Synthesis of novel silica-polyamide nanocomposite membrane with enhanced properties

A synthesis method of polyamide nanocomposite film of about 400–800 nm thickness coated over porous polysulfone support via interfacial polymerization to produce thin film nanocomposite membrane with enhanced properties is described here. Two types of nanocomposite films were prepared by incorporating two types of silica nanoparticles in situ into the polyamide films, one was commercially available LUDOX® HS-40 of which the particle size is about 16 nm and the other has the size of about 3 nm which was synthesised in our laboratory from hydrolysis of tetraethyl orthosilicate (TEOS) in acidic medium. The nanocomposite membranes exhibit superior thermal stability than the pure polyamide membranes; and in both the nanocomposite types, the best membrane performance in terms of separation efficiency and productivity flux was observed in the membrane with a certain amount of silica loading. Higher silica loading into the polymer resulted into a thicker nanocomposite membrane film formation; and at the same time these nanocomposite membranes have relatively large pore sizes as well as higher pore number density, as determined by the analysis of membrane permeation data of aqueous solutions of organic solutes and sodium chloride at pressures ranging from 50 to 400 psig. Depending on the silica content, the average pore radii membranes vary from smaller radius of 0.34 nm to fairly a larger radius of 0.73 nm.