A method for analyzing the inorganic element content of waste heat blackening agent

Abstract

The invention discloses an analysis method for the inorganic element content of a waste heat blackening agent, comprising the following steps: (1) centrifuging a blackening agent working liquid to be tested to separate solid impurities therein; (2) drying the liquid separated by centrifugation to obtain its effective solid content; (3) diluting the liquid separated in step (1); pouring the obtained diluted liquid into the upper layer of an ultrafiltration centrifuge tube to separate the resin in the sample; (4) performing element analysis on the lower layer liquid separated in step (3) using an ICP inductively coupled plasma emission spectrometer; and (5) calculating the concentration of each element in the sample liquid based on the dilution ratio of step (3) and the test result of step (4).

Description

Technical Field

[0001] The invention relates to an analysis method for the inorganic element content of a waste heat blackening agent. Background Art

[0002] Blackening process refers to the process of forming a black protective film on the surface of metal, mainly steel workpieces, through physical or chemical methods to improve the rust resistance of the workpiece and make the appearance more uniform and beautiful. Residual heat blackening usually uses the residual heat of heat treatment tempering or directly heats the workpiece, and then puts the high-temperature workpiece into the blackening agent working liquid. The working liquid is partially heated and vaporized, forming a black film layer with a certain adhesion and bonding force on the surface of the workpiece.

[0003] Waste heat blackening is the most widely used blackening technology under the current environmental protection requirements. As waste heat blackening technology becomes more mature, the scope and field of application are becoming wider and wider. At present, the analysis and detection technology for the application of this product is not perfect, which makes it difficult to judge the crux of many application technical problems, affecting the long-term stable use of the product. For example, the failure of waste heat blackening agent during use often occurs at the same time as the increase in conductivity, but it is difficult to judge whether the increase in conductivity is caused by normal use accumulation or exogenous pollution. And the tolerance of the blackening agent working fluid to different inorganic salts is different. For example, for the same inorganic salt pollution with a conductivity of 2000μS / cm, sodium and potassium salts have almost no effect on the blackening quality, but calcium and magnesium salts will cause the blackening agent film to appear obvious roughness or mottled, resulting in a decrease in blackening quality. Pollution with higher conductivity may even cause serious problems such as incomplete local film layers. Therefore, it is necessary to regularly and accurately analyze the content of various elements in the blackening agent working fluid to determine its actual contamination situation. At present, the blackening agent working fluid sample is directly input into the ICP inductively coupled plasma emission spectrometer for analysis, but the resin in the blackening agent working fluid can easily clog the instrument's atomizer pipeline and probe, which will cause the equipment consumables to fail quickly, thereby increasing the detection cost, and on the other hand will result in a low analysis success rate. Summary of the invention

[0004] Purpose of the invention: The purpose of the present invention is to provide a method for analyzing the inorganic element content of a waste heat blackening agent. The method can effectively improve the detection accuracy of the ICP device for the inorganic element content in the waste heat blackening agent, and solve the problem of low detection success rate in the existing analysis and detection process. The method of the present invention separates the working fluid into two parts, a polymer resin emulsion and an inorganic salt solution, and then directly analyzes the inorganic salt solution, thereby improving the analysis accuracy and reducing the analysis cost.

[0005] Technical solution: The method for analyzing the inorganic element content of the waste heat blackening agent of the present invention comprises the following steps:

[0006] (1) centrifuging the blackening agent working solution to be tested to separate solid impurities therein;

[0007] (2) taking 1.50±0.3 mL of the liquid separated in step (1) and drying it to obtain its effective solid content;

[0008] (3) Based on the solid content of step (2), the liquid separated in step (1) is diluted, and the solid content of the diluted liquid after dilution is 1.0-2.5%; the obtained diluted liquid is poured into the upper layer of an ultrafiltration centrifuge tube to separate the resin in the sample, that is, the resin and the inorganic salt are separated; the molecular weight of the polymer resin in the waste heat blackening working liquid is greater than 30kD and cannot pass through the ultrafiltration membrane, while the various inorganic salt additives and pollutants in the working liquid are less than 3kD and can pass through the ultrafiltration membrane. After separation by the ultrafiltration centrifuge tube, the lower layer liquid is an inorganic salt solution, and the upper layer is a mixture of a polymer resin emulsion and an inorganic salt solution, thereby achieving almost no interference and no risk of failure when the solution is subjected to ICP analysis;

[0009] (4) performing elemental analysis on the lower layer liquid separated in step (3) using an ICP inductively coupled plasma emission spectrometer;

[0010] (5) Calculate the concentration of each element in the sample solution based on the dilution ratio of step (3) and the test results of step (4).

[0011] Wherein, in step (1), the maximum relative centrifugal force is 4000-5000g, and the centrifugation time is 15-20min.

[0012] Wherein, in step (2), a halogen moisture meter is used for drying, the drying temperature is 110-120° C., and the time is 20-30 min.

[0013] Wherein, in step (3), the solid content of the diluted solution after dilution is 1.0 to 2.5%.

[0014] Wherein, in step (3), the cut-off specification of the centrifugal ultrafiltration tube is 3kD, 10kD or 30kD.

[0015] Wherein, in step (3), the size of the ultrafiltration centrifuge tube is 15 mL or 50 mL.

[0016] Wherein, in step (3), the speed of the high-speed centrifuge is 6200-8000 rpm, the maximum relative centrifugal force is 5000-6000 g, and the centrifugation time is 30-40 min to separate the liquid.

[0017] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: The present invention is a separation process before the detection of the blackening agent working fluid, which can be widely applicable to the separation and treatment of various types of waste heat blackening agents. By using the blackening agent working fluid sample separated by the present invention, the polymer resin in the blackening agent can be separated, which can effectively reduce the solid content and precipitation risk of the liquid phase, thereby effectively inhibiting the precipitation of the polymer resin during the detection process and hindering the analysis process, thereby solving the problem that the inorganic element content of the existing waste heat blackening agent working fluid is difficult to analyze or the analysis is inaccurate, and also saves the analysis characterization cost. DETAILED DESCRIPTION

[0018] Example 1

[0019] The method for analyzing the inorganic element content of the waste heat blackening agent of the present invention comprises the following steps:

[0020] A blackening liquid with a usage concentration of 10wt% has been used for 3 months.

[0021] The ion concentration corresponding to the above blackening liquid (calculated at 10wt% concentration) and the measured ion concentration of the newly prepared blackening agent working solution (10wt% blackening liquid + tap water) are shown in the following table:

[0022] element B Ca Fe K Na P S Si Design content / ppm 0.0 0.0 0.0 63.0 17.5 0.0 25.0 13.2 New solution content / ppm 0.0 12.1 0.0 64.3 20.2 0.1 26.1 13.4

[0023] (1) Take 1 kg of residual heat blackening agent working liquid (for a blackening liquid with a use concentration of 10 wt %, which has been used for 3 months), shake it thoroughly, take 30.0 mL and put it into a 50 mL centrifuge tube, centrifuge it in a high-speed centrifuge, set the maximum relative centrifugal force to 4000 g, and centrifuge it for 15 min; after centrifugation, pour out 29.8 mL of the upper liquid; use it for the subsequent steps;

[0024] (2) taking 1.5 mL of the upper layer liquid after centrifugation in step (1), setting the temperature at 110° C. in a halogen moisture meter for 20 min to dry, and obtaining the effective solid content. The effective solid content of the blackening agent working solution was 2.62%;

[0025] (3) Take 10.0 mL of the upper layer liquid after centrifugation in step (1), add 10.0 mL of pure water, and obtain 20 mL of dilution liquid. Based on step (2), it can be known that the solid content of the dilution liquid is 1.31%;

[0026] (4) Pour 20 mL of the diluted working solution in step (3) into the upper layer of a 50 mL ultrafiltration centrifuge tube with a cutoff specification of 30 kD; set the high-speed centrifuge speed to 7400 rpm, the maximum relative centrifugal force to 6000 g, and the centrifugation time to 30 min;

[0027] (5) Take the lower layer liquid after high-speed ultrafiltration in the ultrafiltration centrifuge tube, and separate 8.3 mL of clear liquid. Perform ICP inductively coupled plasma emission spectroscopy analysis. The results are shown in the following table (the data with results less than 1 ppm have been omitted).

[0028] element B Ca Fe K Na P S Si Content / ppm 37.7 26.4 1.9 127.6 37.2 3.3 52.6 18.5

[0029] Based on step (3), the dilution ratio is 2 times, so the actual ion concentrations in the blackening agent working solution sample are shown in the following table:

[0030]

[0031] By comparing with the formula, it can be confirmed that the K, Na, and S elements contained in the blackening agent working liquid sample come from the blackening agent, while the B, Ca, and Si elements are more obvious exogenous pollution, among which the concentration of Ca ions increases faster, which can easily lead to a decrease in the quality of the blackening appearance.

[0032] Example 2

[0033] The method for analyzing the inorganic element content of the waste heat blackening agent of the present invention comprises the following steps:

[0034] A blackening liquid with a usage concentration of 12 wt% has been used for 5 months.

[0035] The ion concentration corresponding to the above blackening liquid (calculated at 12wt% concentration) and the measured ion concentration of the newly prepared blackening agent working solution (12wt% blackening liquid + tap water) are shown in the following table:

[0036]

[0037] (1) Take 1 kg of residual heat blackening agent working liquid (for a blackening liquid with a use concentration of 12 wt %, which has been used for 5 months), shake it thoroughly, take 30.0 mL and put it into a 50 mL centrifuge tube, centrifuge it in a high-speed centrifuge, set the maximum relative centrifugal force to 4000 g, and centrifuge it for 15 min; after centrifugation, pour out 29.8 mL of the upper liquid; use it for the subsequent steps;

[0038] (2) taking 1.4 mL of the upper layer liquid after centrifugation in step (1), setting the temperature at 110° C. in a halogen moisture meter for 20 min to dry, and obtaining the effective solid content. The effective solid content of the blackening agent working solution was 3.85%;

[0039] (3) taking 8.0 mL of the upper layer liquid after centrifugation in step (1), adding 12.0 mL of pure water to obtain 20 mL of dilution liquid, the solid content of the dilution liquid being 1.54%;

[0040] (4) Pour 20 mL of the diluted working solution into the upper layer of a 50 mL ultrafiltration centrifuge tube with a cutoff of 10 kD; set the high-speed centrifuge speed to 6700 rpm, the maximum relative centrifugal force to 5000 g, and the centrifugation time to 40 min;

[0041] (5) Take the lower layer liquid after high-speed ultrafiltration in the ultrafiltration centrifuge tube, and separate 6.7 mL of clear liquid. Perform ICP inductively coupled plasma emission spectroscopy analysis. The results are shown in the following table (the data with results less than 1 ppm have been omitted).

[0042] element B Ca Fe K Na P S Si Content / ppm 1.3 24.2 1.1 192.4 229.6 2.1 43.6 17.8

[0043] Based on step (3), the dilution ratio is 2.5 times, so the concentrations of various ions in the blackening agent working solution sample are shown in the following table:

[0044]

[0045] By comparing with the formula, it can be confirmed that the K, Na, and S elements contained in the blackening agent working liquid sample are derived from the blackening agent, which have increased significantly. The B, Ca, and Si elements are exogenous pollution, and the maximum increase within 5 months is only about 50ppm. The pollution degree is relatively low. The operating conditions of the tank liquid are good and can continue to be used stably.

[0046] Comparative Example 1

[0047] The sample solution in Example 2 was analyzed by conventional methods. The only difference between Example 1 and Example 2 is that the diluted sample was directly subjected to ICP analysis after steps (1), (2), and (3). It can be observed that there is a small amount of residue in the instrument pipeline, and additional cleaning is required after each test. The test results are shown in the following table:

[0048]

[0049] Compared with Example 2, the test results of Comparative Example 1 are significantly lower in terms of Ca and Si data; and the test process requires frequent cleaning of the pipeline, which is inefficient.

[0050] The method of the present invention can carry out continuous testing and accurately obtain the content of each element in the waste heat blackening agent working fluid, that is, the method of the present invention improves the accuracy of detecting the element content based on conductivity, thereby effectively identifying the actual contamination of the blackening liquid, and judging whether the waste heat blackening agent working fluid needs to be replaced based on the exogenous contamination it has received during use.

Claims

1. A method for analyzing the inorganic element content of a waste heat blackening agent, characterized in that: The steps include: (1) centrifuging the blackening agent working solution to be tested to separate solid impurities therein; (2) taking 1.50±0.3 mL of the liquid separated in step (1) and drying it to obtain its effective solid content; (3) diluting the liquid separated in step (1) based on the solid content in step (2); pouring the obtained diluted liquid into the upper layer of an ultrafiltration centrifuge tube to separate the resin in the sample; (4) performing elemental analysis on the lower layer liquid separated in step (3) using an ICP inductively coupled plasma emission spectrometer; (5) Calculate the concentration of each element in the sample solution based on the dilution ratio of step (3) and the test results of step (4).

2. The analysis method according to claim 1, characterized in that: In step (1), the maximum relative centrifugal force is 4000-5000 g, and the centrifugation time is 15-20 min.

3. The analysis method according to claim 1, characterized in that: In step (2), a halogen moisture meter is used for drying, the drying temperature is 110-120° C., and the time is 20-30 min.

4. The analysis method according to claim 1, characterized in that: In step (3), the solid content of the diluted solution after dilution is 1.0 to 2.5%.

5. The analysis method according to claim 1, characterized in that: In step (3), the cut-off specification of the centrifugal ultrafiltration tube is 3kD, 10kD or 30kD.

6. The analysis method according to claim 1, characterized in that: In step (3), the size of the ultrafiltration centrifuge tube is 15 mL or 50 mL.

7. The analysis method according to claim 1, characterized in that: In step (3), the speed of the high-speed centrifuge is 6200-8000 rpm, the maximum relative centrifugal force is 5000-6000 g, and the centrifugation time is 30-40 min to separate the liquid.

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