A Novel BiOCl Based Nanocomposite Membrane for Water Desalination

In this study, BiOCl based nanocomposites were used as photocatalytic membranes for a simulated study on water desalination in reverse osmosis membrane systems. Through molecular dynamic simulation, the molecular structure of BiOCl, BiOCl/Ag₂S and BiOCl/Bi₂O₃ heterojunctions were designed and their electronic properties, mechanical properties, and membrane performance for water desalination were evaluated for the first time. The molecular structure was created, and a geometry optimization task was used to optimize it. Material Studio 2019 CASTEP was used for simulation of the electronic and mechanical properties and water desalination was performed by ReaxFF software under pressures between 0 and 250 MPa. The novel BiOCl based nanocomposites showed improved electronic and mechanical properties and, most importantly, improvements in salt rejection and water permeability as compared to well-known materials such as graphene and MoS₂. BiOCl and BiOCl/Ag₂S had a bandgap around two, which is the ideal bandgap for semiconductor photocatalysts. A salt rejection of 98% was achieved under an applied pressure of 10 MPa. Salt rejection was higher for BiOCl/Bi₂O₃, while water permeability was higher for BiOCl/Ag₂S. The monolayer BiOCl was unstable under pressures higher than 50 MPa, but the mechanical stability of BiOCl/Ag₂S increased twofold and increased fourfold for BiOCl/Bi₂O₃, which is even higher than MoS₂. However, between the three nanocomposites, BiOCl/Ag₂S was found to be the most ideal photocatalytic nanocomposite membrane.