A method and system for online detection of heavy metal leaching toxicity of phosphogypsum

Abstract

The application discloses a kind of phosphogypsum heavy metal leaching toxicity online detection method and system, belong to industrial solid waste environmental monitoring technical field.The method includes step one, to phosphogypsum is quantitatively sampled, and calculates moisture content correction coefficient;Step two, phosphogypsum sample is screened and ground, and its particle size uniformity is calculated and ensured to meet the demand;Step three, the leaching reaction efficiency of each phosphogypsum sample is calculated respectively;Step four, phosphogypsum sample is subjected to negative pressure suction filtration, and filter membrane blockage state is monitored in real time;Step five, phosphogypsum sample filtrate is subjected to heavy metal detection, and the heavy metal concentration of sample after temperature compensation and electrode drift correction is calculated;Step six, clean full flow path, and determine whether cleaning is qualified, whether there is cross contamination.Adapt to the characteristics of phosphogypsum material, and the leaching efficiency deviation is controlled within 3%, completely solve the long-term operation precision attenuation pain point of relevant system, meet the requirement of industrial field continuous online monitoring.

Description

Technical Field

[0001] This invention relates to an online detection method and system for heavy metal leaching toxicity of phosphogypsum, belonging to the field of industrial solid waste environmental monitoring technology. Background Technology

[0002] Phosphogypsum, a major byproduct of wet-process phosphoric acid production, is a key source of soil and groundwater pollution due to the easy leaching and migration of its complexed heavy metals under natural leaching conditions. Current control requirements stipulate that GB5085.3-2007, "Identification Standard for Hazardous Waste: Leaching Toxicity Identification," is the mandatory testing standard. However, industry testing methods still primarily rely on offline laboratory testing, indicating a fundamental technical deficiency.

[0003] The existing offline testing process relies on manual sampling, long-distance transportation, manual pretreatment, oscillation leaching, and atomic absorption spectrophotometry. The entire process takes more than 12 hours and cannot achieve real-time risk warning for the stockpile. When manually adjusting the liquid-solid ratio, leaching temperature, and oscillation frequency, human error can reach more than 8%, resulting in poor parallelism of the test data and lacking value for law enforcement traceability.

[0004] Currently available methods for detecting the heavy metal leaching toxicity of phosphogypsum solid waste have the following shortcomings: First, it cannot be adapted to the material characteristics of phosphogypsum, which is highly crystalline and prone to clumping. Long-term operation can easily cause pipeline blockage and filter membrane damage, ultimately leading to insufficient leaching.

[0005] Second, fluctuations in ambient temperature and material moisture content directly lead to deviations in leaching efficiency, and the detection accuracy cannot meet the requirements of online monitoring.

[0006] Third, there is no data redundancy in a single test, and outliers cannot be corrected.

[0007] In summary, existing methods for detecting the leaching toxicity of heavy metals cannot meet the requirements for online and continuous detection of phosphogypsum, nor can they solve the three core technical pain points of material compatibility, parameter accuracy, and data reliability. There is no mature integrated online detection technology solution. Summary of the Invention

[0008] To address the aforementioned technical problems, this invention provides an online detection method and system for the heavy metal leaching toxicity of phosphogypsum.

[0009] This invention is achieved through the following technical solution: An online detection method for heavy metal leaching toxicity of phosphogypsum includes the following steps: Step 1: Quantitatively sample phosphogypsum and collect the measured moisture content of the phosphogypsum samples. Then based on the measured moisture content Calculate the moisture content correction factor ; Step 2: Sieve and grind the phosphogypsum sample, calculate and ensure its particle size uniformity. Meet the needs; Step 3: Divide the phosphogypsum sample into multiple equal portions, and control the leaching conditions of all equal portions of phosphogypsum sample according to national standards. Then, carry out the leaching reaction of all equal portions of phosphogypsum sample simultaneously and in parallel, and calculate the leaching reaction efficiency of each phosphogypsum sample. ; Step 4: Simultaneously and in parallel perform negative pressure filtration on all phosphogypsum samples that have completed the leaching reaction, then monitor the filter membrane clogging status in real time, and switch to the backup filter membrane when the filter membrane becomes clogged. Step 5: Simultaneously and in parallel, perform heavy metal detection on the filtrate of all phosphogypsum samples using anodic stripping voltammetry, and calculate the temperature-compensated heavy metal concentration in the filtrate of each phosphogypsum sample. And perform data cross-validation, and then use electrode drift correction coefficients. heavy metal concentration in the sample Make corrections; Step 6: Perform a stepwise, quantitative cleaning of the entire flow path using deionized water and dilute nitric acid, and calculate the cleaning saturation. To determine whether the cleaning is up to standard and whether there is any cross-contamination.

[0010] In step one, the moisture content correction coefficient is calculated using the following formula. : In the formula, This is a correction factor with a value of 0.015; The standard moisture content is 5%.

[0011] The particle size uniformity of the phosphogypsum sample after sieving and grinding in step two. The calculation is performed using the following formula: , In the formula, The maximum particle size of the phosphogypsum sample is [missing information]. The minimum particle size of the phosphogypsum sample is given. The average particle size; when When the particle size uniformity meets the requirements, it indicates that the particle size uniformity meets the requirements.

[0012] In step three, the temperature of all equal-amount phosphogypsum samples was controlled at 25°C and the pH value at 5-6, in accordance with national standards, and the volume of extractant added was also controlled. Ensure that the liquid-to-solid ratio of all equally aliquoted phosphogypsum samples matches the standard liquid-to-solid ratio. Consistent.

[0013] The volume of the extractant added The calculation is performed using the following formula: In the formula, the volume of the extractant added is... The unit is mL; Mass of a single phosphogypsum sample, in grams; standard liquid-to-solid ratio ; Leaching reaction efficiency of each phosphogypsum sample The calculation is performed using the following formula: , In the formula, This represents the real-time leaching concentration. To balance the leaching concentration, all units are mg / L; when When the leaching is complete, it indicates that the leaching is complete and meets the testing requirements.

[0014] In step four, the following formula is used to determine whether the filter membrane is clogged: In the formula, The pressure difference of the filter membrane. For real-time filtration pressure, This is the initial filtration pressure; when When this occurs, it indicates that the filter membrane is clogged.

[0015] In step five, the heavy metal concentration of the sample is calculated using the following formula. : In the formula, The peak current of the sample. For blank baseline current, The concentration of the standard solution is... The peak current of the standard liquid is... This is the temperature compensation coefficient; The electrode drift correction factor is calculated using the following formula. : In the formula, The initial standard solution current, For real-time standard solution current, Runtime, in hours; Heavy metal concentration in the sample after electrode drift correction for: .

[0016] In step six, the cleaning saturation is calculated using the following formula. : , In the formula, To reduce the concentration of heavy metals in the cleaning wastewater, This represents the highest heavy metal concentration in the sample. when When the time is right, it indicates that the cleaning is qualified and there is no cross-contamination.

[0017] An online detection system for heavy metal leaching toxicity of phosphogypsum includes: The quantitative sampling unit is used to quantitatively sample phosphogypsum and collect the measured moisture content of the phosphogypsum sample. Transmitted to the PLC controller for moisture content correction factor calculate; A two-stage pretreatment unit is used to perform primary vibration sieving and secondary shear grinding on the phosphogypsum samples collected by the quantitative sampling unit; The leaching reaction unit has multiple sets of parallel reaction vessels built in. Each set of parallel reaction vessels is used one by one to control the leaching conditions of multiple phosphogypsum samples obtained after being processed by the two-stage pretreatment unit and divided into equal portions, so as to achieve synchronous and parallel leaching reaction. The solid-liquid separation unit is used to simultaneously and in parallel perform negative pressure filtration on all phosphogypsum samples that have completed the leaching reaction, and transmits the real-time filtration pressure to the PLC controller for judging the filter membrane blockage status. The heavy metal detection unit is equipped with multiple independent three-electrode systems, and the three-electrode system has a built-in temperature compensation module, which is used to simultaneously and in parallel perform heavy metal detection on the filtrate of all phosphogypsum samples using anodic stripping voltammetry. An automatic cleaning unit is used for graded and quantitative cleaning of the entire flow path; The PLC controller is connected to the quantitative sampling unit, the two-stage pretreatment unit, the leaching reaction unit, the solid-liquid separation unit, and the heavy metal detection unit, and executes the online detection method for heavy metal leaching toxicity of phosphogypsum.

[0018] The system adopts a sequential batch continuous operation mode with a detection cycle of ≤60 minutes. It automatically performs blank calibration, standard solution calibration, and parallel sample calibration at midnight every day. If the calibration fails, the process is automatically locked and an alarm is triggered.

[0019] The beneficial effects of this invention are as follows: 1. Homogenize the phosphogypsum sample and introduce a moisture content correction factor. Volume of extractant added The method was modified to address the issues of phosphogypsum agglomeration and moisture content fluctuations leading to leaching efficiency deviations and reduced detection accuracy. The test data strictly conforms to the national standard laboratory method, with relative deviations controlled within 3%, significantly improving detection accuracy. This also allows the method to be adapted to the material characteristics of phosphogypsum, which is highly crystalline and prone to agglomeration, ensuring long-term operation, avoiding pipeline blockage and filter membrane damage, and guaranteeing sufficient leaching.

[0020] 2. A multi-channel parallel detection method was created to enable cross-validation of detection data, facilitating the removal or correction of outliers. Temperature compensation and electrode drift correction were also introduced to correct for heavy metal concentration in the samples. This significantly improves detection accuracy, while also incorporating graded and quantitative cleaning throughout the entire flow path, and monitoring cleaning saturation. The calculations determine whether the cleaning is qualified and whether there is cross-contamination, which completely solves the pain point of long-term operation accuracy decay of related systems and greatly extends the maintenance-free cycle.

[0021] 3. The system provided eliminates manual operation, realizing unmanned operation of the entire process from sampling, pretreatment, leaching, solid-liquid separation to quantitative detection of heavy metals. The single detection cycle is controllable, meeting the requirements of continuous online monitoring in industrial sites. Detailed Implementation

[0022] The technical solution of the present invention is further described below, but the scope of protection is not limited to what is described.

[0023] Example 1 The present invention provides an online detection method for heavy metal leaching toxicity of phosphogypsum, comprising the following steps: Step 1: Quantitatively sample phosphogypsum and collect the measured moisture content of the phosphogypsum samples. Then based on the measured moisture content Calculate the moisture content correction factor ; Step 2: Sieve and grind the phosphogypsum sample, calculate and ensure its particle size uniformity. Meet the needs; Step 3: Divide the phosphogypsum sample into multiple equal portions, and control the leaching conditions of all equal portions of phosphogypsum sample according to national standards. Then, carry out the leaching reaction of all equal portions of phosphogypsum sample simultaneously and in parallel, and calculate the leaching reaction efficiency of each phosphogypsum sample. ; Step 4: Simultaneously and in parallel perform negative pressure filtration on all phosphogypsum samples that have completed the leaching reaction, then monitor the filter membrane clogging status in real time, and switch to the backup filter membrane when the filter membrane becomes clogged. Step 5: Simultaneously and in parallel, perform heavy metal detection on the filtrate of all phosphogypsum samples using anodic stripping voltammetry, and calculate the temperature-compensated heavy metal concentration in the filtrate of each phosphogypsum sample. And perform data cross-validation, and then use electrode drift correction coefficients. heavy metal concentration in the sample Make corrections; Step 6: Perform a stepwise, quantitative cleaning of the entire flow path using deionized water and dilute nitric acid, and calculate the cleaning saturation. To determine whether the cleaning is up to standard and whether there is any cross-contamination.

[0024] Specifically, the moisture content correction factor calculated in step one. This is used to introduce the volume of extractant added in step three. Corrections were made to address the issue of leaching efficiency deviations and reduced detection accuracy caused by moisture content fluctuations. Simultaneously, a homogenization pretreatment of the phosphogypsum sample in step two was performed to adapt the method to the highly crystalline and easily agglomerated characteristics of phosphogypsum, ensuring long-term operation and preventing pipeline blockage and filter membrane damage, thus guaranteeing sufficient leaching. A multi-channel parallel detection method was created to allow for cross-validation of detection data, facilitating the removal or correction of outliers. Temperature compensation and electrode drift correction were also introduced to adjust for heavy metal concentration in the samples. This significantly improves detection accuracy; step six involves graded and quantitative cleaning of the entire flow path, followed by a cleaning saturation test. The calculation method determines whether the cleaning is qualified and whether there is cross-contamination, which solves the problem of decreased detection accuracy caused by pipeline contamination, achieves long-term maintenance-free operation, and meets the needs of online and continuous detection of phosphogypsum.

[0025] The complete flow path in step six refers to: the parallel reaction vessel chamber, the solid-liquid separation unit chamber, the electrode pool of the heavy metal detection unit, and all material conveying pipelines connecting each unit.

[0026] In step one, the moisture content correction coefficient is calculated using the following formula. : In the formula, This is a correction factor with a value of 0.015; The standard moisture content is 5%.

[0027] Combined with the measured moisture content of the phosphogypsum sample Calculate the moisture content correction factor The effect of the water content of the phosphogypsum sample on the liquid-solid ratio of the filtrate was quantitatively corrected, providing a basis for subsequent accurate calculation of the extraction agent dosing volume. Benchmark parameters are provided to ensure that leaching conditions strictly meet design requirements.

[0028] The particle size uniformity of the phosphogypsum sample after sieving and grinding in step two. The calculation is performed using the following formula: , In the formula, The maximum particle size of the phosphogypsum sample. The minimum particle size of the phosphogypsum sample is given. The average particle size; when When the particle size uniformity meets the requirements, it indicates that the particle size uniformity meets the requirements.

[0029] Specifically, the particle size uniformity of the phosphogypsum sample after step two was calculated. The substandard phosphogypsum samples underwent secondary grinding to improve particle size uniformity. By strictly controlling the concentration to within 10%, the differences in leaching reaction rate and efficiency caused by the high crystallinity and easy agglomeration characteristics of phosphogypsum were eliminated, ensuring the consistency and repeatability of the leaching process of different batches of phosphogypsum samples.

[0030] In step three, the temperature of all equal-amount phosphogypsum samples was controlled at 25°C and the pH value at 5-6, in accordance with national standards, and the volume of extractant added was also controlled. Ensure that the liquid-to-solid ratio of all equally aliquoted phosphogypsum samples matches the standard liquid-to-solid ratio. Consistent.

[0031] The volume of the extractant added The calculation is performed using the following formula: In the formula, the volume of the extractant added is... The unit is mL; Mass of a single phosphogypsum sample, in grams; standard liquid-to-solid ratio ; Leaching reaction efficiency of each phosphogypsum sample The calculation is performed using the following formula: , In the formula, This represents the real-time leaching concentration. To balance the leaching concentration, all units are mg / L; when When the leaching is complete, it indicates that the leaching is complete and meets the testing requirements.

[0032] Specifically, in calculating the volume of extractant added... In the process, a moisture content correction factor is introduced. The method was modified to address the issue of leaching efficiency deviations and reduced detection accuracy caused by moisture content fluctuations.

[0033] The criteria for determining whether leaching is complete are formulated based on the leaching kinetics of heavy metals in phosphogypsum. 95% is set as the practical threshold for industrial online detection, which ensures both detection accuracy and effectively controls the single detection cycle of the detection system to within 60 minutes.

[0034] By calculating the real-time leaching concentration With equilibrium leaching concentration The ratio of the leaching reaction efficiency is obtained. Using ≥95% as the criterion for complete leaching ensures that heavy metals in the sample are fully leached out, while avoiding unnecessary extension of reaction time and effectively controlling the single detection cycle of the detection system.

[0035] In step four, the following formula is used to determine whether the filter membrane is clogged: In the formula, The pressure difference of the filter membrane. For real-time filtration pressure, This is the initial filtration pressure; when When this occurs, it indicates that the filter membrane is clogged.

[0036] Specifically, when When this occurs, it indicates that the filter membrane is clogged, and automatically triggers filter membrane replacement and cleaning.

[0037] Calculate the real-time filtration pressure With initial filtration pressure The difference in the values ​​determines the filter membrane clogging status, enabling early detection of filter membrane clogging risks and automatic triggering of the replacement process. This prevents excessive turbidity caused by incomplete solid-liquid separation and avoids damage to the detection system caused by abnormal pipeline pressure.

[0038] In step five, the heavy metal concentration of the sample is calculated using the following formula. : In the formula, The peak current of the sample. For blank baseline current, The concentration of the standard solution is... The peak current of the standard liquid is... This is the temperature compensation coefficient; The electrode drift correction factor is calculated using the following formula. : In the formula, The initial standard solution current, For real-time standard solution current, Runtime, in hours; Heavy metal concentration in the sample after electrode drift correction for: .

[0039] In step six, the cleaning saturation is calculated using the following formula. : , In the formula, To reduce the heavy metal concentration in the cleaning wastewater, This represents the highest heavy metal concentration in the sample. when When the time is right, it indicates that the cleaning is qualified and there is no cross-contamination.

[0040] Specifically, the sample peak current based on anodic stripping voltammetry Combined with blank baseline current Standard solution peak current and temperature compensation coefficient The electrical signal is accurately converted into the corresponding heavy metal concentration value, thus realizing the quantitative detection of the target heavy metal element.

[0041] Calculate the heavy metal concentration in the cleaning waste liquid. With the highest heavy metal concentration in the sample The ratio of the cleaning saturation value Using ≤1% as the criterion for qualified cleaning, this ensures that residual contaminants in liquid contact components such as leaching reactors, testing tanks, and pipelines are thoroughly removed, and cross-contamination between different batches of phosphogypsum samples is eliminated.

[0042] An online detection system for heavy metal leaching toxicity of phosphogypsum includes: The quantitative sampling unit is used to quantitatively sample phosphogypsum and collect the measured moisture content of the phosphogypsum sample. Transmitted to the PLC controller for moisture content correction factor calculate.

[0043] Specifically, the quantitative sampling unit uses a telescopic closed-loop sampling probe, adaptable to both belt conveyor and stockpile conditions. It incorporates a high-precision weighing sensor and a moisture content detection sensor to measure the real-time moisture content of phosphogypsum samples. .

[0044] A two-stage pretreatment unit is used to perform primary vibration sieving and secondary shear grinding on the phosphogypsum samples collected by the quantitative sampling unit.

[0045] Specifically, after the phosphogypsum sample undergoes primary vibration sieving and secondary shearing and grinding pretreatment in a two-stage pretreatment unit, the problem of insufficient leaching caused by phosphogypsum agglomeration and uneven particle size can be solved.

[0046] The leaching reaction unit has multiple sets of parallel reaction vessels built in. Each set of parallel reaction vessels is used to control the leaching conditions of multiple phosphogypsum samples obtained after being processed by the two-stage pretreatment unit and divided into equal portions, so as to achieve synchronous and parallel leaching reactions.

[0047] Specifically, the leaching reaction unit has two sets of parallel reaction vessels built in, each with an effective volume of 2L. It is equipped with a magnetic constant temperature stirring module, an automatic liquid addition module, and a pH closed-loop adjustment module. It strictly follows national standards to control leaching conditions and simultaneously detects parallel samples to improve data reliability.

[0048] The solid-liquid separation unit is used to simultaneously and in parallel perform negative pressure filtration on all phosphogypsum samples that have completed the leaching reaction, and transmits the real-time filtration pressure to the PLC controller to determine the filter membrane clogging status.

[0049] Specifically, the solid-liquid separation unit uses a 0.45μm aqueous microporous filter membrane with a negative pressure filtration structure, and has a built-in filtration pressure detection sensor. Together with a PLC controller, it can monitor the filter membrane clogging status in real time and automatically switch to a backup filter membrane.

[0050] The heavy metal detection unit is equipped with multiple independent three-electrode systems, and the three-electrode system has a built-in temperature compensation module, which is used to simultaneously and in parallel detect heavy metals in the filtrate of all phosphogypsum samples using anodic stripping voltammetry.

[0051] Specifically, the heavy metal detection unit is a dual-channel heavy metal detection unit, equipped with two independent three-electrode systems to simultaneously detect five characteristic heavy metals: lead, cadmium, total chromium, arsenic, and mercury. The two sets of data are cross-validated. The three-electrode system has a built-in temperature compensation module to eliminate interference from ambient temperature.

[0052] An automatic cleaning unit is used for graded and quantitative cleaning of the entire flow path.

[0053] The PLC controller is connected to the quantitative sampling unit, the two-stage pretreatment unit, the leaching reaction unit, the solid-liquid separation unit, and the heavy metal detection unit, and executes the online detection method for heavy metal leaching toxicity of phosphogypsum.

[0054] Specifically, the system is a vertical, sealed cabinet structure, integrating the seven functional units mentioned above (including the PLC controller). All components in contact with materials are made of polytetrafluoroethylene (PTFE) or 316L stainless steel, which have the advantages of being resistant to acid and alkali corrosion and preventing the leaching of heavy metals. Except for the PLC controller, the technical parameters of the other six functional units are shown in Table 1.

[0055] Table 1. Comparison of Technical Parameters of Core Functional Units of the System

[0056] The system adopts a sequential batch continuous operation mode with a detection cycle of ≤60 minutes. It automatically performs blank calibration, standard solution calibration, and parallel sample calibration at midnight every day. If the calibration fails, the process is automatically locked and an alarm is triggered.

[0057] Specifically, the system can run 24 hours a day without interruption.

[0058] The national standard limits and calibration parameters for controlling heavy metals are shown in Table 2.

[0059] Table 2 National Standard Limits for Characteristic Heavy Metals and System Calibration Parameters

[0060] Example 2 The method and system provided by this invention were applied to the conveyor belt discharge port of a phosphate chemical plant in Guizhou Province. The ambient temperature was 22℃, and the system operated continuously for 24 hours, with a single-cycle detection time of 58 minutes. The process is as follows: 1. Basic setting parameters Sample quantification quality =100.00g; Standard liquid-to-solid ratio =10:1; Standard moisture content =5%; Correction factor =0.015; Temperature compensation coefficient =1.02; Blank baseline current =2.1μA; peak current of standard solution =45.6μA; standard solution concentration =1.0mg / L; Continuous operating time of the equipment =720h.

[0061] 2. Step-by-step formula calculation and working condition verification Step 1: Calculation of moisture content correction factor Measured moisture content =6.8%, .

[0062] Step 2: Calculation of pre-treated particle size uniformity Actual measurement of the ground phosphogypsum sample: =0.92mm, =0.76mm, average particle size =0.84mm.

[0063] , The phosphogypsum sample after secondary grinding indicates that the particle size uniformity does not meet the requirements. =0.88mm, =0.80mm, , This indicates that the pretreatment was qualified, but the particle size uniformity did not meet the requirements.

[0064] Step 3: Calculation of extraction agent volume The system automatically dispenses the extractant in a quantitative manner with an error of ±0.5 mL.

[0065] Specifically, based on the mass of a single phosphogypsum sample Standard liquid-to-solid ratio and moisture content correction factor Precisely calculate the volume of extractant added Furthermore, the system automatically adds the extractant in a quantitative manner, achieving a control precision of ±0.5mL, completely avoiding errors caused by manual solution preparation and ensuring the consistency of the liquid-solid ratio in each batch of leaching reaction.

[0066] Step 4: Leaching efficiency verification The measured real-time leaching concentration was =0.214 mg / L, equilibrium leaching concentration is =0.217mg / L, The leaching was complete and met the testing requirements.

[0067] Step 5: Filter membrane clogging determination Initial filtration pressure is =-0.08MPa, real-time filtration pressure is =-0.083MPa, The filter membrane is not clogged and does not need to be replaced.

[0068] Step 6: Quantitative Calculation of Heavy Metal Concentration The measured peak current of the sample is =11.5μA, .

[0069] Step 7: Electrode drift correction calculation The initial standard solution current is =45.6μA, real-time standard solution current is =44.2μA, Corrected sample heavy metal concentration Pb= The drift is negligible.

[0070] Specifically, calculate the electrode drift correction factor. The core objective is to provide real-time quantitative compensation for the attenuation of the response signal in a three-electrode system due to long-term continuous operation, and to address the current response sensitivity shift caused by electrode surface adsorption contamination, material aging, and decreased electrochemical activity in anodic stripping voltammetry. This electrode drift correction coefficient... Between daily automatic standard solution calibration cycles, the original detection concentrations of all heavy metal elements, after temperature compensation, are corrected batch by batch. This prevents the detection data from gradually deviating from the true value over time during the two calibration intervals. Simultaneously, it eliminates the drift differences between the independent electrodes of the two channels in the dual-channel module, ensuring the consistency of parallel detection data. In this embodiment, the corrected concentration showed no significant change, solely because the electrode state was stable and the drift was minimal during 720 hours of continuous equipment operation.

[0071] Step 8: Determining the cleaning saturation Highest concentration of cleaning waste liquid =0.002 mg / L, the highest heavy metal concentration in the sample. =0.220mg / L, The cleaning was satisfactory and there was no cross-contamination.

[0072] 3. Summary of dual-channel full-element detection results Table 3. Detection Results After All-Element Formula Calculation

[0073] 4. Methods and System Operation Conclusions All indicators met the system control thresholds; the parallelism of the dual-channel detection data was good, and the overall relative deviation after correction was ≤2.3%, which was consistent with the national standard laboratory method; the system ran continuously for 30 days without filter blockage, electrode drift, or cleaning qualification rate of 100%, without human intervention.

Claims

1. An online detection method for heavy metal leaching toxicity of phosphogypsum, characterized in that: Includes the following steps: Step 1: Quantitatively sample phosphogypsum and collect the measured moisture content of the phosphogypsum samples. Then based on the measured moisture content Calculate the moisture content correction factor ; Step 2: Sieve and grind the phosphogypsum sample, calculate and ensure its particle size uniformity. Meet the needs; Step 3: Divide the phosphogypsum sample into multiple equal portions, and control the leaching conditions of all equal portions of phosphogypsum sample according to national standards. Then, carry out the leaching reaction of all equal portions of phosphogypsum sample simultaneously and in parallel, and calculate the leaching reaction efficiency of each phosphogypsum sample. ; Step 4: Simultaneously and in parallel perform negative pressure filtration on all phosphogypsum samples that have completed the leaching reaction, then monitor the filter membrane clogging status in real time, and switch to the backup filter membrane when the filter membrane becomes clogged. Step 5: Simultaneously and in parallel, perform heavy metal detection on the filtrate of all phosphogypsum samples using anodic stripping voltammetry, and calculate the temperature-compensated heavy metal concentration in the filtrate of each phosphogypsum sample. And perform data cross-validation, and then use electrode drift correction coefficients. heavy metal concentration in the sample Make corrections; Step 6: Perform a stepwise, quantitative cleaning of the entire flow path using deionized water and dilute nitric acid, and calculate the cleaning saturation. To determine whether the cleaning is up to standard and whether there is any cross-contamination.

2. The online detection method for heavy metal leaching toxicity of phosphogypsum as described in claim 1, characterized in that: In step one, the moisture content correction coefficient is calculated using the following formula. : In the formula, This is a correction factor with a value of 0.015; The standard moisture content is 5%.

3. The online detection method for heavy metal leaching toxicity of phosphogypsum as described in claim 1, characterized in that: The particle size uniformity of the phosphogypsum sample after sieving and grinding in step two. The calculation is performed using the following formula: ， In the formula, The maximum particle size of the phosphogypsum sample is [missing information]. The minimum particle size of the phosphogypsum sample is given. The average particle size; when When the particle size uniformity meets the requirements, it indicates that the particle size uniformity meets the requirements.

4. The online detection method for heavy metal leaching toxicity of phosphogypsum as described in claim 1, characterized in that: In step three, the temperature of all equal-amount phosphogypsum samples was controlled at 25°C and the pH value at 5-6, in accordance with national standards, and the volume of extractant added was also controlled. Ensure that the liquid-to-solid ratio of all equally aliquoted phosphogypsum samples matches the standard liquid-to-solid ratio. Consistent.

5. The online detection method for heavy metal leaching toxicity of phosphogypsum as described in claim 4, characterized in that: The volume of the extractant added The calculation is performed using the following formula: In the formula, the volume of the extractant added is... The unit is mL; The mass of a single phosphogypsum sample is expressed in grams. Standard liquid-solid ratio ; Leaching reaction efficiency of each phosphogypsum sample The calculation is performed using the following formula: ， In the formula, This represents the real-time leaching concentration. To balance the leaching concentration, all units are mg / L; when When the leaching is complete, it indicates that the leaching is complete and meets the testing requirements.

6. The online detection method for heavy metal leaching toxicity of phosphogypsum as described in claim 1, characterized in that: In step four, the following formula is used to determine whether the filter membrane is clogged: In the formula, The pressure difference of the filter membrane. For real-time filtration pressure, This is the initial filtration pressure; when When this occurs, it indicates that the filter membrane is clogged.

7. The online detection method for heavy metal leaching toxicity of phosphogypsum as described in claim 1, characterized in that: In step five, the heavy metal concentration of the sample is calculated using the following formula. : In the formula, The peak current of the sample. For blank baseline current, The concentration of the standard solution is... The peak current of the standard liquid is... This is the temperature compensation coefficient; The electrode drift correction factor is calculated using the following formula. : In the formula, The initial standard solution current, For real-time standard solution current, Runtime, in hours; Heavy metal concentration in the sample after electrode drift correction for: 。 8. The online detection method for heavy metal leaching toxicity of phosphogypsum as described in claim 1, characterized in that: In step six, the cleaning saturation is calculated using the following formula. : ， In the formula, To reduce the heavy metal concentration in the cleaning wastewater, This represents the highest heavy metal concentration in the sample. when When the time is right, it indicates that the cleaning is qualified and there is no cross-contamination.

9. An online detection system for heavy metal leaching toxicity of phosphogypsum, characterized in that: include: The quantitative sampling unit is used to quantitatively sample phosphogypsum and collect the measured moisture content of the phosphogypsum sample. Transmitted to the PLC controller for moisture content correction factor calculate; A two-stage pretreatment unit is used to perform primary vibration sieving and secondary shear grinding on the phosphogypsum samples collected by the quantitative sampling unit; The leaching reaction unit has multiple sets of parallel reaction vessels built in. Each set of parallel reaction vessels is used one by one to control the leaching conditions of multiple phosphogypsum samples obtained after being processed by the two-stage pretreatment unit and divided into equal portions, so as to achieve synchronous and parallel leaching reaction. The solid-liquid separation unit is used to simultaneously and in parallel perform negative pressure filtration on all phosphogypsum samples that have completed the leaching reaction, and transmits the real-time filtration pressure to the PLC controller for judging the filter membrane blockage status. The heavy metal detection unit is equipped with multiple independent three-electrode systems, and the three-electrode system has a built-in temperature compensation module, which is used to simultaneously and in parallel perform heavy metal detection on the filtrate of all phosphogypsum samples using anodic stripping voltammetry. An automatic cleaning unit is used for graded and quantitative cleaning of the entire flow path; The PLC controller is communicatively connected to the quantitative sampling unit, the two-stage pretreatment unit, the leaching reaction unit, the solid-liquid separation unit, and the heavy metal detection unit, and executes the online detection method for heavy metal leaching toxicity of phosphogypsum as described in any one of claims 1 to 8.

10. The online detection system for heavy metal leaching toxicity of phosphogypsum as described in claim 9, characterized in that: The system adopts a sequential batch continuous operation mode with a detection cycle of ≤60 minutes. It automatically performs blank calibration, standard solution calibration, and parallel sample calibration at midnight every day. If the calibration fails, the process is automatically locked and an alarm is triggered.

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