CN119191429B - A method for preparing a double-layer polypyrrole deposited nickel foam sodium alginate hydrogel solar evaporator - Google Patents
A method for preparing a double-layer polypyrrole deposited nickel foam sodium alginate hydrogel solar evaporatorInfo
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- CN119191429B CN119191429B CN202411559183.0A CN202411559183A CN119191429B CN 119191429 B CN119191429 B CN 119191429B CN 202411559183 A CN202411559183 A CN 202411559183A CN 119191429 B CN119191429 B CN 119191429B
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/02—Treatment of water, waste water, or sewage by heating
- C02F1/04—Treatment of water, waste water, or sewage by heating by distillation or evaporation
- C02F1/14—Treatment of water, waste water, or sewage by heating by distillation or evaporation using solar energy
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A20/00—Water conservation; Efficient water supply; Efficient water use
- Y02A20/20—Controlling water pollution; Waste water treatment
- Y02A20/208—Off-grid powered water treatment
- Y02A20/212—Solar-powered wastewater sewage treatment, e.g. spray evaporation
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Abstract
一种双层聚吡咯沉积泡沫镍海藻酸钠水凝胶太阳能蒸发器的制备方法，它属于太阳能蒸发器制备领域。本发明要解决现有太阳能界面蒸发器的蒸发表面盐积累会降低蒸发器蒸发速率，影响蒸发器长期稳定性的问题。方法：一、电沉积聚吡咯的泡沫镍吸光层的制备；二、海藻酸钠水凝胶的制备；三、组合吸水层和吸光层制备太阳能海水蒸发系统。本发明用于双层聚吡咯沉积泡沫镍海藻酸钠水凝胶太阳能蒸发器的制备。
A method for preparing a double-layer polypyrrole-deposited nickel foam sodium alginate hydrogel solar evaporator belongs to the field of solar evaporator fabrication. This invention addresses the problem that salt accumulation on the evaporation surface of existing solar interface evaporators reduces the evaporation rate and affects the long-term stability of the evaporator. The method includes: 1. Preparation of a light-absorbing layer of polypyrrole-deposited nickel foam; 2. Preparation of sodium alginate hydrogel; 3. Preparation of a solar seawater evaporation system by combining the water-absorbing layer and the light-absorbing layer. This invention is used for the preparation of a double-layer polypyrrole-deposited nickel foam sodium alginate hydrogel solar evaporator.
Description
Technical Field
The invention belongs to the field of solar evaporator preparation.
Background
With the exhaustion of fresh water resources, people are urgently searching for new technology for obtaining fresh water resources, and sea water desalination is one of the most promising technologies at present. The traditional sea water desalting technology has the reverse osmosis method, the multistage flash evaporation method, the electrodialysis method and the like, but has the defects of difficult equipment and process, high energy consumption, environmental pollution and the like. In recent years, solar photo-thermal driving interface evaporation technology is a focus of attention, and combines photo-thermal technology with a water delivery structure, so that heat energy is concentrated on an evaporation surface, loss is reduced, evaporation efficiency is improved, and the solar photo-thermal driving interface evaporation device has the advantages of sustainability, high energy efficiency and the like.
The high-performance solar-driven interface evaporator water treatment system needs to select proper water absorbing materials and is reasonable in design, water is conveyed to the solar absorber through capillary force to form a thin water layer, and the photo-thermal assembly needs to absorb enough light energy and convert the enough light energy into heat energy to evaporate the thin water layer. However, the accumulation of salt on the evaporation surface of the existing solar interface evaporator can reduce the evaporation rate of the evaporator and affect the long-term stability of the evaporator.
Disclosure of Invention
The invention aims to solve the problems that the evaporation rate of an evaporator is reduced and the long-term stability of the evaporator is affected due to the accumulation of salt on the evaporation surface of the existing solar interface evaporator, and further provides a preparation method of the double-layer polypyrrole deposited foam nickel sodium alginate hydrogel solar evaporator.
The preparation method of the double-layer polypyrrole deposited foam nickel sodium alginate hydrogel solar evaporator comprises the following steps:
1. preparation of a foam nickel light-absorbing layer of electrodeposited polypyrrole:
① Washing and drying the foam nickel to obtain pretreated foam nickel;
② Mixing pyrrole, acetonitrile and tetrabutylammonium tetrafluoroborate to obtain a mixed solution of pyrrole, acetonitrile and tetrabutylammonium tetrafluoroborate;
③ Taking the pretreated foam nickel as a working electrode, a copper sheet as a counter electrode, silver chloride as a reference electrode, and a mixed solution of pyrrole, acetonitrile and tetrabutylammonium tetrafluoroborate as an electrodeposit liquid, adopting a time-current method for an electrochemical workstation, electrodepositing 1000 s-2000 s under the conditions of 1V-4V voltage and 20-50 ℃ temperature, washing and drying after deposition to obtain the foam nickel light absorption layer of electrodeposited polypyrrole;
2. Preparation of sodium alginate hydrogel:
① Adding sodium alginate into distilled water to obtain sodium alginate solution;
② Adding calcium chloride into distilled water to obtain a calcium chloride solution;
③ Adding a calcium chloride solution into a sodium alginate solution, heating and dissolving to obtain sodium alginate hydrogel;
3. Solar seawater evaporation system is prepared by combining a water absorption layer and a light absorption layer:
Placing a foam nickel light absorption layer of electrodeposited polypyrrole at the bottom of a container, pouring sodium alginate hydrogel into the container from the surface of the foam nickel light absorption layer of electrodeposited polypyrrole, forming a hydrogel layer on the upper surface of the foam nickel light absorption layer of electrodeposited polypyrrole, then standing for the first time at room temperature until bubbles in the hydrogel layer are discharged, adding a calcium chloride solution into the hydrogel layer along the inner wall of the container, standing for the second time at room temperature, taking out a sample, soaking with distilled water, and finally removing redundant hydrogel to obtain the double-layer polypyrrole-deposited foam nickel sodium alginate hydrogel solar evaporator;
The double-layer polypyrrole deposited foam nickel sodium alginate hydrogel solar evaporator is of an upper-lower structure, foam nickel of electrodeposited polypyrrole is used as a light absorption layer, and sodium alginate hydrogel is used as a water absorption layer.
The beneficial effects of the invention are as follows:
According to the method for preparing the double-layer polypyrrole deposited foam nickel sodium alginate hydrogel solar evaporator, the polypyrrole deposited thickness in the light absorption layer, the sodium alginate content, the calcium chloride content and the like in the light absorption layer are calculated, the optimal evaporation rate of the prepared double-layer evaporator on seawater is 3.22 Kg.m -2·h-1, the photo-thermal efficiency is 91.8%, and the double-layer structure is proved to have higher evaporation rate and photo-thermal conversion efficiency.
When the double-layer structure is prepared, the foam nickel light absorption layer of the electrodeposited polypyrrole is immersed in the hydrogel, so that hydrogel layers formed on the side surfaces and the bottom surfaces of the foam nickel are required to be removed, the double-layer polypyrrole-deposited foam nickel sodium alginate hydrogel solar evaporator is of an upper-lower structure, the foam nickel of the electrodeposited polypyrrole is the light absorption layer, the sodium alginate hydrogel is the water absorption layer, the thicknesses of the hydrogel layers formed on the surfaces of the double-layer polypyrrole-deposited foam nickel sodium alginate hydrogel solar evaporator are different, and the evaporation rates of the evaporator are different to a certain extent.
The calcium chloride is added in two times when the sodium alginate hydrogel in the evaporator is prepared. The preparation method comprises the steps of adding sodium alginate in the heating and dissolving process for the first time, uniformly distributing the sodium alginate in the sodium alginate hydrogel through heating and stirring, adding the sodium alginate hydrogel after standing for the second time, and soaking the sodium alginate hydrogel in a calcium chloride solution to crosslink calcium ions and gel. The gradual penetration of calcium ions into the whole sodium alginate gel is facilitated by adding calcium chloride in multiple times, if a large amount of calcium ions are added at one time, the local calcium ion concentration is too high, the crosslinking reaction is rapidly carried out at part of the positions, and the sodium alginate at other positions may not be crosslinked sufficiently due to insufficient diffusion of the calcium ions. The calcium chloride is added twice to carry out gradual crosslinking, which is favorable for forming a more uniform three-dimensional network structure, and can avoid over-soft or over-hard areas, thereby improving the strength and toughness of the hydrogel as a whole.
The upper layer of the double-layer polypyrrole-deposited foam nickel sodium alginate hydrogel solar evaporator is a foam nickel light absorption layer, the lower layer of the double-layer polypyrrole-deposited foam nickel sodium alginate hydrogel solar evaporator is a sodium alginate hydrogel water absorption layer, polypyrrole contains a large number of double bonds, so that solar energy can be effectively absorbed and converted into heat energy for water evaporation, sodium alginate has a large number of hydroxyl groups and carboxyl groups, the hydrophilic capacity is improved, and the moisture transportation of micron-sized pore channels is accelerated, so that the wettability of the evaporation surface is ensured.
The method is simple to operate, can be used for large-scale production, and the prepared double-layer polypyrrole deposited on the foam nickel sodium alginate hydrogel solar evaporator has the advantages of low energy consumption, high strength and convenience in use.
Drawings
FIG. 1 is a spectrum of RTIR, 1 is sodium alginate hydrogel, 2 is polypyrrole prepared in step one of example;
FIG. 2 shows the UV-visible-near infrared spectrum and AM1.5G spectrum solar radiation spectrum of a double-layer polypyrrole deposited foam nickel sodium alginate hydrogel solar evaporator and a sodium alginate hydrogel prepared in the first embodiment;
FIG. 3 is an SEM image of a nickel foam and a nickel foam light absorbing layer of electrodeposited polypyrrole, a being the nickel foam described in example one step one ①, b being the nickel foam light absorbing layer of electrodeposited polypyrrole prepared in example one step one ③;
FIG. 4 is an SEM image of a sodium alginate hydrogel;
FIG. 5 is a graph showing contact angle measurements of sodium alginate hydrogels;
FIG. 6 is a graph showing the surface temperature test of the light absorption layer of a double-layer polypyrrole electrodeposited foam nickel sodium alginate hydrogel solar evaporator prepared in example I under the light intensity of 1kw/m 2;
FIG. 7 is a graph showing the relationship between the evaporation rate, the photo-thermal efficiency and the concentration of calcium chloride in the sodium alginate hydrogel of step two ③ of the double-layer polypyrrole-deposited foam nickel sodium alginate hydrogel prepared in examples one to five under the conditions of a solar intensity of 1kw/m 2 and room temperature;
FIG. 8 is a graph showing the relationship between the evaporation rate, the photo-thermal efficiency and the thickness of the hydrogel of the double-layer polypyrrole deposited foam nickel sodium alginate hydrogel prepared in the third, sixth and ninth embodiments under the conditions that the solar intensity is 1kw/m 2 and the room temperature;
FIG. 9 is a graph showing the evaporation rate of a double-layer polypyrrole-deposited foam nickel sodium alginate hydrogel solar evaporator prepared in the first example in NaCl solution with different concentrations for 8 hours under the conditions of solar intensity of 1kw/m 2 and room temperature;
FIG. 10 is a graph showing the change of evaporation rate of a double-layer polypyrrole electrodeposited foam nickel sodium alginate hydrogel solar evaporator prepared in example I in 25% NaCl solution for 7 days under the conditions of solar intensity of 1kw/m 2 and room temperature;
FIG. 11 is a graph showing the comparison of pH test paper before and after evaporation of 1mol/LHCL and 1mol/LNaOH solutions by using a double-layer polypyrrole-deposited foam nickel sodium alginate hydrogel solar evaporator prepared in example I under conditions of solar intensity of 1kw/m 2 and room temperature;
fig. 12 is a schematic view of a solar evaporator of a double-layer polypyrrole-deposited foam nickel sodium alginate hydrogel prepared in example one.
Detailed Description
The preparation method of the double-layer polypyrrole deposited foam nickel sodium alginate hydrogel solar evaporator comprises the following steps of:
1. preparation of a foam nickel light-absorbing layer of electrodeposited polypyrrole:
① Washing and drying the foam nickel to obtain pretreated foam nickel;
② Mixing pyrrole, acetonitrile and tetrabutylammonium tetrafluoroborate to obtain a mixed solution of pyrrole, acetonitrile and tetrabutylammonium tetrafluoroborate;
③ Taking the pretreated foam nickel as a working electrode, a copper sheet as a counter electrode, silver chloride as a reference electrode, and a mixed solution of pyrrole, acetonitrile and tetrabutylammonium tetrafluoroborate as an electrodeposit liquid, adopting a time-current method for an electrochemical workstation, electrodepositing 1000 s-2000 s under the conditions of 1V-4V voltage and 20-50 ℃ temperature, washing and drying after deposition to obtain the foam nickel light absorption layer of electrodeposited polypyrrole;
2. Preparation of sodium alginate hydrogel:
① Adding sodium alginate into distilled water to obtain sodium alginate solution;
② Adding calcium chloride into distilled water to obtain a calcium chloride solution;
③ Adding a calcium chloride solution into a sodium alginate solution, heating and dissolving to obtain sodium alginate hydrogel;
3. Solar seawater evaporation system is prepared by combining a water absorption layer and a light absorption layer:
Placing a foam nickel light absorption layer of electrodeposited polypyrrole at the bottom of a container, pouring sodium alginate hydrogel into the container from the surface of the foam nickel light absorption layer of electrodeposited polypyrrole, forming a hydrogel layer on the upper surface of the foam nickel light absorption layer of electrodeposited polypyrrole, then standing for the first time at room temperature until bubbles in the hydrogel layer are discharged, adding a calcium chloride solution into the hydrogel layer along the inner wall of the container, standing for the second time at room temperature, taking out a sample, soaking with distilled water, and finally removing redundant hydrogel to obtain the double-layer polypyrrole-deposited foam nickel sodium alginate hydrogel solar evaporator;
The double-layer polypyrrole deposited foam nickel sodium alginate hydrogel solar evaporator is of an upper-lower structure, foam nickel of electrodeposited polypyrrole is used as a light absorption layer, and sodium alginate hydrogel is used as a water absorption layer.
The polypyrrole prepared in the step one of the present embodiment is a conjugated conductive polymer and has good light absorption performance. The broadband light absorption characteristic of the material can effectively absorb the spectrum range from ultraviolet to near infrared, the light-heat conversion efficiency of the material can be obviously improved by depositing the material on foam nickel, the thickness and the deposition speed of polypyrrole can be accurately controlled by an electrodeposition technology, and the light absorption efficiency and the thermal conductivity of the material can be adjusted. This controllability enables the performance of the polypyrrole foam nickel material to be optimized according to the application requirements.
In the second step of the specific embodiment, the sodium alginate has stronger ionic crosslinking capability and good mechanical strength, and the sodium alginate can quickly form a stable gel structure through crosslinking with divalent Ca 2+, so that the formed gel has better mechanical stability and durability in environmental change. Compared with other natural or synthetic hydrogels, the sodium alginate hydrogel has better salt deposition resistance in a high-salt environment, so that the sodium alginate hydrogel is more suitable for seawater evaporation and purification application. The sodium alginate is a natural polymer substance which is environment-friendly and biocompatible, is derived from seaweed and has good biocompatibility and degradability. When the water purifying system is used in a seawater purifying system, the water purifying system is harmless to the environment, is easy to degrade or recycle in the post-treatment process, and meets the environmental protection requirement.
In the third step of this embodiment, water molecules in the hydrogel network can be classified into three types, water molecules adjacent to the polymer chain are called bound water through hydrogen bond connection, intermediate water having weak hydrogen bond action with the polymer chain, and free water not constrained by the polymer chain, and the evaporation enthalpy value of the intermediate water has lower evaporation enthalpy than that of the bound water and the free water, so that the evaporation enthalpy of the water in the hydrogel material is lower than that of pure water.
The beneficial effects of this embodiment are:
According to the method for preparing the double-layer polypyrrole deposited foam nickel sodium alginate hydrogel solar evaporator, the thickness of polypyrrole deposited in the light absorption layer, sodium alginate content, calcium chloride content and the like are calculated, the optimal evaporation rate of the prepared double-layer evaporator on seawater is 3.22 Kg.m -2·h-1, the photo-thermal efficiency is 91.8%, and the double-layer structure is proved to have higher evaporation rate and photo-thermal conversion efficiency.
When the double-layer structure is prepared, the foam nickel light absorption layer of the electrodeposited polypyrrole is immersed in the hydrogel, so that hydrogel layers formed on the side surfaces and the bottom surfaces of the foam nickel are required to be removed, the double-layer polypyrrole-deposited foam nickel sodium alginate hydrogel solar evaporator is of an upper-lower structure, the foam nickel of the electrodeposited polypyrrole is the light absorption layer, the sodium alginate hydrogel is the water absorption layer, the thicknesses of the hydrogel layers formed on the surfaces of the double-layer polypyrrole-deposited foam nickel sodium alginate hydrogel solar evaporator are different, and the evaporation rates of the evaporators are different to a certain extent.
In the preparation of the sodium alginate hydrogel in the evaporator, calcium chloride is added in two steps. The preparation method comprises the steps of adding sodium alginate in the heating and dissolving process for the first time, uniformly distributing the sodium alginate in the sodium alginate hydrogel through heating and stirring, adding the sodium alginate hydrogel after standing for the second time, and soaking the sodium alginate hydrogel in a calcium chloride solution to crosslink calcium ions and gel. The gradual penetration of calcium ions into the whole sodium alginate gel is facilitated by adding calcium chloride in multiple times, if a large amount of calcium ions are added at one time, the local calcium ion concentration is too high, the crosslinking reaction is rapidly carried out at part of the positions, and the sodium alginate at other positions may not be crosslinked sufficiently due to insufficient diffusion of the calcium ions. The calcium chloride is added twice to carry out gradual crosslinking, which is favorable for forming a more uniform three-dimensional network structure, and can avoid over-soft or over-hard areas, thereby improving the strength and toughness of the hydrogel as a whole.
The upper layer of the double-layer polypyrrole-deposited foam nickel sodium alginate hydrogel solar evaporator prepared by the embodiment is a foam nickel light absorption layer, the lower layer of the double-layer polypyrrole-deposited foam nickel sodium alginate hydrogel solar evaporator is a sodium alginate hydrogel water absorption layer, polypyrrole contains a large number of double bonds, so that effective solar energy can be absorbed and converted into heat energy for water evaporation, sodium alginate has a large number of hydroxyl groups and carboxyl groups, the hydrophilia is improved, and the moisture transportation of micron-sized pore channels is accelerated, so that the wettability of the evaporation surface is ensured.
The method is simple to operate and can be used for large-scale production, and the prepared double-layer polypyrrole deposited on the foam nickel sodium alginate hydrogel solar evaporator has the advantages of low energy consumption, high strength and convenience in use.
In the second embodiment, the first embodiment is different from the second embodiment in that the thickness of the foam nickel in the first ① is 1 mm-5 mm, and the porosity is 80% -98%. The other is the same as in the first embodiment.
The third embodiment is different from the first or second embodiment in that the volume ratio of pyrrole to acetonitrile in the first ② is 1 (100-200), and the mass ratio of pyrrole to tetrabutylammonium tetrafluoroborate in the first ② is 1mL (1-3) g. The other is the same as the first or second embodiment.
In a fourth embodiment, the difference between the first embodiment and the third embodiment is that the distance between the working electrode and the counter electrode in the first ③ is 2cm to 3cm. The other embodiments are the same as those of the first to third embodiments.
The fifth embodiment is different from the first to fourth embodiments in that the mass percentage of the sodium alginate solution in the second ① is 2.5% -4.5% and the mass percentage of the calcium chloride solution in the second ② is 0.15% -0.30%. The other embodiments are the same as those of the first to fourth embodiments.
In the sixth embodiment, the difference between the present embodiment and one of the first to fifth embodiments is that the volume ratio of the calcium chloride solution and the sodium alginate solution in the second ③ is 1 (1.5-3). The other embodiments are the same as those of the first to fifth embodiments.
In a seventh embodiment, the difference between the first embodiment and the sixth embodiment is that the heating and dissolving in the second ③ is specifically heating for 45 min-90 min under the condition that the temperature is 80-90 ℃. The other embodiments are the same as those of the first to sixth embodiments.
The eighth embodiment is different from one of the first to seventh embodiments in that the third embodiment is allowed to stand for 0.5 to 1.5 hours at room temperature; and thirdly, standing for 15-24 hours at room temperature for the second time, and soaking for 4-12 hours in distilled water at room temperature. The other is the same as in embodiments one to seven.
The eighth embodiment is different from the first to eighth embodiments in that a hydrogel layer with a thickness of 1 cm-3 cm is formed on the upper surface of the foam nickel light absorption layer of the electrodeposited polypyrrole in the third step, and the mass percentage of the calcium chloride solution in the third step is 0.05% -0.1%. The others are the same as in embodiments one to eight.
The tenth embodiment is different from one of the first to ninth embodiments in that the volume ratio of the calcium chloride solution in the third step to the sodium alginate hydrogel added into the container is 1 (0.5-2). The others are the same as in embodiments one to nine.
The following examples are used to verify the benefits of the present invention:
Embodiment one:
the preparation method of the double-layer polypyrrole deposited foam nickel sodium alginate hydrogel solar evaporator comprises the following steps:
1. preparation of a foam nickel light-absorbing layer of electrodeposited polypyrrole:
① Washing the foam nickel with distilled water and ethanol in sequence, and drying for 10min at the temperature of 70 ℃ to obtain pretreated foam nickel;
the area of the foam nickel is 3 multiplied by 3cm, the thickness is 1.7mm, and the porosity is 95%;
② Mixing 0.5mL of pyrrole, 60mL of acetonitrile and 0.85g of tetrabutylammonium tetrafluoroborate to obtain a mixed solution of pyrrole, acetonitrile and tetrabutylammonium tetrafluoroborate;
③ Taking pretreated foam nickel as a working electrode, taking a copper sheet as a counter electrode, taking silver chloride as a reference electrode, taking a mixed solution of pyrrole, acetonitrile and tetrabutylammonium tetrafluoroborate as an electrodeposit liquid, adopting a time-current method for an electrochemical workstation, electrodepositing for 1000s under the conditions of voltage of 2V and temperature of 25 ℃, washing by using water and ethanol after the deposition, and drying under the condition of temperature of 70 ℃ to obtain a foam nickel light absorption layer of electrodeposited polypyrrole;
The area of the copper sheet is 3 multiplied by 3 cm, the thickness of the copper sheet is 1.7 mm, and the distance between the working electrode and the counter electrode is 2cm;
2. Preparation of sodium alginate hydrogel:
① 1.2g of sodium alginate is added into 40mL of distilled water to obtain sodium alginate solution;
② Adding 0.042 calcium chloride into 20mL of distilled water to obtain a calcium chloride solution;
③ Adding 20mL of calcium chloride solution into 40mL of sodium alginate solution, and heating and dissolving for 1h at the temperature of 85 ℃ to obtain sodium alginate hydrogel, wherein the concentration of calcium chloride in the sodium alginate hydrogel is 0.07w/v%;
3. Solar seawater evaporation system is prepared by combining a water absorption layer and a light absorption layer:
Placing a foam nickel light absorption layer of electrodeposited polypyrrole at the bottom of a container, pouring sodium alginate hydrogel from the surface of the foam nickel light absorption layer of electrodeposited polypyrrole into the container, forming a hydrogel layer with the thickness of 2cm on the upper surface of the foam nickel light absorption layer of electrodeposited polypyrrole, then standing for 1h at room temperature, adding a calcium chloride solution into the hydrogel layer along the inner wall of the container, standing for 16h at room temperature for the second time, taking out a sample, soaking for 6h with distilled water, and finally removing redundant hydrogel to obtain the double-layer polypyrrole-deposited foam nickel sodium alginate hydrogel solar evaporator;
The solar evaporator of the double-layer polypyrrole-deposited foam nickel sodium alginate hydrogel is of an up-down structure, foam nickel of the electrodeposited polypyrrole is a light absorption layer, and the sodium alginate hydrogel is a water absorption layer.
The preparation process in the third step of the embodiment belongs to the steps that foam nickel is immersed in hydrogel, and finally, hydrogel layers formed on the side surfaces and the bottom surfaces of the foam nickel are required to be removed, so that a double-layer polypyrrole-deposited foam nickel sodium alginate hydrogel solar evaporator is of an upper-lower structure, foam nickel of electrodeposited polypyrrole is used as a light absorption layer, and sodium alginate hydrogel is used as a water absorption layer.
The second embodiment is different from the first embodiment in that 0.030 calcium chloride is added into 20mL of distilled water in the second ② to obtain a calcium chloride solution, and the concentration of calcium chloride in the sodium alginate hydrogel in the second ③ is 0.05w/v%. The other is the same as in the first embodiment.
Embodiment III the difference between the embodiment I and the embodiment II is that 0.036 calcium chloride is added into 20mL of distilled water in the step ② to obtain a calcium chloride solution, and the concentration of the calcium chloride in the sodium alginate hydrogel in the step ③ is 0.06w/v%. The other is the same as in the first embodiment.
The fourth embodiment is different from the first embodiment in that 0.048 calcium chloride is added into 20mL of distilled water in the second ② to obtain a calcium chloride solution, and the concentration of calcium chloride in the sodium alginate hydrogel in the second ③ is 0.08w/v%. The other is the same as in the first embodiment.
The fifth embodiment is different from the first embodiment in that 0.054 calcium chloride is added into 20mL of distilled water in the second ② to obtain a calcium chloride solution, and the concentration of calcium chloride in the sodium alginate hydrogel in the second ③ is 0.09w/v%. The other is the same as in the first embodiment.
In the sixth embodiment, the difference from the first embodiment is that the sodium alginate hydrogel is poured into a container from the surface of the foam nickel light-absorbing layer of electrodeposited polypyrrole, and a hydrogel layer with the thickness of 3cm is formed on the upper surface of the foam nickel light-absorbing layer of electrodeposited polypyrrole. The other is the same as in the first embodiment.
In the seventh embodiment, the difference from the first embodiment is that the sodium alginate hydrogel is poured into a container from the surface of the foam nickel light absorption layer of electrodeposited polypyrrole, and a hydrogel layer with the thickness of 2.5cm is formed on the upper surface of the foam nickel light absorption layer of electrodeposited polypyrrole. The other is the same as in the first embodiment.
The eighth embodiment is different from the first embodiment in that the sodium alginate hydrogel is poured into a container from the surface of the foam nickel light-absorbing layer of electrodeposited polypyrrole, and a hydrogel layer with the thickness of 1.5cm is formed on the upper surface of the foam nickel light-absorbing layer of electrodeposited polypyrrole. The other is the same as in the first embodiment.
Embodiment nine the present embodiment differs from the first embodiment in that the sodium alginate hydrogel is poured into a container from the surface of the foamed nickel light-absorbing layer of electrodeposited polypyrrole, and a hydrogel layer with a thickness of 1cm is formed on the upper surface of the foamed nickel light-absorbing layer of electrodeposited polypyrrole. The other is the same as in the first embodiment.
In the third step, the foam nickel light-absorbing layer of the electrodeposited polypyrrole is placed at the bottom of a container and placed into a mold, sodium alginate hydrogel is poured into the container from the surface of the foam nickel light-absorbing layer of the electrodeposited polypyrrole, a hydrogel layer with the thickness of 2cm is formed on the upper surface of the foam nickel light-absorbing layer of the electrodeposited polypyrrole, half of foam nickel is immersed in the hydrogel due to the control of the mold, half of foam nickel is not immersed in the hydrogel, and finally redundant hydrogel is removed. The other is the same as in the first embodiment.
The second comparison experiment is that the sodium alginate hydrogel prepared in the second step is poured into a container, kept stand for 1h at room temperature, then calcium chloride solution is added into the hydrogel layer along the inner wall of the container, kept stand for 16h at room temperature, a sample is taken out and soaked in distilled water for 6h, and then electrodeposited polypyrrole foam nickel prepared in the first step is placed on the surface of the hydrogel with the thickness of 2cm, so that a solar evaporator in which the foam nickel is not immersed in the sodium alginate hydrogel at all is obtained. The other is the same as in the first embodiment.
The sodium alginate hydrogel shown in figures 1,2, 4 and 5 is prepared by pouring the sodium alginate hydrogel prepared in the step one of the embodiment into a container, standing for 1h at room temperature, adding a calcium chloride solution into a hydrogel layer along the inner wall of the container, standing for 16h at room temperature, taking out a sample, and soaking in distilled water for 6h to obtain the sodium alginate hydrogel, wherein the mass percent of the calcium chloride solution is 0.5%, and the volume ratio of the calcium chloride solution to the sodium alginate hydrogel added into the container is 1:1.
The nickel foam part in the nickel foam light-absorbing layer of electrodeposited polypyrrole prepared in the first step of the example is removed, the rest of polypyrrole is subjected to RTIR test, the chart shown in fig. 1 is RTIR, the chart shown in fig. 1 is sodium alginate hydrogel, the chart shown in fig. 2 is polypyrrole prepared in the first step of the example, the stretching vibration at 3429cm -1 is O-H in the spectrum of the sodium alginate hydrogel, the asymmetric and symmetric stretching vibration at 1621 and 1423cm -1 are C=O respectively, which indicates successful solidification of sodium alginate and calcium ions, the stretching of C=C and the stretching of C-N in the pyrrole rings at 1545 and 1461cm -1 are C=C in the spectrum of the sodium alginate hydrogel, the vibration and the deformation of C-H rings at 1042 and 902cm -1 are C-H planes, which indicates successful synthesis of the polypyrrole.
Fig. 2 shows an absorbance test of the solar energy evaporator of the double-layer polypyrrole deposited foam nickel sodium alginate hydrogel prepared in the first embodiment, the ultraviolet-visible-near infrared spectrum and the AM1.5G spectrum solar radiation spectrum of the sodium alginate hydrogel, and the absorbance test in the wavelength range of 300-2500nm, wherein the absorbance of the sodium alginate hydrogel is observed to be lower than 15%, and compared with the absorbance of the evaporator in the wavelength range of 300-2500nm, which is obviously improved by 94% -99% due to the existence of the electrodeposited polypyrrole of the light-absorbing material.
Fig. 3 is an SEM image of nickel foam and electrodeposited polypyrrole foam nickel light absorbing layer, a is nickel foam described in example one step one ①, b is electrodeposited polypyrrole foam nickel light absorbing layer prepared in example one step one ③. From the figure, the original foam nickel shows rich void structures, and large interconnected voids are maintained after the polypyrrole is electrodeposited on the surface.
Fig. 4 is an SEM image of sodium alginate hydrogel, and it can be seen from the figure that sodium alginate hydrogel contains a plurality of micropore channels to supply water for upper layer light absorbing substances.
Fig. 5 is a contact angle test chart of the sodium alginate hydrogel, and the graph shows that 10uL water drops on the surface can be rapidly absorbed within 0.1s, which shows that the sodium alginate hydrogel has strong water absorption, a large number of hydrophilic groups exist in a sodium alginate chain, and water is rapidly transported to an evaporation interface during evaporation.
FIG. 6 is a graph showing the surface temperature of the light absorption layer of a solar evaporator for electrodepositing foam nickel sodium alginate hydrogel with double-layer polypyrrole prepared in example I under the light intensity of 1kw/m 2, and the surface temperature at 0,5,10,20,40,60 minutes is recorded by an infrared camera. The initial surface temperature in the evaporator was observed to be 24 ℃, 42 ℃ was reached in20 minutes of irradiation, and the temperature was stabilized at 42 ℃ in 60 minutes, indicating that the absorbed heat energy was balanced with the consumption of evaporated water, and that the electrodeposited polypyrrole had good light absorption properties.
1. The evaporation rate test is a key parameter for describing the energy efficiency of the evaporator, and is carried out by putting a double-layer polypyrrole deposited foam nickel sodium alginate hydrogel solar evaporator into a beaker, adding water, filling the free water surface with PS foam, testing the illumination intensity to be 1kw/m 2, controlling the temperature to be room temperature, recording the weight change of the water every 5 minutes, and calculating the evaporation rate (R) according to a formula.
Wherein M is the mass change (Kg) of water;
s, evaporator area (area of electrodeposited polypyrrole foam nickel) (m 2);
h, irradiation time (h).
2. Determination of evaporator equivalent enthalpy:
The evaporator is placed on the surface of pure water and then placed in a constant temperature and humidity box to be an experimental group, pure water with the same surface area as the evaporator is used as a control group and placed in the constant temperature and humidity box, the temperature is set to be 22 ℃, the relative humidity is set to be 45%, and the test is carried out under normal atmospheric pressure and dark environment, so that the heat absorbed by the evaporator and the pure water can be ensured to be consistent. After 6h of standing, the equivalent evaporation enthalpy of the evaporator (Delta Hequ, J/g) was calculated according to the formula.
△Hvap×m0=△Hvau×m1
Wherein Delta Hvap is the evaporation enthalpy (2246J/g) of pure water at 25 ℃;
m0, mass change of pure water (g);
m1 change in mass of water in evaporator (g).
3. Photo-thermal efficiency test:
the photo-thermal efficiency is an important index for evaluating the performance of the evaporator, and is calculated according to a formula.
η=R1×(△Hequ)/(q×Copt)
Wherein R 1 is the relative evaporation rate (kgm -2h-1), the evaporation rate (R) minus the dark evaporation rate of water;
Delta Hequ equivalent enthalpy of evaporation (jg -1)
Q: solar density (w/m 2);
Copt: optical concentration of evaporator surface.
The evaporation rate test is carried out by using natural seawater in the figures 7 and 8, wherein the seawater is taken from yellow sea (Shandong Wisea), the evaporation rate test is carried out by using NaCl solution with the mass percentage of 3.5% -25% in the figure 9, the evaporation rate test is carried out by using NaCl solution with the mass percentage of 25% in the figure 10, and the evaporation rate test is carried out by using HCL solution with the mass percentage of 1mol/L or NaOH solution with the mass percentage of 1mol/L in the figure 11;
The comparative nickel foam was immersed at half thickness in the three states of hydrogel (comparative experiment one), not immersed in hydrogel (comparative experiment two) and completely immersed in hydrogel (example one) at solar intensity of 1kw/m 2 and room temperature, and seawater was taken from yellow sea (shandong wishi) at 3.06kg·m -2·h-1、2.83Kg·m-2·h-1 and 3.22kg·m -2·h-1, respectively. It is known that the evaporator prepared by immersing the entire structure of the foam nickel in the hydrogel has the highest evaporation rate.
FIG. 7 is a graph showing the relationship between the evaporation rate, the photo-thermal efficiency and the concentration of calcium chloride in the sodium alginate hydrogel of step two ③ of the double-layer polypyrrole-deposited foam nickel sodium alginate hydrogel prepared in examples one to five under the conditions of a solar intensity of 1kw/m 2 and room temperature. The calcium ions in the calcium chloride are exchanged with the sodium ions in the sodium alginate to form cross-links between the calcium ions and sodium alginate molecules, the cross-links connect the sodium alginate molecules together to form a three-dimensional network structure, the strength of the hydrogel can be enhanced by increasing the consumption of the calcium chloride, but the water delivery effect can be influenced by reducing the pore structure, and the evaporation rate is measured to obtain 0.07wt% CaCl solution which still has a considerable evaporation rate under the good gel effect, wherein the evaporation rate is 3.22 Kg.m -2·h-1, and the photo-thermal efficiency is 91.8%.
FIG. 8 is a graph showing the relationship between the evaporation rate, the photo-thermal efficiency and the thickness of the hydrogel of the double-layer polypyrrole deposited foam nickel sodium alginate hydrogel prepared in the third, sixth and ninth embodiments under the conditions that the solar intensity is 1kw/m 2 and the room temperature. The thickness of the hydrogel in the evaporator influences the water delivery rate, the thicker the thickness is, the larger the acting force is required for water delivery, but the thickness of the hydrogel has a certain heat insulation effect on a photo-thermal interface, the heat loss in an evaporation system is reduced, the thickness of 2cm is measured to be the proper thickness of the sodium alginate hydrogel in the evaporation system, the evaporation rate is 3.22 Kg.m -2·h-1, and the photo-thermal efficiency is 91.8%.
FIG. 9 is a graph showing the evaporation rate of a double-layer polypyrrole-deposited foam nickel sodium alginate hydrogel solar evaporator prepared in example one in NaCl solution with different concentrations for 8 hours under the conditions of solar intensity of 1kw/m 2 and room temperature. As shown in the figure, the water evaporation experiments are carried out for 8 hours under the conditions of different salinity solutions with the mass percentages of 3.5% -25%, and the evaporation rates of the water evaporation experiments in 3.5%, 7%, 10.5% and 15% of saline water are slightly reduced by 3.22Kg·m-2·h-1、3.18Kg·m-2·h-1、3.15Kg·m-2·h-1、3.09Kg·m-2·h-1, in 20% and 25% of saline water respectively, but can reach 2.94 Kg.m -2·h-1 and 2.83 Kg.m -2·h-1, so that the evaporator has good salt tolerance.
FIG. 10 is a graph showing the change of evaporation rate of a double-layer polypyrrole electrodeposited foam nickel sodium alginate hydrogel solar evaporator prepared in example I in 25% NaCl solution for 7 days under the conditions of solar intensity of 1kw/m 2 and room temperature. The evaporator had good stability and reusability in high concentration NaCl solution by evaporation for 8 hours per day.
FIG. 11 is a graph showing the comparison of pH test paper before and after evaporation of 1mol/LHCL and 1mol/LNaOH solutions by using the double-layer polypyrrole-deposited foam nickel sodium alginate hydrogel solar evaporator prepared in the first embodiment under the conditions of solar intensity of 1kw/m 2 and room temperature, wherein the pH value before and after evaporation of the solution is detected by the pH test paper, the pH value after evaporation of 1mol/L HCl solution is about 6.0, the pH value after evaporation of 1mol/LNaOH solution is about 7, and the pH value after evaporation and purification is close to neutral, thus proving that the evaporator has good purification effect on strong acid and strong alkali solutions.
Fig. 12 is a schematic view of a solar evaporator of a double-layer polypyrrole-deposited foam nickel sodium alginate hydrogel prepared in example one.
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