Reclaimed water reverse osmosis scale inhibitor and preparation method thereof

Abstract

The invention discloses a reclaimed water reverse osmosis scale inhibitor and a preparation method thereof, the reclaimed water reverse osmosis scale inhibitor comprises a hyperbranched polymer formed by graft polymerization of maleic anhydride, maleic acid unsaturated ester and allyl ether, and the mass ratio of maleic anhydride to maleic acid unsaturated ester to allyl ether is (1-1.5): (0.5-1.0): (0.1-0.2). The scale inhibitor can be effectively applied to a reclaimed water reuse reverse osmosis system, calcium carbonate scale, silicon scale, calcium sulfate scale and other scales of the reverse osmosis system are greatly prevented and reduced, and the scale inhibitor is good in compatibility with aluminum ions and positive ion PAM, so that pollution and blockage of the reverse osmosis system are relieved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of industrial water treatment, and particularly relates to a scale inhibitor suitable for a reverse osmosis system for reclaimed water reuse and a preparation method thereof. BACKGROUND

[0002] Reverse osmosis membrane technology is a high-efficiency desalination method, which is widely used in seawater desalination, brackish water desalination and reclaimed water reuse and other fields. Its typical treatment process includes multi-medium filtration, ultrafiltration, dosing treatment (scale inhibitor, reducing agent), security filtration and reverse osmosis treatment. However, the water quality of the reclaimed water is usually worse than that of the conventional surface water or underground water, and has the characteristics of high hardness, high sulfate content, high concentration of metal oxides and organic matter. These pollutants are prone to cause reverse osmosis membrane fouling, and it is difficult to clean after fouling, which leads to increased energy consumption, shortened membrane life and reduced desalination rate, and seriously affects normal operation.

[0003] At present, traditional phosphorus-containing scale inhibitors (such as organic phosphonic acid) are prone to cause water eutrophication, and non-phosphorus polymer scale inhibitors have the risk of membrane fouling. Although the existing technology (such as patent CN109592746B) proposes a network hyperbranched chain scale inhibitor, which can partially alleviate the fouling problem, but still has two defects: one is that the high organic phosphorus content may lead to eutrophication of concentrated water and pollution of the environment; the other is that the synthesis process is complex, and the practicality is limited. Therefore, developing a new type of reverse osmosis scale inhibitor which is efficient, non-phosphorus and easy to degrade has become a technical problem to be solved at present. SUMMARY

[0004] In order to overcome the above-mentioned deficiencies, the application discloses a reclaimed water reverse osmosis scale inhibitor and a preparation method thereof, which can be effectively applied to a reclaimed water reverse osmosis system, greatly prevent and reduce calcium carbonate scale, silicon scale, calcium sulfate scale and other scaling in the reverse osmosis system, and have good compatibility with aluminum ions and cationic PAM, thereby relieving the fouling of the reverse osmosis system.

[0005] The technical scheme of the application is as follows:

[0006] A reclaimed water reverse osmosis scale inhibitor comprises a hyperbranched polymer formed by graft polymerization of maleic anhydride, maleic acid unsaturated ester and allyl ether, and the mass ratio of the maleic anhydride, the maleic acid unsaturated ester and the allyl ether is 1-1.5:0.5-1.0:0.1-0.2.

[0007] Preferably, the maleic acid unsaturated ester is allyl maleate or monomethyl allyl maleate.

[0008] Preferably, the allyl ether is one of allyl polyoxyethylene ether APEG200 and APEG400 or a mixture of the two.

[0009] A preparation method of a reverse osmosis scale inhibitor for reclaimed water, comprising the following steps:

[0010] S1: under the condition of a catalyst, maleic anhydride is mixed with unsaturated alcohol in proportion, toluene is added as a water-carrying agent, and dehydration reaction is carried out at 60-80 DEG C under reduced pressure, and maleic unsaturated ester is obtained by purification through reduced pressure distillation;

[0011] S2: under the protection of nitrogen, maleic anhydride is dissolved in tetrahydrofuran, a mixed solution of maleic unsaturated ester and allyl ether and an initiator solution are added dropwise at a certain temperature, and reaction is carried out for a period of time, and a grafted polymerization product of maleic anhydride, maleic unsaturated ester and allyl ether is obtained after distillation and purification;

[0012] S3: after the grafted polymerization product obtained in step S2 is dissolved in water, a reverse osmosis scale inhibitor for reclaimed water is prepared.

[0013] Preferably, in S1, maleic anhydride is mixed with unsaturated alcohol in a molar ratio of 1:1-1.2:1.

[0014] Preferably, in S1, the catalyst is p-toluenesulfonic acid, and the amount of catalyst is 0.5%-1% of the total mass of maleic anhydride and unsaturated alcohol.

[0015] Preferably, in S1, the unsaturated alcohol is allyl alcohol or methyl allyl alcohol.

[0016] Preferably, in S2, the initiator solution is prepared by dissolving initiator BPO in tetrahydrofuran, and the amount of initiator BPO is 0.5%-1% of the total mass of maleic anhydride, maleic unsaturated ester and allyl ether.

[0017] Preferably, in S2, the mixed solution of maleic unsaturated ester and allyl ether and the initiator solution are added dropwise into the maleic anhydride solution within 2-5h, the temperature of the material is controlled at 60-70 DEG C during the dropwise addition process, and the reaction is carried out for 15-18h.

[0018] Preferably, in S3, the solid content of the reverse osmosis scale inhibitor for reclaimed water is 42-43%.

[0019] Beneficial effects: the present application provides a reverse osmosis scale inhibitor for reclaimed water and a preparation method thereof, which has the following advantages:

[0020] (1) The reverse osmosis scale inhibitor of the present application has excellent scale inhibition effect on carbonate scale, sulfate scale and silicate scale, and is good in cation compatibility, and can effectively cope with the impact caused by the fluctuation of the water quality of the reclaimed water reverse osmosis inlet.

[0021] (2) The scale inhibitor of the present application is a grafted polymer, has excellent dispersing performance and comprehensive scale inhibition capacity, and its low dosage characteristics avoid the membrane channel blockage problem caused by excessive use of small molecule organic phosphorus scale inhibitors, and overcome the membrane surface pollution problem caused by self-winding and self-adhesion of conventional polymer scale inhibitors.

[0022] (3) The scale inhibitor of the present application does not contain phosphorus element, is non-toxic and easy to biodegrade, can significantly reduce the eutrophication risk of water body, and meets the green environmental protection requirement.

[0023] (4) The synthesis process of the present application is simple and efficient, is convenient for industrial production, and has high practicability and economy. DETAILED DESCRIPTION

[0024] The present application is further described below. The following examples are only used to more clearly illustrate the technical solutions of the present application, and cannot be used to limit the protection scope of the present application.

[0025] A preparation method of a reclaimed water reverse osmosis scale inhibitor, and the specific steps are as follows:

[0026] S1: under the condition of a catalyst, maleic anhydride is mixed with unsaturated alcohol in proportion, toluene is added as a water-carrying agent, dehydration reaction is carried out at 60-80 DEG C under reduced pressure, and maleic acid unsaturated ester is obtained by vacuum distillation purification; in the embodiment, a four-necked flask is provided with a magnetic stirrer, a condenser water separator and a thermometer, a catalyst p-toluenesulfonic acid, maleic anhydride and unsaturated alcohol are added, and toluene is added as a water-carrying agent. The magnetic stirrer is turned on, the four-necked flask is heated while stirring, the reaction system is dehydrated at 60-80 DEG C under reduced pressure, after the reaction is completed, toluene and unreacted raw materials are removed by vacuum distillation, and maleic acid unsaturated ester is obtained;

[0027] S2: under the protection of nitrogen, maleic anhydride is dissolved in tetrahydrofuran, a mixed solution of maleic acid unsaturated ester and allyl ether and an initiator solution are added dropwise at a certain temperature, and the mixture is incubated for a period of time, and then the grafted polymerization product of maleic anhydride, maleic acid unsaturated ester and allyl ether is obtained by distillation purification; in the embodiment, a four-necked flask is provided with a magnetic stirrer, a reflux condenser and a thermometer, tetrahydrofuran and maleic anhydride are added and uniformly dissolved, nitrogen is introduced to remove air, maleic acid unsaturated ester and allyl ether are mixed, an initiator solution is obtained by dissolving an initiator BPO in tetrahydrofuran, the temperature is raised to 60 DEG C, the mixed solution of maleic acid unsaturated ester and allyl ether and the initiator solution are slowly added dropwise respectively, the reaction temperature is controlled to be 60-70 DEG C, the dropwise addition is completed within 2-5 h, and then the mixture is incubated for a period of time, after the reaction is completed, the solvent and unreacted monomers are removed by distillation, and the grafted polymerization product of maleic anhydride, maleic acid unsaturated ester and allyl ether is obtained.

[0028] S3: proportionally adding water to dissolve the grafted polymer product prepared in step S2 to prepare a middle water reverse osmosis scale inhibitor.

[0029] Examples 1, 2, 3 and 4 were prepared according to the preparation parameters of each example shown in Table 1, and the solid content (actual measured value) of sample 1, sample 2, sample 3 and sample 4 was 42.25%, 42.12%, 42.52% and 42.46% respectively.

[0030] Preparation parameters of each example in Table 1

[0031]

[0032] Note: The maleic acid unsaturated ester in Table 1 is prepared by step S1.

[0033] In the present application, the solid content of the middle water reverse osmosis scale inhibitor is controlled at 42-43%. The scale inhibitor prepared in the present application can be used as a 10-fold concentrated solution in actual use, and the dosage concentration is 0.2-0.8 mg / L.

[0034] Reverse osmosis scale inhibition performance test:

[0035] The middle water reverse osmosis scale inhibitor samples 1, 2, 3 and 4 prepared by the above examples and the comparative example (an imported membrane scale inhibitor ASD200) were taken, and the middle water of a certain coal chemical industry in Ningxia was used as test water, and the reverse osmosis water quality was as shown in Table 2:

[0036] Table 2 Reverse osmosis water quality

[0037]

[0038] Based on the above test conditions, the performance was evaluated according to HG / T 5166-2017 "Evaluation method for scale inhibition performance of reverse osmosis scale inhibitor", and the drug concentration was 0.5 mg / L, and the test results were as shown in Table 3:

[0039] Table 3 Membrane unit water production Q i P Apparent recovery rate before reduction %

[0040] sample Apparent recovery % Sample 1 78.76 Sample 2 79.46 Sample 3 78.23 Sample 4 79.12 Comparative Example 75.23 Blank group 45.25

[0041] Membrane unit water production (Q i PThe higher the apparent recovery rate before reduction, the better the scale inhibition performance of the agent. The test results in Table 3 show that the apparent recovery rates of samples 1-4 and the comparative example (ASD200) are significantly higher than that of the blank group (45.25%), proving that the scale inhibitor can effectively inhibit membrane fouling. Among them, the performance of samples 1-4 prepared by the application is better than that of the comparative example, especially sample 2, whose recovery rate reaches 79.46%, and the scale inhibition effect is the best.

[0042] This result fully shows that the hyperbranched polymer structure inhibitor prepared by the application can significantly improve the scale inhibition efficiency, and especially has stronger adaptability to complex water quality such as calcium sulfate and silica scale compared with the comparative example. In addition, the scale inhibitor uses a phosphorus-free environmentally friendly formula, avoiding the eutrophication problem that may be caused by the traditional phosphorus-containing scale inhibitor. At the same time, high-efficiency scale inhibition can be achieved under the condition of low dosage (0.5 mg / L), and excellent economy and practicability are combined.

[0043] The above is only the preferred embodiment of the application, and it should be pointed out that for ordinary skilled persons in the technical field, several improvements and modifications can be made without departing from the technical principles of the application, and these improvements and modifications should also be regarded as the protection scope of the application.

Claims

1. A scale inhibitor for reverse osmosis of reclaimed water, characterized in that: The invention comprises a hyperbranched polymer formed by graft polymerization of maleic anhydride, unsaturated maleic acid ester and allyl ether, wherein the mass ratio of maleic anhydride, unsaturated maleic acid ester and allyl ether is 1-1.5:0.5-1.0:0.1-0.

2.

2. The scale inhibitor for reverse osmosis water according to claim 1, characterized in that: The unsaturated maleic acid ester is allyl maleate or monomethyl allyl maleate.

3. The scale inhibitor for reverse osmosis water according to claim 1, characterized in that: The allyl ether is one or a mixture of allyl polyoxyethylene ether APEG200 and APEG400.

4. A method for preparing the reverse osmosis scale inhibitor for recycled water according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1: Under catalyst conditions, maleic anhydride and unsaturated alcohol are mixed in proportion, toluene is added as a water-carrying agent, and dehydration reaction is carried out under reduced pressure at 60-80°C, and unsaturated maleic acid ester is obtained by purification by reduced pressure distillation; S2: Under nitrogen protection, maleic anhydride is dissolved in tetrahydrofuran, and a mixture of unsaturated maleic acid ester and allyl ether and an initiator solution are added dropwise at a certain temperature, and the mixture is kept warm for a period of time to obtain a graft polymerization product of maleic anhydride, unsaturated maleic acid ester and allyl ether after purification by distillation; S3: adding water to dissolve the grafted polymer product obtained in step S2 to prepare a reverse osmosis scale inhibitor for reclaimed water.

5. The preparation method according to claim 4, characterized in that In the S1, maleic anhydride and unsaturated alcohol are mixed in a molar ratio of 1:1 to 1.2:

1.

6. The preparation method according to claim 4, characterized in that In S1, the catalyst is p-toluenesulfonic acid, and the amount of the catalyst used is 0.5%-1% of the total mass of maleic anhydride and the unsaturated alcohol.

7. The preparation method according to claim 4, characterized in that In S1, the unsaturated alcohol is allyl alcohol or methallyl alcohol.

8. The preparation method according to claim 4, characterized in that: In S2, the initiator solution is prepared by dissolving initiator BPO in tetrahydrofuran, and the amount of initiator BPO used is 0.5%-1% of the total mass of the three monomers of maleic anhydride, unsaturated maleic acid ester and allyl ether.

9. The preparation method according to claim 4, characterized in that In S2, the mixed solution of unsaturated maleic acid ester and allyl ether and the initiator solution are added dropwise to the maleic anhydride solution within 2 to 5 hours. During the addition, the material temperature is controlled at 60° C. to 70° C., and the insulation reaction time is 15 to 18 hours.

10. The preparation method according to claim 4, characterized in that: In the S3, the solid content of the reclaimed water reverse osmosis antiscalant is 42-43%.

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