Photothermal membranes for water treatment and anti-fouling performances: A review

Solar energy is a kind of clean and green energy which has been used in a variety of areas power generation, hot water supply. Recently, solar energy has been used to purify wastewater by combing photothermal materials with variety of membranes. This is because of photothermal materials can absorb sunlight and convert solar energy into thermal energy efficiently. Currently, photothermal membranes for water desalination have gradually become the focus of research. However, the application of photothermal membranes for oily wastewater treatment are not sufficient. This review paper first introduces the light absorption and solar-thermal conversion mechanism of various photothermal materials, which provides theoretical bases for the selection and designing of photothermal materials. Then the latest progress of photothermal materials in desalination, water purification, and oil leakage treatment is reviewed. In addition, some research progress in the pollution control of photothermal materials in water treatment is introduced. Then the challenges which were existed in the photothermal material applications were summarized. Currently, some materials have achieved high photothermal conversion efficiency, due to expensive materials or complex processes, the cost is too high for large-scale practical promotion, resulting in a large gap between the test and practical application. Therefore, the future development of photothermal films needs to reduce the cost and ensure their performance. Besides, most of the experiments are carried out in a simulated environment, such as simulated sunlight. The actual environment is affected by a variety of factors, such as weather changes and many complex conditions existing in the water environment. Whether the photothermal film can also produce the desired effect under natural conditions remains to be tested. In addition, photothermal membranes have great advantages in water treatment, but their impact on the environment and health is rarely mentioned in the literature. Therefore, we need to carry out environmental and health risk assessments of photothermal membranes and minimize the harmful effects of photothermal films on the environment and health. It is believed that with the deepening of research, photothermal materials show attractive potential as green technology for proactively wastewater treatment in the near future.