A method for preparing a wheat straw / geo-polymer composite carbonized membrane for water purification technology

Abstract

This invention relates to the field of water purification and water resource recycling technology, specifically to a biopolymer carbonized membrane, which is made of wheat straw powder and geopolymer. By mass fraction, the wheat straw content is 0.5%-3%, the H2O2 content is 0.1%-2%, and the carbon content is... 12 H 25 The SO4Na content is 0.01%-0.06%, the red mud content is 20%-27%, the metakaolin content is 20%-27%, and the water glass content is 41%-46%. This invention also discloses a method for preparing the aforementioned biopolymer carbonized membrane, mainly including the following steps: uniformly mixing wheat straw powder with geopolymer raw materials, curing at a constant temperature, followed by demolding, surface polishing, and high-temperature calcination to finally obtain a wheat straw / geopolymer composite carbonized membrane. Furthermore, this invention clarifies the application of this membrane in the purification of wastewater containing Congo red dye and seawater desalination. The prepared biopolymer carbonized membrane possesses both highly efficient Congo red dye adsorption performance and good interfacial evaporation performance, enabling multi-purpose use and wide application in various water treatment scenarios.

Description

Technical Field

[0001] This invention belongs to the fields of membrane materials and green chemistry, and specifically relates to wheat straw / geopolymer composite carbonized membranes for the treatment of Congo red dye wastewater and seawater desalination, as well as their preparation methods and applications. Background Technology

[0002] Rapid industrialization has driven enormous demand for dyes in industries such as textiles, papermaking, food, pharmaceuticals, and cosmetics. However, this has also led to the massive discharge of dyeing wastewater, exacerbating water pollution and freshwater shortages. Congo red, a widely used anionic azo dye in the textile industry, is difficult to remove through natural degradation or conventional wastewater treatment due to its stable azo bonds (-N=N-) and aromatic ring structure. It is not only potentially carcinogenic but also considered a persistent organic pollutant, posing a serious threat to ecosystems and human health. Statistics show that the global dyeing industry generates over 120 million tons of Congo red-containing wastewater annually, of which 20% to 60% is directly discharged without effective treatment. On the other hand, improper disposal of industrial and agricultural waste also causes multiple environmental problems: the accumulation of solid waste and fly ash affects air quality and even exacerbates smog; agricultural waste, during accumulation, produces toxic gases and odors through microbial decomposition, and incineration releases carbon dioxide and dust, further polluting the environment. At the same time, population growth and industrialization have accelerated the greenhouse effect, leading to glacial melting, sea-level rise, changes in ocean circulation, and frequent extreme weather events. These factors have collectively exacerbated the global water crisis.

[0003] In the current context, traditional water resource development has reached its limits, making seawater desalination technology a crucial pathway to obtaining freshwater resources. However, most existing water treatment materials have limited functionality and struggle to simultaneously address the dual challenges of pollution control and freshwater acquisition. In recent years, membrane separation and interfacial evaporation technologies have gradually become research hotspots in the fields of water treatment and seawater desalination due to their ease of operation, recyclability, and avoidance of secondary pollution.

[0004] Therefore, developing a multifunctional membrane material capable of simultaneously treating dye pollution and achieving seawater desalination is of significant practical importance. This study uses industrial solid waste and agricultural waste as raw materials to achieve "waste-to-waste" through resource utilization. This not only helps alleviate the environmental pressure caused by waste accumulation but also effectively removes Congo red dye from water bodies and promotes the development of seawater desalination technology, providing an integrated solution for addressing water pollution and water scarcity. Summary of the Invention

[0005] Technical problem to be solved: The present invention aims to solve the above-mentioned problems by providing a biomass / geopolymer carbonization membrane, which solves the problems of water pollution caused by Congo red dye and the problem of obtaining freshwater resources through seawater desalination.

[0006] Technical Solution: A method for preparing a wheat straw / geopolymer composite carbonized membrane for water purification, characterized in that: wheat straw, red mud, and metakaolin are used as the main raw materials, and a wheat straw / geopolymer composite membrane is formed by an alkali-activated reaction, and then the final carbonized membrane is obtained by calcination under an inert atmosphere. The specific preparation steps include: (1) mixing wheat straw powder, metakaolin, red mud and water glass evenly, and then stirring at high speed using a disperser at room temperature; (2) adding 30wt% H2O2 and C to the above mixed slurry. 12 H 25 SO4Na, continue high-speed stirring until uniform, then pour into a mold and cure in a constant temperature oven; (3) demold the cured straw / geopolymer composite film, and adjust the thickness to a suitable level by surface polishing; (4) place the film in a crucible, put it into a tube furnace, and calcine it at the set temperature and time under inert gas protection. After calcination, the straw / geopolymer composite carbonized film is obtained, and its structural morphology is as follows. Figure 2 As shown.

[0007] Preferably, in step (1), the material needs to be passed through a 100-200 mesh sieve and 0.5%-3% wheat straw powder, 20%-27% metakaolin, 20%-27% red mud, and 41%-46% water glass with a modulus of 1.2-1.5M. The speed of the high-speed disperser is 800-1200 r / min, and the stirring time is 1-5 min.

[0008] Preferably, in step (2), 0.1%-2% of 30wt% H2O2 and 0.01%-0.06% C are added. 12 H 25 For SO4Na, the high-speed disperser speed is 800-1200 r / min, the stirring time is 1-5 min, the curing temperature is 60-80℃, and the curing time is 16-24 h.

[0009] Preferably, the thickness of the wheat straw / geopolymer composite film in step (3) is 2.0-5.0 mm.

[0010] Preferably, in step (4), the inert gas is N2, the heating rate of the tubular furnace is 1-5 min / ℃, the calcination temperature is 500-800℃, and the time is 10-80 min.

[0011] The wheat straw / geopolymer composite carbonized film prepared by the above method.

[0012] The aforementioned wheat straw / geopolymer composite carbonized film is characterized by being composed of wheat straw, metakaolin, red mud, and water glass to form the wheat straw / geopolymer composite carbonized film.

[0013] The wheat straw / geopolymer composite carbonized membrane of the present invention has excellent retention performance in water containing Congo red dye. In seawater desalination applications, the wheat straw / geopolymer composite carbonized membrane has excellent interfacial evaporation effect, providing a specific solution to water pollution and water shortage.

[0014] Beneficial effects: (1) High economic efficiency and low cost; (2) Using industrial solid waste and agricultural waste as the main raw materials, it effectively alleviates the environmental pollution problem caused by the accumulation of solid waste and agricultural waste; (3) The preparation cost of wheat straw / geopolymer composite carbonization membrane is low, the reaction conditions are mild, and the operation process is simple; (4) Wheat straw / geopolymer composite carbonization membrane is easy to recycle, recyclable and reusable, has good stability, and is not prone to secondary pollution; (5) The wheat straw / geopolymer composite carbonization membrane prepared by this invention has the dual functions of efficient adsorption and removal of Congo red dye and seawater desalination, and is suitable for water treatment needs in multiple fields. Attached Figure Description

[0015] Figure 1 The image shows the XRD pattern of the wheat straw / geopolymer composite carbonized film prepared in Example 1 of this invention.

[0016] Figure 2 Images of wheat straw / geopolymer composite carbonized film (a. Front view of the film; b. Surface view under an optical microscope; c, d. Electron microscope images of the film).

[0017] Figure 3 The graphs show the removal performance of different concentrations of Congo red by the geopolymer membrane of Comparative Example 1, the wheat straw biochar of Comparative Example 2, and the wheat straw / geopolymer composite carbonization membrane of Example 1.

[0018] Figure 4 Comparison of light and dark effects of adding membranes, including Comparative Example 1 (geopolymer membrane) and Example 2 (wheat straw / geopolymer composite carbonized membrane) on pure water and simulated seawater.

[0019] Figure 5 FT-IR image of wheat straw / geopolymer composite carbonized film

[0020] Figure 6 XPS image of wheat straw / geopolymer composite carbonized film Detailed Implementation

[0021] To better illustrate the present invention and facilitate understanding of its technical solutions, typical but non-limiting embodiments of the present invention are as follows:

[0022] Example 1

[0023] A method for preparing a wheat straw / geopolymer composite carbonized membrane for seawater desalination using solar radiation via interfacial evaporation technology, comprising the following steps: (1) mixing 2% wheat straw, 27% metakaolin, 27% red mud and 44% 1.3M water glass, and stirring the mixture at room temperature using a disperser at a speed of 1000 r / min for 2 min; (2) adding 0.9% of 30wt% H2O2 and 0.04% C 12 H 25 After SO4Na, continue high-speed stirring for 1 min. After stirring, pour the slurry into a mold and cure it in a constant temperature oven at 60℃ for 24 h. (3) Take out the cured wheat straw / geopolymer composite film, demold it, and polish it to make the film thickness 3.0 mm. (4) Place the film in a small crucible, put it into a tube furnace, introduce nitrogen gas, set the heating rate to 5℃ / min, the calcination temperature to 650℃, and the calcination time to 30 min. After calcination, let it cool naturally to obtain the wheat straw / geopolymer composite carbonized film.

[0024] Example 2

[0025] A method for preparing a wheat straw / geopolymer composite carbonized membrane (RWM / BC-CM) for retaining Congo red dye liquor, the specific steps are as follows: (1) Mix 2% wheat straw, 27% metakaolin, 27% red mud and 44% 1.3M water glass, and stir the mixture at room temperature using a disperser at a speed of 1000 r / min for 2 min; (2) Add 0.9% of 30 wt% H2O2 and 0.04% C 12 H 25 After SO4Na, continue high-speed stirring for 1 min. After stirring, pour the slurry into a mold and cure it in a constant temperature oven at 60℃ for 24 h. (3) Take out the cured wheat straw / geopolymer composite film, demold it, and polish it to make the film thickness 3.0 mm. (4) Place the film in a small crucible, put it into a tube furnace, introduce nitrogen gas, set the heating rate to 5℃ / min, the calcination temperature to 650℃, and the calcination time to 30 min. After calcination, let it cool naturally to obtain the wheat straw / geopolymer composite carbonized film.

[0026] Comparative Example 1

[0027] A method for preparing a geopolymer membrane (RWM) for retaining Congo red dye liquor, the specific steps of which are: (1) mixing 0% wheat straw, 27% metakaolin, 27% red mud and 44% 1.3M water glass, and stirring the mixture at room temperature using a disperser at a speed of 1000 r / min for 2 min; (2) adding 0.9% of 30 wt% H2O2 and 0.04% C 12 H 25After SO4Na, continue high-speed stirring for 1 minute. After stirring, pour the slurry into a mold and cure it in a constant temperature oven at 60℃ for 24 hours. (3) Take out the cured wheat straw / geolithic composite film, demold it, and polish it to make the film thickness 3.0mm.

[0028] Comparative Example 2

[0029] A method for preparing wheat straw biochar (BC) for retaining Congo red dye solution, the specific steps are as follows: (1) Place wheat straw in a small crucible, put it into a tube furnace and introduce N2. Set the heating rate to 5℃ / min, the calcination temperature to 650℃, and the calcination time to 30min. After calcination, cool to obtain wheat straw biochar.

[0030] Example 3

[0031] In this experiment, 5-25 mg / L Congo red dyeing solutions were selected as the treatment solutions. Specific steps: Congo red removal materials prepared according to the preparation methods described in Example 2, Comparative Example 1, and Comparative Example 2 (weighed according to the mass fraction of wheat straw in the carbonized film) were used. The materials prepared in Example 2, Comparative Example 1, and Comparative Example 2 were used to remove Congo red dyeing solutions of 5, 10, 15, 20, and 25 mg / L respectively at room temperature for 1 hour. After the experiment, the results were detected using a UV spectrophotometer and calculated using formulas (1-1, 1-2), as shown in the figure. Figure 3 .

[0032]

[0033] Depend on Figure 3 It can be seen that the removal performance of the wheat straw / geopolymer composite carbonized membrane in Example 2 is significantly different from that of the simple geopolymer membrane in Comparative Example 1 and the simple wheat straw carbon in Comparative Example 2 for Congo red dyeing. As shown in the figure, although the wheat straw / geopolymer composite carbonized membrane is composed of wheat straw and geopolymer, its removal performance is far superior to that of the two individual substances combined.

[0034] according to Figure 3The data shown demonstrates that the wheat straw / geopolymer composite carbonized membrane developed in this invention exhibits a significant removal effect on Congo red dye solutions. In contrast, the removal capacity of wheat straw biochar or pure geopolymer materials alone is relatively limited. Data from Comparative Example 1 (geopolymer membrane (RWM)) also shows that the removal rate is far below 20% within the 5-25 mg / L Congo red dye solution concentration range; Comparative Example 2 (wheat straw biochar) has a removal rate of approximately 50% within the 5-25 mg / L Congo red dye solution concentration range; while the wheat straw / geopolymer composite carbonized membrane in Example 1 has a removal rate of approximately 80% within the 5-25 mg / L Congo red dye solution concentration range. Notably, the removal performance of the composite membrane even exceeds the sum of the removal rates of the other two, fully demonstrating that the adsorption and removal capacity of the material for Congo red dye solution is synergistically enhanced through the composite preparation process, exhibiting superior potential for wastewater treatment.

[0035] Example 4

[0036] This experiment utilizes a xenon lamp with a 1.5G filter to simulate sunlight and achieve seawater desalination through interfacial evaporation technology. Specific steps: (1) In a dark environment without a membrane, 100g of deionized water and 100g of sodium chloride simulated seawater were subjected to dark evaporation for 5 hours. Mass loss was monitored in real-time using computer software, and the photoevaporation rate and solar energy conversion efficiency were calculated using formulas (2-1, 2-2); (2) In a xenon lamp simulating sunlight environment, 100g of deionized water and 100g of sodium chloride simulated seawater were subjected to photoevaporation for 5 hours without a membrane. Mass loss was monitored in real-time using computer software, and the photoevaporation rate and solar energy conversion efficiency were calculated using formulas (2-1, 2-2); (3) In a xenon lamp simulating sunlight environment, a comparative sample was added... 1. A geopolymer membrane (RMM) was used to photo-evaporate 100g of deionized water and 100g of sodium chloride simulated seawater for 5 hours. The mass loss was detected in real time using computer software, and the photo-evaporation rate and solar energy conversion efficiency were calculated using formulas (2-1, 2-2). (4) In a xenon lamp simulated sunlight environment, wheat straw / geopolymer composite carbonized membrane (RWM / BC-CM) from Example 2 was added, and 100g of deionized water and 100g of sodium chloride simulated seawater were photo-evaporated for 5 hours. The mass loss was detected in real time using computer software, and the photo-evaporation rate and solar energy conversion efficiency were calculated using formulas (2-1, 2-2). The above data were used to draw a graph. Figure 4 .

[0037] like Figure 4As shown, the wheat straw / geopolymer composite carbonized membrane prepared in Example 2 exhibits significantly improved interfacial evaporation performance compared to the pure geopolymer membrane in Comparative Example 1. Whether used in deionized water or simulated seawater systems, the solar evaporation efficiency of this composite membrane is significantly better than that of the pure geopolymer membrane, with particularly pronounced advantages in simulated seawater environments. Test data shows that the wheat straw / geopolymer composite carbonized membrane has a solar energy conversion efficiency as high as 128%. Its evaporation rates for deionized water and simulated seawater can reach 2.62 kg·m³, respectively. -2 .h -1 and 2.28 kg.m -2 .h -1 These figures represent 3.85 times and 3.4 times the evaporation rate under film-free conditions, respectively.

[0038] These results fully demonstrate that the composite membrane possesses excellent interfacial evaporation performance in the field of seawater desalination. The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a wheat straw / geopolymer composite carbonized membrane for water purification technology, characterized in that, Composed of wheat straw, red mud, and metakaolin, a wheat straw / geopolymer composite membrane is obtained through alkali activation; then, a wheat straw / geopolymer composite carbonized membrane is formed by inert gas calcination. The preparation steps are as follows: (1) Mix wheat straw, metakaolin, red mud, and water glass, and stir the mixture at high speed for 1-5 minutes at room temperature using a disperser; (2) Add H2O2 and C 12 H 25 SO4Na is added to the mixed slurry and stirred at high speed for 1-5 minutes. After stirring, the slurry is poured into a mold and cured in a constant temperature oven. (3) The cured wheat straw / geopolymer composite film is removed, demolded, and polished to make the film thickness appropriate. (4) The film is placed in a small crucible, placed in a tube furnace, and inert gas is introduced to set the calcination temperature and calcination time. After calcination, the wheat straw / geopolymer composite carbonized film can be obtained.

2. The method for preparing the biomass / geopolymer carbonized film according to claim 1, characterized in that, In step (1), wheat straw powder needs to be passed through a 100-200 mesh sieve and 0.5%-3% added, metakaolin added 20%-27%, red mud added 20%-27%, water glass modulus is 1.2-1.5M and 41%-46% added, and the speed of the high-speed disperser is 800-1200r / min.

3. The method for preparing the biomass / geopolymer carbonized film according to claim 2, characterized in that, In step (2), 0.1%-2% of 30wt% H2O2 and 0.01%-0.06% C are added. 12 H 25 For SO4Na, the high-speed disperser speed is 800-1200 r / min, the curing temperature is 60-80℃, and the curing time is 16-24h.

4. The method for preparing the biomass / geopolymer carbonized film according to claim 3, characterized in that, In step (4), the inert gas is N2, the calcination temperature of the tubular furnace is 500-800℃, and the time is 10-80min.

5. The method for preparing the biomass / geopolymer carbonized film according to claim 4, characterized in that, In step (3), the thickness of the wheat straw / geopolymer composite film is 2.0-5.0 mm.

6. The wheat straw / geopolymer composite carbonized film prepared by any of the preparation methods described in claims 1-4.

7. The wheat straw / geopolymer composite carbonized film according to claim 6, characterized in that, Composed of wheat straw, metakaolin, red mud and water glass, it forms a wheat straw / geopolymer composite carbonized film.

8. The application of the wheat straw / geopolymer composite carbonized membrane according to claim 7 in the removal of Congo red dye water pollution and seawater desalination.

9. The application of the wheat straw / geopolymer composite carbonization membrane according to claim 8 in seawater desalination, characterized in that, The simulated seawater concentration was 0-15.0 wt%, and the light intensity was 0-3.0 kW / m². 2 The wind speed is 0-5.0 m / s.

10. The application of the wheat straw / geopolymer composite carbonized membrane according to claim 9 in the removal of Congo red dyeing solution pollution, characterized in that, The concentration of Congo red staining solution was 5-30 mg / L, the retention time was 0.5-2.5 h, and the reaction temperature was room temperature.

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