A composite aerogel evaporator for accelerating urine evaporation concentration

Abstract

The present application relates to the technical field of solar interface evaporation porous polymer materials, and particularly relates to a composite aerogel evaporator for accelerating urine evaporation and concentration. The composite aerogel evaporator is a Janus double-layer structure, comprising a lower layer of cationic hydrophilic porous substrate and an upper layer of hydrophobic photothermal functional layer; the lower layer of cationic hydrophilic porous substrate is obtained by cross-linking, directional freeze forming and freeze drying of chitosan and cationic waterborne polyurethane; and the upper layer of hydrophobic photothermal functional layer is a polypyrrole layer, which is obtained by immersing the lower layer of cationic hydrophilic porous substrate in a mixed reaction solution of pyrrole and ammonium persulfate and then performing an oxidation polymerization reaction. The present application applies Hofmeister effect to a urine evaporation system for the first time, breaks the thermodynamic barrier that the evaporation rate of high-salt urine is lower than that of pure water, realizes simultaneous high recovery rate of nitrogen, phosphorus and potassium in urine and reclaimed water, improves operation efficiency, and is suitable for a photothermal evaporation treatment scene of source separation and urine resource utilization.

Description

Technical Field

[0001] This invention relates to the field of solar-powered interfacial evaporation porous polymer materials technology, and in particular to a composite aerogel evaporator for accelerating urine evaporation and concentration. Background Technology

[0002] Existing urine resource recovery technologies include air stripping, electrochemistry, membrane filtration, ion exchange, and cryogenic crystallization. These processes generally have high energy consumption, can only recover a single type of nutrient, and result in significant overall resource loss. They also cannot simultaneously recover water and nitrogen, phosphorus, and potassium nutrients.

[0003] According to Raoult's law, high salt content in urine will reduce the saturated vapor pressure and increase the enthalpy of evaporation. All conventional evaporation systems have inherent barriers: the evaporation rate of salt solutions is necessarily lower than that of pure water, and the evaporation efficiency continues to decrease as the concentration increases. This is the core limitation that existing evaporation materials cannot overcome.

[0004] The Hofmeister effect can regulate polymer hydration and reduce enthalpy of vaporization through anion regulation, but current research has only applied this mechanism to seawater desalination systems; to date, no studies have utilized endogenous Cl- in urine. - Combining cationic aerogels to trigger the Hofmeister effect solves the problem of thermodynamic inhibition of urine evaporation, but there is a lack of dedicated evaporation materials suitable for the complex multi-ion system of urine. Summary of the Invention

[0005] Based on the above, the present invention provides a composite aerogel evaporator for accelerating urine evaporation and concentration.

[0006] To achieve the above objectives, the present invention provides the following solution: One of the technical solutions of the present invention is a composite aerogel evaporator for accelerating urine evaporation and concentration, which has a Janus double-layer structure, including a lower cationic hydrophilic porous substrate and an upper hydrophobic photothermal functional layer. The lower cationic hydrophilic porous substrate is obtained by cross-linking chitosan and cationic waterborne polyurethane, directional freeze molding, and freeze drying. The upper hydrophobic photothermal functional layer is a polypyrrole layer, which is obtained by oxidative polymerization of the lower cationic hydrophilic porous substrate immersed in a mixed reaction solution of pyrrole and ammonium persulfate.

[0007] The second technical solution of the present invention is a method for preparing the above-mentioned composite aerogel evaporator, comprising the following steps: Chitosan solution was mixed with cationic aqueous polyurethane solution, stirred and ultrasonicated, and glutaraldehyde was added to carry out cross-linking reaction to obtain a uniform dispersion. The uniformly dispersed liquid was injected into a mold, directionally frozen and molded using liquid nitrogen, and then freeze-dried to obtain a lower cationic hydrophilic porous substrate. The lower cationic hydrophilic porous substrate is immersed in a mixed reaction solution of pyrrole and ammonium persulfate, and reacted at a constant temperature. After the reaction is completed, the substrate is washed until the washing solution is neutral to obtain the composite aerogel evaporator.

[0008] The third technical solution of the present invention is the application of the above-mentioned composite aerogel evaporator in urine evaporation and concentration.

[0009] The accelerated evaporation mechanism of the composite aerogel evaporator of this invention is as follows: After the cationic substrate is immersed in urine, Cl is selectively adsorbed and enriched by electrostatic interaction. - Reject Na + K + NH 4+ Ions; enriched Cl - Inserting into the gaps between polymer chains in the evaporator disrupts hydrogen bonds between molecular chains, reducing the overall crystallinity of the material and increasing the hydration of the molecular chains. The increased hydration of the polymer chains significantly increases the proportion of intermediate water (IW) in the system, reduces the total amount of hydrogen bonds between water molecules, and lowers the enthalpy of evaporation. Under acidified urine conditions (pH=4), the amino groups of chitosan are further protonated, increasing the positive charge strength of the substrate and further increasing Cl... - Adsorption capacity amplifies the evaporation acceleration effect; the top layer of polypyrrole (PPy) absorbs solar energy to increase the interface temperature, and the low-enthalpy intermediate water preferentially vaporizes; the hydrophobic surface layer hinders the adhesion of salt crystals, and the precipitated salt flows back and dissolves along the pores, ensuring no pore blockage during long-term operation.

[0010] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a composite aerogel evaporator that accelerates the evaporation of high-salt wastewater based on the Hofmeister ion effect. It has a Janus double-layer structure, consisting of a lower CS / WPU layer. + Composed of a cationic hydrophilic porous substrate and an upper PPy hydrophobic photothermal functional layer, the interface carries a stable positive potential and can electrostatically enrich endogenous Cl in urine. - This invention is the first to apply the Hofmeister effect to a urine evaporation system, breaking the thermodynamic barrier that the evaporation rate of high-salt urine is lower than that of pure water. While achieving high recovery rates of nitrogen, phosphorus, and potassium in urine and reclaimed water, it also improves operational efficiency and is suitable for photothermal evaporation treatment scenarios for source separation and urine resource utilization. Attached Figure Description

[0011] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0012] Figure 1 The zeta potential of the composite aerogel at different pH values; Figure 2 The evaporation rates of urine and pure water at different dilution levels over 8 hours; Figure 3 Evaporation rates of pretreated and untreated urine over 8 hours; Figure 4 The recovery rate of major nutrients in urine; Figure 5 The system's reclaimed water recovery rate; Figure 6 The figures represent the electrical conductivity of urine and reclaimed water before evaporation and concentration; the left figure shows the electrical conductivity of urine before evaporation and concentration, and the right figure shows the electrical conductivity of reclaimed water. Figure 7 Evaporation rates of pretreated and untreated urine over 7 days; Figure 8 The diagram shows the mechanical properties of the composite aerogel evaporator; where a is the actual pressure test diagram, b is the compressive stress value after five cycles, and c is the compressive stress curve after five cycles. Detailed Implementation

[0013] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0014] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0015] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0016] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0017] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0018] The first aspect of the present invention provides a composite aerogel evaporator for accelerating urine evaporation and concentration, which has a Janus double-layer structure, including a lower cationic hydrophilic porous substrate and an upper hydrophobic photothermal functional layer. The lower cationic hydrophilic porous substrate is obtained by cross-linking chitosan and cationic waterborne polyurethane, directional freeze molding, and freeze drying. The upper hydrophobic photothermal functional layer is a polypyrrole layer, which is obtained by oxidative polymerization of the lower cationic hydrophilic porous substrate immersed in a mixed reaction solution of pyrrole and ammonium persulfate.

[0019] In a preferred embodiment of the present invention, the zeta potential of the lower cationic hydrophilic porous substrate is 28.92 mV to 65.98 mV, which allows for the electrostatic enrichment of endogenous Cl in urine. - By relying on the Hofmeister effect to increase the proportion of intermediate water and reduce the enthalpy of evaporation, the evaporation of saline wastewater is accelerated.

[0020] The lower cationic hydrophilic porous substrate has a three-dimensional interconnected capillary network of 0.3-0 μm inside, and the vertical water transport height can reach 19 mm within 30 seconds.

[0021] In a preferred embodiment of the present invention, the water contact angle of the lower cationic hydrophilic porous substrate is 45-52°, the water contact angle of the upper hydrophobic photothermal functional layer is 91-105°, and the full-spectrum solar light absorption rate is greater than 95%.

[0022] The raw material system used in this invention is as follows: Hydrophilic substrate raw materials used to prepare the lower cationic hydrophilic porous substrate: chitosan (CS), cationic waterborne polyurethane (WPU) + Glutaraldehyde crosslinking agent; raw materials for preparing the upper hydrophobic photothermal functional layer: pyrrole monomer, ammonium persulfate oxidation initiator.

[0023] A second aspect of the present invention provides a method for preparing the above-mentioned composite aerogel evaporator, comprising the following steps: Chitosan solution was mixed with cationic aqueous polyurethane solution, stirred and ultrasonicated, and glutaraldehyde was added to carry out cross-linking reaction to obtain a uniform dispersion. The uniformly dispersed liquid was injected into a mold, directionally frozen and molded using liquid nitrogen, and then freeze-dried to obtain a lower cationic hydrophilic porous substrate. The lower cationic hydrophilic porous substrate is immersed in a mixed reaction solution of pyrrole and ammonium persulfate, and reacted at a constant temperature. After the reaction is completed, the substrate is washed until the washing solution is neutral to obtain the composite aerogel evaporator.

[0024] In a preferred embodiment of the present invention, the chitosan solution has a mass fraction of 1.5%-2%; the cationic aqueous polyurethane solution has a mass fraction of 30%; the volume ratio of the chitosan solution to the cationic aqueous polyurethane solution is 1:1; and the glutaraldehyde mass fraction in the uniform dispersion is 0.25-0.5%. In this invention, when the chitosan proportion is high, the overall mechanical strength of the aerogel will be greatly reduced, decreasing operational stability; when the chitosan proportion is low, the accelerated evaporation effect is poor. Therefore, the present invention limits the amount of chitosan used to the above parameters.

[0025] In a preferred embodiment of the present invention, the molar ratio of pyrrole to ammonium persulfate is 1:1.2-1:1.5, the isothermal reaction temperature is 4-10℃, and the isothermal reaction time is 6-8 h. In this invention, when the reaction temperature is high, the reaction will be more vigorous, resulting in uneven pyrrole loading; when the reaction temperature is low, the loading time will be prolonged, reducing the preparation efficiency. Therefore, the present invention limits the reaction temperature to 4-10℃.

[0026] A third aspect of the present invention provides the application of the above-described composite aerogel evaporator in urine evaporation and concentration.

[0027] In a preferred embodiment of the present invention, the urine is acidified urine with a pH of 4-5.

[0028] In a preferred embodiment of the present invention, the application includes: immersing the lower end of the composite aerogel evaporator into the surface of urine, exposing the upper hydrophobic photothermal functional layer to solar radiation, obtaining regenerated water after water vapor condensation, and retaining concentrated liquid fertilizer at the bottom of the container.

[0029] In a preferred embodiment of the present invention, the solar irradiance is 1-sun solar irradiance.

[0030] Unless otherwise specified, the technical solutions described in this invention are all conventional solutions in the field, and the reagents or raw materials used are all purchased from commercial channels or are publicly available unless otherwise specified.

[0031] The cationic aqueous polyurethane used in this embodiment of the invention is specifically a 30% cationic aqueous polyurethane solution from the McLean brand. The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0032] Example 1 Take 10 mL of 2% chitosan solution (the chitosan solution is prepared by dissolving acetic acid in pure water, and the mass concentration of acetic acid in the solvent is 1%) and mix it with 10 mL of cationic aqueous polyurethane (30% by mass) solution (the solvent is pure water) in a beaker, stir and sonicate for 3 min, then add 0.5% glutaraldehyde to complete the crosslinking and obtain a uniform dispersion. The above uniformly dispersed liquid was injected into a mold, directionally frozen using liquid nitrogen, and freeze-dried for 24 hours to obtain CS / WPU. + Cationic substrate aerogel (i.e., the lower cationic hydrophilic porous substrate); The above CS / WPU + The cationic substrate aerogel was immersed in a mixed reaction solution of pyrrole and ammonium persulfate in a molar ratio of 1:1.2 and reacted at a constant temperature of 4℃ for 6 h. After the reaction, it was repeatedly washed with deionized water until the washing solution was neutral, and finally the Janus bilayer cationic composite aerogel evaporator was obtained.

[0033] The fixed structural parameters of the Janus bilayer cationic composite aerogel evaporator (hereinafter referred to as: composite aerogel evaporator) prepared in this embodiment are as follows: The Zeta potential of the lower cationic hydrophilic porous substrate is 28.92-65.98 mV, with a stable positive charge (e.g., Figure 1 (as shown) The pore structure of the lower cationic hydrophilic porous substrate: three-dimensional interconnected capillaries with a pore size distribution of 0.3-10 μm; vertical water transport height of 19 mm in 30 s; Wetting properties: Bottom layer water contact angle 48.57° (hydrophilic), top layer PPy contact angle 91.45° (hydrophobic); Photothermal performance: Full-spectrum solar light absorption rate >95%; Mechanical properties: The structure withstands 3000g of pressure without damage; after 5 cycles of 40% compression, the stress shows no decrease (e.g., Figure 8 (as shown in a).

[0034] The performance of the composite aerogel prepared in this embodiment was tested, as follows: The lower end of the composite aerogel evaporator was immersed in the urine liquid surface, while the top PPy photothermal layer was exposed to 1-sun solar radiation. Urine was automatically transported upwards by capillary force, and evaporation was continuously accelerated at the photothermal interface. After water vapor condensation, neutral reclaimed water was obtained, while a high concentration of liquid organic fertilizer remained at the bottom of the container. The test results are as follows: 1. Accelerated Evaporation Core Performance (Test conditions: original urine pH 6.4, dilution ratios set to 4x and 10x, conducted at room temperature): The maximum evaporation rate of urine reached 3.68 kg·m³. -2 ·h -1 Compared to pure water (2.41 kg·m³), -2 ·h -1 The concentration increased by 52.7%; as the urine concentration and evaporation rate continued to rise, it broke the traditional law of the decline in evaporation rate of high-salt solutions (e.g., Figure 2 and Figure 3 (As shown).

[0035] 2. Nutrient and water resource recovery effect (test conditions: acidic urine pH 4, alkaline urine pH 10): Acidified urine system: nutrient recovery is nearly 90% (e.g.) Figure 4 As shown), the reclaimed water recovery rate is nearly 70% (e.g. Figure 5 As shown); the conductivity of the produced reclaimed water decreased to 631 μS / cm (as shown). Figure 6 (As shown).

[0036] 3. Long-lasting salt resistance and stability: Evaporation performance remains stable after seven days of continuous operation for 8 hours per day (e.g., Figure 7 (As shown).

[0037] 4. Mechanical durability properties: WPU + Cross-linking solves the brittleness defect of pure chitosan aerogel, ensuring it does not break under a 3000g heavy load, and its mechanical properties do not decrease after multiple compression cycles, making it suitable for long-term continuous concentration operation (e.g. Figure 8 (As shown).

[0038] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A composite aerogel evaporator for accelerating urine evaporation and concentration, characterized in that, It has a Janus bilayer structure, consisting of a lower cationic hydrophilic porous substrate and an upper hydrophobic photothermal functional layer; The lower cationic hydrophilic porous substrate is obtained by cross-linking chitosan and cationic waterborne polyurethane, directional freeze molding, and freeze drying. The upper hydrophobic photothermal functional layer is a polypyrrole layer, which is obtained by oxidative polymerization of the lower cationic hydrophilic porous substrate immersed in a mixed reaction solution of pyrrole and ammonium persulfate.

2. The composite aerogel evaporator according to claim 1, characterized in that, The zeta potential of the lower cationic hydrophilic porous substrate is 28.92 mV to 65.98 mV.

3. The composite aerogel evaporator according to claim 1, characterized in that, The lower cationic hydrophilic porous substrate has a water contact angle of 45-52°, the upper hydrophobic photothermal functional layer has a water contact angle of 91-105°, and the full-spectrum solar light absorption rate is greater than 95%.

4. A method for preparing the composite aerogel evaporator according to any one of claims 1 to 3, characterized in that, Includes the following steps: Chitosan solution was mixed with cationic aqueous polyurethane solution, stirred and ultrasonicated, and glutaraldehyde was added to carry out cross-linking reaction to obtain a uniform dispersion. The uniformly dispersed liquid was injected into a mold, directionally frozen and molded using liquid nitrogen, and then freeze-dried to obtain a lower cationic hydrophilic porous substrate. The lower cationic hydrophilic porous substrate is immersed in a mixed reaction solution of pyrrole and ammonium persulfate, and reacted at a constant temperature. After the reaction is completed, the substrate is washed until the washing solution is neutral to obtain the composite aerogel evaporator.

5. The preparation method according to claim 4, characterized in that, The chitosan solution has a mass fraction of 1.5%-2%; the cationic aqueous polyurethane solution has a mass fraction of 30%; the volume ratio of the chitosan solution to the cationic aqueous polyurethane solution is 1:1; and the glutaraldehyde mass fraction in the uniform dispersion is 0.25%-0.5%.

6. The preparation method according to claim 4, characterized in that, The molar ratio of pyrrole to ammonium persulfate is 1:1.2-1:1.5, the temperature of the isothermal reaction is 4-10℃, and the reaction time is 6-8h.

7. The application of the composite aerogel evaporator as described in any one of claims 1 to 3 in urine evaporation and concentration.

8. The application according to claim 7, characterized in that, The urine was acidified, with a pH of 4-5.

9. The application according to claim 7, characterized in that, The application includes: immersing the lower end of the composite aerogel evaporator into the surface of urine, exposing the upper hydrophobic photothermal functional layer to solar radiation, obtaining regenerated water after water vapor condensation, and retaining concentrated liquid fertilizer at the bottom of the container.

10. The application according to claim 9, characterized in that, The solar irradiance is 1-sun solar irradiance.

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