Method for rapidly detecting hydrolysis degree of anionic polyacrylamide

Abstract

The invention discloses a method for rapidly detecting the hydrolysis degree of anionic polyacrylamide. The method comprises the following steps: preparing an anionic polyacrylamide solution of a sample to be detected; titrating the anionic polyacrylamide solution of the sample to be detected by using a hydrochloric acid standard solution; the titration end point is judged according to the pH change of the solution. According to the method, the titration end point is determined through pH change, the accuracy is higher, the operation is simpler, and the method is more practical.

Description

Technical Field

[0001] The invention belongs to the field of chemical detection, and in particular relates to a method for quickly detecting the hydrolysis degree of anionic polyacrylamide. Background Art

[0002] Polyacrylamide (PAM) is a linear water-soluble high molecular polymer widely used in industry, agriculture, life and other fields. Polyacrylamide can be used in water treatment, domestic sewage treatment and other industrial wastewater treatment as a coagulant and flocculant to help remove larger suspended solids and organic matter, improve the quality and efficiency of wastewater treatment, and effectively improve water quality.

[0003] One of the technical indicators of anionic polyacrylamide is the degree of hydrolysis. The degree of hydrolysis of anionic polyacrylamide has a significant effect on its flocculation effect. The degree of hydrolysis refers to the proportion of amide groups in polyacrylamide molecules converted to carboxyl groups. If the hydrolysis degree is too low, the adsorption and bridging ability of polyacrylamide is weak, and it cannot effectively condense suspended particles in the water, resulting in poor flocculation effect. Excessive hydrolysis will lead to enhanced anionicity of polyacrylamide, increase the repulsive force with negatively charged suspended particles, and reduce the flocculation effect. A moderate degree of hydrolysis (usually around 20%) can properly stretch the molecular chain of polyacrylamide, increase its adsorption surface area and bridging ability, and thus improve the flocculation effect.

[0004] Common methods for detecting the degree of hydrolysis include chemical titration, potentiometric titration, infrared spectroscopy, etc. At present, the method for detecting the degree of hydrolysis of anionic polyacrylamide in the national standard GB / T17514-2017 "Anionic and non-ionic polyacrylamide for water treatment agents" is too cumbersome, and the indicator color is used to judge the titration end point, the detection error is large, and the detection time is relatively long. These shortcomings need to be improved. Summary of the invention

[0005] The purpose of the present invention is to provide a method for quickly detecting the hydrolysis degree of anionic polyacrylamide in view of the above technical problems to be solved.

[0006] In order to achieve the above object of the invention, the present invention provides a method for quickly detecting the hydrolysis degree of anionic polyacrylamide, which comprises the following steps:

[0007] (1) preparing anionic polyacrylamide solution of a sample to be tested;

[0008] (2) titrating the anionic polyacrylamide solution of the sample to be tested with a hydrochloric acid standard solution;

[0009] (3) Determine the titration endpoint by the change in solution pH.

[0010] According to the method of the present invention, preferably, in the step (1), 0.03 g of polyacrylamide sample is dissolved in 100 mL of water to prepare the anionic polyacrylamide solution of the sample to be tested.

[0011] According to the method of the present invention, preferably, in the step (2), the beaker containing the anionic polyacrylamide solution of the sample to be tested is placed in a constant temperature water bath on a magnetic stirrer, the temperature is controlled at 30°C±0.5°C, the electrode of the acidity meter is inserted into the anionic polyacrylamide solution of the sample to be tested, the distance from the beaker wall is 5mm-10mm, and the distance between the electrode and the magnetic head is 5mm, then the magnetic stirrer is turned on, the liquid surface vortex depth is adjusted to 20mm, then the water temperature of the constant temperature water bath is raised to 30°C±0.5°C, the temperature is kept constant for 10min, and then the polyacrylamide solution of the sample to be tested is titrated with a hydrochloric acid standard solution.

[0012] According to the method of the present invention, preferably, in the step (3), the change of pH on the acidometer is observed, and when the pH drops to 4.16, it is the titration endpoint.

[0013] Compared with the prior art, the present method determines the titration end point by measuring the pH change with an acidity meter, which is more accurate than manually determining the titration end point by the color change of the indicator, and is simpler and more practical to operate. DETAILED DESCRIPTION

[0014] The present invention will be further described below in conjunction with specific examples. It should be understood that the following examples are only used to illustrate the present invention, rather than to limit the scope of the present invention.

[0015] The present invention provides a method for rapidly detecting the hydrolysis degree of anionic polyacrylamide, wherein the method titrates the anionic polyacrylamide with a hydrochloric acid standard solution and determines the titration end point by the change in the pH value of the solution. The method can solve the problem that different people have different judgments on the color of the indicator, and can more accurately detect the hydrolysis degree of anionic polyacrylamide.

[0016] The specific detection steps of the method for quickly detecting the hydrolysis degree of anionic polyacrylamide provided by the present invention are as follows:

[0017] S1: Place a 200mL beaker containing 100mL of water on a magnetic stirrer, insert a 5cm magnetic head, turn on the stirrer, and adjust the speed to 400r / min.

[0018] S2: Accurately weigh about 0.03 g of polyacrylamide sample and slowly add it into a 200 mL beaker to completely dissolve it to obtain a polyacrylamide solution of the sample to be tested.

[0019] S3: Place the 200mL beaker with dissolved polyacrylamide in a constant temperature water bath on a magnetic stirrer, and control the temperature at 30±0.5℃. Insert the electrode of the acidometer into the 200mL beaker with dissolved polyacrylamide, with a distance of 5mm to 10mm from the beaker wall, and the distance between the electrode and the magnetic head is about 5mm.

[0020] S4: Turn on the magnetic stirrer, adjust the vortex depth of the liquid surface to about 20 mm, then turn on the heating device of the constant temperature water bath, raise the water temperature of the constant temperature water bath to 30℃±0.5℃, and keep the temperature constant for 10 minutes.

[0021] S5: Titrate the polyacrylamide solution of the sample to be tested with a 0.1 mol / L hydrochloric acid standard solution, and observe the change in pH on the acidometer. When the pH drops to 4.16, it is the titration endpoint. Record the volume V of the hydrochloric acid standard solution consumed in the titration.

[0022] S6: Degree of hydrolysis w n The hydrolysis degree is calculated by the following formula (3):

[0023]

[0024] V——The volume of the hydrochloric acid standard titration solution consumed in the titration, in milliliters (mL);

[0025] c——The accurate value of the actual concentration of the hydrochloric acid standard titration solution, in moles per liter (mol / L);

[0026] M1——the numerical value of the molar mass of acrylamide in grams per mole (g / mol) (M3=71.07);

[0027] M2——the numerical value of the molar mass of sodium acrylate in grams per mole (g / mol) (M=94.04);

[0028] m——the value of the sample mass, in grams (g);

[0029] w1——mass fraction of solid content of the sample, expressed in %.

[0030] This method was used to detect the hydrolysis degree of the same anionic polyacrylamide sample. After 10 repeated measurements, the test results are shown in the following table.

[0031] 1 2 3 4 5 6 7 8 9 10 Degree of hydrolysis 22.45 22.51 22.47 22.52 22.48 22.46 22.51 22.50 22.49 22.48

[0032] It can be seen from the above 10 repeated measurement data that the error of the results obtained by titration with an acidometer is within the difference allowed by the national standard, and the repeatability of the results is higher than that of manual titration.

Claims

1. A method for rapidly detecting the degree of hydrolysis of anionic polyacrylamide, characterized in that The following steps are involved: (1) preparing anionic polyacrylamide solution of a sample to be tested; (2) titrating the anionic polyacrylamide solution of the sample to be tested with a hydrochloric acid standard solution; (3) Determine the titration endpoint by the change in solution pH.

2. The method according to claim 1, characterized in that In the step (1), 0.03 g of polyacrylamide sample is dissolved in 100 mL of water to prepare the anionic polyacrylamide solution of the sample to be tested.

3. The method according to claim 1, characterized in that In the step (2), the beaker containing the anionic polyacrylamide solution of the sample to be tested is placed in a constant temperature water bath on a magnetic stirrer, the temperature is controlled at 30°C±0.5°C, the electrode of the acidity meter is inserted into the anionic polyacrylamide solution of the sample to be tested, the distance from the beaker wall is 5mm-10mm, and the distance between the electrode and the magnetic head is 5mm, then the magnetic stirrer is turned on, the liquid surface vortex depth is adjusted to 20mm, and then the water temperature of the constant temperature water bath is raised to 30°C±0.5°C, the temperature is kept constant for 10 minutes, and then the polyacrylamide solution of the sample to be tested is titrated with a hydrochloric acid standard solution.

4. The method according to claim 1, characterized in that In the step (3), the change of pH on the acidometer is observed, and when the pH drops to 4.16, it is the titration endpoint.

5. The method according to claim 1, characterized in that The concentration of the hydrochloric acid standard solution is 0.1 mol / L.

Images