Preparation method of scale inhibitor for water pollution prevention and control

Abstract

The application discloses a preparation method of a scale inhibitor for water pollution prevention and treatment, and belongs to the technical field of scale inhibitors. Natural diatomite is sieved and modified by using a KH-550 silane coupling agent to prepare modified diatomite. DIC and NHS are used as carboxyl activators, and DMPA is used as an alkaline catalyst to convert PLGA into an ester intermediate, and then the ester intermediate is subjected to amidation reaction with glucosamine to obtain modified PLGA copolymer. The modified PLGA copolymer is immersed in the modified diatomite to obtain a supported modified PLGA powder. The supported modified PLGA powder is coated in a chitosan shell layer doped with ethylenediamine modified graphene oxide through electrostatic self-assembly to obtain PLGA microcapsules. The PLGA microcapsules, deionized water, dodecyl glucoside and polyethylene glycol are stirred and mixed to obtain the scale inhibitor for water pollution prevention and treatment. The scale inhibitor has the performances of stable release, good overall dispersibility and efficient synergistic scale inhibition.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of scale inhibitors, and particularly relates to a preparation method of a scale inhibitor for water pollution prevention and treatment. BACKGROUND

[0002] High-salinity wastewater in chemical, pharmaceutical, printing and dyeing industries contains high-concentration salt and complex pollutants. Direct discharge will seriously harm the water environment and destroy the water ecology. The evaporation concentration system is an important technology for treating such wastewater, but its operation is often restricted by the problem of scaling. Calcium and magnesium ions and scale-forming substances such as sulfate and carbonate in high-salinity wastewater can form hard scale on the surface of equipment such as evaporator heating pipes, resulting in a significant decrease in heat exchange efficiency. As a special chemical agent for inhibiting the crystallization and deposition of scale-forming substances in water, the scale inhibitor can effectively prevent the formation of hard scale layers such as calcium and magnesium salts by mechanisms such as chelating scale-forming ions, interfering with crystal growth or dispersing fine particles.

[0003] A Chinese patent application with the publication number CN119191585A discloses a high-salinity scale inhibitor suitable for high-salinity wastewater multi-evaporation conditions and a use method thereof. The scale inhibitor is composed of polyaspartic acid 15%, polyepoxy succinic acid 18%, hydroxyethylidene diphosphonic acid 20%, polymaleic anhydride 8%, composite quaternary ammonium salt 12%, 2-phospho-1,2,4-tricarboxylic acid butane 5%, pH adjuster 3%, sodium persulfate 5%, rust inhibitor 8% and preservative 6%. When used, the high-salinity wastewater is pretreated to remove part of the hardness and impurities, and then the mixed scale inhibitor is added in proportion and uniformly dispersed in the wastewater. The scale inhibition performance of the present application is excellent, which can alleviate the aggregation and deposition of salt on the equipment wall, thereby prolonging the service life of the equipment.

[0004] When the high-salinity wastewater system is in a high-temperature environment, the solubility of scale-forming substances changes, and calcium and magnesium ions and acid ions are more likely to be supersaturated, and the crystallization rate increases. However, at high temperatures, organic scale inhibitors may undergo thermal degradation, resulting in a decrease in scale inhibition effect and an inability to effectively alleviate the crystallization and deposition of calcium, magnesium ions and other substances on the surface of the equipment, leading to an aggravation of the scaling problem. Therefore, the stability of the scale inhibitor under high-temperature application has become a research focus. SUMMARY

[0005] The purpose of the present application is to provide a preparation method of a scale inhibitor for water pollution prevention and treatment. By PLGA coating modification, PLGA microcapsules with good slow release and high-temperature stability are prepared, solving the problem of easy thermal degradation of organic scale inhibitors in high-temperature high-salinity wastewater systems. At the same time, combined with the dispersing effect of dodecyl glucoside, the dispersing stability of the scale inhibitor in the high-salinity wastewater system is improved.

[0006] The purpose of the present application can be achieved by the following technical solutions:

[0007] The application discloses a preparation method of a scale inhibitor for water pollution prevention and treatment.

[0008] Step one: natural diatomite is sieved and modified by a KH-550 silane coupling agent to obtain modified diatomite;

[0009] Step two: PLGA is converted into an ester intermediate by using DIC and NHS as a carboxyl activator and using DMPA as an alkaline catalyst, and then subjected to amidation reaction with glucosamine to obtain modified PLGA copolymer; and the modified PLGA copolymer is immersed in the modified diatomite to obtain a supported modified PLGA powder;

[0010] Step three: the supported modified PLGA powder is coated in a chitosan shell layer doped with ethylenediamine modified graphene oxide by electrostatic self-assembly to obtain a PLGA microcapsule;

[0011] Step four: the PLGA microcapsule, deionized water, dodecyl glucoside and polyethylene glycol are stirred and mixed to obtain the scale inhibitor for water pollution prevention and treatment.

[0012] Further, the specific preparation process of the modified diatomite is as follows:

[0013] After the natural diatomite is dried at 70-90 DEG C, the diatomite is ground to pass through a 300-mesh sieve, and a concentrated sulfuric acid solution with a concentration of 30wt% is added into a reaction kettle to soak for 20-30h, and then the diatomite is subjected to water bath reaction at 70-90 DEG C for 40-60min; after cooling, the diatomite is extracted and washed to be neutral, and then the diatomite is dried at 80-100 DEG C, ground to pass through a 300-mesh sieve and sealed for storage, so that the acid treatment of the diatomite is completed; the diatomite after the acid treatment and deionized water are added into a reaction kettle, and under the conditions of 70-90 DEG C and stirring, a silane coupling agent KH-550 and ethanol are added, and the reaction is stirred at 800-1000rpm for 1-3h; after filtration, the filter cake is dried to constant weight, so that the modified diatomite is obtained.

[0014] Further, the ratio of the amount of the natural diatomite to the amount of sulfuric acid is 60-80g:100-200mL.

[0015] Further, the mass ratio of the diatomite after the acid treatment, deionized water, the silane coupling agent and ethanol is 20-30:90-110:0.5-1.5:8-12.

[0016] Further, the specific preparation process of the modified PLGA copolymer is as follows:

[0017] PLGA and dichloromethane are added to a stirred tank, stirred at 0-5℃ until completely dissolved, N-hydroxysuccinimide, 4-dimethylaminopyridine and N,N-diisopropylcarbodiimide are added in turn, 25-35℃ reaction for 10-12h, form the ester intermediate, the amino glucosamine is dissolved in DMF and added to the reaction kettle, continue to react for 18-24h, the reaction system is washed with 5wt% sodium bicarbonate solution and deionized water in turn, dried with anhydrous sodium sulfate, filtered, and the solvent is removed under reduced pressure, the obtained crude product is precipitated with ice ethyl ether, the lower layer is vacuum dried to obtain the modified PLGA copolymer.

[0018] Further, the amount ratio of PLGA, dichloromethane, N-hydroxysuccinimide, 4-dimethylaminopyridine, N,N-diisopropylcarbodiimide, glucosamine and DMF is 2-4g:0.1-0.2L:30-50mg:6-8mg:60-80μL:0.5-0.6g:20-30mL.

[0019] Further, the specific preparation process of the supported modified PLGA powder is as follows:

[0020] The modified PLGA copolymer is dissolved in a dichloromethane / ethanol mixed solution, the pH value is adjusted to 5.0-6.0 with 0.1M hydrochloric acid, modified diatomite is added, ultrasonic dispersion is carried out at 25-30℃ and 300-500W for 20-30min, then stirring is carried out at a speed of 200-300rpm for 8-12h, the solvent is removed by reduced pressure concentration, the remaining solid is washed with deionized water for 3-4 times, and dried to constant weight to obtain the supported modified PLGA powder.

[0021] Further, the amount ratio of the modified PLGA copolymer, dichloromethane / ethanol and modified diatomite is 2-4g:200-400mL:10-20g.

[0022] Further, the specific preparation process of the PLGA microcapsule is as follows:

[0023] The supported modified PLGA powder, EDA-GO and 0.4wt% chitosan acetic acid solution are added to a reaction kettle, stirred at 30-40℃ for 2-3h, centrifugal filtration is carried out, the filter cake is washed with deionized water for 3-4 times, and dried to constant weight to obtain the PLGA microcapsule.

[0024] Further, the mass ratio of the supported modified PLGA powder, EDA-GO and 0.4wt% chitosan acetic acid solution is 5-8:0.05-0.12:0.4-0.8.

[0025] Further, the specific preparation process of the EDA-GO is as follows:

[0026] The GO and deionized water are added into a reaction kettle, ultrasonic dispersion is carried out for 1-3h, ethylenediamine is added at a rotation speed of 200-300rpm, reaction is carried out at 40-50 DEG C for 6-8h, a coagulant sodium chloride is added, centrifugation is carried out at 800-1000rpm for 20-30min, the supernatant is discarded, the lower solid is washed with ethanol and deionized water for 2-3 times respectively, and drying is carried out until the constant weight, so that EDA-GO is obtained.

[0027] Further, the mass ratio of GO, deionized water, ethylenediamine and sodium chloride is 5-10:800-1000:5-8:5-10.

[0028] Further, the specific preparation method of the scale inhibitor for water pollution prevention and control is as follows:

[0029] The PLGA microcapsule and deionized water are added into a stirring kettle, heated to 40-60 DEG C, dodecyl glucoside and polyethylene glycol are added, stirring is carried out for 20-30min, and natural cooling is carried out to room temperature, so that the scale inhibitor for water pollution prevention and control is obtained.

[0030] Further, the mass ratio of PLGA microcapsule, deionized water, dodecyl glucoside and polyethylene glycol is 30-50:20-40:10-13:5-8.

[0031] The beneficial effects of the application are as follows:

[0032] 1. In the application, the glucosamine modification makes the PLGA combine more closely with the modified diatomite, reduces the rapid separation of the active ingredients, the PLGA microcapsule formed by EDA-GO and chitosan constitutes a physical barrier, delays the diffusion of the active ingredients, the compactness and pore regulation of the overall structure make the active ingredients release gradually, avoid the waste caused by too fast release, and realize the stable release rate.

[0033] 2. In the application, the chitosan constructs a protective barrier by virtue of excellent film-forming property, reduces the direct exposure of the internal organic scale-inhibiting component at high temperature, the modified diatomite optimizes the pore after acid treatment and introduces organic groups through KH-550, and is compatible with the modified PLGA, as a carrier, can reduce the damage of high temperature to the PLGA molecular chain, and can enhance the structural stability of the system in a high-salt environment, the EDA-GO is modified from GO by ethylenediamine, the surface amino group improves the dispersity, the excellent thermal stability of EDA-GO itself and the combination of PLGA and chitosan through hydrogen bond improve the heat resistance of the composite system, reduce the PLGA molecular chain breakage caused by high temperature, and solve the problem that the organic scale inhibitor is easily thermally degraded in a high-temperature and high-salt wastewater system. Since the graphene itself has a two-dimensional sheet-like structure of nanometer scale, the doping of EDA-GO has a viscosity-reducing and lubricating effect, can reduce the friction coefficient of the PLGA microcapsule and the inner wall of the high-salt wastewater system, and thus effectively reduces the possibility of causing the blockage of the evaporative crystallizer.

[0034] 3. The chitosan introduced in the application has a natural polysaccharide structure, and the natural sugar groups introduced by the glucosamine modified PLGA also belong to degradable components. They can induce microorganisms to secrete corresponding enzymes to decompose the materials to obtain nutrition, thereby promoting the gradual degradation of the materials, and ultimately achieving a high biodegradation rate.

[0035] 4. In the application, after the PLGA is modified by glucosamine, a large number of amino and hydroxyl groups are introduced into the molecular chain. These polar groups can combine with Ca 2+ , CO3 2- , SO4 2- , PO4 3- ions in water through coordination bonds, hinder the crystal from agglomerating and growing, and the modified diatomite retains the porous structure and improves the compatibility with other components. The introduced EDA-GO has a large specific surface area, and the amino groups on its surface can be closely combined with PLGA and chitosan. The addition of chitosan forms a physical barrier of microcapsules, which can hinder the rapid diffusion of components; in addition, dodecyl glucoside as a surfactant can improve the dispersibility of the material in water, ensure uniform contact of each scale inhibition component, and ultimately achieve high-efficiency synergistic scale inhibition of CaCO3, CaSO4 and CaPO4. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the embodiments of the application. Obviously, the described embodiments are only a part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the application.

[0037] Embodiment 1: The application provides a preparation method of a scale inhibitor for water pollution prevention and control, comprising the following steps:

[0038] S1: 80g of natural diatomite is dried at 70℃, ground and passed through a 300 mesh sieve, and then added into a reaction kettle with 100mL of a 30wt% sulfuric acid solution, soaked for 20h, reacted in a 70℃ water bath for 40min, and then filtered, washed to neutral, dried at 80℃, ground again to pass through a 300 mesh sieve and sealed for storage, to complete the acid treatment of the diatomite; 30g of the acid-treated diatomite and 100g of deionized water are added into a reaction kettle, 1g of a silane coupling agent KH-550 and 8g of ethanol are added under the condition of 70℃ and stirring, and the mixture is stirred at 800rpm for 1h, then filtered and dried to constant weight, to obtain modified diatomite;

[0039] The impurities are removed and the pore structure of diatomite is optimized by mechanical screening and acid leaching process, and the silanol group is generated by hydrolysis of KH-550 silane coupling agent in an aqueous system, and is condensed with the silicon hydroxyl group on the surface of diatomite to form Si-O-Si covalent bond, so that the grafting of amino functional groups is realized, and modified diatomite is obtained.

[0040] S2: 20 g of polylactic acid-glycolic acid copolymer (PLGA) (molecular weight 5000) and 1 L of dichloromethane were added to a stirred tank, stirred at 0°C until completely dissolved, 500 mg of N-hydroxysuccinimide (NHS), 80 mg of 4-dimethylaminopyridine (DMAP) and 800 μL of N,N-dimethylformamide (DMF) were added in turn, and reacted at 25°C for 10 h, 5 g of glucosamine dissolved in N,N-dimethylformamide (DMF) was added to the reaction tank, and the reaction was continued for 18 h, the reaction system was washed with 5 wt% sodium bicarbonate solution and deionized water in turn, and then dried with anhydrous sodium sulfate, filtered, and the solvent was removed under reduced pressure, the obtained crude product was precipitated with ice-ether, the lower layer was taken out and dried under vacuum, and the modified PLGA copolymer was obtained.

[0041] S3: 10 g of modified PLGA copolymer was dissolved in 1 L of dichloromethane / ethanol (volume ratio 7:3) solution, the pH value was adjusted to 5.0 with 0.1 M hydrochloric acid, 40 g of modified diatomite was added, and ultrasonic dispersion was carried out at 25°C and 300 for 20 min, then stirring was carried out at 200 rpm for 8 h, the solvent was removed by reduced pressure concentration, the remaining solid was washed with deionized water for 3 times, and dried to constant weight to obtain a supported modified PLGA powder;

[0042] The modified PLGA copolymer was dissolved in a dichloromethane / ethanol system, the pH value of the system was adjusted to protonate the amino group, and electrostatic adsorption was formed with the silicon oxygen negative ions on the surface of diatomite, and the modified PLGA copolymer was loaded in and outside the pores of diatomite during the impregnation process, forming a supported modified PLGA powder.

[0043] S4: 5 g of graphene oxide (GO) and 800 g of deionized water were added to a reaction tank, ultrasonic dispersion was carried out for 1 h, 5 g of ethylenediamine (EDA) was added at a stirring speed of 200 rpm, and the reaction was carried out at 40°C for 6 h, then 5 g of coagulant sodium chloride was added, and centrifugation was carried out at 800 rpm for 20 min, the supernatant was discarded, and the lower solid was washed with ethanol and deionized water for 2 times respectively, and dried to constant weight to obtain EDA-GO.

[0044] 5 g of supported modified PLGA powder, 0.07 g of EDA-GO and 0.4 g of chitosan acetic acid solution with a concentration of 0.4 wt% were added to a reaction tank, stirring was carried out at 30°C for 2 h, centrifugal filtration was carried out, the filter cake was washed with deionized water for 3 times, and dried to constant weight to obtain PLGA microcapsules.

[0045] The modified PLGA powder loaded into the chitosan acetic acid solution containing ethylenediamine modified graphene oxide with a concentration of 0.4wt%, the -NH3 + The carboxyl / siloxane negative ions on the surface of the copolymer form electrostatic adsorption, and the hydroxyl / amino groups of the EDA-GO synergistically enhance the interfacial bonding with the hydroxyl groups of the chitosan through hydrogen bonding. Through electrostatic self-assembly, a chitosan shell layer doped with EDA-GO is finally formed on the surface of the copolymer, and a PLGA microcapsule is obtained.

[0046] S5: 3g of PLGA microcapsules and 4g of deionized water are added to a stirred tank, heated to 40℃, 1g of dodecyl glucoside and 5g of polyethylene glycol are added, stirred for 20min, and naturally cooled to room temperature to obtain a scale inhibitor for water pollution prevention and control.

[0047] Embodiment 2: The present embodiment provides a preparation method of a scale inhibitor for water pollution prevention and control, comprising the following steps:

[0048] S1: After drying at 80℃, 60g of natural diatomite is ground to pass through a 300 mesh sieve, and 150mL of a 30wt% sulfuric acid solution is added to a reaction kettle, soaked for 25h, and reacted at 80℃ water bath for 50min. After cooling, it is filtered, washed to neutral, dried at 90℃, ground to pass through a 300 mesh sieve again, and sealed for storage to complete the acid treatment of diatomite; 20g of acid-treated diatomite and 90g of deionized water are added to a reaction kettle, and under the conditions of 80℃ and stirring, 0.5g of silane coupling agent KH-550 and 10g of ethanol are added to the mixture, and stirred at 900rpm for 2h. After filtration, the filter cake is dried to constant weight to obtain modified diatomite.

[0049] S2: 30g of PLGA (molecular weight 5000) and 1.5L of dichloromethane are added to a stirred tank, stirred at 3℃ until completely dissolved, 300mg of N-hydroxysuccinimide, 60mg of 4-dimethylaminopyridine and 600μL of N,N-diisopropylcarbodiimide are added in turn, reacted at 30℃ for 11h to form an ester intermediate, 5.5g of glucosamine dissolved in DMF is added to the reaction kettle, and the reaction is continued for 21h to complete the amidation. The reaction system is washed with 5wt% sodium bicarbonate solution and deionized water in turn, dried with anhydrous sodium sulfate, filtered, and the solvent is removed under reduced pressure. The crude product is precipitated with ice-ether, the lower layer is vacuum dried, and the modified PLGA copolymer is obtained.

[0050] S3: 20 g of the modified PLGA copolymer was dissolved in 2 L of dichloromethane / ethanol (volume ratio 7:3) solution, the pH value was adjusted to 5.5 with 0.1 M hydrochloric acid, 60 g of modified diatomite was added, and ultrasonic dispersion was carried out at 28℃ and 400 W for 25 min, followed by stirring at 250 rpm for 10 h, and then the solvent was removed by reduced pressure concentration, the remaining solid was washed with deionized water for 3 times, and dried to constant weight to obtain a modified PLGA powder loaded with the modified PLGA copolymer.

[0051] S4: 8 g of GO and 900 g of deionized water were added to a reaction kettle, ultrasonic dispersion was carried out for 2 h, 8 g of ethylenediamine was added at a stirring speed of 250 rpm, and reaction was carried out at 45℃ for 7 h, 8 g of sodium chloride was added, and then centrifugation was carried out at 900 rpm for 25 min, the supernatant was discarded, and the lower solid was washed with ethanol and deionized water for 2 times respectively, and dried to constant weight to obtain EDA-GO.

[0052] 6 g of the modified PLGA powder loaded with the modified PLGA copolymer, 0.09 g of EDA-GO and 0.6 g of a chitosan acetic acid solution with a concentration of 0.4 wt% were added to a reaction kettle, stirring was carried out at 35℃ for 2.5 h, centrifugal filtration was carried out, the filter cake was washed with deionized water for 3 times, and dried to constant weight to obtain the PLGA microcapsule.

[0053] S5: 4 g of the PLGA microcapsule and 3 g of deionized water were added to a stirring kettle, heated to 50℃, 2 g of dodecyl glucoside and 3 g of polyethylene glycol were added, and stirring was carried out for 25 min, and then naturally cooled to room temperature to obtain the scale inhibitor for water pollution prevention and control.

[0054] Embodiment 3: The embodiment provides a preparation method of a scale inhibitor for water pollution prevention and control, which comprises the following steps:

[0055] S1: 70 g of natural diatomite was dried at 90℃, finely ground through a 300 mesh sieve, and then added to a reaction kettle with 200 mL of a 30 wt% sulfuric acid solution, soaked for 30 h, and reacted in a 90℃ water bath for 60 min, and then filtered, washed to neutral, dried at 100℃, finely ground through a 300 mesh sieve again, and sealed for storage, to complete the acid treatment of the diatomite; 25 g of the acid-treated diatomite and 90 g of deionized water were added to a reaction kettle, 1.5 g of a mixture of silane coupling agent KH-550 and 10 g of ethanol was added under the condition of stirring at 90℃, and stirring reaction was carried out at 1000 rpm for 3 h, and then the filter cake was dried to constant weight to obtain the modified diatomite.

[0056] S2: 40 g of PLGA (molecular weight 5000) and 2 L of dichloromethane were added to a stirred tank, stirred at 5°C until completely dissolved, 400 mg of N-hydroxysuccinimide, 70 mg of 4-dimethylaminopyridine and 700 μL of N,N-diisopropylcarbodiimide were added in turn, reacted at 35°C for 12 h to form an ester intermediate, 6 g of glucosamine dissolved in DMF was added to the reaction tank, and the reaction was continued for 24 h to complete the amidation. The reaction system was washed with 5 wt% sodium bicarbonate solution and deionized water in turn, dried with anhydrous sodium sulfate, filtered, and the solvent was removed under reduced pressure. The obtained crude product was precipitated with ice ethyl ether, the lower layer was taken out and dried under vacuum to obtain the modified PLGA copolymer.

[0057] S3: 30 g of PLGA copolymer was dissolved in 3 L of dichloromethane / ethanol (volume ratio 7:3) solution, the pH value was adjusted to 6.0 with 0.1 M hydrochloric acid, 50 g of modified diatomite was added, and ultrasonic dispersion was carried out at 30°C and 500 W for 30 min, then stirred at 300 rpm for 12 h. The solvent was removed by reduced pressure concentration, the remaining solid was washed with deionized water 4 times, and dried to constant weight to obtain the supported modified PLGA powder.

[0058] S4: 10 g of GO and 1000 g of deionized water were added to the reaction tank, ultrasonic dispersion was carried out for 3 h, 6 g of ethylenediamine was added at 300 rpm, and the reaction was carried out at 50°C for 8 h. After adding 6 g of sodium chloride, centrifugation was carried out at 1000 rpm for 30 min, the supernatant was discarded, and the lower solid was washed with ethanol and deionized water 3 times respectively, and dried to constant weight to obtain EDA-GO.

[0059] 8 g of supported modified PLGA powder, 0.12 g of EDA-GO and 0.8 g of 0.4 wt% chitosan acetic acid solution were added to the reaction tank, stirred at 40°C for 3 h, centrifuged and filtered, the filter cake was washed with deionized water 4 times, and dried to constant weight to obtain the PLGA microcapsule.

[0060] S5: 5 g of PLGA microcapsule and 2 g of deionized water were added to a stirred tank, heated and warmed to 60°C, 3 g of dodecyl glucoside and 6 g of polyethylene glycol were added, stirred for 30 min, and then naturally cooled to room temperature to obtain the scale inhibitor for water pollution prevention and control.

[0061] Comparative Example 1: The difference from Example 1 is that the modification step of glucosamine to PLGA in step S2 is omitted, and the unmodified PLGA is directly used to prepare the supported PLGA powder by compounding with modified diatomite according to step S3, and the rest of the steps remain unchanged to obtain the scale inhibitor for water pollution prevention and control.

[0062] Comparative Example 2: The difference from Example 1 is that the modified PLGA powder loaded in step S3 is only compounded with EDA-GO to prepare a PLGA microcapsule without chitosan, and the remaining steps are unchanged to obtain a scale inhibitor for water pollution prevention and control.

[0063] Comparative Example 3: The difference from Example 1 is that the modified PLGA powder loaded in step S3 is only compounded with a chitosan acetic acid solution with a concentration of 0.4wt% to prepare a PLGA microcapsule without EDA-GO, and the remaining steps are unchanged to obtain a scale inhibitor for water pollution prevention and control.

[0064] Comparative Example 4: The difference from Example 1 is that the EDA-GO in step S4 is replaced by unmodified GO to prepare a PLGA microcapsule, and the remaining steps are unchanged to obtain a scale inhibitor for water pollution prevention and control.

[0065] Comparative Example 5: The difference from Example 1 is that no dodecyl glycoside is added in step S5, and the remaining steps are unchanged to prepare a scale inhibitor for water pollution prevention and control.

[0066] Performance test experiment: Performance tests are performed on Examples 1-3 and Comparative Examples 1-5.

[0067] Release rate: 3g of the scale inhibitors of Examples 1-3 and Comparative Examples 1-5 are dried to constant weight, placed in a stainless steel cup containing 1L of high-salinity wastewater, and left to stand at room temperature. The change in the solid sample is observed, and the release rate is calculated.

[0068] Biodegradation rate: A mixed solution of the scale inhibitor for water pollution prevention and control and microbial inoculum is cultured using a shaking bed method. The chemical oxygen demand of the mixed solution is measured on the 28th day, and then the biodegradation rate is calculated based on the change in the chemical oxygen demand.

[0069] Dispersion performance test: 500mL of simulated high-salinity wastewater is taken, and a scale inhibitor with a concentration of 10mg / L is added. After stirring and standing, the upper clear liquid is taken out, the mass of the bottom sediment is weighed, and the settling rate is calculated.

[0070] Scale inhibition performance test: The scale inhibition efficiency for calcium carbonate and calcium sulfate is calculated according to GB / T 16632-2019, and the scale inhibition efficiency for calcium phosphate is calculated according to GB / T 22626-2008.

[0071] Table 1 Performance test of various water pollution scale inhibitors

[0072]

[0073] As can be seen from Table 1, the release rates of Examples 1-3 are stable at 2.89-2.96mg·h-1 Among them, the comparative example 1 is weak in hydrophilicity and binding force with the carrier due to the non-modification of PLGA with glucosamine, and cannot delay release; the comparative example 2 lacks the physical barrier of microcapsules formed by chitosan, and cannot hinder the rapid diffusion of the components; the comparative example 3 has a sheet layer of EDA-GO and amino groups that can be combined with PLGA and chitosan to form a dense network to delay the release of active ingredients; the comparative example 3 has a loose microcapsule structure due to the absence of EDA-GO, and the active ingredients are easy to diffuse, thus increasing the release rate; and the comparative example 4 uses unmodified GO instead of EDA-GO, and the microcapsule structure is poor in stability and difficult to delay release.

[0074] The biodegradation rates of the examples 1-3 are between 84.3-85.6%, which are superior to those of the comparative examples 1-5. The comparative example 1 directly uses unmodified PLGA, which has poor hydrophilicity of molecular chain, and it is difficult for microorganisms to adhere and metabolize, thus reducing the degradation rate. Chitosan as a natural degradable polysaccharide can provide nutrition for microorganisms and promote colonization, and enhance the biocompatibility of the system. The comparative example 2 lacks chitosan, and the activity of microorganisms is inhibited. In the examples, the GO is modified by ethylenediamine, and the surface amino group improves the binding force with the biocompatible components and reduces the toxicity to microorganisms. In the comparative example 4, the unmodified GO has oxygen-containing groups on the surface, which can easily cause oxidative stress and inhibit the activity of microorganisms, thus reducing the degradation rate. In addition, in the examples, dodecyl glucoside can improve the dispersibility of the material, so that the microorganisms can more easily contact the degradation site. The comparative example 5 lacks this component, and the material is easy to agglomerate, so that the microorganisms are difficult to fully act, and the degradation rate is also slightly lower than that of the examples.

[0075] The sedimentation rates of the scale inhibitors in the examples 1-3 are between 6.2-6.5%, which are excellent in dispersibility. The comparative examples 1-5 have high sedimentation rates (7.0%-7.7%) due to the absence of key components or modification steps. The comparative example 1 has a significant decrease in the dispersibility of the scale inhibitor as a whole due to the non-modification of PLGA with glucosamine, which greatly reduces the hydrophilicity of PLGA and the compatibility with other components. The comparative example 2 has a decrease in the dispersibility of the scale inhibitor due to the absence of chitosan, which makes the structure of the PLGA microcapsule unstable and difficult to maintain the uniform dispersion state of the particles. The comparative example 3 lacks EDA-GO, which loses its role in enhancing the dispersion of the interface in the system. The comparative example 4 uses unmodified GO, which has poor dispersibility and is easy to agglomerate, thus significantly increasing the overall sedimentation rate of the scale inhibitor. The comparative example 5 has a decrease in the dispersion stability of the particles due to the absence of dodecyl glucoside, but the influence on the dispersibility is weaker than the absence of the structure modification step or the omission of the key functional components.

[0076] The anti-fouling performance of examples 1-3 and comparative examples 1-5 is relatively excellent as a whole. After the PLGA is modified by glucosamine, a large number of amino groups and polyhydroxy groups are introduced into the molecular chain. These polar groups can combine with scale ions such as Ca 2+ , CO3 2- , SO4 2- , PO4 3- , etc. in water through coordination bonds, hinder the crystal from agglomerating and growing, the diatomite retains the porous structure after modification, and the compatibility with other components is improved, the sheet structure of EDA-GO has a large specific surface area, the surface amino groups can be closely combined with PLGA and chitosan, the addition of chitosan forms a microcapsule physical barrier to hinder the rapid diffusion of components, in addition, dodecyl glucoside as a surfactant can improve the dispersibility of the material in water, ensure that each anti-fouling component uniformly contacts scale ions and crystals, fully play a role, and finally realize efficient synergistic anti-fouling of CaCO3, CaSO4 and CaPO4. The anti-phosphocalcium fouling efficiency of comparative example 1 is relatively poor, which is mainly due to the fact that the PLGA is not modified by glucosamine. The amino and polyhydroxy groups contained in the glucosamine molecule can form stable coordination bonds with calcium ions in the phosphocalcium crystal, thereby effectively interfering with the nucleation and growth of phosphocalcium and inhibiting the crystallization and precipitation thereof.

[0077] It should be noted that in this text, terms such as "include", "contain" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such a process, method, article or device.

[0078] Although embodiments of the present application have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present application.

Claims

1. A method for preparing a scale inhibitor for water pollution control, characterized in that, Preparation method comprising the following steps: Step 1: screen the natural diatomite and modify it with KH-550 silane coupling agent to obtain modified diatomite; Step 2: convert polylactic acid-glycolic acid copolymer into ester intermediate by using N,N-diisopropyl carbodiimide and N-hydroxy succinimide as carboxyl activators and 4-dimethylamino pyridine as alkaline catalyst, and then carry out amidation reaction with glucosamine to obtain modified polylactic acid-glycolic acid copolymer; dip the modified polylactic acid-glycolic acid copolymer in the modified diatomite to obtain supported modified polylactic acid-glycolic acid copolymer powder; Step 3: coat the supported modified polylactic acid-glycolic acid copolymer powder in the chitosan shell layer doped with ethylenediamine modified graphene oxide by electrostatic self-assembly to obtain polylactic acid-glycolic acid copolymer microcapsule; Step 4: mix polylactic acid-glycolic acid copolymer microcapsule, deionized water, dodecyl glucoside and polyethylene glycol by stirring to obtain scale inhibitor for water pollution prevention and control; The specific preparation process of the modified polylactic acid-glycolic acid copolymer is as follows: add polylactic acid-glycolic acid copolymer and dichloromethane into a stirring kettle, stir at 0-5℃ until completely dissolved, add N-hydroxy succinimide, 4-dimethylamino pyridine and N,N-diisopropyl carbodiimide, react at 25-35℃ for 10-12h, then dissolve glucosamine in N,N-dimethylformamide and add into the reaction kettle, continue to react for 18-24h, wash the reaction system with 5wt% sodium bicarbonate solution and deionized water in sequence, dry with anhydrous sodium sulfate, filter, remove the solvent under reduced pressure, precipitate the obtained crude product with ice ether, take the lower layer and dry under vacuum to obtain the modified polylactic acid-glycolic acid copolymer; The specific preparation process of the supported modified polylactic acid-glycolic acid copolymer powder is as follows: dissolve the modified polylactic acid-glycolic acid copolymer in dichloromethane / ethanol mixed solution, adjust the pH value to 5.0-6.0 with 0.1M hydrochloric acid, add modified diatomite, ultrasonic dispersion at 25-30℃ and 300-500W for 20-30min, stir at 200-300rpm for 8-12h, remove the solvent under reduced pressure, wash and dry the remaining solid to obtain the supported modified polylactic acid-glycolic acid copolymer powder; The specific preparation process of the polylactic acid-glycolic acid copolymer microcapsule is as follows: add supported modified polylactic acid-glycolic acid copolymer powder, ethylenediamine modified graphene oxide and 0.4wt% chitosan acetic acid solution into a reaction kettle, stir at 30-40℃ for 2-3h, centrifugal filter, wash the filter cake with deionized water for 3-4 times, dry to constant weight to obtain the polylactic acid-glycolic acid copolymer microcapsule.

2. The method for preparing a scale inhibitor for water pollution prevention according to claim 1, characterized in that, The specific preparation process of the modified diatomite is as follows: add acid-treated diatomite and deionized water into a reaction kettle, add silane coupling agent KH-550 and ethanol under the conditions of 70-90℃ and stirring, stir at 800-1000rpm for 1-3h, filter, dry the filter cake to constant weight to obtain the modified diatomite; The mass ratio of the acid-treated diatomite, deionized water, silane coupling agent and ethanol is 20-30:90-110:0.5-1.5:8-12.

3. The method according to claim 2, wherein the method is characterized by, The acid treatment method of the diatomite is specifically as follows: The natural diatomite is dried, finely ground through a 300-mesh sieve, soaked in a 30wt% sulfuric acid solution at 20-25℃ for 20-30h, incubated at 70-90℃ for 40-60min, cooled, suction filtered, washed and dried to complete the acid treatment of the diatomite; The dosage ratio of the natural diatomite and sulfuric acid is 60-80g:100-200mL.

4. The method for preparing the scale inhibitor for water pollution prevention and treatment according to claim 1, characterized in that, The dosage ratio of the polylactic acid-glycolic acid copolymer, dichloromethane, N-hydroxysuccinimide, 4-dimethylaminopyridine, N,N-diisopropylcarbodiimide, glucosamine and N,N-dimethylformamide is 2-4g: 0.1-0.2L:30-50mg:6-8mg:60-80μL:0.5-0.6g:20-30mL.

5. The method for preparing the scale inhibitor for water pollution prevention and treatment according to claim 1, characterized in that, The dosage ratio of the modified polylactic acid-glycolic acid copolymer, dichloromethane / ethanol and modified diatomite is 2-4g:200-400mL:10-20g.

6. The method for preparing a scale inhibitor for water pollution prevention according to claim 1, characterized in that, The mass ratio of the supported modified polylactic acid-glycolic acid copolymer powder, ethylenediamine-modified graphene oxide and chitosan acetic acid solution is 5-8:0.05-0.12:0.4-0.

8.

7. The method according to claim 6, wherein the method is characterized by, The ethylenediamine-modified graphene oxide is prepared by the following steps: The graphene oxide and deionized water are added to a reaction kettle, ultrasonically dispersed for 1-3h, then ethylenediamine is added, stirred at 40-50℃ and 200-300rpm for 6-8h, then sodium chloride is added, centrifuged at 800-1000rpm for 20-30min, the lower solid is washed with ethanol and deionized water for 2-3times respectively, and dried to constant weight to obtain the ethylenediamine-modified graphene oxide; The mass ratio of the graphene oxide, deionized water, ethylenediamine and sodium chloride is 5-10:800-1000:5-8:5-10.

8. The method for preparing a scale inhibitor for water pollution prevention according to claim 1, characterized in that, The specific preparation method of the scale inhibitor for water pollution prevention and control is as follows: The polylactic acid-glycolic acid copolymer microcapsule and deionized water are added to a stirred kettle, dodecyl glucoside and polyethylene glycol are added at 40-60℃, stirred for 20-30min, and naturally cooled to room temperature to obtain the scale inhibitor for water pollution prevention and control.

9. The method according to claim 8, wherein the method is characterized by, The mass ratio of the polylactic acid-glycolic acid copolymer microcapsule, deionized water, dodecyl glucoside and polyethylene glycol is 30-50:20-40:10-13:5-8.

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