A method for preparing an anti-fouling permeable membrane and water treatment applications

Abstract

The application discloses a preparation method of an anti-pollution permeation membrane and water treatment application. The preparation method comprises the following steps: PAN, LiCl and UiO-66-(COOH)2 are added into an NMP solvent to configure a casting solution, magnetic stirring is carried out at 60 DEG C for 12 hours, and a PAN / LiCl / UiO matrix membrane with a PET non-woven fabric as a support layer is prepared by a phase inversion method. Then, the matrix membrane is subjected to hydrophilic modification and improvement of a pore structure by using Ar plasma, a polyamide active layer is prepared by an interfacial polymerization method, and PL solution is prepared to perform graft modification on the polyamide layer. The anti-pollution permeation membrane prepared by the method can realize synchronous dye recovery and draw solution reuse in printing and dyeing wastewater, improve the performance of the permeation membrane, relieve membrane pollution by vibration, and restore the membrane flux of the polluted membrane by modified micro-bubbles.

Description

TECHNICAL FIELD

[0001] The application relates to a preparation method of an anti-pollution permeation membrane and water treatment application, and belongs to the field of wastewater treatment. BACKGROUND

[0002] Industrial wastewater is mostly high-concentration and refractory organic wastewater, which has the characteristics of multiple types of pollutants, high concentration of organic matter, low biodegradability, strong biological inhibition, high salt content, and great toxicity. Conventional treatment technologies are difficult to achieve efficient and stable operation, and the distribution characteristics and harmful effects of trace amounts of high-risk pollutants in the drainage are also difficult to accurately analyze and evaluate. Therefore, it is urgent to develop a new technology to efficiently treat industrial wastewater.

[0003] Compared with pressure-driven membranes such as reverse osmosis (RO) and ultrafiltration (UF), forward osmosis (FO) technology does not require external pressure, has the advantages of low energy consumption and low membrane fouling tendency, and uses the osmotic pressure on both sides of the membrane as the driving force, thereby reducing the operation cost. However, FO also has some problems during operation, such as concentration polarization, draw solution regeneration, and membrane fouling. The development of high-performance FO membranes plays an important role in the commercialization of FO. Although membrane fouling is inevitable, it can be alleviated by optimizing the operating conditions, cleaning the membrane, and modifying the membrane, thereby improving the operating performance of forward osmosis. The reasonable selection and regeneration of the draw solution can achieve near-zero discharge of printing and dyeing wastewater. For example, the diluted draw solution after permeation can be further evaporated and crystallized, concentrated and reused, or diluted and directly applied. For the concentrated feed liquid, material recovery can be achieved through chemical precipitation, extraction, and other methods. Wastewater resource treatment has great research significance for water treatment applications with high COD concentration, high colority, and large water quality changes. SUMMARY

[0004] The purpose of the present application is to overcome the shortcomings of low pollutant interception rate, poor permeation capacity, poor anti-pollution performance, and difficulty in recycling the draw solution of the prior art forward osmosis membrane. The present application provides a preparation method of an anti-pollution permeation membrane with high membrane flux and the application of the anti-pollution permeation membrane in water treatment. The anti-pollution permeation membrane prepared by the method is used in water treatment, the feed liquid is printing and dyeing wastewater, the concentrated feed liquid is extracted by dimethyl sulfoxide to recover dyes, and the recovered dyes are reused in the dyeing process of textile printing and dyeing. The draw solution is common chemical waste sodium dodecyl benzene sulfonate (SDBS), which can be directly diluted and reused in the dyeing, finishing, and refining processes after use. The anti-pollution permeation membrane combined with vibration treatment and nano-bubble can simultaneously achieve dye recovery and draw solution reuse in printing and dyeing wastewater, improve the performance of the permeation membrane, alleviate membrane fouling through vibration, and clean the fouled membrane with modified micro-bubbles, thereby restoring the membrane flux of the fouled membrane.

[0005] To achieve the above-mentioned purpose, the present application provides a preparation method of an anti-pollution permeation membrane, comprising the following steps:

[0006] Step 1: mix the dried PAN polymer, LiCl, UiO-66-(COOH)2 and NMP to form a casting solution;

[0007] Step 2: lay the PET non-woven fabric on a glass plate, degas the casting solution obtained in step 1, and uniformly coat it on the non-woven fabric, then use a doctor blade to prepare a base film, and then immediately immerse it in a water bath to perform a phase separation reaction to obtain a PAN / LiCl / UiO base film;

[0008] Step 3: treat the PAN / LiCl / UiO base film obtained in step 2 with Ar plasma to improve the hydrophilicity of the film, then immerse the treated base film in a m-phenylenediamine aqueous solution, take it out and dry it, and then immerse the base film in an isopar-G solution of trimesoyl chloride to perform an interfacial polymerization reaction to form a PA layer on the surface of the base film;

[0009] Step 4: after the interfacial polymerization reaction, add a polylysine solution for graft modification treatment, so that the amino groups on the polylysine molecules covalently react with the acyl chloride groups on the PA layer to form new amide bonds, and then vacuum dry the film to improve the crosslinking degree of the PA to obtain a polylysine grafted PAN / LiCl / UiO anti-pollution permeation membrane, which comprises a PET non-woven fabric support layer, an Ar plasma modified PAN / LiCl / UiO matrix film and a PL covalently grafted and modified polyamide active layer.

[0010] Preferably, the mass percentage of PAN in the casting solution of step 1 is 12-15 wt%, the mass percentage of LiCl is 0.5-2.0 wt%, and the mass percentage of UiO-66-(COOH)2 is 0.025-0.1 wt%.

[0011] Preferably, the Ar plasma treatment in step 3 is performed under the following conditions: a voltage of 6-10 KV and a gas flow rate of 100-150 mL / min at normal pressure for 10-60 s.

[0012] Preferably, the concentration of the polylysine solution in step 4 is 0.1-1.0 wt% PL, and the polylysine solution is prepared by dissolving sodium hydroxide and polylysine hydrochloride PL·HCl in water, wherein w(NaOH) / w(PL·HCl) = 0.20-0.40, and the treatment time is 10-30 min.

[0013] The application also provides the application of the anti-pollution permeation membrane prepared by the above-mentioned preparation method of the anti-pollution permeation membrane in wastewater treatment.

[0014] The application further provides a method for treating printing and dyeing wastewater and simultaneously recovering dyes and draw solution by using the anti-fouling permeable membrane prepared by the method.

[0015] Preferably, the concentration of the draw solution is 0.5-2M, and the diluted concentration is 1-10wt%.

[0016] Preferably, the anti-fouling permeable membrane after operation is cleaned by the method of modified micro-bubble assisted cleaning, so as to remove the pollutants on the membrane surface and restore the membrane flux.

[0017] Preferably, the specific method of cleaning includes: modifying the nano-bubbles by using a mixed solution of 0.1-1wt% NaOH and 0.1-0.5wt% sodium dodecyl benzene sulfonate (SDBS), the average size of the nano-bubbles is 100-150nm, the concentration is 7.5x10 7 ~8x10 7 The modified micro-bubbles are introduced into the feed liquid side by a micro-bubble generator to clean the polluted membrane, and the treatment time is 10-30min.

[0018] The application prepares a new type of PL / PAN / LiCl / UiO anti-fouling permeable membrane by modification methods such as polymer blending, MOF material loading, plasma irradiation and PL molecule grafting, and the anti-fouling permeable membrane has the advantages of good hydrophilicity, strong permeability and anti-fouling, and shows good separation performance. The composite permeable membrane is combined with nano-bubbles and vibration, and a vibration assisted permeable membrane system is used to effectively relieve the pollution on the membrane surface, maintain the stability of the membrane performance, and improve the service life of the membrane. The polluted membrane after operation is cleaned by modified nano-bubbles, the dense dirt on the membrane surface can be effectively removed, the flux recovery rate is high, and the reuse rate of the membrane is greatly improved. The raw material liquid of the permeable membrane separation is printing and dyeing wastewater, the concentrated feed liquid is extracted by dimethyl sulfoxide, and the dyes can be recovered; the draw solution is common chemical waste ammonium sulfate or SDBS, and after use, it can be diluted and directly used in the dyeing, finishing and refining processes of printing and dyeing.

[0019] Compared with the prior art, the application has the advantages that:

[0020] (1) The PL / PAN / LiCl / UiO anti-fouling permeable membrane prepared by the application has the characteristics of high water flux, high selectivity, strong hydrophilicity, low structure parameter and anti-fouling;

[0021] (2) Through the auxiliary permeation process, the deposition of membrane surface pollutants is effectively alleviated, the performance stability of the membrane operation is realized, and the service life of the membrane is improved;

[0022] (3) The concentrated dye wastewater can realize the recovery of dyes through extraction;

[0023] (4) The common chemical waste SDBS is used as the draw solution, and after use, it can be directly used for dyeing, finishing and refining processes in printing and dyeing after dilution.

[0024] (5) The modified micro-bubble assisted cleaning has a high removal effect on the dirt on the polluted membrane surface, has a small influence on the physical and chemical properties of the membrane, and improves the reusability of the membrane. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 It is a process flow diagram of the present application;

[0026] Figure 2 It is the SEM diagram of the anti-pollution permeation membrane obtained in Example 1; (a)-(e): the SEM diagrams of the surface of the base membrane prepared by different concentrations of LiCl, (f)-(j): the surface morphology of the base membrane after interfacial polymerization corresponding to the LiCl concentration, (k)-(o): the cross-section diagram of the base membrane after interfacial polymerization corresponding to the LiCl concentration;

[0027] Figure 3 It is a diagram of the pure water flux and the reverse salt flux of the anti-pollution permeation membrane obtained in Example 1 changing with time;

[0028] Figure 4 It is a diagram of the water flux of the anti-pollution permeation membrane obtained in Example 2 changing with time; (a): the pure water flux of different types of membranes running for 600min in AL-FS mode, (b): the normalized flux of different types of membranes running for 600min in AL-FS mode;

[0029] Figure 5 It is the permeation performance and retention performance of the anti-pollution permeation membrane obtained in Example 3 in AL-FS mode (a) and AL-DS mode (b);

[0030] Figure 6 It is the water flux (a) and the reverse salt flux (b) of the anti-pollution permeation membrane obtained in Example 4 when SDBS is used as the draw solution;

[0031] Figure 7 It is the result of the flux recovery experiment by the micro-bubble assisted cleaning method in Example 5; (a): the normalized flux of the original membrane and the modified membrane after micro-bubble assisted cleaning for 10min, (b): the water flux of the original membrane and the modified membrane before and after micro-bubble assisted cleaning;

[0032] Figure 8 Schematic diagram of microbubble assisted cleaning principle. DETAILED DESCRIPTION

[0033] In order to make the present application more apparent and easy to understand, the preferred embodiments are described in detail below with the accompanying drawings.

[0034] Example 1

[0035] A preparation method of a PL / PAN / LiCl / UiO anti-pollution permeable membrane and application of the permeable membrane coupled with vibration / microbubbles, comprising the following steps:

[0036] (1) A PAN / LiCl / UiO base membrane is prepared by a phase inversion method. 12 wt.% polyacrylonitrile PAN (Sigma-Aldrich, Mw 150,000), 0.5-2.0 wt.% LiCl (Sigma-Aldrich, 99%) and 0.025-0.1 wt% UiO-66-(COOH)2 are added to an NMP (10 mL, China Pharmaceutical) solvent, and the casting solution is stirred at 60°C for 12 h to form a casting solution, which is then left to stand and degassed for standby. PET non-woven fabric is placed on a clean flat glass, then the casting solution is poured onto the non-woven fabric, a film doctor with a thickness of 100 μm is used to scrape the film, and immediately placed in 35°C deionized water for phase separation reaction to obtain a base membrane;

[0037] (2) The base membrane obtained in step 1 is further treated with Ar plasma under the conditions of normal pressure, voltage 6-10 KV, and gas flow rate 100.0-150.0 mL / min for 10-60 s to improve the hydrophilicity of the membrane;

[0038] (3) The membrane obtained in step 2 is further covered with a 2.0 wt.% MPD (m-phenylenediamine) aqueous solution for 2 min, and then the residual MPD solution is carefully removed using a hair dryer. Then, 0.15 wt.% TMC (trimesoyl chloride) dissolved in Isopar-G (isomeric alkane solvent, ExxonMobil) is poured onto the base membrane for 1 min to complete the interfacial polymerization reaction.

[0039] (4) The PAN-1.5LiCl-0.05UiO base membrane with the best performance is selected for interfacial polymerization reaction. After the reaction is completed, the membrane is immediately treated with a PL solution (0.1-1.0 wt.% PL·HCl, wherein w(NaOH) / w(PL·HCl)=0.26) with different concentrations for graft modification, i.e. the prepared PL solution is covered on the surface of the PA layer for 20 min, so that the amino group on the PL molecule reacts with the acyl chloride group on the PA layer to form a new amide bond; the membrane is characterized and tested, and the SEM image of the obtained composite permeable membrane is shown in Figure 2 .

[0040] (5) Put the prepared composite penetration membrane into a self-made membrane module with an effective area of 3 cm x 4 cm, DI water (deionized water) as the feed liquid, 0.5M NaCl as the draw liquid, and the feed liquid flow rate of 16 cm / min, and perform a forward osmosis performance test.

[0041] The results show that the original membrane and the modified membrane both have obvious ridge-valley structure, which shows that the PL grafting modification does not destroy the typical structure of the PA layer. With the addition of LiCl, the finger-shaped large pore structure of the membrane increases, while the sponge-like structure decreases, the pore size and porosity are improved, and the hydrophilic performance of the membrane is improved. It can be seen from Figure 3 that with the increase of the PL loading amount, the water diffusion resistance of the FO membrane increases, and the water flux slightly decreases, but since the PL molecule contains a large number of hydrophilic groups (-NH2, -COOH) that can improve the hydrophilic performance of the membrane surface, the water flux of the FO membrane is improved, and the performance of the membrane is more stable.

[0042] Example 2

[0043] The difference between this embodiment and Example 1 is that the feed liquid in step (5) is the actual printing and dyeing wastewater secondary sedimentation tank effluent, in order to study the water production performance of the composite penetration membrane for actual wastewater treatment.

[0044] It can be seen from Figure 4 that the flux of the modified membrane decreases more slowly, the normalized water flux of FO-0.5PL membrane only decreases by 33.6%, and the average water flux is 9.3 LMH, and the water flux of the unmodified membrane decreases more than other modified membranes, which shows that grafting PL on the surface of the FO membrane can enhance the anti-pollution ability of the membrane, and the performance of the membrane is more stable.

[0045] Example 3

[0046] The difference between this embodiment and Example 1 is that the feed liquid in step (5) is the actual printing and dyeing wastewater secondary sedimentation tank effluent, the draw liquid is 0.5M NaCl solution, and different membrane orientations are set, in order to study the influence of different membrane orientations on the treatment performance of the composite penetration membrane.

[0047] The results are shown in Figure 5 , it can be seen from Figure 5 that compared with the AL-DS mode, the FO membrane has better retention performance for pollutants in the AL-FS mode, mainly because in the AL-DS mode, the porous support layer of the FO membrane faces the raw material liquid, the membrane surface has larger and rougher pore size, which easily makes a large amount of pollutants enter the porous structure and cause rapid pollution. The improvement of the surface potential of the modified membrane weakens the adsorption of Ca 2+ , Mg 2+The electrostatic attraction between the membrane and the membrane surface mitigates organic fouling of the FO membrane. For pollutants present in small amounts in the feed solution, the membrane maintains rejection rates of over 97.1%, 99.0%, and 99.3% for trace pollutants Sb, Cr, and aniline, respectively, and rejection rates of over 95.4% and 97.3% for Ca and Mg, respectively.

[0048] Example 4

[0049] The difference between this embodiment and embodiment 1 is that the extracting liquid in step (5) is a 0.5M SDBS solution, in order to study the feasibility of using SDBS as the extracting liquid.

[0050] The results are as follows Figure 6 As shown, by Figure 6 It was found that when 0.5M SDBS was used as the draw solution, the SDBS solution could generate a stable osmotic pressure above the critical micelle concentration. Due to the constant osmotic pressure, a stable FO flux could be maintained even if the draw solution concentration decreased. Meanwhile, the reverse salt flux was lower than that using sodium chloride as the draw solution, demonstrating the feasibility of using SDBS as the draw solution.

[0051] Example 5

[0052] The difference between this embodiment and embodiment 1 is that: in step (5), the feed liquid is the actual effluent from the secondary sedimentation tank of dyeing and printing wastewater, and the draw liquid is 0.5M NaCl. After a 10-hour membrane fouling experiment, the flux recovery experiment of the fouled membrane is carried out by modified microbubble-assisted cleaning. During the microbubble-assisted cleaning process, the solutions on the feed liquid and draw liquid sides are replaced with 1L of 0.5wt% NaOH + 0.1wt% SDBS mixed solution and 1L of ultrapure water, respectively. Microbubbles are introduced into the feed liquid side through a microbubble generator and cleaned in situ for 10-30 minutes. Then, the performance of the cleaned membrane is tested.

[0053] The results are as follows Figure 7 As shown, Figure 7 The results show that using modified microbubbles to assist cleaning can significantly affect the performance of fouled membranes, increasing flux recovery from 92.7% to 96.6% compared to cleaning with pure water alone. Figure 7 (b) It can be observed that the final water flux of the second cycle (6.89 LMH) of the unmodified fouled membrane is not significantly different from that of the first cycle (6.82 LMH), indicating that modified microbubble-assisted cleaning is more beneficial to the recovery of fouled membrane flux than cleaning with pure water alone. Introducing microbubbles can increase the agitation of fouling on the membrane surface, increase the shear rate along the membrane surface, and generate better hydrodynamics, which is conducive to the removal of dense fouling on the membrane surface, thereby improving membrane performance. The hydrolysis of NaOH and the solubilization of SDBS micelles both play important roles in the cleaning process.

[0054] The above embodiments are only preferred embodiments of the present application, and are not intended to limit the present application in any form and in essence. It should be noted that, for those skilled in the art, several improvements and supplements can be made without departing from the present application, and these improvements and supplements should also be considered as the protection scope of the present application.

Claims

1. A method for preparing an anti-fouling permeable membrane, characterized by, The method comprises the following steps: Step 1: mixing the dried PAN polymer, LiCl, UiO-66-(COOH)2 and NMP to form a casting solution; Step 2: laying PET non-woven fabric on a glass plate, degassing the casting solution obtained in step 1 and uniformly coating the non-woven fabric, using a doctor blade to prepare a base film, and then immediately immersing the base film in a water bath to perform a phase separation reaction to obtain a PAN / LiCl / UiO base film; Step 3: treating the PAN / LiCl / UiO base film obtained in step 2 with Ar plasma to improve the hydrophilicity of the film, then immersing the treated base film in a m-phenylenediamine aqueous solution, taking out and drying, and then immersing the base film in an isopar-G solution of trimesoyl chloride to perform an interfacial polymerization reaction to form a PA layer on the surface of the base film; Step 4: after the interfacial polymerization reaction, adding a polylysine solution for graft modification treatment, covalently reacting the amino groups on the polylysine molecules with the acyl chloride groups on the PA layer to form new amide bonds, and vacuum drying the film to improve the crosslinking degree of the PA to obtain a polylysine grafted PAN / LiCl / UiO anti-pollution permeation membrane, which comprises a PET non-woven fabric support layer, an Ar plasma modified PAN / LiCl / UiO matrix film and a PL covalently grafted and modified polyamide active layer; The mass percentage of PAN in the casting solution of step 1 is 12-15 wt%, the mass percentage of LiCl is 0.5-2.0 wt%, and the mass percentage of UiO-66-(COOH)2 is 0.025-0.1 wt%; The concentration of the polylysine solution in step 4 is 0.01-1.0 wt% PL, the polylysine solution is prepared by dissolving sodium hydroxide and polylysine hydrochloride PL·HCl in water, wherein w(NaOH) / w(PL·HCl)=0.20-0.40, and the treatment time is 10-30 min.

2. The method of claim 1, wherein the method is characterized by, The Ar plasma treatment conditions in step 3 are: under normal pressure, the voltage is 6-10 kV, the gas flow rate is 100-150 mL / min, and the treatment time is 10-60 s.

3. The application of the anti-pollution permeation membrane prepared by the method of any one of claims 1-2 in wastewater treatment.

4. A method for treating printing and dyeing wastewater and simultaneously recovering dyes and draw solution using the anti-fouling and permeable membrane prepared by the method according to any one of claims 1 to 2, characterized in that, It comprises: Using printing and dyeing wastewater as feed liquid and sodium dodecyl benzene sulfonate as stripping liquid, connecting a vibrating device to a membrane module comprising the anti-pollution permeation membrane to treat the printing and dyeing wastewater, and after the treatment of the anti-pollution permeation membrane, the concentrated feed liquid is recovered by extraction, and the used stripping liquid is directly used in the dyeing, finishing or refining process after dilution.

5. A process for treating printing and dyeing effluents and simultaneously recovering dyes and strippants according to claim 4, characterized in that, The concentration of the stripping liquid is 0.5-2 M, and the concentration after dilution is 1-10 wt%.

6. A process for treating printing and dyeing effluents and simultaneously recovering dyes and strippants according to claim 4, characterized in that, The method of cleaning the anti-pollution permeation membrane after operation by modifying micro-bubble assisted cleaning can remove the pollutants on the surface of the membrane and restore the membrane flux.

7. A process for treating printing and dyeing effluents and simultaneously recovering dyes and strippants according to claim 6, characterized in that, The specific method of the cleaning includes: using a mixed solution of 0.1-1 wt% NaOH and 0.1-0.5 wt% sodium dodecyl benzene sulfonate to modify the nano-bubbles, the average size of the nano-bubbles is 100-150 nm, the concentration is 7.5×10 7 ~8×10 7 ML, the modified micro-bubbles are introduced into the feed liquid side through a micro-bubble generator, and the contaminated membrane is cleaned, and the treatment time is 10-30 min.

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