CN-121972035-A - Perfluoro compound interception negatively charged nanofiltration membrane based on PAA grafting and preparation method thereof

CN121972035ACN 121972035 ACN121972035 ACN 121972035ACN-121972035-A

Abstract

The invention discloses a perfluoro compound interception negative charge nanofiltration membrane based on PAA grafting and a preparation method thereof, and the perfluoro compound interception negative charge nanofiltration membrane comprises the steps of basal membrane pretreatment, basal membrane cleaning and activation, preparation of pretreatment mixed solution containing acrylic acid and glutaraldehyde, pre-grafting reaction, interfacial polymerization, preparation of aqueous phase solution containing 1.3-1.5wt% PIP+0.1-0.14wt% TAP+0.14-0.18wt% PEG+0.8-1.2wt% GA+0.03-0.05 wt% SDBS, preparation of oil phase solution, polymerization reaction, surface activation, membrane immersing in 0.04-0.06 wt% NaOH solution after interfacial polymerization, and surface grafting functional layer, preparation of grafting mixed solution containing acrylic acid and glutaraldehyde, and surface grafting reaction. The invention realizes the multi-dimensional performance improvement of the nanofiltration membrane with high selectivity, high flux, high stability and wide adaptability, and meets the requirements of complex water quality treatment and accurate separation of mono-ion and divalent ion.

Inventors

CHEN DONGGEN
XU YINONG
LI ZHONGHUA
ZHANG KAN
LIU PENG
YIN MIAOMIAO
LI ZEDONG
LIU RUI

Assignees

浙江津膜环境科技有限公司

Dates

Publication Date: 20260505
Application Date: 20260408

Claims (10)

1. The preparation method of the perfluorinated compound interception negatively charged nanofiltration membrane based on PAA grafting is characterized by comprising the following steps: S1, pretreatment of a base film Comprises the steps of cleaning and activating a base film, preparing a pretreatment mixed solution and carrying out a pre-grafting reaction; Wherein the pretreatment mixed solution comprises acrylic acid and glutaraldehyde; pre-grafting reaction, namely immersing the surface activated base film into a pre-treatment mixed solution to enable glutaraldehyde to simultaneously crosslink hydroxyl groups and acrylic carboxyl groups of the base film and reserve part of aldehyde groups; S2, interfacial polymerization Comprises the steps of water phase solution preparation, oil phase solution preparation and polymerization reaction; The preparation method comprises the steps of sequentially adding 1.3-1.5 wt% of piperazine, 0.1-0.14 wt% of triaminopyrimidine and 0.14-0.18 wt% of polyethylene glycol-1000 into deionized water, stirring and uniformly mixing, adding 0.8-1.2 wt% of glutaraldehyde and 0.03-0.05 wt% of sodium dodecyl benzene sulfonate before membrane preparation, and continuously stirring and uniformly mixing; the polymerization reaction, namely tiling the pretreated base film, and pouring an aqueous phase solution and an oil phase solution in sequence; s3, surface activation The surface activation of polyamide, namely immersing the film subjected to interfacial polymerization into 0.04-0.06 wt% NaOH solution, standing for 10-20 min at 20-30 ℃, and flushing to neutrality; S4, grafting a functional layer on the surface layer Comprises the steps of preparing grafting mixed solution and carrying out surface grafting reaction; the grafting mixed solution comprises acrylic acid and glutaraldehyde; And (3) surface grafting reaction, namely immersing the membrane subjected to surface activation into a grafting mixed solution to enable glutaraldehyde to bridge polyamide amino and acrylic acid, so as to construct the PAA grafting functional layer.
2. The preparation method of the PAA grafted perfluoro compound interception negatively charged nanofiltration membrane according to claim 1 is characterized in that in the step S1, a polysulfone ultrafiltration base membrane is taken and ultrasonically cleaned for 5-15 min, immersed in 0.4wt% -0.6wt% NaOH solution, kept at 20-30 ℃ for 15-25 min, hydroxyl groups on the surface of the base membrane are activated, and the base membrane is washed to be neutral and drained.
3. The preparation method of the PAA grafted perfluoro compound interception negatively charged nanofiltration membrane according to claim 1 is characterized in that in the step S1, the pretreatment mixed solution is prepared by adding 1.5-2 wt% of acrylic acid and 0.3-0.5 wt% of glutaraldehyde into deionized water, and magnetically stirring for 1-10 min.
4. The method for preparing the PAA grafted perfluoro compound interception negatively charged nanofiltration membrane according to claim 1, wherein in the step S1, the pre-grafting reaction is carried out, when the surface activated base membrane is immersed in the pretreatment mixed solution, the surface activated base membrane is sealed and kept stand for 1-3 hours at 20-30 ℃, and is taken out, washed by deionized water and naturally dried.
5. The method for preparing the PAA grafted perfluoro compound interception negative nanofiltration membrane according to claim 1, wherein in the step S2, the oil phase solution is prepared by preparing an n-hexane solution containing 0.12-0.15 wt% TMC, and performing ultrasonic dispersion for 1-10 min.
6. The preparation method of the PAA grafted perfluoro compound interception negative nanofiltration membrane according to claim 1 is characterized in that in the step S2, the pretreated base membrane is tiled, aqueous phase solution is poured, the base membrane is kept stand for 1-5 min at 20-30 ℃, redundant aqueous phase is poured out, nitrogen is purged and air-dried, oil phase solution is immediately poured, the base membrane is reacted for 0.5-1.5 min at 20-30 ℃, oil phase is poured out, and natural air-drying is performed.
7. The method for preparing the PAA grafted perfluoro compound interception negative nanofiltration membrane according to claim 1, wherein in the step S4, 6-7wt% of acrylic acid and 1.5wt% to 2wt% of glutaraldehyde are added into deionized water for preparation of a grafting mixed solution, and the mixture is stirred uniformly.
8. The method for preparing the PAA grafted perfluoro compound interception negatively charged nanofiltration membrane according to claim 1, wherein in the step S4, the surface layer grafting reaction is carried out, when the membrane after surface activation is immersed in the grafting mixed solution, the membrane is sealed and kept stand for 1-2 hours at 20-30 ℃, and the membrane is taken out, washed by clean water and naturally dried.
9. The method for preparing a PAA graft-based perfluorinated compound entrapping negatively charged nanofiltration membrane according to claim 1, further comprising the steps of: s5, cleaning and preserving Immersing the membrane into deionized water to hydrate the PAA grafting functional layer, taking out the membrane to absorb the surface moisture for use, and sealing and immersing the membrane in the deionized water at 2-5 ℃ for long-term storage.
10. A PAA-grafted perfluoro compound trapping negatively charged nanofiltration membrane, characterized in that the nanofiltration membrane is prepared by the PAA-grafted perfluoro compound trapping negatively charged nanofiltration membrane preparation method according to any one of claims 1 to 9.

Description

Perfluoro compound interception negatively charged nanofiltration membrane based on PAA grafting and preparation method thereof Technical Field The invention relates to the technical field of nanofiltration membrane materials, in particular to a perfluorinated compound interception negatively charged nanofiltration membrane based on PAA grafting and a preparation method thereof. Background The separation performance of nanofiltration membranes depends on the synergistic effect of pore size sieving plus charge effect, wherein the surface negative charge density is critical for improving the interception capability of negative electric pollutants and divalent cations. In the prior art, the method for improving the negative charge on the surface of the membrane mainly comprises the steps of introducing functional groups such as carboxyl, sulfonic group and the like, but has certain limitations. Firstly, a carboxyl-containing monomer is added during the modification of a single functional monomer only through interfacial polymerization, so that the negative charge density is limited, the performance is easy to be attenuated due to the falling of groups, and negative charge substances are introduced into the physical coating modification through an adsorption or deposition mode, so that the interlayer binding force is weak, the falling is easy to occur under the flushing of water flow, and the stability is insufficient. Polyacrylic acid (PAA) is a water-soluble anionic polymer, the molecular formula is (C 3H4O2)n, the relative molecular weight can be regulated and controlled as required, carboxyl functional groups are densely distributed on a linear molecular main chain of the PAA, the PAA has strong water solubility, can be covalently crosslinked with aldehydes or amino groups, can keep stable structure in a wide-range environment with pH of 3-11, and can provide stable negative charge for materials under neutral and alkaline conditions. Chinese patent publication No. CN113877268a discloses a preparation method of a high-charge nanofiltration membrane, which introduces negative charges by adding sulfonated monomers into a water phase, but does not adopt a gradient grafting process, the negative charges are unevenly distributed, and a through cross-linked network is not constructed, so that the long-term running stability is insufficient. Chinese patent publication No. CN114524863A proposes a nanofiltration membrane preparation method containing polyethylene glycol chains, which focuses on flux improvement through a pore-forming agent, but does not optimize negative charge density, has a rejection rate of less than 85% on negative charge pollutants, and cannot meet high-requirement treatment scenes. In summary, the prior art also has the following drawbacks: 1. The charge regulation and control unbalance is that the existing nanofiltration membrane generally has the problems of insufficient negative charge density or uneven distribution, so that the screening difference of divalent cations and monovalent cations is small, the ion selectivity is low, the accurate separation is difficult to realize, meanwhile, the charge groups are easy to fall off or are unstable in ionization, the separation performance attenuation is obvious after long-term operation, and the long-term use requirement of a high-requirement scene cannot be met. 2. The interlayer bonding is weak, namely the base film is mostly physically adsorbed or partially covalently bonded with the functional layer and the functional layer is partially covalently bonded with the surface modification layer, and a stable cross-linked network with penetrability is lacking, so that interlayer stripping is easy to occur under the actual running conditions of water flow flushing, pressure fluctuation and the like, and the flux and interception performance are synchronously deteriorated. 3. The structure stability is insufficient, a perfect three-dimensional crosslinking system is not formed, the swelling resistance is poor, the membrane pore structure is easy to deform in different pH environments, temperature fluctuation or chemical mediums, the pore size distribution is widened, the separation precision is reduced, and meanwhile, membrane pollution accumulation is easy to occur in long-term operation, so that the performance attenuation is further aggravated. 4. The preparation method has the advantages of poor process cooperativity, difficulty in realizing the cooperative optimization of high flux, high selectivity and high stability, imbalance of poor selectivity and low flux caused by high flux, insufficient suitability of preparation process parameters, high sensitivity to reaction conditions and difficulty in guaranteeing repeatability and stability in large-scale production. 5. The environment adaptability is limited, the adaptation capability to complex water quality and wide pH range is weak, the separation performance is easy to fluctuate greatly due to