A scale inhibitor for high concentration iron ions, a preparation method thereof, and a scale inhibition rate detection method

Abstract

This invention discloses a scale inhibitor targeting high concentrations of iron ions, its preparation method, and a method for detecting the scale inhibition rate. The scale inhibitor, by mass percentage, is composed of the following components: 20-25% organic phosphorus mixture, 10-15% metal chelating agent, 1-2% catalyst, pH adjuster, and the balance being deionized water. This scale inhibitor effectively reduces the formation of iron scale in water bodies containing high concentrations of iron ions. The scale inhibition rate detection method of this invention allows for rapid testing of the scale inhibitor's performance against iron scale, providing accurate results, simplifying the testing process, and reducing testing costs.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, and in particular to a scale inhibitor for high concentrations of iron ions, its preparation method, and a method for detecting scale inhibition rate. Background Technology

[0002] With the development of reverse osmosis technology, more and more water samples with complex compositions are appearing. Some of these samples contain ferric and ferrous ions. Ferrous ions in the solution are easily oxidized to ferric ions, which in turn readily hydrolyze to form ferric hydroxide precipitate. In more complex water samples, other types of iron scale may also form. Currently, there are few scale inhibitors specifically designed for water samples with high concentrations of ferric ions, and there are few testing methods for the scale inhibition performance of these inhibitors against iron scale, making it impossible to systematically assess their scale inhibition performance against iron scale.

[0003] Chinese invention patent application with publication number CN116282597A and publication date June 23, 2023 discloses a reducing scale inhibitor and its preparation method. The reducing scale inhibitor has a certain scale inhibition effect on iron and manganese, but the scale inhibitor of this invention cannot achieve the expected effect on the treatment of water containing high concentrations of iron ions with iron ion concentrations of 10 mg / L and above.

[0004] Chinese invention patent application CN106669429A, published on May 17, 2017, discloses a phosphorus-free scale inhibitor for reverse osmosis membranes. This scale inhibitor contains a high-molecular-weight compound with large molecular chains. Due to electrostatic repulsion, solubilization, and lattice distortion, it exhibits good dispersibility and solubility for various inorganic and colloidal scales. It can disperse sparingly soluble salt particles into crystal centers, reducing or controlling the aggregation and scaling of sparingly soluble salts. Furthermore, it can cause lattice distortion in the deposited crystals, achieving the purpose of scale inhibition. It is used to prevent the deposition of calcium carbonate, silicate, sulfate, and phosphate scale. This scale inhibitor has a certain scale inhibition effect on water samples containing low concentrations of iron ions, but its scale inhibition effect is poor for water samples containing high concentrations of iron ions, failing to meet the requirements for water treatment.

[0005] Chinese invention patent application CN110526423A, published on December 3, 2019, discloses a phosphorus-free water treatment agent for high-concentration iron ion circulating water. The phosphorus-free scale inhibitor in this agent can adsorb onto inorganic scale crystals, causing crystal distortion or increasing the internal stress of large crystals, thus making the crystals more prone to breakage and hindering scale growth. Organic polymers can stabilize iron ions in circulating water, preventing iron ions from forming scale on equipment surfaces and causing under-scale corrosion. The iron ion complexing agent in the agent can complex free iron ions in circulating water, interfering with the reaction between Fe3+ and Fe, and reducing corrosion caused by iron ions. However, this scale inhibitor is less effective on water samples other than circulating water, and its scale inhibition effect decreases when the iron ion content in the water reaches 10 mg / L or higher. Summary of the Invention

[0006] The purpose of this invention is to provide a scale inhibitor for high concentrations of iron ions, its preparation method, and a method for detecting the scale inhibition rate. This scale inhibitor can effectively reduce the formation of iron scale in water bodies containing high concentrations of iron ions. The scale inhibition rate detection method of this invention can quickly complete the testing process of the scale inhibitor's scale inhibition performance against iron scale, and the test results are accurate. The test steps are simple and reduce the testing cost.

[0007] To address the problems existing in the prior art, the technical solution adopted in this invention is:

[0008] In a first aspect, the present invention provides a scale inhibitor for high concentrations of iron ions, which is prepared by mixing and reacting the following components by weight percentage:

[0009] The mixture consists of 20-25% organophosphorus compounds, 10-15% metal chelating agents, 1-2% catalysts, pH adjusters, and the remainder is deionized water.

[0010] Preferably, the scale inhibitor for high concentrations of iron ions comprises, by mass percentage: 20% organic phosphorus mixture, 12% metal chelating agent, 1% catalyst, 0.5% pH adjuster, and 66.5% deionized water.

[0011] Further, by mass percentage, the organophosphorus mixture comprises the following components: 50-60% 2-hydroxyphosphonoacetic acid and 40-50% polyaminopolyether methylenephosphonic acid; preferably 55% 2-hydroxyphosphonoacetic acid and 45% polyaminopolyether methylenephosphonic acid; this organophosphorus mixture, in synergy with metal chelating agents, can enhance scale inhibition against iron ions, conventional calcium carbonate, and calcium sulfate.

[0012] The metal chelating agent is composed of the following components: 60-70% deacetylated chitosan and 30-40% sodium gluconate; preferably 65% ​​deacetylated chitosan and 35% sodium gluconate. The synergistic effect of deacetylated chitosan and sodium gluconate can form a stable chelate with iron ions in water, enhancing the scale inhibition effect. Moreover, deacetylated chitosan is non-toxic and biodegradable, and its use in water will not cause secondary pollution.

[0013] The catalyst is sodium citrate, which can accelerate the reaction process.

[0014] The pH adjuster is ammonia.

[0015] The scale inhibitor of this invention, when formulated in a specific ratio, can effectively reduce the formation of iron-containing scale in water. If the metal chelating agent content is below 10%, the scale inhibition effect on iron ions will decrease significantly; if the metal chelating agent content is above 15%, the scale inhibition effect on iron ions will not be significantly improved, and the cost will increase significantly.

[0016] The metal chelating agent in this invention can form stable chelates with iron ions through the amino and hydroxyl groups in the molecule. The metal chelating agent can be compounded with organophosphorus mixtures, sodium citrate, ammonia water, and deionized water in a specific ratio to improve its scale inhibition effect on iron ions.

[0017] Secondly, the present invention provides a method for preparing the scale inhibitor described in the first aspect, comprising the following steps:

[0018] (1) Add deionized water to the reactor, turn on the stirring, and heat to 40-50℃;

[0019] This step requires heating to 40-50℃. If the temperature is below 40℃, the subsequent steps (2) and (3) will not be fully reacted and the reaction time will be too long. If the temperature is above 50℃, impurities will appear in the subsequent steps (2) and (3), affecting the scale inhibition effect of the scale inhibitor.

[0020] (2) Add the organophosphorus mixture and metal chelating agent, and stir for 3-4 hours at a speed of 60-80 rpm. This step allows the raw materials to be mixed evenly and the reaction to be complete. In this step, the organophosphorus mixture and metal chelating agent are used together to chelate with iron ions. At the same time, the organophosphorus mixture also has a certain scale inhibition effect on calcium carbonate and calcium sulfate, which can effectively reduce the formation of iron scale in water.

[0021] (3) Add the catalyst and stir for 1-2 hours at a speed of 100-120 rpm. This step allows the raw materials to be mixed evenly and the reaction to be complete.

[0022] (4) Cool to 20-25℃, add pH adjuster, stir at 100-120 rpm for 1-2 hours to obtain a brownish-yellow transparent liquid. This step can adjust the pH of the scale inhibitor to 3-4, reducing the impact of the agent on the system water.

[0023] Thirdly, the present invention provides the application of the scale inhibitor described in the first aspect above in reducing the formation of iron scale in water.

[0024] Furthermore, the amount of scale inhibitor added is 5-20 ppm, preferably 20 ppm.

[0025] Fourthly, the present invention provides a method for detecting the scale inhibition rate of the scale inhibitor described in the first aspect above, comprising the following steps:

[0026] (1) Take several clean experimental containers and label them accordingly;

[0027] (2) Use a pipette to transfer ferrous sulfate solution into the experimental container;

[0028] (3) Measure out the scale inhibitors and add them to the experimental containers in sequence;

[0029] (4) Use a pipette to transfer borax solution into the experimental container, and then add deionized water until the volume of the solution in the experimental container is 100 ml. Adding borax in this step can accelerate the conversion of ferrous ions to ferric ions in the solution. This is because borax solution can combine with ferric ions to form ferric ion complexes, which promote the contact between ferrous ions and oxygen to be oxidized into ferric ions.

[0030] (5) At the same time, seal all experimental containers and keep them at a constant temperature in a water bath. The water bath temperature is 30-35℃ and the water bath time is 22-24h.

[0031] (6) Remove the experimental container and cool it to room temperature, then filter the solution into beakers;

[0032] (7) Detect the iron ion concentration in the filtrate, repeat the measurement three times, and take the average value;

[0033] (8) The scale inhibition performance of the scale inhibitor is analyzed based on the values ​​measured above.

[0034] Preferably, the number of experimental containers is 5.

[0035] Furthermore, the amount of ferrous sulfate used is 3.53 ml to 7.07 ml, and the concentration of the ferrous sulfate solution is 0.1 to 0.2 mol / L.

[0036] Preferably, the amount of scale inhibitor added in the five experimental containers is 0, 5, 10, 15, and 20 ppm, respectively.

[0037] Furthermore, the amount of borax solution used is 10-15 ml, and the concentration of borax solution is 3.8-4.0 g / L.

[0038] The advantages and beneficial effects of this invention are:

[0039] This invention provides a scale inhibitor for high concentrations of iron ions, which can effectively reduce the formation of iron scale in water bodies containing high concentrations of iron ions. The scale inhibition rate testing method of this invention can quickly complete the testing process of the scale inhibitor's scale inhibition performance against iron scale, and the test results are accurate. The testing steps are simple and reduce testing costs. Detailed Implementation

[0040] The technical solutions in the embodiments of this application are clearly described below. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0041] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0042] Example 1

[0043] This embodiment provides a scale inhibitor for high concentrations of iron ions, which, by mass percentage, consists of: 20% organic phosphorus mixture, 12% metal chelating agent, 1% sodium citrate, 0.5% ammonia, and 66.5% deionized water.

[0044] In this embodiment, the organophosphorus mixture, by mass percentage, consists of: 55% 2-hydroxyphosphonoacetic acid and 45% polyaminopolyether methylenephosphonic acid.

[0045] The metal chelating agent, by mass percentage, consists of: 65% deacetylated chitosan and 35% sodium gluconate.

[0046] This embodiment describes a method for preparing a scale inhibitor targeting high concentrations of iron ions, comprising the following steps:

[0047] a. Add 66.5 kg of deionized water to the reactor, start stirring, and heat to 45°C.

[0048] b. Add 20 kg of organophosphorus mixture and 12 kg of metal chelating agent, stir at 70 rpm for 3 hours.

[0049] c. Add 1 kg of sodium citrate, stir at 110 rpm for 1 hour.

[0050] d. Cool to 25℃, add 0.5kg of ammonia water, stir at 110 rpm for 1 hour to obtain a brownish-yellow transparent liquid.

[0051] This embodiment describes a scale inhibitor for high concentrations of iron ions, which is added at a dosage of 5-20 ppm when used to reduce the formation of iron scale in water.

[0052] Example 2

[0053] This embodiment provides a scale inhibitor for high concentrations of iron ions. The only difference between this embodiment and Embodiment 1 is that, by mass percentage, its components are: 25% organic phosphorus mixture, 10% metal chelating agent, 1% sodium citrate, 0.5% ammonia, and 63.5% deionized water. All other components are the same as in Embodiment 1.

[0054] Example 3

[0055] This embodiment provides a scale inhibitor for high concentrations of iron ions. The only difference between this embodiment and Embodiment 1 is that, by mass percentage, its components are: 22% organic phosphorus mixture, 15% metal chelating agent, 1% sodium citrate, 0.5% ammonia, and 61.5% deionized water. All other components are the same as in Embodiment 1.

[0056] Example 4

[0057] This embodiment provides a scale inhibitor for high concentrations of iron ions. The only difference between this embodiment and Example 1 is that the organic phosphorus mixture, by mass percentage, consists of 50% 2-hydroxyphosphonoacetic acid and 50% polyaminopolyether methylenephosphonic acid, while the rest are the same as in Example 1.

[0058] Example 5

[0059] This embodiment provides a scale inhibitor for high concentrations of iron ions. The only difference between this embodiment and Example 1 is that the organic phosphorus mixture, by mass percentage, consists of 60% 2-hydroxyphosphonoacetic acid and 40% polyaminopolyether methylenephosphonic acid, with the rest being the same as in Example 1.

[0060] Example 6

[0061] This embodiment provides a scale inhibitor for high concentrations of iron ions. The only difference between this embodiment and Embodiment 1 is that the metal chelating agent, by mass percentage, consists of: 60% deacetylated chitosan and 40% sodium gluconate. All other components are the same as in Embodiment 1.

[0062] Example 7

[0063] This embodiment provides a scale inhibitor for high concentrations of iron ions. The only difference between this embodiment and Embodiment 1 is that the metal chelating agent, by mass percentage, consists of: 70% deacetylated chitosan and 30% sodium gluconate. All other components are the same as in Embodiment 1.

[0064] Comparative Example 1

[0065] This comparative example provides a scale inhibitor for high concentrations of iron ions. The only difference between this comparative example and Example 1 is that carboxymethyl cellulose is used instead of deacetylated chitosan. All other aspects are the same as in Example 1.

[0066] Comparative Example 2

[0067] This comparative example provides a scale inhibitor for high concentrations of iron ions. The only difference between this comparative example and Example 1 is that, by mass percentage, its components are: 30% organic phosphorus mixture, 2% metal chelating agent, 1% sodium citrate, 0.5% ammonia, and 66.5% deionized water. All other components are the same as in Example 1.

[0068] Comparative Example 3

[0069] This comparative example provides a scale inhibitor for high concentrations of iron ions, which, by mass percentage, consists of: 32% organophosphorus mixture, 1% sodium citrate, 0.5% ammonia, and 66.5% deionized water. The remaining components are the same as in Example 1.

[0070] Comparative Example 4

[0071] This comparative example provides a scale inhibitor for high concentrations of iron ions, which, by mass percentage, consists of: 32% metal chelating agent, 1% sodium citrate, 0.5% ammonia, and 66.5% deionized water. The remaining components are the same as in Example 1.

[0072] Example 8

[0073] This embodiment provides a method for testing the scale inhibition performance of a scale inhibitor against iron scale, including the following steps:

[0074] (1) Take 5 clean conical flasks and label them accordingly;

[0075] (2) Use a pipette to transfer 3.53 ml of ferrous sulfate solution into each conical flask. The concentration of the ferrous sulfate solution is 0.1 mol / L.

[0076] (3) Measure out the scale inhibitor prepared in Example 1 and add it to five conical flasks in sequence at concentrations of 0, 5, 10, 15 and 20 ppm respectively;

[0077] (4) Use a pipette to transfer 15 ml of borax solution into each of the five conical flasks, and then add deionized water until the total volume of the solution is 100 ml. The concentration of the borax solution is 3.8 g / L.

[0078] (5) Seal all the conical flasks and keep them in a water bath at a constant temperature of 35°C for 24 hours.

[0079] (6) Remove the conical flask and cool it to room temperature, then filter the solution into beakers;

[0080] (7) The iron ion concentration in the filtrate of the first conical flask without scale inhibitor and after 24 hours and the second to fourth conical flasks with scale inhibitor and after 24 hours were measured three times, and the values ​​were 0 / 0 / 0, 9.4 / 9.5 / 9.6, 10 / 10 / 10, 10 / 10 / 10, and 10 / 10 / 10. The average values ​​were 0, 9.5, 10, 10, and 10, respectively.

[0081] (8) Calculate the scale inhibition rate of the scale inhibitor:

[0082] The formula for calculating the scale inhibition rate is: (Iron ion content in the solution after adding scale inhibitor and standing for 24 hours - Iron ion content in the solution after not adding scale inhibitor and standing for 24 hours) / (Iron ion content in the solution after adding scale inhibitor - Iron ion content in the solution after not adding scale inhibitor and standing for 24 hours) * 100%.

[0083] That is, when the amount of scale inhibitor prepared in Example 1 is 0 ppm, the scale inhibition rate = 0-0 / 10-0*100% = 0.

[0084] When the scale inhibitor prepared in Example 1 is added at a dosage of 5 ppm, the scale inhibition rate is 9.5-0 / 10-0*100%=95%.

[0085] When the scale inhibitor prepared in Example 1 is added at a concentration of 10 ppm, the scale inhibition rate = 10-0 / 10-0*100% = 100%.

[0086] When the scale inhibitor prepared in Example 1 is added at a concentration of 15 ppm, the scale inhibition rate = 10-0 / 10-0*100% = 100%.

[0087] When the scale inhibitor prepared in Example 1 is added at a dosage of 20 ppm, the scale inhibition rate = 10-0 / 10-0*100% = 100%.

[0088] In this test method, the active ingredient in the scale inhibitor undergoes a chelation reaction with iron ions in the water, forming a stable chelate that prevents the precipitation of iron ions as scale. The higher the iron ion content in the solution, the better the scale inhibition effect.

[0089] Example 9

[0090] This embodiment provides a method for testing the scale inhibition performance of a scale inhibitor against iron scale. The only difference between this embodiment and Embodiment 8 is that in step (2), 7.07 ml of ferrous sulfate solution is transferred to each conical flask using a pipette and added to each flask. The concentration of the ferrous sulfate solution is 0.1 mol / L. The rest is the same as in Embodiment 8. The iron ion concentration in the filtrate of the five conical flasks is measured three times, and the values ​​are 0 / 0 / 0, 8.7 / 8.8 / 8.9, 9.6 / 9.7 / 9.5, 10 / 10 / 10, and 10 / 10 / 10, respectively. The average values ​​are 0, 8.8, 9.6, 10, and 10, respectively.

[0091] (8) Calculate the scale inhibition rate of the scale inhibitor:

[0092] The formula for calculating the scale inhibition rate is: (Iron ion content in the solution after adding scale inhibitor and standing for 24 hours - Iron ion content in the solution after not adding scale inhibitor and standing for 24 hours) / (Iron ion content in the solution after adding scale inhibitor - Iron ion content in the solution after not adding scale inhibitor and standing for 24 hours) * 100%.

[0093] That is, when the amount of scale inhibitor prepared in Example 1 is 0 ppm, the scale inhibition rate = 0-0 / 10-0*100% = 0.

[0094] When the scale inhibitor prepared in Example 1 is added at a dosage of 5 ppm, the scale inhibition rate is 8.8-0 / 10-0*100%=88%.

[0095] When the scale inhibitor prepared in Example 1 is added at a concentration of 10 ppm, the scale inhibition rate is 9.6-0 / 10-0*100%= 96%.

[0096] When the scale inhibitor prepared in Example 1 is added at a concentration of 15 ppm, the scale inhibition rate = 10-0 / 10-0*100% = 100%.

[0097] When the scale inhibitor prepared in Example 1 is added at a dosage of 20 ppm, the scale inhibition rate = 10-0 / 10-0*100% = 100%.

[0098] In this test method, the active ingredient in the scale inhibitor undergoes a chelation reaction with iron ions in the water, forming a stable chelate that prevents the precipitation of iron ions as scale. The higher the iron ion content in the solution, the better the scale inhibition effect.

[0099] Experimental Example 1

[0100] Following the methods described in Examples 8 and 9, the scale inhibition performance of the organophosphorus mixture and metal chelating agent described in Example 1, as well as the scale inhibitors described in Examples 1-7, Publication Nos. CN116282597A, CN106669429A, CN110526423A, and Comparative Examples 1-4, was tested. The scale inhibition test results are shown in Tables 1 and 2.

[0101] Table 1: Scale inhibition rate of scale inhibitors in each group when the iron ion content in the solution is 10 ppm.

[0102]

[0103] As shown in Table 1, when the iron ion content in the solution is 10 ppm and the amount of scale inhibitor added is 5-20 ppm, the scale inhibition rate of Examples 1-7 reaches 91-100%, which is significantly better than other groups. Among them, Example 1 has the best effect, with a scale inhibition rate of 95-100%, especially when the amount of scale inhibitor added in Example 1 is 10-20 ppm, the scale inhibition rate can reach 100%.

[0104] Table 2: Scale inhibition rate of scale inhibitors in each group when the iron ion content in the solution is 20 ppm.

[0105]

[0106] As shown in Table 2, when the iron ion content in the solution is 20 ppm and the amount of scale inhibitor added is 5-20 ppm, the scale inhibition rate of Examples 1-7 reaches 84-100%, which is significantly better than other groups. Among them, Example 1 has the best effect, with a scale inhibition rate of 88-100%, especially when the amount of scale inhibitor added in Example 1 is 15-20 ppm, the scale inhibition rate can reach 100%.

[0107] As can be seen from Tables 1 and 2, using only a single organophosphorus mixture or metal chelating agent as a scale inhibitor results in a poor scale inhibition rate because no synergistic effect can be achieved.

[0108] Comparative Example 1 uses carboxymethyl cellulose instead of deacetylated chitosan. Because the carboxyl and hydroxyl groups in carboxymethyl cellulose are more likely to bind to themselves, only a small portion can form complexes with iron ions in water, thus resulting in a significant decrease in its scale inhibition efficiency.

[0109] Comparative Example 2 showed a decrease in scale inhibition rate due to excessively high content of organophosphorus mixture and excessively low content of metal chelating agent.

[0110] In Comparative Example 3, the lack of a metal chelating agent resulted in the disappearance of the synergistic effect, leading to a significant decrease in scale inhibition rate.

[0111] In Comparative Example 4, the lack of an organophosphorus mixture resulted in the disappearance of the synergistic effect, leading to a significant decrease in scale inhibition rate.

[0112] The embodiments of this application have been described above, but this application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

Claims

1. A scale inhibitor targeting high concentrations of iron ions, wherein high concentration of iron ions refers to an iron ion content in water ≥10 mg / L, characterized in that, It is composed of the following components reacted together, by mass percentage: The composition consists of 20-25% organophosphorus compound, 10-15% metal chelating agent, 1-2% catalyst, pH adjuster, and the remainder is deionized water. The organophosphorus mixture comprises, by weight percentage: 50-60% 2-hydroxyphosphonoacetic acid and 40-50% polyaminopolyether methylenephosphonic acid; The metal chelating agent is composed of the following components: 60-70% deacetylated chitin and 30-40% sodium gluconate; The catalyst is sodium citrate; The pH adjuster is ammonia.

2. The method for preparing a scale inhibitor targeting high concentrations of iron ions as described in claim 1, characterized in that, Includes the following steps: (1) Add deionized water to the reactor, stir, and heat to 40-50℃; (2) Add the organophosphorus mixture and metal chelating agent, and stir for 3-4 hours at a speed of 60-80 rpm; (3) Add the catalyst and stir for 1-2 hours at a speed of 100-120 rpm. (4) Cool down to 20-25℃, add pH adjuster, stir at 100-120 rpm for 1-2 hours to obtain brownish-yellow transparent liquid.

3. The application of the scale inhibitor for high concentrations of iron ions as described in claim 1 in reducing the formation of iron scale in water.

4. The application according to claim 3, characterized in that, The scale inhibitor is added at a rate of 5-20 ppm.

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