A novel high temperature resistance thin film composite polyamide reverse osmosis membrane with covalent organic frameworks intermediate layer

Abstract

Both salt rejection and pressure-bearing properties of the conventional thin film composite (TFC) polyamide reverse osmosis (RO) membrane are easily weakened at high temperature. In order to improve the high temperature resistance, in this work, a polyamide TFC RO membrane with covalent organic frameworks (COFs) intermediate layer was prepared. Firstly, the COFs layer was decorated on polyether sulfone (PES) support membrane by a unidirectional diffusion method and further modified for shrinking the micropore via the chemical crosslinking reaction with 1,3-diamino-2-propanol (DAPL) or ethylenediamine (EDA), and then continued the conventional interfacial polymerization of m-phenylene diamine (MPD) and trimesoyl chloride (TMC) on the resultant COFs layer for preparing the RO membrane. Furthermore, the correlationship between the microstructure of COFs layer and the separation performance of modified RO membrane was systematically investigated. Due to the introduction of the COF_TpPa-DAPL intermediate layer with more regular microstructure and specific hydrophilicity, the resultant TFC-COF_TpPa-DAPL RO membrane exhibited improvement in water flux by 30 ​% (reached to 50.5 ​L ​m⁻² ​h⁻¹) and higher salt rejection (>99.5 ​%) as compared with the conventional polyamide RO membrane and other reported temperature resistance RO membranes. Meanwhile, this TFC-COF_TpPa-DAPL membrane showed good long-term separation stability during the RO process for 160 ​h. Especially, its water flux increased to 98.8 ​L ​m⁻² ​h⁻¹ without weakening salt rejection (about 99.4 ​%) at 70 ​°C. This study provides an effective way to fabricate the high temperature resistance TFC polyamide RO membrane with good comprehensive separation performance based on COFs intermediate layer.