Our present study used 3,3'-diaminobenzidine (DAB) to prepare nanofiltration polyamide membranes. A poly amide layer was formed on a polysulfone (PSf) support through interfacial polymerization; DAB was reacted with different polyacyl chlorides: isophthaloyl chloride, succinyl chloride, and trimesoyl chloride (TMC). Attenuated total reflectance-Fourier transform infrared confirmed the polyamide layer formation. Scanning electron microscopy illustrated that only the reaction between DAB and TMC yielded a defect-free polyamide layer. The membrane preparation conditions comprised the following parameters: DAB and TMC concentrations, immersion time (PSf support in DAB solution), and polymerization reaction time. The optimized membrane delivered an average permeability of 12.5 L m(-2) h(-1) MPa-1. Its salt rejection followed this order: Na2SO4 (84.2%) > MgSO4 (48.8%) > MgCl2 (14.5%) or NaCl (15.3%). Moreover, the membrane was stable at feed pH of 5-10, at operating temperatures of 25-70 degrees C, and within a long-term nanofiltration period of 148 h.