Method for simultaneously determining bromide ion and iodide ion in medical waste water based on ion chromatography

Abstract

The present application relates to a kind of method for simultaneously determining bromide ion and iodide ion in medical waste based on ion chromatography, belong to analytical testing technical field.The present application carries out specific sequence processing to medical waste and adopts gradient elution ion chromatography, effectively removes the interfering substances such as microorganism, suspended matter, heavy metal, organic matter and chloride ion in medical waste, significantly improves the precision and sensitivity of bromide ion and iodide ion detection.At the same time, the method is simple, fast, can realize the simultaneous determination of bromide ion and iodide ion in medical waste, provides reliable technical support for the effective treatment and environmental monitoring of medical waste.In addition, by establishing standard curve, the concentration of bromide ion and iodide ion in the water sample to be measured can be accurately calculated, which provides a new pollutant index basis for medical waste quality evaluation.

Description

Technical Field

[0001] This invention relates to the field of analytical testing technology, and in particular to a method for simultaneously determining bromide and iodide ions in medical wastewater based on ion chromatography. Background Technology

[0002] Medical wastewater, as a source of urban sewage, poses a significant threat to the aquatic ecosystem, becoming a major factor endangering human life and health. Compared to industrial wastewater, medical wastewater is even more harmful. Medical wastewater contains certain amounts of bromides and iodides. Iodides primarily originate from iodine contrast agents used in diagnostic procedures, radioactive waste liquids from nuclear medicine departments, excrement from patients after ingesting radioactive isotopes during diagnosis and treatment, and cleaning water from washing patient medication cups, syringes, and pipettes used for dispensing high-intensity radioactive isotopes. Bromine in medical wastewater mainly comes from photographic processing room waste liquids, disinfectants, and some drug metabolites. Direct discharge of this bromide- and iodide-containing medical wastewater into natural water bodies will harm the aquatic environment and human health. Furthermore, bromides and iodides are emerging pollutant indicators for evaluating the quality of medical wastewater. Therefore, rapid and accurate determination of bromides and iodides in medical wastewater is crucial for environmental protection, monitoring, and remediation, ensuring drinking water safety, and effective treatment of medical wastewater.

[0003] Currently, the main methods for detecting bromides, both domestically and internationally, include X-ray fluorescence spectrometry, spectrophotometry, potentiometric analysis, voltammetry, ion chromatography, gas chromatography, and iodometric analysis. Methods for detecting iodides mainly include volumetric methods (hypochlorite method), spectrophotometry, ion chromatography, liquid chromatography, gas chromatography, electrochemical methods, flame atomic absorption spectrometry, ICP-AES, ICP-MS, neutron activation assay, and flow injection fluorescence quenching analysis. Ion chromatography, due to its advantages of short analysis time, high sensitivity, good selectivity, good stability, and low environmental pollution, is widely used in petrochemical, environmental monitoring, food and pharmaceutical, solid waste, hydrogeology, electronics, and public health fields. Because medical wastewater has a complex composition, and many of its components interfere with the determination of bromides and iodides, sample pretreatment is particularly important. The main components of medical wastewater include microorganisms, chlorides, suspended solids, ammonia ions, animal and vegetable oils, anionic surfactants, volatile phenols, total cyanide, and heavy metals such as cadmium, chromium, lead, silver, and mercury. Microorganisms, suspended solids, heavy metals, organic matter, and chloride ions can interfere with the determination of bromides and iodides. Summary of the Invention

[0004] In view of the above analysis, the present invention aims to provide a method for simultaneously determining bromide ions and iodide ions in medical wastewater based on ion chromatography, in order to solve at least one of the following problems in the prior art: no test method for bromide ions and iodide ions in medical wastewater is disclosed, and existing test methods for bromide ions and iodide ions in other wastewaters are not applicable to the detection of medical wastewater, resulting in low efficiency, low sensitivity, unreliable results, and high cost.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for simultaneously determining bromide and iodide ions in medical wastewater based on ion chromatography includes the following steps:

[0007] (1) The medical wastewater was subjected to flocculation treatment, residual chlorine removal treatment, filtration treatment, heavy metal removal treatment and organic matter removal treatment in sequence to obtain the water sample to be tested;

[0008] (2) Prepare a mixed standard solution of bromide ions and iodide ions, and establish a standard curve of bromide ions and iodide ions by gradient elution ion chromatography;

[0009] (3) Set up a gradient elution program, inject the water sample to be tested into the ion chromatograph for ion chromatography analysis, and obtain the peak area of ​​bromide ions and the peak area of ​​iodide ions;

[0010] (4) Calculate the concentration of bromide ions and the concentration of iodide ions based on the standard curve and the peak areas of bromide ions and iodide ions, respectively.

[0011] Furthermore, in step (1), the flocculation treatment involves sequentially adding chitosan flocculant and cationic polyacrylamide flocculant to the medical wastewater for treatment.

[0012] Furthermore, the chitosan flocculant is prepared by the following method: chitosan is added to an acetic acid solution and stirred for 2-4 hours to obtain the chitosan flocculant.

[0013] Furthermore, the cationic polyacrylamide flocculant is prepared by the following method: adding cationic polyacrylamide to water, stirring for 1-2 hours, and letting it stand for 0.5-1 hours to obtain the cationic polyacrylamide flocculant.

[0014] Furthermore, the volume ratio of medical wastewater to chitosan flocculant is 200:10~200:30.

[0015] Furthermore, in step (1), the residual chlorine removal treatment involves adding Na2S2O3 to the wastewater after flocculation treatment.

[0016] Furthermore, the concentration of Na2S2O3 in the wastewater is 3.0~4.0 g / L.

[0017] Furthermore, in step (1), the filtration process is performed using a filter membrane with a pore size of 0.22 μm;

[0018] The heavy metal removal process involves sequentially passing the filtered wastewater through a Na-type cation exchange column and an H-type cation exchange column.

[0019] The organic matter removal treatment involves passing the wastewater through a C18 solid-phase extraction column or an RP solid-phase extraction column.

[0020] Furthermore, in step (3), the eluent in the ion chromatography analysis is potassium hydroxide solution, the flow rate is 1.00 mL / min, the column temperature is 30.0℃, the conductivity cell temperature is 35.0℃, the constant suppressor current is 99 mA throughout the process, and the injection volume is 200 μL.

[0021] Furthermore, the eluent concentration was 15 mmol / L during the elution time of 0–12 min; the eluent concentration was increased from 15 mmol / L to 40 mmol / L during the elution time of 12–12.1 min; the eluent concentration was 40 mmol / L during the elution time of 12.1–28 min; and the eluent concentration was controlled at 15 mmol / L during the elution time of 28–34 min.

[0022] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0023] 1. This invention addresses medical wastewater through a specific sequential treatment method and employs gradient elution ion chromatography, effectively removing interfering substances such as microorganisms, suspended solids, heavy metals, organic matter, and chloride ions. This significantly improves the accuracy and sensitivity of bromide and iodide ion detection. Furthermore, the method is simple and rapid, enabling simultaneous determination of bromide and iodide ions in medical wastewater, providing reliable technical support for effective treatment and environmental monitoring of medical wastewater. In addition, by establishing a standard curve, the concentrations of bromide and iodide ions in the test sample can be accurately calculated, providing a new pollutant indicator for evaluating the quality of medical wastewater.

[0024] 2. The present invention first adds chitosan flocculant and then cationic polyacrylamide flocculant in sequence, which can give full play to the synergistic effect of the two flocculants, and remove suspended solids, microorganisms and other interfering substances in medical wastewater more efficiently, providing a purer water sample for subsequent ion chromatography analysis, thereby improving the precision and accuracy of bromide and iodide ion detection.

[0025] 3. The method of this invention effectively removes interfering substances such as microorganisms, suspended solids, and heavy metals from medical wastewater. The precision RSD of bromide and iodide ions is less than 4%, and the spiked recovery rate is between 90% and 100.6%. It extends the analytical column life (capable of analyzing 2000-3000 samples) and reduces detection costs.

[0026] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0027] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0028] Figure 1 This is a standard curve of bromide ions;

[0029] Figure 2 This is a standard curve for iodine ions. Detailed Implementation

[0030] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0031] A specific embodiment of the present invention discloses a method for simultaneously determining bromide ions and iodide ions in medical wastewater based on ion chromatography, comprising the following steps:

[0032] (1) The medical wastewater was subjected to flocculation treatment, residual chlorine removal treatment, filtration treatment, heavy metal removal treatment and organic matter removal treatment in sequence to obtain the water sample to be tested;

[0033] (2) Prepare a mixed standard solution of bromide ions and iodide ions, and establish a standard curve of bromide ions and iodide ions by gradient elution ion chromatography;

[0034] (3) Set up a gradient elution program, inject the water sample to be tested into the ion chromatograph for ion chromatography analysis, and obtain the peak area of ​​bromide ions and the peak area of ​​iodide ions;

[0035] (4) Calculate the concentration of bromide ions and the concentration of iodide ions based on the standard curve and the peak areas of bromide ions and iodide ions, respectively.

[0036] Compared with existing technologies, this invention, through a specific sequential treatment of medical wastewater and the use of gradient elution ion chromatography, effectively removes interfering substances such as microorganisms, suspended solids, heavy metals, organic matter, and chloride ions from medical wastewater, significantly improving the accuracy and sensitivity of bromide and iodide ion detection. Simultaneously, this method is simple and rapid to operate, enabling simultaneous determination of bromide and iodide ions in medical wastewater, providing reliable technical support for the effective treatment and environmental monitoring of medical wastewater. Furthermore, by establishing a standard curve, the concentrations of bromide and iodide ions in the test sample can be accurately calculated, providing a new pollutant indicator basis for the quality evaluation of medical wastewater.

[0037] Specifically, in step (1), the flocculation treatment involves sequentially adding chitosan flocculant and cationic polyacrylamide flocculant to the medical wastewater for treatment.

[0038] Preferably, the chitosan flocculant is prepared by the following method: adding chitosan to an acetic acid solution and stirring for 2-4 hours, for example, 2 hours, 2.2 hours, 2.4 hours, 2.6 hours, 2.8 hours, 3.0 hours, 3.2 hours, 3.4 hours, 3.6 hours, 3.8 hours, or 4 hours, to obtain the chitosan flocculant.

[0039] More preferably, the acetic acid solution is an aqueous solution of acetic acid with a volume fraction of 1-3% (e.g., 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, 2.2%, 2.4%, 2.6%, 2.8%), and the chitosan in the aqueous acetic acid solution has a mass concentration of 0.5-1 g / L, for example, 0.5 g / L, 0.6 g / L, 0.7 g / L, 0.8 g / L, 0.9 g / L, 1 g / L.

[0040] Preferably, the cationic polyacrylamide flocculant is prepared by the following method: adding cationic polyacrylamide to water and stirring for 1-2 hours, for example, 1 hour, 1.2 hours, 1.4 hours, 1.6 hours, 1.8 hours, or 2 hours, and then letting it stand for 0.5-1 hours, for example, 0.5 hours, 0.6 hours, 0.7 hours, 0.8 hours, 0.9 hours, or 1 hour, to obtain the cationic polyacrylamide flocculant.

[0041] More preferably, the cationic polyacrylamide has a mass concentration of 0.1~0.5 g / L in water, for example, 0.1 g / L, 0.2 g / L, 0.3 g / L, 0.4 g / L, or 0.5 g / L.

[0042] Specifically, in step (1), the volume ratio of medical wastewater to chitosan flocculant is 200:10 to 200:30, for example, 200:10, 200:12, 200:14, 200:16, 200:18, 200:20, 200:22, 200:24, 200:26, 200:28, 200:30.

[0043] Preferably, after adding chitosan flocculant, the mixture is stirred at a stirring rate of 180-200 rpm (e.g., 180 rpm, 182 rpm, 184 rpm, 186 rpm, 188 rpm, 190 rpm, 192 rpm, 194 rpm, 196 rpm, 198 rpm, 200 rpm) for 1-3 min, e.g., 1 min, 1.2 min, 1.4 min, 1.6 min, 1.8 min, 2 min, 2.2 min, 2.4 min, 2.6 min, 2.8 min, 3 min, and then the stirring rate is reduced to 40-60 rpm (e.g., 40 rpm, 42 rpm, 44 rpm, 46 rpm, 48 rpm, 50 rpm, 52 rpm, 54 rpm, 56 rpm, 58 rpm, 60 rpm) for 10-20 min (e.g., 10 min, 12 min, 14 min, 16 min, 18 min, 20 min), centrifuged, allowed to stand for 10 min, centrifuged again, and the supernatant is collected.

[0044] Preferably, the volume ratio of the supernatant to the cationic polyacrylamide flocculant is 200:2 to 200:5, for example, 200:2, 200:3, 200:4, or 200:5.

[0045] More preferably, after adding the cationic polyacrylamide flocculant, the mixture is stirred at a stirring rate of 180-200 rpm (e.g., 180 rpm, 182 rpm, 184 rpm, 186 rpm, 188 rpm, 190 rpm, 192 rpm, 194 rpm, 196 rpm, 198 rpm, 200 rpm) for 1-2 min, e.g., 1 min, 1.2 min, 1.4 min, 1.6 min, 1.8 min, 2 min, then the stirring rate is reduced to 40-60 rpm (e.g., 40 rpm, 42 rpm, 44 rpm, 46 rpm, 48 rpm, 50 rpm, 52 rpm, 54 rpm, 56 rpm, 58 rpm, 60 rpm) for 10-15 min, e.g., 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, then allowed to stand for 10 min, centrifuged, and the supernatant is collected.

[0046] This invention targets the flocculation treatment of medical wastewater, employing specific flocculants and a specific sequence, primarily based on the characteristics of different flocculants and the properties of pollutants in medical wastewater. Chitosan flocculant carries a positive charge, enabling it to neutralize negatively charged suspended solids, microorganisms, and other pollutants in medical wastewater, causing them to destabilize and aggregate into larger flocs.

[0047] This invention first adds chitosan flocculant to initially remove most of the suspended solids and microorganisms in wastewater, reducing the burden on subsequent treatment. Cationic polyacrylamide flocculant is a high-molecular polymer with a long-chain structure, which can act as a bridge between the already formed flocs, allowing the flocs to grow larger and denser, thus facilitating sedimentation and separation. Adding cationic polyacrylamide flocculant to the supernatant after chitosan flocculant treatment can more effectively remove residual fine suspended solids and colloidal substances, improving the clarity of the water sample.

[0048] Therefore, the present invention first adds chitosan flocculant and then cationic polyacrylamide flocculant in sequence, which can give full play to the synergistic effect of the two flocculants, and remove suspended solids, microorganisms and other interfering substances in medical wastewater more efficiently, providing a purer water sample for subsequent ion chromatography analysis, thereby improving the precision and accuracy of bromide and iodide ion detection.

[0049] Specifically, in step (1), the residual chlorine removal treatment involves adding Na2S2O3 to the wastewater after flocculation treatment. Preferably, the concentration of Na2S2O3 in the wastewater is 3.0~4.0 g / L, for example, 3.0 g / L, 3.1 g / L, 3.2 g / L, 3.3 g / L, 3.4 g / L, 3.5 g / L, 3.6 g / L, 3.7 g / L, 3.8 g / L, 3.9 g / L, or 4 g / L.

[0050] Specifically, in step (1), the filtration process is performed using a filter membrane with a pore size of 0.22 μm;

[0051] The heavy metal removal process involves sequentially passing the filtered wastewater through a Na-type cation exchange column and an H-type cation exchange column.

[0052] The organic matter removal treatment involves passing the wastewater through a C18 solid-phase extraction column or an RP solid-phase extraction column.

[0053] It should be noted that gradient elution, also known as gradient elution, in this invention refers to a method of effectively separating samples by continuously adjusting the concentration of the elution solution within the same analysis cycle.

[0054] Specifically, in step (3), the eluent in the ion chromatography analysis is potassium hydroxide solution, the flow rate is 1.00 mL / min, the column temperature is 30.0℃, the conductivity cell temperature is 35.0℃, the constant suppressor current is 99 mA, and the injection volume is 200 μL.

[0055] Preferably, the eluent concentration is 15 mmol / L when the elution time is 0–12 min; the eluent concentration is increased from 15 mmol / L to 40 mmol / L when the elution time is 12–12.1 min; the eluent concentration is 40 mmol / L when the elution time is 12.1–28 min; and the eluent concentration is controlled at 15 mmol / L when the elution time is 28–34 min.

[0056] This invention employs gradient elution ion chromatography to simultaneously determine bromide and iodide ions in medical wastewater. The method has a wide linear range, low detection limit, high sensitivity, and is free from interference by common anions in water, resulting in stable and reliable results.

[0057] The technical solution of the present invention will be further explained below with reference to specific embodiments.

[0058] The raw materials or devices involved in the following examples and comparative examples are explained using the following manufacturers and brands. However, the present invention is not limited to these, and other manufacturers and brands may also be used. The manufacturer of cationic polyacrylamide is Shanghai Maclean Biochemical Technology Co., Ltd., CAS: 9003-05-8; the manufacturer of chitosan is Shandong Haiyihua Biotechnology Co., Ltd., CAS: 9012-76-4; the manufacturer of Na-type cation exchange column is Thermo Fisher Scientific, model: Dionex OnGuard II Na column (062962); the manufacturer of H-type cation exchange column is Thermo Fisher Scientific, model: Dionex OnGuard II H column (057086); the manufacturer of C18 solid phase extraction column is Amicrom, model: AM-IC-C1825; the manufacturer of RP solid phase extraction column is Thermo Fisher Scientific, model: Dionex OnGuard II RP column (057084). The medical wastewater in the following examples and comparative examples was taken from the medical wastewater of a general hospital.

[0059] Example 1

[0060] A method for simultaneously determining bromide and iodide ions in medical wastewater based on ion chromatography includes the following steps:

[0061] (1) The medical wastewater was subjected to flocculation treatment, residual chlorine removal treatment, filtration treatment, heavy metal removal treatment and organic matter removal treatment in sequence to obtain the water sample to be tested;

[0062] Specifically, chitosan is added to a 1% (v / v) acetic acid solution, the mass concentration of chitosan in the acetic acid aqueous solution is 0.5 g / L, and stirred for 2 h to obtain the chitosan flocculant; cationic polyacrylamide is added to water, the mass concentration of cationic polyacrylamide in the water is 0.1 g / L, stirred for 1 h, and allowed to stand for 0.5 h to obtain the cationic polyacrylamide flocculant;

[0063] The flocculation treatment involves adding chitosan flocculant to the medical wastewater at a volume ratio of 200:10. After adding the chitosan flocculant, the mixture is stirred at 180 rpm for 1 minute, then the stirring speed is reduced to 40 rpm for 10 minutes. The mixture is then allowed to stand for 10 minutes, centrifuged, and the supernatant is collected. Cationic polyacrylamide flocculant is added to the supernatant for further treatment; the volume ratio of the supernatant to the cationic polyacrylamide flocculant is 200:2.

[0064] The residual chlorine removal treatment involves adding Na2S2O3 to the wastewater after flocculation treatment, with the concentration of Na2S2O3 in the wastewater being 3.0 g / L.

[0065] The filtration process is performed using a filter membrane with a pore size of 0.22 μm.

[0066] The heavy metal removal process involves sequentially passing the filtered wastewater through a Na-type cation exchange column and an H-type cation exchange column.

[0067] The organic matter removal treatment involves passing the wastewater through a C18 solid-phase extraction column to obtain a water sample for testing.

[0068] (2) Prepare a mixed standard solution of bromide ions and iodide ions, and establish a standard curve of bromide ions and iodide ions by gradient elution ion chromatography, specifically including the following:

[0069] The bromine standard solution has a concentration of 100 mg / L and is produced by Beijing Beifang Weiye Metrology Technology Research Institute; the iodine standard solution has a concentration of 100 mg / L and is also produced by Beijing Beifang Weiye Metrology Technology Research Institute.

[0070] (2a) Preparation of bromine standard solution

[0071] Take 10 ml of 100 mg / L bromine standard solution and dilute to 100 ml to obtain a 10 mg / L bromine standard solution.

[0072] Take 10 ml of bromine standard solution and dilute to 100 ml to obtain a 1 mg / L bromine standard solution.

[0073] Take 5 ml of 10 mg / L bromine standard solution and dilute to 100 ml to obtain 0.5 mg / L bromine standard solution.

[0074] Take 5 ml of 1 mg / L bromine standard solution and dilute to 100 ml, 2 ml and 10 ml respectively to obtain 0.05 mg / L, 0.02 mg / L and 0.1 mg / L bromine standard solutions.

[0075] Take 10 ml of 0.1 g / ml bromine standard solution and dilute to 100 ml to obtain 0.01 mg / L bromine standard solution.

[0076] (2b) Preparation of iodine standard solution

[0077] Take 10 ml of 100 mg / L iodine standard solution and dilute to 100 ml to obtain a 10 mg / L iodine standard solution.

[0078] Take 10 ml of iodine standard solution and dilute to 100 ml to obtain a 1 mg / L iodine standard solution.

[0079] Take 5 ml of 10 mg / L iodine standard solution and dilute to 100 ml to obtain 0.5 mg / L iodine standard solution.

[0080] Take 5 ml of 1 mg / L iodine standard solution and dilute it to 100 ml, 2 ml and 10 ml respectively to obtain 0.05 mg / L, 0.02 mg / L and 0.1 mg / L iodine standard solutions.

[0081] Take 10 ml of 0.1 g / ml iodine standard solution and dilute to 100 ml to obtain 0.01 mg / L iodine standard solution.

[0082] (2c) Preparation of a mixed standard solution of bromide and iodide ions

[0083] Take 10 mL of 100 mg / L iodine standard solution and 10 mL of 100 mg / L bromine standard solution, and dilute to 100 mL to obtain a 10 mg / L bromine and iodine mixed standard solution.

[0084] Take 10 mL of the mixed standard solution and dilute it to 100 mL to obtain a 1 mg / L mixed standard solution.

[0085] Take 5 mL of the 10 mg / L mixed standard solution and dilute to 100 mL to obtain a 0.5 mg / L mixed standard solution.

[0086] Take 5 mL of the 1 mg / L mixed standard solution and dilute it to 100 mL, 2 mL and 10 mL respectively to obtain 0.05 mg / L, 0.02 mg / L and 0.1 mg / L mixed standard solutions.

[0087] Take 10 mL of the 0.1 mg / mL mixed standard solution and dilute to 100 mL to obtain a 0.01 mg / L mixed standard solution.

[0088] (2d) Take the mixed standard solution of bromide ions and iodide ions from (2c) and dilute it to prepare a series of mixed standard solutions with concentrations of 0.01, 0.02, 0.05, 0.1, 0.5, 1.0, and 2.0 mg / L. Inject the solutions sequentially in ascending order of concentration. Plot the linear regression equation with peak area (μS·min) on the ordinate and ion concentration (mg / L) on the abscissa, and then plot the standard curve. The linear regression equation is shown in Table 1, and the standard curve is shown in Table 2. Figure 1 and Figure 2 .

[0089] Table 1. Linear equations and correlation coefficients for bromide and iodide ions.

[0090]

[0091] According to Table 1, the linear equation for bromide ions is Y = 1.1016X, with a correlation coefficient of 0.99991; the linear equation for iodide ions is Y = 0.6599X, with a correlation coefficient of 0.99960.

[0092] (3) Set up a gradient elution program, inject the water sample to be tested into the ion chromatograph for ion chromatography analysis, and obtain the peak area of ​​bromide ions and the peak area of ​​iodide ions;

[0093] In the ion chromatography analysis, the eluent is potassium hydroxide solution, the flow rate is 1.00 mL / min, the column temperature is 30.0℃, the conductivity cell temperature is 35.0℃, the constant suppressor current is 99 mA, and the injection volume is 200 μL.

[0094] The eluent concentration was 15 mmol / L during the elution time of 0–12 min; the eluent concentration was increased from 15 mmol / L to 40 mmol / L during the elution time of 12–12.1 min; the eluent concentration was 40 mmol / L during the elution time of 12.1–28 min; and the eluent concentration was controlled at 15 mmol / L during the elution time of 28–34 min.

[0095] (4) Calculate the concentration of bromide ions and the concentration of iodide ions based on the standard curve and the peak areas of bromide ions and iodide ions, respectively.

[0096] Example 2

[0097] A method for simultaneously determining bromide and iodide ions in medical wastewater based on ion chromatography is similar to that in Example 1, except that in step (1), chitosan is added to an acetic acid solution with a volume fraction of 2% and the mass concentration of chitosan in the acetic acid aqueous solution is 0.75 g / L. The mixture is stirred for 3 h to obtain the chitosan flocculant. Cationic polyacrylamide is added to water with a mass concentration of 0.25 g / L and the mixture is stirred for 1.5 h and allowed to stand for 0.75 h to obtain the cationic polyacrylamide flocculant.

[0098] The flocculation treatment involves adding chitosan flocculant to the medical wastewater at a volume ratio of 200:20. After adding the chitosan flocculant, the mixture is stirred at 190 rpm for 2 minutes, then the stirring speed is reduced to 50 rpm for 15 minutes. The mixture is then allowed to stand for 10 minutes, centrifuged, and the supernatant is collected. Cationic polyacrylamide flocculant is added to the supernatant for further treatment; the volume ratio of the supernatant to the cationic polyacrylamide flocculant is 200:2.5.

[0099] The residual chlorine removal treatment involves adding Na2S2O3 to the wastewater after flocculation treatment, with the concentration of Na2S2O3 in the wastewater being 4.0 g / L.

[0100] Example 3

[0101] A method for simultaneously determining bromide and iodide ions in medical wastewater based on ion chromatography is similar to that in Example 1, except that in step (1), chitosan is added to an acetic acid solution with a volume fraction of 3% and a mass concentration of 1 g / L in the acetic acid aqueous solution, and stirred for 4 h to obtain the chitosan flocculant; cationic polyacrylamide is added to water with a mass concentration of 0.5 g / L in the water, stirred for 2 h, and allowed to stand for 1 h to obtain the cationic polyacrylamide flocculant;

[0102] The flocculation treatment involves adding chitosan flocculant to the medical wastewater at a volume ratio of 200:30. After adding the chitosan flocculant, the mixture is stirred at 200 rpm for 3 minutes, then the stirring speed is reduced to 60 rpm for 20 minutes. The mixture is then allowed to stand for 10 minutes, centrifuged, and the supernatant is collected. Cationic polyacrylamide flocculant is added to the supernatant for further treatment; the volume ratio of the supernatant to the cationic polyacrylamide flocculant is 200:5.

[0103] The residual chlorine removal treatment involves adding Na2S2O3 to the wastewater after flocculation treatment, with the concentration of Na2S2O3 in the wastewater being 3.5 g / L.

[0104] Comparative Example 1

[0105] The method for simultaneously determining bromide and iodide ions in medical wastewater based on ion chromatography in this comparative example is similar to that in Example 1, except that chitosan flocculant is not added during the flocculation treatment in step (1).

[0106] Comparative Example 2

[0107] The method for simultaneously determining bromide and iodide ions in medical wastewater based on ion chromatography in this comparative example is similar to that in Example 1, except that cationic polyacrylamide flocculant is not added during the flocculation treatment in step (1).

[0108] Comparative Example 3

[0109] The method for simultaneously determining bromide and iodide ions in medical wastewater based on ion chromatography in this comparative example is similar to that in Example 1, except that in step (1), cationic polyacrylamide flocculant is added first, followed by chitosan flocculant during flocculation treatment.

[0110] Comparative Example 4

[0111] The method for simultaneously determining bromide and iodide ions in medical wastewater based on ion chromatography in this comparative example is similar to that in Example 1, except that in step (1), filtration is performed first, followed by removal of residual chlorine.

[0112] Comparative Example 5

[0113] The method for simultaneously determining bromide and iodide ions in medical wastewater based on ion chromatography in this comparative example is similar to that in Example 1, except that in step (1), after adding chitosan flocculant, the mixture is stirred at a stirring rate of 220 rpm for 15 min, allowed to stand for 10 min, centrifuged, and the supernatant is taken.

[0114] Comparative Example 6

[0115] The method for simultaneously determining bromide and iodide ions in medical wastewater based on ion chromatography in this comparative example is similar to that in Example 1, except that in step (1), Na2S2O3 is replaced with ascorbic acid in the residual chlorine removal treatment.

[0116] Comparative Example 7

[0117] The method for simultaneously determining bromide and iodide ions in medical wastewater based on ion chromatography in this comparative example is similar to that in Example 1, except that in steps (2) and (3), gradient elution is replaced with isocratic elution, that is, the concentration of the eluent remains unchanged throughout the elution process, i.e., the concentration of the eluent is 15.00 mmol / L when determining bromide ions and 40.00 mmol / L when determining iodide ions.

[0118] Test Example 1: Reliability test to verify the method of Example 1

[0119] (1) Limit of detection and limit of determination

[0120] The method detection limit refers to the minimum concentration or minimum content of an analyte that a specific analytical method can quantitatively detect in a sample within a given confidence level.

[0121] According to the requirements for detection limit determination in the "Water Environment Monitoring Standard" (SL219-2013), blank tests were conducted, with one batch (2 blank values) measured daily for 10 consecutive days. Since bromide and iodide ions were not detected in the blank test using pure water, according to the "Technical Guidelines for the Development of Environmental Monitoring Analytical Methods Standards" (HJ 168-2020), pure water must be spiked with a standard working solution, and the spiked concentration should be 2-5 times the estimated method detection limit. The "Water Quality Inorganic Anions (F... - Cl - NO2 - ,Br - NO3 - PO4 3- SO3 2- SO4 2- The determination of Br by ion chromatography (HJ84-2016) - The detection limit is 0.016 mg / L. This is according to the "Determination of Iodide in Water by Ion Chromatography" (HJ 778-2015). - The detection limit is 0.002 mg / L. Therefore, a mixed blank spiking solution of 0.032 mg / L bromide ions and 0.004 mg / L iodide ions was prepared, and 10 batches were tested consecutively. The detection limit was calculated using the following formula:

[0122] MDL = t (n-1,0.99) × S

[0123] Where: MDL—method detection limit.

[0124] n—the number of times the sample is tested.

[0125] S—Standard deviation of the sample,

[0126] t—a one-sided t-distribution with n-1 degrees of freedom and a confidence level of 99%.

[0127] Table 2. Detection limits and lower limits of quantification for bromide and iodide ions.

[0128]

[0129] As shown in Table 2, within a 99% confidence level, the detection limits for bromide ions and iodide ions of this method are 0.0045 and 0.0018, respectively, and the quantitation limits are 0.013 and 0.005, respectively. In summary, this method has low detection limits and quantitation limits, indicating good method sensitivity.

[0130] (2) Accuracy determination

[0131] The method described in Example 1 was used to analyze three water samples, with six parallel measurements performed. The average value of the sample concentration was calculated, and the samples were spiked at 100% of the actual spiking amount to calculate the recovery rate. The data are shown in Tables 3 and 4.

[0132] Table 3 Br - Spiked recovery values

[0133]

[0134] Table 4 I - Spiked recovery values

[0135]

[0136] Tables 3 and 4 show that the recoveries of bromide ions were 90.0%–100.2%, and the recoveries of iodide ions were 90.3%–100.6%. According to the "Water Environment Monitoring Standard" (SL219-2013), the instrument recovery rate should be controlled between 90% and 110%. The recoveries of both ions fall within this range, indicating that this method is suitable for determining Br in actual water samples. - I - The method is accurate and reliable.

[0137] (3) Determination of method precision

[0138] Method precision refers to the degree of consistency among independent test results under specified conditions. It reflects the stability of the method and is usually expressed as relative standard deviation.

[0139] Three standard samples with different concentrations (high, medium, and low) were selected, and each sample was measured in parallel six times. The average value, standard deviation, and relative standard deviation were calculated. The results are shown in Tables 5 and 6.

[0140] Table 5. Precision test data for bromide ions

[0141]

[0142] Table 6. Precision test data for iodine ions

[0143]

[0144] As shown in Tables 5 and 6, the RSDs of bromide ions and iodide ions are as follows: Br - : 1.14%~2.41%, I - The RSDs for both bromide and iodide ions were less than 4%, indicating that the method has high precision and good stability.

[0145] The same experiments were also conducted on other embodiments of the present invention, and the results were basically the same. Due to space limitations, they will not be listed one by one.

[0146] Experimental Example 2

[0147] The samples were processed according to the method in Example 1, and approximately 2,000 to 3,000 samples were analyzed per analytical column.

[0148] (1) When the sample was treated according to Comparative Example 1, no chitosan flocculant was added during the flocculation treatment; only cationic polyacrylamide flocculant was added. Suspended matter was still visible in the treated sample, and the sample was slightly turbid. The pretreated sample was directly introduced into the ion chromatograph for analysis. During the analysis, the analytical column was easily clogged, leading to a decrease in column efficiency, an increase in column pressure, and a significant reduction in the number of samples analyzed per column. Approximately 100-500 samples were analyzed per column, increasing the cost of sample analysis. When medical wastewater was treated according to Comparative Example 1 and then analyzed in the ion chromatograph, impurity peaks interfered with the bromide ion peak, resulting in a lower bromide ion measurement result; in some cases, impurity peaks even masked the bromide ion peak, making it impossible to measure bromide ions. Samples were treated using the methods of Example 1 and Comparative Example 1, respectively. The bromide ion spiked recovery rate in Example 1 was 99.3%, while the bromide ion spiked recovery rate in Comparative Example 1 was 88.9%. The experimental results clearly show that the spiked recovery rate was lower when the sample was treated according to Comparative Example 1, indicating inaccurate sample measurement.

[0149] (2) When samples were treated according to Comparative Example 2, no cationic polyacrylamide flocculant was added during flocculation treatment; only chitosan flocculant was added. Even after treatment, a small amount of organic matter and colloids remained in the samples. Directly introducing the pretreated samples into the ion chromatograph for analysis easily clogged the analytical column, leading to decreased column efficiency, increased column pressure, and a significant reduction in the number of samples that could be analyzed per column (approximately 100-300 samples per column), thus increasing the cost of analysis. Some samples treated according to Comparative Example 2 and then analyzed in the ion chromatograph resulted in excessive column pressure, even damaging the instrument, making sample analysis impossible.

[0150] (3) The samples were treated according to Comparative Example 3. During the flocculation treatment, cationic polyacrylamide flocculant was added first, followed by chitosan flocculant to flocculate the samples. After treatment, a small amount of suspended matter, organic matter, and colloids were visible in the samples, and the samples were turbid. The pretreated samples were directly introduced into the ion chromatograph for determination. During the determination process, the analytical column was easily blocked, resulting in a decrease in column efficiency, an increase in column pressure, a significant reduction in the number of samples measured by the column, and even column pressure overpressure, instrument damage, and inability to determine the samples. The samples were treated according to Comparative Example 3 and Example 1, respectively. The bromide ion spiked recovery rate in Example 1 was 99.3%, while the bromide ion spiked recovery rate in Comparative Example 3 was 72.3%. The experimental results clearly show that the spiked recovery rate of the samples treated according to Comparative Example 3 was seriously low, and the sample determination was inaccurate.

[0151] (4) The samples were processed according to Comparative Example 4, first by filtration and then by dechlorination. New impurities, ions, or precipitates may be generated during dechlorination. Samples with precipitates entering the instrument directly will clog the analytical column, significantly reducing the number of samples measured and increasing the cost. Using the method of this invention, approximately 2000-3000 samples can be measured per analytical column; using Comparative Example 4, approximately 100-200 samples can be measured per column. The sample processing according to Comparative Example 4 generates new impurities, leading to a higher sample recovery rate and inaccurate method determination. Samples were processed according to Comparative Example 4 and Example 1 respectively. The bromide ion spiked recovery rate in Example 1 was 99.3%, while the bromide ion spiked recovery rate in Comparative Example 4 was 115.2%. The experimental results clearly show that the spiked recovery rate was higher when samples were processed according to Comparative Example 4, resulting in inaccurate sample determination.

[0152] (5) When the samples were treated according to Comparative Example 5, after adding chitosan flocculant, the mixture was stirred at a stirring rate of 220 rpm for 15 min. However, this high-speed stirring alone made it difficult for the initially agglomerated particles to collide sufficiently to form larger flocs, resulting in incomplete flocculation. The pretreated samples were then directly introduced into the ion chromatograph for analysis. During the analysis, the analytical column was easily clogged, leading to a decrease in column efficiency, an increase in column pressure, and a significant reduction in the number of samples that could be analyzed per column (approximately 50-100 samples). This increased the cost of sample analysis. Some samples treated according to Comparative Example 5 were then introduced into the ion chromatograph for analysis, resulting in column pressure overpressure and even instrument damage, making sample analysis impossible.

[0153] (6) The sample was treated according to Comparative Example 6, in which Na2S2O3 was replaced with ascorbic acid in the residual chlorine removal treatment. The medical wastewater contained a large amount of iodine (elemental iodine). Ascorbic acid readily reacts with elemental iodine, introducing iodide ions. The original sample was not treated with residual chlorine, and the iodide ion concentration was determined using the method of "Determination of Iodides in Water by Ion Chromatography" (HJ 778-2015), with a concentration of approximately 0.7839 mg / L. The sample was treated according to the method of Example 1, and the iodide ion concentration was determined using the same method, with a concentration of approximately 0.7588 mg / L, which was close to the original data. The sample was treated according to Comparative Example 6, and the iodide ion concentration was determined using the same method, with a concentration of approximately 1.3147 mg / L, which was significantly higher than the original result.

[0154] (7) According to Comparative Example 7, if the eluent concentration is 15.00 mmol / L, both bromide and iodide ions can be eluted and measured, but the measurement time for both ions is 1 hour and 30 minutes. If the eluent concentration is 40.00 mmol / L, the bromide peak overlaps with the chloride peak, making it impossible to measure bromide ions and thus impossible to measure both ions at once. If the two ions are eluted separately, i.e., the eluent concentration is set to 15.00 mmol / L when measuring bromide ions and 40.00 mmol / L when measuring iodide ions, then two samplings, two injections, and two measurements are required, which is not only time-consuming and labor-intensive, but also increases the consumption of pretreatment and analytical columns.

[0155] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for simultaneously determining bromide and iodide ions in medical wastewater based on ion chromatography, characterized in that, Includes the following steps: (1) The medical wastewater was subjected to flocculation treatment, residual chlorine removal treatment, filtration treatment, heavy metal removal treatment and organic matter removal treatment in sequence to obtain the water sample to be tested; The flocculation treatment involves sequentially adding chitosan flocculant and cationic polyacrylamide flocculant to the medical wastewater for treatment. The volume ratio of medical wastewater to chitosan flocculant is 200:10~200:30; After adding chitosan flocculant, stir at a stirring speed of 180-200 rpm for 1-3 min, reduce the stirring speed to 40-60 rpm and stir for 10-20 min, centrifuge, let stand for 10 min, centrifuge again, and collect the supernatant; after adding cationic polyacrylamide flocculant, stir at a stirring speed of 180-200 rpm for 1-2 min, reduce the stirring speed to 40-60 rpm and stir for 10-15 min, let stand for 10 min, centrifuge again, and collect the supernatant. The residual chlorine removal treatment involves adding Na2S2O3 to the wastewater after flocculation treatment; The filtration process is performed using a filter membrane with a pore size of 0.22 μm. The heavy metal removal process involves sequentially passing the filtered wastewater through a Na-type cation exchange column and an H-type cation exchange column. The organic matter removal treatment involves treating the wastewater by passing it through a C18 solid-phase extraction column or an RP solid-phase extraction column. (2) Prepare a mixed standard solution of bromide ions and iodide ions, and establish a standard curve of bromide ions and iodide ions by gradient elution ion chromatography; (3) Set up a gradient elution program, inject the water sample to be tested into the ion chromatograph for ion chromatography analysis, and obtain the peak area of ​​bromide ions and the peak area of ​​iodide ions; In the ion chromatography analysis, the eluent is potassium hydroxide solution, the flow rate is 1.00 mL / min, the column temperature is 30.0℃, the conductivity cell temperature is 35.0℃, the constant suppressor current is 99 mA, and the injection volume is 200 μL. The eluent concentration was 15 mmol / L during the elution time of 0–12 min; the eluent concentration was increased from 15 mmol / L to 40 mmol / L during the elution time of 12–12.1 min; the eluent concentration was 40 mmol / L during the elution time of 12.1–28 min; and the eluent concentration was controlled at 15 mmol / L during the elution time of 28–34 min. (4) Calculate the concentrations of bromide ions and iodide ions based on the standard curve and the peak areas of bromide ions and iodide ions, respectively; The precision RSDs for both bromide and iodide ions were less than 4%, and the recoveries ranged from 90% to 100.6%. The limits of detection for bromide and iodide ions were 0.0045 mg / L and 0.0018 mg / L, respectively.

2. The method for simultaneously determining bromide and iodide ions in medical wastewater based on ion chromatography according to claim 1, characterized in that, The chitosan flocculant is prepared by the following method: chitosan is added to an acetic acid solution and stirred for 2-4 hours to obtain the chitosan flocculant.

3. The method for simultaneously determining bromide and iodide ions in medical wastewater based on ion chromatography according to claim 1, characterized in that, The cationic polyacrylamide flocculant is prepared by the following method: adding cationic polyacrylamide to water, stirring for 1-2 hours, and letting it stand for 0.5-1 hours to obtain the cationic polyacrylamide flocculant.

4. The method for simultaneously determining bromide and iodide ions in medical wastewater based on ion chromatography according to claim 1, characterized in that, The concentration of Na2S2O3 in the wastewater is 3.0~4.0 g / L.

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