A solar-powered device and method for desalinizing saline-alkali soil

Abstract

This invention discloses a solar-powered device and method for desalinizing saline-alkali soil, relating to the field of saline-alkali soil improvement. The device includes a solar power generation unit, a soil salt extraction unit, a soil extract cation and anion direct current separation unit, and a salt collection unit. The method involves: extracting saline from the saline-alkali soil with water, guiding the extract to the cation and anion direct current separation unit, where the anions and cations in the extract move towards their respective ends under the action of the anode and cathode electrodes. The high-concentration brine near the anode and cathode electrodes is then guided to a brine collection tank, while the liquid in the middle of the cation and anion direct current separation unit has a lower salt content and is recycled for further extraction of saline-alkali soil salt. The direct current power used in the device comes from solar photovoltaic panels, and the brine is heated and dried using solar energy.

Description

Technical Field

[0001] This invention relates to the field of saline-alkali land improvement, specifically to a solar-powered device and method for desalinizing saline-alkali land soil. Background Technology

[0002] Soil salinization refers to the accumulation of soluble salts in groundwater, fertilizers, and topsoil, leading to difficulties in crop growth and reduced yields. Due to fertilizer use and the impact of global climate change, the area of ​​salinized soils worldwide is continuously expanding and is considered a significant factor limiting global soil productivity, food security, and ecosystems. There are vast areas of saline-alkali land globally, reaching as high as 1.1 × 10⁻⁶. 9 hm 2 However, saline-alkali land is also an important reserve resource, and my country attaches particular importance to its improvement and management. Saline-alkali soils generally have a high cation content, especially sodium ions, which leads to soil compaction, deterioration of soil structure, and decline in fertility. Therefore, reducing the salinity content of saline-alkali soils is key to their management.

[0003] Methods for improving saline-alkali land mainly include biological improvement, chemical conditioning, physical methods, and water conservancy engineering. While water conservancy engineering and physical improvement (importing soil, constructing drainage, irrigation, and leaching systems) are relatively effective, they are costly and difficult to apply on a large scale. Furthermore, their effectiveness is affected by geological, hydrological, and meteorological factors. For example, in Xinjiang, where saline-alkali land is vast, the lack of abundant rainfall makes leaching and other methods difficult to implement and promote on a large scale. Biological improvement mainly involves planting salt-tolerant and salt-extracting plants, such as *Trichoderma tetragonum*, which can extract some salt. However, this method is time-consuming and its effects are unstable. Chemical improvement mainly reduces the activity of soluble sodium ions through acid-base neutralization and ion replacement. However, this method only addresses the symptoms, not the root cause, and cannot remove sodium ions from the soil. It also introduces a large amount of other ions, potentially exacerbating salinization. Additionally, adding biochar and organic fertilizers can also improve saline-alkali land, but this method cannot remove salt ions and can only mitigate their toxic effects to a certain extent. Therefore, there is a need to develop an effective and low-cost improvement method.

[0004] Removing saline-alkali ions from saline-alkali soils is a formidable challenge. Based on the principle of mutual attraction between cations and anions, it is possible to enrich and separate these cations from the soil solution. However, this method requires significant electricity consumption, necessitates the construction of power supply facilities, and requires AC-DC conversion equipment. Furthermore, saline-alkali lands are mainly concentrated in coastal areas and Xinjiang, making large-scale power infrastructure construction difficult and costly. Summary of the Invention

[0005] This invention provides a solar-powered device and method for desalinizing saline-alkali soil.

[0006] A solar-powered soil desalination device for saline-alkali land includes:

[0007] Solar power generation devices;

[0008] A direct current electrostatic separation device for anions and cations in soil extract, comprising: a separator; a cathode electrode and an anode electrode disposed on both sides of the separator, wherein the cathode electrode and the anode electrode are connected to the output terminal of the solar power generation device;

[0009] A soil salinity extraction device, wherein the soil salinity extraction device uses water to extract salinity from saline-alkali soil to obtain soil extract liquid, and outputs the soil extract liquid to the middle of the separator through a pipeline;

[0010] It is connected by pipeline to a salt collection device near the cathode and anode electrodes inside the separator.

[0011] This invention extracts salt from saline-alkali soil using water. The extracted liquid is then directed to a direct current electrostatic separation device for anions and cations. Under the action of the anode and cathode electrodes, the anions and cations in the extract move towards the two ends of the electrodes respectively. The high-concentration brine near the anode and cathode electrodes is then directed to a brine collection tank, while the liquid in the middle of the direct current electrostatic separation device has a lower salt content. This liquid is recycled to continue extracting salt from the saline-alkali soil. The direct current used in the device comes from solar photovoltaic panels, and the brine is heated and dried using solar energy.

[0012] The solar power generation device includes: a solar photovoltaic panel and a DC voltage regulator connected to the solar photovoltaic panel, wherein the DC voltage regulator serves as the output terminal of the solar power generation device and is electrically connected to the cathode electrode and the anode electrode.

[0013] The separator contains a cathode electrode blocking screen near the cathode electrode and an anode electrode blocking screen near the anode electrode.

[0014] The cathode electrode is located between the inner wall of the separator and the barrier screen of the cathode electrode;

[0015] The anode electrode is located between the inner wall of the separator and the barrier screen of the anode electrode.

[0016] The soil salinity extraction device includes:

[0017] Extraction container;

[0018] A filter screen installed on top of the extraction container for holding saline-alkali soil;

[0019] A water replenishment device that sprays water toward the filter screen.

[0020] The salt collection device includes:

[0021] Salt collection container;

[0022] A solar thermal panel that heats the salt collection container.

[0023] A solar-powered method for desalinizing saline-alkali land, employing a solar-powered desalinizing device, includes the following steps:

[0024] 1) Cover the saline-alkali soil onto the filter screen of the extraction container, spray water or citric acid solution onto the saline-alkali soil on the filter screen with a water supply device, and obtain soil extract by the soil salt extraction device.

[0025] The citric acid aqueous solution contains 0.1%-0.5% citric acid by mass, which results in high extraction efficiency and can also improve the high pH of saline-alkali land.

[0026] 2) The soil extract is transported through pipelines to the middle of the separator in the soil extract anion-cation direct current electrostatic separation device;

[0027] 3) The DC voltage regulator adjusts the voltage to 110-360V. Both the cathode and anode electrodes are graphite electrodes. Under the action of the cathode and anode electrodes, the cations in the soil extract move towards the cathode, while the anions move towards the anode. The solution rich in cations and anions is transferred to the salt collection device, where it is dried into solid salt under the solar thermal plate.

[0028] In step 1), both the cathode electrode and the anode electrode are 0.1-0.3 mm thick graphite electrodes. Compared with the prior art, the present invention has the following advantages:

[0029] This invention utilizes solar energy to directly provide DC power, which is green, pollution-free, and low-cost. The abundant solar energy resources in Xinjiang are particularly conducive to the large-scale application of this method. Furthermore, the device is portable, uses minimal water, and can provide a continuous solution for improving saline-alkali land. The generated salt byproducts can also be used as industrial raw materials, demonstrating promising application prospects. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the solar-powered desalination device for saline-alkali land. Detailed Implementation

[0031] like Figure 1As shown, a solar-powered desalination device for saline-alkali land includes a solar power generation device 1, a soil salt extraction device 13, a soil extract liquid anion and cation direct current separation device 3, and a salt collection device 10. The solar power generation device 1 includes a solar photovoltaic panel and a direct current voltage regulation device 2. The soil salt extraction device 13 can be placed on the ground surface with saline-alkali soil on top, or it can be inserted underground at a depth of 30-45cm. The extraction device contains a 2-5mm screen 12 to ensure that soil leachate enters the extraction device while preventing soil from falling in. The extraction device is connected to an extract liquid outlet 4 to transfer the salt-containing extract liquid to the soil extract liquid anion and cation direct current separation device (3). In addition, the extraction device is connected to a water inlet 7, which is mainly used for rinsing the salt in the saline-alkali soil. A water replenishment device 14 is also provided to replenish the water required for extraction. The soil extract anion-cation direct current separation device 3 mainly includes anode and cathode electrodes 6, which are 0.1-0.3 mm thick graphite electrodes. To avoid contamination of the electrodes by moisture fluctuations and soil leachate impurities in the separation device, a 1-2 mm sieve 5 is installed 5 at a distance of 5-15 cm from the anode and cathode electrodes. The extract entering the separation device through the inlet 4 is separated by the anode and cathode electrodes, and cations such as Ca... 2+ Mg 2+ Na + They move towards the cathode, while SO4 2- Cl - Anions move towards the anode, while the intermediate liquid contains a small amount of salt. The solution, rich in cations and anions, is transferred through outlets 8 and 9 to the salt collection device 10. The high-concentration salt solution in the salt collection device 10 is dried into solid salt under the solar thermal panel 11. Water lost during the process is replenished through the water replenishment device 14.

[0032] A solar-powered method for desalinizing saline-alkali soil involves placing a soil salt extraction device 13 on the ground surface, covering it with saline-alkali soil, or inserting it 30-45 cm underground. The extraction device is connected to a water inlet 7, primarily used for leaching salts from the saline-alkali soil (soil-to-water ratio 1:3-6). A water replenishment device 14 is also provided to supplement the water required for extraction. The extract is transferred through an outlet 4 to a soil extract cation-anion direct current electrostatic separation device 3. The voltage is adjusted to 110-360V by a direct current voltage regulator. The anode and cathode electrodes are 0.1-0.3 mm thick graphite electrodes. A 1-2 mm sieve 5 is placed 5-15 cm away from each electrode. The extract entering the separation device through the water inlet 4 is subjected to the action of the anode and cathode electrodes, and cations such as Ca2+ are separated into cations. 2+ Mg 2+ Na + They move towards the cathode, while SO4 2- Cl -Anions move towards the anode, while the intermediate liquid contains a small amount of salt. The solution, rich in cations and anions, is transferred through outlets 8 and 9 to the salt collection device 10, with the flow rate controlled to match the voltage. The high-concentration salt solution in the salt collection device 10 is dried into solid salt under the solar thermal plate 11. Water lost during the process is replenished through the water replenishment device 14.

[0033] Example 1:

[0034] Soil salt extraction device 13 is placed on the ground surface, and 15 kg of saline-alkali soil is placed on top. The extraction device is connected to a water inlet 7, mainly used for rinsing the salt in the saline-alkali soil (soil-to-water ratio 1:3). A water replenishment device 14 is also provided to replenish the water required for extraction (45 L of citric acid aqueous solution is added, with a citric acid mass percentage of 0.3%). The extract is transferred through the water outlet 4 to the soil extract cation-anion direct current separation device 3. The voltage is adjusted to 160 V by the direct current voltage regulator. The anode and cathode electrodes are 0.1 mm thick graphite electrodes. A 1 mm sieve 5 is set 5 cm away from the anode and cathode electrodes. The extract entering the separation device through the water inlet 4 is separated into cations such as Ca2+ under the action of the anode and cathode electrodes. 2+ Mg 2+ Na + They move towards the cathode, while SO4 2- Cl - Anions move towards the anode, while the intermediate liquid contains a small amount of salt. The solution rich in cations and anions (1L for the cathode and 1L for the anode) is transferred through outlets 8 and 9 to the salt collection device 10, with the flow rate controlled to match the voltage. The high-concentration salt solution in the salt collection device 10 is dried into solid salt under solar heating device 11. Water lost during the process is replenished through water replenishment device 14.

[0035] Example 2:

[0036] Soil salt extraction device 13 is placed on the ground surface, and 15 kg of saline-alkali soil is placed on top. The extraction device is connected to a water inlet 7, mainly used for rinsing the salt in the saline-alkali soil (soil-to-water ratio 1:6). A water replenishment device 14 is also provided to replenish the water required for extraction (a total of 90 L of citric acid aqueous solution is added, with a citric acid mass percentage of 0.3%). The extract is transferred through the water outlet 4 to the soil extract cation-anion direct current separation device 3. The voltage is adjusted to 160 V by the direct current voltage regulator. The anode and cathode electrodes are 0.1 mm thick graphite electrodes. A 1 mm sieve 5 is set 5 cm away from the anode and cathode electrodes. The extract entering the separation device through the water inlet 4 is separated into cations such as Ca2+ under the action of the anode and cathode electrodes. 2+ Mg 2+ Na + They move towards the cathode, while SO4 2- Cl- Anions move towards the anode, while the intermediate liquid contains a small amount of salt. The solution rich in cations and anions (2L for the cathode and 2L for the anode) is transferred through outlets 8 and 9 to the salt collection device 10, with the flow rate controlled to match the voltage. The high-concentration salt solution in the salt collection device 10 is dried into solid salt under solar heating device 11. Water lost during the process is replenished through a water replenishment device (14).

[0037] Example 3:

[0038] Soil salt extraction device 13 is placed on the ground surface, and 15 kg of saline-alkali soil is placed on top. The extraction device is connected to a water inlet 7, which is mainly used to rinse the salt in the saline-alkali soil (soil-to-water ratio 1:6). A water replenishment device 14 is also provided to replenish the water required for extraction (90 L of citric acid aqueous solution is added, and the mass percentage of citric acid in the citric acid aqueous solution is 0.3%). The extract is transferred to the soil extract anion-cation direct current separation device 3 through the water outlet 4. The voltage is adjusted to 320 V by the direct current voltage regulator. The anode and cathode electrodes are 0.1 mm thick graphite electrodes. A 1 mm sieve (5) is set at a distance of 5 cm from the anode and cathode electrodes. The extract entering the separation device through the water inlet (4) is separated by the anode and cathode electrodes. Cations such as Ca 2+ Mg 2+ Na + They move towards the cathode, while SO4 2- Cl - Anions move towards the anode, while the intermediate liquid contains a small amount of salt. The solution rich in cations and anions (2L for the cathode and 2L for the anode) is transferred through outlets 8 and 9 to the salt collection device 10, with the flow rate controlled to match the voltage. The high-concentration salt solution in the salt collection device 10 is dried into solid salt under solar heating device 11. Water lost during the process is replenished through water replenishment device 14.

[0039] Example 4:

[0040] Soil salt extraction device 13 is placed on the ground surface, and 15 kg of saline-alkali soil is placed on top. The extraction device is connected to a water inlet 7, mainly used for rinsing the salt in the saline-alkali soil (soil-to-water ratio 1:6). A water replenishment device 14 is also provided to replenish the water required for extraction (a total of 90 L of citric acid aqueous solution is added, with a citric acid mass percentage of 0.3%). The extract is transferred through the water outlet 4 to the soil extract cation-anion direct current separation device 3. The voltage is adjusted to 320 V by the direct current voltage regulator. The anode and cathode electrodes are 0.3 mm thick graphite electrodes. A 1 mm sieve 5 is set 5 cm away from the anode and cathode electrodes. The extract entering the separation device through the water inlet 4 is separated into cations such as Ca2+ under the action of the anode and cathode electrodes. 2+ Mg 2+ Na +They move towards the cathode, while SO4 2- Cl - Anions move towards the anode, while the intermediate liquid contains a small amount of salt. The solution rich in cations and anions (2L for the cathode and 2L for the anode) is transferred through outlets 8 and 9 to the salt collection device 10, with the flow rate controlled to match the voltage. The high-concentration salt solution in the salt collection device 10 is dried into solid salt under solar heating device 11. Water lost during the process is replenished through water replenishment device 14.

[0041] Example 5:

[0042] Soil salt extraction device 13 is inserted 30cm underground. The extraction device is connected to a water inlet 7, mainly used for leaching salts from saline-alkali soil (soil-to-water ratio 1:6). A water replenishment device 14 is also provided to supplement the water required for extraction (a total of 90L of citric acid aqueous solution is added, with a citric acid mass percentage of 0.3%). The extract is transferred through outlet 4 to a soil extract cation-anion direct current electrostatic separation device 3. The voltage is adjusted to 320V by a direct current voltage regulator. The anode and cathode electrodes are 0.3mm thick graphite electrodes. A 1mm sieve 5 is placed 5cm away from each electrode. The extract entering the separation device through inlet 4 is subjected to the action of the anode and cathode electrodes, and cations such as Ca... 2+ Mg 2+ Na + They move towards the cathode, while SO4 2- Cl - Anions move towards the anode, while the intermediate liquid contains a small amount of salt. The solution rich in cations and anions (2L for the cathode and 2L for the anode) is transferred through outlets 8 and 9 to the salt collection device 10, with the flow rate controlled to match the voltage. The high-concentration salt solution in the salt collection device 10 is dried into solid salt under solar heating device 11. Water lost during the process is replenished through water replenishment device 14.

[0043] The results showed that Example 1 could extract 3.25g of soil salt. The tested soil had a salt content of 0.12%, meaning that a single extraction could remove 18.05% of the salt in the saline-alkali soil. Compared to Example 1, Example 2 could extract 4.25g of soil salt, indicating that increasing water input can improve extraction efficiency. Example 3 could extract 4.75g of soil salt, indicating that increasing electrode voltage can improve extraction efficiency, but the voltage needs to be determined in conjunction with local weather and power generation efficiency. Example 4 could extract 4.70g of salt, indicating that there was no significant correlation between graphite electrode thickness and separation efficiency. Example 5 could extract 3.58g of soil salt, indicating that the in-situ extraction method was not as effective as soil transfer. This may be because the soil structure was damaged to some extent during soil transfer, making salt ions easier to leach. Furthermore, the extraction water added during in-situ extraction is easily lost through lateral diffusion, resulting in relatively low extraction efficiency.

Claims

1. A solar-powered method for desalinizing saline-alkali soil, characterized in that, A solar-powered soil desalination device for saline-alkali land includes: Solar power generation device (1); Soil extract anion and cation direct current separation device (3), the soil extract anion and cation direct current separation device (3) includes: a separator; a cathode electrode and an anode electrode disposed on both sides of the separator, the cathode electrode and the anode electrode being connected to the output end of the solar power generation device (1); Soil salt extraction device (13), wherein the soil salt extraction device (13) uses water to extract soil salt in saline-alkali land to obtain soil extract liquid and outputs the soil extract liquid to the middle of the separator through pipeline; The salt collection device (10) is connected to the cathode and anode electrodes inside the separator via a pipeline. The solar power generation device (1) includes: a solar photovoltaic panel and a DC voltage regulator (2) connected to the solar photovoltaic panel. The DC voltage regulator (2) serves as the output terminal of the solar power generation device (1) and is electrically connected to the cathode electrode and the anode electrode. The separator has a cathode electrode blocking screen near the cathode electrode and an anode electrode blocking screen near the anode electrode. The cathode electrode is located between the inner wall of the separator and the barrier screen of the cathode electrode; The anode electrode is located between the inner wall of the separator and the barrier screen of the anode electrode; The soil salinity extraction device (13) includes: Extraction container; A filter screen installed on top of the extraction container for holding saline-alkali soil; Water supply device (14) spraying towards the filter screen; The salt collection device (10) includes: Salt collection container; Solar thermal panel (11) for heating the salt collection container; The method includes the following steps: 1) Cover the saline-alkali soil onto the filter screen of the extraction container, and spray water or citric acid solution onto the saline-alkali soil on the filter screen using the water replenishment device (14). The soil salt extraction device (13) then obtains the soil extract. The citric acid aqueous solution contains 0.1%-0.5% citric acid by mass. 2) The soil extract is transported through pipeline to the middle of the separator of the soil extract anion and cation direct current separation device (3); 3) DC voltage regulating device (2) regulates the voltage to 110-360V. The cathode electrode and anode electrode are both 0.1-0.3mm thick graphite electrodes. Under the action of the cathode and anode electrodes, the cations in the soil extract move towards the cathode, while the anions move towards the anode. The solution rich in cations and anions is transferred to the salt collection device (10). The solution rich in cations and anions in the salt collection device (10) is dried into solid salt under the solar thermal plate (11).

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