Development of polymer-based new high performance thin-film nanocomposite nanofiltration membranes by vapor phase interfacial polymerization for the removal of heavy metal ions

The vapor phase interfacial polymerization is the new method for the development of thin-film nanocomposite (TFN) and thin-film composite (TFC) membranes. Generally, interfacial polymerization (IP) is done between aqueous phase monomers and organic phase monomers (containing organic solvent like n-hexane) but in this work, IP was done between aqueous phase monomer with vapour phase of organic monomer (TMC) which is the greener method. First time TFN membranes were prepared by vapour phase interfacial polymerization method. TiO2 nanoparticles act as very good nanofillers to prepare the polymeric nanocomposite membranes to tackle the problem of heavy metal pollution in water. However, their weak interaction with the matrix phase is an issue that causes them to leach out during the filtration process of pressure-driven nanofiltration membrane. Functionalizing the TiO2 nanoparticles with polar functional groups is a solution to this issue. After synthesizing carboxylic acid-functionalized TiO2 (COOH-TiO2) nanoparticles were incorporated in the TFN membranes while IP using DETA and TMC containing amine and acyl group monomers, respectively to modify the membrane surface. The effect of different loading concentrations of COOH-TiO2 nanoparticles in TFN has been studied and compared with the TFC membrane. The prepared membranes are subjected to a cross-filtration system for removing Na+, Cu+2, Hg+2, and Pb+2 from their respective Na2SO4, CuSO4, HgCl2, and Pb(NO3)2 feed solutions. The results of TFN membranes were compared with the TFC membrane. The outcomes have shown 87.03 ± 2% rejection of Na+, 86.89 ± 2% rejection of Cu+2, 77.01 ± 2% rejection of Hg+2 and 83.42 ± 1.5% rejection of Pb+2 ions by using TFN membranes. The effect of the monomeric concentration on the performance of the developed membranes was also studied. The antifouling tendency of the membranes was analysed as well by measuring different antifouling parameters like total fouling (FT), flux recovery ratio (FRR), reversible fouling (FR) and irreversible fouling (FIR). The results obtained are outstanding; incorporating nanomaterial results in lowering the irreversible fouling and enhancing the antifouling tendency.