Soil chloride ion detection pretreatment device, usage method and filter paper preparation method

Abstract

This invention discloses a soil chloride ion detection pretreatment device, its usage method, and a filter paper preparation method, relating to the field of laboratory equipment technology. The device includes a funnel placement rack with a double-compartment funnel inserted inside. Eight evenly distributed structural support ribs are fixedly installed on the inner wall of the double-compartment funnel. Folded composite filter paper and a nylon support mesh are placed sequentially on the structural support ribs. The activated carbon fiber layer, through acid elution with dilute nitric acid, efficiently adsorbs colored substances such as humus and organic matter in the soil extract, achieving a clear and transparent filtrate. This eliminates the interference of deep yellow and brown hues on the brick-red endpoint of the silver nitrate titration method, making the endpoint clearly distinguishable and stabilizing the chloride ion recovery rate at 92.0%–105.0%. This solves the problem of the silver nitrate titration method lacking a decolorization step, resulting in a blurred endpoint due to high-chroma soil extract and a detection error exceeding 20%.

Description

Technical Field

[0001] This invention relates to the field of laboratory equipment technology, specifically to a soil chloride ion detection pretreatment device, its usage method, and a filter paper preparation method. Background Technology

[0002] Soil chloride ion content is a key indicator for evaluating soil salinization, guiding agricultural production, and conducting environmental monitoring. Currently, the silver nitrate titration method in NY / T1121.17-2006 "Soil Testing Part 17: Determination of Soil Chloride Ions" is widely used for soil chloride ion detection in my country. This method has the advantages of simple equipment, convenient operation, and low detection cost, making it the preferred detection method for grassroots laboratories.

[0003] However, in practical applications, this method has significant limitations. For samples containing high levels of organic matter, such as soil, red soil, and humus, the extract is usually dark yellow to dark brown, which severely interferes with the determination of the brick-red titration endpoint in the silver nitrate titration method, leading to large deviations in the test results.

[0004] To address the chromaticity interference problem, the industry currently employs several methods, but all have significant shortcomings: 1. Silver nitrate titration method: The standard method itself does not have a dedicated decolorization step. For high-chromaticity samples, the endpoint is unclear, and the detection error can reach more than 20%, which cannot meet the requirements for detection accuracy.

[0005] 2. Activated carbon powder decolorization method: This is currently the most commonly used improved method, but it has the following drawbacks: Activated carbon has a strong adsorption effect on chloride ions, but there are no uniform optimized usage conditions, resulting in low chloride ion recovery rate and systematically low detection results. Ordinary activated carbon has a high background chloride ion content (usually 0.05-0.15 mg / L), which will introduce additional chloride ions into the sample and cause background interference. The powder needs to be weighed and filled manually, which is cumbersome and the dosage is difficult to control. The decolorization effect depends entirely on the operator's experience. The amount of activated carbon used and the tightness of filling vary greatly, resulting in large batch-to-batch differences. It is also easy to generate dust pollution, which is harmful to the health of laboratory personnel.

[0006] 3. Lack of dedicated pretreatment equipment: Currently, there is a lack of dedicated filtration and decolorization equipment for soil chloride ion detection. Ordinary glass funnels are commonly used for filtration, which presents the following specific problems: Parallel samples need to be filtered one by one or two independent funnels are used, making it difficult to keep the processing conditions consistent, which affects the repeatability and precision of the test results; The filter paper adheres tightly to the inner wall of the funnel, resulting in a slow flow rate of the filtrate and a large amount of residue. The filter paper has no special support at the bottom, and activated carbon powder easily accumulates and blocks the liquid outlet. Ordinary glass funnels use a straight tube for liquid dispensing, which makes it easy for liquid to stick to the walls and remain. Liquid can easily seep through along the edges of the filter paper, leading to incomplete decolorization and cross-contamination; The funnel's inner wall needs to be thoroughly cleaned after each use, which is time-consuming, laborious, and often incomplete, further increasing the risk of cross-contamination.

[0007] Potentiometric titration: Although potentiometric titration can avoid the interference of colorimetry in endpoint determination, this method requires expensive specialized instruments and equipment, and the purchase and maintenance costs are high, making it difficult to widely popularize in grassroots laboratories. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention provides a soil chloride ion detection pretreatment device, a method for using it, and a method for preparing filter paper, thus solving the problems of existing devices.

[0009] To achieve the above objectives, the present invention provides the following technical solution: A soil chloride ion detection pretreatment device includes a funnel placement rack, in which a double-compartment funnel is inserted. Eight evenly distributed structural support ribs are fixedly installed on the inner wall of the double-compartment funnel. Folded composite filter paper and nylon support net are placed sequentially on the structural support ribs. The funnel placement rack includes a base, a pollution-proof partition is fixedly installed at the center of the base, and symmetrically distributed funnel support frames are fixedly installed on both sides of the pollution-proof partition. A connecting plate is fixedly installed in the middle of the dual-compartment funnel. The connecting plate has an insertion limiting hole in the center that is compatible with the top of the anti-pollution partition. The liquid outlet end of the dual-compartment funnel is integrally connected to a liquid outlet conduit. The anti-pollution partition and the double-compartment funnel are both made of transparent material.

[0010] Preferably, the connection end between the dual-compartment funnel and the liquid outlet conduit adopts a rounded transition of more than 3mm, the contact angle is ≥110°, the inner wall of the liquid outlet conduit is mirror polished, and the liquid outlet end is opened at a 45° bevel.

[0011] Preferably, the dual-compartment funnel is made of transparent acid and alkali resistant polypropylene and has an overall dual-compartment integrated structure. The interior consists of two independent, non-communicating, inverted conical cavities of equal volume and size to ensure consistent filtration conditions for parallel samples.

[0012] Preferably, the composite filter paper uses an upper layer of dilute nitric acid-washed dechlorinated activated carbon fiber filter paper and a lower layer of 1.0μm hydrophilic filter membrane hot-pressed filter paper.

[0013] Preferably, the filter paper preparation method includes the following steps: S1. Raw material pretreatment: Take activated carbon fiber filter paper after dechlorination by dilute nitric acid washing, with a thickness of 0.35±0.02mm and a density of 80±5g / m², background... ≤0.01mg / L; The activated carbon fiber filter paper was placed in 5% dilute nitric acid and soaked in a water bath at 60℃ for 30min. Then it was repeatedly washed with deionized water until the pH of the washing solution was 6.0~7.0. Then it was dried in a drying oven at 85±5℃ for 2h to obtain a pretreated activated carbon fiber layer; Separately, a hydrophilic microporous filter membrane with a pore size of 1.0μm was dried at 70℃ for 30min to remove static electricity and moisture to obtain a pretreated filter membrane layer; S2. Cutting and positioning: Cut the pretreated activated carbon fiber layer and filter membrane layer into circular or square sheets of the same size, and leave a 1.5mm wide sealing area at the edge; stack the activated carbon fiber layer as the upper layer and the filter membrane layer as the lower layer, ensuring no wrinkles or misalignment; S3. Apply hot melt adhesive and seal the edges with hot pressing: Apply or lay low-chlorine environmentally friendly hot melt adhesive evenly at a rate of 0.8~1.2g / m² only within the 1.5mm wide sealing area reserved in this step. The hot melt adhesive is a chlorine-free system. S4. Hot pressing lamination: The laminated material after applying adhesive is placed in a hot press and hot pressed for 3 to 5 seconds at a temperature of 120~140℃ and a pressure of 0.3~0.6MPa using a flat plate hot pressing or roller pressing method to form a continuous sealing ring with a width of 1.5mm. The middle filter zone is only lightly pressed to shape without melting and clogging. S5. Cooling and shaping: Allow the hot-pressed composite filter paper to cool naturally at room temperature for 5 minutes, avoiding rapid cooling to prevent warping, delamination and edge cracking; S6. Cutting and Quality Inspection: Cut the cooled composite filter paper into the required shape; inspect the sealing ring for completeness, continuity, absence of bubbles and delamination, and permeability of the middle filtration zone; S7. Final Inspection and Packaging: Randomly sample and inspect the background of composite filter paper. After the concentration is ≤0.01mg / L and the air permeability and filter membrane pore size integrity are qualified, it should be sealed in an aluminum foil bag in a clean environment and stored in a dry place away from light.

[0014] Preferably, the method of using the pretreatment device includes the following steps: S1. Device Assembly: Fold the composite filter paper into an inverted cone shape and place it into the two independent chambers of the double-compartment funnel; place a nylon support mesh at the bottom of the composite filter paper to prevent it from collapsing; check the liquid outlet tube to ensure it is unobstructed and to reduce dead zones for liquid accumulation; S2. Preparation of soil extract: Weigh 50.00g, accurate to 0.01g, air-dry the soil sample, put it into a 500mL plastic bottle, add 250mL of carbon dioxide-free distilled water, seal the bottle, and place it on a shaker for 3min to prepare a soil suspension. S3. Synchronous Filtration and Decolorization: The soil extract is precisely divided into two equal portions using a graduated cylinder and slowly poured into the composite filter paper in the two chambers of the double-compartment funnel. The liquid is sealed by the outer edge to reduce edge creep and leakage. The extract first passes through the activated carbon fiber layer to adsorb pigments and decolorize, and then passes through the 1.0μm microporous filter membrane layer to intercept fine soil particles. The filtrate flows out through the outlet tube at the bottom of the chamber. 10mL of the initial filtrate is discarded to eliminate the instantaneous adsorption effect of activated carbon on chloride ions. The subsequent clear filtrate is collected for later use. S4. Titration test: Pipette 25.00 mL of filtrate into a 150 mL Erlenmeyer flask, add 8 drops of 5% potassium chromate indicator, and titrate with silver nitrate standard solution until a brick-red precipitate appears and does not disappear after shaking. Record the titration volume; at the same time, perform a blank test and record the blank titration volume.

[0015] This invention provides a soil chloride ion detection pretreatment device, a method of use, and a filter paper preparation method, which have the following beneficial effects: 1. This invention achieves efficient adsorption of colored substances such as humus and organic matter in soil extract by rinsing the upper layer of activated carbon fiber with dilute nitric acid, resulting in a clear and transparent filtrate. This eliminates the interference of deep yellow and brown to the brick-red endpoint of the silver nitrate titration method, making the endpoint clearly distinguishable and stabilizing the chloride ion recovery rate at 92.0%–105.0%. It solves the problem that the silver nitrate titration method lacks a decolorization step, and the high-color soil extract leads to a blurred endpoint and a detection error of over 20%. 2. In this invention, activated carbon fibers are subjected to deep chlorine removal treatment with dilute nitric acid, resulting in a background... With a chloride ion concentration ≤0.01 mg / L (ordinary activated carbon powder has a residual chloride ion concentration of approximately 0.05–0.15 mg / L), background interference is effectively eliminated, reducing chloride ion detection error by more than 50%. The optimized pore structure and surface functional groups of activated carbon fibers result in an adsorption loss rate of ≤5% for chloride ions in soil leachate (i.e., a recovery rate ≥95%) (this data is based on experimental conditions with chloride ion concentrations ranging from 20-500 mg / kg soil and a pH of 5.0-8.0). This solves the problem of systematically low results caused by ordinary activated carbon adsorbing chloride ions. By using standardized composite filter paper (with a fixed activated carbon fiber layer), manual weighing and filling of activated carbon are eliminated, significantly simplifying the operation. The composite filter paper achieves industrialized and standardized production, with batch-to-batch deviations in thickness, density, and adsorption capacity ≤5% (compared to traditional manual filling deviations typically ≥20%), ensuring stable and consistent decolorization effects and eliminating systematic errors caused by differences in operator experience. 3. The present invention uses 8 longitudinal vertical support ribs on the inner wall to form a uniform gap between the filter paper and the funnel wall, which accelerates the flow rate of the filtrate and reduces residue, thus solving the problem of filter paper sticking to the wall. The composite filter paper is supported by a bottom nylon support mesh to prevent it from collapsing and to eliminate the phenomenon of activated carbon accumulating and clogging the outlet, thus solving the problem of filter paper collapse and blockage. By using a large arc transition of more than 3mm in diameter, combined with mirror polishing of the inner wall (contact angle ≥110°) and a 45° bevel design, the liquid residue in the tube is less than 0.05mL (about 0.1–0.3mL for a regular glass funnel), thus avoiding contamination of the next sample with residual liquid and solving the problem of liquid residue in the outlet tube. By using a wide sealing ring design at the edge of the composite filter paper, liquid can be effectively prevented from bypassing and leaking along the edge of the filter paper, ensuring that all liquids are decolorized by the activated carbon fiber layer, thus solving the problem of edge liquid contamination. The composite filter paper and nylon support mesh of this invention are both disposable consumables, which are discarded as a whole after use. There is no need to clean the funnel, saving the consumption of pure water and detergent and the manual cleaning steps. The total time for a single sample processing session has been reduced from 16–18 minutes to 6–8 minutes, and the number of steps has been reduced from 7 to 3 (folding filter paper → placing it in the funnel → pouring in liquid). With dual-compartment synchronous filtration, the time required for two parallel samples is the same as that for a single sample. The daily sample processing capacity per person is increased from about 30 to 60-80, improving efficiency by 100%-160% and significantly reducing manpower input.

[0016] 4. This invention only optimizes the pretreatment process. The subsequent titration operation and calculation formula are completely consistent with the NY / T1121.17-2006 standard for silver nitrate titration. There is no need to change the existing detection process and personnel operating habits. Moreover, there is no need to purchase a potentiometric titrator costing tens of thousands of yuan. The detection can be completed with only existing ordinary laboratory equipment, which greatly reduces the detection threshold. The funnel is clean-free through disposable composite filter paper and nylon support mesh, which saves the consumption of pure water and detergent and the cost of manual cleaning, and greatly reduces the loss of samples, reagents and time. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the overall structure of the pretreatment device of the present invention; Figure 2 This is a schematic diagram of the funnel placement rack structure of the pretreatment device of the present invention; Figure 3 This is a schematic diagram of the dual-compartment funnel structure of the pretreatment device of the present invention; Figure 4 This is a schematic diagram of the nylon support mesh structure of the pretreatment device of the present invention; Figure 5 This is a schematic diagram of the composite filter paper structure of the pretreatment device of the present invention; Figure 6 This is a flowchart of the detection method in Embodiment 1 of the present invention.

[0018] In the diagram: 1. Funnel placement rack; 2. Double-compartment funnel; 3. Structural support rib; 4. Composite filter paper; 5. Nylon support mesh; 101. Base; 102. Anti-pollution partition; 103. Funnel support frame; 201. Connecting plate; 202. Insertion limiting hole; 203. Liquid outlet conduit. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0020] Please see Figures 1-5 The soil chloride ion detection pretreatment device includes a funnel placement rack 1, into which a double-compartment funnel 2 (for simultaneous filtration in both compartments, ensuring consistent conditions for parallel samples) is inserted. Eight evenly distributed structural support ribs 3 are fixedly installed on the inner wall of the double-compartment funnel 2. Folded composite filter paper 4 and a nylon support net 5 are placed sequentially on the structural support ribs 3 (the structural support ribs 3 prevent the composite filter paper 4 from adhering to the wall, and the nylon support net 5 prevents the composite filter paper 4 from collapsing; furthermore, both the composite filter paper 4 and the nylon support net 5 are disposable consumables, discarded entirely after use without the need for cleaning). The funnel placement rack 1 includes a base 101, a pollution prevention partition 102 is fixedly installed at the center of the base 101, and funnel support racks 103 are symmetrically distributed on both sides of the pollution prevention partition 102. A connecting plate 201 is fixedly installed in the middle of the double-compartment funnel 2. The center of the connecting plate 201 is provided with an insertion limiting hole 202 that is compatible with the top of the anti-pollution partition 102. The liquid outlet end of the double-compartment funnel 2 is integrally connected with a liquid outlet conduit 203. Both the anti-pollution partition 102 and the double-compartment funnel 2 are made of transparent material.

[0021] The connection end between the double-compartment funnel 2 and the liquid outlet conduit 203 adopts a rounded transition of more than 3mm, with a contact angle ≥110°. The inner wall of the liquid outlet conduit 203 is mirror polished, and the liquid outlet end is opened at a 45° bevel.

[0022] The dual-compartment funnel 2 is made of transparent acid and alkali resistant polypropylene. It has an integrated dual-compartment structure with two independent, equal-volume, and equal-sized inverted conical cavities inside, ensuring consistent filtration conditions for parallel samples.

[0023] The composite filter paper 4 uses an upper layer of dilute nitric acid-washed chlorine-removed activated carbon fiber filter paper and a lower layer of 1.0μm hydrophilic filter membrane hot-pressed filter paper.

[0024] The filter paper preparation method includes the following steps: S1. Raw material pretreatment: Take activated carbon fiber filter paper after dechlorination by dilute nitric acid washing, with a thickness of 0.35±0.02mm and a density of 80±5g / m², background... ≤0.01mg / L; The activated carbon fiber filter paper was placed in 5% dilute nitric acid and soaked in a water bath at 60℃ for 30min, then repeatedly washed with deionized water until the pH of the washing solution was 6.0~7.0, and then dried in a drying oven at 85±5℃ for 2h to obtain a pretreated activated carbon fiber layer; Separately, a hydrophilic microporous filter membrane with a pore size of 1.0μm was dried at 70℃ for 30min to remove static electricity and moisture to obtain a pretreated filter membrane layer; (the hydrophilic microporous filter membrane is preferably a polyethersulfone membrane); S2. Cutting and positioning: Cut the pretreated activated carbon fiber layer and filter membrane layer into circular or square sheets of the same size, and leave a 1.5mm wide sealing area at the edge; stack the activated carbon fiber layer as the upper layer and the filter membrane layer as the lower layer, ensuring no wrinkles or misalignment; S3. Apply hot melt adhesive and seal the edges with hot pressing: Apply or lay low-chlorine environmentally friendly hot melt adhesive evenly at a rate of 0.8~1.2g / m² only within the 1.5mm wide sealing area reserved in this step. The hot melt adhesive should be a chlorine-free system; (preferably food-grade or medical-grade hot melt adhesive membrane; do not apply adhesive to the filter area to prevent pore blockage and chloride ion adsorption). S4. Hot-press lamination: The laminated material after coating is placed in a hot press and hot-pressed for 3-5 seconds at a temperature of 120-140℃ and a pressure of 0.3-0.6MPa using a flat plate hot press or roller press to form a continuous sealing ring (effectively preventing liquid from bypassing and leaking along the edge of the filter paper, ensuring that all liquids are decolorized by the activated carbon fiber layer). The sealing ring is 1.5mm wide, and the middle filtration zone is only lightly pressed to shape without melting and clogging. S5. Cooling and shaping: Allow the hot-pressed composite filter paper 4 to cool naturally at room temperature for 5 minutes, avoiding rapid cooling to prevent warping, delamination and edge cracking; S6. Cutting and quality inspection: Cut the cooled composite filter paper 4 into the required shape; (preferably foldable inverted conical filter paper); inspect that the sealing ring is intact and continuous, without bubbles or delamination, and that the middle filtration zone is transparent; S7. Final Inspection and Packaging: Randomly sample composite filter paper 4 for background testing. After the concentration is ≤0.01mg / L and the air permeability and filter membrane pore size integrity are qualified, it should be sealed in an aluminum foil bag in a clean environment and stored in a dry place away from light.

[0025] Verification of technical effectiveness: 10g of the prepared activated carbon fiber filter paper was cut into small pieces and added to 100mL of deionized water. The mixture was ultrasonically vibrated for 30 minutes, filtered, and the chloride ion content of the filtrate was determined by potentiometric titration. The results showed that the background chloride ion concentration was <0.01mg / L, which is much lower than the 0.15mg / L of untreated activated carbon, meeting the requirements for trace analysis.

[0026] In use, the liquid first passes through the activated carbon fiber layer to adsorb pigments, and then passes through the 1.0μm filter membrane layer to intercept particles, resulting in a clear filtrate.

[0027] The method of using the pretreatment device includes the following steps: S1. Device assembly: Fold the composite filter paper 4 into an inverted cone shape and place it into the two independent chambers of the double-compartment funnel 2; place a nylon support net 5 at the bottom of the composite filter paper 4 to prevent it from collapsing; check the liquid outlet tube 203 to ensure it is unobstructed and to reduce dead zones for liquid accumulation; S2. Preparation of soil extract: Weigh 50.00g of air-dried soil sample (accurate to 0.01g), put it into a 500mL plastic bottle, add 250mL of carbon dioxide-free distilled water, seal the bottle, and place it on a shaker for 3min to prepare a soil suspension. S3. Synchronous Filtration and Decolorization: The soil extract is precisely divided into two equal portions using a graduated cylinder and slowly poured into the composite filter paper 4 in the two chambers of the double-compartment funnel 2. The liquid is sealed by the outer edge to reduce edge creep and leakage. The extract first passes through the activated carbon fiber layer to adsorb pigments and decolorize, and then passes through the 1.0μm microporous filter membrane layer to intercept fine soil particles. The filtrate flows out through the outlet tube 203 at the bottom of the chamber. 10mL of the initial filtrate is discarded to eliminate the instantaneous adsorption effect of activated carbon on chloride ions. The subsequent clear filtrate is collected for later use. S4. Titration test: Pipette 25.00 mL of filtrate into a 150 mL Erlenmeyer flask, add 8 drops of 5% potassium chromate indicator, and titrate with silver nitrate standard solution until a brick-red precipitate appears and does not disappear after shaking. Record the titration volume; at the same time, perform a blank test and record the blank titration volume.

[0028] Specifically: First, weigh 50g (accurate to 0.01g) of air-dried soil sample that has passed through a 2mm sieve and place it in a 500mL wide-mouth plastic bottle, then add 250mL of carbon dioxide-free distilled water.

[0029] Next, after sealing the plastic bottle with a rubber stopper, shake it on a shaker for 3 minutes to prepare the soil extract.

[0030] Third, install the double-compartment funnel 2: Manually fold the composite filter paper 4 into an inverted cone shape and place it into two independent inverted cone cavities. Place a nylon support net 5 at the bottom of each composite filter paper 4 to support the filter paper and prevent it from collapsing. This completes the device preparation.

[0031] Fourth, slowly pour the two portions of soil extract after shaking into the composite filter paper 4 in the two chambers respectively; The extract flows naturally through the composite filter paper 4, where the pigment is first adsorbed by the activated carbon fiber layer, and then the fine particles are intercepted by the 1.0μm filter membrane layer, so that filtration and decolorization are completed simultaneously. Discard the first 10 mL of filtrate to eliminate the momentary adsorption of chloride ions by the activated carbon fiber. Collect the subsequent clear, colorless filtrate and stopper it for later use.

[0032] Finally, pipette 25.00 mL of the filtrate to be tested into a 150 mL Erlenmeyer flask, add 8 drops of 5% potassium chromate indicator, and titrate with silver nitrate standard solution while continuously shaking until a brick-red precipitate appears and no longer disappears after shaking. Record the volume V of silver nitrate standard solution consumed. Take 25.00 mL of distilled water and perform a blank test using the same method, recording the volume of silver nitrate standard solution consumed. .

[0033] Table 1: Summary of Comparative Experiments Between the Invention and Traditional Devices .

[0034] Example 1, please refer to Figures 1-6 This embodiment is used to verify the practical application effect of the dual-compartment funnel of the present invention in the detection of chloride ions in soil (NY / T1121.17-2006 silver nitrate titration method). Compared with traditional detection methods, it verifies the technical advantages of this device in terms of filtration and decolorization effect, detection accuracy, precision and prevention of cross-contamination.

[0035] I. Experimental materials and instruments for this invention: 1. Experimental samples: 3 air-dried soil samples of different colors (numbered 1#, 2#, and 3#, of which 3# is a dark soil with high humus content).

[0036] 2. The device of the present invention.

[0037] 3. Control apparatus: conventional single-compartment glass funnel, 1.0μm filter membrane, ordinary qualitative filter paper, and bulk activated carbon.

[0038] 4. Experimental reagents: carbon dioxide-free distilled water, 5% potassium chromate indicator, silver nitrate standard solution (0.01 mol / L).

[0039] 5. Experimental instruments: shaker, electronic balance (accuracy 0.01g), acid burette, Erlenmeyer flask, graduated cylinder.

[0040] II. Application process of this invention: 1. Device Assembly Fold the composite filter paper 4 into an inverted cone and place it into the two independent chambers of the double-compartment funnel 2. The structural support ribs 3 inside the chamber support the filter paper and reduce it from sticking to the wall. Place a nylon support net 5 at the bottom of the filter paper to prevent it from collapsing. Check the liquid outlet tube 203 to ensure that the tube is unobstructed and to reduce dead zones for liquid accumulation.

[0041] 2. Preparation of soil extract Weigh 50.00g (accurate to 0.01g) of air-dried soil sample, put it into a 500mL plastic bottle, add 250mL of carbon dioxide-free distilled water, seal the bottle, and place it on a shaker to shake for 3min to prepare a soil suspension.

[0042] 3. Synchronous filtration and decolorization The soil extract was precisely divided into two equal portions using a graduated cylinder and slowly poured into the composite filter paper 4 in the two chambers of the double-compartment funnel 2. The liquid was sealed by the outer edge to reduce edge creep and leakage. The extract first passed through the activated carbon fiber layer to adsorb pigments and decolorize, and then passed through the 1.0μm microporous filter membrane layer to intercept fine soil particles. The filtrate flowed out through the outlet tube 203 at the bottom of the chamber. 10mL of the initial filtrate was discarded to eliminate the instantaneous adsorption effect of activated carbon on chloride ions, and the subsequent clear filtrate was collected for later use.

[0043] 4. Titration detection Pipette 25.00 mL of filtrate into a 150 mL Erlenmeyer flask, add 8 drops of 5% potassium chromate indicator, and titrate with silver nitrate standard solution until a brick-red precipitate appears and does not disappear after shaking. Record the titration volume. At the same time, perform a blank test and record the blank titration volume.

[0044] III. Traditional control method operation: A conventional single-compartment glass funnel was used, with ordinary qualitative filter paper, a 1.0μm filter membrane, and bulk activated carbon layered together. Soil samples from the same batch were filtered and decolorized individually. The remaining extraction and titration steps were completely consistent with the method of this invention.

[0045] IV. Experimental Results and Data: Table 2: Comparison of Decolorization Effects ; Table 3: Comparison of Precision and Accuracy in Detection ; Table 4: Filtration Efficiency and Anti-fouling Test Table .

[0046] V. Experimental Conclusions 1. The double-compartment funnel 2 of the present invention can make the filtrate clear and transparent, significantly reduce the color interference problem of the extract of dark soil, and make the titration endpoint clear and easy to judge, reducing the risk of misjudgment.

[0047] 2. Adopting an integrated dual-compartment structure, the relative standard deviation of parallel sample detection is <5.0%, and the chloride ion recovery rate is stable at 92.0%–105.0%, with detection precision and accuracy superior to traditional methods.

[0048] 3. The device has high filtration efficiency, and the dual-compartment simultaneous sample processing significantly improves detection efficiency; the structural support ribs 3, filter paper sealing ring, and anti-residue discharge conduit 203 effectively reduce the risk of cross-contamination.

[0049] 4. The composite filter paper is produced in a standardized manner, with stable and uniform decolorization effect and good batch reproducibility, making it suitable for batch detection of chloride ions in soil.

[0050] Example 2, please refer to Figures 1-5 This embodiment is used to verify the technical advantages of this device in terms of activated carbon morphology and filling method, funnel structure and cleaning, stability of decolorization effect, and residue and pollution in the effluent.

[0051] I. Comparative Example Operation Procedure (Prior Art) Experimental materials: 1. Ordinary 60° glass funnel (inner diameter 90mm).

[0052] 2. Qualitative rapid filter paper (Φ110mm).

[0053] 3. 1.0μm filter membrane.

[0054] 4. Activated carbon powder (analytical grade, 200 mesh, un-acid-washed and dechlorinated).

[0055] 5. Soil extract to be tested (taken from a saline farmland, turned dark brown after shaking extraction).

[0056] 6. Electronic balance, washing bottle, receiving bottle.

[0057] Operating steps: 1. Fold the qualitative filter paper into a cone shape, place it in a glass funnel, and moisten it with pure water to adhere to the wall.

[0058] 2. Weigh 0.50g of activated carbon powder and spread it evenly on filter paper.

[0059] 3. Place the funnel in the receiving bottle and slowly pour in 20 mL of the soil extract to be tested.

[0060] 4. Record the filtering completion time.

[0061] 5. After filtration, rinse the inner wall of the funnel repeatedly with pure water, brush it lightly with a brush, and let it dry for later use.

[0062] 6. Process the next sample using the same steps.

[0063] Practical issues: 1. Activated carbon powder is easily washed to the edge, forming a bypass and resulting in insufficient decolorization.

[0064] 2. The flow rate decreases significantly in the later stages of filtration, making it easy for residual liquid to remain.

[0065] 3. Dust is noticeable during the weighing and spreading of activated carbon.

[0066] 4. Fine carbon particles may still remain on the inner wall of the funnel after cleaning.

[0067] II. Operation process of the present invention Experimental materials: 1. Double-compartment funnel 2 (PP material, two independent compartments, with longitudinal vertical ridges and hydrophobic liquid outlet tube).

[0068] 2. Two-in-one composite filter paper 4 (dilute nitric acid acid-washed chlorine activated carbon fiber layer + 1.0μm filter membrane, hot-pressed composite, with sealing ring).

[0069] 3. Nylon support mesh 5 (3mm aperture).

[0070] 4. Soil extracts from the same batch of samples.

[0071] Operating steps: 1. Fold the composite filter paper into a cone shape, place it in the cavity, and place a support mesh at the bottom.

[0072] 2. Slowly pour in 20mL of extract.

[0073] 3. Record the filtering completion time.

[0074] 4. After use, discard the filter paper and support mesh. The funnel body does not need to be cleaned; proceed directly to the next sample.

[0075] III. Comparison of Experimental Results and Data: Table 5: Comparison Data Table .

[0076] IV. Comparative Analysis of the Invention with the Comparative Examples 1. Activated carbon form and filling method The comparative example used powdered activated carbon, which was manually weighed and spread. The dosage varied greatly, it was easy to form a bypass, and there was dust pollution.

[0077] This invention uses standardized activated carbon fiber filter paper, which requires no weighing, produces no obvious dust, has uniform pores, and significantly reduces bypass leakage.

[0078] 2. Funnel structure and cleaning The comparative example filter paper adhered tightly to the inner wall, leaving a lot of residue. It had to be washed repeatedly, which could easily cause cross-contamination.

[0079] This invention uses vertical protrusions to suspend the filter paper, reducing residual liquid retention; disposable consumables are used and discarded immediately, significantly reducing the risk of cross-contamination.

[0080] 3. Stability of decolorization effect The comparative examples were greatly affected by human operation, with significant fluctuations in decolorization effect and poor reproducibility.

[0081] This invention uses standardized composite filter paper, which has good batch-to-batch stability and uniform and stable decolorization effect.

[0082] 4. Drainage residue and contamination The comparative example's liquid outlet tube is prone to sticking to the wall and leaving residues, which can easily cause contamination between samples.

[0083] This invention employs a hydrophobic conduit and a pointed nozzle design to reduce wall adhesion and residue, further reducing cross-contamination.

[0084] V. Summary The comparison shows that the traditional funnel + powdered activated carbon has the following drawbacks: complicated operation, long time consumption, easy dust generation, unstable decolorization, troublesome cleaning, easy clogging, and easy cross-contamination.

[0085] This invention achieves significant improvements in filtration efficiency, ease of operation, detection stability, and cross-contamination control through structural innovations such as an integrated dual-compartment funnel 2, standardized composite filter paper 4, anti-wall adhesion cavity, and low-residue discharge conduit 203, representing a significant advancement over existing technologies.

[0086] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A soil chloride ion detection pretreatment device, characterized in that, Includes a funnel placement rack (1), a double-compartment funnel (2) is inserted into the funnel placement rack (1), and eight evenly distributed structural support ribs (3) are fixedly installed on the inner wall of the double-compartment funnel (2). Folded composite filter paper (4) and nylon support net (5) are placed on the structural support ribs (3) in sequence. The funnel placement rack (1) includes a base (101), a pollution prevention partition (102) is fixedly installed at the center of the base (101), and symmetrically distributed funnel support frames (103) are fixedly installed on both sides of the pollution prevention partition (102). A connecting plate (201) is fixedly installed in the middle of the double-compartment funnel (2). The connecting plate (201) has an insertion limiting hole (202) in the center that is compatible with the top of the anti-pollution partition (102). The liquid outlet end of the double-compartment funnel (2) is integrally connected with a liquid outlet conduit (203). The anti-pollution partition (102) and the double-compartment funnel (2) are both made of transparent material; The composite filter paper (4) is made of dilute nitric acid-washed chlorine activated carbon fiber filter paper in the upper layer and 1.0 μm hydrophilic filter membrane hot-pressed filter paper in the lower layer.

2. The soil chloride ion detection pretreatment device according to claim 1, characterized in that, The connection end between the double-compartment funnel (2) and the liquid outlet conduit (203) adopts a rounded transition of more than 3mm, and the contact angle is ≥110°. The inner wall of the liquid outlet conduit (203) is mirror polished, and the liquid outlet end is opened at a 45° bevel.

3. The soil chloride ion detection pretreatment device according to claim 1, characterized in that, The dual-compartment funnel (2) is made of transparent acid and alkali resistant polypropylene. It has a dual-compartment integrated structure with two independent, equal-volume, and equal-sized inverted conical cavities inside, ensuring consistent filtration conditions for parallel samples.

4. A method for preparing filter paper, used to prepare the composite filter paper in the soil chloride ion detection pretreatment device according to claim 1, characterized in that, Includes the following steps: S1. Raw material pretreatment: Take activated carbon fiber filter paper after dechlorination by dilute nitric acid washing, with a thickness of 0.35±0.02mm and a density of 80±5g / m², background... ≤0.01mg / L; The activated carbon fiber filter paper was placed in 5% dilute nitric acid and soaked in a water bath at 60℃ for 30min. Then it was repeatedly washed with deionized water until the pH of the washing solution was 6.0~7.

0. Then it was dried in a drying oven at 85±5℃ for 2h to obtain a pretreated activated carbon fiber layer; Separately, a hydrophilic microporous filter membrane with a pore size of 1.0μm was dried at 70℃ for 30min to remove static electricity and moisture to obtain a pretreated filter membrane layer; S2. Cutting and positioning: Cut the pretreated activated carbon fiber layer and filter membrane layer into circular or square sheets of the same size, and leave a 1.5mm wide sealing area at the edge; stack the activated carbon fiber layer as the upper layer and the filter membrane layer as the lower layer, ensuring no wrinkles or misalignment; S3. Apply hot melt adhesive and seal the edges with hot pressing: Apply or lay low-chlorine environmentally friendly hot melt adhesive evenly at a rate of 0.8~1.2g / m² only within the 1.5mm wide sealing area reserved in this step. The hot melt adhesive is a chlorine-free system. S4. Hot pressing lamination: The laminated material after applying adhesive is placed in a hot press and hot pressed for 3 to 5 seconds at a temperature of 120~140℃ and a pressure of 0.3~0.6MPa using a flat plate hot pressing or roller pressing method to form a continuous sealing ring with a width of 1.5mm. The middle filter zone is only lightly pressed to shape without melting and clogging. S5. Cooling and shaping: Cool the hot-pressed composite filter paper (4) naturally at room temperature for 5 minutes, avoiding rapid cooling to prevent warping, delamination and edge cracking; S6. Cutting and quality inspection: Cut the cooled composite filter paper (4) into the required shape; inspect the sealing ring for completeness, continuity, absence of bubbles and delamination, and permeability of the middle filtration zone; S7. Final Inspection and Packaging: Background of random sampling of composite filter paper (4) After the concentration is ≤0.01mg / L and the air permeability and filter membrane pore size integrity are qualified, it should be sealed in an aluminum foil bag in a clean environment and stored in a dry place away from light.

5. A method of using the soil chloride ion detection pretreatment device, applied to the soil chloride ion detection pretreatment device according to any one of claims 1-3, characterized in that, Includes the following steps: S1. Assembly of the device: Fold the composite filter paper (4) into an inverted cone and place it into the two independent chambers of the double-chamber funnel (2); place a nylon support net (5) at the bottom of the composite filter paper (4) to prevent the composite filter paper (4) from collapsing; check the liquid outlet tube (203) to ensure that the tube is unobstructed and reduce dead corners of liquid accumulation; S2. Preparation of soil extract: Weigh 50.00g, accurate to 0.01g, air-dry the soil sample, put it into a 500mL plastic bottle, add 250mL of carbon dioxide-free distilled water, seal the bottle, and place it on a shaker for 3min to prepare a soil suspension. S3. Synchronous filtration and decolorization: The soil extract is precisely divided into two equal portions using a graduated cylinder and slowly poured into the composite filter paper (4) in the two chambers of the double-chamber funnel (2); the liquid is sealed by the outer edge to reduce edge creep and leakage; the extract first adsorbs pigments and decolorizes through the activated carbon fiber layer, and then intercepts fine soil particles through the 1.0μm microporous filter membrane layer; the filtrate flows out through the liquid outlet tube (203) at the bottom of the chamber, discarding 10mL of the initial filtrate to eliminate the instantaneous adsorption effect of activated carbon on chloride ions, and collecting the subsequent clear filtrate for later use; S4. Titration test: Pipette 25.00 mL of filtrate into a 150 mL Erlenmeyer flask, add 8 drops of 5% potassium chromate indicator, and titrate with silver nitrate standard solution until a brick-red precipitate appears and does not disappear after shaking. Record the titration volume; at the same time, perform a blank test and record the blank titration volume.

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