阅读说明：本技术 一种海砂氯离子含量的检测方法 (Method for detecting content of chloride ions in sea sand ) 是由 刘俊瑞 林超 朱金鹏 李洁 王慧鑫 朱洪泉 高秀鑫 张宏宇 毛成琦 陈明星 杨尉 于 2020-12-21 设计创作，主要内容包括：本发明公开了一种海砂氯离子含量的检测方法。该检测方法首先将自然潮湿的海砂烘干至恒重,过筛后加入去离子水搅拌并加热处理,然后静置并过滤得到海砂的氯离子溶出液；在海砂的氯离子溶出液中加入酚酞试剂,使用HNO-3溶液或者NaOH溶液调节溶出液为中性；然后向溶出液中加入H-2O-2溶液去除硫离子的影响；继续加入铬酸钾溶液作为指示剂,采用硝酸银滴定法测定溶出液中的氯离子含量。本发明的检测方法能够使海砂内部的氯离子得到充分的释放,并排除了海砂中pH值、硫离子等因素对检测结果的影响,提高了检测的精度,使检测结果更加准确和可靠,为海砂在工程领域的使用提供可靠的依据。(The invention discloses a method for detecting the content of chloride ions in sea sand. The detection method comprises the steps of firstly drying naturally moist sea sand to constant weight, sieving, adding deionized water, stirring, heating, standing and filtering to obtain a chloride ion dissolving liquid of the sea sand; adding phenolphthalein reagent into chloride ion dissolution liquid of sea sand, and using HNO 3 Adjusting the solution to be neutral by the solution or NaOH solution; then adding H into the dissolution liquid 2 O 2 The solution removes the influence of sulfur ions; and continuously adding a potassium chromate solution as an indicator, and measuring the content of chloride ions in the dissolution liquid by a silver nitrate titration method. The detection method provided by the invention can fully release chloride ions in the sea sand, eliminates the influence of factors such as pH value and sulfur ions in the sea sand on the detection result, improves the detection precision, enables the detection result to be more accurate and reliable, and provides a reliable basis for the use of the sea sand in the engineering field.)

1. A detection method for sea sand chloride ion content is characterized by comprising the following steps: firstly, drying naturally moist sea sand to constant weight, sieving, adding deionized water, stirring and heating, then standing and filtering to obtain a chloride ion dissolving liquid of the sea sand; adding phenolphthalein reagent into chloride ion dissolution liquid of sea sand, and using HNO₃Adjusting the solution to be neutral by the solution or NaOH solution; then adding H into the dissolution liquid₂O₂The solution removes the influence of sulfur ions; and continuously adding a potassium chromate solution as an indicator, and measuring the content of chloride ions in the dissolution liquid by a silver nitrate titration method.

2. The method for detecting the content of chloride ions in sea sand is characterized by comprising the following specific operation steps:

1) weighing sea sand in a natural wet state, placing the sea sand in a drying box, drying the sea sand to constant weight, cooling the sea sand to room temperature, and sieving the sea sand;

2) weighing the sample M treated in the step 1)₁g, pour the sample into a beaker, add V₁Stirring the deionized water in milliliters, covering the beaker, and then placing the beaker in a constant-temperature water bath box for heating treatment;

3) after the heating treatment is finished, standing and cooling to room temperature, filtering to obtain chloride ion dissolving liquid of sea sand, and sucking V by a pipette₂Injecting milliliters into a conical flask for later use;

4) dripping phenolphthalein reagent into chloride ion dissolution liquid of sea sand in the conical flask, and dripping HNO dropwise if the dissolution liquid turns red₃Continuously shaking the conical flask in the dripping process until the solution turns colorless; after the phenolphthalein reagent is droppedIf the dissolution liquid does not change color, dropwise adding NaOH solution, and continuously shaking the conical flask in the dropping process until the dissolution liquid turns red;

5) adding H into the dissolution liquid adjusted to be neutral in the step 4)₂O₂The solution is used for removing sulfur ions in the dissolution liquid;

6) adding potassium chromate solution as indicator into the solution, and then using AgNO₃Titrating the standard solution, continuously shaking the conical flask to show brick red as a terminal point in the titration process, and recording the consumed AgNO₃Standard solution dosage.

3. The method for detecting the content of chloride ions in sea sand according to claim 2, wherein the calculation formula adopted by the detection method is as follows:

in the formula, Q is the percentage of the chloride ion content in the sea sand; n is AgNO₃The concentration of the standard solution is in mol/L; a is AgNO consumed during titration₃Volume of standard solution in ml; m₁The mass of the sea sand sample is g; v₁Is M₁g total volume of chloride ion-dissolved solution of sea sand sample, V₂AgNO for separation₃The volume of the dissolution liquid titrated by the standard solution is ml; 0.0355 is the millimolar mass g/mmol of chloride ions.

4. The method for detecting the content of chloride ions in sea sand according to claim 2, wherein after the detection is finished, the container is cleaned by strong ammonia water, and the influence of attached precipitated AgCl on the next test result is eliminated.

5. The method for detecting the content of chloride ions in sea sand according to claim 2, wherein the drying temperature in the step 1) is 105 +/-5 ℃.

6. The method for detecting the content of chloride ions in sea sand according to claim 2, wherein the heating temperature in the step 2) is 80 +/-5 ℃, the heating time is 1h, and the sample is stirred by a glass rod every 10-15min in the heating process.

7. The method for detecting the content of chloride ions in sea sand according to claim 2, wherein M in the step 2)₁And V₁The ratio of (A) to (B) is 1: 1-2.

8. The method for detecting the chloride ion content in the sea sand according to claim 2, wherein the standing time in the step 3) is not less than 8h and V₂And V₁The ratio of (A) to (B) is 1: 5-10.

9. The method for detecting the chloride ion content in the sea sand according to claim 2, wherein the concentration of the potassium chromate solution in the step 6) is 5 wt%, and the volume ratio of the potassium chromate solution to the solution to be dissolved is 1:50-100-1: 50.

Technical Field

The invention belongs to the technical field of chloride ion content detection, and particularly relates to a method for detecting chloride ion content of sea sand.

Background

At present, with the accelerated urbanization process of China, the usage amount of river sand is increased sharply, the storage amount of the river sand is in a trend of gradually reducing and even depleting, the sea sand is an ideal river sand supplement resource, compared with the river sand, the sea sand has the characteristics of good granularity, low silt content, low price and the like, and coastal areas of China have rich sea sand resources. Sea sand is a good substitute for river sand, and has the advantages of good grain shape, low cost, low mud content and abundant reserves. The full utilization of the sea sand can effectively relieve the tension situation of the building sand in China, and has great significance for the development of the building industry. The 'building sand' standard provides a definite detection method and technical requirements for various indexes of sand.

However, in the process of using the sea sand, the chloride ion content in the sea sand is higher, so that the corrosion damage can be caused to the steel bars in the concrete, and the durability of the concrete structure is reduced. In the actual engineering investigation, the sea sand with qualified chloride ion content in the construction process is detected according to the standard of 'sand for construction', and irreparable damage can be generated to the construction engineering after a certain construction age along with the development of time.

Through analysis, the method is found to be caused by the defects of the sea sand chloride ion detection method in the current specification, and mainly comprises the following two points:

(1) the existing sea sand chloride ion detection method in China is not perfect and can not completely detect the content of chloride ions in sea sand. Under normal conditions, the chloride ions in the sea sand are tightly wrapped by the film on the surface and are in a stable state, and the chloride ions cannot be released at normal temperature, so that the detected chloride ions are low in content, and the chloride ions in the sea sand in the actual use process are gradually released along with the service life, so that the steel bars are corroded.

(2) The method for detecting the content of chloride ions in the building sand specification does not change according to the characteristics of sea sand, and is poor in applicability. Since sea sand is accumulated in the sea throughout the year, anions such as S are adhered to the surface of sea sand^2-、SO₄ ^2-The content of the sea sand is higher than that of the river sand, and the pH value of the sea sand solution is different from that of the river sand, so that the detection results are different due to the factors.

Therefore, the method for detecting the content of the chloride ions has important significance for the application of the sea sand in the building engineering.

Disclosure of Invention

The invention mainly aims to overcome the defects of the existing method for detecting the content of chloride ions and provide a novel method for detecting the content of chloride ions in sea sand. The method can fully release chloride ions in the sea sand, eliminates the influence of factors such as pH value and sulfur ions in the sea sand on the detection result, improves the detection precision, enables the detection result to be more accurate and reliable, and provides a reliable basis for the use of the sea sand in the engineering field.

The method for detecting the content of chloride ions in the sea sand comprises the following steps: firstly, drying naturally moist sea sand to constant weight, sieving, adding deionized water, stirring and heating, then standing and filtering to obtain a chloride ion dissolving liquid of the sea sand; adding phenolphthalein reagent into chloride ion dissolution liquid of sea sand, and using HNO₃Adjusting the solution to be neutral by the solution or NaOH solution; however, the device is not suitable for use in a kitchenAdding H into the solution₂O₂The solution removes the influence of sulfur ions; and continuously adding a potassium chromate solution as an indicator, and measuring the content of chloride ions in the dissolution liquid by a silver nitrate titration method.

The method for detecting the content of chloride ions in sea sand comprises the following specific operation steps:

1) weighing sea sand in a natural wet state, placing the sea sand in a drying box, drying the sea sand to constant weight, cooling the sea sand to room temperature, and sieving the sea sand;

2) weighing the sample M treated in the step 1)₁g, pour the sample into a beaker, add V₁Stirring the deionized water in milliliters, covering the beaker, and then placing the beaker in a constant-temperature water bath box for heating treatment;

3) after the heating treatment is finished, standing and cooling to room temperature, filtering to obtain chloride ion dissolving liquid of sea sand, and sucking V by a pipette₂Injecting milliliters into a conical flask for later use;

4) dripping phenolphthalein reagent into chloride ion dissolution liquid of sea sand in the conical flask, and dripping HNO dropwise if the dissolution liquid turns red₃Continuously shaking the conical flask in the dripping process until the solution turns colorless; dripping NaOH solution dropwise if the dissolution liquid does not change color after the phenolphthalein reagent is dripped, and continuously shaking the conical flask in the dripping process until the dissolution liquid turns red;

5) adding H into the dissolution liquid adjusted to be neutral in the step 4)₂O₂The solution is used for removing sulfur ions in the dissolution liquid;

6) adding potassium chromate solution as indicator into the solution, and then using AgNO₃Titrating the standard solution, continuously shaking the conical flask to show brick red as a terminal point in the titration process, and recording the consumed AgNO₃Standard solution dosage.

The detection method of the content of chloride ions in the sea sand adopts a calculation formula as follows:

wherein Q is the chloride ion content in sea sandDividing; n is AgNO₃The concentration of the standard solution is in mol/L; a is AgNO consumed during titration₃Volume of standard solution in ml; m₁The mass of the sea sand sample is g; v₁Is M₁g total volume of chloride ion-dissolved solution of sea sand sample, V₂AgNO for separation₃The volume of the dissolution liquid titrated by the standard solution is ml; 0.0355 is the millimolar mass g/mmol of chloride ions.

According to the method for detecting the content of the chloride ions in the sea sand, after detection is finished, the container is cleaned by using strong ammonia water, and the influence of attached precipitate AgCl on the next test result is eliminated.

The drying temperature in the step 1) is 105 +/-5 ℃.

In the step 2), the heating temperature is 80 +/-5 ℃, the heating time is 1h, and the samples are stirred by glass rods every 10-15min in the heating process.

M in the step 2)₁And V₁The ratio of (A) to (B) is 1: 1-2.

The standing time in the step 3) is not less than 8h, V₂And V₁The ratio of (A) to (B) is 1: 5-10.

The concentration of the potassium chromate solution in the step 6) is 5 wt%, and the volume ratio of the potassium chromate solution to the to-be-detected dissolving solution is 1:50-100-1: 50.

Compared with the prior art, the invention has the following beneficial effects:

1. through the continuous high temperature heating of the sample of waiting to examine and the processing of stirring, destroyed the steady state of sea sand surface material, made the inside chloride ion of sea sand obtain abundant release for measurement accuracy is higher, and the testing result is close to reality more.

2. Aiming at the characteristics of sea sand, HNO is added₃The pH value of the solution is changed by the solution or NaOH solution, so that the pH value of the solution is kept neutral, and the influence of the pH values of sea sand in different regions on the detection result is avoided.

3. Adding a certain amount of H into the sample solution₂O₂The solution eliminates the influence of sulfur ions in the sea sand on the detection result.

4. In the detection process, the detailed limited proportion is made on the use amount of the solution quality, the addition amount of the indicator and the like, and meanwhile, deionized water is directly adopted to replace distilled water to prepare the solution, so that the test operation steps are simplified, and the detection accuracy and reliability are improved.

Detailed Description

Example 1

Drying the natural wet Guangdong Zhuhai sand in a drying oven at 100 ℃ to constant weight, cooling to room temperature, and sieving; weighing 500g of processed sea sand sample to be detected, pouring the sea sand sample into 600ml of deionized water, putting the sea sand sample into a constant-temperature water bath box with the temperature of 80 ℃ for heating for 1h, stirring once every 10min in the heating process, standing the sea sand sample for 10h, cooling the sea sand sample to room temperature, filtering the sea sand sample to obtain a chloride ion dissolving liquid of the sea sand, extracting 50ml of the dissolving liquid by using a pipette, pouring the dissolving liquid into a conical flask, dropwise adding a phenolphthalein reagent into the conical flask, enabling the dissolving liquid to turn red, and dropwise adding 0.1mol/LHNO₃Adding the solution while shaking the conical flask until the solution turns colorless; 3ml of 30% strength by weight H are added₂O₂Adding 1mL of 5 wt% potassium chromate indicator, and adding 0.01mol/L AgNO₃Titrating the standard solution, continuously shaking the conical flask to show brick red as a terminal point in the titration process, and recording the consumed AgNO₃The amount of standard solution used, 41.1ml of first consumption solution, using the formula:the chloride ion content was calculated as 0.01 × 41.1 × 0.0355 × 600 ÷ 500 ÷ 50 × 100 ═ 0.035%; the amount of the second consumption solution was 38.6ml, and the chloride ion content was calculated to be 0.01 × 38.6 × 0.0355 × 600 ÷ 500 ÷ 50 × 100 ═ 0.033%, and the average of the results of the two tests was taken to obtain a chloride ion content of 0.034% in the sea sand.

Comparative example 1:

the content of chloride ions in the sea sand is calculated by adopting a test method in GB/T14684-2011 construction sand. 1100g of sea sand sample with the same source as that in the example 1 is taken according to a quartering method, dried in a drying oven to constant weight and then cooled for later use; weighing 500g of dry sand, pouring into a ground bottle, injecting 500mL of distilled water into the ground bottle, and covering with a plugShaking once, standing for 2h, then shaking once every 5min, and shaking 3 times to dissolve the chloride; filtering clarified solution at upper part of ground bottle, pouring 50ml of solution into conical flask, adding 1ml of 5% potassium dichromate indicator, and adding 0.01mol/L AgNO₃Titrating the standard solution, continuously shaking the conical flask in the titration process until the conical flask presents brick red as an end point, and measuring AgNO₃The consumption of the standard solution was 31.7ml, and the chloride ion content was calculated to be 0.01 × 31.7 × 0.0355 × 10 ÷ 500 × 100 ═ 0.023% by the formula, and AgNO was added for the second time₃The consumption of the standard solution is 32.3ml, the content of the chloride ion is calculated to be 0.023 percent, and the arithmetic mean value of the two test results is taken to obtain the content of the chloride ion to be 0.023 percent.

Comparative example 2:

drying the natural wet Guangdong Zhuhai sand in a drying oven at 100 ℃ to constant weight, cooling to room temperature, and sieving; weighing 500g of processed sea sand sample to be detected, pouring the sea sand sample into 600ml of deionized water, putting the sea sand sample into a constant-temperature water bath at the temperature of 100 ℃ for heating for 1h, stirring the sea sand sample once every 10min in the heating process, standing the sea sand sample for 10h, cooling the sea sand sample to room temperature, filtering the sea sand sample to obtain a chloride ion dissolving liquid of the sea sand, extracting 50ml of the dissolving liquid by using a pipette, pouring the solution into a conical flask, dropwise adding a phenolphthalein reagent into the conical flask, enabling the dissolving liquid to turn red, and dropwise adding 0.1mol/LHNO₃Adding the solution while shaking the conical flask until the solution turns colorless; 3ml of 30% strength by weight H are added₂O₂Adding 1mL of 5 wt% potassium chromate indicator, and adding 0.01mol/L AgNO₃Titrating the standard solution, continuously shaking the conical flask to show brick red as a terminal point in the titration process, and recording the consumed AgNO₃Standard solution dosage. The first consumption solution was used in an amount of 39.3ml using the formula:the chloride ion content was 0.01 × 39.3 × 0.0355 × 600 ÷ 500 ÷ 50 × 100 ═ 0.033%; the amount of the second consumption solution was 40.5ml, the chloride ion content was calculated to be 0.01 × 40.5 × 0.0355 × 600 ÷ 500 ÷ 50 × 100 ═ 0.035%, the average of the two test results was calculated to obtain sea sandThe content of chloride ion is 0.034%. Compared with the result of the example 1, the test result has small change, namely the temperature of the constant temperature water bath is higher than 80 ℃ and has little influence on the test result.

Comparative example 3:

drying the natural wet Guangdong Zhuhai sand in a drying oven at 100 ℃ to constant weight, cooling to room temperature, and sieving; weighing 500g of processed sea sand sample to be detected, pouring the sea sand sample into 600ml of deionized water, putting the sea sand sample into a constant temperature water bath box with the temperature of 80 ℃ for heating for 2h, stirring once every 10min in the heating process, standing for 10h, cooling to room temperature, filtering to obtain a chloride ion dissolving liquid of the sea sand, extracting 50ml of the dissolving liquid by using a pipette, pouring the solution into a conical flask, dropwise adding a phenolphthalein reagent into the conical flask, enabling the dissolving liquid to turn red, and dropwise adding 0.1mol/L HNO₃The flask was shaken while adding the solution until the solution became colorless, and 3ml of 30 wt% H was added₂O₂Adding 1mL of 5 wt% potassium chromate indicator, and adding 0.01mol/L AgNO₃Titrating the standard solution, continuously shaking the conical flask to show brick red as a terminal point in the titration process, and recording the consumed AgNO₃The amount of standard solution used, the amount of first consumption solution used was 40.2ml, using the formula:the chloride ion content was found to be 0.01 × 40.2 × 0.0355 × 600 ÷ 500 ÷ 50 × 100 ═ 0.034%, the amount of the solution consumed for the second time was found to be 41.3ml, the chloride ion content was found to be 0.01 × 41.3 × 0.0355 × 600 ÷ 500 ÷ 50 × 100 ═ 0.035%, the average of the results of the two tests was found to be 0.035%, and the content of chloride ions in sea sand was found to be 0.035%, which showed little change from the result of example 1, i.e., the sea sand was sufficiently released from the interior of a constant temperature water bath at 80 ℃ for 1 hour, and the test results were not greatly affected by a time extension of 2 hours.

Therefore, the sea sand solution is continuously heated and stirred to break the film stabilizing layer on the surface of the sea sand, the chloride ions in the sea sand are released, the pH value of the solution is kept, the influence of other components in the sea sand on the detection result is eliminated, the detection precision of the chloride ion content is improved, and the reliability of the detection result is ensured.

The above description is only a preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can make equivalent changes and modifications within the technical scope of the present invention disclosed by the present invention.