Polysulfone electro-spun nano-fibrous membranes (PSU ENMs) were prepared using a mixture of solvents N,N-dimethyl formamide (DMF) and tetrahydrofurane (THF) for microfiltration and ultrafiltration. The involved electro-spinning parameters, namely, the polymer solution flow rate, the electric voltage and the distance between the needle tip and the collector were varied in the range within which it was possible to obtain bead-free PSU ENMs. Their effects on the morphology and structure of the PSU ENMs were studied. Interfacial polymerization technique was applied to develop novel thin-film composite polyester-PSU based ENMs. The prepared membranes were characterized by means of different techniques such as scanning electron microscopy, contact angle measurements, X-ray diffraction, attenuated total reflectance Fourier transform spectroscopy. Micro/ultra-filtration tests were conducted using humic acid model solutions with a concentration of 15 mg/L at two different pH values (3 and 11). It was observed that PSU ENMs were not selective under acidic conditions, whereas the thin-film composite polyester-PSU based ENMs achieved better separation factors and lower irreversible fouling factors than those of the un-modified PSU ENMs. (C) 2014 Elsevier B.V. All rights reserved.