Theoretical Study On Carbon Nitride （C₃N） Nanoslit As Reverse Osmosis Membrane For Efficient Seawater Desalination

The surge in demand for fresh water and the scarcity of water resources are important problems that need to be solved urgently.The earth has a large area of seawater resources,and seawater contains a lot of salt ions and heavy metal ions,which cannot be used directly,so people began to develop seawater desalination technology.Reverse osmosis(RO)is a popular and cost-effective desalination technology.However,the current low salt filtration efficiency of reverse osmosis membranes leads to high energy consumption of the technology,which increases the cost of seawater desalination.Carbon Nitride(C3N),a new two-dimensional nanomaterial with nitrogen atoms,has some outstanding physical and chemical properties.This nanomaterial has almost the same honeycomb structure as graphene,and no research has yet explored its seawater desalination as a reverse osmosis membrane.performance.In this study,a model composed of Graphene(Gr)piston,Carbon Nitride(C3N)nano-slit reverse osmosis membrane,seawater part and freshwater part was constructed.The efficient desalination performance of Carbon Nitride(C3N)nanoslits was proved by molecular dynamics(MD)simulation.The study found that the slit spacing has an important influence on water penetration.When the slit spacing is 6?,the water permeability reaches an ideal value,about 15 L/(cm2·day·MPa),and completely excludes salt.In addition,as the slit spacing increases,so does the water permeability,which is two orders of magnitude higher than that of common commercial membranes,indicating the superiority of C3N nanoslits in seawater desalination.Local analysis of the water inside the channels showed that increasing the slit spacing allowed more water to pass through.Through free energy calculations,we know that the free energy barrier of water molecules passing through nanoslits is much lower than that of Cl-ions and Na+ ions passing through nanoslits,which further explains the efficient penetration of water.All in all,this study confirmed the efficient seawater desalination performance of C3N nanoslits through molecular dynamics simulation,and further analyzed the influencing factors of water permeability.This study is of great significance for solving the problem of global freshwater shortage,and provides theoretical support for the use of novel two-dimensional nanomaterials as RO membranes for seawater desalination.