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

Abstract

The invention discloses a titanium salt-extracellular polymeric compound and a reverse osmosis membrane pollution control method thereof. The titanium salt-extracellular polymeric compound is used for reverse osmosis membrane combined pollution control in industrial wastewater treatment. According to the method, a compound agent is prepared from titanium salt and extracellular polymeric substances according to the mass ratio of 2: 1, and suspended particles, colloids, organic matter and microorganisms in wastewater are effectively removed. Compared with traditional coagulants and titanium salt compounding agents, the coagulant and titanium salt compounding agent has a higher pollutant removal rate, metal ion residues can be remarkably reduced, the reverse osmosis membrane cleaning frequency is reduced, and the service life of a membrane is prolonged. By extracting the extracellular polymeric substances in the waste membrane component and the sludge of the sewage treatment plant, the cyclic utilization of waste resources is realized, and an efficient and environment-friendly treatment scheme is provided for reverse osmosis membrane pollution control of the high-salt organic wastewater.

Description

Technical Field

[0001] The present application relates to the field of membrane separation technology and water treatment, and specifically to a composite agent for controlling the composite pollution of reverse osmosis membranes by using titanium salts and microbial extracellular polymers, and is particularly suitable for the prevention and control of reverse osmosis membrane pollution in industrial wastewater treatment. Background Art

[0002] Reverse osmosis membrane technology has been widely used in the field of industrial wastewater treatment, especially in the concentration and desalination process of zero-emission processes, which can effectively recover valuable resources in wastewater. However, with the long-term operation of the reverse osmosis membrane, pollutants gradually accumulate on the membrane surface, resulting in a decrease in membrane flux, an increase in operating pressure and energy consumption, and ultimately shortening the service life of the membrane. Due to the complex composition of actual industrial wastewater, it usually contains a large amount of organic matter, inorganic salts and microorganisms. These pollutants are difficult to completely remove in the pretreatment stage and will gradually form a composite pollution layer on the surface of the reverse osmosis membrane. The composite pollution layer is not only difficult to remove, but also significantly reduces the separation performance of the membrane, increases the cleaning frequency, and affects the long-term stable operation of the zero-emission system.

[0003] Existing coagulation pretreatment methods usually use aluminum salts and iron salts as coagulants, which combine with suspended particles and colloidal substances in the water to form flocs, which are then separated by precipitation and low-pressure membranes to reduce pollution deposition on the surface of the reverse osmosis membrane. However, these traditional coagulants have limitations in treating high-salt industrial wastewater with complex components, especially in controlling complex pollution of reverse osmosis membranes. In addition, these traditional coagulants are prone to residual metal ions in the water body, causing secondary pollution and even aggravating the pollution of the reverse osmosis membrane, affecting the long-term operation of the zero-emission system and water quality safety.

[0004] As a natural polymer substance, microbial extracellular polymers have strong adsorption and flocculation capabilities and can effectively flocculate organic matter and microorganisms. In addition, extracellular polymers can also adsorb metal ions in water and reduce the metal residues of coagulants after treatment. Extracellular polymers can be extracted from the pollution layer of discarded reverse osmosis membranes, further improving the recycling rate of resources. As a new type of coagulant, titanium salts have gradually become a potential water treatment agent due to their excellent complexing ability and biocompatibility. Therefore, the development of a composite coagulation technology based on microbial extracellular polymers and titanium salts can not only improve the efficiency of removing complex pollutants, but also reduce metal residues, enhance the stable operation performance of reverse osmosis membranes, and meet the technical requirements for pollution control and resource recycling in the zero-discharge process of industrial wastewater. Summary of the invention

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

[0006] In order to achieve the above application purpose, the technical solution provided by this application is as follows:

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

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

[0009] (3) When in use, the titanium salt-extracellular polymer compound solution in step (2) is diluted to a titanium salt concentration of 5 mg / L-60 mg / L, and then added to the water to be treated.

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

[0011] The extracellular polymers in step (2) are extracted from the organic active components by physical or chemical means, and the organic active components come from the pollution layer of the discarded membrane components and the sludge of the sewage treatment plant. The physical means include at least one of ultrasonic oscillation, filtration and centrifugal separation, and the chemical means include using a leaching agent to dissolve the extracellular polymers in the organic active components and further purifying them by precipitation and separation, the pollution layer of the membrane components comes from at least one of the discarded reverse osmosis, nanofiltration, ultrafiltration and microfiltration membrane components, and the leaching agent includes at least one of a sodium chloride solution and a sodium hydroxide solution.

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

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

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

[0015] 1. Good anti-pollution performance. The combination of titanium salt and extracellular polymers enhances the flocculation effect, effectively removes suspended particles, organic matter and inorganic salt pollutants in wastewater, significantly reduces pollution deposition on the membrane surface, prolongs the cleaning cycle and service life of the membrane, and reduces maintenance costs.

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

[0017] 3. Suitable for high-salt and high-organic industrial wastewater. The combination of titanium salt and extracellular polymers enables the compound agent to maintain a stable coagulation effect under complex water conditions. It is particularly suitable for wastewater treatment in power plants and chemical industries, and significantly improves the economic benefits and stability of the wastewater treatment system. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0020] Figure 2 This is a comparison chart of the treatment effects of the titanium salt compound, titanium sulfate and aluminum sulfate on actual desulfurization wastewater provided in the examples of the present application, wherein A is a comparison chart of turbidity removal rate, and B is a comparison chart of total organic carbon (TOC) removal rate.

[0021] Figure 3 This is a comparison chart of the metal residues after treating actual desulfurization wastewater with the titanium salt compound, titanium sulfate and aluminum sulfate provided in the examples of the present application.

[0022] Figure 4 This is a comparison chart of the changes in the operating flux of the reverse osmosis membrane system after the actual desulfurization wastewater provided in the embodiments of the present application was pretreated with a titanium salt compound, titanium sulfate and aluminum sulfate. DETAILED DESCRIPTION

[0023] The embodiments of the present application are described in detail below. Examples of the embodiments are shown in the drawings, but unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of actually identical structures may be omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0024] Unless otherwise defined, all technical and scientific terms used in this application have the same meanings as those commonly understood by technicians in the technical field to which this application belongs; the terms used in this application are only for the purpose of describing specific embodiments and are not intended to limit this application; unless otherwise specified, the numerical values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art (for example, they can be tested according to the methods given in the embodiments of this application).

[0025] The terms "including" and "having" in the specification and claims of the present application and any modifications thereof are open expressions, that is, including the contents specified in the present application but not excluding other contents.

[0026] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0027] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0028] The present application provides a titanium salt-extracellular polymer compound and a method for controlling reverse osmosis membrane pollution. The implementation flow chart is shown in Figure 1 , specifically including the following steps:

[0029] Preparation of S100, titanium salt-extracellular polymer compound

[0030] Dissolve titanium salt in deionized water at a concentration of 5g / L-10g / L, add a dispersant to improve the solubility and stability of the titanium salt, and obtain a titanium salt solution. The preferred dispersant is polyethylene glycol or other low molecular weight solubilizers, and the proportion of the dispersant is 0.5%-1% of the total mass of the solution. Then, the extracellular polymer is added to the titanium salt solution at a mass ratio of 2:1 between titanium salt and extracellular polymer, and stirred evenly to obtain a titanium salt-extracellular polymer compound solution. The extracellular polymer is extracted from the organic active component by physical or chemical means, and the organic active component comes from the pollution layer of the discarded membrane assembly and the sludge of the sewage treatment plant.

[0031] S200, compound agent coagulation treatment wastewater sample

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

[0033] S300, reverse osmosis membrane system operation

[0034] After the coagulation reaction, the water sample is left to stand for flocculation and precipitation, and the supernatant is separated. The separated supernatant is further introduced into the reverse osmosis membrane system for desalination. After the pretreated water enters the reverse osmosis membrane system, the pollution load is significantly reduced, which prolongs the service life of the membrane and reduces the cleaning frequency.

[0035] The scheme of the present application is described below by specific examples. It should be noted that the following examples are only used to illustrate the present application and should not be considered as limiting the scope of the present application. If no specific technology or conditions are specified in the examples, the technology or conditions described in the literature in this area or the product instructions are used. The reagents or instruments used are not specified by the manufacturer, and are all conventional products that can be obtained commercially.

[0036] Example 1

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

[0040] Example 3

[0041] In this embodiment, aluminum sulfate coagulant was used and added to the flue gas desulfurization wastewater of 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 those in the embodiment, and the turbidity and TOC in the wastewater were detected.

[0042] like Figure 2 As shown in A, in terms of turbidity removal, the turbidity removal rate of the titanium salt compound agent reached a maximum value of 98% at a dosage of 25 mg / L. As the dosage further increased, the turbidity removal rate remained at a high level and showed stability. In contrast, the turbidity removal rate of titanium sulfate in Comparative Example 1 at a dosage of 25 mg / L was 93%, and when the dosage exceeded 30 mg / L, the removal rate dropped significantly. The turbidity removal rate of aluminum sulfate in Comparative Example 2 at different dosages was lower than that of the titanium salt compound agent.

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

[0044] The titanium salt compound agent is superior to titanium sulfate and aluminum sulfate in removing turbidity and TOC. Especially at a lower dosage, the titanium salt compound agent showed better removal effect and stability. The results show that the compound agent can not only effectively improve the turbidity removal rate, but also better remove organic pollutants in wastewater.

[0045] Example 4

[0046] This example tests the effect of titanium salt compound on metal residues at different dosages. A compound prepared by using titanium sulfate and extracellular polymers in a mass ratio of 2:1 was 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. The wastewater was treated under the same operating conditions as in Example 1, and finally a sample was taken 2 cm below the surface of the supernatant to detect the metal residue in the solution.

[0047] Example 5

[0048] In this embodiment, titanium sulfate coagulant was used and added to the flue gas desulfurization wastewater of 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, and the operating conditions were the same as those in the embodiment. The metal residue in the coagulant was measured.

[0049] Example 6

[0050] In this embodiment, aluminum sulfate coagulant was used and added to the flue gas desulfurization wastewater of 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, and the operating conditions were the same as those in the embodiment. The metal residue in the coagulant was measured.

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

[0052] Example 7

[0053] This example evaluates the change in the operating flux of the reverse osmosis membrane system after actual desulfurization wastewater is pretreated with a titanium salt compound. The desulfurization wastewater is pretreated by coagulation using a compound of titanium sulfate and extracellular polymers in a mass ratio of 2:1. The treated wastewater supernatant is filtered through a low-pressure membrane as the influent of the reverse osmosis membrane system, and the normalized flux (J / J) of the reverse osmosis system is recorded at 12h, 24h, 36h, and 48h.

[0054] Example 8

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

[0056] Example 9

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

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

[0059] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A method for preparing a titanium salt-extracellular polymer compound, characterized in that: The method comprises the following steps: (1) dissolving a titanium salt in deionized water, wherein the concentration of the titanium salt is 5 g / L-10 g / L, and adding a dispersant to improve the solubility and stability of the titanium salt to obtain a titanium salt solution; (2) adding the extracellular polymer to the titanium salt solution at a mass ratio of titanium salt to extracellular polymer of 2:1, stirring evenly, to obtain a titanium salt-extracellular polymer composite solution; (3) When in use, the titanium salt-extracellular polymer compound solution is diluted to a titanium salt concentration of 5 mg / L-60 mg / L, and then added and dissolved into the water to be treated.

2. The method for preparing the titanium salt-extracellular polymer compound according to claim 1, characterized in that: The titanium salt includes at least one of titanium sulfate, titanium chloride, potassium titanate, sodium titanate, and ammonium titanate. The dispersant is a solution 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 mass proportion in the titanium salt solution is in the range of 0.5%-1%.

3. The method for preparing the titanium salt-extracellular polymer compound according to claim 1, characterized in that: The extracellular polymers are extracted from organic active components by physical or chemical means, and the organic active components come from the pollution layer of discarded membrane components and the sludge of sewage treatment plants. The physical means include at least one of ultrasonic oscillation, filtration and centrifugal separation, and the chemical means include using an extractant to dissolve the extracellular polymers in the organic active components and further purifying them by precipitation and separation. The pollution layer of the discarded membrane components comes from at least one of discarded reverse osmosis, nanofiltration, ultrafiltration and microfiltration membrane components, and the extractant includes at least one of a sodium chloride solution and a sodium hydroxide solution.

4. A titanium salt-extracellular polymer compound and a method for controlling reverse osmosis membrane pollution, characterized in that: The titanium salt-extracellular polymer compound solution of claim 1 is added to the water to be treated, and a supernatant is obtained after coagulation and sedimentation treatment, and the supernatant is introduced into a reverse osmosis membrane system for desalination treatment.

5. The method for controlling reverse osmosis membrane pollution according to claim 4, characterized in that: The concentration of the titanium salt in the titanium salt-extracellular polymer compound solution is 5 mg / L-60 mg / L, preferably 25 mg / L, and the mass of the extracellular polymer is 50% of the mass of the titanium salt.

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