Online continuous detection system and method for cation exchange capacity of montmorillonite slurry

Abstract

The invention discloses an online continuous detection system and method for cation exchange capacity of montmorillonite slurry. The system is composed of a sampling module, a solid content determination module, a flow path control module, a closed circular reaction unit, a bypass solid-liquid separation module, an online optical detection module, a data processing module, a control module and a cleaning module. The method comprises the following steps: automatically diluting a sample according to the solid content, mixing with a Cu-Trien reagent pre-balanced by carbonate, and fully reacting in a closed circular reaction channel; in the reaction process, low-turbidity clarified liquor is continuously obtained by bypass micro / cross flow filtration and enters a flow-through optical detection pool for real-time absorbance measurement. The system adopts a dual-stability criterion triggering terminal point, the residual Cu-Trien concentration is inversely calculated according to a calibration curve, and CEC is calculated by combining the solid content. According to the scheme, full reaction and non-turbidity interference of an online spectrophotometric method are considered, carbonate errors are reduced, and real-time, accurate and continuous monitoring of CEC in the production process is achieved.

Description

Technical Field

[0001] This invention belongs to the field of mineral analysis and detection technology, specifically a system and method for online continuous detection of cation exchange capacity of montmorillonite slurry. Background Technology

[0002] Montmorillonite is a layered silicate mineral with a unique interlayer cation exchange capacity, widely used in casting, drilling mud, environmental remediation, animal feed additives, and pharmaceutical carriers. Cation exchange capacity (CEC) is a core indicator characterizing the quality of montmorillonite-based bentonite samples, directly determining their adsorption performance, swelling properties, and application value. Therefore, accurate and rapid determination of the CEC of montmorillonite slurry is of great significance for production process control and product quality assurance.

[0003] Currently, the determination of CEC in montmorillonite mainly relies on laboratory methods, including the ammonium acetate method, the methylene blue method, and the copper-triethylenetetramine complex (Cu-Trien) method. While these methods offer high accuracy, they generally suffer from cumbersome operation, long processing times (typically 1-6 hours), and the need for offline operation, making them unsuitable for real-time monitoring on production lines. The Cu-Trien method, in particular, utilizes… The complex is used as an indicator cation. The CEC value is calculated by measuring the concentration of Cu-Trien remaining in the solution after the exchange reaction. This method is relatively simple to operate and has good selectivity, and has the potential to be implemented online.

[0004] With the development of industrial automation, montmorillonite production enterprises urgently need online and continuous CEC detection methods to achieve process control. Flow injection analysis (FIA) technology has been implemented for online detection in many fields, but for the online determination of CEC in montmorillonite slurry, especially how to eliminate turbidity interference while ensuring sufficient ion exchange reaction, how to obtain accurate solid content and mineral composition data online, and how to achieve long-term stable operation of the system, mature technical solutions are still lacking. First, montmorillonite slurry is a high-concentration suspension system, and even after dilution, it still contains a large number of particles. Direct photometric measurements will result in significant errors due to scattering, violating the applicable conditions of the Lambert-Beer law. Effectively eliminating turbidity interference is the primary challenge for online optical detection.

[0005] Secondly, the CEC calculation formula requires the mass of montmorillonite in the sample, but the solid content of the slurry on the production line fluctuates greatly. Traditional methods rely on manual sampling, drying, and weighing. How to obtain accurate solid content data in real time in the online system has not yet been solved. In addition, the ion exchange reaction between Cu-Trien and montmorillonite usually takes 15-30 minutes to reach equilibrium. Traditional FIA systems extend the reaction time by extending the pipeline, but this leads to a large system volume, increased reagent consumption, and easy clogging in the slurry system.

[0006] Meanwhile, because montmorillonite products often contain associated carbonate minerals (such as calcite), which partially dissolve in Cu-Trien solution, the additional reagent consumption leads to higher CEC measurement values. Existing methods lack effective suppression measures. In addition, existing technologies lack system integration solutions, and there is no mature commercial online CEC detection system. There are also technological gaps in the optimized configuration and coordinated control of various functional modules.

[0007] Therefore, it is necessary to develop an online continuous detection system and method for the cation exchange capacity of montmorillonite slurry that can overcome the above-mentioned technical difficulties. Summary of the Invention

[0008] In view of this, in order to solve the problem that existing methods for detecting the cation exchange capacity (CEC) of montmorillonite-based bentonite slurry cannot achieve online continuous measurement, this invention proposes an online continuous detection system and method for the cation exchange capacity of montmorillonite slurry. By online determination of solid content and solid-liquid separation to eliminate turbidity interference, a closed-loop reaction unit is used to ensure sufficient reaction time, and a Cu-Trien reagent formulation pre-equilibrated with carbonates is used to suppress interference, thereby achieving real-time, accurate, and continuous detection of the CEC of montmorillonite slurry.

[0009] According to some embodiments, the present invention adopts the following technical solution: An online continuous detection system for the cation exchange capacity of montmorillonite slurry includes: A sampling module is used to automatically collect montmorillonite slurry samples from the production line; A solid content determination module, connected to the sampling module, is used for online determination of the solid content of the sample; The flow path control module, including a metering pump and a multi-way valve, is fluidly connected to the sampling module and is used to realize sample dilution, Cu-Trien reagent addition and mixing; The reaction unit is fluidly connected to the flow control module to form a closed-loop reaction channel. It is equipped with a circulation pump and a static mixer to enable the sample and Cu-Trien reagent to undergo a full ion exchange reaction through repeated cyclic contact in a solid-liquid coexistence state. The solid-liquid separation module is fluidly connected to the reaction unit via a bypass. It continuously draws out a portion of the mixture from the circulating reaction channel and separates it to obtain a clear liquid. The concentrated liquid is returned to the reaction unit, while the solid-liquid reaction in the reaction unit continues. The online detection module includes a flow-through optical detection cell, which is fluidly connected to the clarified liquid outlet of the solid-liquid separation module, and is used to measure the absorbance of the clarified liquid in real time. The data processing module is connected to the online detection module and the solid content determination module. It calculates the concentration of unconsumed Cu-Trien reagent based on the absorbance and calculates the cation exchange capacity based on the solid content data. The control module is connected to each module and is used to coordinate the automatic cyclic operation of each module; The cleaning module is connected to the closed reaction channel and is used for automatically cleaning the flow path and the detection pool.

[0010] According to some embodiments, the present invention adopts the following technical solution: The solid content determination module uses one of an online density meter, a Coriolis mass flow meter, a turbidity meter, or a near-infrared spectrometer; the solid-liquid separation module uses a side-channel microfiltration device, a cross-flow filtration device, or an online centrifuge, wherein the concentrate is returned to the reaction unit and the clarified liquid enters the online detection module.

[0011] According to some embodiments, the present invention adopts the following technical solution: The reaction unit is a closed-loop reaction circuit, equipped with a static mixer and a circulating pump. Through repeated cyclic contact, the effective reaction time of the sample and Cu-Trien reagent in the reaction unit is 15-30 minutes.

[0012] According to some embodiments, the present invention adopts the following technical solution: The flow path control module is equipped with a Cu-Trien reagent storage tank. The reagent adopts a Cu-trien-calcite formula that is pre-equilibrated with carbonate. The concentration of the Cu-Trien reagent is 0.005-0.02 mol / L, and the pH value is 7.5-8.0.

[0013] According to some embodiments, the present invention adopts the following technical solution: The flow-through optical detection cell has an optical path of 2-5 mm, a measurement wavelength of 570-620 nm, is equipped with an anti-contamination optical window, and is equipped with a temperature control device to stabilize the detection temperature at 25℃.

[0014] According to some embodiments, the present invention adopts the following technical solution: A method for online continuous detection of the cation exchange capacity of montmorillonite slurry, comprising: S1: Automatically collects montmorillonite slurry samples, determines solid content online, and automatically adjusts the dilution factor to dilute the sample based on the solid content; S2: Inject excess Cu-Trien reagent into the continuously flowing diluted sample, the amount of reagent injected being 1.5-2.5 times the theoretical consumption of the sample; S3: Introduce the mixture into a closed reaction channel and allow it to react fully in a solid-liquid coexistence state for 15-30 minutes; S4: During the reaction, a portion of the mixture is continuously extracted from the reaction channel and separated to obtain a clear liquid through a bypass solid-liquid separation device, while the concentrated liquid is returned to the reaction channel. S5: The absorbance of the clarified liquid is measured in real time through a flow-through optical detection cell, and the endpoint determination is triggered when the absorbance reaches a stable value. S6: Calculate the residual Cu-Trien reagent concentration based on the absorbance using a pre-established calibration curve, and calculate the cation exchange capacity using the solid content data; S7: Automatically cleans the flow path and detection cell, then resets and enters the next measurement cycle; The absorbance stability determination adopts a dual-criteria approach, specifically: The rate of change of absorbance is less than 0.5% / min and the standard deviation is less than 0.005 over N consecutive sampling periods, where N≥5; Simultaneously monitor the stability of flow rate or pressure in the flow path. When the flow rate or pressure fluctuation exceeds the set threshold ±10%, the endpoint determination will not be triggered. The formula for calculating the cation exchange capacity is as follows: ;

[0015] Where z = 2 (Cu-Trien valence number). The initial concentration of the reagent is (mol / L). The reagent injection volume (L) is given by Cr, the residual concentration (mol / L), and Vr is the total liquid volume of the reaction system (including the volume of diluted sample and added reagent), in L; m is the dry basis mass of the sample (kg), calculated as m = Vsample × Csolid × Calculate, where Vsample is the sample volume before dilution (L) and Csolid is the solid content (g / L).

[0016] According to some embodiments, the present invention adopts the following technical solution: The closed reaction channel adopts a closed-loop reaction method, specifically: the mixture of sample and reagent is circulated within the reaction unit, and an effective reaction time of 15-30 minutes is achieved by controlling the number of cycles n and the flow rate v. The circulation volume is V_reactor, and the total circulation time t = n × V_reactor / v.

[0017] The Cu-Trien reagent is prepared by mixing triethylenetetramine and copper sulfate at a molar ratio of 1.05-1.10:1, adjusting the pH to 7.5-8.0 with Tris buffer, adding calcium carbonate powder for pre-equilibration, and filtering to obtain Cu-trien-calcite solution.

[0018] According to some embodiments, the present invention adopts the following technical solution: In step S1, the dilution factor is automatically calculated based on the online measured solid content, so that the solid content after dilution is controlled between 0.5-2.0 g / L; The adaptive adjustment method for the reagent injection volume is as follows: For the first measurement, a default excess coefficient of 2.0 is used. Subsequent measurements are performed by calculating the residual concentration Cprev based on the stable absorbance Aprev from the previous measurement. When Cprev / When Cprev / <0.3, increase the reagent injection ratio. When the absorbance is >0.8, reduce the reagent injection ratio to maintain the absorbance within the range of 0.3-0.8.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention provides an online continuous detection method for the cation exchange capacity (CEC) of montmorillonite slurry. This method acquires the solid content of the sample in real time through a solid content determination module, providing accurate quality data for CEC calculation. A solid-liquid separation module removes suspended particles, eliminating interference from turbidity in optical measurements. A closed-loop reaction unit enables a sufficient reaction time of 15-30 minutes within a limited volume. A Cu-trien-calcite reagent formulation pre-equilibrated with carbonates significantly reduces systematic errors caused by carbonate dissolution. Finally, a dual stability criterion ensures measurement reliability, enabling online, continuous, and accurate detection of the CEC of montmorillonite slurry.

[0020] In terms of technical implementation, this invention provides two methods: First, it employs solid-liquid separation to eliminate turbidity interference, obtaining a clear liquid that conforms to the Lambert-Beer law for photometric measurement, ensuring measurement accuracy. Second, it designs a closed-loop circulating reaction unit, achieving the required reaction time of 15-30 minutes through repeated circulation within a small-volume reactor, thus resolving the contradiction between reaction time and system volume in traditional FIA systems. Simultaneously, it introduces dual stability criteria (absorbance stability + flow / pressure stability) to avoid misjudgments in case of flow path abnormalities, improving the system's reliability and practicality. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the online continuous detection system for cation exchange capacity of montmorillonite slurry according to the present invention; Figure 2This is a schematic flowchart of the online continuous detection method for cation exchange capacity of montmorillonite slurry according to the present invention. Detailed Implementation

[0022] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application.

[0023] It should be understood that although the terms first, second, third, etc., may be used in this application to describe various information, such information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, without departing from the scope of this application, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to determination."

[0024] Terminology Explanation: Calibration curve: Establishing a linear equation for the quantitative relationship between absorbance A and Cu-Trien concentration c. It is used to back-calculate the measured absorbance into the reagent concentration.

[0025] Closed-loop reaction: A reaction method in which the sample and reagent are repeatedly contacted by a circulating pump within a fixed-volume reaction unit, extending the effective reaction time without increasing the system volume.

[0026] Dual stability criterion: A criterion method that simultaneously monitors absorbance stability and flow path flow / pressure stability to avoid erroneous triggering of the measurement endpoint when the system is abnormal.

[0027] To achieve the above objectives, the first aspect of the present invention provides an online continuous detection system for the cation exchange capacity of montmorillonite slurry, such as... Figure 1 As shown, the system includes a sampling module, a solid content determination module, a flow path control module, a solid-liquid separation module, a reaction unit, an online detection module, a data processing module, a control module, and a cleaning module connected in sequence.

[0028] The sampling module periodically extracts samples from the slurry pipeline or storage tank of the production line. The sampling point is set at a location where the flow is fully mixed. The sampling frequency is set according to process requirements, and it is recommended to do so once every 30 minutes to 2 hours.

[0029] Furthermore, the sampling pump is preferably a peristaltic pump or a diaphragm pump with an adjustable flow rate of 10-100 mL / min, and is equipped with a 40-60 mesh sieve for pre-filtering large particulate impurities.

[0030] The solid content determination module acquires the solid content of the sample in real time, providing a basis for the dry basis mass m of the sample in the CEC calculation.

[0031] Furthermore, the solid content can be determined using one of the following methods: (1) Online density meter: measures the density ρ of slurry, and converts it through the linear relationship between density and solid content, with an accuracy of ±0.5%; (2) Coriolis mass flow meter: measures mass flow rate and volumetric flow rate to calculate density with an accuracy of ±1%, and provides flow data; (3) Turbidity meter: The solid content is converted from the measured turbidity value through the calibration curve, with an accuracy of ±2%; (4) Near-infrared spectrometer: Predicts using characteristic absorption through a chemometric model with an accuracy of ±1.5%.

[0032] Specifically, an online density meter is preferred, with a measurement range of 800-1500 kg / m³ and a response time of <5 seconds.

[0033] The flow path control module includes a peristaltic pump, a multi-channel switching valve, an online mixer, and a reagent storage tank, enabling automatic sample dilution, precise addition of Cu-Trien reagent, and thorough mixing of the two.

[0034] Furthermore, based on the measured solid content Csolid (g / L), the data processing module automatically calculates the dilution factor n = Csolid / Ctarget, where Ctarget is the target solid content, preferably 1.0 g / L (range 0.5-2.0 g / L). The control module then adjusts the flow rate ratio of the sample pump and the dilution water pump, Qsample:Qwater = 1:(n-1), to achieve automatic sample dilution and ensure that the solid content remains stable within the target range after dilution.

[0035] Furthermore, the Cu-Trien reagent uses a Cu-trien-calcite formulation pre-equilibrated with carbonate, prepared by weighing copper sulfate... The solution is mixed with triethylenetetramine (trien) at a molar ratio of Cu:trien = 1:1.05, dissolved in deionized water, and the pH is adjusted to 7.5-8.0 with Tris buffer. After bringing the volume to a final depth, calcium carbonate powder (0.5 g / L) is added, and the mixture is stirred and equilibrated for 24 hours. The solution is then filtered (0.45 μm) to obtain the working solution with a concentration of 0.005-0.02 mol / L. This formulation effectively suppresses systematic errors caused by the dissolution of carbonates in the sample.

[0036] Specifically, the reagent injection volume is calculated based on 1.5-2.5 times the theoretical sample consumption, and can be adaptively adjusted based on the stable absorbance measured previously: if the ratio of residual concentration to initial concentration Cr / <0.3, increase the excess coefficient; if Cr / >0.8, reduce the excess coefficient to keep the absorbance within the range of 0.3-0.8, and ensure that the measurement falls within the linear range of the calibration curve.

[0037] The reaction unit forms a closed-loop reaction circuit. The reactor volume is 50-200 mL, preferably 100 mL, and the material is 316L stainless steel or PTFE lined. The reaction circuit is equipped with a circulation pump (flow rate 0.2-1.0 L / min, preferably 0.5 L / min) and static mixers (6-12 mixing units). An effective reaction time of 15-30 minutes is achieved by controlling the number of circulations and the flow rate. The reaction temperature is stabilized at 25°C using a temperature control device.

[0038] The solid-liquid separation module uses a bypass sampling method, continuously extracting a portion of the mixed liquid from the reaction loop for solid-liquid separation while the ion exchange reaction is taking place in the reaction unit.

[0039] The function of this module is to: set a diversion point on the circulation pipeline of the reaction loop, and control the bypass extraction flow rate through a metering pump or diversion valve, which is usually 5-20% of the reaction loop circulation flow rate; the solid-liquid separation and the ion exchange reaction in the reaction unit are carried out synchronously and do not interfere with each other; the concentrated liquid after separation is returned to the inlet of the reaction loop through the reflux pipeline to ensure that the reactants are not lost and the reaction is complete; this design obtains a clear liquid without turbidity interference for photometric detection while maintaining the solid-liquid coexistence state in the reaction unit and the continuous ion exchange.

[0040] Specific connection method: A bypass point is set on the circulation pipeline of the reaction loop, and the bypass extraction flow rate is controlled by a metering pump or a bypass valve (usually 5-20% of the reaction loop circulation flow rate). After the extracted mixture is separated by a solid-liquid separation device, the clarified liquid enters the online detection module, and the concentrated liquid returns to the reaction loop inlet through a return pipeline. This bypass design ensures that the set solid-liquid ratio and reaction conditions are always maintained in the reaction loop, while obtaining a clear liquid without turbidity interference for detection.

[0041] Solid-liquid separation devices can be implemented using one of the following methods: (1) Side-path microfiltration device: The filter membrane material is polyethersulfone (PES), polyvinylidene fluoride (PVDF) or ceramic membrane, with a pore size of 0.2-0.45μm, preferably 0.22μm, and a transmembrane pressure difference of 0.5-2.0bar, preferably 1.0bar; (2) Cross-flow filtration device: pore size 0.2-0.45μm, concentrate flows along the membrane surface, reducing membrane fouling, suitable for long-term continuous operation; (3) Online centrifuge: speed 3000-6000rpm, good separation effect but complex equipment.

[0042] The turbidity of the clarified liquid after separation should be less than 5 NTU, preferably less than 3 NTU.

[0043] The online detection module includes a flow-through optical detection cell, a light source, a monochromator, and a photodetector. The flow-through optical detection cell has an optical path of 2-5 mm (preferably 3 mm), a measurement wavelength of 570-620 nm (preferably 590 nm, corresponding to the maximum absorption of Cu-Trien), and is equipped with a contamination-resistant optical window (sapphire or quartz). The temperature is controlled at 25±0.5℃.

[0044] Furthermore, the absorbance measurement range is 0-2.0 AU, with an accuracy of ±0.005 AU.

[0045] The data processing module calculates the residual Cu-Trien concentration and CEC based on the absorbance. First, a calibration curve is established: a series of Cu-Trien standard solutions (concentration 0-0.002 mol / L) are prepared, absorbance is measured, and the least squares method is used for fitting. The requirement is R² ≥ 0.999. The calibration curve is updated every 24 hours or every 50 samples.

[0046] Furthermore, during online measurement, the residual concentration is calculated back from the measured absorbance A: .

[0047] CEC calculation formula:

[0048] Where: z = 2 (Cu-Trien valence number) The initial concentration of the reagent is (mol / L). The volume (L) of reagent injected. Residual concentration (mol / L) Let m be the total liquid volume of the reaction system (L), and m be the dry weight of the sample (kg). The formula is: m = Vsample × Csolid × ... Calculate, where Vsample is the sample volume (L) and Csolid is the solid content (g / L).

[0049] The control module coordinates the operation of each functional module to achieve automatic measurement cycle. The endpoint of the reaction is determined by dual stability criteria: (1) the rate of change of absorbance is <0.5% / min and the standard deviation is <0.005 within N consecutive sampling cycles (N≥5); (2) the flow rate or pressure fluctuation is within ±10% of the set value. The endpoint determination is triggered when both criteria are met, and CEC calculation is entered. If the flow rate or pressure is abnormal, the endpoint determination will not be triggered even if the absorbance is "stable" to avoid misjudgment.

[0050] The cleaning module includes a cleaning solution storage tank (dilute acid, deionized water, and surfactant solution) and a transfer pump, with an independent cleaning branch. After each measurement, the system sequentially cleans with dilute acid, rinses with deionized water, cleans with surfactant, and finally rinses. Cleaning is considered complete when the absorbance of the detection cell returns to baseline ±0.005 and the flow path pressure returns to normal.

[0051] In this invention, the system's workflow includes: a sampling module collecting montmorillonite slurry samples from the production line; the samples flowing through a solids content determination module for online solids content measurement; based on the solids content value, a data processing module automatically calculating the dilution factor; and a control module adjusting the flow ratio of the sample pump and the dilution water pump to dilute the sample; the diluted sample is then mixed with Cu-Trien reagent in a flow path control module before entering the reaction unit. The mixture circulates in a closed-loop reaction circuit for 15-30 minutes in a solid-liquid coexistence state. During the reaction, a portion of the mixture is continuously extracted from the circulating reaction channel (5-20% of the circulating flow rate) through a bypass solid-liquid separation module to remove suspended particles and obtain a clarified liquid. The concentrated liquid is simultaneously returned to the reaction circuit to ensure that the solid-liquid reaction continues in the reaction channel without material loss. The clarified liquid enters the online detection module. The absorbance of the clarified liquid after the reaction is measured by the online detection module. When the absorbance meets the dual stability criteria, the endpoint determination is triggered. The data processing module calculates the residual Cu-Trien concentration based on the absorbance using the calibration curve and calculates the cation exchange capacity by combining the solid content data. After the measurement is completed, the cleaning module automatically cleans the flow path and the detection cell. After the system is reset, it enters the next measurement cycle.

[0052] A second aspect of this invention provides an online continuous detection method for the cation exchange capacity of montmorillonite slurry, wherein the method is implemented in the system, such as... Figure 2 As shown, the method includes the following steps: S1: Automatically collects montmorillonite slurry samples, determines solid content online, and automatically adjusts the dilution factor to dilute the sample based on the solid content; S2: Inject excess Cu-Trien reagent (pre-equilibrated with carbonate, injection amount is 1.5-2.5 times the theoretical consumption) into the continuously flowing diluted sample. S3: Introduce the mixture into a closed-loop reaction channel and allow it to react fully in a cyclical manner under solid-liquid coexistence conditions for 15-30 minutes. S4: During the reaction, a portion of the mixed liquid is continuously extracted from the circulating reaction channel and separated to obtain a clear liquid through a bypass solid-liquid separation device. The concentrated liquid is simultaneously returned to the reaction channel to keep the solid-liquid reaction in the reaction channel running continuously. S5: The absorbance of the clarified liquid after the reaction is measured in real time through a flow-through optical detection cell. When the absorbance reaches a stable value, the endpoint determination is triggered. S6: Calculate the residual Cu-Trien reagent concentration based on the absorbance using a pre-established calibration curve, and calculate the cation exchange capacity using the solid content data; S7: Automatically cleans the flow path and detection cell, then resets and enters the next measurement cycle.

[0053] In a specific implementation, in step S1, the dilution factor is automatically calculated based on the solid content measured online, so that the solid content after dilution is controlled between 0.5-2.0 g / L.

[0054] In a specific implementation, the Cu-Trien reagent in step S2 is formulated with pre-equilibrium carbonate, and the amount of reagent injected is 1.5-2.5 times the theoretical consumption of the sample.

[0055] In a specific implementation, in step S2, a default excess coefficient of 2.0 is used for the first measurement. Subsequently, the injection ratio of Cu-Trien reagent is automatically adjusted according to the stable absorbance of the previous measurement to maintain the absorbance in the range of 0.3-0.8, so as to ensure that the measurement is within the linear range of the calibration curve.

[0056] In a specific implementation, step S3 employs a closed-loop reaction method, in which the mixture of sample and reagent is circulated within the reaction unit, and an effective reaction time of 15-30 minutes is achieved by controlling the number of cycles and the flow rate.

[0057] In a specific embodiment, the reaction temperature in step S3 is 25°C.

[0058] In a specific implementation, the solid-liquid separation in step S4 uses a microfiltration device or a cross-flow filtration device (membrane pore size 0.2-0.45 μm), or an online centrifuge (speed 3000-6000 rpm).

[0059] In a specific implementation, the stability criterion for step S5 is: the rate of change of absorbance is less than 0.5% / min and the standard deviation is less than 0.005 within N consecutive sampling periods, where N≥5.

[0060] In a specific implementation, the stability criterion is used in conjunction with the flow path flow stability or pressure stability, and the endpoint determination is not triggered when the flow or pressure fluctuation exceeds the set value ±10%.

[0061] In a specific implementation, step S6 uses the following formula to calculate the cation exchange capacity:

[0062] The meanings of each parameter are the same as those defined in the first aspect of the system description.

[0063] In a specific embodiment, the residual reagent concentration Cr is obtained by converting the stable absorbance measured in step S5 using a pre-established calibration curve: Where A is absorbance and k is the slope of the calibration curve. This is the intercept.

[0064] The present invention will be described in detail below through embodiments, but the scope of protection of the present invention is not limited thereto.

[0065] The following examples are as follows Figures 1-2 The system shown is implemented in an online continuous detection system for the cation exchange capacity of montmorillonite slurry. The system includes: a sampling module, which uses a peristaltic pump with a flow rate of 50 mL / min and is equipped with a 50-mesh sieve. The solid content determination module uses an online density meter with a measurement range of 800-1500 kg / m³ and an accuracy of ±0.5%. The flow path control module includes a sample pump, a dilution water pump (flow rate adjustable from 0-100 mL / min), a reagent pump, a multi-channel switching valve, and an online mixer, and is equipped with a Cu-Trien reagent storage tank (Cu-trien-calcite formulation, concentration 0.01 mol / L, pH 7.8). The reaction unit adopts a closed-loop reaction circuit, with a reactor volume of 100mL, made of 316L stainless steel, a circulation pump flow rate of 0.5L / min, and is equipped with a static mixer with 8 mixing units and a temperature control device (25℃). The solid-liquid separation module uses a bypass microfiltration device, a polyethersulfone membrane with a pore size of 0.22 μm and a transmembrane pressure difference of 1.0 bar. The online detection module includes a flow-through optical detection cell (3mm optical path, quartz window), an LED light source (590nm), an absorbance measurement range of 0-2.0AU, and an accuracy of ±0.005AU. The data processing module uses an industrial computer to store the calibration curve (A=615.2×c+0.002, R²=0.9995). The control module uses a PLC controller; The cleaning module is equipped with a cleaning solution storage tank (0.05mol / L HCl, deionized water, 0.1% Triton X-100) and a transfer pump. Example 1

[0066] (1) The sampling module collects montmorillonite slurry samples from the production line and obtains the solid content using an online density meter. The control module automatically adjusts the flow ratio of the sample pump and the dilution water pump according to the target solid content range to complete the dilution.

[0067] (2) Inject the Cu-trien-calcite reagent through a reagent pump and mix it thoroughly with the diluted sample in an online mixer.

[0068] (3) The mixture is fed into a closed-loop reaction loop. During the circulation reaction, a portion of the mixture is separated into solid and liquid by a bypass microfiltration device to obtain a low-turbidity clear liquid (the concentrate is returned to the reaction loop).

[0069] (4) The clarified liquid continuously enters the flow-through optical detection cell, the circulation pump maintains the set flow rate, and the reaction temperature is stable at 25℃; when the absorbance meets the dual stability criteria (absorbance stability + flow / pressure stability), the endpoint determination is triggered.

[0070] (5) The data processing module calculates the residual reagent concentration based on the stable absorbance and calibration curve, and generates CEC results by combining the solid content.

[0071] (6) The cleaning module sequentially completes pickling, rinsing and surfactant cleaning. After the absorbance of the detection cell and the flow path pressure are restored to the baseline, the system is reset and enters the next cycle. Example 2

[0072] (1) The sampling module collects slurry samples and obtains the solid content through a Coriolis mass flow meter; the control module automatically completes the dilution according to the target solid content range.

[0073] (2) Based on the stable absorbance measured previously, the reagent excess coefficient is adaptively adjusted, and Cu-trien-calcite reagent is injected and mixed online with the diluted sample.

[0074] (3) The mixture enters the closed-loop reaction loop, and cross-flow filtration is used as a bypass solid-liquid separation unit to continuously obtain clear liquid for detection, while the concentrated liquid is returned to the reaction loop.

[0075] (4) The reaction is carried out under the set circulation flow rate and temperature (25℃) conditions. The endpoint determination is triggered when the absorbance meets the dual stability criteria.

[0076] (5) The data processing module calculates the residual reagent concentration based on the stable absorbance and calibration curve, and outputs the CEC results in combination with the solid content.

[0077] (6) Complete the cleaning and reset according to the preset program. Example 3

[0078] (1) The system is set to automatic cyclic operation mode, and the sampling period is set to 30 minutes for long-term continuous operation.

[0079] (2) The solid content determination module monitors the solid content fluctuation of the production line in real time; the control module dynamically adjusts the flow ratio of the sample pump and the dilution water pump according to the measured value, so that the solid content after dilution is stable within the target range.

[0080] (3) The flow path control module adaptively adjusts the amount of Cu-trien-calcite reagent injected based on the previous stable absorbance, so that the online measurement remains in the linear range of the calibration curve.

[0081] (4) Each measurement is completed in a closed-loop reaction loop, with continuous solid-liquid separation via bypass microfiltration; after the dual stability criteria are met, the data processing module generates the CEC result.

[0082] (5) The cleaning module automatically executes the cleaning program after each measurement and regularly backflushes and maintains the microfiltration membrane to ensure the stability and flux recovery of long-term continuous operation.

[0083] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. An online continuous detection system for the cation exchange capacity of montmorillonite slurry, characterized in that, include: A sampling module is used to automatically collect montmorillonite slurry samples from the production line; A solid content determination module, connected to the sampling module, is used for online determination of the solid content of the sample; The flow path control module, including a metering pump and a multi-way valve, is fluidly connected to the sampling module and is used to realize sample dilution, Cu-Trien reagent addition and mixing; The reaction unit is fluidly connected to the flow control module to form a closed-loop reaction channel. It is equipped with a circulation pump and a static mixer to enable the sample and Cu-Trien reagent to fully carry out ion exchange reaction through repeated cyclic contact in a solid-liquid coexistence state. The solid-liquid separation module is fluidly connected to the circulating reaction channel of the reaction unit in a bypass manner. During the reaction, a portion of the mixture is continuously extracted from the circulating channel and separated to obtain a clear liquid. The concentrated liquid is returned to the reaction unit, while the solid-liquid reaction in the reaction unit continues. The online detection module includes a flow-through optical detection cell, which is fluidly connected to the clarified liquid outlet of the solid-liquid separation module, and is used to measure the absorbance of the clarified liquid in real time. The data processing module is connected to the online detection module and the solid content determination module. It calculates the concentration of unconsumed Cu-Trien reagent based on the absorbance and calculates the cation exchange capacity based on the solid content data. The control module is connected to each module and is used to coordinate the automatic cyclic operation of each module; The cleaning module is connected to the closed reaction channel and is used for automatically cleaning the flow path and the detection pool.

2. The system according to claim 1, characterized in that: The solid content determination module uses one of an online densitometer, a Coriolis mass flow meter, a turbidity meter, or a near-infrared spectrometer. The solid-liquid separation module employs one of a side-channel microfiltration device, a cross-flow filtration device, or an online centrifuge, wherein the concentrate is returned to the reaction unit and the clarified liquid enters the online detection module.

3. The system according to claim 1, characterized in that, The reaction unit is a closed-loop reaction circuit, equipped with a static mixer and a circulating pump. Through repeated cyclic contact, the effective reaction time of the sample and Cu-Trien reagent in the reaction unit is 15-30 minutes.

4. The system according to claim 1, characterized in that, The flow path control module is equipped with a Cu-Trien reagent storage tank. The reagent adopts a Cu-trien-calcite formula that is pre-equilibrated with carbonate. The concentration of the Cu-Trien reagent is 0.005-0.02 mol / L, and the pH value is 7.5-8.

0.

5. The system according to claim 1, characterized in that, The flow-through optical detection cell has an optical path of 2-5 mm, a measurement wavelength of 570-620 nm, is equipped with an anti-contamination optical window, and is equipped with a temperature control device to stabilize the detection temperature at 25℃.

6. A method for online continuous detection of the cation exchange capacity of montmorillonite slurry, characterized in that, Includes the following iterative steps: S1: Automatically collects montmorillonite slurry samples, determines solid content online, and automatically adjusts the dilution factor to dilute the sample based on the solid content; S2: Inject excess Cu-Trien reagent into the continuously flowing diluted sample, the amount of reagent injected being 1.5-2.5 times the theoretical consumption of the sample; S3: Introduce the mixture into a closed-loop reaction channel and allow it to react fully in a cyclical manner under solid-liquid coexistence conditions for 15-30 minutes. S4: During the reaction, a portion of the mixed liquid is continuously extracted from the circulating reaction channel and separated to obtain a clear liquid through a bypass solid-liquid separation device. The concentrated liquid is simultaneously returned to the reaction channel to keep the solid-liquid reaction in the reaction channel running continuously. S5: The absorbance of the clarified liquid is measured in real time through a flow-through optical detection cell, and the endpoint determination is triggered when the absorbance reaches a stable value. S6: Calculate the residual Cu-Trien reagent concentration based on the absorbance using a pre-established calibration curve, and calculate the cation exchange capacity using the solid content data; S7: Automatically cleans the flow path and detection cell, then resets and enters the next measurement cycle.

7. The method according to claim 6, characterized in that: In step S1, the dilution factor is automatically calculated based on the online measured solid content, so that the solid content after dilution is controlled between 0.5-2.0 g / L; In step S2, the default excess factor of 2.0 is used for the first measurement. Subsequently, the injection ratio of Cu-Trien reagent is automatically adjusted according to the stable absorbance of the previous measurement to keep the absorbance in the range of 0.3-0.8, so as to ensure that the measurement is within the linear range of the calibration curve.

8. The method according to claim 6, characterized in that, In step S4, a closed-loop reaction method is adopted, in which the mixture of sample and reagent is circulated within the reaction unit. An effective reaction time of 15-30 minutes is achieved by controlling the number of cycles and the flow rate.

9. The method according to claim 6, characterized in that, The stability criterion for step S5 is: the rate of change of absorbance is less than 0.5% / min and the standard deviation is less than 0.005 within N consecutive sampling periods, where N≥5; the stability criterion is used in conjunction with the flow path flow stability or pressure stability, and the endpoint determination is not triggered when the flow rate or pressure fluctuation exceeds the set threshold.

10. The method according to claim 6, characterized in that, Step S6 uses the following formula to calculate the cation exchange capacity: ； in: z is the valence of the Cu-Trien complex, z=2; The initial concentration of Cu-Trien reagent is expressed in mol / L. The volume of reagent injected is in liters (L). The residual reagent concentration is expressed in mol / L and is obtained by converting the stable absorbance measured in step S5 using a pre-established calibration curve. The total liquid volume of the reaction system is expressed in liters (L). m is the dry weight of the sample, in kg, which is calculated from the sample volume and the solid content measured in step S1.

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