Water is the source of life and the basis for the survival of all things in the world. Although water coverage exceeds 70% of the earth we live on, freshwater resources are less than 3%. The distribution of this fresh water is extremely uneven. It exists in lakes, rivers, underground, and Antarctic ice. Less than 1% of the fresh water available for human consumption remains.
In addition, affected by a series of problems such as environmental pollution and population growth, the global shortage of freshwater resources will become more severe in the future. Therefore, solving the problem of scarcity of fresh water resources is a top priority.
On September 13, 2023, Chinese scientists published an article on new photothermal conversion materials in the magazine "Nature". The advent of this material is expected to bring a steady stream of fresh water resources to mankind and ensure a safe and sufficient supply of fresh water!
Image source: Nature magazine.
Preparation and principles of new materials
Solar energy is a renewable energy source that is widely used for heating and energy storage.Solar-driven interfacial water evaporation technology has been proposed for nearly ten years. That is, solar energy is absorbed and converted into heat energy, which promotes the evaporation of water molecules into water vapor. The water vapor is collected and used for subsequent processing. This technology has broad application prospects in the field of seawater desalination to produce clean fresh water. The use of solar energy can alleviate the consumption of fossil energy and a series of environmental pollution problems.
The core of this technology is how to improve the conversion efficiency of solar thermal energy. The new high-efficiency photothermal conversion material newly developed by Chinese scientists brings hope for the widespread use of this technology!
Starting from the nature of heat generation caused by the interaction between sunlight and matter, scientists used chemistry, physics, calculations and other related experiments to discover that there is a Ti-Ti dimer structure in titanium suboxide (TinO2n-1). This structure will limit the distribution range of the 3d layer electron movement of the electronic structure outside the Ti atom nucleus, resulting in real space localization of electrons and the introduction of flat-band electronic states near the Fermi level, resulting in an enhanced joint state density of electronic transitions.
Based on the above principles, it was found through further experiments thatAs a substance of titanium suboxide, λ-Ti3O5 has an absorbance of more than 95% of sunlight.
Reflection spectra and electronic structure. Image source: Reference [1]
The scientists further used λ-Ti3O5 and polyvinyl alcohol materials to process evaporators. In order to improve the efficiency of water evaporation, the evaporator was designed into a three-dimensional porous connected structure.
Experiments have found that under the conditions of sunlight (1kWm-2), through this device, the amount of water evaporated per hour can be as high as 6.09kgm-2, which is the fastest level of water evaporation currently achieved by solar-driven interface water evaporation technology. Scientists further used this equipment in seawater desalination experiments, and the amount of fresh water collected per day can reach 23Lm-2.
It can be seen that if this equipment is put into the field of seawater desalination, large-scale fresh water preparation can be achieved, which will greatly solve the problem of shortage of fresh water resources and bring new ideas to the purification treatment of sewage and wastewater.
Schematic diagram of the working of a three-dimensional porous connected structure evaporator (a. Outdoor seawater desalination device; b. Changes in solar energy, fresh water collection rate, and total amount of collected fresh water over time; c. Changes in temperature and humidity over time; d. Daily average light flux and fresh water collection rate). Image source: Reference [1]
What can we do about freshwater protection?
The discovery of new materials makes us no longer fear that there will be no water to drink in the future. However, we must also save water and increase our awareness of protecting freshwater resources.
First of all, the government has successively promulgated and improved laws and regulations related to the protection of freshwater resources, restricting them through laws, and reminding everyone of the importance of protecting freshwater.Increase the publicity of policies related to freshwater protection and raise everyone's awareness of water conservation. At the same time, optimize the use of fresh water in agriculture and industry and improve the utilization rate of fresh water.
In life, each of us should pay attention to saving water, and at the same time,Be careful not to discard waste, chemicals, medicines, etc. into the sewers, which may easily cause fresh water pollution.
Let us work together to protect freshwater resources, use water rationally, and don't let the last drop of water on the earth become our tears!
References
[1] Yang, B., Zhang, Z., Liu, P. etal. Flatbandλ-Ti3O5 towards extraordinary solar team generation. Nature (2023).
[2] Li Xueqin. New solar collector and its application in seawater desalination [J]. General Machinery, 2012. DOI: CNKI: SUN: TYJS.0.2012-03-037.
[3] Xie Lixin, Li Pingli, Wang Shichang. Current status of seawater desalination technology and review of various desalination methods [J]. Progress in Chemical Industry, 2003, 22(10): 4. DOI: 10.3321/j.issn: 1000-6613.2003.10.011.
[4] Lu Zhu. Prospects of water conservation and water resources regeneration and reuse technology [J]. Water Purification Technology, 2002(S1):5.DOI:CNKI:SUN:ZSJS.0.2002-S1-013.