Insight into the pore tuning of triazine-based nitrogen-rich organoalkoxysilane membranes for use in water desalination

Abstract

A promising new triazine-based nitrogen-rich organosilica (TTESPT) membrane has been developed for molecular separation processes in gas (gas separation) and liquid phases (reverse osmosis (RO)). By adjusting the H₂O/TTESPT molar ratio, we found a promising technique for tuning the pore network of TTESPT membranes. An increase in the H₂O/TTESPT molar ratio from 60 to 240 fully hydrolyzed all the ethoxide groups in the TTESPT membrane, which reduced the size of the pores in the silica pore network. A TTESPT membrane with a high H₂O/TTESPT molar ratio exhibited a high degree of selectivity for H₂/SF₆ (greater than 4000) at a permeation temperature of 200 °C. This membrane also demonstrated high sodium chloride (NaCl) rejection (>98.5%) with water permeability of >1 × 10⁻¹² m³ m⁻² s⁻¹ Pa⁻¹ under operating conditions of 1 MPa and 60 °C during a RO experiment. As the operating temperature was increased from 25 to 60 °C, the NaCl rejection was constant without displaying the characteristic flux deterioration. This showed that the membrane retained a stable hybrid network structure.