Preparation method of polyepoxysuccinic acid modified sulfur quantum dot scale inhibitor and antibacterial agent

Abstract

This application discloses a method for preparing a polyepoxysuccinic acid-modified sulfur quantum dot scale inhibitor and antibacterial agent, belonging to the field of water treatment nanomaterials. The method includes: preparing nitrogen-doped sulfur quantum dots; reacting polyepoxysuccinic acid or its derivatives with nitrogen-doped sulfur quantum dots to obtain a composite product; purifying the composite product; and concentrating, drying, and grinding the purified composite product to obtain the scale inhibitor and antibacterial agent. This application modifies the surface functional groups of sulfur quantum dots with polyepoxysuccinic acid or its derivatives, endowing the product with abundant active functional groups. This allows the product to inhibit the formation of calcium carbonate scale through chelation solubilization, crystal form regulation, and adsorption dispersion mechanisms, while retaining the intrinsic antibacterial properties of sulfur quantum dots, effectively inhibiting bacterial growth in water while inhibiting scale formation. This preparation method is environmentally friendly, with mild reaction conditions, and the resulting scale inhibitor and antibacterial agent has good reservoir compatibility, making it suitable for high-salinity and high-temperature environments in oil fields.

Description

Technical Field

[0001] This application relates to the field of water treatment nanomaterials technology, and in particular to a method for preparing a polyepoxysuccinic acid modified sulfur quantum dot scale inhibitor and antibacterial agent. Background Technology

[0002] During water injection development in oilfields, poor water quality compatibility and changes in temperature and pressure can easily lead to the formation of calcium carbonate scale in pipelines and reservoirs, resulting in decreased production efficiency. Simultaneously, scale formation is often accompanied by bacterial growth, creating a vicious cycle of "scale formation-bacterial growth-corrosion." Adding scale inhibitors is the primary control measure. Traditional organophosphonate scale inhibitors pose environmental risks, while green scale inhibitors such as polyepoxysuccinic acid (PESA) have limited effectiveness in high-mineralization and high-temperature environments. Although sulfur quantum dots (SQDs) possess nanoscale effects and antibacterial potential, their insufficient surface functional groups result in poor scale inhibition when used alone.

[0003] Therefore, there is an urgent need to develop a multifunctional oilfield water treatment agent that combines efficient scale inhibition and antibacterial properties with a green and environmentally friendly process. Summary of the Invention

[0004] This application provides a method for preparing a polyepoxysuccinic acid modified sulfur quantum dot scale inhibitor and antibacterial agent, which solves the problems mentioned in the background art.

[0005] In a first aspect, embodiments of this application provide a method for preparing a polyepoxysuccinic acid modified sulfur quantum dot scale inhibitor and antibacterial agent, comprising: S1: Preparation of nitrogen-doped sulfur quantum dots; S2: Polyepoxysuccinic acid or its derivatives are combined with the nitrogen-doped sulfur quantum dots to obtain a composite product; S3: Purify the composite product; S4: The purified composite product is concentrated, dried and ground to obtain the scale inhibitor and antibacterial agent.

[0006] In conjunction with the first aspect, in one possible implementation, step S2 includes: S21: Polyepoxysuccinate is pretreated by acidification to obtain polyepoxysuccinic acid; S22: The polyepoxysuccinic acid obtained in step S21 is combined with the nitrogen-doped sulfur quantum dots prepared in step S1 at a mass ratio of (8-12):1 to obtain polyepoxysuccinic acid modified sulfur quantum dots.

[0007] In conjunction with the first aspect, in one possible implementation, step S21 includes: Sodium polyepoxysuccinate was weighed and dissolved in distilled water. Concentrated hydrochloric acid was added dropwise to adjust the pH to 2. Anhydrous ethanol was added and allowed to stand to precipitate a white solid. After washing, drying and grinding, polyepoxysuccinic acid was obtained. Step S22 includes: The prepared polyepoxysuccinic acid and nitrogen-doped sulfur quantum dots were dissolved in distilled water at a mass ratio of 10:1. The pH was adjusted to 7-8 with sodium hydroxide solution, and the mixture was stirred and heated at 80℃ for 24 hours. After cooling, the mixture was filtered through a filter membrane. Anhydrous ethanol was added to the filtrate and allowed to stand to precipitate. After washing, the precipitate was concentrated by rotary evaporation and dried to obtain polyepoxysuccinic acid modified sulfur quantum dots.

[0008] In conjunction with the first aspect, in one possible implementation, step S2 further includes preparing a derivative of polyepoxysuccinic acid: S23: Polyepoxysuccinic acid is modified by reacting it with thiourea or urea to obtain thiourea-modified polyepoxysuccinic acid or urea-modified polyepoxysuccinic acid respectively. S24: The thiourea-modified polyepoxysuccinic acid or urea-modified polyepoxysuccinic acid obtained in step S23 is reacted with the nitrogen-doped sulfur quantum dots obtained in step S1 to obtain thiourea-modified polyepoxysuccinic acid-modified sulfur quantum dots or urea-modified polyepoxysuccinic acid-modified sulfur quantum dots.

[0009] In conjunction with the first aspect, in one possible implementation, step S23 includes: Polyepoxysuccinic acid was dissolved in distilled water with thiourea or urea at a mass ratio of (2-3):1. The pH was adjusted to 7 with sodium hydroxide solution. The mixture was stirred at 85°C for 1.5 h until it became viscous. After filtration to remove impurities, it was dried under vacuum to obtain thiourea-modified polyepoxysuccinic acid or urea-modified polyepoxysuccinic acid. Step S24 includes: The nitrogen-doped sulfur quantum dots obtained in step S1 and the thiourea-modified polyepoxysuccinic acid or urea-modified polyepoxysuccinic acid obtained in step S23 were dissolved in deionized water at a mass ratio of (10-15):1. The pH was adjusted to 7 with sodium hydroxide solution, heated at 80°C for 24 hours, cooled, and then anhydrous ethanol was added to allow precipitation. After washing, the mixture was concentrated by rotary evaporation and dried at 60°C to obtain thiourea-modified polyepoxysuccinic acid-modified sulfur quantum dots or urea-modified polyepoxysuccinic acid-modified sulfur quantum dots.

[0010] In conjunction with the first aspect, in one possible implementation, in step S1, the raw materials for preparing nitrogen-doped sulfur quantum dots include sublimed sulfur, sodium hydroxide, and L-cysteine. In step S2, the conditions for the composite reaction include: pH adjusted to 7-8, reaction temperature at 80-90℃, and reaction time at 1.5-24h.

[0011] In conjunction with the first aspect, in one possible implementation, in step S3, the purification process includes at least one of microporous membrane filtration and dialysis; In step S4, the drying method is vacuum drying.

[0012] In conjunction with the first aspect, in one possible implementation, the nitrogen-doped sulfur quantum dots, the polyepoxysuccinic acid, and the derivatives of the polyepoxysuccinic acid are in powder or solution form before the reaction.

[0013] Secondly, this application provides a polyepoxysuccinic acid and its derivatives modified sulfur quantum dot scale inhibitor and antibacterial agent prepared according to the preparation method of the first aspect or any possible implementation of the first aspect.

[0014] In conjunction with the second aspect, in one possible implementation, the scale inhibitor / bacteriostatic agent has a surface rich in one or more functional groups selected from carboxyl, amide, carbonyl, and thiocarbonyl groups; and / or has a particle size of 3.5-4.5 nm.

[0015] One or more technical solutions provided in the embodiments of this application have at least the following technical effects: The preparation method provided in this application, which first prepares nitrogen-doped sulfur quantum dots, then reacts them with polyepoxysuccinic acid or its derivatives, and finally purifies, concentrates, dries, and grinds them to obtain a scale inhibitor and antibacterial agent, brings the following technical effects: This preparation process is green and environmentally friendly, employing a composite modification process, using environmentally friendly and readily available raw materials, with mild reaction conditions and low energy consumption, avoiding the pollution problems in the synthesis process of traditional chemical scale inhibitors; by modifying the surface functional groups of sulfur quantum dots with polyepoxysuccinic acid or its derivatives, the product is endowed with abundant active functional groups, enabling it to… This compound product effectively inhibits the formation of calcium carbonate scale through a triple mechanism of chelation solubilization, crystal form regulation, and adsorption dispersion. At the same time, it retains the intrinsic antibacterial properties of sulfur quantum dots, effectively inhibiting bacterial growth in water while inhibiting scale formation. This breaks the vicious cycle of "scale formation-bacterial growth-corrosion" in oilfields and achieves synergistic effects of scale inhibition and antibacterial action. In addition, this scale inhibitor and antibacterial agent has good reservoir compatibility, is suitable for high-salinity and high-temperature environments in oilfields, has a low core damage rate, and can meet the requirements of water injection in oilfields. It provides a clear structure-activity relationship reference for the structural design of multifunctional water treatment agents. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments of this application will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 A schematic diagram of the preparation process of polyepoxysuccinic acid and its derivatives modified sulfur quantum dot scale inhibitors and antibacterial agents provided in the embodiments of this application; Figure 2Transmission electron microscopy (TEM) image and particle size distribution diagram of the polyepoxysuccinic acid modified sulfur quantum dot scale inhibitor prepared in the embodiments of this application; Figure 3 Infrared spectrum of the polyepoxysuccinic acid and its derivatives modified sulfur quantum dot scale inhibitor provided in the embodiments of this application; Figure 4 A comparison chart of scale inhibition rate test results of the polyepoxysuccinic acid and its derivatives modified sulfur quantum dot scale inhibitors provided in the embodiments of this application; Figure 5 Comparison of core displacement test results of the polyepoxysuccinic acid and its derivatives modified sulfur quantum dot scale inhibitors provided in the embodiments of this application; Figure 6 A comparison of the antibacterial effects of the CSN-PESA-SQDs scale inhibitor and antibacterial agent prepared according to the embodiments of this application. Detailed Implementation

[0018] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0019] In the description of the embodiments of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the embodiments of this application and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. The terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application according to the specific circumstances.

[0020] This application provides a method for preparing a polyepoxysuccinic acid modified sulfur quantum dot scale inhibitor and antibacterial agent, such as... Figure 1 As shown, it includes: S1: Preparation of nitrogen-doped sulfur quantum dots.

[0021] S2: Polyepoxysuccinic acid or its derivatives are combined with nitrogen-doped sulfur quantum dots to obtain a composite product.

[0022] S3: Purify the composite product.

[0023] S4: The purified composite product is concentrated, dried and ground to obtain a scale inhibitor and antibacterial agent.

[0024] The preparation method provided in this application involves first preparing nitrogen-doped sulfur quantum dots, then reacting them with polyepoxysuccinic acid or its derivatives, followed by purification, concentration, drying, and grinding to obtain a scale inhibitor and antibacterial agent. This method, on the one hand, modifies the surface functional groups of sulfur quantum dots with polyepoxysuccinic acid or its derivatives, endowing the product with abundant active groups such as carboxyl, amide, carbonyl, and thiocarbonyl groups. This enables the product to efficiently inhibit the formation of calcium carbonate scale through a triple mechanism of chelation solubilization, crystal form regulation, and adsorption dispersion, overcoming the shortcomings of insufficient scale inhibition capacity of single sulfur quantum dots and the performance degradation of traditional green scale inhibitors in high-salinity environments. On the other hand, the composite product retains the intrinsic antibacterial properties of sulfur quantum dots, working synergistically with the functional groups to effectively inhibit bacterial growth in water while inhibiting scale, breaking the vicious cycle of "scale formation-bacterial growth-corrosion" in oilfields. Furthermore, this preparation method uses mild reaction conditions and is environmentally friendly. The resulting scale inhibitor and antibacterial agent can achieve high-efficiency scale inhibition and complete antibacterial action with low dosage, providing an integrated solution for oilfield water treatment.

[0025] In this embodiment of the application, step S2 includes: S21: Polyepoxysuccinate is pretreated by acidification to obtain polyepoxysuccinic acid.

[0026] S22: The polyepoxysuccinic acid obtained in step S21 is combined with the nitrogen-doped sulfur quantum dots prepared in step S1 at a mass ratio of (8-12):1 to obtain polyepoxysuccinic acid modified sulfur quantum dots.

[0027] In this embodiment of the application, step S21 includes: Sodium polyepoxysuccinate was weighed and dissolved in distilled water. Concentrated hydrochloric acid was added dropwise to adjust the pH to 2. Anhydrous ethanol was added and allowed to stand to precipitate a white solid. After washing, drying and grinding, polyepoxysuccinic acid was obtained. Step S22 includes: The prepared polyepoxysuccinic acid and nitrogen-doped sulfur quantum dots were dissolved in distilled water at a mass ratio of 10:1. The pH was adjusted to 7-8 with sodium hydroxide solution, and the mixture was stirred and heated at 80℃ for 24 hours. After cooling, the mixture was filtered through a filter membrane. Anhydrous ethanol was added to the filtrate and allowed to stand to precipitate. After washing, the precipitate was concentrated by rotary evaporation and dried to obtain polyepoxysuccinic acid modified sulfur quantum dots.

[0028] It should be noted that in the embodiments of this application, the acidification pretreatment of polyepoxysuccinate by S21 can remove salt ions and obtain pure polyepoxysuccinic acid, providing active sites for its subsequent covalent bonding with sulfur quantum dots; then, in S22, polyepoxysuccinic acid and nitrogen-doped sulfur quantum dots are reacted at a preferred mass ratio of 10:1 at pH 7. 8. A composite reaction was carried out at 80℃ for 24 hours, followed by membrane filtration, anhydrous ethanol precipitation, washing, rotary evaporation concentration, and drying to obtain polyepoxysuccinic acid-modified sulfur quantum dots. This preparation process is mild and controllable. In the obtained product, polyepoxysuccinic acid is covalently and stably modified on the surface of sulfur quantum dots, significantly increasing the density of active functional groups such as carboxyl groups. This gives the product a triple scale inhibition mechanism of chelation solubilization, crystal distortion, and adsorption dispersion. Simultaneously, it retains the intrinsic antibacterial properties of sulfur quantum dots, achieving a scale inhibition rate of >85% for calcium carbonate scale at extremely low dosages (e.g., 20 mg / L), while also inhibiting bacterial growth. This effectively overcomes the problems of poor scale inhibition capacity of single sulfur quantum dots, the single function of traditional scale inhibitors, and easy failure under high salinity, providing a highly efficient, environmentally friendly, and dual-functional integrated solution for oilfield water treatment.

[0029] In this embodiment of the application, step S2 further includes preparing a derivative of polyepoxysuccinic acid: S23: Polyepoxysuccinic acid is modified by reacting it with thiourea or urea to obtain thiourea-modified polyepoxysuccinic acid or urea-modified polyepoxysuccinic acid.

[0030] S24: The thiourea-modified polyepoxysuccinic acid or urea-modified polyepoxysuccinic acid obtained in step S23 is reacted with the nitrogen-doped sulfur quantum dots obtained in step S1 to obtain thiourea-modified polyepoxysuccinic acid-modified sulfur quantum dots or urea-modified polyepoxysuccinic acid-modified sulfur quantum dots.

[0031] In this embodiment of the application, step S23 includes: Polyepoxysuccinic acid was dissolved in distilled water with thiourea or urea at a mass ratio of (2-3):1. The pH was adjusted to 7 with sodium hydroxide solution. The mixture was stirred at 85°C for 1.5 h until it became viscous. After filtration to remove impurities, it was dried under vacuum to obtain thiourea-modified polyepoxysuccinic acid or urea-modified polyepoxysuccinic acid. Step S24 includes: The nitrogen-doped sulfur quantum dots obtained in step S1 and the thiourea-modified polyepoxysuccinic acid or urea-modified polyepoxysuccinic acid obtained in step S23 were dissolved in deionized water at a mass ratio of (10-15):1. The pH was adjusted to 7 with sodium hydroxide solution, heated at 80°C for 24 hours, cooled, and then anhydrous ethanol was added to allow precipitation. After washing, the mixture was concentrated by rotary evaporation and dried at 60°C to obtain thiourea-modified polyepoxysuccinic acid-modified sulfur quantum dots or urea-modified polyepoxysuccinic acid-modified sulfur quantum dots.

[0032] It should be noted that in the embodiments of this application, in step S23, polyepoxysuccinic acid is stirred with thiourea or urea at a mass ratio of (2-3):1 at pH 7 and 85°C for 1.5 h until it becomes viscous. After filtration and vacuum drying, thiourea-modified polyepoxysuccinic acid or urea-modified polyepoxysuccinic acid is obtained. This step successfully introduces a thiocarbonyl group (C=S) or an additional amide group (-CONH2) into the molecular structure of polyepoxysuccinic acid, which significantly enriches the types and density of functional groups. Then, in step S24, the obtained derivative is reacted with nitrogen-doped sulfur quantum dots at a mass ratio of (10-15):1 at pH 7 and 80°C for 24 h. After precipitation, washing and drying, the final product is obtained. This technical approach leverages the strong C=S coordination groups introduced by thiourea to enhance the chelation and capture ability of calcium ions. Simultaneously, it utilizes the synergistic effect of the -CONH2 group introduced by urea and the existing -COOH group to significantly improve lattice distortion and dispersion performance. This results in thiourea-modified polyepoxysuccinic acid-modified sulfur quantum dots achieving a scale inhibition rate of over 88% against calcium carbonate at a dosage of 20 mg / L, with the urea-modified product reaching as high as 90.8%. Furthermore, derivative modification further optimizes the surface microenvironment of the sulfur quantum dots, enhancing their interaction with bacterial cell membranes. This allows the composite product to achieve an antibacterial rate of over 85% at concentrations of 125-150 mg / L, and complete antibacterial activity at 180 mg / L. Through functional group-oriented design and optimized composite ratios, this solution achieves a stepwise improvement in scale inhibition performance and a synergistic enhancement of antibacterial function, providing a controllable and multifunctional water treatment agent solution for the differentiated needs of various oilfield water quality conditions.

[0033] In this embodiment of the application, in step S1, the raw materials for preparing nitrogen-doped sulfur quantum dots include sublimed sulfur, sodium hydroxide, and L-cysteine.

[0034] In step S2, the conditions for the composite reaction include: pH adjusted to 7-8, reaction temperature at 80-90℃, and reaction time at 1.5-24h.

[0035] In this embodiment of the application, step S3, the purification process includes at least one of microporous membrane filtration and dialysis.

[0036] In step S4, the drying method is vacuum drying.

[0037] In the embodiments of this application, nitrogen-doped sulfur quantum dots, polyepoxysuccinic acid, and derivatives of polyepoxysuccinic acid are in powder or solution form before the reaction.

[0038] In the embodiments of this application, the polyepoxysuccinic acid and its derivatives modified sulfur quantum dot scale inhibitor and antibacterial agent are prepared according to the above-described preparation method.

[0039] In the embodiments of this application, the scale inhibitor and antibacterial agent has a surface rich in one or more functional groups, including carboxyl, amide, carbonyl and thiocarbonyl groups, and its particle size is 3.5-4.5 nm.

[0040] This application relates to the application of the aforementioned scale inhibitor and antibacterial agent in oilfield water treatment, wherein the scale inhibitor and antibacterial agent is used to inhibit the formation of calcium carbonate scale and inhibit the growth of bacteria in water.

[0041] In this embodiment, the concentration of the scale inhibitor and antibacterial agent in the water is 10-180 mg / L. Preferably, the concentration for scale inhibition is 20-50 mg / L, and the concentration for full antibacterial function is 180 mg / L.

[0042] All reagents used in this application are of analytical grade and can be purchased from conventional biochemical reagent companies unless otherwise specified. The experimental water is deionized water.

[0043] Example 1: Preparation of nitrogen-doped sulfur quantum dots (N-SQDs) Weigh 11.4 g of sublimed sulfur, 32.4 g of sodium hydroxide, and an appropriate amount of L-cysteine, dissolve them in 570 mL of distilled water, and stir and heat at 90 °C for 20 min to obtain an orange-yellow precursor solution. Slowly add hydrogen peroxide dropwise to the precursor solution until the solution turns pale yellow and no bubbles are generated. Stop adding hydrogen peroxide and turn off the heating device. After cooling to room temperature, filter to remove insoluble impurities. Transfer the filtrate to a dialysis bag with a molecular weight cutoff of 500 Da and dialyze with 1000 mL of deionized water for 36 h (replace the dialysate every 8 h). Concentrate the dialyzed solution by rotary evaporation and dry it in an oven at 60 °C to obtain pale yellow nitrogen-doped sulfur quantum dot (N-SQDs) powder, which is then sealed and stored.

[0044] Example 2: Preparation of polyepoxysuccinic acid modified sulfur quantum dots (PESA-SQDs) Step 1: Pretreatment of Polyepoxysuccinic Acid (PESA) Polyepoxysuccinate sodium (PESA-Na) was weighed and dissolved in distilled water. Concentrated hydrochloric acid (HCl) was added dropwise to adjust the pH to 2. Three times the volume of anhydrous ethanol was added and allowed to stand. After a white solid precipitated, it was washed, dried and ground to obtain polyepoxysuccinic acid (PESA).

[0045] Step 2: Composite reaction of polyepoxysuccinic acid modified sulfur quantum dots (PESA-SQDs) Pretreated polyepoxysuccinic acid (PESA) and nitrogen-doped sulfur quantum dots (N-SQDs) prepared in Example 1 were dissolved in distilled water at a mass ratio of 10:1. The pH was adjusted to 7-8 by adding an appropriate amount of 1 mol / L sodium hydroxide (NaOH) solution, and the mixture was stirred and heated at 80°C for 24 h. After cooling to room temperature, the mixture was filtered under reduced pressure through a 0.22 μm filter membrane. Three volumes of anhydrous ethanol were added to the filtrate, and the mixture was allowed to stand for 12 h to precipitate. The precipitate was washed 3-4 times with anhydrous ethanol, concentrated by rotary evaporation, and dried in an oven at 60°C to obtain white powdered polyepoxysuccinic acid modified sulfur quantum dots (PESA-SQDs).

[0046] Example 3: Preparation of thiourea-modified polyepoxysuccinic acid-modified sulfur quantum dots (CSN-PESA-SQDs) and urea-modified polyepoxysuccinic acid-modified sulfur quantum dots (UERA-PESA-SQDs). Step 1: Preparation of thiourea-modified polyepoxysuccinic acid (CSN-PESA) and urea-modified polyepoxysuccinic acid (UERA-PESA) Polyepoxysuccinic acid (PESA) and thiourea (CSN) were dissolved in distilled water at a mass ratio of 2:1. The pH was adjusted to 7 by adding an appropriate amount of 1 mol / L sodium hydroxide (NaOH) solution. The mixture was stirred at 85°C for 1.5 h until the system became viscous. The reaction product was filtered to remove impurities and then dried under vacuum to obtain thiourea-modified polyepoxysuccinic acid (CSN-PESA).

[0047] Polyepoxysuccinic acid (PESA) and urea (UERA) were dissolved in distilled water at a mass ratio of 2.5:1. An appropriate amount of 1 mol / L sodium hydroxide (NaOH) solution was added to adjust the pH to 7. The mixture was stirred at 85°C for 1.5 h until the system became viscous. The reaction product was filtered to remove impurities and then dried under vacuum to obtain urea-modified polyepoxysuccinic acid (UERA-PESA).

[0048] Step 2: Composite reaction of thiourea-modified polyepoxysuccinic acid-modified sulfur quantum dots (CSN-PESA-SQDs) and urea-modified polyepoxysuccinic acid-modified sulfur quantum dots (UERA-PESA-SQDs). Nitrogen-doped sulfur quantum dots (N-SQDs) prepared in Example 1, thiourea-modified polyepoxysuccinic acid (CSN-PESA), and urea-modified polyepoxysuccinic acid (UERA-PESA) were weighed separately and dissolved in 20 mL of deionized water at a mass ratio of 15:1. The pH was adjusted to 7 by adding an appropriate amount of 1 mol / L sodium hydroxide (NaOH) solution. The mixed solution was heated at 80 °C for 24 h, cooled to room temperature, poured into a watch glass, and precipitated with 3 times its volume of anhydrous ethanol for 12 h. The precipitate was washed with anhydrous ethanol. After being precipitated 3-4 times and concentrated by rotary evaporation, the product was dried in an oven at 60°C to obtain two white powder products, namely thiourea-modified polyepoxysuccinic acid-modified sulfur quantum dots (CSN-PESA-SQDs) and urea-modified polyepoxysuccinic acid-modified sulfur quantum dots (UERA-PESA-SQDs).

[0049] Example 4: Product purification and finished product preparation The polyepoxysuccinic acid modified sulfur quantum dots (PESA-SQDs), thiourea modified polyepoxysuccinic acid modified sulfur quantum dots (CSN-PESA-SQDs), and urea modified polyepoxysuccinic acid modified sulfur quantum dots (UERA-PESA-SQDs) prepared in Examples 2 and 3 were filtered through 0.22 μm microporous membranes to remove particulate impurities. They were then transferred to dialysis bags with a molecular weight cutoff of 500 Da and dialyzed with deionized water for 36 h to further remove small molecule inorganic salts, obtaining purified composite products.

[0050] The purified product was placed in a rotary evaporator and concentrated to a viscous state at 60-70℃; then transferred to a vacuum drying oven and dried at 60℃ for 4 hours. After grinding, powdered polyepoxysuccinic acid and its derivatives modified sulfur quantum dot scale inhibitor and antibacterial agent was obtained.

[0051] Example 5: Transmission Electron Microscopy (TEM) Characterization The polyepoxysuccinic acid and its derivatives modified sulfur quantum dot scale inhibitors and antibacterial agents obtained in Examples 2 and 3 were characterized using transmission electron microscopy (TEM).

[0052] like Figure 2As shown, the modified sulfur quantum dots (PESA-SQDs), thiourea-modified PSA-SQDs (CSN-PESA-SQDs), and urea-modified PSA-SQDs (UERA-PESA-SQDs) exhibit uniform distribution, predominantly spherical morphology, good dispersibility, and no agglomeration. Their sizes range from 3.5-4.2 nm, 3.7-4.5 nm, and 3.6-4.1 nm, respectively, with average particle sizes of 3.87 nm, 4.11 nm, and 3.95 nm. The lattice spacings in PESA-SQDs, CSN-PESA-SQDs, and UERA-PESA-SQDs are clearly observed to be approximately 0.24 nm, 0.23 nm, and 0.235 nm, respectively, demonstrating good crystallinity.

[0053] Example 6: Fourier Transform Infrared Spectroscopy (FT-IR) Characterization The samples obtained in Examples 1, 2 and 3 were characterized using Fourier transform infrared spectroscopy.

[0054] like Figure 3 As shown, the sulfur quantum dots PESA-SQDs, CSN-PESA-SQDs, and UERA-PESA-SQDs modified with polyepoxysuccinic acid and its derivatives retained the original characteristic peaks of N-SQDs on their surfaces, in the range of 3100-3500 cm⁻¹. -1 1700-1600cm -1 1300-1400cm -1 1000-1200cm -1 New characteristic peaks for NH, C=O, CN, and COC appear at this location. These peaks are particularly prominent in the 1700-1600 cm⁻¹ region. -1 The absorption peaks at 1300-1400 cm⁻¹ are mainly attributed to the stretching vibrations of C=O in -COOH and -CONH⁻. -1 The absorption peak at 1000-1200 cm⁻¹ is mainly attributed to the CN stretching vibration peak in the amide group. -1 The intensity of the vibration at this point is attributed to the stretching vibration of COC, and its intensity is significantly higher in the modified sample than in the unmodified N-SQDs. Furthermore, CSN-PESA-SQDs exhibit a higher intensity at 1250 cm⁻¹. -1 The presence of a C=S characteristic peak nearby indicates that the modification of polyepoxysuccinic acid and its derivatives effectively increased the surface functional group density and introduced new active groups.

[0055] Example 7: Static Scale Inhibition Performance Test This embodiment tests the static scale inhibition performance of the scale inhibitors and antibacterial agents prepared in Examples 2 and 3.

[0056] The test method referenced the petroleum and natural gas industry standard "General Technical Conditions for Scale Inhibitors for Oilfield Use" (SY-T5673-2020), and static scale inhibition experiments were conducted using production water samples from the WZ12-2A oilfield in the western South China Sea. The Na content in this water sample... + +K + The content is 11403 mg / L, Ca² + 700 mg / L, Mg² + It is 208 mg / L, Cl - The concentration of HCO3 was 20111 mg / L. - The concentration was 547 mg / L, SO4² - The concentration was 281 mg / L. The suspended solids (SS) was 2 mg / L, the particle size (d) was only 1.5 μm, and the dissolved oxygen (O) content was 6 mg / L.

[0057] Adding scale inhibitors can suppress the formation of scale in water, reducing the amount of calcium carbonate precipitate and resulting in a higher concentration of free calcium ions compared to water without scale inhibitors. The scale inhibition rate can be calculated by analyzing the changes in the mass of calcium scale in blank water samples before and after the experiment, as well as in water samples after adding scale inhibitors.

[0058] The scale inhibition rate is calculated using the following formula: Total scale C = M1 + M2; (Equation 1) Scale inhibition rate η = (C0 - C1) / C0 × 100%; (Equation 2) In the formula, M1 represents the mass of scale retained on the filter membrane (g), M2 represents the mass of scale adhering to the inner wall of the reaction vessel (g), η represents the scale inhibition rate (%), C0 represents the scale amount in the control group (g), and C1 represents the scale amount in the chemically treated group (g). Based on previous research, over 98% of the scale in the production water of the WZ12-2A oilfield is CaCO3 scale; therefore, the η value in this paper can be considered as the scale inhibition rate for CaCO3.

[0059] The scale inhibitors prepared in Examples 2 and 3 were added to the production water samples at concentrations of 10, 20, 30, 40, and 50 mg / L, respectively.

[0060] like Figure 4 As shown, the scale inhibition rates of PESA-SQDs, CSN-PESA-SQDs, and UERA-PESA-SQDs all increased with increasing dosage. The results indicate that the scale inhibitors and antibacterial agents prepared in this application can achieve excellent scale inhibition effects even at low dosages, with UERA-PESA-SQDs exhibiting the best performance.

[0061] Example 8: Dynamic scale inhibition performance test (core displacement experiment) This embodiment tests the dynamic scale inhibition performance of the scale inhibitors and antibacterial agents prepared in Examples 2 and 3.

[0062] The testing method was based on the oil and gas industry standard SY / T5358-2024 "Evaluation Method of Reservoir Sensitivity Flow Test". Core flow experiments were carried out, and the displacement fluid was the WZ12-2A oilfield production water sample from Example 7.

[0063] The formula for calculating the core permeability retention rate D is: D=(K i / K0)×100%; In the formula, K0 is the initial permeability of the working fluid (10 - ³μm²), K i The permeability measured at different PV values ​​(10) - (³μm²).

[0064] The scale inhibitors prepared in Examples 2 and 3 were added to the displacing fluid at different concentrations, and core displacement experiments were conducted. The experiment was stopped when the cumulative displacement volume reached 100 PV. The pressure difference changes during the displacement process were recorded, and the core permeability retention rate was calculated. Figure 5 Comparison of core permeability retention rates of polyepoxysuccinic acid and its derivatives modified sulfur quantum dot scale inhibitors.

[0065] As the concentration increased, the core permeability retention rate further improved, indicating that the scale inhibitor and antibacterial agent prepared in this application has good reservoir compatibility.

[0066] Example 9: Antibacterial Performance Test This embodiment tests the antibacterial properties of CSN-PESA-SQDs prepared in Example 3.

[0067] The test method employed the EASICULTCOMBI dip-slide method to conduct antibacterial experiments. Natural water samples simulating the microbial environment of oilfield water were used as the test subjects. These water samples contained common bacteria, with an initial colony count of approximately 10. 4 CFU / mL. Experimental groups and a blank control group were set up with CSN-PESA-SQDs concentrations of 50, 100, 125, 150, and 180 mg / L, with two parallel samples in each group.

[0068] Specific testing procedures: Immerse the EASICULTCOMBI slides (containing both TTC agar and rose red sodium agar) into the water samples of each concentration experimental group and the blank control group, ensuring the slides are completely wetted and in full contact with the water samples for 5-10 seconds. After removal, blot off excess liquid and seal the slides in culture tubes. Incubate the culture tubes in a constant temperature incubator at 27-30℃ for 24-48 hours. After incubation, compare the colony growth of the blank group and the experimental group, count the colony count, and evaluate the antibacterial effect.

[0069] like Figure 6 As shown, the blank control group had dense bacterial colonies on the surface of TTC agar, with a colony count of up to 10. 4 CFU / mL; A certain number of colonies were still visible on TTC agar in the 50 mg / L and 100 mg / L experimental groups, indicating limited antibacterial effect; the number of colonies in the 125 mg / L experimental group was significantly reduced, with an antibacterial rate of over 85%; the 150 mg / L experimental group had only a very small number of micro-colony residues, achieving highly effective antibacterial effect; the 180 mg / L experimental group showed no colony growth on the surface of TTC agar, achieving complete antibacterial effect. No mold or yeast growth was observed on any of the rose red sodium agar concentration groups.

[0070] The above results indicate that the CSN-PESA-SQDs scale inhibitor and antibacterial agent prepared in this application has a significant concentration-dependent antibacterial effect on common bacteria in water. Highly effective antibacterial effect can be achieved at concentrations of 125 mg / L and above, and bacterial growth can be completely inhibited at a concentration of 180 mg / L.

[0071] Example 10: Comparative Experiment This embodiment compares the scale inhibitor and antibacterial agent prepared in this application with the prior art.

[0072] According to HengtongXia et al. in 2024 The paper "Research on the inhibitory properties and mechanism of carboxymethylcellulose-modified sulfur quantum dots towards calcium sulfate and calcium carbonate" published in the International Journal of Biological Macromolecules (Int. J. Biol. Macromol., 2024, 262, 130106) reports that the carboxymethylcellulose-modified sulfur quantum dot (CMC-SQDs) scale inhibitor prepared therein can only achieve a weak inhibitory effect on calcium carbonate at a temperature of 80℃ and a dosage of 60 mg / L.

[0073] The scale inhibitors and antibacterial agents prepared in Examples 2 and 3 of this application, under the same temperature (80°C) and a dosage of only 20 mg / L (one-third of the former), showed a scale inhibition rate of up to 90.8% for calcium carbonate, far superior to the weak inhibition effect of CMC-SQDs. Simultaneously, the products of this application can disrupt the regular growth of calcium carbonate crystals through a triple mechanism of chelation, crystal form regulation, and adsorption dispersion, achieving a core permeability retention rate of 81.7% and a core damage rate of only 18.3%. Furthermore, CSN-PESA-SQDs can achieve complete antibacterial activity at a concentration of 180 mg / L, possessing the dual advantages of scale inhibition and antibacterial function.

[0074] Comparative results show that the polyepoxysuccinic acid and its derivatives modified sulfur quantum dot scale inhibitor and antibacterial agent prepared in this application is significantly superior to the CMC-SQDs scale inhibitor reported in the prior art in terms of dosage, scale inhibition efficiency, core compatibility and functional diversity.

[0075] The method for preparing the polyepoxysuccinic acid modified sulfur quantum dot scale inhibitor and antibacterial agent provided in this application is simple, mild, and environmentally friendly. The resulting product has both excellent scale inhibition and antibacterial properties and can be widely used in the field of oilfield produced water treatment. It effectively breaks the vicious cycle of "scale formation-bacterial growth-corrosion" in oilfields and has significant industrial and economic value.

[0076] In summary, compared with the prior art, the preferred preparation method of this application (such as using a mass ratio of (8-12):1 for composite reaction, or further modification with thiourea or urea, etc.) can further achieve the following technical effects: 1. Green and efficient preparation process: The solvent-free composite modification process is adopted, the raw materials are environmentally friendly and readily available, the reaction conditions are mild (temperature ≤90℃), the time is short and the energy consumption is low, avoiding the pollution problems in the synthesis process of traditional chemical scale inhibitors, which meets the requirements of green development.

[0077] 2. Strong functional synergy: Breaking through the limitations of traditional scale inhibitors with only one function, it achieves synergistic effects of scale inhibition and antibacterial activity through precise modification of surface functional groups. The scale inhibition rate can reach 85.9%-90.8% at a dosage of 20 mg / L, and complete antibacterial activity can be achieved at a concentration of 180 mg / L, which can simultaneously solve the problems of scaling and bacterial growth in oil fields.

[0078] 3. Wide adaptability and good reservoir compatibility: It is suitable for oilfields with high salinity and high temperature, and has a significant effect on inhibiting calcium carbonate scale. Core flow experiments show that the permeability retention rate is over 80.9% at a dosage of 20 mg / L, and the core damage rate is ≤19.1%, which meets the requirements for water injection in oilfields.

[0079] 4. Clear mechanism of action: It inhibits scaling through a triple mechanism of chelation solubilization, crystal form regulation and adsorption dispersion, while relying on the bulk properties of sulfur quantum dots and the synergistic effect of functional groups to achieve antibacterial effect, providing a clear structure-activity relationship reference for the structural design of multifunctional water treatment agents.

[0080] The various embodiments in this specification are described in a progressive manner. For the same or similar parts between the various embodiments, please refer to each other. Each embodiment focuses on describing the differences from other embodiments.

[0081] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit this application. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of this application.

Claims

1. A method for preparing a polyepoxysuccinic acid modified sulfur quantum dot scale and bacteria inhibitor, characterized in that, include: S1: Preparation of nitrogen-doped sulfur quantum dots; S2: Polyepoxysuccinic acid or its derivatives are combined with the nitrogen-doped sulfur quantum dots to obtain a composite product; S3: Purify the composite product; S4: The purified composite product is concentrated, dried and ground to obtain the scale inhibitor and antibacterial agent.

2. The preparation method according to claim 1, characterized in that, Step S2 includes: S21: Polyepoxysuccinate is pretreated by acidification to obtain polyepoxysuccinic acid; S22: The polyepoxysuccinic acid obtained in step S21 is combined with the nitrogen-doped sulfur quantum dots prepared in step S1 at a mass ratio of (8-12):1 to obtain polyepoxysuccinic acid modified sulfur quantum dots.

3. The preparation method according to claim 2, characterized in that, Step S21 includes: Sodium polyepoxysuccinate was weighed and dissolved in distilled water. Concentrated hydrochloric acid was added dropwise to adjust the pH to 2. Anhydrous ethanol was added and allowed to stand to precipitate a white solid. After washing, drying and grinding, polyepoxysuccinic acid was obtained. Step S22 includes: The prepared polyepoxysuccinic acid and nitrogen-doped sulfur quantum dots were dissolved in distilled water at a mass ratio of 10:

1. The pH was adjusted to 7-8 with sodium hydroxide solution, and the mixture was stirred and heated at 80℃ for 24 hours. After cooling, the mixture was filtered through a filter membrane. Anhydrous ethanol was added to the filtrate and allowed to stand to precipitate. After washing, the precipitate was concentrated by rotary evaporation and dried to obtain polyepoxysuccinic acid modified sulfur quantum dots.

4. The preparation method according to claim 1, characterized in that, Step S2 also includes the preparation of a derivative of polyepoxysuccinic acid: S23: Polyepoxysuccinic acid is modified by reacting it with thiourea or urea to obtain thiourea-modified polyepoxysuccinic acid or urea-modified polyepoxysuccinic acid respectively. S24: The thiourea-modified polyepoxysuccinic acid or urea-modified polyepoxysuccinic acid obtained in step S23 is reacted with the nitrogen-doped sulfur quantum dots obtained in step S1 to obtain thiourea-modified polyepoxysuccinic acid-modified sulfur quantum dots or urea-modified polyepoxysuccinic acid-modified sulfur quantum dots.

5. The preparation method according to claim 4, characterized in that, Step S23 includes: Polyepoxysuccinic acid was dissolved in distilled water with thiourea or urea at a mass ratio of (2-3):

1. The pH was adjusted to 7 with sodium hydroxide solution. The mixture was stirred at 85°C for 1.5 h until it became viscous. After filtration to remove impurities, it was dried under vacuum to obtain thiourea-modified polyepoxysuccinic acid or urea-modified polyepoxysuccinic acid. Step S24 includes: The nitrogen-doped sulfur quantum dots obtained in step S1 and the thiourea-modified polyepoxysuccinic acid or urea-modified polyepoxysuccinic acid obtained in step S23 were dissolved in deionized water at a mass ratio of (10-15):

1. The pH was adjusted to 7 with sodium hydroxide solution, heated at 80°C for 24 hours, cooled, and then anhydrous ethanol was added to allow precipitation. After washing, the mixture was concentrated by rotary evaporation and dried at 60°C to obtain thiourea-modified polyepoxysuccinic acid-modified sulfur quantum dots or urea-modified polyepoxysuccinic acid-modified sulfur quantum dots.

6. The preparation method according to claim 1, characterized in that, In step S1, the raw materials for preparing nitrogen-doped sulfur quantum dots include sublimed sulfur, sodium hydroxide, and L-cysteine; In step S2, the conditions for the composite reaction include: pH adjusted to 7-8, reaction temperature at 80-90℃, and reaction time at 1.5-24h.

7. The preparation method according to claim 1, characterized in that, In step S3, the purification process includes at least one of microporous membrane filtration and dialysis; In step S4, the drying method is vacuum drying.

8. The preparation method according to claim 1, characterized in that, The nitrogen-doped sulfur quantum dots, the polyepoxysuccinic acid, and the derivatives of the polyepoxysuccinic acid are in powder or solution form before the reaction.

9. A polyepoxysuccinic acid and its derivatives modified sulfur quantum dot scale inhibitor and antibacterial agent prepared by the preparation method according to any one of claims 1-8.

10. The scale inhibitor and antibacterial agent according to claim 9, characterized in that, The scale inhibitor and antibacterial agent has a surface rich in one or more functional groups, including carboxyl, amide, carbonyl and thiocarbonyl groups; and / or its particle size is 3.5-4.5 nm.

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