(727b) Water Desalination and Purification through Mixed-Matrix Membranes: An Atomistic Simulation Study

Development of technologies for water desalination is critical to cope with the global inadequate supply of clean water. Membrane-based separation is an efficient method to produce fresh water suitable for human consumption and irrigation. In particular, reverse osmosis (RO) has become the most widely used for water desalination. Currently, RO comprises 60% of the capacity of desalination and represents 75-85% new desalination projects worldwide. RO is also significant in purifying polluted water due to its low energy cost and simple operational process, especially in mining areas. In RO process, a selective membrane with high water flux is of vital importance to its performance. Compared with conventional polymeric membranes and zeolites, mixed-matrix membranes (MMMs) formed by incorporating organic/inorganic fillers into a polymer matrix have attracted considerable interest since they combine the merits of each type of material.

In this work, an atomistic simulation study is conducted for water desalination and purification through MMMs constructed by PB-1A organic cage and a polymer of intrinsic microporosity (PIM-1). PB-1A is a newly reported analogue of porphyrin box PB-1 with intrinsic porosity. The swelling of the MMMs in water and its effect on water permeation are examined. For desalination of seawater, the MMMs exhibit high water permeability and 100% salt rejection. For purification of wastewater (containing Pb²⁺, Cu²⁺ and Cd²⁺ ions), high water permeation and ion rejection are also achieved at various conditions. For both applications, the dynamic and structural properties of water molecules in the membranes are investigated. This simulation study provides microscopic insights into water transport in PB-1A/PIM-1 MMMs and suggests their potential use for water desalination and purification.