阅读说明：本技术 一种利用氮化石墨烯复合纳米纤维膜光热光催化协同处理高盐有机废水的方法 (Method for photo-thermal photocatalytic co-treatment of high-salinity organic wastewater by using nitrided graphene composite nanofiber membrane ) 是由 代云容 郭星星 王思宇 高航 朱繁 于 2020-04-17 设计创作，主要内容包括：本发明属于污水处理领域,具体为一种利用氮化石墨烯复合纳米纤维膜光热光催化协同处理高盐有机废水的方法。该方法先以静电纺丝技术制备得到具有优良光吸收性能和光催化性能的氮化石墨烯复合纳米纤维膜,然后再将复合纤维膜覆盖于含有不同盐度和不同浓度有机污染物的高盐有机废水表面,在模拟太阳光下照射,同时实现光热蒸发脱盐和光催化去除有机污染物目的,收集的冷凝水中盐度和有机污染物的去除率均超过99.9％。该方法所制备的复合纳米纤维膜材料具有宽光谱吸收、脱盐效率高、快速去除有机污染物、稳定性强等特点,可广泛用于高盐水和海水淡化、工业高盐有机废水及含盐水净化等领域。(The invention belongs to the field of sewage treatment, and particularly relates to a method for photo-thermal photocatalytic co-treatment of high-salinity organic wastewater by using a graphene nitride composite nanofiber membrane. According to the method, the graphene nitride composite nanofiber membrane with excellent light absorption performance and photocatalytic performance is prepared by an electrostatic spinning technology, then the composite fiber membrane is covered on the surface of high-salt organic wastewater containing organic pollutants with different salinity and different concentrations, irradiation is carried out under simulated sunlight, the purposes of photo-thermal evaporation desalination and photocatalytic organic pollutant removal are achieved, and the salinity and organic pollutant removal rate in collected condensed water exceeds 99.9%. The composite nanofiber membrane material prepared by the method has the characteristics of wide spectral absorption, high desalting efficiency, rapid removal of organic pollutants, strong stability and the like, and can be widely used in the fields of high-salt water and seawater desalination, industrial high-salt organic wastewater purification, salt-containing water purification and the like.)

1. A method for treating high-salinity organic wastewater by utilizing photo-thermal photocatalysis of a graphene nitride composite nanofiber membrane is characterized by comprising the following two steps: preparing a nitrogenized graphene composite nanofiber membrane and carrying out photo-thermal photocatalytic synergistic treatment on high-salt organic wastewater by using the nitrogenized graphene composite nanofiber membrane;

the preparation method of the azotized graphene composite nanofiber membrane comprises the following steps:

1) adding polymer particles with a certain mass into a solvent, and stirring for 2 hours at a heating or normal temperature to obtain a transparent gel solution with a mass concentration of 6-9%;

2) weighing a certain mass of graphene nitride, adding the graphene nitride into the transparent gel solution obtained in the step 1), performing ultrasonic treatment for 120min under the condition of 20kHz, and then placing the solution on a magnetic stirrer to stir for 30min under the condition of 600rpm to obtain a uniform graphene nitride mixed gel solution;

3) introducing the mixed gel solution obtained in the step 2) into a high-voltage electrostatic spinning device, adjusting the power supply voltage to be 15-20 kV, setting the flow rate of the spinning solution to be 1m L/h and the receiving distance to be 15cm, and obtaining stable and continuous jet, wherein the temperature is controlled to be 25 +/-5 ℃ and the humidity is 35 +/-5% in the spinning process;

4) collecting a fiber film on an aluminum foil of a receiving plate, stopping spinning after the thickness of the fiber film reaches 0.10-0.15 mm after 6-8 hours, treating the obtained graphene nitride composite nanofiber film in a muffle furnace at 150-180 ℃ for 30min, and then cooling to room temperature for storage for later use;

the method for treating the high-salinity organic wastewater by utilizing the photo-thermal photocatalysis synergistic effect of the azotized graphene composite nanofiber membrane comprises the following steps:

a) the obtained graphene nitride composite nanofiber membrane is taken off from the aluminum foil and cut into a wafer with the diameter of 5 cm;

b) A300W xenon lamp is taken as a sunlight light source simulator, an AM 1.5 optical filter is added for simulating solar radiation, and the illumination intensity is determined to be 1kW/m through an optical power meter²；

c) Measuring 100m L simulated high-salt organic wastewater containing organic pollutants with different concentrations and different salinity in a glass beaker, covering the whole water surface with a graphene nitride composite nanofiber membrane, and standing in simulated sunlight to start reaction;

d) and collecting the evaporated condensate water, sampling at regular time, analyzing the salinity and the organic matter concentration in the condensate water, and determining the water yield.

2. The method for the photo-thermal photocatalytic co-treatment of the high-salinity organic wastewater by using the graphene nitride composite nanofiber membrane as claimed in claim 1, wherein the method comprises the following steps: the preparation method of the nitrogenated graphene composite nanofiber membrane comprises the step 1) of preparing the nitrogenated graphene composite nanofiber membrane by using a polymer which is one of polyvinyl alcohol, polylactic acid, polyvinylidene fluoride, polycaprolactone and polystyrene, and using a solvent which is one of water, N-dimethylformamide, dichloromethane and dimethyl sulfoxide.

3. The method for the photo-thermal photocatalytic co-treatment of the high-salinity organic wastewater by using the graphene nitride composite nanofiber membrane as claimed in claim 1, wherein the method comprises the following steps: the mass of the azotized graphene added in the step 2) of preparing the azotized graphene composite nanofiber membrane is 1-5% of that of the polymer.

4. The method for the photo-thermal photo-catalytic co-treatment of the high-salt organic wastewater by using the graphene nitride composite nanofiber membrane as claimed in claim 1, wherein the organic pollutants in the simulated high-salt organic wastewater in the step c) of the photo-thermal photo-catalytic co-treatment of the high-salt organic wastewater by using the graphene nitride composite nanofiber membrane comprise one or more of benzene, dichlorophenol, methylene blue, triclosan and bisphenol A, the concentration range is 1-10 mg/L, and the salinity is 1-10% by mass concentration of NaCl.

5. The method for the photothermal photocatalytic co-treatment of high-salt organic wastewater by using the graphene nitride composite nanofiber membrane as claimed in claim 1, wherein the concentration of Na ions in the condensed water in the step d) of the photothermal photocatalytic co-treatment of high-salt organic wastewater by using the graphene nitride composite nanofiber membrane is lower than 0.8 mg/L, the concentration of organic pollutants is lower than 5 μ g/L, and the water yield is 1.2 ℃1.6kg/m²/h。

Technical Field

The invention belongs to the field of sewage treatment, particularly relates to the field of high-salinity organic wastewater treatment, and particularly relates to a method for treating high-salinity organic wastewater by utilizing photo-thermal photocatalysis of a graphene nitride composite nanofiber membrane.

Background

The high-salt organic wastewater refers to wastewater with the organic matter Content (COD) of more than 10000 mg/L and the mass fraction of total dissolved solid TDS of more than or equal to 3.5 percent (or the salt mass fraction of sodium chloride of more than 1 percent), and generally comes from the industries of chemical industry, energy, metallurgy, electroplating, printing and dyeing, coking, food processing and the like.

The treatment of high-salt organic wastewater has been the focus of attention in the field of industrial water treatment. The current treatment methods mainly include physical methods such as evaporation, incineration, membrane separation, adsorption, etc.; chemical methods such as ion exchange, precipitation, advanced oxidation, etc.; and biological methods such as an activated sludge method and a biofilm method. The evaporation method is simple to operate, partial water in the high-salinity organic wastewater can be vaporized at a relatively low temperature (50-150 ℃), solid-liquid separation is realized, and the salt in the wastewater is efficiently removed. Therefore, evaporation technologies such as Membrane Distillation (MD), flash evaporation (MSF), multiple effect evaporation (MED), mechanical compression evaporation (MVR), etc. are widely used in practical high-salt organic wastewater treatment. However, the high-salt organic wastewater discharged by most industrial industries contains a large amount of volatile or semi-volatile organic compounds, and in the evaporation treatment process, the organic compounds enter distilled water through volatilization and entrainment, so that high-concentration organic compounds exist in the distilled water, and other technologies are needed for further treatment. Therefore, the evaporation method is generally used as a pretreatment process of high-salt organic wastewater, and a mode of dividing and treating high-salt and organic pollution is mostly adopted in process development, so that the process is complicated, and the defects related to a single process are brought. Therefore, how to synchronously perform phase-change separation desalination and harmless organic matter degradation and to 'combine and treat' high salinity and organic pollutants is a research hotspot in the field of high-salinity organic wastewater treatment in recent years and is also needed by the industry.

In recent years, the advent and rapid development of the concept of interfacial heating and the theory of simulated transpiration have led to great interest in photothermal desalination. The photothermal desalination technology can convert light energy into heat energy by means of a photothermal conversion material, and carries out local heating evaporation on an air-water interface, so that the desalination of high-salinity organic wastewater is realized, and the photothermal desalination technology has the advantages of low energy consumption, mild reaction conditions, high effluent quality and the like. The conventional photothermal conversion material can only realize the separation of inorganic pollutants such as salt, particles and the like, and lacks the treatment capacity on organic matters in wastewater. If the photo-thermal conversion material is endowed with the photo-catalytic performance, the photo-thermal technology and the photo-catalytic technology are cooperated, and the removal of salt and organic matters can be realized simultaneously. Although the photothermal and photocatalytic processes differ in the energy conversion pathway and the action object, both are based on the absorption and conversion of light energy, and can be theoretically achieved simultaneously on one material. The nitrogenated graphene is a novel graphene-based material, and nitrogen atoms are introduced into the edge and defect positions of the graphene, so that an active region which can directly participate in catalytic reaction is generated. The high specific surface area and catalytic activity enable the graphene to have certain adsorption removal performance on organic pollutants, so that the nitrided graphene has greater advantages in the fields of photo-heat and photocatalysis.

The high-voltage electrostatic spinning technology is a novel technology for preparing a nanofiber membrane. The technology realizes the processing of the superfine fiber membrane by utilizing the jet flow of polymer solution or melt with charges in an electrostatic field, the diameter of the prepared fiber is 1 to 2 orders of magnitude smaller than that of the common fiber prepared by the traditional method, the void ratio is high, the specific surface area is large, the structure is compact, and the mechanical strength is certain. Therefore, by means of the flexible and adjustable characteristic of the electrostatic spinning technology, the technology can uniformly disperse the graphene nitride in the fiber, so that the tensile property of the fiber is enhanced, and meanwhile, the fiber yarns with compact structures can tightly combine the graphene nitride in the fiber, so that the photo-thermal and photocatalytic activities of the graphene nitride can be enhanced while the loss of nano particles is prevented. The nitride graphene composite material in the form of the nanofiber membrane can take high-efficiency photothermal desalination and photocatalytic degradation into consideration to remove organic matters, and the practicability of the nitride graphene and the electrospun fiber membrane in the field of environmental water treatment is remarkably improved.

Disclosure of Invention

The invention aims to provide a method for photo-thermal photocatalytic synergistic treatment of high-salinity organic wastewater by using a graphene nitride composite nanofiber membrane, namely, the graphene nitride composite nanofiber membrane prepared by using an electrostatic spinning technology is used as a photo-thermal conversion and photocatalytic dual-functional material, so that photo-thermal desalination can be realized under sunlight, and organic pollutants adsorbed on the fiber membrane or escaped along with steam are degraded through photocatalysis. The azotized graphene composite nanofiber membrane adopted by the method has the advantages of good stability, simple preparation process, high photo-thermal conversion efficiency, obvious photo-catalytic effect, easiness in recycling and the like; and the method is environment-friendly, easy to operate, economical and efficient.

The technical scheme of the invention is as follows:

according to the method for removing high-salinity organic wastewater by photo-thermal photocatalysis cooperation, the nitrided graphene with wide spectrum absorption capacity and photo-thermal conversion capacity is used as a light absorber and a photocatalyst, the nitrided graphene is fixed in the nanofiber by an electrostatic spinning technology to prepare the nitrided graphene composite nanofiber membrane, and then the composite nanofiber membrane is used for photo-thermal desalination and pollutant catalytic degradation to obtain clean condensate water. The method comprises two steps: preparation of the azotized graphene composite nanofiber membrane and photo-thermal photocatalytic synergistic treatment of high-salt organic wastewater by using the azotized graphene composite nanofiber membrane.

The preparation method of the azotized graphene composite nanofiber membrane comprises the following steps:

1) adding polymer particles with a certain mass into a solvent, and stirring for 2 hours at a heating or normal temperature to obtain a transparent gel solution with a mass concentration of 6-9%;

2) weighing a certain mass of graphene nitride, adding the graphene nitride into the transparent gel solution obtained in the step 1), performing ultrasonic treatment for 120min under the condition of 20kHz, and then placing the solution on a magnetic stirrer to stir for 30min under the condition of 600rpm to obtain a uniform graphene nitride mixed gel solution;

3) introducing the mixed gel solution obtained in the step 2) into a high-voltage electrostatic spinning device, adjusting the power supply voltage to be 15-20 kV, setting the flow rate of the spinning solution to be 1m L/h and the receiving distance to be 15cm, and obtaining stable and continuous jet, wherein the temperature is controlled to be 25 +/-5 ℃ and the humidity is 35 +/-5% in the spinning process;

4) collecting a fiber film on an aluminum foil of a receiving plate, stopping spinning after the thickness of the fiber film reaches 0.10-0.15 mm after 6-8 hours, treating the obtained graphene nitride composite nanofiber film in a muffle furnace at 150-180 ℃ for 30min, and then cooling to room temperature for storage for later use;

the method for treating the high-salinity organic wastewater by utilizing the photo-thermal photocatalysis synergistic effect of the azotized graphene composite nanofiber membrane comprises the following steps:

a) the obtained graphene nitride composite nanofiber membrane is taken off from the aluminum foil and cut into a wafer with the diameter of 5 cm;

b) A300W xenon lamp is taken as a sunlight light source simulator, an AM 1.5 optical filter is added for simulating solar radiation, and the illumination intensity is determined to be 1kW/m through an optical power meter²；

c) Measuring 100m L simulated high-salt organic wastewater containing organic pollutants with different concentrations and different salinity in a glass beaker, covering the whole water surface with a graphene nitride composite nanofiber membrane, and standing in simulated sunlight to start reaction;

d) and collecting the evaporated condensate water, sampling at regular time, analyzing the salinity and the organic matter concentration in the condensate water, and determining the water yield.

In the method, the polymer in the step 1) for preparing the nitrogenated graphene composite nanofiber membrane is one of polyvinyl alcohol, polylactic acid, polyvinylidene fluoride, polycaprolactone and polystyrene, and the solvent is one of water, N-dimethylformamide, dichloromethane and dimethyl sulfoxide.

The mass of the azotized graphene added in the step 2) of preparing the azotized graphene composite nanofiber membrane is 1-5% of that of the polymer. Within the range, the higher the content of the nitrogenated graphene is, the stronger the photothermal desalination and photocatalytic degradation performance of the composite nanofiber membrane on organic pollutants is. When the content exceeds 5%, the agglomeration phenomenon of the azotized graphene is subjected to polyaddition, the spinning process becomes difficult, more liquid drops exist in the collected fiber, the mechanical strength of the fiber membrane is obviously reduced, and the photo-thermal and photo-catalytic properties are not obviously improved. Therefore, the optimal graphene nitride content in the composite nanofiber membrane is 5%.

The obtained graphene nitride composite nanofiber membrane is placed in a muffle furnace for heat treatment, so that the stability and the light absorption performance of the graphene nitride composite nanofiber membrane can be enhanced; the light absorption range can extend from the ultraviolet band to the near infrared band, the absorption efficiency of the composite nanofiber membrane to the simulated sunlight under the wet state can reach more than 90 percent, the absorbed light energy can be efficiently converted into heat energy, the surface temperature of the dry-state composite membrane can reach more than 100 ℃, the temperature of the wet-state composite membrane can also reach more than 50 ℃, and the photothermal conversion efficiency can reach as high as 92.3 percent.

The azotized graphene composite material in the form of the nanofiber membrane can uniformly disperse azotized graphene in fibers, so that secondary pollution caused by loss of nanoparticles can be prevented, the tensile property of the fibers can be enhanced, the mechanical strength of the composite membrane is improved, and the photo-thermal and photocatalytic activities of the composite membrane can be enhanced. More importantly, the forming material of the electrospinning nano-fiber can be hydrophilic polymer or hydrophobic polymer, if the hydrophobic polymer is formed into filaments, the micron-level gap formed by the mutual lapping of the fibers can play a role in capillary water drawing, so that the continuous water supply is ensured, and the electrospinning nano-fiber is also suitable for being used as a channel for water vapor transmission; meanwhile, volatile organic compounds escaping along with the evaporation of water vapor tend to be adsorbed on the surface of the fiber, the average free path of the azotized graphene photon-generated carriers is shortened, the azotized graphene photon-generated carriers are fully reacted with photocatalytic active species, and efficient and thorough degradation is realized. In addition, the photo-thermal desalting can enhance the reaction rate and efficiency of the whole system for photo-catalytically degrading various organic pollutants through the photo-thermal effect, and realize the high-efficiency treatment and recycling of the high-salinity organic wastewater.

The method for simulating the photo-thermal photocatalytic co-treatment of the high-salinity organic wastewater by using the graphene nitride composite nanofiber membrane in the step c) comprises the step of simulating one or more organic pollutants in the high-salinity organic wastewater, wherein the concentration range of the organic pollutants comprises 1-10 mg/L of benzene, dichlorophenol, methylene blue, triclosan and bisphenol A, the salinity is 1-10% by mass concentration of NaCl, after the photo-thermal photocatalytic co-treatment of the graphene nitride composite nanofiber membrane, the salinity in collected condensed water is lower than 0.8 mg/L, the concentration of the organic pollutants is lower than 5 mu g/L, and the water production rate is 1.2-1.6 kg/m²/h。

The photo-thermal photocatalytic co-treatment method for high-salinity organic wastewater provided by the invention has the following advantages:

1. the preparation process of the photo-absorber graphene nitride composite nanofiber membrane adopted by the method is simple, the polymer electrospun fiber membrane can provide a carrier for nanoscale powder graphene nitride, and the mechanical property, the photo-thermal property and the photocatalytic property of the electrospun fiber membrane can be obviously improved by adding the graphene nitride, so that the composite fiber membrane has the advantages of wide spectrum absorption, high-efficiency catalytic degradation property, environmental friendliness, easiness in recycling and the like.

2. The method for photo-thermal photocatalytic co-treatment of high-salt organic wastewater by using the nitrogenized graphene composite nanofiber membrane is simple to operate, mild in condition, low in cost and beneficial to popularization and application.

3. The azotized graphene composite nanofiber membrane has good light absorption performance, strong heating capacity and ideal desalting effect, is suitable for treating salt-containing wastewater with different salinity, and can effectively degrade organic pollutants through the photocatalysis performance of azotized graphene. Moreover, polymers of different materials can be replaced or different types and quantities of nitrided graphene can be added to realize the regulation and control of the overall performance of the composite nanofiber membrane.

Drawings

In order to more clearly illustrate the embodiments of the present invention, the drawings used in the description of the embodiments section below are briefly described.

FIG. 1 is a scanning electron microscope image of a polyvinyl alcohol nano electrospun fiber membrane (a) and a polyvinyl alcohol/graphene nitride composite nano electrospun fiber membrane (b);

fig. 2 is an ultraviolet-visible-near infrared absorption and reflection spectrum of the polyvinyl alcohol/graphene nitride composite nanofiber film;

FIG. 3 is a diagram showing the temperature changes of the membrane surface and the water body when the polyvinyl alcohol/graphene nitride composite nanofiber membrane is used for treating high-salt organic wastewater;

FIG. 4a shows the concentration changes of Na ions and organic pollutants in condensed water before and after the photo-thermal photocatalytic treatment of a simulated high-salt organic wastewater composed of NaCl, benzene, methylene blue and triclosan by using a polyvinyl alcohol/graphene nitride composite nanofiber membrane; FIG. 4b shows the concentration changes of Na ions and organic pollutants in condensate water before and after the photo-thermal photocatalytic treatment of a simulated high-salinity organic wastewater composed of NaCl, dichlorophenol, methylene blue and bisphenol A by the polyvinyl alcohol/graphene nitride composite nanofiber membrane; fig. 4c shows the concentration changes of Na ions and organic pollutants in condensed water before and after the simulated high-salt organic wastewater composed of NaCl, benzene, triclosan and bisphenol a is processed by the polyvinyl alcohol/graphene nitride composite nanofiber membrane through photo-thermal photocatalysis.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.