Carbon Nanotube Based Porous Membrane Applied For Desalination

The development of desalination technology is crucial for human survival and sustainable development of the ecological environment.Current industrialized desalination technologies,such as Reverse Osmosis(RO),Electrodialysis(ED),Multi-stage Flash Desalination(MSF),etc.have deficiencies in terms of desalination processes,operating costs and energy consumption that cannot be ignored.Solar evaporation is a green and sustainable desalination technology,which can be realized by photothermal conversion of the absorber materials at the air-water interface.In recent years,solar evaporation technology has become the research hotspot with the advantages of low cost,low energy consumption,and high energy conversion efficiency.Carbon-based materials are photo-thermal conversion materials including carbon nanotubes,graphene,carbon black,and graphite,which all have strong light absorption capabilities and excellent photo-thermal conversion properties.Also,carbon nanotube-based materials exhibit good resistance to electrochemical corrosion that gives them the potential to achieve stable Joule-heat air-water interface evaporation.This work focuses on the preparation,characterization and performance optimization of carbon nanotube-based materials for the application of desalination process.We prepared carbon nanotube arrays via chemical vapor deposition(CVD)method and filled the gaps between the carbon nanotube arrays with flexible polymer polydimethylsiloxane(PDMS)to achieve a carbon nanotube-PDMS composite membrane.Porous carbon nanotube composite membrane was constructed by laser etching micropores on the carbon nanotube-PDMS composite membrane.The laser-etched micro-pores and the carbon nanotubes(nano-pores)can continuously refract and reflect the sunlight incident in the composite membrane,limit the sunlight to the interior of the composite membrane so that the composite membrane can achieve a high photo-thermal conversion efficiency.Carbolong complexes were found as a new type of metalorganic complexes with good photo-thermal conversion characteristics.We coated Carbolong complexes on the surface of the porous carbon nanotube-PDMS composite membrane to further enhance photo-thermal conversion property and Joule-heat effect.This work also systematically presents the fabrication of desalination equipment and the control method of desalination processes under optical and electrical conditions respectively.The experimental results show that the salt rejection rate of the photo-thermal conversion and the Joule-heat desalination process can reach 99.90%.The solar evaporation rate of the photo-thermal conversion desalination process is 15.80 kg·m-2·h-1,and the energy utilization efficiency of this process is 93.64%.The evaporation rate of the Joule-heat process is 12.51 kg·m-2·h-1,and the energy utilization efficiency of this process is 46.17%.Therefore,the desalination system in this work might provide a potential way for readily access to freshwater with portable types of equipment in need.