Carbon dot corrosion inhibitor with excellent corrosion inhibition and tracing performance as well as preparation method and application of carbon dot corrosion inhibitor

Abstract

The invention discloses a carbon dot corrosion inhibitor with excellent corrosion inhibition and tracing performance, a preparation method and application, and relates to the technical field of corrosion inhibition of metal materials. The technical problems that in the prior art, a carbon dot corrosion inhibitor is prone to aggregation and instability in a high-temperature and strong-acid environment, and application is single are solved. The method comprises the following steps: firstly, taking citric acid and propargyl-PEG2-amine as raw materials, and dissolving the raw materials in deionized water to obtain a mixed solution; the mixed solution is placed in a high-pressure reaction kettle to be subjected to a hydrothermal reaction, and citric acid carbon dots modified by propargyl-PEG2-amine are prepared; sequentially carrying out centrifugation, dialysis and freeze drying treatment on the citric acid carbon dots modified by the propargyl-PEG2-amine, so as to obtain the citric acid carbon dots modified by the propargyl-PEG2-amine. The prepared carbon dot corrosion inhibitor can be used as a corrosion inhibition material in a high-temperature-resistant strong-acid environment, and can also be used for in-situ monitoring of dichromate ions in industrial wastewater and in-situ monitoring of iron ions and ferrous ions in underground water, surface water and drinking water so as to judge whether the content of the iron ions and the ferrous ions exceeds the standard or not.

Description

Technical Field

[0001] This invention relates to the field of corrosion inhibition technology for metallic materials, specifically to a carbon point corrosion inhibitor with excellent corrosion inhibition and tracing properties, its preparation method, and its application. Background Technology

[0002] N80 steel, with its excellent mechanical properties, weldability, toughness, and impact resistance, is widely used in oil drilling and production, oil and gas transportation, and other fields. However, it is highly susceptible to corrosion during oil well acidizing and industrial pickling processes. To reduce metal corrosion during industrial production, adding corrosion inhibitors to corrosive media has become an economical and effective protective measure. Traditional corrosion inhibitors often contain electronegative heteroatoms or unsaturated bonds such as nitrogen, sulfur, and phosphorus, which can inhibit corrosion by forming an adsorption layer on the metal surface. However, most of them suffer from high toxicity and significant environmental hazards, contradicting the concept of green development. Therefore, developing green, low-cost, and efficient corrosion inhibitors and iron ion stabilizers has become a current research focus.

[0003] The continuous development of industry and manufacturing has led to increasingly serious problems in the discharge of wastewater containing heavy metal ions (such as excess ferric ions) and highly oxidizing oxyacid ions (such as dichromate ions). These pollutants diffuse through the aquatic environment and enter the food chain, posing a serious threat to human health. Dichromate ions are highly carcinogenic, while excess ferric ions can induce organ dysfunction and damage the heart, lungs, liver, and kidneys. Therefore, developing methods that can selectively and sensitively identify specific ions in water is not only of great significance for environmental pollution control but also provides a reference for early-stage corrosion visualization monitoring.

[0004] Carbon dots have attracted widespread attention in various fields such as corrosion protection, bioimaging, energy storage, photocatalysis, and biochemical sensing due to their excellent water solubility, good biocompatibility, low toxicity, and unique fluorescence properties. In the field of corrosion protection, CDs-based materials have demonstrated excellent corrosion inhibition performance as novel green corrosion inhibitors. Significant quantum confinement and edge effects allow electron-rich heteroatom-doped carbon dots to significantly alter their electronic properties. By introducing various functional groups (such as -NH2, -COOH, -SH, -OH), doping provides abundant active sites, significantly enhancing π-electron interactions, metal-ligand coordination, and synergistic effects, thereby promoting the robust adsorption of carbon dots on metal surfaces and contributing to the formation of a uniform protective film. Therefore, carbon dots have been widely used in corrosion protection. Simultaneously, thanks to their tunable optical properties and high quantum yield, CDs are also widely used as fluorescence sensors for various analytes, such as for the detection of iron ions, dichromate ions, chromium ions, and copper ions. Their surface functional groups form complexes with target ions, inducing fluorescence quenching effects and achieving selective identification of analytes. Currently, the main methods for preparing CDs-based materials include hydrothermal / solvent methods, microwave-assisted methods, pyrolysis methods, and electrochemical synthesis methods. In the hydrothermal / solvent method, carbon sources such as citric acid and biomass, along with dopants such as urea and thiourea, are dissolved in water or an organic solvent. The mixture is then placed in a high-pressure reactor and reacted at 160–220°C for 4–12 hours. After cooling, the mixture is centrifuged, dialyzed, and dried to obtain pure carbon dots. However, this method has the following technical problems: First, the reaction is carried out in a closed, high-pressure, heterogeneous system. During the reaction, the carbonization, nucleation, and growth rates of the carbon source cannot be synchronized, easily leading to agglomerates or amorphous carbon black impurities, directly affecting its water solubility. Second, carbon dots prepared using existing technologies cannot be used as carbon dot corrosion inhibitors in high-temperature, strong-acid environments because traditional corrosion inhibitors are prone to aggregation and instability under such conditions. Under high temperature conditions, the surface functional groups (such as carboxyl and hydroxyl groups) of citric acid carbon dots may undergo thermal decomposition or structural changes, resulting in a decrease in their binding ability with the metal surface, thereby reducing the corrosion inhibition efficiency. In addition, high temperature will reduce the Gibbs free energy change of the adsorption process of citric acid carbon dots, causing the adsorption equilibrium to shift towards the desorption direction, resulting in the desorption of corrosion inhibitor molecules from the metal surface, making the protective film unstable or incomplete, and reducing the corrosion inhibition effect.

[0005] In conclusion, further expanding the application of CDs-based materials in the field of corrosion inhibition and developing multifunctional CDs-based materials with both high-efficiency corrosion inhibition and real-time tracing properties has significant scientific research value and practical application prospects. Summary of the Invention

[0006] One of the objectives of this invention is to provide a method for preparing a carbon dot corrosion inhibitor with excellent corrosion inhibition and tracing properties. The carbon dot corrosion inhibitor prepared by this method can be used as a corrosion inhibitor material resistant to high temperature and strong acid environment. It can also be used for in-situ monitoring of dichromate ions in industrial wastewater and ferric ions and ferrous ions in surface water, groundwater and drinking water to determine whether their content exceeds the standard.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a method for preparing a carbon point corrosion inhibitor with excellent corrosion inhibition and tracing properties, comprising the following steps in sequence: a) using citric acid and propargyl-PEG2-amine as raw materials, dissolving them in deionized water to obtain a mixed solution; the molar ratio of citric acid to propargyl-PEG2-amine is 1:2.

[0008] b. The mixed solution is placed in a high-pressure reactor for hydrothermal reaction at a temperature of 150°C for 7-9 hours. During the hydrothermal reaction, the carboxyl group on citric acid undergoes amidation with the amino group in propargyl-PEG2-amine to prepare citric acid carbon dots modified with propargyl-PEG2-amine.

[0009] c. The citric acid carbon dots modified with propargyl-PEG2-amine were subjected to centrifugation, dialysis, and freeze-drying in sequence to obtain the final product.

[0010] In the preparation method of the above-mentioned carbon dot corrosion inhibitor with excellent corrosion inhibition and tracing properties, in step a, citric acid and propargyl-PEG2-amine are dissolved in 15-25 mL of deionized water.

[0011] In the preparation method of the carbon dot corrosion inhibitor with excellent corrosion inhibition and tracing properties described above, the centrifugation step in step c is as follows: the citric acid carbon dots modified with propargyl-PEG2-amine are centrifuged at 10000 rpm to remove particulate matter and collect the clear solution.

[0012] The preparation method of the above-mentioned carbon dot corrosion inhibitor with excellent corrosion inhibition and tracing properties includes the following dialysis steps: the collected clear solution is placed in a dialysis bag with a molecular weight cutoff of 500 Da, and dialyzed in 500 mL of deionized water. The dialysis water is changed every 2 to 3 hours until the dialysis fluid becomes transparent and colorless.

[0013] The preparation method of the above-mentioned carbon dot corrosion inhibitor with excellent corrosion inhibition and tracing properties includes the freeze-drying step of: freeze-drying the solution obtained by dialysis for 70-75 hours to obtain a brown solid product, which is the carbon dot corrosion inhibitor.

[0014] Another object of the present invention is to provide a carbon dot corrosion inhibitor prepared by the above preparation method, wherein the carbon dot corrosion inhibitor has a particle size of 1.881 to 2.595 nm, and comprises a carbon core and a surface layer, wherein the carbon core is a graphitized carbon core, and the surface layer is carbon dots modified by an amidation reaction and modified with propargyl-PEG2-amine.

[0015] Another object of the present invention is to provide the application of the above-mentioned carbon point corrosion inhibitor, which can be applied to a 1 mol / L HCl corrosive environment at a temperature of 30°C or 90°C, and can also be used as a fluorescent probe to monitor ferric ions and ferrous ions in drinking water and dichromate ions in industrial wastewater.

[0016] The above-mentioned carbon dot corrosion inhibitor with excellent corrosion inhibition and tracing properties is applied in a 1 mol / L HCl corrosive environment at temperatures of 30℃ or 90℃. When the carbon dot corrosion inhibitor is protonated, the nitrogen element on its surface coordinates with iron ions and reacts with Cl adsorbed on the iron surface. - Electrostatic attraction occurs, adsorbing onto the metal surface to form a protective layer. At the same time, the PEG2 segments form a hydrophilic hydration layer on the carbon dot surface. Through steric hindrance, the van der Waals attraction between particles is weakened, enhancing the dispersion stability of the carbon dot corrosion inhibitor in the corrosive environment. This results in a dense and uniform protective layer that reduces metal corrosion.

[0017] The above-mentioned carbon dot corrosion inhibitor with excellent corrosion inhibition and tracing properties is used as a fluorescent probe to monitor dichromate ions in industrial wastewater and ferric ions and ferrous ions in surface water, groundwater, and drinking water. The active groups of the carbon dot corrosion inhibitor coordinate with ferric ions and ferrous ions, and undergo redox or electrostatic interactions with dichromate ions, resulting in photoelectric induced transfer or internal filtration effect, which causes fluorescence quenching of the carbon dots, thereby realizing the monitoring of ferric ions, ferrous ions, and dichromate ions.

[0018] Compared with the prior art, the present invention brings the following beneficial technical effects: (1) The present invention overcomes the technical problem that citric acid carbon dots are easy to aggregate and have poor thermal stability in high temperature environment by designing carbon dots with ether bonds, amide groups and PEG2 segments on the surface.

[0019] (2) The carbon dot corrosion inhibitor of the present invention has a better corrosion inhibition effect and can better inhibit metal corrosion, indicating that the adsorption capacity of the citric acid functionalized carbon dot corrosion inhibitor is stronger, and the corrosion inhibitor molecules can be better adsorbed on the metal surface to form a dense adsorption layer.

[0020] (3) The carbon point corrosion inhibitor prepared by the present invention can be applied to high temperature and strong acid corrosion environment, as well as to monitor dichromate ions in industrial wastewater and to monitor iron ions and ferrous ions in surface water, groundwater and drinking water in situ to determine whether their content exceeds the standard, thus breaking through the technical bottleneck of the single performance of carbon point corrosion inhibitor.

[0021] (4) The carbon point corrosion inhibitor prepared by this invention is a green and efficient corrosion inhibitor, low in toxicity and environmentally friendly, with good corrosion inhibition effect, and is a yellow-brown paste at room temperature, which is easily soluble in water and ethanol. The preparation method of this invention is simple to operate, has a short synthesis time, and no harmful substances are generated during the synthesis process. Attached Figure Description

[0022] Figure 1 The particle size analysis and TEM image of the carbon dot corrosion inhibitor prepared in Example 1 of this invention are shown.

[0023] Figure 2 The thermogravimetric analysis diagram is shown for the carbon dot corrosion inhibitor prepared in Example 1 of this invention.

[0024] Figure 3 The image shows the FTIR spectrum of the carbon dot corrosion inhibitor prepared in Example 1 of this invention.

[0025] Figure 4 The diagram shows the corrosion inhibition efficiency of the carbon dot corrosion inhibitor prepared in Example 1 of this invention.

[0026] Figure 5 The image shows a transmission electron microscope (TEM) image of the carbon dot corrosion inhibitor prepared in Comparative Example 2. Detailed Implementation

[0027] This invention proposes a carbon point corrosion inhibitor with excellent corrosion inhibition and tracing properties, its preparation method, and its application. To make the advantages and technical solutions of this invention clearer and more explicit, the invention will be further described below with reference to specific embodiments.

[0028] The propargyl-PEG2-amine mentioned in this invention is an abbreviation for 2-[2-(2-propargyloxy)ethoxy]ethylamine.

[0029] In this invention, the PEG-CD mentioned in the accompanying drawings and specific embodiments refers to the carbon point corrosion inhibitor prepared in Example 1 of this invention. CD in the drawings refers to the carbon point corrosion inhibitor prepared in Comparative Example 1.

[0030] All the raw materials mentioned in this invention can be purchased through commercial channels.

[0031] The technical concept of this invention lies in addressing the problem of existing carbon dot corrosion inhibitors exhibiting unfavorable adsorption-desorption balance at high temperatures, loss of dispersion stability (thermal aggregation), and an inability to simultaneously achieve fluorescent tracking of ferric, ferrous, and dichromate ions. To address this problem, this invention synthesizes citric acid carbon dots with propargyl-PEG2-amine chains on their surface using citric acid and propargyl-PEG2-amine as precursors. In this structure, the amine groups undergo amidation with the carboxyl groups on the carbon dot surface, forming amide bonds; simultaneously, ether bonds in the PEG2 chain segments are introduced into the carbon dot surface framework. The synergistic effect of the amide and ether bonds significantly improves the thermal stability of the carbon dots below 200°C, effectively inhibiting the thermal decomposition of surface functional groups at high temperatures. The PEG2 chains form a hydrophilic hydration layer on the carbon dot surface, weakening van der Waals attraction between particles through steric hindrance, thereby significantly enhancing the dispersion stability of the carbon dots in high-temperature, strongly acidic aqueous solutions, overcoming the shortcomings of traditional corrosion inhibitors that easily aggregate and become unstable in this environment. Furthermore, this carbon dot also possesses fluorescent tracing capabilities, exhibiting specific fluorescent responses to key ions in the corrosion process, such as ferric and ferrous ions, enabling real-time monitoring of target ions in the corrosive microenvironment. It can also be used for monitoring dichromate ions in industrial wastewater and for in-situ monitoring of ferric and ferrous ions in surface water, groundwater, and drinking water.

[0032] The present invention will be further described below with reference to specific embodiments.

[0033] Example 1: A carbon point corrosion inhibitor with excellent corrosion inhibition and tracing properties. The specific steps are as follows: Step 1: Citric acid and propargyl-PEG2-amine (molar ratio 1:2) are used as precursors and dissolved in 20 mL of deionized water. The solution is stirred continuously until it is completely clear.

[0034] Step 2: Subsequently, the mixed solution is transferred to a high-pressure reactor lined with polytetrafluoroethylene and reacted at 150°C for 8 hours. After the reaction is completed, it is allowed to cool naturally to room temperature.

[0035] Step 3: The product obtained in Step 2 is centrifuged at 10,000 rpm to remove large particulate byproducts, yielding a clear solution. This clear solution is placed in a dialysis bag with a molecular weight cutoff of 500 Da and dialyzed in 500 mL of deionized water, with the dialyzing water changed every 2-3 hours until the dialysate becomes clear and colorless. Finally, the purified carbon dot solution is freeze-dried for 72 hours to obtain the carbon dot corrosion inhibitor.

[0036] The carbon dot corrosion inhibitor prepared in this embodiment was subjected to transmission electron microscopy, thermogravimetric analysis, and Fourier transform infrared spectroscopy. Figure 1 , Figure 2 , Figure 3 As shown. From Figure 1The carbon dot corrosion inhibitor obtained has a particle size of 2.238 ± 0.357 nm and exhibits good dispersibility in aqueous solution. Figure 2 Amide bonds, ether bonds, and PEG2 chains have been successfully modified onto carbon point corrosion inhibitors. Figure 3 The synthesized carbon point corrosion inhibitor obtained in this process has excellent thermal stability.

[0037] The carbon dot corrosion inhibitor prepared in Example 1 was transported along with the acidizing fluid to the oil well area and areas prone to pipeline corrosion via a wellhead injection device. When the pipeline corrosion area faces a localized acidic environment, the protonated carbon dot corrosion inhibitor, through coordination with iron ions and the adsorption of Cl on the iron surface… - Electrostatic attraction causes the carbon point corrosion inhibitor to adhere to the metal surface, forming a protective layer and reducing corrosion. In industrial wastewater discharge, carbon point corrosion inhibitors can be made into test strips to detect whether ferric, ferrous, and dichromate ions in industrial wastewater undergo fluorescence quenching under ultraviolet light. Utilizing the active groups such as carboxyl and amide groups on the carbon point corrosion inhibitor, through coordination with ferric and ferrous ions, and through redox or electrostatic interactions with dichromate ions, photoelectric induced transfer or internal filtration effects cause the carbon points to quench fluorescence. This allows for the monitoring of dichromate ions in industrial wastewater and the detection of ferric and ferrous ions in surface water or drinking water.

[0038] Application Example 1: A static corrosion performance evaluation experiment was used to measure the corrosion inhibition performance of the carbon dot corrosion inhibitor prepared in the example. The specific experiment was as follows: Before weighing, N80 steel was first polished with 400, 800, and 1200 grit sandpaper in sequence, then cleaned with deionized water and anhydrous ethanol, and finally dried with cold air. N80 steel samples were immersed in 1M HCl aqueous solutions containing different concentrations of carbon dot corrosion inhibitor at 303K for 12 hours. After immersion, they were removed, immersed in anhydrous ethanol for 30 minutes to dehydrate, dried with cold air, rinsed, wiped dry, and placed in an ultrasonic cleaner for 10 minutes to remove surface corrosion. After drying with cold air, the samples were weighed. Based on the weight change of the samples, the corrosion inhibition efficiency of the carbon dot corrosion inhibitor and the solution corrosion rate were calculated. The corrosion inhibition efficiency was combined with... Figure 4 As shown in Table 1, Table 1 shows the corrosion inhibition efficiency of N80 steel in 1M HCl solution at 303K with different concentrations of carbon point corrosion inhibitor.

[0039] Table 1

[0040] As shown in Table 1, the N80 steel strips experienced the greatest mass loss in the blank samples, indicating severe corrosion. After adding the carbon point corrosion inhibitor, the mass loss of the strips decreased significantly with increasing concentration, demonstrating a significant corrosion inhibition effect. When the inhibitor concentration was 500 mg / L, the corrosion inhibition efficiency reached 98.67%.

[0041] Application Example 2: A static corrosion performance evaluation experiment was used to measure the corrosion inhibition performance of the carbon dot corrosion inhibitor prepared in Example 1. The specific experiment was as follows: Before weighing, N80 steel was first polished with 400, 800, and 1200 grit sandpaper in sequence, then cleaned with deionized water and anhydrous ethanol, and finally dried with cold air for later use. N80 steel samples were immersed in 1M HCl aqueous solutions containing different concentrations of carbon dot corrosion inhibitor at 363K for 12 hours. After immersion, they were removed, immersed in anhydrous ethanol for 30 minutes to dehydrate, dried with cold air, rinsed, and the surface was wiped dry before being placed in an ultrasonic cleaner for 10 minutes to remove surface corrosion. After drying with cold air, the samples were weighed. Based on the weight changes of the samples, the corrosion inhibition efficiency of the carbon dot corrosion inhibitor and the solution corrosion rate were calculated, as shown in Table 2. Table 2 shows the corrosion inhibition efficiency of N80 steel in 1M HCl solution at 363K with different concentrations of carbon dot corrosion inhibitor.

[0042] Table 2

[0043] As shown in Table 2, the N80 steel plate experienced the greatest mass loss in the blank samples, indicating severe corrosion. After adding the carbon point corrosion inhibitor prepared in Example 1, the mass loss of the plate decreased significantly with increasing concentration, demonstrating a significant corrosion inhibition effect. When the concentration of the carbon point corrosion inhibitor was 500 mg / L, the corrosion inhibition efficiency reached 99.20%.

[0044] Application Example 3: The carbon dot corrosion inhibitor prepared in Example 1 was applied to industrial wastewater. The specific steps were as follows: a series of mixed solutions of 100 mg / L carbon dot corrosion inhibitor containing iron ions with concentrations of 0, 0.1, 0.5, 1.0, 5.0, 10.0, 50.0, and 100.0 mg / L were prepared, and their quenching efficiency was analyzed using a fluorescence spectrophotometer, as shown in Table 3. Table 3 shows the quenching efficiency of carbon dot corrosion inhibitor solutions containing different concentrations of iron ions.

[0045] Table 3

[0046] Fluorescence spectroscopy revealed that the fluorescence intensity decreased with increasing iron ion concentration, and the quenching efficiency reached a maximum of 73.12%. This indicates that carbon dot corrosion inhibitors can be used as fluorescent probes to detect iron ions in industrial wastewater.

[0047] Application Example 4: The carbon dot corrosion inhibitor prepared in Example 1 was applied to industrial wastewater. The specific steps were as follows: a series of mixed solutions of 100 mg / L carbon dot corrosion inhibitor containing ferrous ions with concentrations of 0, 0.1, 0.5, 1.0, 5.0, 10.0, 50.0, and 100.0 mg / L were prepared, and their quenching efficiency was analyzed using a fluorescence spectrophotometer, as shown in Table 4. Table 4 shows the quenching efficiency of carbon dot corrosion inhibitor solutions containing different concentrations of ferrous ions.

[0048] Table 4

[0049] Fluorescence spectroscopy revealed that fluorescence intensity decreased with increasing ferrous ion concentration, and the quenching efficiency reached a maximum of 43.84%. This indicates that carbon dot corrosion inhibitors can be used as fluorescent probes to detect ferrous ions in surface water or drinking water.

[0050] Application Example 5: The carbon dot corrosion inhibitor prepared in Example 1 was applied to industrial wastewater. The specific steps were as follows: a series of mixed solutions of carbon dot corrosion inhibitor containing dichromate ions at concentrations of 0, 0.1, 0.5, 1.0, 5.0, 10.0, 50.0, and 100.0 mg / L were prepared, and their quenching efficiency was analyzed using a fluorescence spectrophotometer, as shown in Table 5. Table 5 shows the quenching efficiency of carbon dot corrosion inhibitor solutions containing different concentrations of dichromate ions.

[0051] Table 5

[0052] Fluorescence spectroscopy revealed that fluorescence intensity decreased with increasing dichromate ion concentration, with a quenching efficiency reaching a maximum of 66.02%. This indicates that carbon dot corrosion inhibitors can be used as fluorescent probes to detect iron ions in industrial wastewater.

[0053] Application Example 6: The carbon dot corrosion inhibitor prepared in Example 1 was applied to industrial wastewater. The specific steps were as follows: a series of mixed solutions of 100 mg / L carbon dot corrosion inhibitor containing iron ions with concentrations of 0, 0.1, 0.5, 1.0, 5.0, 10.0, 50.0 and 100.0 mg / L were prepared, and the detection limit of PEG-CD for iron ions was calculated using formula (1) and formula (2), as shown in Table 6. Table 6 shows the quenching efficiency of carbon dot corrosion inhibitor solutions containing different concentrations of iron ions.

[0054] (1).

[0055] (2).

[0056] In formula (1): F0 represents the fluorescence intensity of the carbon point corrosion inhibitor, F represents the fluorescence intensity containing ferrous, ferrous, or dichromate ions, and K sv represents the Stern-Volmer constant, and C represents the concentration of ferric ions, ferrous ions, or dichromate ions.

[0057] In equation (2): S represents the standard deviation of the fluorescence intensity of the carbon dot corrosion inhibitor fluorescent probe system itself when no target analyte is added; b represents the slope of the calibration curve (Kvs); LOD represents the detection limit; and k represents the confidence factor (usually taken as 3).

[0058] Table 6

[0059] As shown in Table 6, the detection limit of carbon point corrosion inhibitor for iron ions is 0.105 mg / L, which can be used to monitor the iron ion content in surface water, groundwater and drinking water.

[0060] Application Example 7: The carbon dot corrosion inhibitor prepared in Example 1 was applied to industrial wastewater. The specific steps were as follows: a series of PEG-CD mixed solutions containing ferrous ions at concentrations of 0, 0.1, 0.5, 1.0, 5.0, 10.0, 50.0, and 100.0 mg / L were prepared, and the detection limit of PEG-CD for ferrous ions was calculated using formulas (1) and (2), as shown in Table 7. Table 7 shows the quenching efficiency of carbon dot corrosion inhibitor solutions containing different concentrations of ferrous ions.

[0061] Table 7

[0062] As shown in Table 7, the detection limit of carbon point corrosion inhibitor for ferrous ions is 0.19 mg / L, which can be used to monitor the ferrous ion content in surface water, groundwater and drinking water.

[0063] Application Example 8: The carbon point corrosion inhibitor prepared in Example 1 was applied to industrial wastewater. The specific steps were as follows: a series of carbon point corrosion inhibitor mixed solutions containing dichromate ions at concentrations of 0, 0.1, 0.5, 1.0, 5.0, 10.0, 50.0, and 100.0 mg / L were prepared, and the detection limit of PEG-CD for dichromate ions was calculated using formulas (1) and (2), as shown in Table 8. Table 8 shows the quenching efficiency of carbon point corrosion inhibitor solutions containing different concentrations of dichromate ions.

[0064] Table 8

[0065] Table 8 shows that the detection limit of carbon point corrosion inhibitor for ferrous ions is 0.11 mg / L, which can be used to monitor the dichromate ion content in industrial wastewater.

[0066] Comparative Example 1: Unlike Example 1, no propargyl-PEG2-amine was added.

[0067] The specific steps are as follows: Step 1: Dissolve citric acid in 20 mL of deionized water and stir continuously until the solution is completely clear.

[0068] Step 2: Subsequently, the mixed solution is transferred to a high-pressure reactor lined with polytetrafluoroethylene and reacted at 150°C for 8 hours. After the reaction is completed, it is allowed to cool naturally to room temperature.

[0069] Step 3: The product obtained in Step 2 is centrifuged at 10,000 rpm to remove large particulate byproducts, yielding a clear solution. This clear solution is placed in a dialysis bag with a molecular weight cutoff of 500 Da and dialyzed in 500 mL of deionized water, with the dialyzing water changed every 2-3 hours until the dialysate becomes clear and colorless. Finally, the purified carbon dot solution is freeze-dried for 72 hours to obtain the carbon dot corrosion inhibitor.

[0070] The carbon dot corrosion inhibitor prepared in Comparative Example 1 was applied using the same steps as in Example 1. The effects of the carbon dot corrosion inhibitor prepared in Comparative Example 1 and the carbon dot corrosion inhibitor prepared in Example 1 were compared. Figure 2 , 3 As shown in Tables 4, 9, and 10, Table 9 shows the temperature at 303K and Table 10 shows the temperature at 363K.

[0071] Table 9

[0072] Table 10

[0073] Comparative Example 1: The corrosion inhibition performance of the citric acid carbon dot corrosion inhibitor without propargyl-PEG2-amine modification was 65.57% and 31.74% at 30℃ and 90℃, respectively. Therefore, the corrosion inhibition performance of the citric acid carbon dot corrosion inhibitor without propargyl-PEG2-amine modification was poor.

[0074] Comparative Example 2: The difference from Example 1 is that the hydrothermal reaction temperature is 180°C.

[0075] The specific steps are as follows: Step 1: Use citric acid and propargyl-PEG2-amine (molar ratio 1:2) as precursors, dissolve them in 20 mL of deionized water, and stir continuously until the solution is completely clear.

[0076] Step 2: Subsequently, the mixed solution is transferred to a high-pressure reactor lined with polytetrafluoroethylene and reacted at 180°C for 8 hours. After the reaction is completed, it is allowed to cool naturally to room temperature.

[0077] Step 3: The product obtained in Step 2 is centrifuged at 10,000 rpm to remove large particulate byproducts, yielding a clear solution. This clear solution is placed in a dialysis bag with a molecular weight cutoff of 500 Da and dialyzed in 500 mL of deionized water, with the dialyzing water changed every 2-3 hours until the dialysate becomes clear and colorless. Finally, the purified carbon dot solution is freeze-dried for 72 hours to obtain the carbon dot corrosion inhibitor.

[0078] The carbon dot corrosion inhibitor prepared in Comparative Example 2 was tested, and its effect was as follows: Figure 5 As shown, citric acid carbon dots synthesized at 180℃ tend to aggregate and have poor dispersibility in aqueous solutions, which is not conducive to the uniform adsorption of the carbon dot corrosion inhibitor protective film on the metal surface.

[0079] Any parts not mentioned in this invention can be achieved by referring to existing technologies.

[0080] Those skilled in the art should recognize that the above embodiments are merely illustrative of this application and are not intended to limit this application. Any appropriate changes and variations made to the above embodiments within the essential spirit and scope of this application fall within the scope of protection of the claims of this application.

Claims

1. A method for preparing a carbon point corrosion inhibitor with excellent corrosion inhibition and tracing properties, characterized in that, The steps are as follows: a. Using citric acid and propargyl-PEG2-amine as raw materials, dissolve them in deionized water to obtain a mixed solution; The molar ratio of citric acid to propargyl-PEG2-amine is 1:2; b. The mixed solution is placed in a high-pressure reactor for hydrothermal reaction at a temperature of 150°C for 7-9 hours. During the hydrothermal reaction, the carboxyl group on citric acid undergoes amidation reaction with the amino group in propargyl-PEG2-amine to prepare citric acid carbon dots modified with propargyl-PEG2-amine. c. The citric acid carbon dots modified with propargyl-PEG2-amine were subjected to centrifugation, dialysis, and freeze-drying in sequence to obtain the final product.

2. The method for preparing a carbon dot corrosion inhibitor with excellent corrosion inhibition and tracing properties according to claim 1, characterized in that: In step a, citric acid and propargyl-PEG2-amine are dissolved in 15-25 mL of deionized water.

3. The method for preparing a carbon dot corrosion inhibitor with excellent corrosion inhibition and tracing properties according to claim 1, characterized in that: In step c, the centrifugation process is as follows: the citric acid carbon dots modified with propargyl-PEG2-amine are centrifuged at 10,000 rpm to remove particulate matter and collect the clear solution.

4. The method for preparing a carbon dot corrosion inhibitor with excellent corrosion inhibition and tracing properties according to claim 3, characterized in that: The dialysis procedure is as follows: Place the collected clear solution in a dialysis bag with a molecular weight cutoff of 500 Da, and dialyze it in 500 mL of deionized water. Change the dialysis water every 2 to 3 hours until the dialysate becomes clear and colorless.

5. The method for preparing a carbon dot corrosion inhibitor with excellent corrosion inhibition and tracing properties according to claim 4, characterized in that: The freeze-drying process involves freeze-drying the solution obtained from dialysis for 70–75 hours to obtain a brown solid product, which is the carbon point corrosion inhibitor.

6. A carbon point corrosion inhibitor with excellent corrosion inhibition and tracing properties, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 5. The carbon dot corrosion inhibitor has a particle size of 1.881 to 2.595 nm and includes a carbon core and a surface layer. The carbon core is a graphitized carbon core, and the surface layer is carbon dots modified by an amidation reaction and modified with propargyl-PEG2-amine.

7. The application of the carbon point corrosion inhibitor with excellent corrosion inhibition and tracing properties according to claim 6, characterized in that: The applications include carbon point corrosion inhibitors, which can be used in 1 mol / L HCl corrosive environments at temperatures of 30℃ or 90℃, and can also be used as fluorescent probes to monitor ferric and ferrous ions in groundwater, surface water, and drinking water, and to monitor dichromate ions in industrial wastewater.

8. The application of the carbon point corrosion inhibitor with excellent corrosion inhibition and tracing properties according to claim 7, characterized in that: When carbon dot corrosion inhibitors are applied in a 1 mol / L HCl corrosive environment at temperatures of 30℃ or 90℃, the nitrogen elements on the surface of the carbon dot corrosion inhibitor are protonated and coordinate with iron ions, and then react with the Cl adsorbed on the iron surface. - Electrostatic attraction occurs, adsorbing onto the metal surface to form a protective layer. At the same time, the PEG2 segments form a hydrophilic hydration layer on the carbon dot surface. Through steric hindrance, the van der Waals attraction between particles is weakened, enhancing the dispersion stability of the carbon dot corrosion inhibitor in the corrosive environment. This results in a dense and uniform protective layer that reduces metal corrosion.

9. The application of the carbon point corrosion inhibitor with excellent corrosion inhibition and tracing properties according to claim 7, characterized in that: When the carbon dot corrosion inhibitor is used as a fluorescent probe to monitor dichromate ions in industrial wastewater and ferric ions and ferrous ions in surface water, groundwater, and drinking water, the active groups of the carbon dot corrosion inhibitor coordinate with ferric ions and ferrous ions, and undergo redox or electrostatic interactions with dichromate ions, resulting in photoelectric induced transfer or internal filtration effect, which causes the carbon dots to undergo fluorescence quenching, thereby realizing the monitoring of ferric ions, ferrous ions, and dichromate ions.

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