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Design principle of whole biomass photothermal still based on rice straw
The biomass photothermal distiller made of rice straw has a unique barrier-free water draw channel, has good application universality, and uses waste biomass raw materials, which is more environmentally friendly.
Water is the source of life and one of the necessary conditions for human survival, but the global water resources situation is not optimistic. According to the "World Water Development Report 2018" released by the United Nations, due to factors such as population growth, economic development and changes in consumption patterns, the global demand for water resources is increasing at a rate of 1% per year, and this rate will also increase in the next 20 years. Will be greatly accelerated. "Report" also pointed out that in the next few decades, water quality will further deteriorate, and the threat to human health, environment and sustainable development will only increase.
Recently, a team of Liu Fu, a researcher from the Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, recently developed a full biomass interface photothermal distiller, which is made of rice straw and can extract pure water by solar energy. Related papers published in ACS APPLIED MATERIALS & INTER
FACES.
Using solar energy to achieve energy-free separation and purification
Traditional separation and purification technology is a process of high energy consumption and high cost. Under the current energy crisis and increasing environmental pressure, innovative technologies are urgently needed to break through energy consumption barriers.
Liu Fu told the China Science News in an interview that he started his research on polymer separation membranes with his tutor Professor Xu Youyi during his graduate study at Zhejiang University. After finishing his postdoctoral research work at Imperial College, he returned to China in 2010 to join the Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences. He has been devoted to the research and development and multifunctional application of polymer membrane materials.
I have been studying separation membranes for more than ten years, and he has never got an answer to one question: How to reduce energy consumption during separation and purification?
Liu Fu explained: "Although membrane separation is a relatively low energy consumption technology compared to other separation technologies, this is also one of the reasons why it is widely used. However, energy is becoming increasingly tight, resources are severely scarce, and the ecological environment Today, worsening, further reducing energy consumption and reducing carbon dioxide emissions is a problem that must be solved for the continued development of separation and purification technology. How can we embark on a green road in a rapidly developing economy and society? "
An accidental discovery at an academic conference inspired him. It was a report on light-to-heat conversion materials. As a clean and renewable energy source, solar energy is a topic that scientists around the world are concerned about how to develop and use it efficiently.
Liu Fu is very excited about this: "If solar energy can be integrated into the field of separation and purification, or even membrane separation applications, it will be a low-energy or no-energy carbon dioxide zero-emission technology. Is it possible to achieve low energy? Separation and purification with or without energy consumption? "
The whole biomass photothermal distiller was born
Along this line of thought, the team began to think about whether it could find a light-to-heat conversion material to achieve the purification and purification of water and solve the problem of drinking water for people in water-scarce areas. However, most of the photothermal materials currently studied include plasmon materials (such as gold and silver nanoparticles), carbon nanomaterials (such as graphene, carbon nanotubes, etc.) and semiconductor materials (such as TiO2, Ti3C4, MoO3, etc. ), Most of them have the problems of complicated preparation and high cost, and most of them are difficult to scale.
The last one to become a "seed player" is the most common crop-rice. As a crop with a high transpiration coefficient, the rice straw has a unique capillary cavity and a multi-level micro-nano structure wall.
"This gives rice straw a very excellent bottom-up, unobstructed water supply capacity, which can pump sewage, muddy water, salt water and other pumps up, and the internal channels will not be blocked, maintaining a stable water pumping capacity." The first author of the paper Dr. Fang Qile explained.
They reused rice straw after the grain was harvested. The straw is divided into two, and the upper part of the leaves is simply carbonized to obtain a porous carbon-based light-absorbing material, which is compounded with a cellulose material to form a porous photothermal evaporation film with high stability and high mechanical strength-the evaporation film solar The light absorption reaches 89.4%, and the surface temperature can quickly reach 72 degrees Celsius under the sun; the lower part of the straw is directly used as a water channel and a support. The photothermal evaporation membrane and the water suction channel are assembled into a full biomass interface photothermal distiller, and all of them are prepared from rice straw.
"We placed the photothermal distiller in a transparent closed evaporation chamber for continuous simulation experiments of outdoor seawater desalination. The daily water production in sunny and cloudy weather was 6.4-7.9 kg / m2 and 4.6-5.6 kg / m2, respectively. The ion removal rate is maintained above 99.9%, and the water quality directly meets drinking standards. "Liu Fu said that only one square meter of this photothermal evaporation film can be used to produce fresh water that can fully meet the drinking needs of two or three adults a day.
In addition, in addition to being suitable for seawater desalination, the biomass photothermal distiller can also extract pure water stably from water-bearing media such as tidal flats, wetlands, swamps, etc. It is suitable for emergency water intake in the wild, islands and reefs, and backward water-scarce areas, and can be used on-site Material.
Compared with other biomass photothermal materials, such as wood sliced ​​carbonized materials and mushroom carbonized materials, the biomass photothermal distiller made of rice straw has a unique barrier-free water suction channel, which has good application universality, and The use of waste biomass raw materials is more environmentally friendly.
New green application of photothermal conversion technology
In addition to a relatively simple aqueous solution system, in many cases, the system that requires separation and purification is very complex, often involving high salinity or strong acid and alkaline solutions, polar organic solvents, oil-water mixed systems, etc. Based on actual needs, the research team conducts research on the photothermal conversion materials with high stability and large-scale preparation and purifies the multi-media system.
The carbon fiber, Prussian blue and other light-to-heat conversion materials recently developed by the team have the advantages of high light absorption (92% to 94%), resistance to organic solvents, stable structure, and can be prepared on a large scale. They have been successfully applied to high-saline seawater (10 wt%) ), Oil-water emulsion and a series of organic solvents (dielectric constant 2.38 ~ 37.78) photothermal purification, while maintaining 99.9% removal rate, the evaporation flux from acetone 29.2 Lm-2h-1 to N-methylpyrrolidone The range of 0.73 Lm-2h-1 varies; the purification efficiency of some organic solvents is comparable to that of traditional pressure-driven organic solvent resistant nanofiltration membranes. According to reports, the carbon fiber and Prussian blue thermal material developed by it can also maintain stable mechanical strength in the long-term photothermal operation of highly polar solvents, and have important practical application value.
Liu Fu said that the team is currently continuing to conduct a series of application studies on the separation and purification of photothermal conversion technology in different systems. "The follow-up will also integrate light-to-heat conversion technology in the traditional membrane separation process, using solar energy as a green entry point to explore breakthroughs to further reduce energy consumption." (Reporter Zhang Jingjing)
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