Alkaline environment-friendly membrane cleaning agent for calcium sulfate composite scale sample and preparation method of alkaline environment-friendly membrane cleaning agent

Abstract

The invention provides an alkaline environment-friendly membrane cleaning agent for a calcium sulfate composite scale sample, which is characterized by comprising the following components in percentage by mass: 0.01-0.02% of a pH regulator, 0.1-0.5% of a surfactant, 10-25% of a chelating agent, 0.1-0.5% of an alkaline builder and the balance of deionized water. The cleaning agent is easy to prepare, low in cost, high in normal-temperature dissolution rate and easy and convenient to use and operate, waste liquid can be safely discharged and is non-toxic and harmless, the service life of the membrane can be prolonged, environmental pollution can be reduced, and the cleaning agent is particularly suitable for cleaning various reverse osmosis and nanofiltration membranes.

Description

Technical Field

[0001] The invention relates to the field of reverse osmosis membrane water treatment technology, and in particular to an alkaline environmentally friendly membrane cleaning agent for calcium sulfate composite scale and a preparation method thereof. Background Art

[0002] Reverse osmosis (RO) is a membrane separation technology that uses pressure difference to separate solvent from solution. It has the advantages of low energy consumption, low cost, simple operation and high efficiency. It is widely used in seawater desalination, industrial wastewater treatment and other fields. However, membrane contamination can lead to membrane exhaustion, causing the pressure difference of membrane elements to increase during operation, the desalination rate and flow rate to decrease, and even fail to work normally. The main pollutants include carbonate, sulfate and silicate scales. The selection of cleaning agents and cleaning methods is crucial to restore membrane performance and extend service life. Among them, complex scales such as calcium sulfate are hard and difficult to remove. The traditional sodium hydroxide cleaning method is time-consuming and labor-intensive, and it is still a major problem for descaling.

[0003] A Chinese patent application document (CN117205756A) discloses a membrane cleaning agent for treating calcium sulfate scale, which is specially used to remove insoluble calcium sulfate scale. The agent is a neutral solution, which can thoroughly remove calcium sulfate scale without corroding membrane elements, is non-toxic and harmless to the human body, and the waste liquid can be safely discharged. It is efficient and safe, and does not produce hydrogen embrittlement. However, the cleaning agent cannot achieve the best effect on complex scale samples, and the cleaning agent formula takes a long time to dissolve, and requires auxiliary agents to dissolve, which has a low cost-effectiveness.

[0004] A composite scale inhibitor and descaling agent is disclosed in a Chinese patent application document (CN116947225A), which can effectively remove common scale components such as calcium carbonate, calcium sulfate and ferric oxide through the synergistic effect of chelating ions and auxiliary agents, and can also remove barium strontium scale pollution, with good descaling effect. After experiments, the descaling rate is greater than ≥96%, and the descaling efficiency is high, non-corrosive, and operating costs are saved. It is suitable for circulating cooling water systems in various situations. Although the descaling agent has a certain cleaning effect on complex scale samples, it has the inconvenience of long soaking time and an operating temperature of 50°C to 90°C, and the descaling agent cannot meet the cleaning conditions of different workshops.

[0005] A Chinese patent application document (CN101757858A) discloses a composite cleaning agent for cleaning organic dirt in a membrane system. The cleaning agent removes organic pollution to the membrane system through multiple actions, and can achieve good decontamination effect; it can simultaneously solve the damage of multiple types of pollutants such as inorganic salts and metal oxides to the membrane system, and has a wide range of efficacy; it can replace multiple agents for joint use, and is easy to operate. However, when the cleaning agent is used for calcium sulfate, in order to achieve the effect, the cleaning agent consumption is relatively large.

[0006] A Chinese patent application document (CN102527244A) discloses a method for cleaning a reverse osmosis membrane, which uses an acidic cleaning agent and an alkaline cleaning agent for cleaning. The method requires taking the membrane element out of the water tank and rinsing the residual cleaning agent with clean water, and then placing the membrane element into a reverse osmosis membrane offline cleaning device. The cleaning agent in this solution cannot achieve a good removal effect on calcium sulfate scale samples, and the cleaning operation is cumbersome.

[0007] Therefore, for the complex scale samples generated in the reverse osmosis membrane, especially those containing calcium sulfate, there is a need for a reverse osmosis membrane cleaning agent that is more convenient to use, has a good cleaning effect, and does not cause pollution problems. Summary of the invention

[0008] In order to solve the above problems, the present invention aims to provide an alkaline environmentally friendly membrane cleaning agent for calcium sulfate composite scale and a preparation method thereof.

[0009] To achieve the above object, the present invention adopts the following technical solution:

[0010] The invention provides an alkaline environmentally friendly membrane cleaning agent for calcium sulfate composite scale, characterized in that, in terms of mass percentage, its components include: 0.01% to 0.02% pH regulator, 0.1% to 0.5% surfactant, 10% to 25% chelating agent, 0.1% to 0.5% alkaline builder, and the balance deionized water.

[0011] Furthermore, the alkaline environmentally friendly membrane cleaning agent for calcium sulfate composite scale provided by the present invention may also have the following characteristics: wherein the surfactant is one or more of sodium dodecyl sulfonate, sodium dodecylbenzene sulfonate, and sodium dodecyl sulfate.

[0012] Furthermore, the alkaline environmentally friendly membrane cleaning agent for calcium sulfate composite scale provided by the present invention may also have the following characteristics: wherein the chelating agent is one or more of disodium salt of ethylenediaminetetraacetic acid, tetrasodium salt of ethylenediaminetetraacetic acid, ethylenediaminetetraacetic acid, dipotassium salt of ethylenediaminetetraacetic acid, and dipotassium salt of ethylene glycol diethyl ether diaminetetraacetic acid.

[0013] Furthermore, the alkaline environmentally friendly membrane cleaning agent for calcium sulfate composite scale provided by the present invention may also have the following characteristics: wherein the pH adjusting agent is selected from sodium hydroxide or potassium hydroxide.

[0014] Furthermore, the alkaline environmentally friendly membrane cleaning agent for calcium sulfate composite scale provided by the present invention may also have the following characteristics: wherein the pH adjusting agent adjusts the pH value to 11.0-12.0.

[0015] Furthermore, the alkaline environmentally friendly membrane cleaning agent for calcium sulfate composite scale provided by the present invention may also have the following characteristics: wherein the alkaline builder is one or more of sodium bicarbonate, ammonium citrate, sodium carbonate, and sodium acetate.

[0016] The present invention also provides a method for preparing the above-mentioned alkaline environmentally friendly membrane cleaning agent for calcium sulfate composite scale, which is characterized in that it includes the following steps: weighing a pH regulator, a surfactant, a chelating agent, an alkaline builder and deionized water; then, adding the weighed pH regulator, surfactant, chelating agent, and alkaline builder into the deionized water in sequence and stirring, the stirring speed is controlled at 60r / min, stirring for 1 hour, until the materials are completely dissolved, and the membrane cleaning agent is prepared.

[0017] Functions and effects of the present invention:

[0018] The alkaline environmentally friendly membrane cleaning agent for calcium sulfate composite scale of the present invention includes a pH regulator, a surfactant, a chelating agent and an alkaline detergent. The cleaning agent components can safely and quickly remove the calcium sulfate scale on the membrane surface by dispersion, chelation and the like, and effectively soften the calcium sulfate crystals to avoid scratching the membrane material, thereby solving the pollution problem of the reverse osmosis system, and can clean the system scaling, microbial contamination and organic matter attachment, improve the desalination rate of the reverse osmosis membrane, thereby improving the system performance, extending the service life of the membrane, and reducing the production cost. The cleaning efficiency can reach 96% to 100%. In addition, the cleaning agent is non-toxic, harmless to the human body, does not contain phosphorus, has complete biodegradability, and direct discharge has no impact on the environment. In addition, according to actual needs, the cleaning can be carried out by pausing the equipment or without stopping the equipment. The cleaning agent can react spontaneously at room temperature without heating, and can remove more than 98% of calcium sulfate and composite scale at one time in a short time, saving time and effort. The cleaning agent is simple to prepare, low in cost, has a fast dissolution rate at room temperature, is easy to use and operate, and the waste liquid can be safely discharged and is non-toxic and harmless. It can increase production, extend the service life of the membrane, and reduce environmental pollution. It is particularly suitable for cleaning various reverse osmosis and nanofiltration membranes, especially in the application scenarios of zero-discharge wastewater treatment, and has broad practical value. DETAILED DESCRIPTION

[0019] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the following embodiments specifically illustrate the technical solutions of the present invention.

[0020] <Example 1>

[0021] This embodiment prepares an alkaline environmentally friendly membrane cleaning agent for calcium sulfate composite scale.

[0022] 1) The pH of the prepared alkaline environmentally friendly cleaning agent is 11, and the mass percentage of each component is as follows:

[0023] 0.01% pH adjuster: potassium hydroxide.

[0024] 0.1% Surfactant: Sodium dodecyl sulfate.

[0025] 10% Chelating agent: 1% EDTA disodium salt, 8% EDTA tetrasodium salt, 1% EDTA.

[0026] 0.5% alkaline builder: 0.45% sodium carbonate, 0.05% sodium acetate.

[0027] The balance is deionized water.

[0028] 2) Add surfactant, chelating agent and alkaline detergent to deionized water in sequence, dissolve at room temperature, stir with magnetic rotor, control the stirring speed at 60r / min, stir for 1h, and prepare 100ml cleaning agent for standby use.

[0029] <Example 2>

[0030] This embodiment prepares an alkaline environmentally friendly membrane cleaning agent for calcium sulfate composite scale.

[0031] 1) The pH of the prepared alkaline environmentally friendly cleaning agent is 12, and the mass percentage of each component is as follows:

[0032] 0.01% pH adjuster: sodium hydroxide.

[0033] 0.5% surfactant: 0.2% sodium dodecyl sulfonate, 0.2% sodium dodecylbenzene sulfonate, 0.1% sodium dodecyl sulfate.

[0034] 25% chelating agent: 10% disodium ethylenediaminetetraacetic acid, 10% tetrasodium ethylenediaminetetraacetic acid, 0.5% ethylenediaminetetraacetic acid, 4% dipotassium ethylenediaminetetraacetic acid, 0.5% dipotassium ethylenediaminetetraacetic acid.

[0035] 0.2% alkaline builder: 0.04% sodium bicarbonate, 0.02% ammonium citrate, 0.1% sodium carbonate, 0.04% sodium acetate.

[0036] The balance is deionized water.

[0037] 2) Add surfactant, chelating agent and alkaline detergent to deionized water in sequence, dissolve at room temperature, stir with magnetic rotor, control the stirring speed at 60r / min, stir for 1h, and prepare 100ml cleaning agent for standby use.

[0038] <Example 3>

[0039] This embodiment prepares an alkaline environmentally friendly membrane cleaning agent for calcium sulfate composite scale.

[0040] 1) The pH of the prepared alkaline environmentally friendly cleaning agent is 12, and the mass percentage of each component is as follows:

[0041] 0.02% pH adjuster: sodium hydroxide.

[0042] 0.1% Surfactant: Sodium dodecylbenzene sulfonate

[0043] 15% Chelating agent: 10% EDTA tetrasodium salt, 0.5% EDTA, 4.5% EDTA dipotassium salt.

[0044] 0.2% alkaline builder: 0.1% sodium bicarbonate, 0.1% ammonium citrate.

[0045] The balance is deionized water.

[0046] (2) Add surfactant, chelating agent and alkaline detergent to deionized water in sequence, dissolve at room temperature, stir with magnetic rotor at a speed of 60 r / min, stir for 1 hour, and prepare 100 ml of cleaning agent for standby use.

[0047] <Example 4>

[0048] This embodiment prepares an alkaline environmentally friendly membrane cleaning agent for calcium sulfate composite scale.

[0049] 1) The pH of the prepared alkaline environmentally friendly cleaning agent is 11.5, and the mass percentage of each component is as follows:

[0050] 0.01% pH adjuster: potassium hydroxide.

[0051] 0.1% Surfactant: Sodium dodecylbenzene sulfonate.

[0052] 20% Chelating agent: 10% EDTA disodium salt, 10% EDTA tetrasodium salt.

[0053] 0.2% alkaline builder: sodium carbonate.

[0054] The balance is deionized water.

[0055] 2) Add surfactant, chelating agent and alkaline detergent to deionized water in sequence, dissolve at room temperature, stir with magnetic rotor, control the stirring speed at 60r / min, stir for 1h, and prepare 100ml cleaning agent for standby use.

[0056] <Comparative Example 1>

[0057] Comparative Example 1 A cleaning agent was prepared according to the scheme described in Chinese patent application document CN117205756A.

[0058] 1) Add 40 g of deionized water into a reactor, turn on the stirrer, add 30 g of main detergent sodium acetate and 25 g of builder sodium citrate while stirring, and continue stirring for 30 min;

[0059] Add 10 g of hexamethylenetetramine as a buffer and continue stirring for 60 min;

[0060] Add 10 g of the penetrant alkyl alcohol polyoxyethyl ether and continue stirring for 60 min until the solution becomes clear and bright.

[0061] 2) Take 100 ml for later use.

[0062] <Comparative Example 2>

[0063] Comparative Example 2: A cleaning agent was prepared according to the scheme described in Chinese patent application document CN116947225A.

[0064] 1) 9.5% of ethylenediaminetetraacetic acid, 15.2% of diethylenetriaminepentaacetic acid, 4% of sodium humate, 2.5% of citric acid, 0.5% of triethanolamine, 1.0% of alkylphenol polyoxyethylene ether (TX-10) and 1.1% of itaconic acid / 2-acrylamide-2-methylpropanesulfonic acid / sodium allylsulfonate terpolymer (the monomer molar ratio of itaconic acid, 2-acrylamide-2-methylpropanesulfonic acid and sodium allylsulfonate is 2.2:1:1.7), the balance is water, and the pH value is 6.8.

[0065] 2) Prepare 100 ml solution for later use.

[0066] <Comparative Example 3>

[0067] Comparative Example 3: A cleaning agent was prepared according to the scheme described in Chinese patent application document CN101757858A.

[0068] 1) The cleaning membrane system used contains a composite cleaning agent for organic dirt, which is prepared from sodium bicarbonate, EDTA-4Na, ammonium citrate, sodium dodecylbenzene sulfonate and pure water in mass ratios of 15%, 25%, 15%, 1% and 44% respectively to form a chemical solution at room temperature.

[0069] 2) Prepare 100 ml and set aside.

[0070] <Comparative Example 4>

[0071] Comparative Example 4: A cleaning agent was prepared according to the scheme described in Chinese patent application document CN102527244A.

[0072] 1) This type of cleaning agent contains alkali, surfactant, chelating agent, salt, alcohol and water; the alkali in the cleaning agent is sodium hydroxide, and the pH value is adjusted to 12 using sodium hydroxide; the surfactant is sodium dodecylbenzene sulfonate, and its mass concentration is 0.1%; the chelating agent is tetrasodium EDTA, and its mass concentration is 2.0%; the mass concentration of sodium chloride is 3%; the mass concentration of ethylene glycol is 0.5%; the solvent water used to prepare the cleaning agent is selected from the water produced by the reverse osmosis system.

[0073] 2) Prepare 100 ml of cleaning agent and set aside.

[0074] Experiment to verify the effect of dissolving calcium sulfate:

[0075] Experiments were conducted with Example 1, Example 2, Example 3, Example 4, Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4, and a commercially available calcium sulfate cleaning agent 1, a commercially available calcium sulfate cleaning agent 2, a commercially available calcium sulfate cleaning agent 3, and a commercially available calcium sulfate cleaning agent 4 according to the following steps:

[0076] (1) Place a clean three-necked flask in a heat-collecting magnetic stirrer and connect the condenser and thermometer.

[0077] (2) Take 100 mL of each of the above cleaning agents and another 100 mL of deionized water as a blank.

[0078] (3) Pour the test samples into three-necked flasks and plug them with rubber stoppers. Use a balance to accurately weigh about 1g of analytically pure calcium sulfate crystals, recorded as M1. When the liquid in the three-necked flask is constant at 25°C, pour the calcium sulfate crystals in, stir and dissolve at a constant temperature, and keep the water body slowly stirred. After 8 hours, pour the mixture in the three-necked flask into a funnel for filtration. After thorough filtration, place the filter cake in a vacuum drying oven for drying, take it out and cool it, weigh it as M2, and calculate the scale removal rate and the blank self-dissolution rate a. The calculation formula for the scale removal rate is as follows:

[0079]

[0080] The experimental results are shown in Table 1 below:

[0081] Table 1. Calcium sulfate dissolution performance test table

[0082] Test item name Initial scale sample (g) 8h residual scale sample (g) 8h scale removal rate (%) Example 1 1.01 0.03 96.7 Example 2 1.02 0 100 Example 3 1.01 0.01 99.2 Example 4 1.03 0 100 Comparative Example 1 1.01 0.15 79.4 Comparative Example 2 1.02 0.14 80.8 Comparative Example 3 1.01 0.18 75.5 Comparative Example 4 1.03 0.14 80.6 Commercial cleaning agent 1 1.01 0.46 37.1 Commercial cleaning agent 2 1.01 0.42 42.2 Commercial cleaning agent 3 1.02 0.50 31.4 Commercial cleaning agent 4 1.01 0.59 19.2

[0083] As shown in Table 1, compared with the comparative alkaline cleaning agent and the commercial calcium sulfate cleaning agent, the cleaning agent in this case has a better dissolving effect on calcium sulfate. In addition, under the same experimental conditions, the scale removal efficiency of the cleaning agent is more than twice that of the commercial cleaning agent, which greatly improves the efficiency of on-site cleaning.

[0084] The above are only preferred embodiments of the present invention and are not intended to limit the present invention in any form. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present invention fall within the protection scope of the present invention.

Claims

1. An alkaline environmentally friendly membrane cleaning agent for calcium sulfate composite scale, characterized in that: The components include, by mass percentage, 0.01% to 0.02% of a pH regulator, 0.1% to 0.5% of a surfactant, 10% to 25% of a chelating agent, 0.1% to 0.5% of an alkaline detergent, and the balance of deionized water.

2. The alkaline environmentally friendly membrane cleaning agent for calcium sulfate composite scale as claimed in claim 1, characterized in that: in, The surfactant is one or more of sodium dodecyl sulfonate, sodium dodecylbenzene sulfonate and sodium dodecyl sulfate.

3. The alkaline environmentally friendly membrane cleaning agent for calcium sulfate composite scale as claimed in claim 1, characterized in that: in, The chelating agent is one or more of ethylenediaminetetraacetic acid disodium salt, ethylenediaminetetraacetic acid tetrasodium salt, ethylenediaminetetraacetic acid, ethylenediaminetetraacetic acid dipotassium salt, and ethylene glycol diethyl ether diaminetetraacetic acid dipotassium salt.

4. The alkaline environmentally friendly membrane cleaning agent for calcium sulfate composite scale as claimed in claim 1, characterized in that: in, The pH adjuster is selected from sodium hydroxide or potassium hydroxide.

5. The alkaline environmentally friendly membrane cleaning agent for calcium sulfate composite scale as claimed in claim 4, characterized in that: in, The pH adjuster adjusts the pH value to 11.0-12.

0.

6. The alkaline environmentally friendly membrane cleaning agent for calcium sulfate composite scale as claimed in claim 1, characterized in that: in, The alkaline builder is one or more of sodium bicarbonate, ammonium citrate, sodium carbonate and sodium acetate.

7. A method for preparing an alkaline environmentally friendly membrane cleaning agent for calcium sulfate composite scale as claimed in any one of claims 1 to 6, characterized in that: The following steps are involved: Weighing the pH regulator, the surfactant, the chelating agent, the alkaline builder and the deionized water; The weighed pH regulator, the surfactant, the chelating agent, and the alkaline builder are sequentially added into the deionized water and stirred at a stirring speed of 60 r / min for 1 hour until the materials are completely dissolved, thereby preparing the membrane cleaning agent.

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