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CN-121994889-A - Chroma-compared concentration detection sensor and application thereof in phosphoric acid detection

CN121994889ACN 121994889 ACN121994889 ACN 121994889ACN-121994889-A

Abstract

The invention discloses a colorimetric concentration detection sensor and application thereof in phosphoric acid detection, and belongs to the technical field of phosphoric acid detection. The sensor integrates a chromaticity detection unit, a comparison detection unit and a concentration detection unit, can synchronously realize the rapid detection of chromaticity, comparison and concentration of the refined phosphoric acid, completes signal acquisition by combining a differential pulse voltammetry and an alternating current impedance method, and eliminates detection deviation caused by a high-temperature working condition by a temperature compensation formula. The method has the advantages of quick response, high precision and strong stability, can effectively reduce the risk of manual operation, is suitable for controlling the production process of the sections of wet phosphoric acid extraction, decolorization, concentration and the like, and fills the industry blank of multi-parameter synchronous detection.

Inventors

  • QU GUANGFEI
  • SUN CHENXIN
  • PAN KEHENG
  • Du Wanyuan
  • XU RUI
  • ZHENG HAN
  • SHI YUCHEN

Assignees

  • 昆明理工大学

Dates

Publication Date
20260508
Application Date
20260323

Claims (7)

  1. 1. The colorimetric compared concentration detection sensor is characterized by comprising a colorimetric detection unit, a comparing detection unit and a concentration detection unit; the colorimetric detection unit is a working electrode I, a reference electrode I and an auxiliary electrode I, wherein the working electrode I is a platinum electrode of a surface modification organic group selective chelating coating, and the preparation of the platinum electrode of the surface modification organic group selective chelating coating is as follows: (1) Selecting platinum sheets with purity more than or equal to 99.99%, sequentially polishing with silicon carbide sand paper of 800 meshes, 1200 meshes and 2000 meshes step by step, ultrasonically cleaning with absolute ethyl alcohol for 10-20min, ultrasonically cleaning with deionized water for 8-12min, finally activating in sulfuric acid solution of 0.5mol/L by cyclic voltammetry, scanning in a range of-0.2-1.2V at a scanning rate of 40-60mV/s, and circulating for 20 circles; (2) Dissolving an organic phosphine chelating agent in an acetic acid-sodium acetate buffer solution with the pH value of=3.0 according to the proportion of 0.5-1.0g/L, immersing an activated platinum substrate in the solution, performing electropolymerization modification for 25-35min at the constant potential of 0.9-1.2V, and then curing for 1-3h in a 55-65 ℃ vacuum drying oven to form an organic group selective chelating coating with the thickness of 20-50nm, wherein the organic phosphine chelating agent is amino trimethylene phosphonic acid; The detection unit consists of a top hydrophobic electrode, a middle composite electrode and a bottom hydrophilic electrode, wherein the preparation of the top hydrophobic electrode is as follows: (1) Taking a platinum sheet with the purity of more than or equal to 99.99 percent as a substrate, ultrasonically cleaning the substrate for 8-12min by absolute ethyl alcohol, washing the substrate by deionized water, and drying the substrate for 25-35min at 110-130 ℃; (2) Placing the pretreated substrate in a vapor deposition furnace, taking polytetrafluoroethylene micropowder as a raw material, and depositing for 30-60min under the conditions of 380-400 ℃ and vacuum degree less than or equal to 10Pa, wherein the thickness of the film is controlled to be 50-100nm; (3) Naturally cooling to room temperature after the deposition is finished, and annealing for 1h at 200 ℃ to ensure that the binding force of the film and the substrate is more than or equal to 5N/cm 2 and the contact angle reaches 110 DEG + -5 DEG; the preparation of the middle composite electrode is as follows: (1) Taking a platinum sheet with the purity of more than or equal to 99.99 percent as a substrate, sequentially polishing the substrate to a mirror surface step by using silicon carbide sand paper with 800 meshes, 1200 meshes and 2000 meshes, ultrasonically cleaning the substrate by absolute ethyl alcohol for 10-20min, ultrasonically cleaning the substrate by deionized water for 8-12min, and drying the substrate by nitrogen for later use; (2) Etching the surface of the platinum sheet treated in the step (1) by adopting a femtosecond laser etching technology, wherein the etching parameters are that the laser power is 10-15W, the scanning speed is 400-600mm/s, the etching depth is 15-25 mu m, the groove width is 40-60 mu m, the groove spacing is 40-60 mu m, a uniform grid-shaped groove structure is formed, and deionized water is used for ultrasonic cleaning for 4-6min after etching is finished, so that etching residues are removed; (3) Placing the etched platinum sheet into a sulfuric acid solution with the concentration of 0.4-0.6mol/L, activating by adopting a cyclic voltammetry, scanning the platinum sheet within the scanning range of-0.2-1.2V, and the scanning rate of 40-60mV/s, circulating for 20 circles, washing the platinum sheet cleanly by deionized water after the activation is finished, and drying by nitrogen to obtain the middle composite electrode; the bottom hydrophilic electrode was prepared as follows: (1) Taking a platinum sheet with the purity of more than or equal to 99.99 percent as a substrate, sequentially polishing the substrate to a mirror surface step by using silicon carbide sand paper with 800 meshes, 1200 meshes and 2000 meshes, ultrasonically cleaning the substrate by using acetone for 8-12min, ultrasonically cleaning the substrate by using absolute ethyl alcohol for 8-12min, ultrasonically cleaning the substrate by using deionized water for 8-12min, removing surface greasy dirt and impurities, and drying the substrate by using nitrogen for later use; (2) Immersing the pretreated platinum sheet in a hydrogen peroxide solution with the mass concentration of 20-40%, immersing the platinum sheet in the hydrogen peroxide solution at room temperature in a dark place for 25-35min to form a uniform PtO/PtO 2 mixed platinum oxidation hydrophilic layer on the surface of the platinum sheet, taking out the platinum sheet, and repeatedly washing the platinum sheet with deionized water to remove residual hydrogen peroxide; (3) Placing the platinum sheet subjected to the oxidation treatment in a 55-65 ℃ vacuum drying oven for drying for 1-2 hours, then soaking the platinum sheet in a phosphoric acid solution with the mass concentration of 80-90% at room temperature for 70-75 hours for aging treatment, taking out the platinum sheet, and then washing and drying the platinum sheet to ensure that the contact angle of the electrode surface is less than or equal to 30 degrees and the contact angle change after soaking is less than or equal to 5 degrees; The concentration detection unit comprises a working electrode II, a reference electrode II and an auxiliary electrode II, and the working electrode II is prepared as follows: (1) Mixing the multiwall carbon nanotube and the reduced graphene oxide according to the mass ratio of 1:1-3, adding deionized water, performing ultrasonic dispersion to form a suspension with the concentration of 1-3mg/mL, coating the suspension on the surface of a glassy carbon electrode by adopting a drop coating method, and drying for 1h at the temperature of 75-85 ℃ to obtain a substrate; (2) Placing a substrate in a bismuth nitrate solution with the concentration of 0.1mol/L, and adopting a constant potential deposition method to deposit for 10min at the potential of-0.6V to form a bismuth film with the thickness of 10-20 nm; (3) Dispersing sodium molybdate into chitosan solution with the mass concentration of 2-3% according to the proportion of 0.2-0.6mg/cm 2 , forming uniform slurry by ultrasonic dispersion, coating the slurry on the surface of a bismuth film by a spraying method, and crosslinking and curing for 1-2 hours at the temperature of 100 ℃ to prepare the working electrode II.
  2. 2. The colorimetric concentration detection sensor according to claim 1, further comprising a temperature compensation unit including a temperature sensor for compensating the reduction peak current signal detected by the colorimetric detection unit and the concentration detection unit based on a temperature-peak current correction formula of ; Wherein I corr is a corrected current, I meas is a measured current, α=0.003/° C is a temperature coefficient, T is a measured temperature, and T 0 =25 ℃ is a reference temperature.
  3. 3. The colorimetric concentration detection sensor according to claim 1, further comprising a control module, wherein the control module monitors that the impedance abnormality R is 200kΩ or R <500 Ω and the temperature exceeds 120 ℃, and real-time early warning is achieved, and the response time is less than or equal to 2s.
  4. 4. The use of the colorimetric versus concentration detection sensor according to claim 1 in phosphoric acid colorimetric, comparative and concentration detection.
  5. 5. The method of claim 4, wherein the concentration detection unit is used by setting one end of a working electrode II, a reference electrode II and an auxiliary electrode II in a phosphoric acid standard solution with concentration of 0-600 mu mol/L, detecting by a differential pulse voltammetry method with pH=3.0 acetic acid-sodium acetate buffer solution as a solvent, obtaining a reduction peak current of the phosphomolybdic heteropolyacid by using the parameters of 50ms of pulse width, 10mV/s of scanning speed and-0.2-1.0V of scanning voltage, drawing a standard curve of the phosphoric acid concentration by using the reduction peak current as an abscissa, obtaining a regression equation, determining a linear relation between the phosphoric acid concentration and the reduction peak current, placing a sample to be detected in an electrolytic cell, detecting by the method, obtaining a reduction peak current corresponding to phosphoric acid in the sample to be detected, substituting the regression equation, and calculating to obtain the phosphoric acid concentration in the sample to be detected.
  6. 6. The method of using a chromaticity detection unit according to claim 4, wherein the chromaticity detection unit is characterized in that an industrial refined phosphoric acid with a mass concentration of 85% is used as a solvent to prepare a standard solution with a concentration gradient of 0.1-5.0ppm of a solution of a chromogenic organic substance, the composition of the chromogenic organic substance and the mass percentage of 2-ethylhexyl phosphonic acid are 40% -50%, tributyl phosphate is 30% -40%, and phenylphosphonic acid is 10% -20%, one end of a working electrode I, one end of a reference electrode I and one end of an auxiliary electrode I are arranged in the standard solution, the working electrode I and one end of the auxiliary electrode I are detected by a differential pulse voltammetry, parameters are 50ms in pulse width, 10mV/s in scanning speed and 0-0.8V in scanning voltage, a reduction peak current of the chromogenic organic substance is obtained, the reduction peak current of phosphoric acid aqueous solutions with different concentrations is converted into a phosphoric acid Hazen chromaticity value, the phosphoric acid Hazen chromaticity value is used as an abscissa, a standard curve of phosphoric acid chromaticity is drawn, a linear relation between the phosphoric acid chromaticity and the reduction peak current is determined, a sample is placed in an electrolytic cell, the electrochemical sample to be detected by the method, the electrochemical sample to be detected by the regression peak is calculated by the regression detection station, and the corresponding phosphoric acid sample to be detected by the electrochemical sample to be detected.
  7. 7. The application of the detection unit according to claim 4, wherein the top hydrophobic electrode, the middle composite electrode and the bottom hydrophilic electrode are sequentially arranged in the sample to be detected from top to bottom, the distances between the three electrodes are the same, an impedance signal is obtained by detection using an alternating current impedance method, the impedance signal is automatically analyzed by an electrochemical workstation, the real part value R of the impedance is obtained by separation, the real part value R Top 、R In (a) 、R Bottom of the impedance is respectively obtained by the top hydrophobic electrode, the middle composite electrode and the bottom hydrophilic electrode, and the sample to be detected is obtained The method comprises the steps of setting a phase detection unit in a mixed solution of tributyl phosphate TBP and kerosene in a volume ratio of 1:1, adopting an alternating current impedance method to detect, scanning and taking a stable impedance real part value of a top hydrophobic electrode as R Organic compound , setting the phase detection unit in industrial refined phosphoric acid with a mass concentration of 50%, adopting the same alternating current impedance method to detect, scanning and taking a stable impedance real part value of a bottom hydrophilic electrode as R Phosphoric acid , and calculating the phase ratio according to the following formula : ; When the comparison is in the range of 0.17-0.5, the sample meets the production requirement.

Description

Chroma-compared concentration detection sensor and application thereof in phosphoric acid detection Technical Field The invention relates to the technical field of phosphoric acid detection, in particular to a phosphoric acid chromaticity ratio concentration detection sensor. Background The refined phosphoric acid is a key product in the phosphorus chemical industry and is widely applied to the fields of food, electronics, chemical fertilizers and the like. Phosphoric acid is prepared by a wet method by taking phosphate ore as a raw material, and a refined phosphoric acid product with the concentration of 85% is finally obtained through acidolysis, purification, refining, concentration and other series working sections, wherein the chromaticity, the phase ratio and the concentration of the refined phosphoric acid are core parameters for measuring the quality of the product and the stability of an extraction process. The chromaticity directly determines the grade of the product, the chromaticity is an visual index of the appearance and purity of phosphoric acid, the color-forming organic group exceeds the standard, the product is yellow, the food grade/electronic grade standard cannot be achieved, the market admittance and selling price are directly influenced, the decoloring process effect is reflected, and unqualified products are prevented from flowing into the downstream. The concentration is related to the suitability of the product to the application scene, and the concentration is not up to standard, so that the downstream application such as fertilizer production and electronic material preparation can be influenced, and meanwhile, the crystallization blockage caused by the too high concentration or the increase of the production cost due to the too low concentration can be avoided. Compared with the standard term in the chemical industry, the method refers to the volume ratio of one liquid phase to the other liquid phase in an extraction system, is generally expressed as A/O ratio, namely phosphoric acid phase volume/organic phase volume, in wet phosphoric acid extraction, is a key parameter for solvent extraction impurity removal, directly influences the impurity removal efficiency and the phosphoric acid recovery rate, and compared with detection, the method can truly reflect the current actual comparison of an extraction tank, once the detection result deviates from the process optimal interval, the detection result can be immediately adjusted, the detection result can be quickly pulled back to the optimal value, the phosphoric acid extraction and impurity separation are always in a high-efficiency stable state, and continuous expansion of extraction unbalance is avoided. If phase separation is slow, emulsification and interface turbidity occur during detection, the working section process can be immediately adjusted, and the deterioration of the full line working condition of the extraction tank is prevented. By detecting the entrainment quantity of the organic phase, the ageing and pollution degree of the circulating organic phase can be judged, the organic phase is timely arranged for cleaning and regenerating, the extraction efficiency of the circulating extractant is ensured, and the long-term stable operation of the working section is maintained. The traditional manual sampling has strong hysteresis, and compared with the traditional manual sampling, the organic phase is easy to excessively throw or run off along with the water phase after unbalance, and the traditional manual sampling has the advantages of avoiding the invalid consumption of the organic phase, reducing the waste of high-price extractant and directly reducing the raw material cost. Compared with the unbalance, the method can directly lead to incomplete impurity removal, generate unqualified phosphoric acid, need to return to the extraction working section for reworking, timely adjust the method, avoid unqualified products from the source, and save steam, water and electricity, labor and material loss required by reworking. The abnormal phase separation is found in time, so that the emulsion can be prevented from blocking a pipeline and corroding extraction equipment, the frequency and the cost of equipment overhaul and shutdown maintenance are reduced, and the effective operation time of the device is prolonged. The phase ratio is adjusted to an optimal value in time, so that impurities such as metal ions, fluorine, sulfur, organic matters and the like can be guaranteed to be extracted and separated efficiently, and the product can stably reach the industrial primary product, food grade and even electronic grade standard. The stability of the organic phase means that the entrainment quantity of the organic phase is stable, and yellowing and concentration fluctuation of the product caused by organic phase residue are avoided. Currently, in the industry, an off-line sampling mode is mostly adopted for detecting chromaticity,