Polyamide thin film composite membranes containing ZIF-8 for the separation of pharmaceutical compounds from aqueous streams

Pharmaceutical compounds which are hydrophilic and biologically persistent are being recognized as new unregulated contaminants in water. The hydrophilic characteristic deters their removal through biological processes and adsorption. However, electrostatic repulsion and size sieving in nanofiltration (NF) can be used for the removal of these compounds. Although both NF and reverse osmosis (RO) are options for removal of pharmaceutical compounds from aqueous feeds, the high pressure (and therefore high energy consumption) and membrane fouling remain serious concerns. Therefore development of improved membranes continues to be a key research area. Metal organic frameworks (MOF) are a class of porous crystalline compounds which offer advantages of large surface area and controlled porosity. MOFs have been used as adsorbents. More recently, MOF membranes and MOF incorporated polymeric membranes have gained importance. In this work, MOF incorporated polymeric membrane was prepared and tested for removal of the common analgesic acetaminophen (or paracetamol, MW 151 g/mol). Thin film polyamide composite membranes were synthesized by interfacial polymerization with zeolitic imidazolate framework-8 (ZIF-8). Two different structures were prepared and characterized (i) polysulfone (PSF) support membranes with ZIF-8 and polyamide (PA) separation layer, and (ii) layer-by layer (LBL) polyamide/ZIF-8 nanocomposite membrane on top of PSF support. The latter synthesis protocol produced defect free TFC membrane with 55% acetaminophen retention and permeance equivalent to conventional PSF/PA membrane.