A method for detecting the removal effect of PFASs by a water purifier

Abstract

The present invention discloses a method for detecting the removal effect of PFASs by a water purifier, comprising the following steps: 1) dissolving PFOA and PFOS in methanol to obtain PFOA stock solution and PFOS stock solution; 2) respectively absorbing PFOA stock solution and PFOS stock solution into pure water, stirring and mixing to obtain PFASs test solution; 3) adding a matrix substance to the test solution, and adjusting the pH to 5-10 and the temperature to 15-40°C; 4) purifying the test solution obtained in step 3) by a water purifier to be tested, sampling and detecting the removal rate of PFASs by the water purifier to be tested at different times. The present invention provides a method for detecting the removal effect of PFASs by a water purifier, which fills the gap in the evaluation method of the removal performance of PFASs by domestic water purifier standards, and establishes the evaluation method of the removal effect of PFASs by a water purifier for the first time; it can comprehensively evaluate the removal effect of a water purifier on PFASs, so as to ensure that the real removal capacity of the water purifier under different water quality conditions in actual use can be verified; it is a relatively simple operation method, and its results are more accurate.

Description

Technical Field

[0001] The invention relates to a method for detecting the PFASs removal effect of a water purifier, and belongs to the technical field of detecting the PFASs removal effect of a water purifier. Background Art

[0002] Per- and polyfluoroalkyl substances (PFASs) are a general term for a large class of synthetic chemicals, including thousands of specific substances. They are called "permanent chemicals" by the scientific community. They all contain carbon-fluorine (CF) bonds. The presence of CF bonds makes PFAS highly chemically inert and resistant to high temperatures, which can give products good waterproof, oil-proof and anti-fouling properties. Therefore, they are widely used in various consumer product fields, such as non-stick cookware, food packaging paper, luggage and outdoor products, coatings, etc. However, the presence of CF bonds also means that PFAS is difficult to decompose after entering the environment, and can migrate long distances through environmental media and spread all over the country. The subsequent pollution control is technically very difficult and costly. If PFAS are continuously released, they will accumulate in the environment and will further pollute our soil, water sources and food.

[0003] Among PFASs, perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) are chemicals that are often detected in the highest concentrations in environmental samples. The main exposure routes are oral, respiratory and dermal. The sources of oral exposure mainly include diet and drinking water. Studies have reported that PFOS / PFOA have multiple toxicities such as liver, immune, nervous, reproductive and developmental, and can increase the risk of tumors. They are harmful to human health and cause cardiometabolic diseases, endocrine disorders, renal damage, etc., and therefore have received increasing attention. PFOS / PFOA is widely present in the blood of the Chinese population, mostly PFOS, and exposure is on the rise, which may be related to increased environmental concentrations and accumulation in the body.

[0004] Drinking water in China mainly comes from surface water and groundwater. About 25% to 40% of the world's drinking water comes from groundwater, and 70% of my country's regions use groundwater as the main source of drinking water. The sources of PFOA and PFOS in groundwater are mainly leachate, domestic wastewater, and surface water infiltration. The results show that more than 20% of urban drinking water samples have PFAS concentrations exceeding the upper limit of the maximum pollutant standard. PFAS in some cities in the Yangtze River Basin has exceeded the health standards issued by European and American institutions. The cities with the highest PFAS concentrations are: Zigong (502.9ng / L), Lianyungang (332.6ng / L), Changshu (122.4ng / L), Chengdu (119.4ng / L), Wuxi (93.6ng / L) and Hangzhou (74.1ng / L).

[0005] With the development of my country's social economy and people's increasing expectations for living standards, drinking water safety and health are the focus of people's attention, and drinking safe and healthy drinking water has become a rigid need for people. At present, various domestic water purifier brands are uneven, and their purification principles and performance are not consistent. If there is no perfect detection method to evaluate the water purifier, there will be some safety hazards in product quality. Improving the testing method of water purifiers for PFASs is an urgent problem to be solved in the water purifier industry, and it is particularly important to study the removal effect and effect of water purifiers on PFASs. The GB5749-2022 "Drinking Water Standard" currently implemented in April 2023 has newly added perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) required limit values, but the industry lacks evaluation standards and requirements for the removal effect of PFOA / PFOS. For this reason, the present invention proposes a detection method for the removal effect of PFASs by a water purifier, and the detection type water purifier's ability to remove PFASs to fill the gap in domestic detection methods. Summary of the invention

[0006] The present invention provides a method for detecting the PFASs removal effect of a water purifier, which can detect the PFASs removal effect of a water purifier with high accuracy and is simple and easy to operate.

[0007] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows:

[0008] A method for detecting the removal effect of PFASs by a water purifier comprises the following steps:

[0009] 1) Dissolve PFOA and PFOS in methanol to obtain PFOA stock solution and PFOS stock solution respectively;

[0010] 2) Pipette PFOA stock solution and PFOS stock solution into pure water respectively, stir and mix well to obtain PFASs test solution;

[0011] 3) Add the matrix material to the test solution and adjust the pH to 5-10 and the temperature to 15-40°C;

[0012] 4) The test liquid obtained in step 3) is purified by the water purifier to be tested, and samples are taken to detect the removal rate of PFASs by the water purifier to be tested at different times.

[0013] PFOA is perfluorooctanoic acid C8HF 15 O2; PFOS is perfluorooctane sulfonic acid C8HF 17 O3S.

[0014] The above method can be used to accurately determine the removal effect of the water purifier on PFASs, which is simple, accurate and practical.

[0015] During the test, the removal rate is compared based on the product's declared lifespan, such as 8T of water, 10T of water, etc., and sampling is performed in sections when the water flow rate reaches 10-30% of the declared lifespan.

[0016] In step 1), the purity of PFOA is ≥95.5%, and the purity of PFOS is ≥98%; the amount of methanol used per mg of PFOA is 900-1100 ml, more preferably 1000 ml, and the amount of methanol used per mg of PFOS is 900-1000 ml, more preferably 1000 ml.

[0017] At present, the concentration of PFOA in natural water is higher than that of PFOS. In order to further improve the accuracy of the test, in step 2), the mass ratio of PFOA and PFOS in the PFASs test solution is (1.8-2.5):1, and more preferably 2:1. This is closer to the concentration in natural water.

[0018] In the above step 2), the volume ratio of PFOA stock solution to pure water is (0.03-0.05):100, more preferably 0.04:100, and the volume ratio of PFOS stock solution to pure water is (0.01-0.03):100, more preferably 0.02:100; stirring is performed at a speed of 200-400 r / min for more than 30 min; the conductivity of pure water is <10 us / cm.

[0019] In order to improve the accuracy of the test, in step 3), the matrix material is at least one of NaCl, CaCl2 or MgCl2. Preferably, in step 3), the matrix material is CaCl2 or MgCl2, more preferably CaCl2. The content of the matrix material in the test solution is 1 to 3 mmol / L.

[0020] The filter elements of existing water purifiers mainly include: activated carbon filter elements, ultrafiltration membrane filter elements, nanofiltration membrane filter elements and reverse osmosis membrane filter elements.

[0021] In order to improve the accuracy of the test, in step 3), the pH value for the activated carbon filter element is 8 to 9; the pH value for the ultrafiltration membrane filter element is 8 to 9; the pH value for the nanofiltration membrane filter element is 8 to 9; and the pH value for the reverse osmosis membrane filter element is 5 to 6.

[0022] The pH was adjusted with 6N hydrochloric acid or sodium hydroxide solution.

[0023] In order to improve the accuracy of the test, in step 3), the temperature for the activated carbon filter element is 30-36°C; the temperature for the ultrafiltration membrane filter element is 15-20°C; the temperature for the nanofiltration membrane filter element is 15-20°C; and the temperature for the reverse osmosis membrane filter element is 15-20°C.

[0024] In order to improve the accuracy of the test, in step 3), the flow rate during the test is 1 to 4 L / min. Preferably, in step 3), the flow rate for the activated carbon filter element is 1 to 1.5 L / min; the flow rate for the ultrafiltration membrane filter element is 3 to 4 L / min; the flow rate for the nanofiltration membrane filter element is 3 to 4 L / min; and the flow rate for the reverse osmosis membrane filter element is 1.8 to 2.2 L / min.

[0025] The technologies not mentioned in the present invention are all referred to the prior art.

[0026] The present invention provides a detection method for the PFASs removal effect of a water purifier, which can fill the gap in the domestic water purifier standard for the evaluation method of PFASs removal performance, and establishes the first evaluation method for the PFASs removal effect of a water purifier; it can more comprehensively evaluate the PFASs removal effect of a water purifier to ensure that the real removal capacity of the water purifier under different water quality conditions in actual use can be verified; the operation method is relatively simple and the result has higher accuracy; it promotes the continuous improvement of the water purification industry's purification capacity for PFASs. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a flow chart of detecting the removal effect of PFASs by the water purifier of the present invention; DETAILED DESCRIPTION

[0028] In order to better understand the present invention, the content of the present invention is further explained below in conjunction with the embodiments, but the content of the present invention is not limited to the following embodiments.

[0029] The purity of PFOA (perfluorooctanoic acid McLean P815842) is ≥95.5%; the purity of PFOS (perfluorooctanesulfonic acid Sigma 33607) is ≥98%;

[0030] Example 1

[0031] Configure the test fluid:

[0032] 1) Weigh 1 mg of PFOA and PFOS respectively and dissolve them in 1000 mL of methanol to prepare stock solutions.

[0033] 2) Pipette 40 mL of PFOA stock solution and 20 mL of PFOS stock solution into 100 L of pure water (conductivity <10 us / cm), and stir (300 r / min) for 35 min.

[0034] 3) Add the matrix material to the test solution and adjust the pH to 5-10 and the temperature to 15-40°C.

[0035] 4) The prepared test solution was sampled and tested for the total content of PFOA and PFOS.

[0036] Example 2

[0037] According to the method of Example 1, the test liquid is prepared in the test barrel to detect the water purifier of the activated carbon filter:

[0038] CaCl2 is used as the matrix material, the molar concentration of CaCl2 in the test liquid is 2mmol / L, the pH is adjusted to 9 using a 6N sodium hydroxide solution, the test liquid temperature is controlled at 35℃±1℃, and the test liquid flow rate is 1L / min. The test liquid is purified by the water purifier to be tested, and samples are taken to test the effluent concentration after the removal of PFASs by the water purifier to be tested with different water flow rates. Samples are taken twice and the relative precision deviation RPD is calculated. The calculation method is as follows:

[0039] formula:

[0040] Where: RPD is the relative deviation; x1 and x2 are the results of two measurements respectively.

[0041] And test the PFASs concentration of the test liquid in the barrel and calculate the accuracy relative error %D, the calculation method is as follows:

[0042] formula:

[0043] Where: %D is the relative deviation; X is the test value; μ is the true value.

[0044] The test results are as follows:

[0045]

[0046] Comparative Example 1

[0047] The pH of the test solution was adjusted to 6 using 6N hydrochloric acid. The rest were all referred to Example 2. The precision of the PFASs effluent concentration of 0-8000L decreased by 3.44%-4.45%, and the accuracy of the test solution decreased by 2.04%-3.01%.

[0048] Comparative Example 2

[0049] The temperature of the test liquid was adjusted to 15° C. The rest were referred to Example 2. The precision of the PFASs effluent concentration of 0-8000L decreased by 4.24%-5.21%, and the accuracy of the test liquid decreased by 2.87%-3.43%.

[0050] Comparative Example 3

[0051] The flow rate of the test liquid was adjusted to 4 L / min. The rest were referred to Example 2. The precision of the PFASs effluent concentration of 0-8000 L decreased by 4.16%-5.22%, and the accuracy of the test liquid decreased by 0.10%-0.17%.

[0052] Comparative Example 4

[0053] No CaCl2 was added as the matrix material. The rest were all referred to Example 2. The precision of 0-8000L PFASs effluent concentration decreased by 8.62%-10.22%, and the accuracy of the test solution decreased by 5.71%-6.21%.

[0054] Example 3

[0055] According to the method of Example 1, the test liquid is prepared in the test barrel to detect the water purifier of the ultrafiltration membrane filter element:

[0056] CaCl2 is used as the matrix material, the molar concentration of CaCl2 in the test liquid is 2mmol / L, the pH is adjusted to 9 using a 6N sodium hydroxide solution, the test liquid temperature is controlled at 15°C, and the test liquid flow rate is 4L / min. The test liquid is purified by the water purifier to be tested, and the concentration of the effluent after the removal of PFASs by the water purifier to be tested with different water flow rates is sampled and tested. The concentration of the effluent after the removal of PFASs by the water purifier to be tested with different water flow rates is sampled and tested. The sampling is repeated twice and the relative deviation RPD of the precision is calculated. The calculation method is the same as in Example 2. The PFASs concentration of the test liquid in the barrel is tested and the relative error %D of the accuracy is calculated. The calculation method is the same as in Example 2.

[0057] The test results are as follows:

[0058]

[0059] Comparative Example 5

[0060] The pH of the test solution was adjusted to 6 using 6N hydrochloric acid. The rest were all referred to Example 3. The precision of 0-8000L PFASs effluent concentration decreased by 4.34%-5.22%, and the accuracy of the test solution decreased by 2.62%-3.14%.

[0061] Comparative Example 6

[0062] The temperature of the test liquid was adjusted to 35° C. The rest were referred to Example 3. The precision of the PFASs effluent concentration of 0-8000L decreased by 3.26%-4.33%, and the accuracy of the test liquid decreased by 3.09%-4.01%.

[0063] Comparative Example 7

[0064] The flow rate of the test liquid was adjusted to 1 L / min. The rest were all referred to Example 3. The precision of the PFASs effluent concentration of 0-8000 L decreased by 2.13%-3.09%, and the accuracy of the test liquid decreased by 0.31%-0.42%.

[0065] Comparative Example 8

[0066] No CaCl2 was added as the matrix material. The rest were all referred to Example 3. The precision of 0-8000L PFASs effluent concentration decreased by 5.66%-6.34%, and the accuracy of the test solution decreased by 6.23%-6.71%.

[0067] Example 4

[0068] According to the method of Example 1, the test liquid is prepared in the test barrel to detect the water purifier of the nanomembrane filter element:

[0069] CaCl2 is used as the matrix material, the molar concentration of CaCl2 in the test liquid is 2mmol / L, the pH is adjusted to 9 using a 6N sodium hydroxide solution, the test liquid temperature is controlled at 15°C, and the test liquid flow rate is 4L / min. The test liquid is purified by the water purifier to be tested, and the concentration of the effluent after the removal of PFASs by the water purifier to be tested with different water flow rates is sampled and tested. The concentration of the effluent after the removal of PFASs by the water purifier to be tested with different water flow rates is sampled and tested. The sampling is repeated twice and the relative deviation RPD of the precision is calculated. The calculation method is the same as in Example 2. The PFASs concentration of the test liquid in the barrel is tested and the relative error %D of the accuracy is calculated. The calculation method is the same as in Example 2.

[0070] The test results are as follows:

[0071]

[0072] Comparative Example 9

[0073] The pH of the test solution was adjusted to 6 using 6N hydrochloric acid. The rest were all referred to Example 3. The precision of 0-8000L PFASs effluent concentration decreased by 4.27%-4.73%, and the accuracy of the test solution decreased by 2.54%-3.14%.

[0074] Comparative Example 10

[0075] The temperature of the test liquid was adjusted to 35° C. The rest were referred to Example 3. The precision of the PFASs effluent concentration of 0-8000L decreased by 3.97%-4.53%, and the accuracy of the test liquid decreased by 3.66%-4.34%.

[0076] Comparative Example 11

[0077] The flow rate of the test liquid was adjusted to 1 L / min. The rest were all referred to Example 3. The precision of the PFASs effluent concentration of 0-8000 L decreased by 5.97%-6.23%, and the accuracy of the test liquid decreased by 0.12%-0.45%.

[0078] Comparative Example 12

[0079] No CaCl2 was added as the matrix material. The rest were all referred to Example 4. The precision of 0-8000L PFASs effluent concentration decreased by 4.11%-5.24%, and the accuracy of the test solution decreased by 6.56%-7.17%.

[0080] Example 5

[0081] According to the method of Example 1, the test liquid is prepared in the test barrel to detect the water purifier of the reverse osmosis membrane filter element:

[0082] CaCl2 is used as the matrix material, the molar concentration of CaCl2 in the test liquid is 2mmol / L, the pH is adjusted to 6 using concentrated 6N hydrochloric acid, the test liquid temperature is controlled at 15°C, and the test liquid flow rate is 2L / min. The test liquid is purified by the water purifier to be tested, and the effluent concentration after the removal of PFASs by the water purifier to be tested with different water flow rates is sampled and tested. The effluent concentration after the removal of PFASs by the water purifier to be tested with different water flow rates is sampled and tested. The sampling is repeated twice and the relative deviation RPD of precision is calculated. The calculation method is the same as in Example 2. The PFASs concentration of the test liquid in the barrel is tested and the relative error %D of accuracy is calculated. The calculation method is the same as in Example 2.

[0083] The test results are as follows:

[0084]

[0085] Comparative Example 12

[0086] The pH of the test solution was adjusted to 9 using a 6N sodium hydroxide solution. The rest was referred to Example 4. The precision of the PFASs effluent concentration of 0-8000L decreased by 3.69%-4.53%, and the accuracy of the test solution decreased by 2.21%-2.77%.

[0087] Comparative Example 14

[0088] The temperature of the test liquid was adjusted to 35° C. The rest were referred to Example 4. The precision of the PFASs effluent concentration of 0-8000L decreased by 4.62%-5.22%, and the accuracy of the test liquid decreased by 3.23%-3.45%.

[0089] Comparative Example 15

[0090] The flow rate of the test liquid was adjusted to 4 L / min. The rest were all referred to Example 4. The precision of the PFASs effluent concentration of 0-8000 L decreased by 5.56%-5.71%, and the accuracy of the test liquid decreased by 0.24%-0.31%.

[0091] Comparative Example 16

[0092] No CaCl2 was added as the matrix material. The rest were all referred to Example 4. The precision of 0-8000L PFASs effluent concentration decreased by 3.31%-3.34%, and the accuracy of the test solution decreased by 4.92%-5.17%.

Claims

1. A method for detecting the removal effect of PFASs by a water purifier, characterized in that: The steps include: 1) Dissolve PFOA and PFOS in methanol to obtain PFOA stock solution and PFOS stock solution respectively; 2) Pipette PFOA stock solution and PFOS stock solution into pure water respectively, stir and mix well to obtain PFASs test solution; 3) Add the matrix material to the test solution and adjust the pH to 5-10 and the temperature to 15-40°C; 4) Purify the test solution obtained in step 3) through the water purifier to be tested, and take samples to test the removal rate of PFASs by the water purifier to be tested with different water flow rates; In step 1), the amount of methanol used per mg of PFOA is 900-1100 ml, and the amount of methanol used per mg of PFOS is 900-1000 ml; In step 2), the volume ratio of PFOA stock solution to pure water is (0.03-0.05):100, and the volume ratio of PFOS stock solution to pure water is (0.01-0.03):100; In step 3), the matrix material is CaCl2; the content of the matrix material in the test solution is 1-3 mmol / L; In step 3), the pH value for the activated carbon filter element is 8 to 9; the pH value for the ultrafiltration membrane filter element is 8 to 9; the pH value for the nanofiltration membrane filter element is 8 to 9; and the pH value for the reverse osmosis membrane filter element is 5 to 6; In step 3), the temperature of the activated carbon filter element is 30-36°C; the temperature of the ultrafiltration membrane filter element is 15-20°C; the temperature of the nanofiltration membrane filter element is 15-20°C; the temperature of the reverse osmosis membrane filter element is 15-20°C; In step 3), the flow rate during detection is 1~4 L / min; the flow rate for activated carbon filter element is 1~1.5 L / min; the flow rate for ultrafiltration membrane filter element is 3~4L / min; the flow rate for nanofiltration membrane filter element is 3~4L / min; the flow rate for reverse osmosis membrane filter element is 1.8~2.2L / min.

2. The method for detecting the removal effect of PFASs by a water purifier as claimed in claim 1, characterized in that: In step 1), the purity of PFOA is ≥95.5%, and the purity of PFOS is ≥98%.

3. The method for detecting the removal effect of PFASs by a water purifier as claimed in claim 1 or 2, characterized in that: In step 2), the mass ratio of PFOA and PFOS in the PFASs test solution is (1.8~2.5):

1.

4. The method for detecting the removal effect of PFASs by a water purifier as claimed in claim 1 or 2, characterized in that: In step 2), stirring is performed at a rotation speed of 200-400 r / min for more than 30 min; the conductivity of pure water is less than 10 us / cm.

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