Multi-thorn needle point type saline-alkali soil treatment evaporator and preparation method thereof

Abstract

The invention discloses a multi-thorn needle tip type saline-alkali soil treatment evaporator and a preparation method thereof, the multi-thorn needle tip type saline-alkali soil treatment evaporator is prepared by taking light wood pulp as a substrate, composite chitosan, carbon nanotubes and other raw materials through condensation reaction and freeze forming, a main body is a blocky substrate, a conical needle tip structure is integrally distributed on the surface, the taper angle of a needle tip is 12-35 degrees, and the length of the needle tip is 0.8-2.2 cm. Through the multi-thorn needle point type structural design, salt crystals are separated out only at the needle point and fall off automatically by means of gravity, the problem that the salt crystals are accumulated on a photo-thermal interface body is solved, the continuous working time of solar driving interface evaporation is prolonged to 15 h or above from 5 h of a traditional evaporator, the evaporation rate reaches 1.2 kg / mh to 1.5 kg / mh under one sunlight intensity, and the energy consumption is reduced. The salt removal rate of the saline-alkali soil exceeds 60%, meanwhile, passive recovery of mineral salt can be achieved, and an efficient solution is provided for large-scale treatment of the saline-alkali soil.

Description

Technical Field

[0001] This application relates to the field of evaporator preparation technology, and in particular to a multi-prickly needle-tip type evaporator for saline-alkali land treatment and its preparation method. Background Technology

[0002] my country has vast areas of saline-alkali land, mainly distributed in the northwest inland and coastal areas. Salinization severely restricts agricultural production and damages the ecological environment. Traditional treatment methods, such as water conservancy improvement and chemical improvement, suffer from high costs, long cycles, and low resource utilization rates. Solar-driven interfacial evaporation technology, with its advantages of being green, environmentally friendly, and low-cost, has become an emerging technological direction for saline-alkali land treatment. It converts solar energy into heat energy through photothermal materials, accelerating the evaporation of saline-alkali land solutions and achieving desalination and freshwater recovery.

[0003] However, existing solar evaporators face a core technological bottleneck in their application to saline-alkali land remediation: salt crystals easily accumulate on the main surface of the photothermal interface, blocking water transport channels and obstructing sunlight, thus interrupting the photothermal reaction and preventing continuous evaporation. Existing technologies, such as 3D porous evaporators and carbon-based composite evaporators, while improving evaporation efficiency, have not solved the problem of salt crystal accumulation. Some improvement schemes attempt to reduce salt adsorption through surface modification, but the effects are limited; salt crystals still gradually cover the photothermal layer, restricting the practical application of evaporators in saline-alkali land remediation. Furthermore, the fabrication of existing evaporators largely relies on complex template synthesis or high-temperature sintering processes, making large-scale production difficult and further hindering their industrialization and promotion.

[0004] To address the aforementioned issues, this application presents an evaporator with a multi-needle tip structure. By utilizing the principle of localized salt crystallization, salt is precipitated only at the tip and then detaches on its own. Simultaneously, a simple acid-base treatment and freeze-forming process are employed to achieve low-cost, large-scale production of the evaporator, effectively solving the technical pain points of traditional evaporators. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing solar evaporators in saline-alkali land remediation, such as salt crystal accumulation and inability to operate continuously. This invention provides a multi-prickly needle-shaped evaporator for saline-alkali land remediation and its preparation method. Through structural innovation and process optimization, it enables continuous solar-driven interface evaporation while improving the desalination efficiency and resource recovery capacity of saline-alkali land.

[0006] This application discloses a multi-spined needle-tip type evaporator for saline-alkali land treatment, characterized in that it is made of balsa wood-based hydrogel by freezing and molding, and includes an integrated block matrix and multiple conical needle-tip structures; the conical needle-tip structures are evenly distributed on the upper surface of the block matrix, with a cone angle of 12°~35°, a length of 0.8cm~2.2cm, and a distance of 1.5cm~3.5cm between adjacent needle tips.

[0007] Preferably, the balsamic-based hydrogel is composed of 45 to 55 parts of balsamic pulp, 0.8 to 1.2 parts of chitosan, 0.8 to 1.2 parts of glacial acetic acid, 0.8 to 1.2 parts of hydrochloric acid, 0.08 to 0.12 parts of piperazine, 0.08 to 0.12 parts of carbon nanotubes, and 0.5 mL to 0.7 mL of glutaraldehyde.

[0008] Preferably, the balsa wood pulp is a cellulose suspension obtained by filtration after balsa wood has been treated with acetic acid and sodium hydroxide, and its weight fraction is 8%~12%.

[0009] This application also provides a method for preparing the above-mentioned evaporator, including the following steps:

[0010] Preparation of S1 balsa wood pulp: Balsa wood is cut into small pieces, placed in pure water, and acetic acid is added under 100°C oil bath conditions. The mixture is stirred at 180~220 rpm for 10~14 hours for acid treatment. After the acid treatment solution is poured off, pure water is added again, and sodium hydroxide is added under 100°C oil bath conditions. The mixture is stirred at the same speed for 10~14 hours for alkali treatment. After cooling to room temperature, the suspension is filtered 3~5 times. The solid residue is taken and deionized water is added to prepare balsa wood pulp with a weight fraction of 8%~12%.

[0011] Preparation of S2 hydrogel precursor solution: Take the balsa wood pulp obtained in step S1, add chitosan, glacial acetic acid and hydrochloric acid, and stir at 180~220 rpm for 8~12 min; then add piperazine and carbon nanotubes, and continue to stir at the same speed for 8~12 min; finally add glutaraldehyde, and stir for 2~5 min to initiate aldol condensation reaction to obtain hydrogel precursor solution.

[0012] S3 Cryogenic Molding: The hydrogel precursor liquid obtained in step S2 is injected into a multi-needle tip mold and frozen at -6~-2℃ for 20~28h; after freezing, the mold is removed and the mixture is thawed naturally to obtain a multi-needle tip saline-alkali land treatment evaporator.

[0013] Preferably, in step S1, the oil bath temperature fluctuation range for acid treatment and alkali treatment does not exceed ±2℃, vacuum filtration is used, and the filter membrane pore size is 0.22μm.

[0014] The advantages of this invention are:

[0015] 1. This invention utilizes a multi-needle-tip structure design and the principle of local salt crystallization to ensure that salt is precipitated only at the needle tip. The salt crystals at the needle tip fall off by gravity, avoiding the accumulation of salt crystals on the main body of the photothermal interface. This extends the continuous working time of the evaporator from the traditional 5 hours to more than 15 hours. Under one solar intensity, the evaporation rate reaches 1.2~1.5 kg / (m²•h), and the desalination rate of saline-alkali land exceeds 60%.

[0016] 2. The preparation process of this invention is simple, using acid-alkali treatment and freeze molding, without the need for complex equipment. The raw material, balsa wood, is widely available and inexpensive. The solvent has a recyclability rate of >90%, making it suitable for large-scale production. The size of the evaporator and the needle tip structure parameters can be flexibly adjusted through the mold to meet the treatment needs of different types of saline-alkali land.

[0017] 3. The porous structure formed by acid and alkali treatment of balsa wood can construct efficient capillary channels, thereby rapidly transporting saline-alkali land aqueous solutions to the photothermal interface. The hydrophilic groups of chitosan can enhance the water retention capacity of the matrix, and the uniformly dispersed carbon nanotubes can absorb solar energy and convert it into heat energy. The synergistic effect of these three elements achieves efficient coupling of photothermal conversion and water transport. At the same time, the needle-like structure enables the passive recovery of mineral salts. The recovered salt crystals have a purity >95%, which can be used as industrial raw materials, achieving a win-win situation for both the economic and ecological benefits of saline-alkali land management. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 The diagram shown is a schematic of the evaporator of the present invention;

[0020] Figure 2 The figure shown is a continuous working performance test curve of an embodiment of the present invention;

[0021] Figure 3 The figure shown is a test curve of desalination rate and salt crystal recovery amount in Example 1 of the present invention;

[0022] Figure 4 The image shown is a real photograph of the long-term photothermal reaction in Embodiment 1 of the present invention. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Example 1

[0025] Preparation of S1 balsa wood pulp: Balsa wood was cut into small pieces of 1cm×1cm×0.2cm, placed in a 1000mL beaker, 600mL of purified water was added, and the mixture was transferred to a 100℃ oil bath. 10mL of acetic acid was added, and the mixture was stirred at 200rpm for 12h for acid treatment. After the acid treatment solution was poured off, 600mL of purified water was added again, along with 10mL of sodium hydroxide. The mixture was then stirred at 200rpm for 12h in a 100℃ oil bath for alkali treatment. After cooling to room temperature, the suspension was vacuum filtered three times using a 0.22μm filter membrane. The solid residue was transferred to a volumetric flask, and deionized water was added to prepare a 10% (w / w) balsa wood pulp.

[0026] Preparation of S2 hydrogel precursor solution: Take 50 mL of balsa wood pulp obtained in step S1 into a beaker, add 1 g chitosan, 1 g glacial acetic acid and 1 g hydrochloric acid, and stir at 200 rpm for 10 min; then add 0.1 g piperazine and 0.1 g carbon nanotubes, and continue stirring at 200 rpm for 10 min; finally add 0.6 mL glutaraldehyde, stir for 3 min to initiate aldol condensation reaction, and obtain hydrogel precursor solution.

[0027] S3 Cryogenic Molding: The hydrogel precursor liquid is injected into a multi-needle tip mold (needle tip cone angle 20°, length 1.5cm, spacing 2.5cm), the inner wall of the mold is coated with polytetrafluoroethylene release agent, and frozen at -4℃ for 24h; after freezing, the mold is demolded and thawed naturally to obtain a multi-needle tip saline-alkali land treatment evaporator.

[0028] Example 2

[0029] In Example 1, the mold needle tip cone angle in step S3 is changed to 15°, the length is changed to 0.8cm, and the spacing is changed to 1.5cm. The remaining steps are the same as in Example 1.

[0030] Example 3

[0031] In Example 1, the mold needle tip cone angle in step S3 is changed to 30°, the length is changed to 2.2cm, and the spacing is changed to 3.5cm. The remaining steps are the same as in Example 1.

[0032] Comparative Example 1

[0033] A balsamic-based hydrogel was prepared according to the method in Example 1. The hydrogel precursor liquid was injected into a block mold and frozen to obtain a conventional block evaporator without a needle tip structure.

[0034] To verify the practical application performance of the evaporator of the present invention, tests were conducted on the evaporators of Examples 1-3 and Comparative Example 1, including tests on salt crystal distribution, continuous working performance, desalination rate, and salt crystal recovery. The test environment was a 10% sodium chloride solution simulating saline-alkali land, and the light condition was 1 solar intensity (100mW / cm²).

[0035] Each evaporator was placed in the test solution for continuous solar evaporation experiments. The location and coverage of salt crystal precipitation were observed and recorded at regular intervals. The results showed that: after 5 hours of operation, the conventional block evaporator in Comparative Example 1 had a large area of ​​salt crystal covering its photothermal interface, with a coverage area of ​​more than 80%, completely blocking the water transport channel; while after 15 hours of continuous operation, the multi-spined needle-tip evaporator in Example 1 only had salt crystal precipitation at the conical needle tip, with no salt crystal accumulation on the surface of the block substrate. The evaporators in Examples 2 and 3 also showed the same salt crystal distribution pattern, with salt crystal precipitation only at the needle tip. This proves that the multi-spined needle-tip structure of the present invention can effectively achieve spatial isolation between salt crystal and the photothermal interface.

[0036] like Figure 2 The results of continuous operation show that: the conventional block evaporator of Comparative Example 1 had an evaporation efficiency of less than 50% after 5 hours and basically lost its evaporation capacity after 10 hours; the evaporator of Example 1 maintained an evaporation efficiency of more than 85% after 15 hours, and even after 20 hours of operation, the efficiency could still be maintained at 70%, showing excellent continuous operation performance; the evaporators of Example 2 and Example 3 maintained an evaporation efficiency of 80% and 75% respectively after 15 hours, which was slightly lower than that of Example 1. This is because the difference in the parameters of the cone angle and length of the needle tip affected the smoothness of salt crystal shedding. It can be seen that a cone angle of 20°, a length of 1.5 cm, and a spacing of 2.5 cm is the optimal parameter combination for the needle tip structure.

[0037] The evaporator of Example 1 was tested in a 10% sodium chloride solution. The test results showed that the desalination rate increased linearly with the increase of working time, reaching 65% after 15 hours and further increasing to 72% after 20 hours. At the same time, the salt crystals precipitated at the needle tip fell off by gravity and could be passively recovered. The amount of salt crystals recovered after 15 hours was 120g and after 20 hours was 180g. Moreover, the recovered salt crystals had high purity and could be directly used as industrial salt raw materials. This fully demonstrates that the evaporator of this invention has the dual advantages of desalination efficiency and resource recovery in the treatment of saline-alkali land.

[0038] This embodiment is merely an illustrative description of the present patent and does not limit its scope of protection. Those skilled in the art may make partial modifications to it. As long as they do not exceed the spirit and essence of the present patent, they shall be regarded as equivalent substitutions to the present patent and shall be within the scope of protection of the present patent.

Claims

1. A multi-pronged tip type saline-alkali soil treatment evaporator, characterized in that, A balsa wood-based hydrogel is prepared by mold freezing forming, comprising an integrated block matrix and a plurality of conical needle tip structures; the conical needle tip structures are uniformly distributed on the upper surface of the block matrix, the needle tip cone angle is 12°-35°, the length is 0.8cm-2.2cm, and the distance between adjacent needle tips is 1.5cm-3.5cm.

2. The evaporator of claim 1, wherein, The balsa wood-based hydrogel is composed of 45-55 parts of balsa wood pulp, 0.8-1.2 parts of chitosan, 0.8-1.2 parts of glacial acetic acid, 0.8-1.2 parts of hydrochloric acid, 0.08-0.12 parts of piperazine, 0.08-0.12 parts of carbon nanotubes, and 0.5mL-0.7mL of glutaraldehyde.

3. The evaporator of claim 2, wherein, The balsa wood pulp is a cellulose suspension obtained by vacuum filtration after acetic acid treatment and sodium hydroxide treatment of balsa wood, and the weight fraction is 8%-12%.

4. The evaporator preparation method according to any one of claims 1 to 3, characterized in that, The method comprises the following steps: S1. Preparation of balsa wood pulp: cut the balsa wood into small pieces, add acetic acid in pure water under 100℃ oil bath condition, stir at a speed of 180-220rpm for 10-14h for acid treatment; after pouring the acid treatment liquid, add sodium hydroxide in pure water under 100℃ oil bath condition, stir at the same speed for 10-14h for alkali treatment; after cooling to room temperature, vacuum filter the suspension for 3-5 times, and take the solid residue to prepare balsa wood pulp with a weight fraction of 8%-12% by adding deionized water; S2. Preparation of hydrogel precursor liquid: take the balsa wood pulp prepared in step S1, add chitosan, glacial acetic acid and hydrochloric acid, stir at a speed of 180-220rpm for 8-12min; then add piperazine and carbon nanotubes, continue to stir at this speed for 8-12min; finally, add glutaraldehyde, stir for 2-5min to initiate the aldol condensation reaction, and obtain the hydrogel precursor liquid; S3. Freeze forming: inject the hydrogel precursor liquid prepared in step S2 into a multi-pronged needle tip mold, freeze at-6--2℃ for 20-28h; after freezing, demold and naturally thaw, and obtain the multi-pronged needle tip type saline-alkali soil treatment evaporator.

5. The method of claim 4, wherein the evaporator is prepared by, In step S1, the oil bath temperature fluctuation range of acid treatment and alkali treatment is not more than ±2℃, and vacuum filtration is used for filtration, and the filter membrane pore size is 0.22μm.

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