rexresearch1
Jiayun WANG, et al.
Hydro-Sponge Air Well
Hydro-Sponge Air Well
https://interestingengineering.com/innovation/hydrosponge-water-from-air-40-less-energy?group=test_b
Sun-powered hydrosponge harvests water from air with 40% less energy
Rupendra Brahambhatt
Dubbed CPPY@LiCl, the hydrosponge is mostly made of eco-friendly ingredients, including chitosan (obtained from shellfish waste), γ-polyglutamic acid (a biopolymer), and polyvinylpyrrolidone.
...Creating the perfect hydrosponge
The hydrosponge is mostly made of eco-friendly ingredients, including chitosan (obtained from shellfish waste), γ-polyglutamic acid (a biopolymer), and polyvinylpyrrolidone. To help the material absorb sunlight and turn that into heat effectively, the researchers also added a compound called polypyrrole.
Next, they employed a mix of physical and chemical-based foaming methods to design the material such that 70% of the hydrosponge is empty space comprising interconnected channels. This porous design allows water vapor to flow through it easily and stick to its surface. To further enhance its performance, the researchers added lithium chloride—a salt that’s naturally good at pulling in moisture from the air.
All these ingredients resulted in the formation of CPPY@LiCl, a hydrosponge capable of trapping and releasing water without using any external power supply.
What sets this material apart is how it stores water. The researchers found that water inside it appears in three forms: tightly attached to the material, loosely attached, and freely moving through the pores. CPPY@LiCl contains a lot of loose and free-moving water, which can be removed with far less energy than materials where water binds tightly.
For instance, the amount of energy needed to evaporate water from CPPY@LiCl is about 40% lower than regular water. Moreover, while conventional water harvesting material typically releases water at 80°C (176°F), water starts flowing out from the hydrosponge at just 50°C (122°F),hich means that the heat from sunlight is enough to make it work.
Testing the water retention capacity
The team conducted experiments under different humidity conditions to check CPPY@LiCl’s water absorption rate. The scientists found that the material could absorb 1.64 grams of water per gram of material at 30% humidity, 2.65 grams at 60%, and 4.21 grams at 80%.
Next, they conducted tests in outdoor settings, during which the material was left overnight, and then water was collected from it during the day. At the end of the test, the material had harvested 6.29 liters of water per square meter. Plus, it maintained 90% of its water-capturing ability even after exposure to strong UV light.
Finally, they checked whether this water was clean and drinkable. The harvested water turned out to be safe for human consumption as per the water safety guidelines set by the World Health Organization (WHO). These results highlight the incredible potential of CPPY@LiCl in solving water scarcity-related challenges in many regions of the world.
The material is mostly biodegradable, gives out a good yield, and only needs sunlight, making it an ideal solution for rural and remote areas where people don’t have access to clean drinking water. However, further research is required to improve its performance and bring down the cost of the hydrosponge.
https://advanced.onlinelibrary.wiley.com/doi/10.1002/adfm.202500679
Biomass-Derived Hydro-Sponge for Ultra-Efficient Atmospheric Water Harvesting
Bowen Lin, Wenjun Ying, Chunfeng Li, Jinzhu Liu, Longkun Zhou, Hua Zhang, Ruzhu Wang, Jiayun Wang
Abstract
Sorption-based atmospheric water harvesting (SAWH) presents a promising solution for the global freshwater shortage. However, the efficiency of current water harvesting systems is significantly limited by high energy consumption, primarily due to the inefficiency of existing sorbents and the lack of in-depth research on material-water interactions inside. Thus, a novel biomass-based hydro-sponge porous material, CPPY is prepared, by using carboxymethyl chitosan, γ-polyglutamic acid, polyvinylpyrrolidone, and photothermal additive polypyrrole. Combined with physical and chemical foaming to create porous channels, the porosity can achieve 70%. CPPY is developed with super water storage properties up to 40 g g−1 while containing a large amount of activated water, which reduces the energy consumption for evaporation by 40% compared to pure water. The CPPY@LiCl prepared using CPPY loaded with LiCl achieved ultra-high-water uptake of 1.64, 2.65, and 4.21 g g−1 at 30%, 60%, and 80% RH, respectively, with fast water vapor release at a desorption temperature of 50 °C. A remarkable water yield of 6.29 L m−2 day−1 utilizing CPPY@LiCl integrated with a batch treatment strategy under natural sunlight is achieved.
Inventor(s): WANG JIAYUN; LUO ZHIPENG; DU SHUAI +
The invention relates to the technical field of hydrogel materials, in particular to a salt hydrogel and a preparation method thereof, and provides a carbon material, deionized water, inorganic salt, acrylamide, cellulose or derivatives thereof, a cross-linking agent, a cross-linking accelerant and an initiator. Step 2, dispersing the carbon material in the deionized water, sequentially adding the inorganic salt, the acrylamide, the cellulose or the derivative thereof, the cross-linking agent and the cross-linking accelerant, and stirring and dissolving to obtain a precursor solution; 3, adding an initiator into the precursor solution to obtain a foaming mixed solution; 4, immediately pouring the foaming mixed solution into a mold, standing for a period of time, and demolding to obtain a hydrogel sample; and step 5, sequentially carrying out drying and thermal reduction on the hydrogel sample, so as to obtain the salty hydrogel. The defects of a common adsorbent for taking water from air are effectively overcome.
Technical Field
The invention relates to the technical field of hydrogel materials, and in particular to a saline hydrogel and a preparation method thereof.
Background Art
With the rapid growth of the global economy and population, human demand for freshwater resources has increased dramatically. However, due to various reasons, fresh water resources are facing serious shortage. Currently, obtaining fresh water through traditional methods can no longer meet human demand for fresh water.
Air water extraction technology came into being and has become a hot research topic. For commercial water extraction needs, how to develop efficient, safe and low-cost adsorbents is the main problem in achieving commercial and efficient water extraction. On the one hand, since the water resources obtained by air water extraction are sustainable, it can reduce dependence on traditional water resources. On the other hand, air water extraction technology can be driven by low-temperature heat sources such as solar energy, without consuming a lot of energy, thus reducing greenhouse gas emissions.
Air water extraction technology includes different methods, such as adsorption, refrigeration condensation and fogging.
The adsorption method is to pass humid air through an adsorbent, which captures water vapor in the humid air and further obtains fresh water through evaporation and condensation.
Common adsorbents on the market currently include silica gel, fiber adsorbents, molecular sieves and salt-containing composite adsorbents, but silica gel is expensive to produce and will deform or melt when exposed to high temperatures; the preparation of molecular sieves requires high temperature and high pressure conditions and because the adsorption process of molecular sieves is limited by their pores, molecules of a certain size may clog the pores, resulting in performance degradation; the adsorption capacity of fiber adsorbents is limited compared to hydrogels, and when the fiber adsorbent reaches saturation, regeneration is relatively difficult.
The above-mentioned adsorbents all have some difficult-to-solve problems, such as small adsorption capacity, difficulty in desorption, complex preparation process, and high cost, which will greatly limit their application and the possibility of commercial water extraction. However, salt-containing composite adsorbents can solve the above problems by introducing hygroscopic inorganic salts and stimulus-responsive components into a specific matrix, and are ideal materials for achieving large-scale commercial air water extraction.
In view of the above problems, it is urgently necessary to provide a hygroscopic salt hydrogel having the following advantages: high moisture absorption rate, large adsorption capacity, stable performance, low desorption driving temperature, stable multi-porous structure and low cost.
Summary of the invention
The purpose of the present invention is to provide a salt hydrogel and a preparation method thereof in view of the deficiencies in the prior art;
To achieve the above object, the technical solution adopted by the present invention is:
The present invention provides a method for preparing a saline hydrogel, characterized in that the steps include:
Step 1, providing carbon material, deionized water, inorganic salt, acrylamide, cellulose or its derivatives, a crosslinking agent, a crosslinking accelerator, and an initiator;
Step 2, dispersing the carbon material in the deionized water, and sequentially adding the inorganic salt, the acrylamide, the cellulose or its derivative, the crosslinking agent, and the crosslinking accelerator to stir and dissolve to obtain a precursor solution;
Step 3, adding an initiator to the precursor solution to obtain a foaming mixed solution;
Step 4: pour the foaming mixed solution into the mold immediately, let it stand for a period of time, and then demould it to obtain a hydrogel sample;
Step 5, drying and thermally reducing the hydrogel sample in sequence to obtain the saline hydrogel;
Wherein, the carbon material is selected from at least one of reduced graphene oxide, carboxylated carbon nanotubes, and carbon black;
Wherein, the cellulose or its derivative is selected from at least one of chitosan, wood cellulose, methyl cellulose, hydroxyethyl cellulose and hydroxypropyl methyl cellulose.
Furthermore, the inorganic salt is selected from at least one of LiCl, MgCl<sub>2</sub>, and CaCl<sub>2</sub>.
Furthermore, the cellulose or its derivative is hydroxypropyl methylcellulose.
Furthermore, the cross-linking agent is N,N-methylenebisacrylamide, the cross-linking accelerator is N,N,N',N'-tetramethylethylenediamine, and the initiator is ammonium persulfate.
Furthermore, in the step 2, the method of dispersing the carbon material in the deionized water is ultrasonic dispersion, and the stirring and dissolving step after adding the inorganic salt, the acrylamide, the cellulose or its derivative, the crosslinking agent, and the crosslinking accelerator includes: low-temperature water bath magnetic stirring, and high-speed stirring; wherein,
The ultrasonic dispersion time of the ultrasonic dispersion is 1min-20min;
The rotation speed of the low-temperature water bath magnetic stirring is 500rpm-600rpm;
The temperature of the low-temperature water bath magnetic stirring is 0°C-10°C;
The stirring time of the low-temperature water bath magnetic stirring is 5 min-10 min.
Furthermore, in the step 2, after the precursor solution is magnetically stirred in a low-temperature water bath, the precursor solution is stirred using a cantilevered powerful electric stirrer; wherein,
The rotation speed of the high-speed stirring is 1700rmp-1900rmp;
The stirring time of the high-speed stirring is 10 min-30 min.
Furthermore, in step 5, the drying method is to use an air drying oven for drying, and the thermal reduction method is to use a vacuum oven for thermal reduction; wherein,
The drying process lasts for 7-9 hours.
The drying treatment temperature is 70°C-100°C;
The heat reduction treatment time is 7h-9h;
The treatment temperature of the thermal reduction is 110-130°C.
Furthermore, in the step 1,
The amount of the carbon material used is 1 mg-40 mg; the amount of the deionized water used is 1 mL-15 mL;
The dosage of the inorganic salt is 1g-10g;
The amount of acrylamide used is 1g-5g;
The amount of cellulose or its derivatives is 0.1g-0.5g;
The amount of the cross-linking agent is 1mg-10mg;
The amount of the cross-linking accelerator is 1 μL-15 μL;
The dosage of the initiator is 1 mg to 15 mg.
A salt hydrogel prepared by the preparation method as described above.
The present invention adopts the above technical solution, and has the following technical effects compared with the prior art:
The present invention uses polyacrylamide and hydroxypropyl methylcellulose as a substrate, embeds a hygroscopic inorganic salt as an adsorbent and dopes a carbon material for photothermal conversion. By adjusting the ratio between the components and selecting a suitable preparation process, it is possible to achieve strong hygroscopic ability, large adsorption capacity, no liquid decomposition phenomenon, strong recyclability, and faster adsorption/desorption kinetics, effectively making up for the shortcomings of commonly used air water extraction adsorbents.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG1 is a schematic diagram of a preparation process of a saline hydrogel preparation method;
FIG2 is a graph showing the adsorption and desorption performance test results of saline hydrogel per unit weight (g/g);
FIG3 is a graph showing the adsorption and desorption performance test results per unit area (g/m<sup>2</sup>) of saline hydrogel;
FIG4 is the moisture absorption isotherm of saline hydrogel under different humidity conditions;
FIG5 is a graph showing the cyclic durability test results of saline hydrogel;
Figure 6 shows the effect of different mass proportions of LiCl in saline hydrogel on the hygroscopic properties.
DETAILED DESCRIPTION
The specific embodiments of the present invention will be described in detail below.
Unless otherwise defined, technical or scientific terms used in the claims and the specification shall have the common meanings understood by persons having ordinary skills in the technical field to which the present invention belongs.
The words "include" or similar words used in the patent application specification and claims of the present invention mean that the items appearing before "include" include the items listed after "include" or their equivalents, and do not exclude other items.
Numerical values mentioned herein include all values increasing by one unit from the lower value to the upper value, provided that any lower value is separated from any higher value by at least two units.
For example, if a component or a physical quantity is from 1 to 100, 10 to 90 is better, and 20 to 80 is the most optimal, it is intended to express that values such as 5 to 95, 14 to 76, 23 to 67, 32 to 58, 41 to 49 are clearly listed in this specification; for values less than 1, 0.0001, 0.001, 0.01 or 0.1 are considered to be more appropriate units.
The foregoing examples are for illustrative purposes only and, in fact, all combinations of numerical values between the lowest value and the highest value enumerated are to be considered to be expressly stated in this specification in a similar manner.
Example 1
This embodiment provides a salt hydrogel and a preparation method thereof. In this embodiment, polyacrylamide PAM and hydroxypropyl methylcellulose are used as a substrate, LiCl is embedded as a hygroscopic inorganic salt and a photothermal conversion component, reduced graphene oxide (rGO) is doped. The components are used in a suitable ratio and preparation process to prepare a salt hydrogel that can be used for commercial efficient water extraction. The preparation method thereof comprises the following steps:
Step 1: Provide reduced graphene oxide, deionized water, inorganic salt, acrylamide, cellulose or its derivatives, N,N-methylenebisacrylamide, N,N,N',N'-tetramethylethylenediamine, and ammonium persulfate.
Wherein, the inorganic salt is LiCl, and the cellulose or its derivative is hydroxypropyl methylcellulose;
Step 2, weigh 35 mg of reduced graphene oxide and ultrasonically disperse it in 10 ml of deionized water, the ultrasonic dispersion time is 10 min, and the reduced graphene oxide dispersion is obtained, then 5 g of anhydrous LiCl is weighed, added to the reduced graphene oxide dispersion, and the water bath magnetic stirrer is stirred at a low speed, wherein the speed of the low-speed stirring is 500 rpm, and then the low-speed stirring is performed until the anhydrous LiCl is completely dissolved to obtain a mixed solution of reduced graphene oxide and anhydrous lithium chloride;
Step 3, weigh 2g of acrylamide powder and add it to the mixed solution, stir at a low speed until it is completely dissolved, and obtain a first mixed solution, weigh 0.25g of hydroxypropyl methylcellulose powder and slowly add it to the first mixed solution, stir at a low speed until it is completely dissolved, and obtain a second mixed solution, weigh 6mg of cross-linking agent N,N-methylenebisacrylamide and add it to the second mixed solution, stir at a low speed until it is completely dissolved, and obtain a third mixed solution, then add 10μL of cross-linking promoter tetramethylethylenediamine, and stir evenly at a low speed to obtain a fourth mixed solution, stir the fourth mixed solution at a low speed for 5min, and then use a cantilevered high-powered electric stirrer to adjust the speed to 1800rmp and stir at a high speed for 20min to obtain a precursor solution.
Step 4: Add 9 mg of initiator ammonium persulfate and evenly drop it into the precursor solution. After stirring for 1 minute, immediately pour the obtained foaming mixed solution into the prepared mold for molding. After standing for a period of time, demold the solution to obtain a hydrogel sample.
Step 5: Place the demoulding hydrogel sample in a forced air drying oven for drying, and transfer the dried hydrogel sample to a vacuum oven for thermal reduction to obtain a saline hydrogel.
In this embodiment, the PHGL hydrogel obtained was tested for its moisture absorption performance, and the test results were as follows: moisture absorption was carried out under the conditions of 25°C and 75% RH for 10 hours, and each gram of dry material could absorb 1.32 g of water vapor in the air; then desorption was carried out under the conditions of 80°C and 7% RH, and the amount of water taken up per gram of dry material was 1.14 g, with a water absorption rate of 86%.
Example 2
This embodiment provides a salt hydrogel and a preparation method thereof. In this embodiment, polyacrylamide and hydroxypropyl methylcellulose are used as a substrate, LiCl is embedded as a hygroscopic inorganic salt, and carboxylated carbon nanotubes as a photothermal conversion component are doped. The components are used in a suitable ratio and preparation process to prepare a salt hydrogel that can be used for commercial efficient water extraction. The preparation method thereof comprises the following steps:
Step 1: provide carboxylated carbon nanotubes, deionized water, inorganic salts, acrylamide, cellulose or its derivatives, N,N-methylenebisacrylamide, N,N,N',N'-tetramethylethylenediamine, and ammonium persulfate.
Wherein, the inorganic salt is LiCl, and the cellulose or its derivative is hydroxypropyl methylcellulose;
Step 2: Weigh 4.5 mg of carboxylated carbon nanotubes and ultrasonically disperse them in 3 ml of deionized water for 10 min to obtain a carboxylated carbon nanotube dispersion. Then weigh 1.51 g of anhydrous LiCl and add it to the carboxylated carbon nanotube dispersion. Stir the mixture with a water bath magnetic stirrer at a low speed of 500 rpm until the anhydrous LiCl is completely dissolved to obtain a mixed solution of carboxylated carbon nanotubes and anhydrous lithium chloride.
Step 3, weigh 2g of acrylamide powder and add it to the mixed solution, stir at a low speed until it is completely dissolved, and obtain a first mixed solution, weigh 0.25g of hydroxypropyl methylcellulose powder and slowly add it to the first mixed solution, stir at a low speed until it is completely dissolved, and obtain a second mixed solution, weigh 6mg of cross-linking agent N,N-methylenebisacrylamide and add it to the second mixed solution, stir at a low speed until it is completely dissolved, and obtain a third mixed solution, then add 10μL of cross-linking promoter tetramethylethylenediamine, and stir evenly at a low speed to obtain a fourth mixed solution, stir the fourth mixed solution at a low speed for 5min, and then use a cantilevered high-powered electric stirrer to adjust the speed to 1800rmp and stir at a high speed for 20min to obtain a precursor solution.
Step 4: Add 9 mg of initiator ammonium persulfate and evenly drop it into the precursor solution. After stirring for 1 minute, immediately pour the obtained foaming mixed solution into the prepared mold for molding. After standing for a period of time, demold the solution to obtain a hydrogel sample.
Step 5: Place the demoulding hydrogel sample in a forced air drying oven for drying, and transfer the dried hydrogel sample to a vacuum oven for thermal reduction to obtain a saline hydrogel.
Example 3
This embodiment provides a salt hydrogel and a preparation method thereof. In this embodiment, polyacrylamide and hydroxypropyl methylcellulose are used as a substrate, LiCl is embedded as a hygroscopic inorganic salt and carbon black, a photothermal conversion component, is doped, and the components are used in a suitable ratio and preparation process to prepare a salt hydrogel that can be used for commercial efficient water extraction. The preparation method thereof comprises the following steps:
Step 1: Provide carbon black, deionized water, inorganic salt, acrylamide, cellulose or its derivatives, N,N-methylenebisacrylamide, N,N,N',N'-tetramethylethylenediamine, and ammonium persulfate.
Wherein, the inorganic salt is LiCl, and the cellulose or its derivative is hydroxypropyl methylcellulose;
Step 2: Weigh 10 mg of carbon black and disperse it in 10 ml of deionized water. The ultrasonic dispersion time is 10 min to obtain a carbon black dispersion. Then weigh 5 g of anhydrous LiCl and add it to the carbon black dispersion. Stir the mixture with a water bath magnetic stirrer at a low speed of 500 rpm until the anhydrous LiCl is completely dissolved to obtain a mixed solution of carbon black and anhydrous LiCl.
Step 3, weigh 2g of acrylamide powder and add it to the mixed solution, stir at a low speed until it is completely dissolved, and obtain a first mixed solution, weigh 0.25g of hydroxypropyl methylcellulose powder and slowly add it to the first mixed solution, stir at a low speed until it is completely dissolved, and obtain a second mixed solution, weigh 6mg of cross-linking agent N,N-methylenebisacrylamide and add it to the second mixed solution, stir at a low speed until it is completely dissolved, and obtain a third mixed solution, then add 10μL of cross-linking promoter tetramethylethylenediamine, and stir evenly at a low speed to obtain a fourth mixed solution, stir the fourth mixed solution at a low speed for 5min, and then use a cantilevered high-powered electric stirrer to adjust the speed to 1800rmp and stir at a high speed for 20min to obtain a precursor solution.
Step 4: Add 9 mg of initiator ammonium persulfate and evenly drop it into the precursor solution. After stirring for 1 minute, immediately pour the obtained foaming mixed solution into the prepared mold for molding. After standing for a period of time, demold the solution to obtain a hydrogel sample.
Step 5: Place the demoulding hydrogel sample in a forced air drying oven for drying, and transfer the dried hydrogel sample to a vacuum oven for thermal reduction to obtain a saline hydrogel.
As a preferred embodiment, cellulose or a derivative thereof is selected from at least one of chitosan, lignocellulose, methyl cellulose, hydroxyethyl cellulose, and carboxymethyl cellulose.
As a preferred embodiment, the inorganic salt is selected from at least one of MgCl<sub>2</sub> and CaCl<sub>2</sub>.
The present invention uses polyacrylamide and hydroxypropyl methylcellulose as a substrate, embeds a hygroscopic inorganic salt as an adsorbent and dopes a carbon material for photothermal conversion. By adjusting the ratio between the components and selecting a suitable preparation process, it is possible to achieve strong hygroscopic ability, large adsorption capacity, no liquid decomposition phenomenon, strong recyclability, and faster adsorption/desorption kinetics, effectively making up for the shortcomings of commonly used air water extraction adsorbents.
The above description is only a preferred embodiment of the present invention, and does not limit the implementation mode and protection scope of the present invention. For those skilled in the art, it should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the description and illustrations of the present invention should be included in the protection scope of the present invention.
A water-harvesting system can operate with a material that can take up and release water with minimum energy requirements and powered by low-grade energy sources, such as sunlight, in order to potentially allow its deployment into households, especially those located in sunny regions. A water-harvesting method and system can include vapor adsorption using a porous metal-organic framework. In certain embodiments, the porous metal-organic framework can include metal-organic framework in ambient air with low relative humidity, typical of the levels found in most dry regions of the world.
Related: Air Wells, Dew Ponds & Fog Fences: http://rexresearch.com/1index.html#airwellsindx