Background
The ultrafiltration membrane can consume more energy and have serious consequences of membrane replacement after being polluted, and membrane pollutants comprise organic pollutants, colloid pollutants, biological pollutants and the like, wherein the influence of the biological pollutants on the membrane is most critical. In the five steps of the biofilm formation mechanism, biofouling rapidly increases energy consumption resulting in an increase in permeation costs of the fouled membrane, and irreversible attachment of biofouling inevitably results in a reduction in the membrane application cycle.
With the increasing use of polymer membranes in water and wastewater treatment, there have been some solutions to reduce biological contamination and the like in the prior art, and the solutions to mitigate biological contamination are divided into process control and membrane modification.
Where process control, e.g., optimization of operating conditions, has a large impact on membrane biofouling mitigation, the carefully designed pretreatment portion plus timely backwashing and chemical cleaning will extend the membrane's useful life and minimize additional operating costs. However, such professional water purification requires a large initial investment and, in addition, an experienced operator supervision device to provide an optimized operation of the water purification device.
In addition, the modification of membranes has been studied in the last decade mainly on mixing, grafting and coating, the principle being to add both antibacterial and anti-adhesion core functions in membrane manufacture, but the modifying effect of such membranes is not significant.
Therefore, in the last fifty years of membrane development, membrane replacement is the more choice in industrial applications, but this has the problem of higher cost.
Disclosure of Invention
The technical problem to be solved by the present invention is to provide an ultrafiltration membrane with fluorescence monitoring function and a preparation method thereof, which can effectively and reliably reduce the influence of biological pollution on membrane application and prolong the practical life of the membrane, aiming at the defects in the prior art.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows:
a preparation method of an ultrafiltration membrane with a fluorescence monitoring function comprises the following steps:
s01, mixing and dissolving polyether sulfone, polyvinylpyrrolidone and tetraphenyl ethylene into N-methyl pyrrolidone to form a casting film solution;
s02, carrying out ultrasonic treatment on the casting film solution obtained in the S01 until no condensate exists in the casting film solution;
s03, taking the glass plate as a support layer for the casting film solution treated by the ultrasonic treatment in the S02, carrying out film scraping treatment of wet phase conversion, and exposing the film in the air after the film scraping is finished;
s04, the glass plate carrying the casting film solution in S03 is soaked in water.
In S01, the proportions of polyether sulfone, polyvinylpyrrolidone, tetraphenylethylene and N-methylpyrrolidone are 16%, 4%, 0.1-5% and 75-79.9% by mass, respectively.
In S02, the ultrasonic treatment is specifically carried out by ultrasonic bath treatment at 40kHz for 5 minutes and then ultrasonic treatment with an ultrasonic probe for 1 minute.
In S03, the film scraping treatment is specifically to scrape the film with the thickness of 150 μm, control the film forming speed to be 8 cm/min, and the time of exposure to the air after the film scraping is finished is 1 min.
In S04, the glass plate is soaked in water for 16-24 h.
The ultrasonic treatment comprises three cycles of the steps, the cycle setting intervals are respectively 1h, 9h and 17h, and standing is carried out for 7h after the ultrasonic treatment is finished.
An ultrafiltration membrane with a fluorescence monitoring function, which is prepared by any one of the preparation methods.
The invention has the beneficial effects that: the invention provides an ultrafiltration membrane with a fluorescence monitoring function and a preparation method thereof. The produced ultrafiltration membrane has good biological fouling sensitivity, can give an alarm in time in household or industrial application, and further optimizes the service life of the membrane component by cleaning in time. Less expense is required due to the improvement and the processability of the mixture is very similar to a classical PESUF film. Therefore, the ultrafiltration membrane capable of monitoring biological pollution in real time can be applied as a new generation of intelligent membrane for water treatment, and the reliability of a water purification system is improved.
Detailed Description
The present invention is further described with reference to the accompanying drawings, and the following examples are only for clearly illustrating the technical solutions of the present invention, and should not be taken as limiting the scope of the present invention.
Detailed description of thepreferred embodiment 1
The invention discloses a preparation method of an ultrafiltration membrane with a fluorescence monitoring function, which adopts polyether sulfone (PES) as a membrane matrix, polyvinylpyrrolidone (PVP) as a cross-linking agent and N-methyl pyrrolidone (NMP) as a solvent, and adds tetraphenyl ethylene (TPE) with a fluorescence function, and specifically comprises the following steps:
step one, polyether sulfone, polyvinylpyrrolidone and tetraphenyl ethylene are mixed and dissolved into N-methyl pyrrolidone to form a casting film solution, wherein the proportion fractions of the polyether sulfone, the polyvinylpyrrolidone, the tetraphenyl ethylene and the N-methyl pyrrolidone are respectively 16%, 4%, 0.1-5% and 75-79.9% by mass, and the preferred proportions are 16g of polyether sulfone, 4g of polyvinylpyrrolidone, 0.1g of tetraphenyl ethylene and 79.9g of N-methyl pyrrolidone.
And step two, carrying out ultrasonic treatment on the casting film solution obtained in the step one until no condensate exists in the casting film solution, so that all components in the solution are uniformly dispersed. The ultrasonic treatment is specifically carried out by ultrasonic bath treatment at 40kHz for 5 minutes and then ultrasonic treatment with an ultrasonic probe for 1 minute. The steps are circulated for 3 times in total, the circulation setting intervals are respectively 1h, 9h and 17h, and standing is carried out for 7h after the ultrasonic treatment is finished, so that the high-concentration organic solute can be fully and uniformly dissolved in the organic solvent.
And step three, taking a clean glass plate as a supporting layer for the casting film solution subjected to ultrasonic treatment in the step two, performing wet-phase conversion film scraping treatment, and exposing the film in the air after the film scraping is finished. The film scraping treatment is specifically to scrape the film with the thickness of 150 μm, control the film forming speed to be 8 cm/min, and expose the film to the air for 1min after the film scraping is finished.
And step four, soaking the glass plate loaded with the casting film solution in the step three in water for 16-24 hours, so as to volatilize the N-methylpyrrolidone from the water.
An ultrafiltration membrane with a fluorescence monitoring function is prepared by the preparation method. The SEM image is shown in figure 1,
specific example 2
This example is the same as example 1, except that in step one, it is preferably 16g of polyethersulfone, 4g of polyvinylpyrrolidone, 0.2g of tetraphenylethylene and 79.8g of N-methylpyrrolidone.
Specific example 3
This example is the same as example 1, except that in step one, it is preferably 16g of polyethersulfone, 4g of polyvinylpyrrolidone, 0.5g of tetraphenylethylene and 79.5g of N-methylpyrrolidone.
Specific example 4
This example is the same as example 1, except that in step one, it is preferably 16g of polyethersulfone, 4g of polyvinylpyrrolidone, 1g of tetraphenylethylene and 79g of N-methylpyrrolidone.
Specific example 5
This example is the same as example 1, except that in step one, it is preferably 16g of polyethersulfone, 4g of polyvinylpyrrolidone, 2g of tetraphenylethylene and 78g of N-methylpyrrolidone.
Specific example 6
This example is the same as example 1, except that in step one, it is preferably 16g of polyethersulfone, 4g of polyvinylpyrrolidone, 51g of tetraphenylethylene and 75g of N-methylpyrrolidone.
As shown in FIG. 2, we tested the fluorescence emission intensity of the ultrafiltration membrane emitted by ultraviolet light irradiation when the ultrafiltration membrane prepared by the present invention adsorbs Bovine Serum Albumin (BSA) under different conditions, including tetraphenyl ethylene with different ratio fractions, Bovine Serum Albumin (BSA) concentrations with different concentrations, and different adsorption times. From the figure, it can be seen that the fluorescence emission intensity of the ultrafiltration membrane becomes stronger as the fractional fraction of tetraphenylethylene is increased under the condition that the adsorption time and the concentration of Bovine Serum Albumin (BSA) are unchanged. The maximum solubility of tetraphenylethylene in N-methylpyrrolidone solvent is 5 wt%, and above this fraction tetraphenylethylene is not homogeneously dissolved, so that ultrafiltration membranes were prepared having the most sensitive effect on the monitoring of biofouling adsorption at a mass concentration of tetraphenylethylene of 5 wt%.
Biological pollutants are attached to the ultrafiltration membrane mainly through two processes, when the reversible ultrafiltration membrane is attached to the biological pollutants in the early stage, the biological pollutants can be removed from the ultrafiltration membrane through a flushing mode, regeneration and reuse of the ultrafiltration membrane are achieved, adsorption of the biological pollutants by the ultrafiltration membrane in the later stage is changed into irreversible, and regeneration of the ultrafiltration membrane cannot be achieved through the flushing mode in the later stage. Therefore, the operation of the ultrafiltration membrane can be stopped at the later stage of reversible adsorption of the biological pollutants by the ultrafiltration membrane, and then the regeneration of the ultrafiltration membrane can be realized by flushing. In the prior art, although the process of adsorbing biological pollutants by the ultrafiltration membrane can be monitored and judged manually, the judgment is subjective, time-consuming and labor-consuming. According to the ultrafiltration membrane with the fluorescence monitoring function, the tetraphenylethylene is added into the existing ultrafiltration membrane, the filtering function of the existing ultrafiltration membrane is not influenced, and under the irradiation of ultraviolet light, the tetraphenylethylene can emit fluorescence with different intensities according to the amount of biological pollutants adsorbed on the ultrafiltration membrane, so that whether the stage needing flushing and regeneration is reached is judged, and the monitoring mode is reliable. Furthermore, the ultrafiltration membrane prepared by the method can be used together with a fluorescence detector and a computer to realize intelligent monitoring.
In addition, the ultrafiltration membrane prepared by the invention has small agglomeration of TPE particles even under high load, and the filtering process of the ultrafiltration membrane cannot be influenced. The proper affinity of TPE to the film matrix prevents secondary contamination of films doped with TPE dopants. The high stability of the TPE particles in the PES matrix can avoid environmental pollution and can also ensure the lifetime luminescence of the filter membrane.
The above description is only of the preferred embodiments of the present invention, and it should be noted that: it will be apparent to those skilled in the art that various modifications and adaptations can be made without departing from the principles of the invention and these are intended to be within the scope of the invention.