Ultra-high selectivity self-supporting symmetric membrane for forward osmosis separation

The emerging self-supporting symmetric membrane has shown great promise in the field of forward osmosis (FO) separation due to the elimination of internal concentration polarization (ICP). The selective permeability and mechanical properties of membrane materials are the keys to determining the comprehensive properties of such ultra-thin membranes. In this study, a series of carboxylated poly (aryl ether sulfone) (PAES-COOH) materials were designed and synthesized for the fabrication of high performance self-supporting symmetric FO membranes. Owing to the superior character of polymer materials and the introduction of hydrophilic charged carboxylic groups in their molecular structure, these prepared self-supporting symmetric FO membranes with a thickness of ~2.5 μm exhibited excellent mechanical robustness and outstanding permselectivity, so that they could maintain structural integrity and show a high water/salt selectivity in the process of long-term forward osmosis separation. The series of fabricated PAES-COOH membranes displayed the Young's modulus surpass 1.76 GPa, the tensile strength exceed 72.6 MPa, and the elongation at break overtop 70.2%. Additionally, the optimal PAES-COOH-80 membrane sample demonstrated a remarkable H2O/Na2SO4 selectivity of 1673.8 L mol−1. This study provides an effective strategy for conveniently fabricating high-performance self-supporting symmetric FO membrane.