet transmitted light intensity refers to the transmitted light intensity value separated from a mixed light intensity record, which is solely contributed by the ultraviolet source, and can be the signal component obtained after demodulation according to the on / off frequency of the ultraviolet source. Visible transmitted light intensity refers to the transmitted light intensity value separated from a mixed light intensity record, which is solely contributed by the visible source, and can be the signal component obtained after demodulation according to the on / off frequency of the visible source. Fluorescence emitted light intensity refers to the emitted light intensity value separated from a mixed light intensity record, which is solely contributed by the fluorescence excitation source, and can be the signal component obtained after demodulation according to the on / off frequency of the fluorescence excitation source.

[0077] Based on the first and second light intensity records obtained in step S1031, frequency demodulation is used to separate the contribution components of each light source from the mixed light intensity signal according to the different on / off frequencies of each light source. First, for the light intensity record changing with time at each measurement wavelength in the ultraviolet band, correlation demodulation is performed using a reference signal that matches the on / off frequency of the ultraviolet light source to extract the periodic component in the record that matches the on / off frequency of the ultraviolet light source, thus obtaining the ultraviolet transmitted light intensity value at that wavelength. Next, for the light intensity record changing with time at each measurement wavelength in the visible band, correlation demodulation is performed using a reference signal that matches the on / off frequency of the visible light source to extract the periodic component that matches the on / off frequency of the visible light source, thus obtaining the visible transmitted light intensity value at that wavelength.

[0078] Next, correlation demodulation is performed using a reference signal matching the on / off frequency of the visible light source to extract the periodic component consistent with the on / off frequency of the visible light source, thus obtaining the visible transmitted light intensity value at that wavelength. Then, correlation demodulation is performed using a reference signal matching the on / off frequency of the fluorescent excitation source to extract the periodic component consistent with the on / off frequency of the fluorescent excitation source, thus obtaining the fluorescent emitted light intensity value at that wavelength. The above demodulation operation can be implemented using the lock-in amplification principle, that is, the mixed light intensity signal is multiplied by the reference sine signal of the corresponding on / off frequency, and then low-pass filtered. The DC component obtained after filtering is the transmitted or emitted light intensity value corresponding to the light source.

[0079] S1034. Based on the ultraviolet transmitted light intensity value and the corresponding ultraviolet incident light intensity value of the first detection liquid, the ultraviolet absorbance and the visible transmitted light intensity value and the corresponding visible incident light intensity value are calculated, and the fluorescence intensity is integrated with the fluorescence emission light intensity value to obtain the first spectrum.

[0080] S1035. The ultraviolet absorbance and visible absorbance are calculated based on the ultraviolet transmitted light intensity value and the corresponding ultraviolet incident light intensity value, the visible transmitted light intensity value and the corresponding visible incident light intensity value of the second detection liquid, and the fluorescence intensity is integrated with the fluorescence emission light intensity value to obtain the second spectrum.

[0081] The ultraviolet incident light intensity refers to the initial light intensity of the ultraviolet light source before absorption by the detection liquid, and can be a fixed value obtained in advance through blank reference measurement. The visible incident light intensity refers to the initial light intensity of the visible light source before absorption by the detection liquid, and can be a fixed value obtained in advance through blank reference measurement. Ultraviolet absorbance is a value representing the degree of ultraviolet light absorption by the detection liquid, calculated based on the ultraviolet transmitted light intensity and the ultraviolet incident light intensity.

[0082] Visible absorbance is a numerical value representing the degree of visible light absorption by the test solution, calculated from the visible transmitted light intensity and the visible incident light intensity. Fluorescence intensity is a numerical value directly representing the fluorescence response of the test solution, expressed as the fluorescence emitted light intensity. The first spectrum refers to the spectral data composed of the ultraviolet absorbance, visible absorbance, and fluorescence intensity corresponding to the first test solution, arranged according to the measurement wavelength. The second spectrum refers to the spectral data composed of the ultraviolet absorbance, visible absorbance, and fluorescence intensity corresponding to the second test solution, arranged according to the measurement wavelength.

[0083] Based on the separated ultraviolet and visible transmitted light intensities, and combined with the pre-measured ultraviolet and visible incident light intensities, the absorbance is calculated according to Beer-Lambert's law. First, for each measurement wavelength, the ultraviolet transmitted light intensity and the corresponding ultraviolet incident light intensity are substituted into the absorbance calculation formula, which can be expressed as: ,in wavelength UV absorbance at that location. This represents the intensity of the ultraviolet transmitted light obtained at this wavelength. This is the pre-measured ultraviolet incident light intensity value at this wavelength.

[0084] Next, using the same method, substitute the visible transmitted light intensity value and the corresponding visible incident light intensity value into the formula. To obtain the wavelength Visible absorbance at ,in This represents the intensity of visible transmitted light at that wavelength. This represents the intensity of visible incident light at that wavelength.

[0085] Then, the fluorescence emission intensity value obtained by separation is directly used as the fluorescence intensity at that wavelength. No incident light intensity normalization is required. Finally, the UV absorbance, visible absorbance, and fluorescence intensity of the same detection solution at each measurement wavelength are integrated in wavelength order. The first spectrum is obtained by integrating the data for the first light intensity, and the second spectrum is obtained by integrating the data for the second light intensity.

[0086] This embodiment achieves simultaneous acquisition of UV, visible, and fluorescence spectral response data in a single measurement by simultaneously irradiating the same detection liquid with ultraviolet, visible, and fluorescence light sources at different on / off frequencies, and receiving the mixed light intensity signal formed by the combined effect of the three light sources within the same measurement time period using a photodetector. This avoids the need for multiple samplings required for time-series measurements and the influence of liquid state changes introduced by such measurements. Furthermore, the signal demodulation module accurately extracts the UV transmitted light intensity, visible transmitted light intensity, and fluorescence emitted light intensity, and calculates the UV absorbance and visible absorbance using Lambert-Beer's law. The fluorescence intensity is directly represented by the fluorescence emitted light intensity, ultimately integrating these to form a first and second spectrum encompassing multidimensional spectral characteristics.

[0087] This process combines simultaneous illumination from multiple light sources with frequency demodulation separation, which improves the synchronicity and consistency of the acquisition of various types of spectral information while ensuring measurement efficiency. This provides a reliable and complete data foundation for subsequent background matrix interference removal and accurate identification of lithium-ion characteristic peaks through difference calculation between the first and second spectra.

[0088] S104. Based on the difference in absorbance and fluorescence intensity between the first and second spectra of the same water sample, generate the third spectrum for each water sample. Based on the third spectrum of the pretreated liquid and the third spectrum of the tail liquid, determine the absorption peak and fluorescence peak corresponding to lithium ions within the water production cycle.

[0089] Optionally, step S104, which generates a third spectrum for each water sample based on the differences in absorbance and fluorescence intensity between the first and second spectra of the same water sample, may specifically include: S1041. At each measurement wavelength, calculate the difference in absorbance and the difference in fluorescence intensity between the second spectrum and the first spectrum of the same water sample to obtain the difference in absorbance and the difference in fluorescence intensity.

[0090] The absorbance difference refers to the difference between the absorbance value of the second spectrum and the absorbance value of the first spectrum for the same water sample at the same measurement wavelength. It can be categorized into ultraviolet absorbance difference and visible absorbance difference, and this difference reflects the degree of change in the light absorption characteristics of the water sample after the reaction of the detection reagent with lithium ions, compared to the original water sample background. The fluorescence intensity difference refers to the difference between the fluorescence intensity value of the second spectrum and the fluorescence intensity value of the first spectrum for the same water sample at the same measurement wavelength, and this difference reflects the degree of change in the fluorescence response characteristics of the water sample after the reaction of the detection reagent with lithium ions, compared to the original water sample background.

[0091] Based on the first and second spectra of each water sample obtained in step S103, the differences are calculated for each data point at the same measurement wavelength to extract the spectral response changes caused solely by the reaction between the detection reagent and lithium ions. First, for the ultraviolet band, at each measurement wavelength, the ultraviolet absorbance in the second spectrum is subtracted from the ultraviolet absorbance at the same measurement wavelength in the first spectrum to obtain the ultraviolet absorbance difference at that wavelength. The calculation method can be expressed as follows: ,in The first spectrum at wavelength UV absorbance at that location. The second spectrum represents the ultraviolet absorbance at the same wavelength. This represents the difference in ultraviolet absorbance at that wavelength.

[0092] Next, for the visible band, the visible absorbance difference is calculated using the same method, which can be expressed as follows: ,in The first spectrum at wavelength Visible absorbance at that location Let be the visible absorbance of the second spectrum at the same wavelength. Then, for the fluorescence band, subtract the fluorescence intensity in the second spectrum from the fluorescence intensity at the same measurement wavelength in the first spectrum to obtain the fluorescence intensity difference at that wavelength. This can be calculated as follows: ,in The first spectrum at wavelength fluorescence intensity at that location The fluorescence intensity of the second spectrum at the same wavelength.

[0093] The above calculations were performed point by point for each measurement wavelength. Since the first detection solution does not contain the detection reagent while the second detection solution contains the detection reagent and has completed the complexation reaction with lithium ions, the difference between the two represents the spectral increment contributed by the reaction between the reagent and lithium ions, thereby effectively stripping away the inherent absorption and inherent fluorescence components of the water sample's own background matrix in the ultraviolet and visible bands.

[0094] S1042. Arrange the absorbance difference and fluorescence intensity difference corresponding to each measurement wavelength in order from short wavelength to long wavelength to generate the third spectrum of each water sample.

[0095] The third spectrum refers to the spectral data composed of the differences in absorbance and fluorescence intensity of the same water sample at various measurement wavelengths, arranged in order from shortest to longest wavelength. This spectrum eliminates the inherent spectral contribution of the water sample's own background matrix and retains only the response change information caused by the reaction between the detection reagent and lithium ions.

[0096] Based on the absorbance difference and fluorescence intensity difference values ​​of each water sample calculated in step S1041 at each measurement wavelength, these values ​​are systematically organized according to wavelength to form a difference spectrum that directly reflects the characteristics of lithium-ion reactions. First, the ultraviolet absorbance difference and visible absorbance difference values ​​are arranged sequentially from shortest to longest wavelength, forming the absorbance difference curve for the water sample. Next, the fluorescence intensity difference values ​​are similarly arranged sequentially from shortest to longest wavelength, forming the fluorescence intensity difference curve for the water sample. Finally, the absorbance difference curve and the fluorescence intensity difference curve are integrated according to their corresponding wavelengths to form the third spectrum of the water sample.

[0097] Optionally, the process of determining the absorption and fluorescence peaks corresponding to lithium ions during the water production cycle based on the third spectrum of the pretreated water sample and the third spectrum of the tailings water sample in step S104 may specifically include: S1043. The wavelength in the third spectrum of the pretreated water sample where the absorbance difference is greater than the absorbance difference between the previous and subsequent measurement wavelengths is determined as the candidate absorption wavelength.

[0098] Candidate absorption wavelength refers to the wavelength in the third spectrum of the pretreated water sample where the absorbance difference is greater than the absorbance difference between the two adjacent wavelengths. This wavelength exhibits a local peak shape on the absorbance difference curve and can be the wavelength position where potential lithium ion absorption characteristics are located.

[0099] Based on the third spectrum of the pretreated water sample obtained in step S1042, local extrema were determined point by point on the absorbance difference curve to preliminarily screen the wavelength positions that might correspond to the lithium-ion absorption response. Considering that random high-frequency noise in actual spectral measurements can easily lead to false peak identification, the Savitzky-Golay filtering algorithm was first used to smooth and denoise the absorbance difference curve, with a smoothing window size of 15 data points and a fitting polynomial order of 3. Then, starting from the second measurement wavelength of the smoothed absorbance difference curve, the absorbance difference at the current measurement wavelength was compared with the absorbance differences at the previous and next measurement wavelengths.

[0100] If the absorbance difference at the current measurement wavelength is greater than the absorbance differences at both the previous and next measurement wavelengths, and the difference between the absorbance difference at the current wavelength and the absorbance difference at the adjacent trough is greater than the preset absorption peak spike threshold, then a true and effective local peak is determined at that measurement wavelength, and this measurement wavelength is identified as a candidate absorption wavelength. The preset absorption peak spike threshold is set to three times the standard deviation of the background spectral noise in that band. Then, following the above method, all measurement wavelengths in the absorbance difference curve, excluding the beginning and end, are sequentially traversed to obtain all candidate absorption wavelengths corresponding to the pretreated liquid water sample.

[0101] S1044. The fluorescence intensity difference in the third spectrum of the pretreated water sample is determined as the candidate fluorescence wavelength when the fluorescence intensity difference is greater than the difference between the previous and subsequent measurement wavelengths.

[0102] Candidate fluorescence wavelength refers to the measurement wavelength in the third spectrum of the pretreated water sample where the fluorescence intensity difference is greater than the fluorescence intensity difference between the two adjacent measurement wavelengths. This wavelength exhibits a local peak shape on the fluorescence intensity difference curve and can be the wavelength position where the potential lithium-ion fluorescence characteristics are located.

[0103] Based on the third spectrum of the pretreated water sample obtained in step S1042, local extrema are determined point-by-point on the fluorescence intensity difference curve to preliminarily screen the wavelength positions that may correspond to the lithium-ion fluorescence response. The determination method is consistent with the determination method for the absorbance difference curve in step S1043. First, the fluorescence intensity difference curve is smoothed and denoised using the Savitzky-Golay filtering algorithm, with a smoothing window size of 15 data points and a fitting polynomial order of 3. Then, starting from the second measurement wavelength of the smoothed fluorescence intensity difference curve, the fluorescence intensity difference at the current measurement wavelength is compared with the fluorescence intensity differences at the previous and next measurement wavelengths.

[0104] If the fluorescence intensity difference at the current measurement wavelength is greater than the fluorescence intensity differences at both the previous and next measurement wavelengths, and the difference between the fluorescence intensity difference at the current wavelength and the adjacent trough is greater than the preset fluorescence peak protrusion threshold, then a true and effective local peak is determined at that measurement wavelength, and this measurement wavelength is identified as a candidate fluorescence wavelength. The preset fluorescence peak protrusion threshold is set to three times the standard deviation of the background fluorescence noise. Then, following the above method, all measurement wavelengths in the fluorescence intensity difference curve, excluding the beginning and end, are sequentially traversed to obtain all candidate fluorescence wavelengths corresponding to the pretreated solution water sample.

[0105] S1045. Peaks formed at candidate absorption wavelengths with absorbance differences greater than the absorbance difference at the same measurement wavelength in the third spectrum of the tail liquid are identified as the absorption peaks corresponding to lithium ions.

[0106] An absorption peak refers to the characteristic peak formed by lithium ions on the absorbance difference curve after screening by comparing candidate absorption wavelengths with the third spectrum of the tail liquid water sample. The wavelength position of the peak indicates the characteristic response position of lithium ions reacting with the detection reagent in the ultraviolet or visible band.

[0107] Based on the candidate absorption wavelength set corresponding to the pretreated liquid sample obtained in step S1043, and combined with the third spectrum of the tail liquid sample within the same production cycle in step S1042, a comparative screening is performed to eliminate false peaks formed by non-lithium ion responses and confirm the absorption peaks that truly correspond to lithium ions. Since the lithium extraction unit has effectively removed lithium ions from the water, if the peak value at the candidate absorption wavelength is indeed caused by the lithium ion reaction, the absorbance difference of the tail liquid sample at that wavelength should be significantly lower than that of the pretreated liquid sample.

[0108] First, for each candidate absorption wavelength in the candidate absorption wavelength set, the absorbance difference at the same measurement wavelength in the third spectrum of the tailings water sample is extracted. Next, the absorbance difference of the pretreated water sample at the same candidate absorption wavelength is compared with that of the tailings water sample at the same measurement wavelength. Then, if the absorbance difference of the pretreated water sample at the same candidate absorption wavelength is greater than that of the tailings water sample at the same measurement wavelength, the peak formed at that candidate absorption wavelength is determined to be the absorption peak corresponding to lithium ions; otherwise, that candidate absorption wavelength is excluded.

[0109] S1046. Peaks formed at candidate fluorescence wavelengths with fluorescence intensity differences greater than the fluorescence intensity differences at the same measurement wavelength in the third spectrum of the tail liquid are identified as the fluorescence peaks corresponding to lithium ions.

[0110] The fluorescence peak refers to the characteristic peak formed by lithium ions on the fluorescence intensity difference curve after screening by comparing the candidate fluorescence wavelengths with the third spectrum of the tail liquid water sample. The wavelength position of the peak indicates the characteristic response position of lithium ions reacting with the detection reagent in the fluorescence band.

[0111] Based on the candidate fluorescence wavelength set corresponding to the pretreated liquid sample obtained in step S1044, and combined with the third spectrum of the tail liquid sample within the same production cycle, the same comparison and screening logic as in step S1045 is used to confirm the fluorescence peak truly corresponding to lithium ions. First, for each candidate fluorescence wavelength in the candidate fluorescence wavelength set, the fluorescence intensity difference at the same measurement wavelength in the third spectrum of the tail liquid sample is extracted. Next, the fluorescence intensity difference of the pretreated liquid sample at this candidate fluorescence wavelength is compared with the fluorescence intensity difference of the tail liquid sample at the same measurement wavelength. Then, if the fluorescence intensity difference of the pretreated liquid sample at this candidate fluorescence wavelength is greater than the fluorescence intensity difference of the tail liquid sample at the same measurement wavelength, the peak formed at this candidate fluorescence wavelength is determined to be the fluorescence peak corresponding to lithium ions; otherwise, the candidate fluorescence wavelength is excluded.

[0112] This embodiment calculates the absorbance difference and fluorescence intensity difference between the second and first spectra of the same water sample at each measurement wavelength, and integrates them in wavelength order to generate a third spectrum that only reflects the contribution of the reaction between the reagent and lithium ions. This effectively removes the inherent response interference of the water sample's own background matrix in the ultraviolet, visible and fluorescence dimensions.

[0113] Furthermore, by extracting local peaks from the third spectrum of the pretreated solution as candidate absorption and fluorescence wavelengths, and comparing them with the characteristic that the response of the third spectrum of the tail liquid sample after lithium extraction within the same production cycle is significantly reduced at the same wavelength, spurious peaks formed by non-lithium ion responses were eliminated, accurately pinpointing the true absorption and fluorescence peak positions corresponding to lithium ions within the current production cycle. This process, combining difference calculation with comparison screening at nodes within the same cycle, overcomes difficulties such as the complexity of the seawater matrix, strong interference from coexisting ions, and the drift of characteristic peak positions caused by water quality fluctuations.

[0114] S105. Based on the absorption peak and fluorescence peak, determine the corresponding absorbance change and fluorescence intensity change from the third spectrum of each water sample. Based on the absorbance change and fluorescence intensity change, determine the lithium ion concentration of each water sample using the pre-calibrated correspondence between the lithium ion concentration and the absorbance change and fluorescence intensity change.

[0115] Optionally, before determining the lithium ion concentration of each water sample in step S105 based on the change in absorbance and the change in fluorescence intensity using a pre-calibrated correspondence between the lithium ion concentration and the changes in absorbance and fluorescence intensity, the method further includes: Salt solutions with the same conductivity were prepared for the raw seawater, reverse osmosis concentrated brine, pretreatment solution before lithium extraction, and tailings solution after lithium extraction. Each salt solution was divided into multiple portions, and different preset amounts of lithium ion solutions of known concentration were added to each portion to obtain multiple lithium standard solutions with different lithium ion concentrations.

[0116] Salt solutions with identical conductivity refer to simulated matrix solutions prepared for each of the actual water samples corresponding to the original seawater, reverse osmosis concentrated brine, pretreated liquid, and tailings, respectively, with the same conductivity value as the water sample. The conductivity of the solution can be kept consistent with the measured conductivity of the corresponding water sample by adjusting the concentration of major salts such as sodium chloride and magnesium chloride. This solution is used to simulate the ionic strength background of the actual water sample to eliminate the influence of matrix effects on the calibration results. Lithium standard solutions refer to solutions with known lithium ion concentrations prepared by adding a lithium ion solution of known concentration to the aforementioned salt solutions with identical conductivity. These solutions can include combinations of solutions with multiple lithium ion concentration gradients and are used to establish a quantitative correlation between lithium ion concentration and spectral response.

[0117] For the four types of water samples at different nodes, matrix-matched lithium standard solutions were prepared to ensure that the established correspondences could be accurately applied to the real-world testing scenarios of each node. First, the conductivity values ​​of the raw seawater, reverse osmosis concentrated brine, pretreatment solution, and tailings were measured and used as the target conductivity for preparing the corresponding salt solutions.

[0118] Next, based on the target conductivity of each water sample at each node, four types of salt solutions with conductivity consistent with the corresponding water sample were prepared by adjusting the concentration of the main salts. This process was monitored and adjusted in real time using a conductivity meter until the difference between the conductivity of the prepared solution and the measured value of the corresponding water sample was within an acceptable range. Then, different preset amounts of lithium ion solution of known concentration were added to each salt solution. The known concentration lithium ion solution could be a lithium chloride standard solution.

[0119] To ensure the accuracy of the multiple linear regression model, the amount added needs to be determined based on the actual background concentration range of the water samples at each node in the actual seawater lithium extraction process: for the salt solution corresponding to the original seawater, the preset lithium ion concentration gradient range is set to 0.1 mg / L to 0.3 mg / L; for the salt solution corresponding to the reverse osmosis concentrated brine, due to the concentration effect of reverse osmosis, the preset concentration gradient range is set to 0.2 mg / L to 0.6 mg / L; for the salt solution corresponding to the pretreatment liquid before lithium extraction, the preset concentration gradient range is set to 0.2 mg / L to 0.6 mg / L; for the salt solution corresponding to the tail liquid after lithium extraction, since most of the lithium has been extracted, the preset concentration gradient range is set to 0.01 mg / L to 0.05 mg / L.

[0120] Calculate the changes in absorbance and fluorescence intensity for each lithium standard solution.

[0121] The change in absorbance refers to the difference in absorbance read from the third spectrum at the absorption peak wavelength determined in step S104 after adding the detection reagent, performing spectral measurement, and calculating the difference in the lithium standard solution according to the procedures described in steps S102 to S104. For the purpose of establishing a unified model representation, it is uniformly defined as the change in absorbance. Furthermore, this value reflects the magnitude of absorbance change caused by the reaction of lithium ions in the lithium standard solution with the detection reagent.

[0122] The change in fluorescence intensity refers to the difference in fluorescence intensity read from the third spectrum at the fluorescence peak wavelength determined in step S104 after detecting the lithium standard solution according to the above procedure. This difference is uniformly defined as the change in fluorescence intensity. Furthermore, this value reflects the range of fluorescence intensity changes caused by the reaction of lithium ions in the lithium standard solution with the detection reagent.

[0123] For the lithium standard solution series corresponding to various nodes obtained, the detection solution preparation, AC signal equilibrium determination, multispectral measurement, and third spectrum generation are carried out sequentially according to the complete process of steps S102 to S104 to obtain the spectral response values ​​of each lithium standard solution at the absorption peak and fluorescence peak wavelengths. First, each lithium standard solution is divided into two portions according to step S102. One portion is kept as the first detection solution and the other portion is used as the second detection solution. The detection reagent is added to the other portion and an AC signal is applied until the reaction reaches equilibrium.

[0124] Next, following step S103, the two test solutions were subjected to UV, Visible, and Fluorescence spectral measurements to obtain the corresponding first and second spectra. Then, following step S104, the difference was calculated to generate the third spectrum. Finally, from the third spectrum of each lithium standard solution, the absorbance difference corresponding to the wavelength positions of each absorption peak determined in step S104 was extracted as the absorbance change of that lithium standard solution. Simultaneously, the fluorescence intensity difference corresponding to the wavelength position of each fluorescence peak was extracted as the fluorescence intensity change of the lithium standard solution. .

[0125] Based on the changes in lithium ion concentration, absorbance, and fluorescence intensity of each lithium standard solution, a corresponding relationship is established with the corresponding water sample.

[0126] The correspondence relationship refers to the quantitative mapping relationship established between the lithium ion concentration values ​​of a series of lithium standard solutions corresponding to a specific node water sample and the corresponding changes in absorbance and fluorescence intensity. It can be a multiple linear regression model with lithium ion concentration as the dependent variable and changes in absorbance and fluorescence intensity as independent variables, and can be used to back-calculate the lithium ion concentration under known absorbance and fluorescence intensity changes. Because the matrix composition and conductivity of the four types of node water samples differ significantly, an independent correspondence relationship is established for each type of node water sample to ensure that the quantitative calculation of lithium ion concentration in each node water sample is not affected by matrix differences.

[0127] Based on the lithium ion concentration, absorbance change sequences, and fluorescence intensity change sequences of the lithium standard solution series corresponding to various node water samples, independent correspondences were established for each type of node water sample. First, for the calibration data corresponding to the original seawater, the absorbance change was used as the basis for... and fluorescence intensity change Using lithium ion concentration as the dependent variable and lithium ion concentration as the independent variable, a quantitative mapping relationship is established by fitting the data using multiple linear regression. The model can be expressed as follows: ,in The lithium-ion concentration to be predicted. This represents the change in absorbance. The change in fluorescence intensity and For the corresponding regression coefficients, For the intercept term, all the above coefficients were obtained by fitting the calibration data of the lithium standard solution series using the least squares method. The goodness of fit can be determined by the coefficient of determination. Assessment and requirements Not less than 0.99.

[0128] Next, using the same method, independent correspondences were established for the lithium standard solution series corresponding to the reverse osmosis concentrated brine, pretreatment solution, and tailings, respectively. The regression model structure for each node water sample was the same, but the regression coefficients were obtained independently. Then, the above four sets of independent correspondences were bound and stored with the corresponding node water samples, serving as the calibration basis for the quantitative calculation of lithium ion concentration in each node water sample in step S105.

[0129] Based on the third spectra of the four types of water samples obtained in step S104, and the determined wavelength positions of absorption and fluorescence peaks, the measured absorbance change and fluorescence intensity change of each water sample are extracted sequentially, and the quantitative calculation of lithium ion concentration is completed by combining the pre-established correspondence. First, for the third spectrum of each water sample, according to the wavelength positions of each absorption peak determined in step S104, the corresponding absorbance difference is read from the third spectrum of the water sample as the measured absorbance change of the water sample. .

[0130] Simultaneously, based on the wavelength position of each fluorescence peak, the corresponding fluorescence intensity difference was read as the measured fluorescence intensity change of the water sample. Next, based on the pre-established correspondence between corresponding nodes in the selection of water sample types for that node, the measured values ​​are... and Substitute into the correspondence model The lithium ion concentration of the water sample at that node was calculated. ,in , , The regression coefficients are pre-calibrated in the correspondence bound to the water sample at this node. Then, the above operation is performed sequentially on the four types of water samples at the node: raw seawater, reverse osmosis concentrated brine, pretreated liquid, and tailings liquid. Each water sample at the node is calculated using its own bound independent correspondence, and finally the lithium ion concentration of each of the four types of water samples at the node within the same water production cycle is obtained.

[0131] This embodiment ensures that the matrix environment used in the calibration process is highly consistent with the actual water samples at each of the four node types by preparing salt solutions with the same conductivity and a series of lithium standard solutions with multiple concentration gradients. This eliminates the matrix effect interference of differences in ion intensity between water samples at different node types on the spectral response. Furthermore, by obtaining the changes in absorbance and fluorescence intensity for each lithium standard solution according to the complete detection procedure, and by performing multiple linear regression fitting between the two types of spectral responses and lithium ion concentration, an independent and accurate correspondence was established for each type of water sample at each node.

[0132] Based on this, the measured response quantities are extracted from the third spectrum of water samples at each node according to the wavelength positions of the absorption peak and fluorescence peak dynamically determined in the current water production cycle. These are then substituted into the independent correspondence of each node to complete the quantitative calculation of lithium ion concentration. Finally, the lithium ion concentration results of the four nodes—raw seawater, reverse osmosis concentrated brine, pretreated liquid, and tailings liquid—are output within the same water production cycle.

[0133] This process effectively overcomes the difficulty that a single standard curve cannot be applied across nodes due to the significant differences in water sample matrix at each node in the seawater lithium extraction process, by combining matrix matching calibration, two-dimensional spectral fusion modeling, and multi-node independent correspondence. It achieves accurate quantitative detection of lithium ion concentration under complex water quality conditions.

[0134] Figure 4 This is a schematic diagram illustrating a specific implementation of a seawater lithium-ion concentration detection system based on multispectral fusion, as provided in this application. (Refer to...) Figure 4 The system may include: The acquisition module 410 is used to collect water samples of raw seawater, reverse osmosis brine, pre-treatment liquid before lithium extraction, and tailings liquid after lithium extraction within the same water production cycle. The dividing module 420 is used to divide each water sample into a first detection solution and a second detection solution, and to add a detection reagent that reacts with lithium ions to produce color and fluorescence changes. An AC signal is applied to the second detection solution of each water sample until the impedance value changes measured multiple times are within a preset allowable range and then the process stops. The measurement module 430 is used to perform ultraviolet absorption spectroscopy, visible absorption spectroscopy and fluorescence spectroscopy on the first and second test solutions of each water sample to obtain the first and second spectra of each water sample. The generation module 440 is used to generate a third spectrum for each water sample based on the difference in absorbance and fluorescence intensity between the first and second spectra of the same water sample, and to determine the absorption peak and fluorescence peak corresponding to lithium ions within the water production cycle based on the third spectrum of the pretreated liquid water sample and the third spectrum of the tail liquid water sample. The generation module 440 is also used to determine the corresponding absorbance change and fluorescence intensity change from the third spectrum of each water sample according to the absorption peak and fluorescence peak, and to determine the lithium ion concentration of each water sample based on the absorbance change and fluorescence intensity change using the pre-calibrated correspondence between the lithium ion concentration and the absorbance change and fluorescence intensity change.

[0135] The seawater lithium-ion concentration detection system based on multispectral fusion in this application embodiment is used to implement the aforementioned seawater lithium-ion concentration detection method based on multispectral fusion. Therefore, the specific implementation of the seawater lithium-ion concentration detection system based on multispectral fusion can be found in the embodiment section of the seawater lithium-ion concentration detection method based on multispectral fusion above. The specific implementation can be referred to the description of the corresponding embodiments, and will not be repeated here.

[0136] Electronic devices may include processors and memory storing computer program instructions.

[0137] Specifically, the processor may include a central processing unit (CPU), an application-specific integrated circuit (ASIC), or one or more integrated circuits that can be configured to implement the embodiments of this application.

[0138] The memory may include a large-capacity storage device for data or instructions. For example, and not limitingly, the memory may include a hard disk drive (HDD), a floppy disk drive, flash memory, optical disk, magneto-optical disk, magnetic tape, or a Universal Serial Bus (USB) drive, or a combination of two or more of these. Where appropriate, the memory may include removable or non-removable (or fixed) media. Where appropriate, the memory may be internal or external to the integrated gateway disaster recovery device. In a particular embodiment, the memory is non-volatile solid-state memory.

[0139] Memory may include read-only memory (ROM), random access memory (RAM), disk storage media devices, optical storage media devices, flash memory devices, and electrical, optical, or other physical / tangible memory storage devices. Therefore, typically, memory includes one or more tangible (non-transitory) computer-readable storage media (e.g., memory devices) encoded with software including computer-executable instructions, and when the software is executed (e.g., by one or more processors), it is operable to perform the operations described with reference to the method according to the first aspect of this disclosure.

[0140] The processor reads and executes computer program instructions stored in the memory to implement any of the multispectral fusion-based seawater lithium ion concentration detection methods described in the above embodiments.

[0141] In one example, the electronic device may also include a communication interface and a bus. The processor, memory, and communication interface are connected via the bus and communicate with each other.

[0142] The communication interface is mainly used to realize communication between various modules, devices, units and / or equipment in the embodiments of this application.

[0143] A bus, including hardware, software, or both, couples components of an online data traffic metering device together. For example, and not limitingly, a bus may include an Accelerated Graphics Port (AGP) or other graphics bus, an Enhanced Industry Standard Architecture (EISA) bus, a Front Side Bus (FSB), HyperTransport (HT) interconnect, an Industry Standard Architecture (ISA) bus, an Infinite Bandwidth Interconnect, a Low Pin Count (LPC) bus, a memory bus, a Microchannel Architecture (MCA) bus, a Peripheral Component Interconnect (PCI) bus, a PCI-Express (PCI-X) bus, a Serial Advanced Technology Attachment (SATA) bus, a Video Electronics Standards Association Local (VLB) bus, or other suitable buses, or combinations of two or more of these. Where appropriate, a bus may include one or more buses. Although specific buses are described and illustrated in embodiments of this application, this application contemplates any suitable bus or interconnect.

[0144] The electronic device can execute the seawater lithium-ion concentration detection method based on multispectral fusion in the embodiments of this application, thereby realizing the seawater lithium-ion concentration detection method based on multispectral fusion described in conjunction with the accompanying drawings.

[0145] Furthermore, in conjunction with the multispectral fusion-based seawater lithium ion concentration detection method described in the above embodiments, this application embodiment can provide a computer-readable storage medium for implementation. This computer-readable storage medium stores computer program instructions; when executed by a processor, these computer program instructions implement any of the multispectral fusion-based seawater lithium ion concentration detection methods described in the above embodiments.

[0146] It should be clarified that this application is not limited to the specific configurations and processes described above and shown in the figures. For the sake of brevity, detailed descriptions of known methods are omitted here. In the above embodiments, several specific steps are described and shown as examples. However, the method process of this application is not limited to the specific steps described and shown. Those skilled in the art can make various changes, modifications, and additions, or change the order of steps, after understanding the spirit of this application.

[0147] The functional blocks shown in the above-described structural diagram can be implemented as hardware, software, firmware, or a combination thereof. When implemented in hardware, they can be, for example, electronic circuits, application-specific integrated circuits (ASICs), appropriate firmware, plug-ins, function cards, etc. When implemented in software, the elements of this application are programs or code segments used to perform the required tasks. Programs or code segments can be stored on a machine-readable medium or transmitted over a transmission medium or communication link via data signals carried on a carrier wave. "Machine-readable medium" can include any medium capable of storing or transmitting information. Examples of machine-readable media include electronic circuits, semiconductor memory devices, ROM, flash memory, erasable ROM (EROM), floppy disks, CD-ROMs, optical disks, hard disks, fiber optic media, radio frequency (RF) links, etc. Code segments can be downloaded via computer networks such as the Internet, intranets, etc.

[0148] It should also be noted that the exemplary embodiments mentioned in this application describe methods or systems based on a series of steps or apparatus. However, this application is not limited to the order of the above steps; that is, the steps can be performed in the order mentioned in the embodiments, or in a different order, or several steps can be performed simultaneously.

[0149] The aspects of this application have been described above with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It should be understood that each block in the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing apparatus to produce a machine such that these instructions, executable via the processor of the computer or other programmable data processing apparatus, enable the implementation of the functions / actions specified in one or more blocks of the flowchart illustrations and / or block diagrams. Such a processor can be, but is not limited to, a general-purpose processor, a special-purpose processor, a special application processor, or a field-programmable logic circuit. It is also understood that each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, can also be implemented by dedicated hardware performing the specified functions or actions, or can be implemented by a combination of dedicated hardware and computer instructions.

[0150] The above provides a detailed description of a method and system for detecting lithium ion concentration in seawater based on multispectral fusion, as provided in this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the embodiments above are merely for the purpose of helping to understand the method and its core ideas. It should be noted that those skilled in the art can make various improvements and modifications to this application without departing from its principles, and these improvements and modifications also fall within the protection scope of this application.

Claims

1. A method for detecting lithium-ion concentration in seawater based on multispectral fusion, characterized in that, include: Water samples were collected from the original seawater, reverse osmosis brine, pretreated liquid before lithium extraction, and tailings liquid after lithium extraction within the same water production cycle. Each water sample is divided into a first detection solution and a second detection solution. A detection reagent that reacts with lithium ions to produce color and fluorescence changes is added to the second detection solution. An AC signal is applied to the second detection solution of each water sample until the impedance value changes measured multiple times are within the preset allowable range. For each water sample, the first and second test solutions were subjected to ultraviolet absorption spectroscopy, visible absorption spectroscopy, and fluorescence spectroscopy to obtain the first and second spectra of each water sample. Based on the differences in absorbance and fluorescence intensity between the first and second spectra of the same water sample, a third spectrum is generated for each water sample. Based on the third spectrum of the pretreated liquid and the third spectrum of the tail liquid, the absorption peak and fluorescence peak corresponding to lithium ions within the water production cycle are determined. According to the absorption peak and the fluorescence peak, the corresponding changes in absorbance and fluorescence intensity are determined from the third spectrum of each water sample. Based on the changes in absorbance and fluorescence intensity, the lithium ion concentration of each water sample is determined using the pre-calibrated correspondence between the lithium ion concentration and the changes in absorbance and fluorescence intensity.

2. The method according to claim 1, characterized in that, The first and second detection solutions for each water sample are subjected to ultraviolet absorption spectroscopy, visible absorption spectroscopy, and fluorescence spectroscopy to obtain the first and second spectra for each water sample, including: When measuring the first and second detection solutions of each water sample, an ultraviolet light source, a visible light source, and a fluorescent excitation light source are used to irradiate the first and second detection solutions respectively, to obtain a first light intensity record corresponding to the first detection solution and a second light intensity record corresponding to the second detection solution. The on / off frequencies of the ultraviolet light source, the visible light source, and the fluorescent excitation light source are different from each other. The first and second light intensity records include the light intensity values ​​that change with measurement time at each measurement wavelength. According to the on / off frequency, the corresponding ultraviolet transmitted light intensity value, visible transmitted light intensity value and fluorescence emitted light intensity value are separated from the first light intensity record and the second light intensity record, respectively. The ultraviolet absorbance is obtained based on the ultraviolet transmitted light intensity value and the corresponding ultraviolet incident light intensity value. The visible absorbance is obtained based on the visible transmitted light intensity value and the corresponding visible incident light intensity value. The fluorescence intensity is taken as the fluorescence intensity value. The ultraviolet absorbance, visible absorbance and fluorescence intensity corresponding to the first light intensity are recorded as the first spectrum. The ultraviolet absorbance, visible absorbance and fluorescence intensity corresponding to the second light intensity are recorded as the second spectrum.

3. The method according to claim 2, characterized in that, The step of irradiating the first detection liquid and the second detection liquid with an ultraviolet light source, a visible light source, and a fluorescence excitation light source, respectively, to obtain a first light intensity record corresponding to the first detection liquid and a second light intensity record corresponding to the second detection liquid includes: When measuring the first detection solution, the ultraviolet light source, the visible light source, and the fluorescent excitation light source are respectively irradiated with the first detection solution at their corresponding on / off frequencies within the same measurement time period; The photodetector receives the ultraviolet transmitted light formed by the first detection liquid under ultraviolet light source irradiation, the visible transmitted light formed under visible light source irradiation, and the fluorescent emitted light formed under fluorescent excitation light source irradiation, and records the corresponding light intensity values ​​according to the measurement time and measurement wavelength to form the first light intensity record. When measuring the second detection solution, the ultraviolet light source, the visible light source, and the fluorescent excitation light source are respectively irradiated with the second detection solution at their corresponding on / off frequencies within the same measurement time period; The photodetector receives the ultraviolet transmitted light formed by the second detection liquid under ultraviolet light source irradiation, the visible transmitted light formed under visible light source irradiation, and the fluorescent emitted light formed under fluorescent excitation light source irradiation, and records the corresponding light intensity values ​​according to the measurement time and measurement wavelength to form the second light intensity record.

4. The method according to claim 1, characterized in that, The step of applying an AC signal to the second detection liquid of each water sample until the impedance value changes measured multiple times are within a preset allowable range, includes: Impedance measurements are performed on the second detection liquid of each water sample after the AC signal is applied at preset time intervals to obtain multiple impedance values ​​within a continuous measurement time. Calculate the absolute value of the difference between the impedance values ​​corresponding to two adjacent measurement times to obtain the change in impedance between adjacent measurements; When the consecutive preset number of adjacent impedance changes are all within the preset allowable range, the application of the AC signal to the second detection liquid is stopped.

5. The method according to claim 1, characterized in that, The process of generating a third spectrum for each water sample based on the differences in absorbance and fluorescence intensity between the first and second spectra of the same water sample includes: At each measurement wavelength, the difference in absorbance and the difference in fluorescence intensity between the second and first spectra of the same water sample are calculated to obtain the absorbance difference and fluorescence intensity difference. The absorbance difference and fluorescence intensity difference corresponding to each measurement wavelength are arranged in order from short wavelength to long wavelength to generate the third spectrum of each water sample.

6. The method according to claim 5, characterized in that, The determination of the absorption and fluorescence peaks corresponding to lithium ions during the water production cycle based on the third spectrum of the pretreated solution and the third spectrum of the tailings solution includes: The wavelength in the third spectrum of the pretreated solution where the absorbance difference is greater than the absorbance difference between the previous and subsequent measurement wavelengths is determined as the candidate absorption wavelength. The fluorescence intensity difference in the third spectrum of the pretreated water sample that is greater than the fluorescence intensity difference between the previous and subsequent measurement wavelengths is determined as the candidate fluorescence wavelength. The peak formed at the candidate absorption wavelength with an absorbance difference greater than that at the same measurement wavelength in the third spectrum of the water sample of the tail liquid is identified as the absorption peak corresponding to lithium ions. The peak formed at the candidate fluorescence wavelength with a fluorescence intensity difference greater than that at the same measurement wavelength in the third spectrum of the water sample of the tail liquid is identified as the fluorescence peak corresponding to lithium ions.

7. The method according to claim 1, characterized in that, Before determining the lithium ion concentration of each water sample based on the absorbance change and the fluorescence intensity change using a pre-calibrated correspondence between lithium ion concentration and absorbance and fluorescence intensity changes, the method further includes: Salt solutions with the same conductivity were prepared for the original seawater, reverse osmosis concentrated brine, pretreatment liquid before lithium extraction, and tailings liquid after lithium extraction. Each salt solution was divided into multiple portions and then different preset amounts of lithium ion solutions of known concentration were added to each portion to obtain multiple lithium standard solutions with different lithium ion concentrations. Calculate the change in absorbance and the change in fluorescence intensity for each of the lithium standard solutions; Based on the lithium ion concentration, absorbance change, and fluorescence intensity change of each lithium standard solution, a corresponding relationship is established with the corresponding water sample.

8. The method according to claim 1, characterized in that, The water samples of the raw seawater, reverse osmosis concentrated brine, pre-treated liquid before lithium extraction, and tailings after lithium extraction were all taken from the same batch of seawater entering the reverse osmosis unit and formed at different treatment stages. The raw seawater sample is collected before the seawater enters the reverse osmosis unit. The reverse osmosis brine sample is collected after the raw seawater has been concentrated in the reverse osmosis unit. The pretreatment solution sample before lithium extraction is collected after the reverse osmosis brine has been pretreated and before it enters the lithium extraction unit. The tailings sample after lithium extraction is collected during the normal effluent stage after the pretreatment solution before lithium extraction has been treated by the lithium extraction unit. The tailings after lithium extraction do not include eluent, regenerated solution, or flushing solution.

9. A seawater lithium-ion concentration detection system based on multispectral fusion, characterized in that, include: The data acquisition module is used to collect water samples of raw seawater, reverse osmosis brine, pretreatment solution before lithium extraction, and tailings solution after lithium extraction within the same water production cycle. The dividing module is used to divide each water sample into a first detection solution and a second detection solution, and to add a detection reagent to the second detection solution that reacts with lithium ions to produce color and fluorescence changes. An AC signal is applied to the second detection solution of each water sample until the impedance value changes measured multiple times are within a preset allowable range and then the process stops. The measurement module is used to perform ultraviolet absorption spectroscopy, visible absorption spectroscopy and fluorescence spectroscopy on the first and second test solutions of each water sample to obtain the first and second spectra of each water sample. The generation module is used to generate a third spectrum for each water sample based on the difference in absorbance and fluorescence intensity between the first and second spectra of the same water sample. Based on the third spectrum of the water sample of the pretreated liquid and the third spectrum of the water sample of the tail liquid, the absorption peak and fluorescence peak corresponding to lithium ions in the water production cycle are determined. The generation module is further configured to determine the corresponding absorbance change and fluorescence intensity change from the third spectrum of each water sample according to the absorption peak and the fluorescence peak, and to determine the lithium ion concentration of each water sample based on the absorbance change and the fluorescence intensity change using a pre-calibrated correspondence between the lithium ion concentration and the absorbance change and fluorescence intensity change.

10. An electronic device, characterized in that, include: Memory, used to store computer programs; A processor, configured to execute the computer program to implement the steps of the seawater lithium ion concentration detection method based on multispectral fusion as described in any one of claims 1 to 8.

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