Antifouling agents and methods for their preparation

Abstract

This invention provides a scale inhibitor and its preparation method. The scale inhibitor is used for phosphogypsum leachate in a reverse osmosis membrane system. The scale inhibitor comprises the following raw materials in parts by weight: 10%-20% aluminum compound, 5%-10% organophosphonic acid, 2%-5% anionic surfactant, 4%-10% solvent, and the remainder is purified water. This addresses the problem of scaling in phosphogypsum leachate in reverse osmosis membrane systems by existing commercially available scale inhibitors, which suffer from poor targeting and scale inhibition effects. This invention introduces an aluminum compound, in which Al... 3+ It will react with silicon in a competitive manner with fluorine, from SiF6 2‑ Complex ions replace silicon to form acid-soluble AlF₂. x 3‑x Complexing ions cause SiF6 in the phosphogypsum leachate to form complex ions. 2‑ Reduce or inhibit SiF6 2‑ This reduces or inhibits the formation of potassium / sodium fluorosilicate scale.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of phosphogypsum leachate treatment, and more particularly to a scale inhibitor and a preparation method thereof. BACKGROUND

[0002] Phosphogypsum refers to solid waste residues produced when phosphorite is treated with sulfuric acid in the production of phosphoric acid, and the main component is calcium sulfate. At present, nearly one hundred million tons of phosphogypsum are discharged annually in China, and phosphogypsum leachate is formed by the leaching of phosphogypsum. The leachate sources can be divided into two parts, one part is the moisture carried by the phosphogypsum itself when it is placed in the yard, and the other part is caused by natural rainfall. The main characteristics of the leachate are strong acidity, rich in phosphates, sulfates, fluorosilicates, and fluorides. Once it penetrates into the underground, it not only causes a large amount of waste of phosphorus and fluorine resources, but also seriously pollutes the nearby groundwater and surface water resources. With the increasingly stringent environmental monitoring indicators, the low-cost calcium method treatment technology widely used in the industry cannot meet the requirements.

[0003] Therefore, many enterprises use reverse osmosis membrane treatment systems that can effectively concentrate and recycle phosphorus and fluorine resources in phosphogypsum leachate and produce water that can be used for production water. The concentrated water after reverse osmosis is used for dilute phosphoric acid recovery, and the production water is used for production water, which can greatly save water and greatly reduce pollution, and has very important significance for pollution prevention, economic benefits, sustainable development, and other aspects. However, because phosphogypsum leachate is rich in phosphates, sulfates, fluorosilicates, and fluorides, the reverse osmosis membrane filters water molecules to the clean water side, and the impurity concentration on the concentrated water side becomes larger and larger, which is prone to produce scale mainly composed of potassium / sodium fluorosilicate, resulting in membrane blockage, membrane flux reduction, desalination efficiency reduction, and osmotic pressure increase, and even the entire reverse osmosis membrane system may be paralyzed.

[0004] Therefore, the study of scale inhibition technology for phosphogypsum leachate has positive practical significance and application value for the normal operation of the phosphogypsum leachate grading reuse system and the improvement of economic and environmental benefits.

[0005] In industrial water treatment, the scale inhibition dispersant mainly affects the crystallization of calcium carbonate, calcium sulfate and other slightly soluble salts through chelation, lattice distortion and dispersion. However, the general polycarboxylic acid (salt) and organic phosphonic acid cannot form stable complexes with sodium and potassium ions, so the polycarboxylic acid and organic phosphonic acid have little effect on the crystallization of potassium / sodium fluosilicate slightly soluble salt through the chelation mechanism, but the polycarboxylic acid and organic phosphonic acid can affect the crystallization of potassium / sodium fluosilicate through the lattice distortion and dispersion mechanisms. (1) Lattice distortion effect: In low pH solution, the surface of potassium / sodium fluosilicate crystal is usually positively charged, while the organic phosphonic acid and polycarboxylic acid (salt) can be partially ionized in the solution, and the negatively charged anions can be adsorbed to the active growth point of the crystal and the surface of the crystal, inhibiting the normal growth of potassium / sodium fluosilicate crystal according to the lattice arrangement, causing the crystal to be distorted and the growth to be inhibited. (2) Dispersion effect: When anionic scale inhibition dispersant such as polycarboxylic acid is added, due to physical or chemical action, it can be adsorbed to the surface of potassium / sodium fluosilicate crystal particles, making the surface of the crystal particles have the same negative charge, and the crystal particles repel each other, so that the microcrystals can be effectively dispersed and difficult to aggregate.

[0006] Therefore, the scale inhibition dispersant used in industrial water treatment can reduce the potassium / sodium fluosilicate scaling, but compared with its effect on the crystallization of calcium carbonate, calcium sulfate and other slightly soluble salts in industrial cooling water system, the scaling type studied in this paper is mainly potassium / sodium fluosilicate scale, and the solution properties are strongly acidic, which are quite different from the industrial cooling water system, so the scale inhibition dispersant used in industrial water treatment has little effect on the crystallization of potassium / sodium fluosilicate scale. For example, the ionization of organic phosphonic acid and polycarboxylic acid in acidic solution is weak, which weakens the adsorption of scale inhibition dispersant on the surface of potassium / sodium fluosilicate crystal particles, and the scale inhibition effect is obviously poorer than that in the corresponding industrial cooling water system. SUMMARY

[0007] The present application provides a kind of for phosphogypsum leachate in reverse osmosis membrane system scale inhibitor and its preparation method, to solve the existing market scale inhibitor for phosphogypsum leachate in reverse osmosis membrane system scaling problem, there is not strong, scale inhibition effect is not good and other technical problems.

[0008] According to one aspect of the present application, a scale inhibitor is provided for use in phosphogypsum leachate in a reverse osmosis membrane system, the scale inhibitor comprising the following raw materials in parts by weight: aluminum compound 10%-20%, organic phosphonic acid 5%-10%, anionic surfactant 2%-5%, solvent 4%-10%, and the rest is purified water.

[0009] Preferably, on the basis of the above scheme, the aluminum compound includes one or more of aluminum oxide, aluminum chloride, aluminum sulfate, aluminum hydroxide, and aluminum nitrate.

[0010] Based on the above scheme, preferably, the organophosphorus scale inhibitor is one or more of polyaminopolyether methylenephosphonic acid, aminotrimethylenephosphonic acid, ethylenediaminetetramethylenephosphonic acid, and hexamethylenediaminetetramethylenephosphonic acid.

[0011] Based on the above scheme, the preferred option is dodecylbenzenesulfonic acid.

[0012] Preferably, based on the above scheme, the solvent is industrial ethanol.

[0013] The present invention also provides a method for preparing the scale inhibitor of claim 1, comprising the following steps:

[0014] S1, mix dodecylbenzenesulfonic acid and industrial ethanol at a mass ratio of 1:2 to 5 and stir evenly at room temperature;

[0015] S2, mix aluminum compound and water at a mass ratio of 1:2 to 5, stir at room temperature to fully dissolve aluminum sulfate;

[0016] S3, mix the raw materials prepared in step S1 with the raw materials prepared in step S2, and stir evenly at room temperature;

[0017] S4. The raw materials obtained in S3 are mixed with organophosphonic acid at a mass ratio of 9 to 19:1, and then stirred evenly at room temperature to obtain the finished scale inhibitor.

[0018] The present invention provides a scale inhibitor that incorporates an aluminum compound, wherein the aluminum compound contains Al. 3+ It will react with silicon in a competitive manner with fluorine, from SiF6 2- Complex ions replace silicon to form acid-soluble AlF₂. x 3-x Complexing ions cause SiF6 in the phosphogypsum leachate to form complex ions. 2- Reduce or inhibit SiF6 2- This reduces or inhibits the formation of potassium / sodium fluorosilicate scale.

[0019] Specifically, the reaction in which dissolved aluminum and silicon compete for fluorine in acidic solution is as follows:

[0020]

[0021] On the other hand, the synergistic surfactant dodecylbenzenesulfonic acid of the present invention increases the crystallization induction period and the limiting supersaturation of potassium fluorosilicate, thereby making it difficult for potassium fluorosilicate / sodium to form crystal nuclei in the solution, effectively alleviating the scaling of potassium fluorosilicate / sodium.

[0022] The organic phosphorus scale inhibitor in the traditional formula inhibits the normal growth of potassium / sodium fluorosilicate crystals arranged by crystal lattice by the effect of crystal lattice distortion, so that the crystals are distorted and the growth is inhibited. The scale inhibitor of the application has the synergistic effect of the aluminum compound as the main component, the organic phosphorus scale inhibitor and the surfactant to strengthen the scale inhibition effect.

[0023] Compared with the prior art, the scale inhibitor of the application has simple preparation method, stable performance and high scale inhibition performance. It can effectively prevent the phosphogypsum leachate from scaling on the reverse osmosis membrane system, ensure the normal operation of the system, meet the market demand and effectively solve the problem of insufficient scale inhibition effect of the prior art on the phosphogypsum leachate. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the application, the drawings needed for the description of the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description only some embodiments of the application, and for those skilled in the art, other drawings can also be obtained without creative labor. In the drawings:

[0025] In the drawings:

[0026] Figure 1 The flow chart of the preparation method of the scale inhibitor of the application. DETAILED DESCRIPTION

[0027] The specific embodiments of the application will be further described in detail below in combination with the drawings and examples. The following examples are used to illustrate the application, but not to limit the scope of the application.

[0028] It should be understood that when used in the specification and the appended claims, the term "comprising" indicates the presence of the described features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0029] In order to make the drawing simple, only the parts related to the application are shown in the drawings, which do not represent the actual structure of the product. In addition, in order to make the drawing simple and easy to understand, in some drawings, only one of the components with the same structure or function is shown, or only one of them is marked. In this paper, "one" not only means "only one", but also means "more than one".

[0030] It should be further understood that the term "and / or" used in the specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes these combinations.

[0031] In the embodiments shown in the drawings, the indications of directions, such as up, down, left, right, front and back, are used to explain the structure and movement of various components of the application and are not absolute but relative. These indications are appropriate when the components are in the positions shown in the drawings. If the positions of the components change, the indications of the directions also change accordingly.

[0032] In addition, in the description of the present application, the terms "first", "second", and the like are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, specific embodiments of the present application will be described below with reference to the drawings. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained from these drawings without creative labor, and other embodiments can also be obtained.

[0034] Please refer to Figure 1 As shown in the drawings, the present application is a scale inhibitor for phosphogypsum leachate in a reverse osmosis membrane system, the scale inhibitor comprising the following raw materials in parts by weight: aluminum compound 10%-20%, organic phosphonic acid 5%-10%, anionic surfactant 2%-5%, solvent 4%-10%, and the rest being purified water.

[0035] Among them, the aluminum compound includes one or more of aluminum oxide, aluminum chloride, aluminum sulfate, aluminum hydroxide, and aluminum nitrate, the organic phosphonic scale inhibitor is one or more of polyamino polyether methylidene phosphonic acid, aminotrimethylene phosphonic acid, ethylenediamine tetramethylene phosphonic acid, and hexanediamine tetramethylene phosphonic acid, the anionic surfactant is dodecyl benzene sulfonic acid, and the solvent is industrial ethanol.

[0036] The present application also provides a method for preparing the scale inhibitor of claim 1, comprising the following steps:

[0037] S1, mix dodecyl benzene sulfonic acid and industrial ethanol according to a mass ratio of 1:2-5, and stir uniformly;

[0038] S2, mix aluminum compound and water according to a mass ratio of 1:2-5, stir, and fully dissolve the aluminum sulfate;

[0039] S3, mix the raw materials prepared in step S1 with the raw materials prepared in S2, and stir uniformly;

[0040] S4, prepare the raw materials prepared in S3 with organic phosphonic acid according to a mass ratio of 9-19:1, and then stir uniformly, to obtain the finished scale inhibitor.

[0041] In order to verify the specific implementation effect of the present application, the following specific examples are used to illustrate:

[0042] The scale inhibitor described in this example is prepared by the following steps in the order:

[0043] S1, 2 parts by mass of dodecyl benzene sulfonic acid is mixed with 3 parts by mass of industrial ethanol, stirred uniformly at room temperature;

[0044] S2, 20 parts by mass of aluminum sulfate is mixed with 70 parts by mass of water, and the aluminum sulfate is fully dissolved by stirring at room temperature;

[0045] S3, the raw material prepared in S1 is mixed with the raw material prepared in S2, and stirred uniformly at room temperature;

[0046] S4, the raw material prepared in S3 is mixed with 5 parts by mass of polyamino polyether methylene phosphonic acid, and stirred uniformly at room temperature to obtain a scale inhibitor for gypsum leachate in reverse osmosis membrane system.

[0047] Example 2

[0048] The scale inhibitor described in this example is prepared by the following steps in the order:

[0049] S1, 2 parts by mass of dodecyl benzene sulfonic acid is mixed with 3 parts by mass of industrial ethanol, stirred uniformly at room temperature;

[0050] S2, 15 parts by mass of aluminum chloride is mixed with 70 parts by mass of water, and the aluminum chloride is fully dissolved by stirring at room temperature;

[0051] S3, the raw material prepared in S1 is mixed with the raw material prepared in S2, and stirred uniformly at room temperature;

[0052] S4, the raw material prepared in S3 is mixed with 10 parts by mass of aminotrimethylene phosphonic acid, and stirred uniformly at room temperature to obtain a scale inhibitor for gypsum leachate in reverse osmosis membrane system.

[0053] Example 3

[0054] The scale inhibitor described in this example is prepared by the following steps in the order:

[0055] S1, 5 parts by mass of dodecyl benzene sulfonic acid is mixed with 9 parts by mass of industrial ethanol, stirred uniformly at room temperature;

[0056] S2, 10 parts by mass of aluminum sulfate is mixed with 70 parts by mass of water, and the aluminum sulfate is fully dissolved by stirring at room temperature;

[0057] S3, the raw material prepared in S1 is mixed with the raw material prepared in S2, and stirred uniformly at room temperature;

[0058] S4, the raw materials prepared in S3 are mixed with 6 parts by mass of hexamethylene diamine tetramethylene phosphonic acid, and stirred at room temperature until mixed evenly, to obtain a scale inhibitor for phosphogypsum leachate in a reverse osmosis membrane system.

[0059] Example 4

[0060] The scale inhibitor described in this example is prepared according to the following order of steps:

[0061] S1, 2 parts by mass of dodecyl benzene sulfonic acid are mixed with 3 parts by mass of industrial ethanol, and stirred at room temperature until mixed evenly;

[0062] S2, 20 parts by mass of aluminum chloride are mixed with 70 parts by mass of water, and stirred at room temperature until the aluminum chloride is fully dissolved;

[0063] S3, the raw materials prepared in S1 are mixed with the raw materials prepared in S2, and stirred at room temperature until mixed evenly;

[0064] S4, the raw materials prepared in S3 are mixed with 5 parts by mass of ethylenediamine tetramethylene phosphonic acid, and stirred at room temperature until mixed evenly, to obtain a scale inhibitor for phosphogypsum leachate in a reverse osmosis membrane system.

[0065] To fully understand the actual effect of the scale inhibitor prepared in Examples 1-4 of the present application, the scaling material of the phosphogypsum leachate in the reverse osmosis membrane system of a certain company in Hubei Province is analyzed by phase analysis, scanning electron microscopy, and elemental analysis, and the analysis results are as follows:

[0066] Detection item Fluorine Silicon dioxide Potassium oxide Sulfate Calcium oxide Composition of phosphogypsum leachate on the components of reverse osmosis membrane foulant 36.44％ 15.65％ 23.15％ 22.13％ 12.71％

[0067] It is judged that the main scale is regular and coarse potassium / sodium fluosilicate scale and calcium sulfate scale, wherein the content of potassium / sodium fluosilicate scale is about 70%, and the content of calcium sulfate scale is about 30%.

[0068] The leachate before the phosphogypsum leachate of the company enters the reverse osmosis membrane system is taken back for scale inhibition experiment, and the experimental method for simulating the production of potassium / sodium fluosilicate scale in the reverse osmosis membrane system of the phosphogypsum leachate is as follows:

[0069] The 500g of the taken-back phosphogypsum leachate is transferred to four 500ml beakers, and the scale inhibitor is added in proportion and placed in a 50℃ constant temperature water bath for concentration to 200g. Among them, the scale inhibitor is added in the beaker in an amount of 60ppm, 100ppm, and 150ppm based on the amount of leachate, and a blank control is also carried out. The sum of the concentrations of K+ and Na+ in the solution before and after adding the scale inhibitor and the mass of the scale sample in the beaker after concentration of the leachate are measured, and the scale inhibition rates η1 and η2 are calculated by the following formula, respectively;

[0070]

[0071] C0——the total concentration of K+ and Na+ in the filtrate before concentration, mg / L;

[0072] C1——the total concentration of K+ and Na+ in the test group without scale inhibitor after concentration, mg / L;

[0073] C2——the total concentration of K+ and Na+ in the test group with scale inhibitor after concentration, mg / L.

[0074]

[0075] A0——the mass of scale sample in the test group without scale inhibitor after concentration, mg;

[0076] A1——the mass of scale sample in the test group with scale inhibitor after concentration, mg;

[0077] The experimental results of the scale inhibition effect of the scale inhibitors prepared in Examples 1-4 in phosphogypsum leachate are shown in Tables 1 and 2.

[0078] Table 1: Evaluation of scale inhibition performance of potassium / sodium fluosilicate in phosphogypsum leachate

[0079]

[0080] As shown in Table 1, when the dosage of the scale inhibitors prepared in Examples 1-4 is 60 ppm, the scale inhibition rate can reach more than 90%. When the dosage of the scale inhibitors of Example 1 and Example 4 is 100 ppm, the scale inhibition rate can reach more than 98%.

[0081] It is found through comparison that the scale inhibitors prepared in Example 1 and Example 4 have the best scale inhibition effect on potassium / sodium fluosilicate in phosphogypsum leachate, and the dosage is small, which is the optimal formula. It is suggested that 100 ppm can achieve excellent scale inhibition effect.

[0082] Table 2: Evaluation of scale inhibition performance of scale substance in phosphogypsum leachate

[0083]

[0084] As shown by the comparison of the scale inhibition effect in Table 2 and Table 1, the scale inhibition rate calculated by the mass of scale substance in phosphogypsum leachate is slightly lower than that calculated by the content of potassium / sodium fluosilicate, but the scale inhibition effect of Examples 1-4 is consistent. When the dosage of the scale inhibitors of Example 1 and Example 4 is 100 ppm, the scale inhibition rate can reach more than 95%, which is the optimal formula.

[0085] Comparative Example

[0086] The scale inhibition results of commonly used functional single-agent or compound scale inhibitors for preventing or reducing scaling of phosphogypsum leachate on reverse osmosis membrane systems are shown in Tables 3 and 4 below. The experimental methods for the comparative examples are the same as those in Examples 1-4.

[0087] Table 3: Evaluation of the scale inhibition performance of potassium / sodium fluorosilicate in phosphogypsum leachate

[0088]

[0089]

[0090] Table 4: Evaluation of the scale inhibition performance of scale in phosphogypsum leachate

[0091]

[0092]

[0093] As can be seen from Tables 3 and 4, single-agent organophosphonic acid scale inhibitors or compound scale inhibitors, which have excellent scale inhibition effects in traditional industrial cooling water systems, have poor effects in phosphogypsum leachate. This is because the scaling type of phosphogypsum leachate is mainly potassium / sodium fluorosilicate and the solution is strongly acidic, which are quite different from those in industrial cooling water systems, resulting in a significant change in the scale inhibition effect of the scale inhibitors.

[0094] Analysis of the test data in Tables 1, 2, 3, and 4 shows that the scale inhibitors in Examples 1-4, at the same dosage, exhibit significantly greater scale inhibition effects than the comparative scale inhibitors. Therefore, it can be determined that the scale inhibitor of this invention has a significantly superior scale inhibition effect compared to the comparative scale inhibitors.

[0095] The present invention provides a scale inhibitor that incorporates an aluminum compound, wherein the aluminum compound contains Al. 3+ It will react with silicon in a competitive manner with fluorine, from SiF6 2 Complex ions replace silicon to form acid-soluble AlF₂. x 3-x Complexing ions cause SiF6 in the phosphogypsum leachate to form complex ions. 2- Reduce or inhibit SiF6 2- This reduces or inhibits the formation of potassium / sodium fluorosilicate scale.

[0096] On the other hand, the synergistic surfactant dodecylbenzenesulfonic acid of the present invention increases the crystallization induction period and the limiting supersaturation of potassium fluorosilicate, thereby making it difficult for potassium fluorosilicate / sodium to form crystal nuclei in the solution, effectively alleviating the scaling of potassium fluorosilicate / sodium.

[0097] The organic phosphorus scale inhibitor in the traditional formula inhibits the normal growth of potassium / sodium fluosilicate crystal arranged by crystal lattice by the effect of crystal lattice distortion, so that the crystal is distorted and the growth is inhibited. The scale inhibitor of the application takes aluminum compound as the main component, and the synergistic effect of the organic phosphorus scale inhibitor and the surfactant strengthens the scale inhibition effect.

[0098] Compared with the prior art, the scale inhibitor of the application not only has a simple preparation method and stable performance, but also has high scale inhibition performance. The scale inhibitor can effectively prevent phosphogypsum leachate from scaling on the reverse osmosis membrane system, ensure the normal operation of the system, meet the market demand, and effectively solve the problem of insufficient scale inhibition effect of the prior art on the phosphogypsum leachate.

[0099] The beneficial effects of the application are:

[0100] 1. Compared with the traditional scale inhibitor, the scale inhibition rate of the scale inhibitor of the application in the phosphogypsum leachate reverse osmosis membrane system can reach more than 95%, and the scale inhibition effect is much higher than that of the traditional scale inhibitor.

[0101] 2. The scale inhibitor of the application can be used under high acidity conditions, and has excellent scale inhibition effect on various scales, especially potassium / sodium fluosilicate in the phosphogypsum leachate.

[0102] 3. Compared with the traditional scale inhibitor, the addition amount is small, and the use cost is low.

[0103] 4. The preparation method is simple, the performance is stable, the use is convenient, has no any influence on the subsequent section, and has good application prospect.

[0104] In order to verify the performance of the scale inhibitor of the application in effectively preventing the phosphogypsum leachate from scaling on the reverse osmosis membrane system, the scale inhibitor of the application is used in the phosphogypsum leachate reverse osmosis membrane reuse system of a company in Hubei, and the scale inhibition rate can reach more than 95%.

[0105] Finally, the method of the application is only a preferred embodiment, and is not used to limit the protection scope of the application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the application shall be included in the protection scope of the application.

Claims

1. A scale inhibitor for use in a reverse osmosis membrane system for phosphogypsum leachate, characterized in that, The scale inhibitor comprises the following raw materials in parts by weight: 2 parts by weight of dodecylbenzenesulfonic acid, 3 parts by weight of industrial ethanol, 20 parts by weight of aluminum sulfate, 70 parts by weight of water, and 5 parts by weight of polyaminopolyether methylenephosphonic acid.

2. A method for preparing the scale inhibitor of claim 1, characterized in that, Includes the following steps: S1, mix 2 parts by mass of dodecylbenzenesulfonic acid and 3 parts by mass of industrial ethanol, and stir evenly at room temperature; S2, mix 20 parts by weight of aluminum sulfate with 70 parts by weight of water, and stir at room temperature until the aluminum sulfate is fully dissolved; S3, mix the raw materials prepared in S1 with the raw materials prepared in S2, and stir evenly at room temperature; S4, the raw material obtained in S3 is mixed with 5 parts by mass of polyaminopolyether methylenephosphonic acid, and stirred and mixed evenly at room temperature to obtain a scale inhibitor for phosphogypsum filtrate in reverse osmosis membrane systems.

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