Titanium salt-extracellular polymer compound agent and reverse osmosis membrane pollution control method thereof

Abstract

The application discloses a titanium salt-extracellular polymer complexing agent and a reverse osmosis membrane pollution control method thereof, and is used for industrial wastewater treatment reverse osmosis membrane composite pollution control. The method effectively removes suspended particles, colloids, organic matters and microorganisms in wastewater by preparing a complexing agent in a mass ratio of 2:1 of titanium salt and extracellular polymer. Compared with traditional coagulants, the titanium salt complexing agent has a higher pollutant removal rate, can significantly reduce the residual of metal ions, reduce the reverse osmosis membrane cleaning frequency, and prolong the service life of the membrane. The application realizes the recycling of waste resources by extracting extracellular polymers from waste membrane components and sludge in a sewage treatment plant, and provides an efficient and environmentally-friendly treatment scheme for reverse osmosis membrane pollution control of high-salinity organic wastewater.

Description

Technical Field

[0001] This application relates to the fields of membrane separation technology and water treatment, specifically to a method for controlling complex fouling of reverse osmosis membranes by using a complex agent of titanium salt and microbial extracellular polymers, which is particularly suitable for the prevention and control of reverse osmosis membrane fouling in industrial wastewater treatment. Background Technology

[0002] Reverse osmosis membrane technology has been widely used in industrial wastewater treatment, especially in the concentration and desalination processes of zero-discharge systems, where it can effectively recover valuable resources from wastewater. However, with long-term operation, contaminants gradually accumulate on the surface of reverse osmosis membranes, leading to decreased membrane flux, increased operating pressure, and higher energy consumption, ultimately shortening the membrane's lifespan. Because actual industrial wastewater is complex, typically containing large amounts of organic matter, inorganic salts, and microorganisms, these contaminants are difficult to completely remove during pretreatment and gradually form a complex fouling layer on the reverse osmosis membrane surface. This complex fouling layer is not only difficult to remove but also significantly reduces membrane separation performance, increases cleaning frequency, and affects the long-term stable operation of zero-discharge systems.

[0003] Existing coagulation pretreatment methods typically use aluminum and iron salts as coagulants. These coagulants combine with suspended particles and colloidal substances in the water to form flocs, which are then separated by sedimentation and low-pressure membrane separation, thereby reducing fouling deposits on the reverse osmosis membrane surface. However, these traditional coagulants exhibit limitations in treating complex, high-salinity industrial wastewater, particularly in controlling complex fouling of the reverse osmosis membrane. Furthermore, these traditional coagulants tend to leave residual metal ions in the water, leading to secondary pollution and even exacerbating reverse osmosis membrane fouling, affecting the long-term operation of zero-discharge systems and water quality safety.

[0004] Microbial extracellular polymers (LCPs), as natural macromolecules, possess strong adsorption and flocculation capabilities, effectively coagulating organic matter and microorganisms. Furthermore, LCPs can adsorb metal ions in water, reducing metal residues in the treated water. LCPs can also be extracted from the fouled layers of discarded reverse osmosis membranes, further enhancing resource recycling rates. Titanium salts, as a novel coagulant, are gradually becoming a promising water treatment agent due to their excellent complexing ability and biocompatibility. Therefore, developing a coagulation technology based on a combination of microbial LCPs and titanium salts can not only improve the efficiency of removing complex pollutants but also reduce metal residues, enhance the stable operation of reverse osmosis membranes, and meet the technical requirements for pollution control and resource recycling in zero-discharge processes for industrial wastewater. Summary of the Invention

[0005] The purpose of this application is to provide a reverse osmosis membrane fouling control method based on a titanium salt and extracellular polymer compound, which is aimed at the treatment of industrial wastewater containing complex pollutants. This compound can effectively remove inorganic metals, organic matter and microbial components in wastewater, thereby reducing reverse osmosis membrane fouling, reducing cleaning frequency, extending membrane life, and improving system stability and operating efficiency.

[0006] To achieve the above-mentioned objectives, the technical solution provided in this application is as follows:

[0007] (1) Dissolve titanium salt in deionized water at a concentration of 5 g / L-10 g / L, and add a dispersant to improve the solubility and stability of titanium salt to obtain a titanium salt solution.

[0008] (2) Add the extracellular polymer to the titanium salt solution in step (1) at a mass ratio of titanium salt to extracellular polymer of 2:1, stir evenly, and obtain titanium salt-extracellular polymer compound solution.

[0009] (3) When using, dilute the titanium salt-extracellular polymeric compound solution in step (2) to a titanium salt concentration of 5 mg / L-60 mg / L and add it to the water body to be treated.

[0010] In step (1), the titanium salt includes at least one of titanium sulfate, titanium chloride, potassium titanate, sodium titanate, and ammonium titanate. The dispersant is selected from a system containing a solubilizer, a stabilizer, and a low-viscosity solution, preferably a mixture of polyethylene glycol, ethanolamine, and a low molecular weight surfactant, and its proportion is controlled within the range of 0.5%-1% of the titanium salt solution.

[0011] The extracellular polymer in step (2) is extracted from the organic active component by physical or chemical means. The organic active component originates from the fouled layer of spent membrane modules and sludge from wastewater treatment plants. Physical means include at least one of ultrasonic oscillation, filtration, and centrifugation. Chemical means include dissolving the extracellular polymer in the organic active component using an extractant and further purifying it by precipitation and separation. The fouled layer of the membrane module originates from at least one of spent reverse osmosis, nanofiltration, ultrafiltration, and microfiltration membrane modules. The extractant includes at least one of sodium chloride solution and sodium hydroxide solution.

[0012] The titanium salt-extracellular polymeric compound solution in step (3) is added to the water to be treated. After coagulation and sedimentation, the supernatant is separated and introduced into the reverse osmosis membrane system for desalination.

[0013] The optimal concentration of titanium salt in the titanium salt-extracellular polymeric compound solution in step (3) is 25 mg / L, and the mass of the extracellular polymeric compound is 50% of the mass of the titanium salt.

[0014] Compared with the prior art, this application has the following beneficial effects:

[0015] 1. Excellent antifouling performance. The combination of titanium salt and extracellular polymeric substances enhances the flocculation effect, effectively removing suspended particles, organic matter, and inorganic salt pollutants from wastewater. This significantly reduces fouling deposits on the membrane surface, extends the membrane cleaning cycle and service life, and lowers maintenance costs.

[0016] 2. Low metal residue. Titanium salts have strong complexing ability, which can significantly reduce the residual metal ions during coagulation and avoid secondary pollution. Compared with traditional coagulants, titanium salt compound agents have greater environmental advantages and ensure the safety of treated water.

[0017] 3. Suitable for industrial wastewater with high salinity and high organic content. The combination of titanium salt and extracellular polymers enables the compound to maintain stable coagulation effect under complex water quality conditions, making it particularly suitable for wastewater treatment in power plants and chemical industries, significantly improving the economic efficiency and stability of wastewater treatment systems. Attached Figure Description

[0018] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0019] Figure 1 This is a flow chart of the titanium salt-extracellular polymeric compound preparation and wastewater treatment process described in this application.

[0020] Figure 2 The graphs show the comparison of the actual desulfurization wastewater treatment effects of the titanium salt compound, titanium sulfate, and aluminum sulfate provided in the embodiments of this application. In the graphs, A is a comparison graph of turbidity removal rate and B is a comparison graph of total organic carbon (TOC) removal rate.

[0021] Figure 3 A comparison chart showing the metal residue levels after treating actual desulfurization wastewater with titanium salt compound, titanium sulfate, and aluminum sulfate, as provided in the embodiments of this application.

[0022] Figure 4 A comparison chart showing the change in operating flux of a reverse osmosis membrane system after pretreatment with titanium salt compounding agent, titanium sulfate, and aluminum sulfate for actual desulfurization wastewater provided in the embodiments of this application. Detailed Implementation

[0023] The embodiments of this application are described in detail below, with examples of these embodiments shown in the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0024] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in this application is for the purpose of describing particular embodiments only and is not intended to limit this application; unless otherwise stated, the values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art (e.g., they can be tested according to the methods given in the embodiments of this application).

[0025] The terms “comprising” and “having”, and any variations thereof, in the specification and claims of this application are open-ended expressions, meaning they include what is specified in this application but do not exclude other aspects.

[0026] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0027] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0028] This application provides a titanium salt-extracellular polymeric compound and a method for controlling reverse osmosis membrane fouling. The implementation flowchart is shown below. Figure 1 Specifically, it includes the following steps:

[0029] Preparation of S100 and titanium salt-extracellular polymeric compound

[0030] Titanium salt is dissolved in deionized water at a concentration of 5-10 g / L. A dispersant is added to improve the solubility and stability of the titanium salt, resulting in a titanium salt solution. Preferred dispersants are polyethylene glycol or other low molecular weight solubilizers, with a dispersant ratio of 0.5%-1% of the total solution mass. Then, the extracellular polymeric substance (ECPL) is added to the titanium salt solution at a mass ratio of 2:1 (titanium salt to EPL), and the mixture is stirred until homogeneous, yielding a titanium salt-ECPL composite solution. The EPL is extracted from the organic active component using physical or chemical methods. The organic active component originates from the fouled layer of waste membrane modules and sludge from wastewater treatment plants.

[0031] S200, compound agent coagulation treatment wastewater sample

[0032] When using, dilute the titanium salt-extracellular polymeric compound solution from step (1) to a titanium salt concentration of 5 mg / L-60 mg / L, preferably to 25 mg / L. Add the compound solution to the industrial wastewater to be treated, ensuring that it is fully mixed with the suspended particles, organic matter and inorganic salts in the water to cause a flocculation reaction and form larger flocs.

[0033] S300, Reverse Osmosis Membrane System Operation

[0034] After the coagulation reaction, the water sample is allowed to stand for flocculation and sedimentation, and the supernatant is separated. The separated supernatant is then introduced into the reverse osmosis membrane system for desalination. After the pretreated water enters the reverse osmosis membrane system, the fouling load is significantly reduced, extending the membrane's lifespan and reducing the cleaning frequency.

[0035] The following specific embodiments illustrate the solution of this application. It should be noted that these embodiments are for illustrative purposes only and should not be considered as limiting the scope of this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0036] Example 1

[0037] In this embodiment, a compound agent prepared by titanium sulfate and extracellular polymeric substances at a mass ratio of 2:1 was used to treat flue gas desulfurization wastewater from a coal-fired power plant. The compound agent was added to the desulfurization wastewater at dosages of 5 mg / L, 10 mg / L, 15 mg / L, 20 mg / L, 25 mg / L, 30 mg / L, 40 mg / L, 50 mg / L, and 60 mg / L. The coagulation operation conditions were: rapid stirring at 200 rpm for 1.5 min, followed by slow stirring at 40 rpm for 20 min, and standing for 30 min. Samples were then taken from 2 cm below the surface of the supernatant to test the turbidity and TOC in the wastewater.

[0038] Example 2

[0039] In this embodiment, titanium sulfate coagulant was used and added to the flue gas desulfurization wastewater from a coal-fired power plant at dosages of 5 mg / L, 10 mg / L, 15 mg / L, 20 mg / L, 25 mg / L, 30 mg / L, 40 mg / L, 50 mg / L, and 60 mg / L. The coagulation operating conditions were the same as in Example 1, and the turbidity and TOC in the wastewater were measured.

[0040] Example 3

[0041] In this embodiment, aluminum sulfate coagulant was used and added to the flue gas desulfurization wastewater from a coal-fired power plant at dosages of 5 mg / L, 10 mg / L, 15 mg / L, 20 mg / L, 25 mg / L, 30 mg / L, 40 mg / L, 50 mg / L, and 60 mg / L. The coagulation operation conditions were the same as in the previous embodiment, and the turbidity and TOC in the wastewater were measured.

[0042] like Figure 2 As shown in Figure A, regarding turbidity removal, the titanium salt compound achieved a maximum turbidity removal rate of 98% at a dosage of 25 mg / L. With further increases in dosage, the turbidity removal rate remained at a high level and exhibited stability. In contrast, the titanium sulfate in Comparative Example 1 achieved a turbidity removal rate of 93% at a dosage of 25 mg / L, but the removal rate decreased significantly when the dosage exceeded 30 mg / L. The aluminum sulfate in Comparative Example 2 showed lower turbidity removal rates than the titanium salt compound under all dosage conditions.

[0043] like Figure 2 As shown in Figure B, when the dosage of the titanium salt compound was 25 mg / L, the TOC concentration was 41.61 mg / L, and the removal rate was 14.79%. In contrast, the removal rate of titanium sulfate in Comparative Example 1 was 10.17% at 25 mg / L, and the removal rate of aluminum sulfate in Comparative Example 2 was only 8.45% at the same dosage.

[0044] The titanium salt compound exhibits superior performance compared to titanium sulfate and aluminum sulfate in removing both turbidity and TOC. Particularly at lower dosages, the titanium salt compound demonstrates better removal efficiency and stability. These results indicate that the compound can not only effectively improve turbidity removal but also effectively remove organic pollutants from wastewater.

[0045] Example 4

[0046] This example tested the effect of titanium salt compound on metal residues at different dosages. A compound prepared using titanium sulfate and an extracellular polymeric substance at a 2:1 mass ratio was added to flue gas desulfurization wastewater from a coal-fired power plant at dosages of 5 mg / L, 10 mg / L, 15 mg / L, 20 mg / L, 25 mg / L, 30 mg / L, 40 mg / L, 50 mg / L, and 60 mg / L. The wastewater was treated under the same operating conditions as in Example 1, and finally, samples were taken from 2 cm below the surface of the supernatant to detect the amount of metal residues in the solution.

[0047] Example 5

[0048] In this embodiment, titanium sulfate coagulant was used and added to the flue gas desulfurization wastewater of a coal-fired power plant at dosages of 5 mg / L, 10 mg / L, 15 mg / L, 20 mg / L, 25 mg / L, 30 mg / L, 40 mg / L, 50 mg / L, and 60 mg / L, under the same operating conditions as in the previous embodiment. The residual metal content in the coagulant was determined.

[0049] Example 6

[0050] In this embodiment, aluminum sulfate coagulant was used and added to the flue gas desulfurization wastewater of a coal-fired power plant at dosages of 5 mg / L, 10 mg / L, 15 mg / L, 20 mg / L, 25 mg / L, 30 mg / L, 40 mg / L, 50 mg / L, and 60 mg / L, under the same operating conditions as in the previous embodiment. The residual metal content in the coagulant was determined.

[0051] Figure 3 The comparison of residual metal concentrations of the three coagulants is shown. At a dosage of 30 mg / L, the residual metal concentration of the titanium salt compound was 1.06 mg / L, significantly lower than that of Comparative Example 5 (2.96 mg / L) and Comparative Example 6 (2.00 mg / L). Even at higher dosages of 50 mg / L-60 mg / L, the titanium salt compound still maintained a low residual metal concentration of approximately 2.2 mg / L, indicating its significant advantage in reducing metal residues.

[0052] Example 7

[0053] This embodiment evaluates the flux changes of a reverse osmosis membrane system after pretreatment of actual desulfurization wastewater with a titanium salt compound. The desulfurization wastewater was pretreated with a compound of titanium sulfate and extracellular polymeric substances at a mass ratio of 2:1 for coagulation. The supernatant of the treated wastewater was then filtered through a low-pressure membrane and used as the feed water for the reverse osmosis membrane system. The normalized flux (J / J) of the reverse osmosis system was recorded at 12h, 24h, 36h, and 48h.

[0054] Example 8

[0055] In this embodiment, titanium sulfate coagulant was used to pretreat the desulfurization wastewater through coagulation. The supernatant of the treated wastewater was filtered through a low-pressure membrane and used as the feed water for the reverse osmosis membrane system. The normalized flux (J / J) of the reverse osmosis system was recorded at 12h, 24h, 36h, and 48h.

[0056] Example 9

[0057] In this embodiment, aluminum sulfate coagulant was used to pretreat the desulfurization wastewater through coagulation. The supernatant of the treated wastewater was filtered through a low-pressure membrane and used as the feed water for the reverse osmosis membrane system. The normalized flux (J / J) of the reverse osmosis system was recorded at 12h, 24h, 36h, and 48h.

[0058] Figure 4 The normalized flux changes of three coagulants in a reverse osmosis membrane system are shown. The normalized flux of the titanium salt compound in the examples is 0.90 after 48 hours, maintaining a high flux level, while the fluxes of Examples 8 and 9 are 0.80 and 0.61, respectively. This indicates that the titanium salt compound can more effectively reduce reverse osmosis membrane fouling, extend the cleaning cycle of the reverse osmosis membrane, and maintain the stability of the system.

[0059] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A method for controlling reverse osmosis membrane fouling based on titanium salt-extracellular polymeric substance complexing agent, characterized by, The method comprises the following steps: (1) Dissolve titanium salt in deionized water, the concentration of the titanium salt is 5-10 g / L, and add a dispersant to improve the solubility and stability of the titanium salt to obtain a titanium salt solution; (2) Add extracellular polymers to the titanium salt solution at a mass ratio of titanium salt to extracellular polymers of 2:1, stir uniformly to obtain a titanium salt-extracellular polymer complexing agent solution; (3) When used, dilute the titanium salt-extracellular polymer complexing agent solution to a titanium salt concentration of 5-60 mg / L, and add the diluted complexing agent to the water to be treated; (4) After coagulation and sedimentation treatment, the supernatant is separated and introduced into a reverse osmosis membrane system for desalination treatment; The extracellular polymers are extracted from organic active components by physical or chemical means, the organic active components are from the waste membrane module pollution layer and the sludge of the sewage treatment plant, the physical means include at least one of ultrasonic oscillation, filtration and centrifugal separation, the chemical means include using a leaching agent to dissolve the extracellular polymers in the organic active components, and further purifying by precipitation and separation, the waste membrane module pollution layer is from at least one of the waste reverse osmosis, nanofiltration, ultrafiltration, microfiltration membrane module, and the leaching agent includes at least one of sodium chloride solution and sodium hydroxide solution; The titanium salt includes at least one of titanium sulfate, titanium chloride, potassium titanate, sodium titanate, and ammonium titanate, and the dispersant is a composition containing a solubilizing agent, a stabilizer, and a low-viscosity solution system, the mass fraction of which in the titanium salt solution is in the range of 0.5%-1%.

2. The reverse osmosis membrane fouling control method of claim 1, wherein, The dispersant is a mixture of polyethylene glycol, ethanolamine, and low-molecular-weight surfactants.

3. The method of reverse osmosis membrane fouling control of claim 1, wherein, The concentration of titanium salt in the titanium salt-extracellular polymer complexing agent solution is 25 mg / L, and the mass of the extracellular polymers is 50% of the mass of the titanium salt.

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