Saline-alkali soil leacheate evaporation, concentration and carnallite crystallization integrated device

Abstract

A saline-alkali soil leacheate evaporation concentration carnallite crystallization integrated device comprises a bottom box with the upper surface open, and an inner cavity of the bottom box is divided into a purification concentration area, a sand filtering area and an evaporation crystallization area; the purification and concentration area is as high as one side edge of the sand filtration area, the purification and concentration area is communicated with the sand filtration area through a water inlet pipeline, the evaporative crystallization area is as high as the other side edge of the sand filtration area and is lower than the purification and concentration area, and a water inlet is formed in the side wall of the purification and concentration area; a water vapor condensation cover plate and a solar photovoltaic panel cover the bottom box, the water vapor condensation cover plate and the solar photovoltaic panel are reversely laid in a herringbone shape, and a fresh water collection tank is arranged on the inner wall of the bottom box below the bottom edge of the water vapor condensation cover plate. The seven technological processes of light coagulation, photo-catalytic oxidation, evaporation concentration, precipitation, filtration, salt crystallization and fresh water recovery are organically integrated and fused in a single device for completion for the first time, and high integration of equipment functions is achieved.

Description

Technical Field

[0001] This invention belongs to the field of saline-alkali land leachate treatment technology, specifically relating to an integrated device for evaporation, concentration, and crystallization of mixed salts from saline-alkali land leachate. Background Technology

[0002] Current technologies for treating saline-alkali land leachate face multiple systemic defects. First, the evaporation process presents a contradiction between high energy consumption and strong dependence: traditional evaporation ponds or mechanical evaporation devices (such as multi-effect evaporation and MVR) consume large amounts of fossil fuels or electricity, with energy costs accounting for 60%–80%. Natural evaporation is significantly affected by climate fluctuations, with efficiency decreasing by 30%–50% under low temperature, high humidity, or rainy conditions, leading to prolonged treatment cycles and inefficient use of land resources. Second, the mixed crystallization of mixed salts severely restricts resource utilization: the leachate contains multiple ionic components (Na+, Na ... + Cl - SO4 2- Ca 2+ Due to the small differences in crystallization kinetics, eutectic mixtures are easily formed. Existing equipment lacks a stepwise crystallization control mechanism, and the purity of the products is generally below 70%, failing to meet industrial salt standards (e.g., NaCl ≥ 97%, GB / T 5462-2015), forcing most to be disposed of by landfill. Furthermore, environmental risks continue to emerge: leakage of incompletely solidified concentrate may cause groundwater pollution (TDS > 100 g / L, containing heavy metal residues), and open-air stockpiling of mixed salts exacerbates salt dust diffusion and secondary salinization of surrounding soils. Finally, the decentralized nature of the system increases space costs: distributed treatment processes require multiple units connected in series, increasing infrastructure investment by more than 40%, while natural evaporation ponds occupy 2–5 m³ / m² per unit capacity, with land occupation issues being particularly severe in low-evaporation areas. Summary of the Invention

[0003] To address the aforementioned problems, the present invention aims to provide an integrated device for evaporation, concentration, and crystallization of mixed salts from saline-alkali land leachate, which solves the technical problems of high energy dependence, complex salt crystallization process, large footprint, high risk of secondary pollution, and significant interference from organic matter in leachate treatment.

[0004] To achieve the above objectives, the technical solution adopted by the present invention includes: An integrated device for evaporation, concentration, and crystallization of mixed salts from saline-alkali land leachate includes a bottom box with an open upper surface. The inner cavity of the bottom box is divided into a purification and concentration zone, a sand filtration zone, and an evaporation and crystallization zone from one side to the other. A first scraper conveyor is installed at the bottom of the purification and concentration zone, and a second scraper conveyor is installed at the bottom of the evaporation and crystallization zone. The height of the purification and concentration zone is the same as the height of one side of the sand filtration zone. The purification and concentration zone and the sand filtration zone are connected by a water inlet pipe, and a water pump is installed on the water inlet pipe. The height of the evaporation and crystallization zone is the same as the height of the other side of the sand filtration zone and lower than the height of the purification and concentration zone. A water inlet is provided on the side wall of the purification and concentration zone. A water vapor condensation cover and a solar photovoltaic panel are installed on top of the bottom box. The water vapor condensation cover and the solar photovoltaic panel are laid in a "V" shape. Sealing plates are installed perpendicular to the two sides of the bottom box at the included angle of the water vapor condensation cover and the solar photovoltaic panel. A fresh water collection tank is provided on the inner wall of the bottom box below the bottom edge of the water vapor condensation cover. A fresh water outlet is connected to the outer side wall of the end of the fresh water collection tank.

[0005] Preferably, multiple ultrasonic generators and electric heating modules are arranged at the bottom of the purification and concentration zone and the evaporation and crystallization zone.

[0006] Preferably, the laying density of the ultrasonic generator is 3-5m² / unit.

[0007] Preferably, the bottom angle of the water vapor condensation cover plate is 30°~75°.

[0008] Preferably, the length-to-width ratio of the purification and concentration zone is 2 to 3:1, the sidewall depth is at least 1.1m, and a photothermal catalytic material layer is arranged on the upper part of the rinsing liquid.

[0009] Preferably, a filter bed is provided in the sand filtration zone, the length-to-width ratio of the sand filtration zone is 5~10:1, one side of the sand filtration zone is at the same height as the purification and concentration zone, and the other side of the sand filtration zone is flush with the bottom of the freshwater collection tank.

[0010] Preferably, the length-to-width ratio of the evaporation crystallization zone is 4~6:1, and the length ratio of the same purification and concentration zone is 1:5~6.

[0011] Preferably, the sealing plate on one side of the purification and concentration zone is equipped with a slag outlet.

[0012] Preferably, the sealing plate on one side of the evaporation and crystallization zone is provided with a salt outlet.

[0013] A method for treating impurities and crystallizing salts from evaporation and concentration of leachate from saline-alkali land, based on the integrated device for evaporation, concentration, and crystallization of impurities and salts from saline-alkali land leachate disclosed in this application, specifically includes the following steps: S1, the rinsing solution enters the purification and concentration zone through the inlet. The photothermal catalytic material layer is suspended on the upper surface of the rinsing solution. Under solar radiation, the efficient evaporation of water and photocatalytic degradation of organic matter in the rinsing solution are achieved simultaneously. When the water level in the purification and concentration zone drops to about 1 / 5 of the inlet water depth, the rinsing solution is replenished through the inlet until the TDS of the rinsing solution reaches 150g / L~250g / L. Then the water replenishment is stopped, and the concentrated rinsing solution is obtained. S2, the concentrated rinsing liquid is pumped to the sand filtration zone through the inlet pipe by the bottom water pump. S1 is repeated again after all the rinsing liquid in the purification and concentration tank has entered the sand filtration zone. S3, after the suspended solids in the concentrated rinsing liquid are intercepted by the filter bed in the sand filtration zone, the clear liquid flows into the evaporation and crystallization zone from the other side of the sand filtration zone. In the crystallization zone, the clear liquid is further evaporated and concentrated until salt is precipitated. During this period, the purification and concentration zone operates synchronously with the sand filtration zone and continuously supplies clear liquid to the crystallization zone. S4, when the salt precipitation in the crystallization zone reaches a thickness of 2-3 cm, drive the second scraper to directionally push the precipitated salt to the salt outlet for collection; S5. Throughout the process, water vapor condenses on the inner surface of the water vapor condensation cover and migrates along the water vapor condensation cover to the fresh water collection tank under the action of gravity, and is finally recycled and reused from the outlet. When there is a certain thickness of sediment at the bottom of the purification and concentration zone, the first scraper is started to push the sediment to the slag outlet, and then it is manually removed through the slag outlet.

[0014] Compared with the prior art, the advantages of the present invention are: (1) The present invention provides an integrated device for evaporation, concentration and crystallization of mixed salts from saline-alkali land leachate. Through the rational design of the component structure, the device optimizes the utilization of solar energy resources and achieves all-weather operation. During the day, the device uses solar energy for catalytic degradation of organic matter and photo-flocculation and precipitation of colloidal particles. At the same time, the excess solar energy is converted into electrical energy by the photovoltaic system for storage. At night, the stored electrical energy is used to start the electric auxiliary heating system to heat the leachate and maintain it at 40±5℃. The significant temperature difference is formed by taking advantage of the low temperature environment at night, thereby efficiently driving the evaporation of the leachate and the recovery of condensate.

[0015] (2) The present invention provides an integrated device for evaporation, concentration and crystallization of mixed salts in saline-alkali land leaching liquid. Through the rational setting of component structure, it is the first to organically integrate seven processes, namely photocoagulation, photocatalytic oxidation, evaporation and concentration, precipitation, filtration, salt crystallization and freshwater recovery, into a single device, thereby achieving a high degree of integration of equipment functions. The freshwater resources generated by the device can be reused on-site for leaching and desalination of saline-alkali land. Compared with the traditional one-time leaching method, it saves 60% to 85% of water. The obtained salt can be further purified and utilized as a resource.

[0016] (3) The integrated device for evaporation, concentration and crystallization of mixed salts in saline-alkali land leaching liquid of the present invention preferably uses an α-Fe2O3 / porous carbon-based suspension composite material layer as the photothermal catalytic material layer. Its solar light absorption rate exceeds 95%, which improves the comprehensive utilization rate of solar energy by more than 40% compared with the traditional evaporator, and at the same time achieves a 60% to 80% reduction in energy consumption. At the same time, the material has a low density and can be suspended on the water surface and automatically adjust its position according to the change of water level, realizing the efficient utilization of sunlight, giving full play to the high photothermal conversion efficiency of the material and the photocatalytic degradation efficiency of organic matter, realizing the efficient utilization of sunlight, and greatly improving the photothermal conversion efficiency of the material and the photocatalytic degradation efficiency of organic matter.

[0017] (4) The present invention provides a method for treating mixed salt crystallization by evaporation and concentration of leachate from saline-alkali land. The system operates in a day-night coordinated manner, utilizing efficient photothermal materials to degrade organic pollutants and achieve coagulation and sedimentation of colloidal particles, while simultaneously converting excess solar energy into electrical energy for storage. At night, the system activates electric auxiliary heating to precisely control the water temperature in the core area at 40±5℃. The "nighttime supplementary heating" design achieves two goals at once. Attached Figure Description

[0018] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof. In the drawings: Figure 1 This is a schematic diagram of the integrated device for evaporation, concentration, and crystallization of mixed salts from saline-alkali land leaching solution according to the present invention. Figure 2 for Figure 1 The main view; Figure 3 for Figure 1 The left view; Figure 4 for Figure 1 Top view; Figure 5 for Figure 4 Sectional view of section AA; Figure 6 for Figure 4 A sectional view of section BB in the middle.

[0019] The labels in the diagram represent: 1. Slag outlet, 2. Purification and concentration zone, 3. Sand filtration zone, 4. Evaporation and crystallization zone, 5. Freshwater collection tank, 6. Solar photovoltaic panel, 7. Water vapor condensation cover plate, 8. Ultrasonic generator, 9. Water inlet, 10. First scraper conveyor, 11. Second scraper conveyor, 12. Freshwater outlet, 13. Electric heating module, 14. Photothermal catalytic material layer, 15. Salt outlet, 16. Water inlet pipe, 17. Water pump, 18. Sealing plate. Detailed Implementation

[0020] The invention is not limited to the following specific embodiments. All equivalent modifications made based on the technical solutions of this application fall within the protection scope of this invention.

[0021] It should be noted that the directional terms mentioned herein are consistent with the specific directions on the paper in the accompanying drawings or the corresponding directions of the space shown in the drawings; all components and devices in this invention, unless otherwise specified, are components and devices known in the prior art.

[0022] Example 1 This embodiment discloses an integrated device for evaporation, concentration, and crystallization of impurities in saline-alkali land leachate. It includes a bottom box with an open upper surface. The inner cavity of the bottom box is divided into a purification and concentration zone 2, a sand filtration zone 3, and an evaporation and crystallization zone 4 from one side to the other. A first scraper conveyor 10 is installed at the bottom of the purification and concentration zone 2, and a second scraper conveyor 11 is installed at the bottom of the evaporation and crystallization zone 4. The height of the purification and concentration zone 2 is equal to the height of one side of the sand filtration zone 3. The purification and concentration zone 2 and the sand filtration zone 3 are connected by a water inlet pipe 16, and a water pump is installed on the water inlet pipe 16. The height of the evaporation and crystallization zone 4 is equal to the height of one side of the sand filtration zone 3. The other side of the sand filtration zone 3 is at the same height as and lower than the height of the purification and concentration zone 2. The side wall of the purification and concentration zone 2 is provided with a water inlet 9. A water vapor condensation cover 7 and a solar photovoltaic panel 6 are installed on top of the bottom box. The water vapor condensation cover 7 and the solar photovoltaic panel 6 are laid in a "V" shape. The two sides of the water vapor condensation cover 7 and the solar photovoltaic panel 6 are perpendicular to the two sides of the bottom box and are provided with sealing plates 18. A fresh water collection tank 5 is provided on the inner wall of the bottom box below the bottom edge of the water vapor condensation cover 7. The fresh water collection tank 5 is connected to a fresh water outlet 12 on the outer side wall of the end of the side wall. Its function is as follows: By integrating the solar photovoltaic panel 6 and the water vapor condensation cover 7 in a "V"-shaped structure, the solar panels maximize light collection while optimizing space utilization and ensuring efficient freshwater collection. This optimizes the device's utilization of solar energy resources, enabling all-weather operation. During the day, the device utilizes solar energy for the catalytic degradation of organic matter and the photo-flocculation and precipitation of colloidal particles. Simultaneously, excess solar energy is converted into electrical energy by the photovoltaic system for storage. At night, the stored electrical energy is used to activate the electric auxiliary heating system, heating the leachate and maintaining it at 40±5℃. The significant temperature difference created by the low nighttime environment efficiently drives the evaporation of the leachate and the recovery of condensate. This successfully solves two major technical bottlenecks in the practical application of traditional solar evaporation devices: firstly, abundant solar energy during the day, but a small internal and external temperature difference, making water vapor condensation and recovery difficult; secondly, lack of sunlight at night, although the internal and external temperature difference meets the conditions for water vapor condensation and recovery for a short time, lacks the driving force for continuous water vapor evaporation.

[0023] This innovative device organically integrates seven processes—photocoagulation, photocatalytic oxidation, evaporation concentration, sedimentation, filtration, salt crystallization, and freshwater recovery—into a single unit, achieving a high degree of equipment integration. The freshwater generated by the device can be reused on-site for leaching desalination of saline-alkali land, saving 60% to 85% of water compared to the traditional single-stage leaching method. The obtained salt can be further purified and utilized as a resource.

[0024] In this embodiment, the water vapor condensation cover 7 is preferably made of quartz glass, which greatly improves light transmittance. In this embodiment, a water vapor condensation cover 7 parallel to the solar photovoltaic panel 6 is preferably also provided below it. That is, the two water vapor condensation cover plates 7, the two sealing plates 18 and the bottom box form a relatively sealed space, so that the inner cavity of the integrated device in this embodiment is sealed. At the same time, the water vapor condensation cover 7 below the solar photovoltaic panel 6 can also support and protect the solar photovoltaic panel 6 from the bottom to prevent it from getting damp.

[0025] In this embodiment, both the first scraper conveyor 10 and the second scraper conveyor 11 are existing, known equipment.

[0026] In this embodiment, multiple ultrasonic generators 8 and electric heating modules 13 are arranged on the inner bottom below the bottom of the purification and concentration zone 2 and the evaporation and crystallization zone 4. The ultrasonic generators 8 are used to perform ultrasonic cleaning when the bottom of the pool is cleaned periodically. The electric heating modules 13 are an auxiliary heating system for nighttime use, maintaining the water temperature at night to ensure continuous evaporation. The ultrasonic generators 8 are laid at a density of 3-5 m² / unit. The ultrasonic generators 8 are existing and known equipment. The electric heating modules 13 are preferably optional industrial submersible heating rods.

[0027] In this embodiment, the bottom angle of the water vapor condensation cover plate 7 is 30°~75°.

[0028] In this embodiment, the purification and concentration zone 2 has an aspect ratio of 2 to 3:1 and a sidewall depth of at least 1.1m. A photothermal catalytic material layer 14 is laid on the upper part of the rinsing liquid. In this embodiment, the photothermal catalytic material layer 14 is preferably an α-Fe2O3 / porous carbon-based suspension composite material layer with a solar light absorption rate of over 95%. This improves the comprehensive utilization rate of solar energy by more than 40% compared to traditional evaporators, while achieving a 60% to 80% reduction in energy consumption. It overcomes the technical bottleneck of poor sunlight penetration in water and low solar light utilization efficiency when the photothermal catalytic material layer 14 is laid at the bottom of the device. At the same time, the material has a low density and can float on the water surface, automatically adjusting its position according to changes in water level, thus achieving efficient utilization of sunlight. It fully utilizes the high photothermal conversion efficiency of the material (at an ambient temperature of 20°C, the composite material floating on the water surface can heat up from 19.2°C to 40°C in 30 minutes under natural sunlight) and the photocatalytic degradation efficiency of organic matter, achieving efficient utilization of sunlight and greatly improving the photothermal conversion efficiency of the material and the photocatalytic degradation efficiency of organic matter.

[0029] In this embodiment, the α-Fe2O3 / porous carbon-based suspension composite material layer uses melamine sponge produced by Chengdu Outlet Co., Ltd. as the experimental raw material. The foamed carbon is obtained by carbonization at a temperature of 300-500℃ for 0.5-8 hours. The foamed carbon is then soaked in a 0.5-3 mmol / L ferric nitrate solution and stirred for 60 min. The reaction system is then placed in a reaction vessel and hydrothermally treated at 120℃ for 6-24 h. After cooling, the adsorbed products on the surface are washed with pure water, and then dried at 60℃ to obtain the α-Fe2O3 / porous carbon-based suspension composite material layer.

[0030] In this embodiment, a filter bed is provided in the sand filter zone 3. The length-to-width ratio of the sand filter zone 3 is 5~10:1. One side of the sand filter zone 3 is at the same height as the purification and concentration zone 2, and the other side of the sand filter zone 3 is flush with the bottom of the fresh water collection tank 5.

[0031] The distribution of each layer in the filter bed in this embodiment is shown in Table 1: Table 1 Examples of filter bed levels

[0032] In this embodiment, the aspect ratio of the evaporation crystallization zone 4 is 4~6:1, and the length ratio of the same purification and concentration zone 2 is 1:5~6.

[0033] In this embodiment, the sealing plate 18 on one side of the purification and concentration zone 2 is provided with a slag outlet 1, and the sealing plate 18 on one side of the evaporation and crystallization zone 4 is provided with a salt outlet 15.

[0034] This embodiment also discloses a method for treating mixed salt crystallization by evaporation and concentration of leachate from saline-alkali land, which specifically includes the following steps: S1, the rinsing solution enters the purification and concentration zone 2 through the inlet 9. The photothermal catalytic material layer 14 is suspended on the upper surface of the rinsing solution. Under solar radiation, the efficient evaporation of water and photocatalytic degradation of organic matter in the rinsing solution are realized simultaneously. When the water level in the purification and concentration zone 2 drops to about 1 / 5 of the inlet water depth, the rinsing solution is replenished through the inlet 9 until the TDS (total dissolved solids) of the rinsing solution reaches 150 g / L~250 g / L. The water replenishment is then stopped, and the concentrated rinsing solution is obtained. S2, the concentrated rinsing liquid is pumped to the sand filter zone 3 through the inlet pipe 16 by the bottom water pump 17. S1 is repeated again after all the rinsing liquid in the purification and concentration tank has entered the sand filter zone. S3, after the suspended solids in the concentrated rinsing liquid are intercepted by the filter bed in the sand filter zone 3, the clear liquid flows into the evaporation and crystallization zone 4 from the other side of the sand filter zone 3. In the crystallization zone 4, the clear liquid is further evaporated and concentrated until salt is precipitated. During this period, the purification and concentration zone 2 operates synchronously with the sand filter zone 3 and continuously supplies clear liquid to the crystallization zone 4. S4, when the salt precipitation in the crystallization zone 4 reaches a thickness of 2-3 cm, drive the second scraper 11 to directionally push the precipitated salt to the salt outlet 15 for collection. S5, throughout the process, water vapor condenses on the inner surface of the water vapor condensation cover plate 7 and migrates along the water vapor condensation cover plate 7 to the fresh water collection tank 5 under the action of gravity, and is finally recycled and reused by the outlet 12; When there is a certain thickness of sediment at the bottom of the purification and concentration zone 2, the first scraper 10 is started to push the sediment to the slag outlet 1, and then it is manually removed through the slag outlet 1.

[0035] The entire system operates in a day-night coordinated manner: This invention is a fully solar-powered day-night coordinated operation device. During the day, the device acts as both an energy "producer" and "processing plant": it utilizes highly efficient photothermal materials to degrade organic pollutants and achieve coagulation and sedimentation of colloidal particles, while simultaneously converting excess solar energy into stored electrical energy. At night, the system activates auxiliary electric heating to precisely control the water temperature in the core area at 40±5℃. The "nighttime supplementary heating" design achieves two goals at once: First, it utilizes the low ambient temperature at night to artificially create a significant temperature difference between the inside and outside, allowing water vapor to condense efficiently into fresh water on the inner wall of the device, greatly improving the evaporation rate and fresh water yield; second, by stabilizing the temperature, it cleverly prevents salt from rapidly precipitating in the evaporation and crystallization zone due to nighttime cooling, forming inferior microcrystals, and guides it to slowly form high-quality crystals with regular morphology and higher purity.

[0036] Example 2 An integrated device for evaporation, concentration, and crystallization of mixed salts from saline-alkali land leachate is disclosed. The steam condenser cover plate 7 has angles of 30°, 40°, 50°, and 60°. The device is installed in Xi'an City, Shaanxi Province. The highest daily air temperature was 33°C, the highest water temperature was 42.1°C, the lowest air temperature was 17.2°C, and the lowest water temperature was 17.9°C. The water depth in the device was 10 cm, and the total water volume was 10 L. Table 2 shows the data records during the device's operation, with the data representing the cumulative freshwater collection. Table 2 Freshwater collection volume at different cover angles during device operation.

[0037] As shown in Table 2, freshwater collection mainly occurs at night (20:00-8:00 the next day). The adjustable cover design of this device can be flexibly designed according to the climate type and site conditions of the actual location. At the installation location of this device, the amount of freshwater collected gradually increases as the cover angle increases. When the cover angle continues to increase, on the one hand, the cover area will increase by 1.9 times. On the other hand, the wind force at the device installation site is relatively large, which will increase the wind-receiving area and increase instability. Therefore, this embodiment only selected 60°.

[0038] Example 3 An integrated purification, concentration, and crystallization device for saline-alkali land leachate combining photothermal composite catalytic materials was developed. The steam condenser cover plate 7 has an angle of 60°. The device was installed in Xi'an, Shaanxi Province, with a water depth of 10cm and an inlet water volume of 10L. The device was continuously operated under sunlight until the TDS reached 150g / L. The observed data are shown in Table 3 below. Table 3. Freshwater treatment status of the device at different time periods

[0039] Table 3 shows that the present invention can achieve relatively stable freshwater collection during a 20-day operation period, with an average daily water production of approximately 500 mL. It also effectively concentrates the eluent, demonstrating good overall operational stability. Under the action of the composite material, the system exhibits significant COD removal capacity, and the trend of COD concentration change in the concentrate indicates that the material continuously plays a catalytic degradation role during evaporation, rather than simple initial adsorption or a one-time reaction. Throughout the process, the turbidity of the eluent remains at a low level, indicating the excellent photocoagulation effect of this invention.

[0040] Example 4 The α-Fe2O3 / porous carbon-based suspension composite material used in this embodiment was fixed at the bottom of the water layer. The water depth was varied, and the material was exposed to sunlight for 12 hours. The COD removal effect is shown in Table 4. The composite material was then placed on the water surface and fixed at the bottom (sunlight penetration depth 10 cm, i.e., water depth 10 cm), both under the same environment and exposed to sunlight for 180 minutes. The temperature of both materials was continuously measured during this period, and the results are shown in Table 5. Table 4. Effect of different light penetration depths on COD removal

[0041] Table 5. Photothermal effects at different locations on the composite material

[0042] Table 4 shows that after 12 hours of illumination, the intensity of sunlight penetrating the water layer decreases with increasing penetration depth, resulting in a significant decline in COD removal efficiency. Table 5 shows that when the material is placed on the upper part of the water layer, its heating rate and final temperature are both higher than when it is placed on the bottom. The results in Tables 4 and 5 demonstrate that the composite material used in this invention overcomes the technical bottleneck of poor sunlight penetration in water and low solar energy utilization efficiency when the photothermal material is laid at the bottom of the device.

[0043] Comparative Example To verify the synergistic technical effect of the present invention and the nonlinear enhancement effect between the modules, simulation experiments were conducted to compare the device of the present invention with several comparative schemes. Using the controlled variable method, the effects of the presence mode of the photothermal composite catalytic material and the setting of the photovoltaic energy storage-nighttime heating module on evaporation efficiency, COD removal rate, and salt crystallization purity were investigated.

[0044] I. Experimental Apparatus and Conditions All experiments used the same experimental apparatus with the same structure and dimensions as in Example 3. The length-to-width ratio of the purification and concentration zone was 2.5:1, the water depth was 10 cm, and the total water volume was 10 L. The cover angle was set to 60°, and the cover material was quartz glass.

[0045] The experiment was conducted in Xi'an, Shaanxi Province, over a period of seven consecutive sunny days with an average daily solar irradiance of approximately 800 W / m², an average daytime ambient temperature of 30 ± 3℃, and an average nighttime temperature of 16 ± 2℃. The apparatus operated under natural light during the day and different operating modes were set for each experimental group at night. Each experimental group had three parallel samples (n=3), and the average value was taken.

[0046] The initial leaching solution was a sample collected in situ from saline-alkali land, with an initial COD of 72 mg / L, TDS of approximately 2.3 g / L, and turbidity of 5.7 NTU.

[0047] II. Experimental Grouping Table 6 Experimental Groups

[0048] III. Testing and Measurement Methods COD: The potassium dichromate method (HJ828-2017) was used, and samples were taken once daily at 08:00. TDS: YSI-EC300A conductivity meter; Freshwater production: Weigh the volume (mL) of condensate in the freshwater collection tank and record it daily; Temperature monitoring: thermometer; IV. Experimental Results (1) Cumulative freshwater collection and COD changes Table 7. Cumulative Freshwater Collection and COD Changes over 7 Days for Each Group

[0049] (2) Temperature rise curve of material surface Table 8. Comparison of temperature rise between suspended materials and bottom-fixed materials (under natural light)

[0050] V. Analysis of Experimental Results The cumulative freshwater collection volume of invention group A over 7 days was 3680mL, with a daily water production of 526mL / d, demonstrating the high evaporation and condensation efficiency of the device under the "photothermal catalysis + photovoltaic energy storage day and night heat replenishment" mode.

[0051] Although the bottom-fixed group C also has photothermal materials, the cumulative water production is slightly lower (3590mL) because the materials are located underwater and the light attenuation is significant.

[0052] The water production of group B without materials (3381 mL) was close to that of the first two groups, indicating that the evaporation effect under light alone can still produce a certain amount of fresh water. However, due to the lack of degradation pathways for internal organic matter, the COD increased significantly afterward.

[0053] The cumulative freshwater production of Group D without nighttime heating was only 1470 mL, with a daily water production of about 210 mL / d, which is only 40% of that of the invention group. This indicates that the energy storage-nighttime heating system plays a key role in the nighttime evaporation and condensation processes.

[0054] (2) COD variation pattern The COD change shows that the COD of invention group A decreased from 72.0 mg / L to 19.2 mg / L, a decrease of 73%, indicating that the photothermal composite catalytic material continuously carries out photocatalytic oxidation reaction during the evaporation and concentration process, effectively degrading organic matter and inhibiting enrichment.

[0055] The COD of the bottom-fixed group C decreased to 44.5 mg / L. Although it showed a certain degradation effect, it was lower than that of the invention group, indicating that the suspended arrangement structure can significantly enhance the light utilization rate and catalytic reaction rate.

[0056] The COD of group D without nighttime heating was 21.6 mg / L, which is close to that of the invention group, indicating that nighttime supplemental heating mainly affects the evaporation rate and has little effect on the degradation of organic matter.

[0057] The COD of group B without materials increased to 108.4 mg / L, an increase of about 1.5 times, indicating that in the absence of photocatalysis, water evaporation led to a significant concentration of organic matter, and the system exhibited the phenomenon of "enrichment of organic pollutants".

[0058] (3) Comprehensive comparison and synergistic effect analysis Compared to the bottom-fixed group, the invention group showed an approximately 45% increase in COD removal rate and a slightly higher freshwater collection rate of about 3%, indicating that the suspended design not only improves light absorption and heat utilization efficiency but also promotes the synergistic effect of photocatalytic reaction and evaporation. Compared to the group without nighttime heating, the invention group showed an approximately 150% increase in freshwater collection, demonstrating that photovoltaic energy storage and the nighttime heating system significantly contribute to the nighttime evaporation and condensation stage. The experiments in each group show that the photothermal catalytic material is responsible for "synergistic purification and photothermal evaporation," while nighttime heating is responsible for "thermal management and continuous evaporation power," together forming an all-weather operating system.

[0059] In summary, comparative experiments demonstrate that the device of this invention exhibits significantly superior overall performance compared to the comparative examples under the same light and environmental conditions. This improvement in technical effectiveness is not due to the linear superposition of a single module, but rather to the synergistic effect of multiple physical fields among the suspended photothermal catalytic layer, day-night coordinated thermal management, and the integrated sand filtration-crystallization system. This synergistic effect significantly improves the device's evaporation efficiency, COD removal capacity, and salt purity, demonstrating outstanding substantive features and significant technological advancements, which are not readily apparent.

[0060] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0061] Furthermore, the various implementation methods disclosed in this solution can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content invented by this disclosure.

Claims

1. An integrated device for evaporation, concentration, and crystallization of mixed salts from saline-alkali land leachate, characterized in that, The bottom box includes an open top surface. The inner cavity of the bottom box is divided into a purification and concentration zone (2), a sand filtration zone (3), and an evaporation and crystallization zone (4) from one side to the other. The bottom of the purification and concentration zone (2) is equipped with a first scraper (10), and the bottom of the evaporation and crystallization zone (4) is equipped with a second scraper (11). The height of the purification and concentration zone (2) is the same as the height of one side of the sand filter zone (3). The purification and concentration zone (2) and the sand filter zone (3) are connected by a water inlet pipe (16), and a water pump (17) is provided on the water inlet pipe (16). The height of the evaporation and crystallization zone (4) is the same as the height of the other side of the sand filter zone (3) and lower than the height of the purification and concentration zone (2). The side wall of the purification and concentration zone (2) is provided with a water inlet (9). The bottom box is covered with a water vapor condensation cover plate (7) and a solar photovoltaic panel (6), and the water vapor condensation cover plate (7) and the solar photovoltaic panel (6) are laid in a "V" shape. The two sides of the water vapor condensation cover plate (7) and the solar photovoltaic panel (6) are perpendicular to the two sides of the bottom box and are provided with sealing plates (18). The inner wall of the bottom box below the bottom edge of the water vapor condensation cover plate (7) is provided with a fresh water collection tank (5), and the outer side wall of the end of the fresh water collection tank (5) is connected to a fresh water outlet (12).

2. The integrated device for evaporation, concentration, and crystallization of mixed salts from saline-alkali land leaching solution as described in claim 1, characterized in that, Multiple ultrasonic generators (8) and electric heating modules (13) are arranged at the bottom of the purification and concentration zone (2) and the evaporation and crystallization zone (4).

3. The integrated device for evaporation, concentration, and crystallization of mixed salts from saline-alkali land leaching solution as described in claim 2, characterized in that... The laying density of the ultrasonic generator (8) is 3-5 m² / unit.

4. The integrated device for evaporation, concentration, and crystallization of mixed salts from saline-alkali land leaching solution as described in claim 3, characterized in that... The bottom angle of the water vapor condensation cover plate (7) is 30°~75°.

5. The integrated device for evaporation, concentration, and crystallization of impurities in saline-alkali land leachate as described in any one of claims 1-4, characterized in that, The purification and concentration zone (2) has an aspect ratio of 2 to 3:1 and a sidewall depth of at least 1.1 m. A photothermal catalytic material layer (14) is arranged on the upper part of the rinsing liquid.

6. The integrated device for evaporation, concentration, and crystallization of impurities in saline-alkali land leachate as described in claim 5, characterized in that, The sand filter zone (3) is equipped with a filter bed. The length-to-width ratio of the sand filter zone (3) is 5~10:

1. One side of the sand filter zone (3) is at the same height as the purification and concentration zone (2), and the other side of the sand filter zone (3) is flush with the bottom of the fresh water collection tank (5).

7. The integrated device for evaporation, concentration, and crystallization of impurities from saline-alkali land leaching solution as described in claim 6, characterized in that... The evaporation crystallization zone (4) has an aspect ratio of 4~6:1, and its length ratio to the purification and concentration zone (2) is 1:5~6.

8. The integrated device for evaporation, concentration, and crystallization of impurities in saline-alkali land leachate as described in claim 6, characterized in that, The sealing plate (18) on one side of the purification and concentration zone (2) is provided with a slag outlet (1).

9. The integrated device for evaporation, concentration, and crystallization of mixed salts from saline-alkali land leachate as described in claim 8, characterized in that... The sealing plate (18) on one side of the evaporation crystallization zone (4) is provided with a salt outlet (15).

10. A method for treating impurities and salts by evaporation, concentration, and crystallization of leachate from saline-alkali land, characterized in that... The integrated device for evaporation, concentration, and crystallization of mixed salts from saline-alkali land leachate as described in claim 9 specifically includes the following steps: S1, the rinsing liquid enters the purification and concentration zone (2) through the inlet (9). The photothermal catalytic material layer (14) is suspended on the upper surface of the rinsing liquid. Under solar radiation, the efficient evaporation of water in the rinsing liquid and the photocatalytic degradation of organic matter are realized simultaneously. When the water level in the purification and concentration zone (2) drops to about 1 / 5 of the inlet water depth, the rinsing liquid is replenished through the inlet (9) until the TDS of the rinsing liquid reaches 150 g / L~250 g / L and the water replenishment is stopped, and the concentrated rinsing liquid is obtained. S2, the concentrated rinsing liquid is pumped to the sand filter area (3) through the inlet pipe (16) by the bottom water pump (17). S1 is repeated again after all the rinsing liquid in the purification and concentration tank has entered the sand filter area. S3, after the suspended solids in the concentrated rinsing liquid are intercepted by the filter bed in the sand filtration zone (3), the clear liquid flows from the other side of the sand filtration zone (3) into the evaporation and crystallization zone (4), and the clear liquid is further evaporated and concentrated in the crystallization zone (4) until salt is precipitated. During this period, the purification and concentration zone (2) operates synchronously with the sand filtration zone (3) and continuously supplies clear liquid to the crystallization zone (4). S4, when the salt precipitation in the crystallization zone (4) reaches a thickness of 2~3cm, drive the second scraper (11) to directionally push the precipitated salt to the salt outlet (15) for collection; S5, throughout the process, water vapor condenses on the inner surface of the water vapor condensation cover plate (7) and migrates along the water vapor condensation cover plate (7) to the fresh water collection tank (5) under the action of gravity, and is finally recycled and reused by the outlet (12); When there is a certain thickness of sediment at the bottom of the purification and concentration zone (2), the first scraper (10) is started to push the sediment to the slag outlet (1), and then it is manually removed through the slag outlet (1).

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