A review on the synthesis of fully aromatic polyamide reverse osmosis membranes

Reverse osmosis (RO) membranes have been used for desalination for over 40 years. This review focuses on the lab-scale synthesis of fully aromatic polyamide layers used to create RO membranes using the interfacial polymerization (IP) process between an amine monomer, m-phenylenediamine (MPD), and an acyl chloride monomer, trimesoyl chloride (TMC). This review extensively covers the numerous lab-scale synthesis protocols used in research labs and proposed mechanisms and kinetics for synthesizing these fully aromatic polyamide layers using IP. Emphasis is placed on the support membrane used and the reaction conditions such as monomer concentration, solution volume, aqueous solution soaking time, reaction time, reaction temperature, and the use of non-reactive additives in the reaction solution. The effect of processing techniques for removing the aqueous solution and for post-reaction cross-linking are discussed. These variables are compared by investigating their effect on the membrane desalination performance. The numerous methods used to characterize the polyamide layers are reviewed. The synthesis of fully aromatic polyamide layers on hollow fiber membranes is briefly discussed. The goal of this review is to discuss the numerous synthesis parameters in reported lab-scale studies for control membranes, which may help researchers to synthesize and improve RO membranes more effectively.