A design method for realizing active salt rejection of interface evaporator through conical pore structure

Abstract

This invention relates to a design method for active salt removal in an interfacial evaporator using a conical pore structure, belonging to the field of photothermal evaporation and nanofluid transport technology. Under conditions of limited porosity and evaporation rate, this method constructs a geometrically asymmetric conical nanopore structure. By controlling parameters such as pore size ratio, pore length, and pore wall surface potential, the ion transport path and mass transfer process within the pores can be directionally controlled. Combined with the coupling effects of multiple physical fields such as convection, diffusion, electromigration, and thermal diffusion, the migration of salt ions from the evaporation interface to the bulk solution is promoted, thereby forming a stable active salt removal effect. Compared to straight pore structures, the conical nanopores used in this invention can enhance the mass transfer asymmetry near the interface, improve ion migration efficiency, and thus significantly suppress salt accumulation in high-salt environments. This method can effectively improve the salt crystallization resistance and operational stability of photothermal evaporation systems.

Description

Technical Field

[0001] This invention relates to the field of interfacial energy conversion and nanofluid transport regulation technology, specifically to a design method for active salt removal from an interfacial evaporator through a conical pore structure. Background Technology

[0002] With the increasing global shortage of freshwater resources and growing energy pressure, photothermal interfacial evaporation technology, with its advantages of high photothermal conversion efficiency, low carbon footprint, environmental friendliness, and ability to utilize low-grade energy, has shown great application potential in fields such as seawater desalination and wastewater treatment. In recent years, research on evaporation-induced ion migration and interfacial mass transfer regulation has gradually attracted attention, providing new insights into improving salt control during the evaporation process. Furthermore, by regulating ion transport pathways and migration directions, the orderly migration and redistribution of salt ions can be achieved, potentially suppressing salt accumulation at the interface during evaporation, thus providing a new technical pathway for constructing highly stable photothermal evaporation systems.

[0003] Traditional photothermal evaporation systems typically consist of a photothermal absorption layer and a porous substrate. During continuous evaporation, water transport and solute enrichment processes within the substrate are coupled. However, due to the rapid evaporation rate at the interface, salt ions readily accumulate on the surface and within the pores of the porous structure, leading to severe salt buildup. Salt buildup not only reduces the light absorption capacity of the photothermal layer and the water evaporation flux but also significantly increases ion transport resistance due to pore blockage, thereby weakening the mass transfer efficiency of the system and making long-term stable operation difficult.

[0004] Currently, existing technologies for addressing salt accumulation primarily employ methods such as physical cleaning, structural optimization, or the introduction of passive diffusion channels. However, limited by the geometric symmetry of the pores and the limited physicochemical properties of the surface, these strategies often struggle to effectively control ion migration pathways while maintaining high evaporation flux, failing to fundamentally suppress the continuous accumulation of salt at the interface. Existing research largely focuses on improving the hydrophilicity of materials or optimizing pore structures, but studies on constructing geometrically asymmetric structures to regulate ion transport behavior and further achieve synergy between evaporation and active salt removal remain insufficient. In particular, the mechanism for utilizing the spatial structural asymmetry generated by conical nanopores, combined with the coupling effect of photothermal-driven convection, concentration, and temperature fields, to achieve directional ion migration and promote the return of salt to the bulk solution still lacks a systematic theoretical model and engineering implementation path.

[0005] Against this backdrop, the key issue in designing a long-life, high-stability photothermal interfacial evaporation system is how to precisely design ion transport paths and multi-field coupling strength by systematically controlling the geometric asymmetry, pore size ratio, and pore length of nanopores in porous substrates, thereby constructing a structural system that can guide salt ions from the interface to the bulk phase and suppress the accumulation of salt at the interface under continuous evaporation conditions.

[0006] Currently, research on the multiphysics coupling effects and control methods of asymmetric conical nanopore structures in evaporation-driven ion transport and active desalination processes is insufficient, lacking systematic design theories and engineering implementation pathways. Therefore, there is an urgent need for a photothermal interface evaporation system design method that, by controlling the geometric parameters of conical nanopores, achieves controllable ion transport paths and optimized mass transfer processes, thereby obtaining highly efficient active desalination capabilities under limited evaporation rates and porosity conditions. This method aims to meet the demands of next-generation water treatment systems for high performance and long-term stable operation. Summary of the Invention

[0007] To address the aforementioned problems, the main objective of this invention is to provide a design method for actively removing salt from an interface evaporator through a conical channel structure, which solves the problems of low adjustment accuracy, high operational risk, significant safety hazards, low efficiency, and inability to achieve quantitative and repeatable adjustment in the prior art.

[0008] To address the shortcomings of existing technologies, the present invention aims to provide a design method for active salt removal in an interfacial evaporator using a conical pore structure. This method designs a high-performance photothermal interfacial evaporation system comprising a photothermal absorbing material, a porous substrate material permeated with a conical nanopore array, and an electrical signal extraction unit. By controlling one or more of the pore size ratio, pore length, and surface potential of the conical nanopores, the system constructs a multi-physics coupled transport path based on the ion concentration polarization effect, achieving active control of high ion flux output and dynamic salt balance under limited evaporation rate and porosity conditions. Based on this, the salt removal rate of the system of the present invention is at 10... -11 mol·m -2 ·s -1 The order of magnitude, and can be from 0 to -6 × 10⁻⁶. -10 mol·m -2 ·s -1 It can achieve continuous adjustment within a certain range, thereby realizing a controllable transition from a weak salt discharge state to a strong salt discharge state, meeting the requirements for efficient ion separation and stable operation under different concentration gradients and complex salt environments.

[0009] The present invention solves the above-mentioned technical problems through the following technical solution: a design method for active salt removal of an interface evaporator through a conical channel structure. The method is based on a photothermal interface evaporation system constructed by a conical nanopore array with a geometrically asymmetric structure. The conical nanopores penetrate a porous substrate material, and the two ends of the pores are a large pore end and a small pore end, respectively. The pores have a preset porosity. The method includes the following steps: Step 1: Construct a single cone-shaped nanopore model Based on numerical simulation methods, we established single conical nanopore structure models with different pore size ratios and pore lengths, and controlled the degree of geometric asymmetry of the pores to form structural systems with different ion transport properties. Step 2: Constructing a photothermal evaporation-ion transport coupling system Under photothermal evaporation conditions, a multiphysics model coupling diffusion, electromigration, convection, and thermal diffusion is constructed by introducing concentration gradient, surface potential gradient, temperature gradient, and fluid convection field. Under the condition of limited porosity and evaporation rate, the influence of different pore size ratios and pore length structural parameters on the overall ion transport characteristics is calculated. By controlling the pore size ratio, pore length, and pore wall surface potential, the directional migration and mass transfer regulation of ions in conical nanopores is realized.

[0010] The salt removal phenomenon is as follows: under the coupling effect of multiple physical fields, salt ions are promoted to migrate from the evaporation interface to the bulk solution, thereby inhibiting the accumulation of salt in the pores and achieving continuous removal; when the system can stably maintain the above-mentioned ion migration and mass transfer process within the limited evaporation rate and porosity range, and effectively inhibit salt accumulation, active salt removal based on the photothermal interface regulated by the conical nanopore structure is realized.

[0011] In a specific embodiment of the present invention, in step one, the radius r of the tapered nanopore is... s The pore size is 50–70 nanometers, and the macropore radius is r. l The design range is 100–200 nm, the pore size ratio λ is 2–4, and the channel length L is 5000–9000 nm.

[0012] In a specific embodiment of the present invention, in step one, the porosity ε of the porous substrate material is designed to be 10-90%, and the overall porosity is controllably adjusted by adjusting the pore diameter and pore spacing.

[0013] In a specific embodiment of the present invention, in step one, the inner wall of the conical nanopore has a surface charge, and the surface potential ψ of the pore wall is designed to be 25, 50, 75, and 100 millivolts, respectively.

[0014] In a specific embodiment of the present invention, in step one, the porous substrate material is selected from one or more of the following: alumina (Al2O3), silicon dioxide (SiO2), titanium dioxide (TiO2), boron nitride (BN), silicon carbide (SiC), polymer porous membranes, or composite materials thereof.

[0015] In a specific embodiment of the present invention, in step two, the concentration difference ΔC between the two ends of the conical nanopore channel due to salt enrichment induced by water evaporation and the external environment is designed to be in the range of 10 to 100 mol per cubic meter, wherein the concentration of the liquid at the bottom end is set to be 0.5 to 5 mol per cubic meter.

[0016] In a specific embodiment of the present invention, in step two, the temperature difference ΔT between the two ends of the porous substrate due to local photothermal heating is designed to be 0.5 to 10 Kelvin.

[0017] In a specific implementation of the present invention, in step two, the evaporation rate J, based on the principle of conservation of mass and volumetric flow rate, is designed to be 1 to 5 kg per square meter per hour.

[0018] The positive and progressive effects of this invention are as follows: The design method for active salt removal in an interfacial evaporator using a conical pore structure provided by this invention has the following advantages: By adjusting the structural parameters of the conical nanopores and the surface potential of the pore walls, this invention achieves the orderly construction of ion transport paths and active salt removal functions within the photothermal interfacial evaporation system. This invention, by adjusting one or more parameters among the pore size ratio, pore length, and surface potential of the conical nanopores, can effectively optimize ion transport paths, enabling a photothermal interfacial evaporation system that achieves salt removal and dynamic equilibrium under limited evaporation rate and porosity conditions. Numerical simulation analysis of the influence of different pore structures and pore wall surface potentials on the overall ion flux allows for the control of the system's salt removal efficiency and mass transfer performance.

[0019] The photothermal interface evaporation system proposed in this invention consists of a photothermal absorption layer, an asymmetric conical nanoporous substrate, and an electrode extraction unit. It has excellent energy conversion performance and good long-term operational stability, and can be adapted to various complex water quality application scenarios such as seawater desalination, high-salt wastewater treatment, and environmental energy capture.

[0020] This invention optimizes the channel geometry and the surface potential of the pore wall to achieve efficient active salt removal and self-cleaning effects at a lower cleaning frequency and with less external intervention than traditional designs, significantly reducing maintenance costs and system complexity. This provides a new technical solution for the application of high-performance self-circulating water treatment devices. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the principle of the photothermal interface evaporation system based on conical nanopores of the present invention.

[0022] Figure 2 This is a schematic diagram of the three-dimensional macroscopic structure of an arrayed conical nanochannel membrane with transport characteristics according to the present invention.

[0023] Figure 3 This is a graph showing the relationship between the total ion flux and the concentration difference in a single straight channel and a conical channel under different pore wall surface potentials, pore diameter ratios, and pore lengths in the photothermal interface evaporation system designed based on the method of the present invention in Example 1. Detailed Implementation

[0024] The preferred embodiments of the present invention are given below with reference to the accompanying drawings to illustrate the technical solution of the present invention in detail.

[0025] To address the shortcomings of existing technologies, this invention provides a design method for active salt removal in an interfacial evaporator using a conical pore structure. The high-performance photothermal interfacial evaporation system designed by this method comprises a photothermal absorbing material, a porous substrate material with a perforated array of conical nanopores, and an electrical signal extraction unit. By controlling one or more of the pore size ratio, pore length, and surface potential of the pore walls of the conical nanopores, the system constructs a multi-physics coupled transport path based on the ion concentration polarization effect, achieving active control of high ion flux output and dynamic salt balance under limited evaporation rate and porosity conditions. Based on this, the salt removal rate of the system of this invention is at 10... -11 mol·m -2 ·s -1 The order of magnitude, and can be from 0 to -6 × 10⁻⁶. -10 mol·m -2 ·s -1 It can achieve continuous adjustment within a certain range, thereby realizing a controllable transition from a weak salt discharge state to a strong salt discharge state, meeting the requirements for efficient ion separation and stable operation under different concentration gradients and complex salt environments.

[0026] In this invention, a conical nanopore refers to a microscopic transport channel unit that penetrates a porous substrate material and possesses geometric asymmetry in a photothermal interfacial evaporation system. The channel is characterized by its geometric parameters, specifically defined as: a microscopic transport channel with a large opening radius r... l Small end radius r sThe asymmetric space formed by the pore length L is defined as the pore size ratio λ, where the diameter ratio of the large end to the small end is defined as the pore size ratio. The pores must satisfy geometric continuity, meaning the pore size changes linearly and continuously from the large end to the small end, and each pore is independent and does not intersect with others within the substrate. The pores are filled with an electrolyte solution, and the pore walls have a specific charge density and surface potential ψ. The spatial distribution of the pores satisfies a specific porosity ε, exhibiting a periodic array distribution. The transport mode refers to the migration orientation of ions and fluid within the conical nanopores under the influence of evaporation driving force, concentration gradient, and electric field coupling. The transport mode must satisfy flow conservation, meaning that under steady-state evaporation flux J, the flow velocity, porosity, and cross-sectional area within the pores satisfy a volumetric flow rate balance relationship. The critical concentration difference ΔCc is the solute concentration threshold that causes a directional change in the total ion flux Φ of the system under a specific geometric structure and evaporation rate. The critical concentration difference is determined based on the directional characteristics of the total ion flux, specifically defined as follows: when the total ion flux Φ > 0, the system is in a diffusion-dominated migration state; when the total ion flux Φ < 0, the system enters an active salt expulsion mode; when the total ion flux Φ is exactly zero, the concentration difference across the pore is the critical concentration difference. The critical concentration difference must satisfy dynamic equilibrium, meaning that under this state, the various ion fluxes generated by diffusion, convection, thermal diffusion, and electromigration completely cancel each other out in the vector direction. The value of this critical point is systematically controlled by the pore length L, the pore size ratio λ, and the surface potential ψ of the pore wall.

[0027] like Figure 1 , Figure 2 As shown, this invention proposes an active salt removal design method for a conical nanopore photothermal interface based on controlling the aperture ratio, pore length, and pore wall surface potential, comprising the following steps: Step 1: Construct a single cone-shaped nanopore model, and adjust the geometric asymmetry parameters and surface charge distribution of the cone-shaped nanopore to form a microstructure model with specific ion transport characteristics; Step 2: Construct a photothermal evaporation-ion transport coupling system. Apply the constructed nanopore model to the simulated photothermal evaporation field. Design the ion transport path by adjusting the physical field gradient and pore structure parameters. Numerically simulate and calculate the salt migration and active salt removal effect of the entire system, thereby completing the optimized design of the photothermal interface active salt removal system.

[0028] Furthermore, in step one, the porous substrate material can be designed as alumina (Al2O3), silicon dioxide (SiO2), titanium dioxide (TiO2), boron nitride (BN), silicon carbide (SiC), polymer porous membranes, or composite materials thereof, which have stable chemical properties and porous structures.

[0029] Furthermore, in step one, the pore radius r of the tapered nanopores s Designed to be 50–70 nanometers, with a large pore radius r lThe design range is 100–200 nanometers, and the nanopore size ratio λ is designed to be 2–4.

[0030] Furthermore, in step one, the length L of the tapered nanopore is designed to be in the range of 5000–9000 nanometers.

[0031] Furthermore, in step one, the inner wall of the conical nanopore has a surface charge, and the surface potential ψ of the pore wall is designed to be 25, 50, 75, and 100 millivolts, respectively.

[0032] Furthermore, in step two, the temperature difference ΔT between the two ends of the porous substrate due to local photothermal heating is designed to be 1 Kelvin.

[0033] Furthermore, in step two, the concentration difference ΔC between the two ends of the conical nanopore channel, induced by water evaporation and formed by the external environment, is designed to be in the range of 10 to 50 moles per cubic meter, with the concentration of the liquid at the bottom set to 1 mole per cubic meter.

[0034] Furthermore, in step two, the porosity ε of the porous substrate material is designed to be 10-90%, and the overall fluid flux is quantitatively controlled by adjusting the pore density within a standard area of ​​1 square meter.

[0035] Furthermore, in step two, based on the principle of conservation of mass and volumetric flow rate, the interfacial evaporation rate J under a standard area of ​​1 square meter is converted into the average flow velocity v in a single channel.

[0036] Furthermore, in step two, the finite element method is used to establish a set of multiphysics field control equations by coupling the Poisson equation, the Nernst-Planck equation and the Navier-Stokes equation, and to solve them iteratively. The total ion flux and the flux of each component in the system are calculated, and the critical concentration difference ΔCc is found to verify the effect of active salt removal and the optimization of ion transport under the conical nanopores.

[0037] Furthermore, by selecting a micro / nano fabrication, trajectory etching, or self-assembly pore construction process, a periodic array of conical nanopores with specific geometric parameters is formed inside a porous substrate material to prepare a photothermal interface evaporation active salt removal device with controllable structure and excellent performance, achieving stable salt removal and pore salt accumulation inhibition.

[0038] Example 1 The photothermal interface evaporation power generation and active salt removal system designed in this invention uses silicon carbide (SiC) as a porous substrate to construct conical nanopores with geometrically asymmetric characteristics. The pore size is controlled to create highly efficient ion transport channels. For example... Figure 3As shown, this invention utilizes numerical simulation methods in multiphysics numerical simulation software to calculate and analyze the system. First, the model is standardized, with the simulated porous substrate area set to 1 square meter and the temperature difference ΔT set to 1 Kelvin. Through boundary condition processing, the evaporation rate J (set to 2 kg / m² / hour) under a standard area of ​​1 square meter is transformed into the average flow velocity v within a single pore based on the principle of mass conservation. Based on this, as... Figure 3 As shown in part a, the length of both the straight and tapered channels is set to L = 8000 nanometers, and the radii of the two ends of the straight channel are both r. l =200 nanometers; radius r of the tapered channel pore s =50 nanometers, macropore radius r l =200 nm. As the surface potential ψ of the pore wall increases from 25 mV to 100 mV, the charge selectivity within the system gradually increases. For straight channels, the internal electric field is uniformly distributed, and the total ion flux shows a linear trend with the increase of the concentration difference ΔC, with a relatively gentle overall change. In contrast, due to the asymmetry of the geometric structure, the ion transport behavior inside the conical channels exhibits significant differences in different directions. When the surface potential ψ is 25 mV, the geometric asymmetry of the conical channel has a weak promoting effect on ion migration. The confinement effect at the small pore tip and the initial concentration polarization inhibit ion migration to some extent, thus making its ion flux amplitude lower than that of straight channels under the same size conditions. When the surface potential ψ is 50 mV, the critical salt expulsion concentration difference ΔCc is 39 mol / m³. At this point, the diffusion driving force and the electromigration driving force in the system reach a relative equilibrium, and the total ion flux is close to zero. When the surface potential ψ increases to 75 and 100 mV, the geometrically asymmetric structure of the conical channel can reduce the effective transport resistance of ions through the channel, making its flux amplitude higher than that of a straight channel under the same size conditions. At the same time, the electrostatic shielding effect of the small end region is enhanced, forming an ion depletion region near the channel entrance, thereby suppressing the concentration gradient-driven diffusion flux and making the electric field-driven migration flux dominant, so that the direction of ion migration can be controlled even under low concentration gradient conditions.

[0039] like Figure 3 As shown in section b, this invention further modulates the influence of pore size ratio λ and concentration difference ΔC on ion flux. Specifically, the pore length L is set to 8000 nm, and the pore radius r... s =50 nanometers, macropore radius r lThe design range is 100–200 nm, i.e., the nanopore size ratio λ is 2–4. The surface potential of the pore wall is ψ = 50 mV, thus forming conical nanopore structures with different pore size ratios λ. Under ion migration, larger pore size ratios λ = 3.5 and 4 are more likely to produce negative ion flux under lower concentration gradients, thereby enhancing the system's active salt removal capacity. This is because as the pore size ratio increases, the geometric asymmetry of the pores increases, the electric field concentration effect at the small pore tip region becomes more pronounced, and an ion depletion region is easily formed at the pore inlet, thus promoting the reversal of the ion migration direction. When the pore size ratios λ = 3.5 and λ = 4, the corresponding critical concentration gradients ΔCc are approximately 41 mol / m³ and 43 mol / m³, respectively. The difference between the two is small, indicating that the diffusion driving force and the electromigration driving force reach a relative balance in this range, and the net ion flux in the pores is close to zero. When the concentration difference exceeds the critical value, the ion flux increases monotonically with increasing ΔC, but the flux amplitude still varies under different pore size ratios. Increasing the pore size ratio is beneficial for enhancing the electric field gradient within the pores, but an excessively large pore size ratio may introduce transport inhomogeneities, thereby affecting the ion migration process. Therefore, there exists a reasonable pore size ratio range within the parameter range to achieve a balance between the physical field enhancement effect and the ion transport resistance, thereby improving the overall ion desalination performance of the system.

[0040] like Figure 3 As shown in section c, the effect of further modulating the pore length L on ion transport behavior under transport mode is demonstrated. In the calculations, the pore length L was set to 5000, 6000, 7000, 8000, and 9000 nm, and the pore radius r was... s =50 nanometers, macropore radius r l The pore length is 200 nm, and the surface potential of the pore wall is ψ = 50 mV. With increasing pore length L, the critical concentration difference ΔCc for triggering salt expulsion under different length conditions shows relatively small differences, all around 45 mol / m³. In contrast, when the pore length L = 8000 nm, the critical concentration difference for triggering salt expulsion decreases slightly, and active salt expulsion flux can be induced at ΔC = 43 mol / m³, exhibiting a certain degree of early triggering characteristic. However, with increasing pore length, the ion flux in the system generally shows a decreasing trend. This indicates that longer nanopores increase the migration path of ions within the pore, thereby increasing transport resistance and inhibiting ion migration. Comprehensive experimental analysis shows that the optimal active salt expulsion configuration is achieved with a pore wall surface potential ψ = 100 mV, a pore size ratio λ = 3.5, and a pore length L = 8000 nm under a conical pore.

[0041] Within the above parameter adjustment range, the total ion flux of the system of the present invention is at 10. -11 mol·m -2 ·s -1Order of magnitude. When the surface potential of the pore wall, the pore size ratio, and the pore length are optimized in a coordinated manner, the maximum negative ion flux can reach approximately -6 × 10⁻⁶. -10 mol·m -2 ·s -1 Under low-driving conditions, the total ion flux approaches zero. Therefore, this invention achieves a salt removal rate of 0 to -6 × 10⁻⁶. -10 mol·m -2 ·s -1 It is continuously adjustable within a certain range, with a maximum adjustment range of approximately 6 × 10. -10 mol·m -2 ·s -1 By controlling the surface potential of the pore wall, the pore size ratio, and the pore length, the direction and intensity of ion transport can be controlled and adjusted, thereby achieving stable switching between weak and strong salt removal states and meeting the requirements for efficient ion separation under different concentration gradient conditions.

[0042] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as defined by the appended claims and their equivalents.

Claims

1. A design method for achieving active salt removal in an interfacial evaporator through a conical channel structure, characterized in that: The method is based on a cone-shaped nanopore array with a geometrically asymmetric structure to construct a photothermal interface evaporation system. The cone-shaped nanopores penetrate the porous substrate material, and the two ends of the pores are a macropore end and a micropore end, respectively. The pores have a preset porosity. The method includes the following steps: Step 1: Construct a single cone-shaped nanopore model Based on numerical simulation methods, we established single conical nanopore structure models with different pore size ratios and pore lengths, and controlled the degree of geometric asymmetry of the pores to form structural systems with different ion transport properties. Step 2: Constructing a photothermal evaporation-ion transport coupling system Under photothermal evaporation conditions, a multiphysics model coupling diffusion, electromigration, convection, and thermal diffusion is constructed by introducing concentration gradient, surface potential gradient, temperature gradient, and fluid convection field. Under the constraints of porosity and evaporation rate, the influence of different pore size ratios and pore length structural parameters on the overall ion transport characteristics is calculated. By controlling the pore size ratio, pore length, and pore wall surface potential, the directional migration and mass transfer regulation of ions in conical nanopores is achieved. The salt removal phenomenon is as follows: under the coupling effect of multiple physical fields, salt ions are promoted to migrate from the evaporation interface to the bulk solution, thereby inhibiting the accumulation of salt in the pores and achieving continuous removal; when the system can stably maintain the above-mentioned ion migration and mass transfer process within the limited evaporation rate and porosity range, and effectively inhibit salt accumulation, active salt removal based on the photothermal interface regulated by the conical nanopore structure is realized.

2. The design method for active salt removal from an interfacial evaporator using a conical channel structure as described in claim 1, characterized in that: In step one, the radius r of the tapered nanopore is... s The pore size is 50–70 nanometers, and the macropore radius is r. l The design range is 100–200 nm, the pore size ratio λ is 2–4, and the channel length L is 5000–9000 nm.

3. The design method for active salt removal from an interfacial evaporator using a conical channel structure as described in claim 1, characterized in that: In step one, the porosity ε of the porous substrate material is designed to be 10-90%, and the overall porosity can be controlled by adjusting the pore diameter and pore spacing.

4. The design method for active salt removal from an interfacial evaporator using a conical channel structure as described in claim 1, characterized in that: In step one, the inner wall of the conical nanopore has a surface charge, and the surface potential ψ of the pore wall is designed to be 25, 50, 75, and 100 millivolts, respectively.

5. The design method for active salt removal from an interfacial evaporator using a conical channel structure according to claim 1, characterized in that: In step one, the porous substrate material is selected from one or more of the following: alumina (Al2O3), silicon dioxide (SiO2), titanium dioxide (TiO2), boron nitride (BN), silicon carbide (SiC), polymer porous membranes, or composite materials thereof.

6. The design method for active salt removal from an interface evaporator using a conical channel structure according to claim 1, characterized in that: In step two, the concentration difference ΔC between the two ends of the conical nanopore, induced by water evaporation and formed by the external environment, is designed to be in the range of 10 to 100 mol per cubic meter, with the concentration of the liquid at the bottom set to be 0.5 to 5 mol per cubic meter.

7. The design method for active salt removal from an interfacial evaporator using a conical channel structure according to claim 1, characterized in that: In step two, the temperature difference ΔT between the two ends of the porous substrate due to local photothermal heating is designed to be 0.5 to 10 Kelvin.

8. The design method for active salt removal from an interfacial evaporator using a conical channel structure according to claim 1, characterized in that: In step two, the evaporation rate J is designed to be 1 to 5 kg per square meter per hour based on the principle of conservation of mass and volumetric flow rate.

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